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<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide</title><author><name sortKey="Kuyken, Bart" sort="Kuyken, Bart" uniqKey="Kuyken B" first="Bart" last="Kuyken">Bart Kuyken</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Ideguchi, Takuro" sort="Ideguchi, Takuro" uniqKey="Ideguchi T" first="Takuro" last="Ideguchi">Takuro Ideguchi</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="Holzner, Simon" sort="Holzner, Simon" uniqKey="Holzner S" first="Simon" last="Holzner">Simon Holzner</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="Yan, Ming" sort="Yan, Ming" uniqKey="Yan M" first="Ming" last="Yan">Ming Yan</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="H Nsch, Theodor W" sort="H Nsch, Theodor W" uniqKey="H Nsch T" first="Theodor W." last="H Nsch">Theodor W. H Nsch</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="Van Campenhout, Joris" sort="Van Campenhout, Joris" uniqKey="Van Campenhout J" first="Joris" last="Van Campenhout">Joris Van Campenhout</name><affiliation><nlm:aff id="a5"><institution>imec</institution>, Kapeldreef 75, 3001 Leuven,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Verheyen, Peter" sort="Verheyen, Peter" uniqKey="Verheyen P" first="Peter" last="Verheyen">Peter Verheyen</name><affiliation><nlm:aff id="a5"><institution>imec</institution>, Kapeldreef 75, 3001 Leuven,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Coen, Stephane" sort="Coen, Stephane" uniqKey="Coen S" first="Stéphane" last="Coen">Stéphane Coen</name><affiliation><nlm:aff id="a6"><institution>Department of Physics, The University of Auckland</institution>, Private Bag 92019 Auckland,<country>New Zealand</country></nlm:aff></affiliation></author><author><name sortKey="Leo, Francois" sort="Leo, Francois" uniqKey="Leo F" first="Francois" last="Leo">Francois Leo</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Baets, Roel" sort="Baets, Roel" uniqKey="Baets R" first="Roel" last="Baets">Roel Baets</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Roelkens, Gunther" sort="Roelkens, Gunther" uniqKey="Roelkens G" first="Gunther" last="Roelkens">Gunther Roelkens</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Picque, Nathalie" sort="Picque, Nathalie" uniqKey="Picque N" first="Nathalie" last="Picqué">Nathalie Picqué</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a7"><institution>Institut des Sciences Moléculaires d’Orsay, CNRS</institution>, Bâtiment 350, 91405 Orsay,<country>France</country></nlm:aff></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">PMC</idno><idno type="pmid">25697764</idno><idno type="pmc">4346629</idno><idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4346629</idno><idno type="RBID">PMC:4346629</idno><idno type="doi">10.1038/ncomms7310</idno><date when="2015">2015</date><idno type="wicri:Area/Pmc/Corpus">000076</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000076</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide</title><author><name sortKey="Kuyken, Bart" sort="Kuyken, Bart" uniqKey="Kuyken B" first="Bart" last="Kuyken">Bart Kuyken</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Ideguchi, Takuro" sort="Ideguchi, Takuro" uniqKey="Ideguchi T" first="Takuro" last="Ideguchi">Takuro Ideguchi</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="Holzner, Simon" sort="Holzner, Simon" uniqKey="Holzner S" first="Simon" last="Holzner">Simon Holzner</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="Yan, Ming" sort="Yan, Ming" uniqKey="Yan M" first="Ming" last="Yan">Ming Yan</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="H Nsch, Theodor W" sort="H Nsch, Theodor W" uniqKey="H Nsch T" first="Theodor W." last="H Nsch">Theodor W. H Nsch</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation></author><author><name sortKey="Van Campenhout, Joris" sort="Van Campenhout, Joris" uniqKey="Van Campenhout J" first="Joris" last="Van Campenhout">Joris Van Campenhout</name><affiliation><nlm:aff id="a5"><institution>imec</institution>, Kapeldreef 75, 3001 Leuven,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Verheyen, Peter" sort="Verheyen, Peter" uniqKey="Verheyen P" first="Peter" last="Verheyen">Peter Verheyen</name><affiliation><nlm:aff id="a5"><institution>imec</institution>, Kapeldreef 75, 3001 Leuven,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Coen, Stephane" sort="Coen, Stephane" uniqKey="Coen S" first="Stéphane" last="Coen">Stéphane Coen</name><affiliation><nlm:aff id="a6"><institution>Department of Physics, The University of Auckland</institution>, Private Bag 92019 Auckland,<country>New Zealand</country></nlm:aff></affiliation></author><author><name sortKey="Leo, Francois" sort="Leo, Francois" uniqKey="Leo F" first="Francois" last="Leo">Francois Leo</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Baets, Roel" sort="Baets, Roel" uniqKey="Baets R" first="Roel" last="Baets">Roel Baets</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Roelkens, Gunther" sort="Roelkens, Gunther" uniqKey="Roelkens G" first="Gunther" last="Roelkens">Gunther Roelkens</name><affiliation><nlm:aff id="a1"><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation><affiliation><nlm:aff id="a2"><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></nlm:aff></affiliation></author><author><name sortKey="Picque, Nathalie" sort="Picque, Nathalie" uniqKey="Picque N" first="Nathalie" last="Picqué">Nathalie Picqué</name><affiliation><nlm:aff id="a3"><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a4"><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></nlm:aff></affiliation><affiliation><nlm:aff id="a7"><institution>Institut des Sciences Moléculaires d’Orsay, CNRS</institution>, Bâtiment 350, 91405 Orsay,<country>France</country></nlm:aff></affiliation></author></analytic><series><title level="j">Nature Communications</title><idno type="eISSN">2041-1723</idno><imprint><date when="2015">2015</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><p>Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500–3,300 nm) spectra with a coupled input pulse energy as low as 16 pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip.</p></div></front><back><div1 type="bibliography"><listBibl><biblStruct><analytic><author><name sortKey="Schliesser, A" uniqKey="Schliesser A">A. Schliesser</name></author><author><name sortKey="Picque, N" uniqKey="Picque N">N. Picqué</name></author><author><name sortKey="H Nsch, T W" uniqKey="H Nsch T">T. W. Hänsch</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Hugi, A" uniqKey="Hugi A">A. Hugi</name></author><author><name sortKey="Villares, G" uniqKey="Villares G">G. Villares</name></author><author><name sortKey="Blaser, S" uniqKey="Blaser S">S. Blaser</name></author><author><name sortKey="Liu, H" uniqKey="Liu H">H. Liu</name></author><author><name sortKey="Faist, J" uniqKey="Faist J">J. Faist</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Wang, C Y" uniqKey="Wang C">C. Y. Wang</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Burghoff, D" uniqKey="Burghoff D">D. Burghoff</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Dudley, J M" uniqKey="Dudley J">J. M. Dudley</name></author><author><name sortKey="Genty, G" uniqKey="Genty G">G. Genty</name></author><author><name sortKey="Coen, S" uniqKey="Coen S">S. Coen</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Marandi, A" uniqKey="Marandi A">A. Marandi</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Rudy, C W" uniqKey="Rudy C">C. W. Rudy</name></author><author><name sortKey="Marandi, A" uniqKey="Marandi A">A. Marandi</name></author><author><name sortKey="Vodopyanov, K L" uniqKey="Vodopyanov K">K. L. Vodopyanov</name></author><author><name sortKey="Byer, R L" uniqKey="Byer R">R. L. Byer</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Lee, K" uniqKey="Lee K">K. Lee</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Granzow, N" uniqKey="Granzow N">N. Granzow</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Shabahang, S" uniqKey="Shabahang S">S. Shabahang</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Phillips, C R" uniqKey="Phillips C">C. R. Phillips</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Phillips, C R" uniqKey="Phillips C">C. R. Phillips</name></author><author><name sortKey="Pelc, J S" uniqKey="Pelc J">J. S. Pelc</name></author><author><name sortKey="Fejer, M M" uniqKey="Fejer M">M. M. Fejer</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Halir, R" uniqKey="Halir R">R. Halir</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Soref, R" uniqKey="Soref R">R. Soref</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Jalali, B" uniqKey="Jalali B">B. Jalali</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Lau, R" uniqKey="Lau R">R. Lau</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Bogaerts, W" uniqKey="Bogaerts W">W. Bogaerts</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Bristow, A D" uniqKey="Bristow A">A. D. Bristow</name></author><author><name sortKey="Rotenberg, N" uniqKey="Rotenberg N">N. Rotenberg</name></author><author><name sortKey="Van Driel, H M" uniqKey="Van Driel H">H. M. Van Driel</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Kumar, S C" uniqKey="Kumar S">S. C. Kumar</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Pu, M" uniqKey="Pu M">M. Pu</name></author><author><name sortKey="Liu, L" uniqKey="Liu L">L. Liu</name></author><author><name sortKey="Ou, H" uniqKey="Ou H">H. Ou</name></author><author><name sortKey="Yvind, K" uniqKey="Yvind K">K. Yvind</name></author><author><name sortKey="Hvam, J M" uniqKey="Hvam J">J. M. Hvam</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Colinge, J" uniqKey="Colinge J">J. Colinge</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Hochberg, M" uniqKey="Hochberg M">M. Hochberg</name></author><author><name sortKey="Jones, T B" uniqKey="Jones T">T. B. Jones</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Udem, T" uniqKey="Udem T">T. Udem</name></author><author><name sortKey="Holzwarth, R" uniqKey="Holzwarth R">R. Holzwarth</name></author><author><name sortKey="H Nsch, T W" uniqKey="H Nsch T">T. W. Hänsch</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Gohle, C" uniqKey="Gohle C">C. Gohle</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Ideguchi, T" uniqKey="Ideguchi T">T. Ideguchi</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Diddams, S A" uniqKey="Diddams S">S. A. Diddams</name></author><author><name sortKey="Ye, J" uniqKey="Ye J">J. Ye</name></author><author><name sortKey="Hollberg, L" uniqKey="Hollberg L">L. Hollberg</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Pearl, S" uniqKey="Pearl S">S. Pearl</name></author><author><name sortKey="Rotenberg, N" uniqKey="Rotenberg N">N. Rotenberg</name></author><author><name sortKey="Driel, H M" uniqKey="Driel H">H. M. Driel</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Cristiani, I" uniqKey="Cristiani I">I. Cristiani</name></author><author><name sortKey="Tediosi, R" uniqKey="Tediosi R">R. Tediosi</name></author><author><name sortKey="Tartara, L" uniqKey="Tartara L">L. Tartara</name></author><author><name sortKey="Degiorgio, V" uniqKey="Degiorgio V">V. Degiorgio</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Kuyken, B" uniqKey="Kuyken B">B. Kuyken</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Ruehl, A" uniqKey="Ruehl A">A. Ruehl</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Baehr Jones, T" uniqKey="Baehr Jones T">T. Baehr-Jones</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Li, F" uniqKey="Li F">F. Li</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Soref, R" uniqKey="Soref R">R. Soref</name></author><author><name sortKey="Emelett, A" uniqKey="Emelett A">A. Emelett</name></author><author><name sortKey="Buchwald, W R" uniqKey="Buchwald W">W. R. Buchwald</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Griffith, A G" uniqKey="Griffith A">A. G. Griffith</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Yin, L" uniqKey="Yin L">L. Yin</name></author><author><name sortKey="Lin, Q" uniqKey="Lin Q">Q. Lin</name></author><author><name sortKey="Agrawal, G P" uniqKey="Agrawal G">G. P. Agrawal</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Husko, C" uniqKey="Husko C">C. Husko</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Gai, X" uniqKey="Gai X">X. Gai</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Lin, Q" uniqKey="Lin Q">Q. Lin</name></author><author><name sortKey="Painter, O J" uniqKey="Painter O">O. J. Painter</name></author><author><name sortKey="Agrawal, G P" uniqKey="Agrawal G">G. P. Agrawal</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Boyraz, O" uniqKey="Boyraz O">O. Boyraz</name></author><author><name sortKey="Koonath, P" uniqKey="Koonath P">P. Koonath</name></author><author><name sortKey="Raghunathan, V" uniqKey="Raghunathan V">V. Raghunathan</name></author><author><name sortKey="Jalali, B" uniqKey="Jalali B">B. Jalali</name></author></analytic></biblStruct></listBibl></div1></back></TEI><pmc article-type="research-article"><pmc-dir>properties open_access</pmc-dir>
<front><journal-meta><journal-id journal-id-type="nlm-ta">Nat Commun</journal-id><journal-id journal-id-type="iso-abbrev">Nat Commun</journal-id><journal-title-group><journal-title>Nature Communications</journal-title></journal-title-group><issn pub-type="epub">2041-1723</issn><publisher><publisher-name>Nature Pub. Group</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="pmid">25697764</article-id><article-id pub-id-type="pmc">4346629</article-id><article-id pub-id-type="pii">ncomms7310</article-id><article-id pub-id-type="doi">10.1038/ncomms7310</article-id><article-categories><subj-group subj-group-type="heading"><subject>Article</subject></subj-group></article-categories><title-group><article-title>An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide</article-title></title-group><contrib-group><contrib contrib-type="author"><name><surname>Kuyken</surname><given-names>Bart</given-names></name><xref ref-type="corresp" rid="c2">b</xref><xref ref-type="aff" rid="a1">1</xref><xref ref-type="aff" rid="a2">2</xref></contrib><contrib contrib-type="author"><name><surname>Ideguchi</surname><given-names>Takuro</given-names></name><xref ref-type="aff" rid="a3">3</xref></contrib><contrib contrib-type="author"><name><surname>Holzner</surname><given-names>Simon</given-names></name><xref ref-type="aff" rid="a3">3</xref><xref ref-type="aff" rid="a4">4</xref></contrib><contrib contrib-type="author"><name><surname>Yan</surname><given-names>Ming</given-names></name><xref ref-type="aff" rid="a3">3</xref><xref ref-type="aff" rid="a4">4</xref></contrib><contrib contrib-type="author"><name><surname>Hänsch</surname><given-names>Theodor W.</given-names></name><xref ref-type="aff" rid="a3">3</xref><xref ref-type="aff" rid="a4">4</xref></contrib><contrib contrib-type="author"><name><surname>Van Campenhout</surname><given-names>Joris</given-names></name><xref ref-type="aff" rid="a5">5</xref></contrib><contrib contrib-type="author"><name><surname>Verheyen</surname><given-names>Peter</given-names></name><xref ref-type="aff" rid="a5">5</xref></contrib><contrib contrib-type="author"><name><surname>Coen</surname><given-names>Stéphane</given-names></name><xref ref-type="aff" rid="a6">6</xref></contrib><contrib contrib-type="author"><name><surname>Leo</surname><given-names>Francois</given-names></name><xref ref-type="aff" rid="a1">1</xref><xref ref-type="aff" rid="a2">2</xref></contrib><contrib contrib-type="author"><name><surname>Baets</surname><given-names>Roel</given-names></name><xref ref-type="aff" rid="a1">1</xref><xref ref-type="aff" rid="a2">2</xref></contrib><contrib contrib-type="author"><name><surname>Roelkens</surname><given-names>Gunther</given-names></name><xref ref-type="aff" rid="a1">1</xref><xref ref-type="aff" rid="a2">2</xref></contrib><contrib contrib-type="author"><name><surname>Picqué</surname><given-names>Nathalie</given-names></name><xref ref-type="corresp" rid="c1">a</xref><xref ref-type="aff" rid="a3">3</xref><xref ref-type="aff" rid="a4">4</xref><xref ref-type="aff" rid="a7">7</xref></contrib><aff id="a1"><label>1</label><institution>Photonics Research Group, Department of Information Technology, Ghent University–imec</institution>, Sint-Pietersnieuwstraat 41, 9000 Ghent,<country>Belgium</country></aff><aff id="a2"><label>2</label><institution>Center for Nano- and Biophotonics (NB-Photonics), Ghent University</institution>, 9000 Ghent,<country>Belgium</country></aff><aff id="a3"><label>3</label><institution>Max Planck Institut für Quantenoptik</institution>, Hans-Kopfermannstrasse 1, 85748 Garching,<country>Germany</country></aff><aff id="a4"><label>4</label><institution>Ludwig-Maximilians-Universität München, Fakultät für Physik</institution>, Schellingstrasse 4/III, 80799 Munich,<country>Germany</country></aff><aff id="a5"><label>5</label><institution>imec</institution>, Kapeldreef 75, 3001 Leuven,<country>Belgium</country></aff><aff id="a6"><label>6</label><institution>Department of Physics, The University of Auckland</institution>, Private Bag 92019 Auckland,<country>New Zealand</country></aff><aff id="a7"><label>7</label><institution>Institut des Sciences Moléculaires d’Orsay, CNRS</institution>, Bâtiment 350, 91405 Orsay,<country>France</country></aff></contrib-group><author-notes><corresp id="c1"><label>a</label><email>nathalie.picque@mpq.mpg.de</email></corresp><corresp id="c2"><label>b</label><email>Bart.Kuyken@intec.ugent.be</email></corresp></author-notes><pub-date pub-type="epub"><day>20</day><month>02</month><year>2015</year></pub-date><volume>6</volume><elocation-id>6310</elocation-id><history><date date-type="received"><day>06</day><month>09</month><year>2014</year></date><date date-type="accepted"><day>16</day><month>01</month><year>2015</year></date></history><permissions><copyright-statement>Copyright © 2015, Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.</copyright-statement><copyright-year>2015</copyright-year><copyright-holder>Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.</copyright-holder><license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/4.0/"><pmc-comment>author-paid</pmc-comment>
<license-p>This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit <ext-link ext-link-type="uri" xlink:href="http://creativecommons.org/licenses/by/4.0/">http://creativecommons.org/licenses/by/4.0/</ext-link></license-p></license></permissions><abstract><p>Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500–3,300 nm) spectra with a coupled input pulse energy as low as 16 pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip.</p></abstract><abstract abstract-type="web-summary"><p><inline-graphic id="i1" xlink:href="ncomms7310-i1.jpg"></inline-graphic>Phase-coherent frequency combs in the mid-infrared have important potential applications but their fabrication remains challenging. Here, Kuyken <italic>et al</italic>. demonstrate an octave-spanning frequency comb in the mid-infrared using a highly nonlinear dispersion-engineered silicon waveguide on a silicon-on-insulator chip.</p></abstract></article-meta></front><body><p>Frequency combs in the mid-infrared region<xref ref-type="bibr" rid="b1">1</xref> have been mostly generated by nonlinear frequency conversion of near-infrared frequency combs. Although the field is currently very active with the exploration of many different and promising approaches<xref ref-type="bibr" rid="b2">2</xref><xref ref-type="bibr" rid="b3">3</xref><xref ref-type="bibr" rid="b4">4</xref>, producing a very broad spectrum with a slowly varying envelope remains challenging. Supercontinuum generation in a highly nonlinear fibre is known, under certain circumstances<xref ref-type="bibr" rid="b5">5</xref>, to be a powerful way to generate an octave-spanning frequency comb.</p><p>However, in the mid-infrared spectral region, suitable materials have remained scarse and difficult to engineer. Phase-coherent octave-spanning frequency comb generation has been achieved by spectral broadening of optical parametric oscillators (OPOs)<xref ref-type="bibr" rid="b6">6</xref> and thulium-doped fibre laser<xref ref-type="bibr" rid="b7">7</xref><xref ref-type="bibr" rid="b8">8</xref><xref ref-type="bibr" rid="b9">9</xref> frequency combs in nonlinear chalcogenide-tapered fibres. Taper lifetimes have recently been improved to several days with hybrid silica-chalcogenide structures, in which octave-spanning frequency comb generation has been reported<xref ref-type="bibr" rid="b8">8</xref><xref ref-type="bibr" rid="b9">9</xref> using 65-fs pulses of only 18 pJ. Promising solutions for enhanced stability are presently under investigation with multimaterial chalcogenide nanotapers<xref ref-type="bibr" rid="b10">10</xref>. Another approach is the use of quasi-phase-matched periodically poled lithium niobate (PPLN) waveguides. Impressive results have been obtained and an octave-spanning phase-coherent supercontinuum has been generated<xref ref-type="bibr" rid="b11">11</xref>. However, absorption between 2,500 and 2,800 nm, and more importantly the limited transparency of lithium niobate beyond 4,500 nm, inhibits the scaling of the technology to longer wavelengths. Furthermore, high-energy pulses (7 nJ) are needed because of the moderate nonlinearity of the waveguide. In addition, during the poling of the crystal small random variations on the location of the walls of the poled domains are introduced. This aberration increases the conversion of parasitic processes significantly<xref ref-type="bibr" rid="b11">11</xref><xref ref-type="bibr" rid="b12">12</xref> and makes modelling difficult.</p><p>Silicon-based waveguides have been originally conceived for the telecommunication region. In this region, octave-spanning supercontinuum generation has been demonstrated by pumping silicon nitride waveguides with 150-pJ pulses centred at 1.3 μm (ref. <xref ref-type="bibr" rid="b13">13</xref>), but the coherence conservation in the supercontinuum generation process has not been investigated. Recently, the application of silicon technology to the mid-infrared spectral region has attracted significant interest<xref ref-type="bibr" rid="b14">14</xref><xref ref-type="bibr" rid="b15">15</xref><xref ref-type="bibr" rid="b16">16</xref>. Silicon nanophotonic wire waveguides can be engineered<xref ref-type="bibr" rid="b17">17</xref> within a nanometre precision in a standard CMOS facility. Such waveguides offer many advantages for mid-infrared nonlinear optics, mostly related to the wide transparency range of silicon (1.1–8 μm), its high nonlinear refractive index, the possibility of precise dispersion engineering of the waveguide platforms and the high refractive index contrast between the silicon waveguide core and the cladding material (typically, SiO<sub>2</sub> or air), which allows for densely integrated waveguide systems with a nonlinear parameter one to two orders of magnitude higher than that possible in the chalcogenide or silicon nitride systems.</p><p>In this article, we report on the design of strongly nonlinear, dispersion-controlled silicon photonic wire waveguides. We harness such chemically stable waveguides for mid-infrared supercontinuum generation, and we demonstrate a phase-coherent frequency comb generator with a 30-dB bandwidth spanning from 1,540 up to 3,200 nm, with coupled input pulse energies as low as 16 pJ.</p><sec disp-level="1" sec-type="results"><title>Results</title><sec disp-level="2"><title>A highly nonlinear dispersion-engineered silicon waveguide</title><p>The photonic wire is fabricated in a CMOS pilot line<xref ref-type="bibr" rid="b17">17</xref> on a 200-mm silicon-on-insulator (SOI) wafer and consisting of a 390-nm-thick silicon device layer on top of a 2-μm buried oxide layer. The inset in <xref ref-type="fig" rid="f1">Fig. 1a</xref>) shows a schematic cross-section of the silicon photonic wire. The 1-cm-long air-clad photonic wire has a rectangular cross-section of 1,600 nm × 390 nm. The waveguide is slightly over etched by 10 nm into the buried oxide. The photonic wire widens near the cleaved facets to a 3-μm wide waveguide section for improved coupling efficiency. As a result of the high nonlinear index of silicon<xref ref-type="bibr" rid="b18">18</xref> and the strong optical confinement obtained by the high linear refractive index of silicon, the nonlinear parameter in the silicon wire is 38 (Wm)<sup>−1</sup> at 2,300 nm for the highly confined quasi-TE mode. Such a high nonlinear parameter in silicon waveguides shows the advantage of using silicon over chalcogenide tapers (<italic>γ</italic>=4.5 (Wm)<sup>−1</sup> (ref. <xref ref-type="bibr" rid="b6">6</xref>)) and silicon nitride waveguides (<italic>γ</italic>=1.2 (Wm)<sup>−1</sup> (ref. <xref ref-type="bibr" rid="b13">13</xref>)) where the nonlinear parameter is much lower. As a result of the high confinement, the waveguide dispersion of the silicon photonic wire contributes strongly to the overall dispersion of the optical waveguide, such that group velocity dispersion can be engineered by optimizing the waveguide dimensions. The group velocity dispersion of the quasi-TE mode of the dispersion-engineered photonic wire waveguide as a function of wavelength is shown in <xref ref-type="fig" rid="f1">Fig. 1a</xref>. The group velocity dispersion is simulated with the help of a finite element mode solver (Fimmwave). The zero-dispersion wavelength is at 2,180 nm and the dispersion becomes positive (normal) at shorter wavelengths, while the dispersion remains low over a wide spectral band. By using a cut-back technique the propagation loss for the quasi-TE mode is determined to be <0.2 dB cm<sup>−1</sup> in the wavelength range of 2,200–2,400 nm.</p></sec><sec disp-level="2"><title>The experimental set-up for supercontinuum generation</title><p>The set-up is shown in <xref ref-type="fig" rid="f1">Fig. 1b</xref>. The frequency comb seed source consists of a homemade mid-infrared singly resonant OPO<xref ref-type="bibr" rid="b19">19</xref> at a repetition frequency of 100 MHz, synchronously pumped by a femtosecond mode-locked Ti-Sapphire laser. The OPO is tuned to a centre wavelength of 2,290 nm, close to the zero-dispersion wavelength of 2,180 nm of the silicon waveguide. Pumping a waveguide close to the zero-dispersion wavelength in the anomalous region allows for broadband supercontinuum generation<xref ref-type="bibr" rid="b5">5</xref>. The OPO has a pulse duration of 70 fs (see <xref ref-type="supplementary-material" rid="S1">Supplementary Fig. 1</xref>), while its average power is 35 mW. The ultrashort mid-infrared fs pulses coming from the OPO are coupled to the quasi-TE mode of the silicon photonic wire using a high (Numerical Aperture) NA (NA=0.85) chalcogenide lens with a focal length of 1.87 mm (see <xref ref-type="supplementary-material" rid="S1">Supplementary Methods</xref> for details). The output of the chip is coupled, using another chalcogenide lens, to a Fourier transform spectrometer to quantify the spectrum of the output pulses. The coupling loss at the input waveguide facet is estimated to be 12 dB, leading to an on-chip peak power of 225 W or pulse energy of 16 pJ. The high coupling loss at the waveguide facet stems from the bad overlap of the quasi-TE mode of the waveguide and the mode profile at the focus plane of the lens. However, spot size converters<xref ref-type="bibr" rid="b20">20</xref> could be used to significantly improve the coupling efficiency. We note that the coupled pulse energy and pulse duration that we use are similar to that used in ref. <xref ref-type="bibr" rid="b8">8</xref> for phase-coherent supercontinuum generation in a chalcogenide-silica hybrid waveguide.</p></sec><sec disp-level="2"><title>Spectral broadening in a silicon photonic nanowire waveguide</title><p>The spectra at the input and output of the waveguide are shown in <xref ref-type="fig" rid="f2">Fig. 2</xref>) for a pulse energy of 16 pJ. Spectra at lower pulse energies can be found in <xref ref-type="supplementary-material" rid="S1">Supplementary Fig. 2</xref>. The spectrum of the pulses is significantly broadened in the silicon photonic wire waveguide and spans more than an octave: the 30-dB bandwidth spans from 1,540 up to 3,200 nm at the output. The peak at 1,600 nm is located in the normal dispersion regime of the waveguide and is generated through dispersive wave generation, a method used to spectrally extend a supercontinuum<xref ref-type="bibr" rid="b16">16</xref>. In the course of the several weeks of experimental investigations, we did not observe any modification of the characteristics of the supercontinuum at the output of the silicon waveguide. Consistently, SOI platforms are used in electronics<xref ref-type="bibr" rid="b21">21</xref> and optics<xref ref-type="bibr" rid="b22">22</xref> during years without degradation.</p></sec><sec disp-level="2"><title>A phase-coherent supercontinuum</title><p>We experimentally investigate the phase coherence of the supercontinuum generated in the waveguide by beat note measurements with a set of narrow line-width continuous-wave lasers. Such a characterization technique for assessing comb coherence properties is an alternative to that involving a <italic>f</italic>–2<italic>f</italic> interferometer<xref ref-type="bibr" rid="b23">23</xref> and it is well documented in the literature, for example refs <xref ref-type="bibr" rid="b3">3</xref>, <xref ref-type="bibr" rid="b4">4</xref>, <xref ref-type="bibr" rid="b24">24</xref>. Here it was chosen because our foreseen applications<xref ref-type="bibr" rid="b25">25</xref> to molecular spectroscopy do not require self-referencing of the comb. In this characterization, all laser systems, including the continuous wave ones, are free-running. First, we beat the free-running seed source with a tunable continuous wave OPO (Argos Aculight, line-width ~60 kHz at 500 μs) at 2,400 nm on a fast InGaAsSb photodetector (<xref ref-type="fig" rid="f3">Fig. 3a</xref>). We then beat the supercontinuum output with the same OPO (<xref ref-type="fig" rid="f3">Fig. 3b,c</xref>), respectively, tuned at 2,418 and 2,580 nm. We finally beat (<xref ref-type="fig" rid="f3">Fig. 3d</xref>), on a fast InGaAs detector, the supercontinuum with a narrow line-width erbium-doped fibre laser (Koheras AdjustiK E15, NKT Photonics, line-width 0.1 kHz at 100 μs) at 1,586 nm, far from the seed wavelength. All radiofrequency spectra are recorded with a 100-kHz resolution bandwidth, and a spectrum with a 105-MHz span shows three isolated lines. The strong beat signal at 100 MHz corresponds to the repetition frequency of the fs OPO, while the other two beat notes correspond to the beat signal generated by the continuous wave lasers and the two spectrally closest lines of the frequency comb. The line-width of the beat notes, measured with a 10-kHz-resolution bandwidth (insets in <xref ref-type="fig" rid="f3">Fig. 3a–d</xref>) is limited by the instabilities of the free-running lasers, but it is found to be ~50 kHz, without noticeable broadening relative to the fs OPO seed source. The width of the free-running beat notes is the convolution of the width of the two beating laser lines. However, the width of the lines of the free-running femtosecond mode-locked Ti-Sapphire laser used to synchronously pump the seed fs OPO is similar. Stabilizing the system against a radiofrequency reference, such as a caesium clock, is not expected to bring significant line-width reduction: the locking electronics would need a bandwidth that only compensates for slow fluctuations (~100 Hz) to avoid ‘coherence collapse’ by multiplication of the phase noise of the radiofrequency reference<xref ref-type="bibr" rid="b26">26</xref>. We note that our measured line-widths are in full agreement with that of other free-running or radiofrequency-referenced frequency comb systems<xref ref-type="bibr" rid="b26">26</xref>. Our investigation thus demonstrates the frequency comb structure of the supercontinuum.</p></sec><sec disp-level="2"><title>Comparison with simulations</title><p>The coherence of the supercontinuum can be simulated and such simulations can be used to confirm the frequency comb structure at the probed wavelengths as well as indicating the coherence over the whole bandwidth. The supercontinuum generation can be simulated by solving the generalized nonlinear Schrödinger equation numerically with a split-step Fourier method<xref ref-type="bibr" rid="b5">5</xref> (see Methods). The simulation takes the linear propagation loss, the nonlinear phase shift, the three-photon absorption and both the induced absorption and dispersion by the carriers into account. In the simulation the nonlinear parameter <italic>γ</italic> is assumed to be 38 (Wm)<sup>−1</sup>, the linear propagation loss is assumed to be 0.1 dB cm<sup>−1</sup> and the three-photon absorption coefficient is assumed to be 0.025 cm<sup>3 </sup>GW<sup>−2</sup> (ref. <xref ref-type="bibr" rid="b27">27</xref>). <xref ref-type="fig" rid="f4">Figure 4a</xref>) shows the evolution of the spectrum of a 225-W peak power, 70-fs-long pulse as it is propagating along the silicon photonic wire waveguide. The simulated spectrum after 1-cm propagation is shown in <xref ref-type="fig" rid="f4">Fig. 4b</xref>. As shown in <xref ref-type="fig" rid="f4">Fig. 4b</xref>, the simulation agrees very well with the experimental results. The simulation of the spectral evolution of the pulse along the photonic wire length reveals (<xref ref-type="fig" rid="f4">Fig. 4a</xref>) that, in the first millimeter of propagation, self-phase modulation is the primary mechanism for spectral broadening. The spectrum is further broadened into the telecom wavelength range, where the group velocity dispersion of the waveguide is normal, through dispersive wave generation<xref ref-type="bibr" rid="b28">28</xref>. The use of the short pulses favours the processes such as dispersive wave generation and self-phase modulation. Unlike in ref. <xref ref-type="bibr" rid="b29">29</xref> where longer, ps pulses were used and the spectral broadening primarily results of amplification of background noise (modulation instability), the nonlinear process of dispersive wave generation and self-phase modulation maintain the coherence in the pulse.</p><p>The coherence of the supercontinuum can be simulated by including shot noise at the input. The noise <italic>E</italic><sub>noise</sub>(<italic>t</italic>) at the input is assumed to be a random variable with a stochastic distribution <inline-formula id="d33e576"><inline-graphic id="d33e577" xlink:href="ncomms7310-m1.jpg"></inline-graphic></inline-formula>, with <italic>h</italic> the Planck constant and <italic>υ</italic> the frequency of the photons, and analysing an ensemble of simulated supercontina<xref ref-type="bibr" rid="b30">30</xref>. The first-order coherence function</p><p><disp-formula id="eq2"><inline-graphic id="d33e590" xlink:href="ncomms7310-m2.jpg"></inline-graphic></disp-formula></p><p>is calculated for an ensemble of 100 spectra and is shown in <xref ref-type="fig" rid="f4">Fig. 4c</xref>. The coherence is close to unity over the whole spectrum, indicating that the generated supercontinuum is coherent over its entire bandwidth.</p><p>To emphasize the comb structure of the supercontinuum spectrum, which results from the pulse-to-pulse coherence, the spectrum of the pulse train at the output of the chip was simulated with a resolution of 10 kHz in a narrow band interval. The spectrum is simulated by first generating a set of pulses including the input shot noise, but excluding timing jitter and residual intensity noise, as discussed above. These pulses were stacked together in a pulse train with a repetition frequency of 100 MHz. The Fourier transform was calculated to generate the spectrum of the pulse train (see <xref ref-type="supplementary-material" rid="S1">Supplementary Methods</xref> and <xref ref-type="supplementary-material" rid="S1">Supplementary Fig. 3</xref> for details). <xref ref-type="fig" rid="f5">Figure 5</xref> shows the spectrum of a train of 1,000 pulses, calculated in a 500-MHz interval at 1,586 nm. The independent comb lines can clearly be seen. The inset of <xref ref-type="fig" rid="f5">Fig. 5</xref> shows one individual comb line sampled with a resolution of 10 kHz by calculating the spectrum of a pulse train consisting of 10,000 pulses. Similar simulations were performed in an interval at 2,418 and 2,580 nm, confirming the comb structure of the supercontinuum (see <xref ref-type="supplementary-material" rid="S1">Supplementary Fig. 4</xref>). In the simulations, the width of the comb lines is only limited by the time window used.</p><p>Interestingly, such nonlinear processes in silicon wires can be harnessed with other mid-infrared ultrashort pulse pump laser systems of different wavelength than the OPO employed here. For example, our simulations (<xref ref-type="supplementary-material" rid="S1">Supplementary Discussion</xref> and <xref ref-type="supplementary-material" rid="S1">Supplementary Fig. 5</xref>) indicate that a thulium-doped mode-locked fibre laser can be used as well to generate a phase-coherent octave-spanning supercontinuum in a dispersion-engineered silicon waveguide.</p></sec></sec><sec disp-level="1" sec-type="discussion"><title>Discussion</title><p>Using a silicon nanowire on a chip, we have demonstrated an octave-spanning frequency comb spanning from the telecom wavelength window ~1,500 nm to the mid-infared wavelength range at 3,300 nm. Such frequency comb is readily suitable for direct frequency comb spectroscopy, particularly for dual-comb spectroscopy with, for example, adaptive sampling<xref ref-type="bibr" rid="b25">25</xref>. Improved dispersion engineering could potentially extend the supercontinuum over the whole transparency window of the SOI platform (1,100–4,000 nm), limited by the buried oxide. Even broader bandwidths could be further obtained up to 5,500 nm with silicon on sapphire waveguide platforms<xref ref-type="bibr" rid="b31">31</xref><xref ref-type="bibr" rid="b32">32</xref>. By using waveguide designs where the buried oxide is removed<xref ref-type="bibr" rid="b14">14</xref><xref ref-type="bibr" rid="b15">15</xref><xref ref-type="bibr" rid="b33">33</xref>, the entire silicon transparency window (up to 8,500 nm) could be covered. As many molecules have strong rovibrational lines in the mid-infrared range, such developments would contribute in expanding the intriguing capabilities of molecular spectroscopy with frequency combs to the molecular fingerprint region. Such broadband supercontinua may also lead to self-referenced mid-infrared frequency comb systems, as needed for precision measurements in frequency metrology and in some implementations of direct frequency comb spectroscopy<xref ref-type="bibr" rid="b1">1</xref>. The rapid progress in the development of miniaturized mid-infrared frequency comb generators, as reported for instance with quantum cascade lasers<xref ref-type="bibr" rid="b2">2</xref><xref ref-type="bibr" rid="b4">4</xref> or high-quality factor microresonators<xref ref-type="bibr" rid="b34">34</xref>, might lead to an entirely new strategy for a compact source of ultrashort pulses in the future. Our work would then represent an essential building block paving the road for an octave-spanning frequency comb entirely generated on a chip. Such prospect would be of interest to, for example, chemical sensing, calibration of astronomical spectrographs, environmental monitoring or free-space communications.</p></sec><sec disp-level="1" sec-type="methods"><title>Methods</title><sec disp-level="2"><title>Description of the mid-infrared frequency comb seed source</title><p>The frequency comb generator that seeds the silicon waveguide is a home-made femtosecond synchronously pumped OPO. Its design and characterization are described in ref. <xref ref-type="bibr" rid="b19">19</xref>. Here we just reproduce the details that are useful for the description of the present experiment. The pump source of the OPO is a Kerr-lens mode-locked Ti:sapphire oscillator with a repetition frequency of 100 MHz, an average power of 1 W, a central wavelength of 790 nm and a pulse duration of 20 fs. The nonlinear crystal of the OPO is made of MgO:PPLN with a fan-out grating interaction length of <italic>l</italic>=500 μm. The OPO cavity is a dispersion-controlled four-mirror standing-wave design with two planoconcave mirrors and four plane mirrors. We tune the central wavelength of the idler of the OPO to 2,290 nm. The average output power is 35 mW. The idler spectrum is shown in <xref ref-type="fig" rid="f2">Fig. 2b</xref>. We measure the pulse duration with a home-made autocorrelator based on two-photon absorption in a InGaAs photodetector. The autocorrelation (<xref ref-type="supplementary-material" rid="S1">Supplementary Fig. 1</xref>) reveals a pulse duration of 72 fs, assuming a <italic>sech</italic><sup>2</sup> profile.</p></sec><sec disp-level="2"><title>Simulations</title><p>The spectral evolution of the pulses along the waveguide is simulated by solving the generalized nonlinear Schrodinger equation numerically using a split-step approach<xref ref-type="bibr" rid="b35">35</xref>. We solve</p><p><disp-formula id="eq3"><inline-graphic id="d33e692" xlink:href="ncomms7310-m3.jpg"></inline-graphic></disp-formula></p><p>Here <italic>E</italic>(<italic>z</italic>, <italic>t</italic>) is the envelope of the electric field of the short pulses, <italic>β</italic><sub>k</sub> is the kth order dispersion coefficient, <italic>α</italic><sub>l</sub> the linear propagation loss, <italic>α</italic><sub>3eff</sub> the effective third-order absorption coefficient, <italic>α</italic><sub>c</sub> the free carrier absorption coefficient, <italic>μ</italic> takes the free carrier dispersion in account, <italic>γ</italic> is the nonlinear parameter of the waveguide, while the integral takes in account the fractional Raman response. The effective third-order absorption coefficient can be calculated as <inline-formula id="d33e732"><inline-graphic id="d33e733" xlink:href="ncomms7310-m4.jpg"></inline-graphic></inline-formula> (ref. <xref ref-type="bibr" rid="b36">36</xref>), where <italic>α</italic><sub><italic>3</italic></sub> is the third-order nonlinear absorption coefficient in silicon of ~2.5 × 10<sup>−26 </sup>m<sup>3 </sup>GW<sup>−2</sup> (refs <xref ref-type="bibr" rid="b27">27</xref>, <xref ref-type="bibr" rid="b37">37</xref>) and <italic>A</italic><sub>5eff</sub>=0.5 μm<sup>2</sup> the fifth-order mode area. The carrier-induced absorption coefficient is proportional to the carrier density <italic>N</italic><sub>c</sub>, such that <italic>α</italic><sub>c</sub>=<italic>σN</italic><sub>c</sub>, where <italic>σ</italic>=2.77 × 10<sup>−21 </sup>m<sup>2</sup> (ref. <xref ref-type="bibr" rid="b38">38</xref>), while <inline-formula id="d33e800"><inline-graphic id="d33e801" xlink:href="ncomms7310-m5.jpg"></inline-graphic></inline-formula>with <italic>k</italic><sub>c</sub>=1.35 × 10<sup>−27 </sup>m<sup>3</sup> (ref. <xref ref-type="bibr" rid="b38">38</xref>). The evolution of the carrier density itself can be calculated as <inline-formula id="d33e818"><inline-graphic id="d33e819" xlink:href="ncomms7310-m6.jpg"></inline-graphic></inline-formula> (ref. <xref ref-type="bibr" rid="b38">38</xref>), where <italic>h</italic> is Planck’s constant and <italic>τ</italic> the carrier lifetime, estimated to be 1 ns (ref. <xref ref-type="bibr" rid="b39">39</xref>). It was assumed that the pulse was a hyperbolic secant with a full-width at half-maximum of 70 fs.</p></sec></sec><sec disp-level="1"><title>Author contributions</title><p>B.K. performed the numerical dispersion design calculations with guidance from R.B. and G.R., J.V.C. and P.V. supervised the waveguide device fabrication process. B.K., T.I., S.H. and M.Y. performed the supercontinuum generation experiment as well as the beat note experiment with guidance and supervision from T.W.H. and N.P. T.I., S.H. and M.Y. performed the autocorrelation experiment under the supervision of N.P. B.K., F.L. and S.C. performed the simulations on the coherence. B.K. drafted the manuscript. All authors provided comments and suggestions for improvements.</p></sec><sec disp-level="1"><title>Additional information</title><p><bold>How to cite this article:</bold> Kuyken, B. <italic>et al</italic>. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide. <italic>Nat. Commun.</italic> 6:6310 doi: 10.1038/ncomms7310 (2015).</p></sec><sec sec-type="supplementary-material" id="S1"><title>Supplementary Material</title><supplementary-material id="d33e18" content-type="local-data"><caption><title>Supplementary Information</title><p>Supplementary Figures 1-5, Supplementary Methods, Supplementary Discussion and Supplementary References</p></caption><media xlink:href="ncomms7310-s1.pdf"></media></supplementary-material></sec></body><back><ack><p>B.K. acknowledges the special research fund of Ghent University (BOF), for a post doctoral fellowship. We are grateful to Dr Antonin Poisson and Dr Clément Lafargue for experimental support. This work was partly carried out in the framework of the Methusalem project ‘Smart Photonic Chips’ and the FP7-ERC-INSPECTRA, FP7-ERC-MIRACLE and FP7-ERC-Multicomb (Advanced Investigator Grant 267854) projects.</p></ack><ref-list><ref id="b1"><mixed-citation publication-type="journal"><name><surname>Schliesser</surname><given-names>A.</given-names></name>, <name><surname>Picqué</surname><given-names>N.</given-names></name> & <name><surname>Hänsch</surname><given-names>T. W.</given-names></name><article-title>Mid-infrared frequency combs</article-title>. <source>Nat. Photon.</source><volume>6</volume>, <fpage>440</fpage>–<lpage>449</lpage> (<year>2012</year>).</mixed-citation></ref><ref id="b2"><mixed-citation publication-type="journal"><name><surname>Hugi</surname><given-names>A.</given-names></name>, <name><surname>Villares</surname><given-names>G.</given-names></name>, <name><surname>Blaser</surname><given-names>S.</given-names></name>, <name><surname>Liu</surname><given-names>H.</given-names></name> & <name><surname>Faist</surname><given-names>J.</given-names></name><article-title>Mid-infrared frequency comb based on a quantum cascade laser</article-title>. <source>Nature</source><volume>492</volume>, <fpage>229</fpage>–<lpage>233</lpage> (<year>2012</year>).<pub-id pub-id-type="pmid">23235876</pub-id></mixed-citation></ref><ref id="b3"><mixed-citation publication-type="journal"><name><surname>Wang</surname><given-names>C. Y.</given-names></name><etal></etal>. <article-title>Mid-infrared optical frequency combs at 2.5 μm based on crystalline microresonators</article-title>. <source>Nat. Commun.</source><volume>4</volume>, <fpage>1345</fpage> (<year>2013</year>).<pub-id pub-id-type="pmid">23299895</pub-id></mixed-citation></ref><ref id="b4"><mixed-citation publication-type="journal"><name><surname>Burghoff</surname><given-names>D.</given-names></name><etal></etal>. <article-title>Terahertz laser frequency combs</article-title>. <source>Nat. Photon.</source><volume>8</volume>, <fpage>462</fpage>–<lpage>467</lpage> (<year>2014</year>).</mixed-citation></ref><ref id="b5"><mixed-citation publication-type="journal"><name><surname>Dudley</surname><given-names>J. M.</given-names></name>, <name><surname>Genty</surname><given-names>G.</given-names></name> & <name><surname>Coen</surname><given-names>S.</given-names></name><article-title>Supercontinuum generation in photonic crystal fiber</article-title>. <source>Rev. Mod. Phys.</source><volume>78</volume>, <fpage>1135</fpage>–<lpage>1184</lpage> (<year>2006</year>).</mixed-citation></ref><ref id="b6"><mixed-citation publication-type="journal"><name><surname>Marandi</surname><given-names>A.</given-names></name><etal></etal>. <article-title>Mid-infrared supercontinuum generation in tapered chalcogenide fiber for producing octave-spanning frequency comb around 3 μm</article-title>. <source>Opt. Express</source><volume>20</volume>, <fpage>24218</fpage>–<lpage>24225</lpage> (<year>2012</year>).<pub-id pub-id-type="pmid">23187184</pub-id></mixed-citation></ref><ref id="b7"><mixed-citation publication-type="journal"><name><surname>Rudy</surname><given-names>C. W.</given-names></name>, <name><surname>Marandi</surname><given-names>A.</given-names></name>, <name><surname>Vodopyanov</surname><given-names>K. L.</given-names></name> & <name><surname>Byer</surname><given-names>R. L.</given-names></name><article-title>Octave-spanning supercontinuum generation in in situ tapered As<sub>2</sub>S<sub>3</sub> fiber pumped by a thulium-doped fiber laser</article-title>. <source>Opt. Lett.</source><volume>38</volume>, <fpage>2865</fpage>–<lpage>2868</lpage> (<year>2013</year>).<pub-id pub-id-type="pmid">23903165</pub-id></mixed-citation></ref><ref id="b8"><mixed-citation publication-type="journal"><name><surname>Lee</surname><given-names>K.</given-names></name><etal></etal>. <article-title>Mid-infrared frequency combs from coherent supercontinuum in chalcogenide nanospike</article-title>. <source>Opt. Lett.</source><volume>39</volume>, <fpage>2056</fpage>–<lpage>2059</lpage> (<year>2014</year>).<pub-id pub-id-type="pmid">24686673</pub-id></mixed-citation></ref><ref id="b9"><mixed-citation publication-type="journal"><name><surname>Granzow</surname><given-names>N.</given-names></name><etal></etal>. <article-title>Mid-infrared supercontinuum generation in As2S3-silica ‘nano-spike’ step-index waveguide</article-title>. <source>Opt. Express</source><volume>21</volume>, <fpage>10969</fpage>–<lpage>10977</lpage> (<year>2013</year>).<pub-id pub-id-type="pmid">23669953</pub-id></mixed-citation></ref><ref id="b10"><mixed-citation publication-type="other"><name><surname>Shabahang</surname><given-names>S.</given-names></name><etal></etal>. <italic>CLEO: 2013, OSA Technical Digest</italic>. Paper SW3I.2 (Optical Society of America, San Jose, CA, USA, 2013) <ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1364/CLEO_SI.2014.SW3I.2">http://dx.doi.org/10.1364/CLEO_SI.2014.SW3I.2</ext-link>.</mixed-citation></ref><ref id="b11"><mixed-citation publication-type="journal"><name><surname>Phillips</surname><given-names>C. R.</given-names></name><etal></etal>. <article-title>Supercontinuum generation in quasi-phase-matched LiNbO<sub>3</sub> waveguide pumped by a Tm-doped fiber laser system</article-title>. <source>Opt. Lett.</source><volume>36</volume>, <fpage>3912</fpage>–<lpage>3914</lpage> (<year>2011</year>).<pub-id pub-id-type="pmid">21964139</pub-id></mixed-citation></ref><ref id="b12"><mixed-citation publication-type="journal"><name><surname>Phillips</surname><given-names>C. R.</given-names></name>, <name><surname>Pelc</surname><given-names>J. S.</given-names></name> & <name><surname>Fejer</surname><given-names>M. M.</given-names></name><article-title>Parametric processes in quasi-phasematching gratings with random duty cycle errors</article-title>. <source>J. Opt. Soc. Am. B</source><volume>30</volume>, <fpage>982</fpage>–<lpage>993</lpage> (<year>2013</year>).</mixed-citation></ref><ref id="b13"><mixed-citation publication-type="journal"><name><surname>Halir</surname><given-names>R.</given-names></name><etal></etal>. <article-title>Ultrabroadband supercontinuum generation in a CMOS-compatible platform</article-title>. <source>Opt. Lett.</source><volume>37</volume>, <fpage>1685</fpage>–<lpage>1687</lpage> (<year>2012</year>).<pub-id pub-id-type="pmid">22627537</pub-id></mixed-citation></ref><ref id="b14"><mixed-citation publication-type="journal"><name><surname>Soref</surname><given-names>R.</given-names></name><article-title>Mid-infrared photonics in silicon and germanium</article-title>. <source>Nat. Photon.</source><volume>4</volume>, <fpage>495</fpage>–<lpage>497</lpage> (<year>2010</year>).</mixed-citation></ref><ref id="b15"><mixed-citation publication-type="journal"><name><surname>Jalali</surname><given-names>B.</given-names></name><article-title>Nonlinear optics in the mid-infrared</article-title>. <source>Nat. Photon.</source><volume>4</volume>, <fpage>506</fpage>–<lpage>508</lpage> (<year>2010</year>).</mixed-citation></ref><ref id="b16"><mixed-citation publication-type="journal"><name><surname>Lau</surname><given-names>R.</given-names></name><etal></etal>. <article-title>Octave-spanning mid-infrared supercontinuum generation in silicon nanowaveguides</article-title>. <source>Opt. Lett.</source><volume>39</volume>, <fpage>4518</fpage>–<lpage>4525</lpage> (<year>2014</year>).<pub-id pub-id-type="pmid">25078217</pub-id></mixed-citation></ref><ref id="b17"><mixed-citation publication-type="journal"><name><surname>Bogaerts</surname><given-names>W.</given-names></name><etal></etal>. <article-title>Nanophotonic waveguides in silicon-on-insulator fabricated with CMOS technology</article-title>. <source>J. Lightw. Technol.</source><volume>23</volume>, <fpage>401</fpage>–<lpage>412</lpage> (<year>2005</year>).</mixed-citation></ref><ref id="b18"><mixed-citation publication-type="journal"><name><surname>Bristow</surname><given-names>A. D.</given-names></name>, <name><surname>Rotenberg</surname><given-names>N.</given-names></name> & <name><surname>Van Driel</surname><given-names>H. M.</given-names></name><article-title>Two-photon absorption and Kerr coefficients of silicon for 850-2200 nm</article-title>. <source>Appl. Phys. Lett.</source><volume>90</volume>, <fpage>191104</fpage> (<year>2007</year>).</mixed-citation></ref><ref id="b19"><mixed-citation publication-type="journal"><name><surname>Kumar</surname><given-names>S. C.</given-names></name><etal></etal>. <article-title>Few-cycle, broadband, mid-infrared optical parametric oscillator pumped by a 20-fs Ti:sapphire laser</article-title>. <source>Laser Photon. Rev.</source><volume>8</volume>, <fpage>L86</fpage>–<lpage>L91</lpage> (<year>2014</year>).</mixed-citation></ref><ref id="b20"><mixed-citation publication-type="journal"><name><surname>Pu</surname><given-names>M.</given-names></name>, <name><surname>Liu</surname><given-names>L.</given-names></name>, <name><surname>Ou</surname><given-names>H.</given-names></name>, <name><surname>Yvind</surname><given-names>K.</given-names></name> & <name><surname>Hvam</surname><given-names>J. M.</given-names></name><article-title>Ultra-low-loss inverted taper coupler for silicon-on-insulator ridge waveguide</article-title>. <source>Opt. Commun.</source><volume>283</volume>, <fpage>3678</fpage>–<lpage>3682</lpage> (<year>2010</year>).</mixed-citation></ref><ref id="b21"><mixed-citation publication-type="journal"><name><surname>Colinge</surname><given-names>J.</given-names></name><source>Silicon-on-Insulator Technology: Materials to VLSI</source> Kluwer Academic Publishers (<year>2004</year>).</mixed-citation></ref><ref id="b22"><mixed-citation publication-type="journal"><name><surname>Hochberg</surname><given-names>M.</given-names></name> & <name><surname>Jones</surname><given-names>T. B.</given-names></name><article-title>Towards Fabless silicon photonics</article-title>. <source>Nat. Photon.</source><volume>4</volume>, <fpage>492</fpage>–<lpage>494</lpage> (<year>2010</year>).</mixed-citation></ref><ref id="b23"><mixed-citation publication-type="journal"><name><surname>Udem</surname><given-names>T.</given-names></name>, <name><surname>Holzwarth</surname><given-names>R.</given-names></name> & <name><surname>Hänsch</surname><given-names>T. W.</given-names></name><article-title>Optical frequency metrology</article-title>. <source>Nature</source><volume>416</volume>, <fpage>233</fpage>–<lpage>237</lpage> (<year>2002</year>).<pub-id pub-id-type="pmid">11894107</pub-id></mixed-citation></ref><ref id="b24"><mixed-citation publication-type="journal"><name><surname>Gohle</surname><given-names>C.</given-names></name><etal></etal>. <article-title>A frequency comb in the extreme ultraviolet</article-title>. <source>Nature</source><volume>436</volume>, <fpage>234</fpage>–<lpage>237</lpage> (<year>2005</year>).<pub-id pub-id-type="pmid">16015324</pub-id></mixed-citation></ref><ref id="b25"><mixed-citation publication-type="journal"><name><surname>Ideguchi</surname><given-names>T.</given-names></name><etal></etal>. <article-title>Adaptive real-time dual-comb spectroscopy</article-title>. <source>Nat. Commun.</source><volume>5</volume>, <fpage>3375</fpage> (<year>2014</year>).<pub-id pub-id-type="pmid">24572636</pub-id></mixed-citation></ref><ref id="b26"><mixed-citation publication-type="journal"><name><surname>Diddams</surname><given-names>S. A.</given-names></name>, <name><surname>Ye</surname><given-names>J.</given-names></name> & <name><surname>Hollberg</surname><given-names>L.</given-names></name> in<source>Femtosecond Optical Frequency Comb: Principle, Operation and Applications</source> eds Ye J., Cundiff S. T. <fpage>225</fpage>–<lpage>262</lpage>Springer (<year>2005</year>).</mixed-citation></ref><ref id="b27"><mixed-citation publication-type="journal"><name><surname>Pearl</surname><given-names>S.</given-names></name>, <name><surname>Rotenberg</surname><given-names>N.</given-names></name> & <name><surname>Driel</surname><given-names>H. M.</given-names></name><article-title>Three photon absorption in silicon for 2300-3300 nm</article-title>. <source>Appl. Phys. Lett.</source><volume>93</volume>, <fpage>131102</fpage> (<year>2008</year>).</mixed-citation></ref><ref id="b28"><mixed-citation publication-type="journal"><name><surname>Cristiani</surname><given-names>I.</given-names></name>, <name><surname>Tediosi</surname><given-names>R.</given-names></name>, <name><surname>Tartara</surname><given-names>L.</given-names></name> & <name><surname>Degiorgio</surname><given-names>V.</given-names></name><article-title>Dispersive wave generation by solitons in microstructured optical fibers</article-title>. <source>Opt. Express</source><volume>12</volume>, <fpage>124</fpage>–<lpage>135</lpage> (<year>2004</year>).<pub-id pub-id-type="pmid">19471518</pub-id></mixed-citation></ref><ref id="b29"><mixed-citation publication-type="journal"><name><surname>Kuyken</surname><given-names>B.</given-names></name><etal></etal>. <article-title>Mid-infrared to telecom-band supercontinuum generation in highly nonlinear silicon-on-insulator wire waveguides</article-title>. <source>Opt. Express</source><volume>19</volume>, <fpage>20172</fpage>–<lpage>20181</lpage> (<year>2011</year>).<pub-id pub-id-type="pmid">21997028</pub-id></mixed-citation></ref><ref id="b30"><mixed-citation publication-type="journal"><name><surname>Ruehl</surname><given-names>A.</given-names></name><etal></etal>. <article-title>Ultrabroadband coherent supercontinuum frequency comb</article-title>. <source>Phys. Rev. A</source><volume>84</volume>, <fpage>11806</fpage>–<lpage>11811</lpage> (<year>2011</year>).</mixed-citation></ref><ref id="b31"><mixed-citation publication-type="journal"><name><surname>Baehr-Jones</surname><given-names>T.</given-names></name><etal></etal>. <article-title>Silicon-on-sapphire integrated waveguides for the mid-infrared</article-title>. <source>Opt. Express</source><volume>18</volume>, <fpage>12127</fpage>–<lpage>12135</lpage> (<year>2010</year>).<pub-id pub-id-type="pmid">20588335</pub-id></mixed-citation></ref><ref id="b32"><mixed-citation publication-type="journal"><name><surname>Li</surname><given-names>F.</given-names></name><etal></etal>. <article-title>Low propagation loss silicon-on-sapphire waveguides for the mid-infrared</article-title>. <source>Opt. Express</source><volume>19</volume>, <fpage>15212</fpage>–<lpage>15220</lpage> (<year>2011</year>).<pub-id pub-id-type="pmid">21934884</pub-id></mixed-citation></ref><ref id="b33"><mixed-citation publication-type="journal"><name><surname>Soref</surname><given-names>R.</given-names></name>, <name><surname>Emelett</surname><given-names>A.</given-names></name> & <name><surname>Buchwald</surname><given-names>W. R.</given-names></name><article-title>Silicon waveguided components for the long-wave infrared region</article-title>. <source>J. Opt A Pure Appl. Opt.</source><volume>8</volume>, <fpage>840</fpage>–<lpage>853</lpage> (<year>2006</year>).</mixed-citation></ref><ref id="b34"><mixed-citation publication-type="other"><name><surname>Griffith</surname><given-names>A. G.</given-names></name><etal></etal>. Silicon-chip mid-infrared frequency comb generation. Preprint at <ext-link ext-link-type="uri" xlink:href="http://arXiv.org/abs/1408.1039">http://arXiv.org/abs/1408.1039</ext-link> (<year>2014</year>).</mixed-citation></ref><ref id="b35"><mixed-citation publication-type="journal"><name><surname>Yin</surname><given-names>L.</given-names></name>, <name><surname>Lin</surname><given-names>Q.</given-names></name> & <name><surname>Agrawal</surname><given-names>G. P.</given-names></name><article-title>Soliton fission and supercontinuum generation in silicon waveguides</article-title>. <source>Opt. Lett.</source><volume>32</volume>, <fpage>391</fpage>–<lpage>393</lpage> (<year>2007</year>).<pub-id pub-id-type="pmid">17356663</pub-id></mixed-citation></ref><ref id="b36"><mixed-citation publication-type="journal"><name><surname>Husko</surname><given-names>C.</given-names></name><etal></etal>. <article-title>Non-trivial scaling of self-phase modulation and three-photon absorption in III–V photonic crystal waveguides</article-title>. <source>Opt. Express</source><volume>17</volume>, <fpage>22442</fpage>–<lpage>22451</lpage> (<year>2009</year>).<pub-id pub-id-type="pmid">20052168</pub-id></mixed-citation></ref><ref id="b37"><mixed-citation publication-type="journal"><name><surname>Gai</surname><given-names>X.</given-names></name><etal></etal>. <article-title>Nonlinear absorption and refraction in crystalline silicon in the mid-infrared</article-title>. <source>Laser Photon. Rev.</source><volume>7</volume>, <fpage>1054</fpage>–<lpage>1064</lpage> (<year>2013</year>).</mixed-citation></ref><ref id="b38"><mixed-citation publication-type="journal"><name><surname>Lin</surname><given-names>Q.</given-names></name>, <name><surname>Painter</surname><given-names>O. J.</given-names></name> & <name><surname>Agrawal</surname><given-names>G. P.</given-names></name><article-title>Nonlinear optical phenomena in silicon waveguides: modeling and applications</article-title>. <source>Opt. Express</source><volume>15</volume>, <fpage>16604</fpage>–<lpage>16644</lpage> (<year>2007</year>).<pub-id pub-id-type="pmid">19550949</pub-id></mixed-citation></ref><ref id="b39"><mixed-citation publication-type="journal"><name><surname>Boyraz</surname><given-names>O.</given-names></name>, <name><surname>Koonath</surname><given-names>P.</given-names></name>, <name><surname>Raghunathan</surname><given-names>V.</given-names></name> & <name><surname>Jalali</surname><given-names>B.</given-names></name><article-title>All optical switching and continuum generation in silicon waveguides</article-title>. <source>Opt. Express</source><volume>12</volume>, <fpage>4094</fpage>–<lpage>4102</lpage> (<year>2004</year>).<pub-id pub-id-type="pmid">19483951</pub-id></mixed-citation></ref></ref-list></back><floats-group><fig id="f1"><label>Figure 1</label><caption><title>The simulated dispersion of the photonic wire waveguide and the experimental set-up.</title><p>(<bold>a</bold>) The zero-dispersion wavelength of the quasi-TE mode is at 2,180 nm, while the dispersion is normal at shorter wavelengths and anomalous at longer wavelengths. The waveguide cross-section is shown in the inset. (<bold>b</bold>) Experimental set-up: the OPO pumped by a Ti-Sapphire mode-locked laser is coupled to the silicon chip with a lens. The output of the chip can be sent to a photodetector or a spectrometer.</p></caption><graphic xlink:href="ncomms7310-f1"></graphic></fig><fig id="f2"><label>Figure 2</label><caption><title>The spectrum at the input (red) and the output (black) of the silicon nanowire.</title><p>The input pulses are centred at 2,290 nm and have a coupled peak power of 225 W. Their spectrum is broadened in the silicon photonic wire such that it experimentally spans more than an octave: the 30-dB bandwidth covers from 1,540 to 3,200 nm. The arrows indicate the wavelength position where the phase coherence measurements are performed.</p></caption><graphic xlink:href="ncomms7310-f2"></graphic></fig><fig id="f3"><label>Figure 3</label><caption><title>Experimental radiofrequency spectra of the beat notes.</title><p>(<bold>a</bold>) Radiofrequency spectrum of the free-running beat note of the pump pulses and a narrow line-width source at 2,400 nm. (<bold>b</bold>–<bold>d</bold>) Free-running beat notes of the spectrally broadened pulses and a narrow line-width source at <italic>λ</italic>=2,418 nm, <italic>λ</italic>=2,580 nm and <italic>λ</italic>=1,586 nm, respectively. The insets in the figure show a high-resolution spectrum of the free-running beat notes. The free-running beat notes of the output pulses are measured to be ~50 kHz wide and are not broadened as compared with beat notes measured on the input pulses.</p></caption><graphic xlink:href="ncomms7310-f3"></graphic></fig><fig id="f4"><label>Figure 4</label><caption><title>The simulated spectral broadening and coherence of the pulses.</title><p>(<bold>a</bold>) Evolution of the spectral content of the optical pulse along the length of the silicon photonic wire waveguide. (<bold>b</bold>) Simulated spectra after 1 cm of propagation in the waveguide (blue) and the measured supercontinuum (red). (<bold>c</bold>) Simulated coherence as a function of wavelength.</p></caption><graphic xlink:href="ncomms7310-f4"></graphic></fig><fig id="f5"><label>Figure 5</label><caption><title>A simulated high-resolution spectrum of the silicon wire output.</title><p>The spectrum of the supercontinuum frequency comb is simulated over a 500-MHz bandwidth in the vicinity of 1,586 nm (198 THz). It reveals comb lines separated by 100 MHz in the. A high-resolution (10 kHz) inset around a comb line is also shown.</p></caption><graphic xlink:href="ncomms7310-f5"></graphic></fig></floats-group></pmc></record>Pour manipuler ce document sous Unix (Dilib)
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