Thermal noise in complex systems

TL;DR

This paper introduces a method to compute Brownian noise spectral density in complex optomechanical systems and reports new mechanical loss measurements for high-purity GaAs across a broad temperature range, revealing multiple Debye loss peaks.

Contribution

It presents a novel approach using Levin's virtual pressure method for noise calculation and provides the first detailed loss measurements for GaAs over wide temperatures.

Findings

Identification of three Debye loss peaks in GaAs.

Activation energies for relaxation processes identified.

Light-induced damping effects observed in GaAs.

Abstract

We present a method to calculate the power spectral density of Brownian noise in complex optomechanical systems using Levin's approach of virtual pressure and present first mechanical loss measurements for high-purity GaAs over a wide temperature range from 7 K to 250 K. The loss reveals three Debye loss peaks. Each peak corresponds to an Arrhenius-like relaxation process with activation energies of 17.9 meV, 65.4 meV and 123 meV respectively. Additional light induced damping was observed for photon energies below and above the fundamental gap of GaAs in contrast to observations by Okamoto et al.