A fully planar solar pumped laser based on a luminescent solar collector

A solar-pumped laser (SPL) that converts sunlight directly into a coherent and intense laser beam generally requires a large concentrating lens and precise solar tracking, thereby limiting its potential utility. Here, we demonstrate a fully-planar SPL without a lens or solar tracking. A Nd3+-doped silica fiber is coiled into a cylindrical chamber filled with a sensitizer solution, which acts as a luminescent solar collector. The body of the chamber is highly reflective while the top window is a dichroic mirror that transmits incoming sunlight and traps the fluorescence emitted by the sensitizer. The laser-oscillation threshold was reached at a natural sunlight illumination of 60% on the top window. Calculations indicated that a solar-to-laser power-conversion efficiency could eventually reach 8%. Such an SPL has potential applications in long-term renewable-energy storage or decentralised power supplies for electric vehicles and Internet-of-Things devices.