Ultrabroadband spectral beam combiner spanning over three octaves

We report the design, build, and test of a multispectral laser beam combining collimator with a spectral range in excess of three octaves. The device is based on a sapphire wedge prism, calcium fluoride, and sapphire collimating doublet lens and fiber optic inputs and is designed to operate from ultraviolet (355 nm) to mid-infrared (4075 nm) wavelengths. Five laser sources at different wavelengths were used to validate the concept. The device produced full-angle beam divergence of between 0.1 and 0.2 mrad from 355 to 1908 nm. The bore-sight error with respect to the design wavelength of 1064 nm was 0.07 mrad for 532 nm, 0.14 mrad for 355 and 1908 nm, and 2.4 mrad for 4075 nm. The results presented here represent, to the authors' knowledge, the widest spectral range of a laser beam combiner yet demonstrated.