Fabrication of Advanced Glass Light Pipes for Solar Concentrators

New applications for light pipes include waveguiding solar concentrators. For practical applications, achieving high optical transmission is critical so low-absorption glass is preferred over other materials, and the fabrication approach must show promise for scalability and low manufacturing costs. We present results for fabricated fused silica light pipes using femtosecond laser irradiation followed by chemical etching. After compensating for Fresnel losses and averaging over incident angles (in air) from 0 degrees to 25 degrees, transmission efficiencies of 96% and higher were measured for light pipes up to 20mm in length and 1mm(2) cross-sectional area. The feasibility of creating glass light pipes with advanced geometries such as angled facets, tapering of the cross-section along the length, and combiners with micron-scale precision is also demonstrated. Tapered light pipes with concentrating factors up to 7x were fabricated, as well as cascaded structures with 45 degrees-angled facets to couple light from multiple lens array elements into a common light pipe.