FDTD Simulation of Thermal Noise in Open Cavities

TL;DR

This paper presents a finite-difference time-domain (FDTD) numerical model to simulate thermal noise in open optical cavities, capturing both Markovian and non-Markovian regimes without prior cavity mode knowledge.

Contribution

The authors develop a novel FDTD-based approach to model thermal noise in open cavities, accounting for non-Markovian effects and eliminating the need for cavity mode pre-calculation.

Findings

FDTD model recovers standard quantum Langevin results in Markovian regime.

Simulation shows intracavity noise buildup depends on photon lifetime and radiation coherence.

Method effectively models thermal noise in time domain without prior cavity mode information.

Abstract

A numerical model based on the finite-difference time-domain (FDTD) method is developed to simulate thermal noise in open cavities owing to output coupling. The absorbing boundary of the FDTD grid is treated as a blackbody, whose thermal radiation penetrates the cavity in the grid. The calculated amount of thermal noise in a one-dimensional dielectric cavity recovers the standard result of the quantum Langevin equation in the Markovian regime. Our FDTD simulation also demonstrates that in the non-Markovian regime the buildup of the intracavity noise field depends on the ratio of the cavity photon lifetime to the coherence time of thermal radiation. The advantage of our numerical method is that the thermal noise is introduced in the time domain without prior knowledge of cavity modes.