The noise fluxes produced by the degree of first-order temporal coherence in a single mode class-A laser amplifier

TL;DR

This paper investigates the noise characteristics of a single mode class-A laser, analyzing how the degree of first-order temporal coherence influences noise fluxes and their bandwidth, with implications for laser stability and noise management.

Contribution

It introduces a detailed theoretical analysis linking the degree of first-order temporal coherence to noise fluxes in a class-A laser, including the effects of input signal and system parameters.

Findings

Noise fluxes depend on input signal detuning and system damping rates.

The degree of first-order temporal coherence relates to amplitude noise flux via its Fourier transform.

A flux conservation principle balances input pumping noise with output and spontaneous emission noise.

Abstract

The noise feature of a single mode class-A laser is investigated in the presence (amplifier) and absence (free-running) of an input signal. The Maxwell-Bloch equations of motion have been solved after adding the cavity Langevin force to calculate fluctuations that imposed to the atomic population inversion and the amplitude and phase of cavity electric field. The correlation function of these fluctuations is then used to derive the spontaneous emission, amplitude, and phase noise fluxes in the below and above-threshold states. The bandwidth of noise fluxes is not only adjusted by the amplitude and frequency detuning of input signal, but also by the laser pumping and cavity damping rates. On the other hand, the degree of first-order temporal coherence (DFOTC) is turned out as the correlation function of the amplitude fluctuation so that its Fourier transform led to the amplitude noise flux. The coherence time plays a dual role in order that it is equal to the damping rate invers of DFOTC and at the same time has an uncertainty relation with the bandwidth of amplitude noise flux. Finally, the flux conservation requires a balance between the input pumping noise flux and the output amplitude and spontaneous emission noise fluxes.