Fundamental entropic processes in the theory of optical thermodynamics

TL;DR

This paper develops a thermodynamic framework for multimoded optical systems, deriving analogues of classical thermodynamic laws and analyzing entropy behavior in photonic lattices under various conditions.

Contribution

It introduces an optical thermodynamics theory with laws analogous to classical thermodynamics, applied specifically to two-dimensional photonic lattices.

Findings

Derived an optical first law of thermodynamics.

Identified conditions for entropy extensivity in waveguide arrays.

Analyzed thermodynamic processes like isentropic and Joule expansions in optical systems.

Abstract

We study the statistical behavior of multimoded optical systems under equilibrium conditions. We investigate the role of variations of the system parameters in the thermodynamic description and derive, an optical analogue of the first law of thermodynamics, a generic expression for the work done to the system, and an optical Gibbs-Duhem equation. To demonstrate these effects, we focus in the case of two-dimensional photonic lattices. We study the conditions under which the entropy in such waveguide arrays can be considered as extensive. In this respect, small deviations from the extensive character of the entropy give rise to stress and strain terms. We examine how the conservation laws in such array configurations are affected by variations in the system parameters, and furthermore, we analyze the respective thermodynamic processes (isentropic and Joule-type expansions).