# Dynamics at Threshold in Mesoscale Class-B Lasers

## TL;DR

This paper investigates the intrinsic dynamics of threshold crossing in mesoscale Class B lasers using a simple rate equation model, providing approximate solutions and timescales that characterize their response to perturbations.

## Contribution

It introduces an analytical approach to understand the threshold dynamics of mesoscale lasers, extending insights to nanolasers and validating results with numerical simulations.

## Key findings

- Derived approximate solutions for population inversion and field intensity.
- Identified key timescales for laser response to perturbations.
- Validated analytical results with numerical simulations.

## Abstract

The threshold properties of very small lasers (down to the nanoscale) are a topic of active research in light of continuous progress in nanofabrication. With the help of a simple rate equation model we analyze the intrinsic, macroscopic dynamics of threshold crossing for Class B lasers. We use the deterministic aspects of the basic rate equations to extract some fundamental time constants from an approximate analysis of laser dynamics in the threshold region. Approximate solutions for the population inversion and for the field intensity, up to the point where the latter reaches macroscopic levels, are found and discussed. The resulting timescales characterize the laser's ability to respond to perturbations (external modulation or intrinsic fluctuations in the lasing transition region). Numerical verifications test the accuracy of these solutions and confirm their validity. The predictions are used to interpret experimental results obtained in mesoscale lasers and to speculated about their extension to nanolasers.