Intra-cavity cryogenic optical refrigeration using high power vertical external-cavity surface-emitting lasers (VECSELs).

Mohammadreza Ghasemkhani,Jeffrey G Cederberg,Mansoor Sheik-Bahae,Seth D Melgaard,Denis V Seletskiy,Alexander R Albrecht

doi:10.1364/oe.22.016232

Mohammadreza Ghasemkhani, Jeffrey G Cederberg + Show 4 more

Open Access

https://doi.org/10.1364/oe.22.016232

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Abstract

A 7% Yb:YLF crystal is laser cooled to 131 ± 1 K from room temperature by placing it inside the external cavity of a high power InGaAs/GaAs VECSEL operating at 1020 nm with 0.15 nm linewidth. This is the lowest temperature achieved in the intracavity geometry to date and presents major progress towards realizing an all-solid-state compact optical cryocooler.

Highlights

IntroductionSolid state laser cooling ( known as optical refrigeration) is based on the anti-Stokes fluorescence process [1,2,3,4,5]
Solid state laser cooling is based on the anti-Stokes fluorescence process [1,2,3,4,5]
By combining the highest performance cooling material to date, the Yb:YLF crystal, and high efficiency semiconductor vertical external-cavity surfaceemitting lasers (VECSELs), we have demonstrated cooling to an absolute temperature of 131 ± 1 K starting from room temperature

Summary

Introduction

Solid state laser cooling ( known as optical refrigeration) is based on the anti-Stokes fluorescence process [1,2,3,4,5]. Optical refrigeration has reached 114 K in a high-purity 10% Yb3+-doped yttrium lithium fluoride (Yb3+:YLF) crystal [6], utilizing a multi-pass geometry for enhancement of pump light absorption, important for low temperature operation. We focus on the enhancement of pump absorption by placing a 7% Yb:YLF crystal cooling sample inside of a high-efficiency laser cavity. The absorption of the pump laser by the rare-earth ions at the cooling wavelengths is typically very low (approximately 12% per pass), at low temperatures This in turn requires a multi-pass geometry to fully utilize the incident laser power. Longitudinal mode instabilities of the pump laser during high power operation, limited the applicability of this approach for cryogenic cooling These complications can be avoided by placing the sample inside of a laser cavity (intra-cavity).

Optical refrigeration cooling model

Enhancement of absorbed power

Findings

Conclusion