Ultrabroadband nonlinear optics in nanophotonic periodically poled lithium niobate waveguides

Abstract

Quasi-phasematched interactions in waveguides with quadratic nonlinearities enable highly efficient nonlinear frequency conversion. In this article, we demonstrate the first generation of devices that combine the dispersion-engineering available in nanophotonic waveguides with quasi-phasematched nonlinear interactions available in periodically poled lithium niobate (PPLN). This combination enables quasi-static interactions of femtosecond pulses, reducing the pulse energy requirements by several orders of magnitude, from picojoules to femtojoules. We experimentally demonstrate two effects associated with second harmonic generation. First, we observe efficient quasi-phasematched second harmonic generation with <100 fJ of pulse energy. Second, in the limit of strong phase-mismatch, we observe spectral broadening of both harmonics with as little as 2-pJ of pulse energy. These results lay a foundation for a new class of nonlinear devices, in which co-engineering of dispersion with quasi-phasematching enables efficient nonlinear optics at the femtojoule level.This document provides supplementary information to "Ultrabroadband Nonlinear Optics in Nanophotonic Periodically Poled Lithium Niobate Waveguides," Optica volume, first page (year), http://dx.doi.org/10.1364/optica.0.000000. In this supplemental, we discuss the calculation of the effective areas for nonlinear interactions in tightly confining waveguides. The detailed calculations presented here will help readers to reproduce the results shown in the main article.http://dx.

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