Femtosecond laser-written high-efficiency blazed phase gratings in the volume of soda lime glass for light management in solar modules

Highly efficient volume phase gratings have been fabricated in low-iron soda lime glass using femtosecond (fs) laser pulses with 1030 nm wavelength and 270 fs pulse duration. Optical simulations based on rigorous coupled-wave analysis theory were performed to determine optimal grating parameters and designs for the application of the gratings for light management in solar modules, suggesting a very effective blazed-like design. Several of such blazed phase gratings have been fabricated and analyzed by measuring their diffraction efficiencies into first and higher orders. Up to 77% of the incoming light in the wavelength region relevant for silicon-based photovoltaics were diffracted by these gratings. Typical induced refractive index changes between 0.002 and 0.006 were derived by comparing the experimental efficiencies with the simulation results.