On-chip non-Hermitian optical parametric amplifiers with a large bandwidth

Recently, our groups have introduced the notion of optical parametric amplification based on non-Hermitian phase matching wherein the incorporation of loss can lead to gain in this nonlinear optical process. Previous simulation results using second-order nonlinear optical coupled-mode theory have demonstrated the potential of this technique as an alternative to the stringent phase-matching condition, which is often difficult to achieve in semiconductor platforms. Here we fortify this notion for the case of third-order nonlinearity by considering parametric amplification in silicon nanowires and illustrate the feasibility of these devices by employing rigorous finite-difference time-domain analysis using realistic materials and geometric parameters. Particularly, we demonstrate that by systematic control of the optical loss of the idler in a four-wave mixing process, we can achieve efficient unidirectional energy conversion from the pump to the signal component even when the typical phase-matching condition is violated. Importantly, our simulations show that a signal gain of similar to 9 dB for a waveguide length of a few millimeters is possible over a large bandwidth of several hundreds of nanometers (similar to 600 nm). This bandwidth is nearly 2 orders of magnitude larger than what can be achieved in the conventional silicon-photonics-based four-wave mixing process. (C) 2021 Optical Society of America

Automated summary

This research introduces an optical parametric amplification technique based on non-Hermitian phase matching, which utilizes losses to achieve gain in nonlinear optical processes. The study demonstrates efficient energy conversion from pump to signal component through controlled optical losses, even when standard phase-matching conditions are not met.