Giant nonlinear response at a plasmonic nanofocus drives efficient four-wave mixing

• Published in: Science (American Association for the Advancement of Science) Vol. 358; no. 6367; pp. 1179 - 1181
• Main Authors: Nielsen, Michael P., Shi, Xingyuan, Dichtl, Paul, Maier, Stefan A., Oulton, Rupert F.
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 01.12.2017; The American Association for the Advancement of Science
• Subjects: Broadband; Electromagnetic fields; Four-wave mixing; Light; Mixing processes; Nonlinear optics; Nonlinear response; Optical frequency; Optics; Phase matching; Photonics; Photons; Polymers; Silicon; Telecommunications; Wavelengths
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aao1467

Efficient optical frequency mixing typically must accumulate over large interaction lengths because nonlinear responses in natural materials are inherently weak. This limits the efficiency of mixing processes owing to the requirement of phase matching. Here, we report efficient four-wave mixing (FWM) over micrometer-scale interaction lengths at telecommunications wavelengths on silicon. We used an integrated plasmonic gap waveguide that strongly confines light within a nonlinear organic polymer. The gap waveguide intensifies light by nanofocusing it to a mode cross-section of a few tens of nanometers, thus generating a nonlinear response so strong that efficient FWM accumulates over wavelength-scale distances. This technique opens up nonlinear optics to a regime of relaxed phase matching, with the possibility of compact, broadband, and efficient frequency mixing integrated with silicon photonics.