Balance between noise fluxes in free-running single-mode class-A lasers

TL;DR

This paper analyzes how laser pumping rate fluctuations affect noise fluxes in free-running single-mode class-A lasers, deriving correlation functions and confirming energy conservation laws.

Contribution

It introduces a method to calculate noise fluxes based on cavity Langevin forces and establishes a conservation relation linking pumping noise with laser variable fluctuations.

Findings

Derived correlation functions for cavity field and inversion fluctuations

Established a conservation relation for noise fluxes

Confirmed results through energy conservation law

Abstract

The fluctuation effect of laser pumping rate on the output noise fluxes of class-A lasers is investigated. The method is based on the role of cavity Langevin force as a fluctuating force in the absence of the atomic population inversion and dipole moment Langevin forces. The temporal fluctuations induced to the phase and amplitude of the cavity electric field and the atomic population inversion are calculated in both below and above threshold states. Our aim is to derive correlation functions for the fluctuating variables of the cavity electric field and the atomic population inversion to determine the noise fluxes emerging from the cavity mirrors and measured by an optical detector and those radiated in the form of spontaneous emission in all spatial directions. We introduce a heuristic conservation relation that connects the noise flux generated by the laser pumping system with those distributed among the laser variables. Finally, the results are confirmed by demonstrating the energy conservation law.