Fast square-oscillations in semiconductor VCSELs with delayed orthogonal polarization feedback

TL;DR

This paper investigates fast square oscillations in semiconductor VCSELs with delayed orthogonal polarization feedback, revealing their origin from mode beating and mode rotation, with implications for optical communication and photonic computing.

Contribution

It provides the first detailed experimental analysis of fast square oscillations in VCSELs with delayed polarization feedback, linking them to mode beating and nonlinear dynamics.

Findings

Fast square oscillations originate from TE and TM mode beating.

Long delay induces low-frequency mode rotation.

The study offers an all-optical method for generating specialized signals.

Abstract

We present an experimental investigation into the generation of self-sustained and fast square oscillations from the TE mode of semiconductor VCSELs with delayed orthogonal polarization feedback. We find that the low frequency switching originates from the rotation of the TE and TM modes facilitated by a long time delay, but the fast oscillations are anchored to the frequency beating between the TE and TM modes and are modified by a half-wavelength ($\lambda/2$) plate. A comprehensive analysis of the evolution of the nonlinear dynamics is conducted and the related mechanism is discussed. Our study not only deepens our comprehension of laser nonlinear dynamics but also offers an all-optical approach for producing specialized signals, which could be instrumental in applications such as optical communications and photonic computing leveraging the complexity of long-delay systems.