Optimizing performance for on-chip SBS-based isolator

TL;DR

This paper numerically investigates a Brillouin-based on-chip optical isolator using a dual-pump scheme in a ridge waveguide, optimizing design parameters to achieve high isolation and bandwidth robustness.

Contribution

It introduces a novel on-chip SBS-based isolator design with optimized waveguide geometry and mode selection, enabling high isolation with fabrication tolerance.

Findings

Achieves 30 dB isolation over 38 nm bandwidth with 500 mW pump.

Maintains 20-30 dB isolation over 5-10 nm bandwidth despite fabrication errors.

Enhances acoustic confinement through mode and geometry optimization.

Abstract

Non-reciprocal optical components such as isolators and circulators are crucial for preventing catastrophic back-reflection and controlling optical crosstalk in photonic systems. While non-reciprocal devices based on Brillouin intermodal transitions have been experimentally demonstrated in chip-scale platforms, harnessing such interactions has required a suspended waveguide structure, which is challenging to fabricate and is potentially less robust than a non-suspended structure, thereby limiting the design flexibility. In this paper, we numerically investigate the performance of a Brillouin-based isolation scheme in which a dual-pump-driven optoacoustic interaction is used to excite confined acoustic waves in a traditional ridge waveguide. We find that acoustic confinement, and therefore the amount of Brillouin-driven mode conversion, can be enhanced by selecting an appropriate optical mode pair and waveguide geometry of two arsenic based chalcogenide platforms. Further, we optimize the isolator design in its entirety, including the input couplers, mode filters, the Brillouin-active waveguide as well as the device fabrication tolerances. We predict such a device can achieve 30 dB isolation over a 38 nm bandwidth when 500 mW pump power is used; in the presence of a +/- 10 nm fabrication-induced width error, such isolation can be maintained over a 5-10 nm bandwidth.