Abstract
We have studied low-dispersion slow light and its nonlinear enhancement in photonic crystal waveguides. In this work, we fabricated the waveguides using Si CMOS-compatible process. It enables us to integrate spotsize converters, which greatly simplifies the optical coupling from fibers as well as demonstration of the nonlinear enhancement. Two-photon absorption, self-phase modulation and four-wave mixing were observed clearly for picosecond pulses in a 200-μm-long device. In comparison with Si wire waveguides, a 60-120 fold higher nonlinearity was evaluated for a group index of 51. Unique intensity response also occurred due to the specific transmission spectrum and enhanced nonlinearities. Such slow light may add various functionalities in Si photonics, while loss reduction is desired for ensuring the advantage of slow light.
Highlights
With the rapid increase in photonic network traffic and related power consumption, advanced optical signal processing requiring fewer O/E conversions is desired, and thereby nonlinear optical devices are studied for all optical wavelength conversion, signal regeneration, and fast photonic switching
The lattice-shifted photonic crystal waveguide (LSPCW) we have developed so far exhibits LD slow light with a simple parameter tuning [7]
We demonstrate unique intensity response and four-wave mixing (FWM), which may be applicable for signal processing
Summary
With the rapid increase in photonic network traffic and related power consumption, advanced optical signal processing requiring fewer O/E conversions is desired, and thereby nonlinear optical devices are studied for all optical wavelength conversion, signal regeneration, and fast photonic switching. The CMOS process ensures large-scale photonic integration with high uniformity, high reproducibility, and low cost It is already used for fabricating Si wire and rib waveguides on silicon-on-insulator (SOI) substrate [11,12,13]. The thick silica box layer in the SOI substrate needs to be etched chemically in the backend process, but this often damages other devices This difficulty hampers the integration of spot-size converters (SSCs) [14] with PCWs. Without SSCs, the optical coupling loss between a lensed fiber and a cleaved PCW is usually as high as 15 20 dB/facet. We demonstrate unique intensity response and FWM, which may be applicable for signal processing
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