Degenerate optical parametric amplification in CMOS silicon

TL;DR

This paper demonstrates degenerate optical parametric amplification in CMOS silicon by breaking silicon's inversion symmetry with bias fields, enabling nonlinear optical devices compatible with existing CMOS fabrication processes.

Contribution

It presents the first on-chip degenerate $ ext{chi}^{(2)}$ optical parametric amplifier in silicon, expanding silicon photonics capabilities with nonlinear optical functionalities.

Findings

Achieved second-harmonic generation with 0.2% W$^{-1}$ efficiency.

Demonstrated degenerate $ ext{chi}^{(2)}$ optical parametric amplification with 0.02 dB gain.

Operated at a pump wavelength of 1196 nm with 3 mW on-chip pump power.

Abstract

Silicon is a common material for photonics due to its favorable optical properties in the telecom and mid-wave IR bands, as well as compatibility with a wide range of complementary metal-oxide semiconductor (CMOS) foundry processes. Crystalline inversion symmetry precludes silicon from natively exhibiting second-order nonlinear optical processes. In this work, we build on recent work in silicon photonics that break this material symmetry using large bias fields, thereby enabling $\chi^{(2)}$ interactions. Using this approach, we demonstrate both second-harmonic generation (with a normalized efficiency of $0.2\,\%\,\mathrm{W^{-1} cm^{-2}}$) and, to our knowledge, the first degenerate $\chi^{(2)}$ optical parametric amplifier (with relative gain of $0.02\,\mathrm{dB}$ using $3\,\mathrm{mW}$ of pump power on-chip at a pump wavelength of $1196\,\mathrm{nm}$) using silicon-on-insulator waveguides fabricated in a CMOS-compatible commercial foundry. We expect this technology to enable the integration of novel nonlinear optical devices such as optical parametric amplifiers, oscillators, and frequency converters into large-scale, hybrid photonic-electronic systems by leveraging the extensive ecosystem of CMOS fabrication.