Transversely pumped solar Nd3+-doped fiber laser

Abstract In order to improve the coupling efficiency of solar fiber lasers, a new kind of transversely pumping geometry is proposed. A two-stage concentration system is designed to concentrate the sunlight into the Nd-doped fiber coiled in a ring chamber with high-reflective inner surfaces. The primary concentrator is an off-axis Fresnel lens with a radius of 600 mm, and the secondary concentrator is a compound parabolic optical waveguide. With this concentration configuration, the collection efficiency can be as high as 21.4%. 73.5 W solar power is absorbed by the fiber core according to ray-tracing simulation. Output characteristics of the solar fiber laser are further analyzed by calculating the rate equations. 2.6 W laser output is obtained and the slope efficiency reaches 3.7%.