Transverse mode dynamics of vertical-cavity surface-emitting laser (VCSEL) under mode-selective optical feedback

Abstract

We investigate the relationship between the linearly polarized (LP) modes of a 6 μm oxide-aperture VCSEL under mode-selective optical feedback (OFB) targeting the LP₀₂ mode. A solitary VCSEL (SV) and a VCSEL under mode-selective OFB of strength R_f = 25%, 50%, 75%, 100% were evaluated at pump currents χ = 1.0 to χ = 1.5 in increments of 0.1. Correlation showed that mode-selective OFB forces the selected mode LP₀₂ into negative correlation against non-selected modes. While mutual information generally decreases at higher χ, the introduction of mode-selective OFB forces MI value to drop to near zero, manifesting independence from other modes. Transfer entropy revealed the cause for this behaviour wherein LP₀₂ mode drives the carrier density, which subsequently dictates the dynamics of non-selected LP modes. The phase difference and amplitude dynamics exhibited mode-selective feedback-induced intermittent phase locking and mode hopping of LP modes, respectively.