A Highly Efficient Hybrid Fiber Optic Laser Using a Cesium Atom Vapor Cell as an Optical Gain Medium

TL;DR

This paper presents a highly efficient hybrid fiber optic laser using a cesium vapor cell as an optical gain medium, achieving high slope efficiency and power output through an innovative cavity design.

Contribution

The study introduces a novel hybrid laser cavity scheme with a cesium vapor cell and demonstrates its high efficiency and power, highlighting the multifunctional role of the single mode fiber.

Findings

Achieved 86% slope efficiency and 419 mW continuous wave power.

Optimized pump beam waist and vapor cell temperature for maximum efficiency.

Demonstrated the fiber's multifunctional role in the hybrid cavity.

Abstract

A new scheme of a highly efficient hybrid laser cavity is proposed and experimentally demonstrated utilizing a hot cesium (Cs) vapor cell as an optical gain medium. The laser cavity consists of a macroscopic concave reflecting mirror (>99% reflectivity) and a 4% Fresnel-reflecting perpendicularly cleaved facet of a single mode fiber (SMF). The cylindrical cesium gain cell is located between these two reflectors. The SMF serves multiple roles: 1) a passive mode-matching component to approximate the pump beam diameter to that of the laser cavity mode within the cesium cell, 2) an output coupler with low reflectivity, and 3) a high beam-quality laser delivery with a low loss. Optimizing the pump beam waist diameter and the cesium vapor cell temperature, a high slope efficiency of 86% and continuous wave power of 419 mW were obtained in the pump power range of 400 to 600 mW, with an optical-to-optical conversion efficiency of 71%. The unique multi-functional role of the SMF in the hybrid cavity is fully described, and it can also be applied to other phases of high optical gain media.