Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides

TL;DR

This paper demonstrates a silicon nanophotonic optical parametric amplifier operating in the mid-infrared with high gain and broad bandwidth, enabling integrated all-optical signal processing and mid-IR light source generation.

Contribution

It introduces a silicon-based mid-IR parametric amplifier with record gain by operating at wavelengths where two-photon absorption is minimized, and achieves broadband amplification on a compact chip.

Findings

Achieved 25.4 dB gain in silicon nanophotonic waveguides.

Operated at mid-IR wavelength (~2200 nm) to avoid TPA.

Generated multiple mid-IR sources over a 500 nm spectral range.

Abstract

All-optical signal processing is envisioned as an approach to dramatically decrease power consumption and speed up performance of next-generation optical telecommunications networks. Nonlinear optical effects, such as four-wave mixing (FWM) and parametric gain, have long been explored to realize all-optical functions in glass fibers. An alternative approach is to employ nanoscale engineering of silicon waveguides to enhance the optical nonlinearities by up to five orders of magnitude, enabling integrated chip-scale all-optical signal processing. Previously, strong two-photon absorption (TPA) of the telecom-band pump has been a fundamental and unavoidable obstacle, limiting parametric gain to values on the order of a few dB. Here we demonstrate a silicon nanophotonic optical parametric amplifier exhibiting gain as large as 25.4 dB, by operating the pump in the mid-IR near one-half the band-gap energy (E~0.55eV, lambda~2200nm), at which parasitic TPA-related absorption vanishes. This gain is high enough to compensate all insertion losses, resulting in 13 dB net off-chip amplification. Furthermore, dispersion engineering dramatically increases the gain bandwidth to more than 220 nm, all realized using an ultra-compact 4 mm silicon chip. Beyond its significant relevance to all-optical signal processing, the broadband parametric gain also facilitates the simultaneous generation of multiple on-chip mid-IR sources through cascaded FWM, covering a 500 nm spectral range. Together, these results provide a foundation for the construction of silicon-based room-temperature mid-IR light sources including tunable chip-scale parametric oscillators, optical frequency combs, and supercontinuum generators.