Glass waveguides are fabricated using laser processing techniques that have low optical loss with >90% optical throughput. Advanced light pipes are demonstrated, including angled facets for turning mirrors used for lens-to-light pipe coupling, tapers that increase the concentration, and couplers for combining the outputs from multiple lens array elements. Because they are fabricated from glass, these light pipes can support large optical concentrations and propagate broadband solar over long distances with minimal loss and degradation compared to polymer waveguides. Applications include waveguiding solar concentrators using multi-junction PV cells, solar thermal applications and remoting solar energy, such as for daylighting. Ray trace simulations are used to estimate the surface smoothness required to achieve low loss. Optical measurements for fabricated light pipes are reported for use in waveguiding solar concentrator architectures.
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° to 25°, transmission efficiencies of 96% and higher were measured for light pipes up to 20mm in length and 1mm2 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°-angled facets to couple light from multiple lens array elements into a common light pipe.