Passive Mode-Locking and Tilted Waves in Broad-Area Vertical-Cavity Surface-Emitting Lasers

TL;DR

This paper demonstrates passive mode-locking in a broad-area VCSEL using optical feedback from a resonant saturable absorber mirror, resulting in high-power, short pulses with tunable emission.

Contribution

It introduces a novel mode-locking mechanism involving tilted waves and optical feedback at the Fourier plane, enabling tunable, high-power pulsed emission in broad-area VCSELs.

Findings

Achieved passive mode-locking with ~1 W peak power and 10 ps pulses.

Formed two tilted plane waves with opposite transverse components.

Tunable emission over 4 nm due to inhomogeneities in the saturable absorber.

Abstract

We show experimentally and theoretically that an electrically biased $200\,\mu$m multi-transverse mode Vertical-Cavity Surface-Emitting Laser can be passively mode-locked using optical feedback from a distant Resonant Saturable Absorber Mirror. This is achieved when one cavity is placed at the Fourier plane of the other. Such non conventional optical feedback leads to the formation of two tilted plane waves traveling in the external cavity with opposite transverse components and alternating in time at every round-trip. Each of these plane waves gives birth to a train of mode-locked pulses separated by twice the external cavity round-trip, while the two trains are time shifted by a round-trip. A large portion of the transverse section of the device contributes to mode-locked emission leading to pulses of approximately 1 W peak power and 10 ps width. We discuss how inhomogeneities in the transverse section of the saturable absorber select the emitted tilted waves, thus leading to tunable emission over 4 nm.