High-efficiency and economical solar-energy-pumped laser with Fresnel lens and chromium codoped laser medium

The authors achieved 11%–14% slope efficiency of solar-pumped laser by Cr-codoped Nd:yttrium aluminum garnet ceramic and Fresnel lens focusing from natural sunlight. The laser output of 24.4W was achieved with 1.3m2 Fresnel lens. The maximum output for unit area of sunlight was 18.7W∕m2, which is 2.8 times larger than previous results with mirror collector. The utilization of Cr3+ ion enabled efficient absorption and energy transfer to Nd3+ ion of solar spectrum. The fluorescence yield at 1064nm for various pumping wavelengths was measured both for Crcodoped and nondoped laser media, and 1.8 times enhancement of laser output from sunlight is predicted.