Condensation of Thresholds in Multimode Microlasers

TL;DR

This paper demonstrates that by tailoring the spatial pump profile in multimode microlasers, multiple modes can be simultaneously activated at lower pump energies, enhancing their applicability in speckle-free imaging.

Contribution

It introduces a method to optimize pump profiles for achieving highly multimode lasing in microlasers based on ab initio laser theory.

Findings

Multiple modes can be turned on simultaneously with optimized pump profiles.

The optimal pump profile can be derived from the saturated gain profile.

Highly multimode lasing reduces spatial coherence for imaging applications.

Abstract

We show from ab initio laser theory that by choosing an appropriate spatial pump profile, many different spatial modes of a typical microlaser can be turned on at the same pump energy, substantially increasing the number, N, of simultaneous lasing modes. The optimal pump profile can be obtained simply from knowledge of the space-dependent saturated gain profile when the system is uniformly pumped up to the Nth modal threshold. We test this general result by applying it to a two-dimensional diffusive random laser and a microdisk laser. Achieving highly multimode lasing at reasonable pump powers is useful for reducing the spatial coherence of laser sources, making them suitable for use in speckle-free imaging and other applications.