# Regularization of Vertical-Cavity Surface-Emitting Lasers emission by periodic non-Hermitian potentials

## TL;DR

This paper introduces a new method using periodic non-Hermitian potentials to stabilize and enhance the brightness of broad-area VCSELs by concentrating light into a central, narrow beam through asymmetric mode coupling.

## Contribution

It presents a novel physical mechanism employing non-Hermitian potentials to control and improve the emission stability and brightness of VCSELs, which is a new approach in laser physics.

## Key findings

- Achieves stable, bright, narrow emission beams from broad-area VCSELs.
- Identifies optimal phase differences for inward radial mode coupling.
- Shows unidirectional inward coupling enhances central intensity without requiring perfect PT-symmetry.

## Abstract

We propose a novel physical mechanism based on periodic non-Hermitian potentials to efficiently control the complex spatial dynamics of broad-area lasers, particularly in Vertical-Cavity Surface-Emitting Lasers (VCSELs), achieving a stable emission of maximum brightness. Radially dephased periodic refractive index and gain-loss modulations accumulate the generated light from the entire active layer and concentrate it around the structure axis to emit narrow, bright beams. The effect is due to asymmetric-inward radial coupling between transverse modes, for particular phase differences of the refractive index and gain-loss modulations. Light is confined into a central beam with large intensity opening the path to design compact, bright and efficient broad-area light sources. We perform a comprehensive analysis to explore the maximum central intensity enhancement and concentration regimes. The study reveals that the optimum schemes are those holding unidirectional inward coupling but not fulfilling a perfect local PT-symmetry.

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Source: https://tomesphere.com/paper/1902.04915