Clarifying the impact of dual optical feedback on semiconductor lasers through analysis of the effective feedback phase

TL;DR

This paper investigates how the phase of dual optical feedback influences the stability of semiconductor lasers, revealing increased sensitivity and complex interactions that affect laser dynamics.

Contribution

It provides a detailed analysis of the feedback phase effects in dual-feedback laser systems, a topic not thoroughly explored before.

Findings

Feedback phase significantly affects laser stability.

Dual feedback increases sensitivity to phase changes.

Interference between feedback arms influences frequency shifts.

Abstract

Time-delayed optical feedback is known to trigger a wide variety of complex dynamical behavior in semiconductor lasers. Adding a second optical feedback loop is naturally expected to further increase the complexity of the system and its dynamics, but due to interference between the two feedback arms it was also quickly identified as a way to improve the laser stability. While these two aspects have already been investigated, the influence of the feedback phases, i.e. sub-wavelength changes in the mirror positions, on the laser behavior still remains to be thoroughly studied, despite indications that this parameter could have a significant impact. Here, we analyze the effect of the feedback phase on the laser stability in a dual-feedback configuration. We show an increased sensitivity of the laser system to feedback phase changes when two feedback loops are present, and clarify the interplay between the frequency shift induced by the feedback and the interferometric effect between the two feedback arms.