Low-spatial coherence electrically-pumped semiconductor laser for speckle-free full-field imaging

TL;DR

This paper introduces a novel chip-scale, electrically-pumped semiconductor laser with high power per mode and low spatial coherence, enabling speckle-free full-field imaging and overcoming limitations of traditional coherent laser sources.

Contribution

A new chaotic cavity laser design achieves simultaneous multimode lasing with low spatial coherence and high power per mode, suitable for speckle-free imaging applications.

Findings

Demonstrated speckle-free full-field imaging using the laser

Achieved high power per mode exceeding LEDs and thermal sources

Laser exhibits simultaneous lasing in ~1000 independent modes

Abstract

The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically-pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ~1000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications.