# Optimization of Anisotropic Photonic Density of States for Raman Cooling

## TL;DR

This paper explores how anisotropic photonic density of states can be optimized to enhance Raman cooling efficiency in optical refrigeration, addressing the challenge of imbalance in Stokes and anti-Stokes scattering.

## Contribution

It introduces a framework for optimizing Raman cooling using anisotropic photonic DoS and demonstrates its importance for systems with lower symmetry.

## Key findings

- Optimization of Raman cooling figure of merit considering crystal orientations
- Anisotropic photonic DoS significantly improves cooling efficiency
- Applicable to various laser cooling methods with anisotropic media

## Abstract

Optical refrigeration of solids holds tremendous promise for applications in thermal management. It can be achieved through multiple mechanisms including inelastic anti-Stokes Brillouin and Raman scattering. However, engineering of these mechanisms remains relatively unexplored. The major challenge lies in the natural unfavorable imbalance in transition rates for Stokes and anti-Stokes scattering. We consider the influence of anisotropic photonic density of states on Raman scattering and derive expressions for cooling in such systems. We demonstrate optimization of the Raman cooling figure of merit considering all possible orientations for the material crystal and two example photonic crystals. We find that the anisotropic description of the photonic DoS and the optimization process is necessary to obtain the best Raman cooling efficiency for systems having lower symmetry. This general result applies to a wide array of other laser cooling methods in the presence of anisotropy.