Investigation and optimization of continuum generation in crystals - white-light beyond sapphire

Focusing intense ultrashort laser pulses into transparent dielectric can lead to one of the most fascinating phenomena in ultrafast optics - white-light generation. The resulting femtosecond supercontinua are used for various applications such as transient spectroscopy, optical parametric amplification or carrier envelope phase measurements. The standard bulk material for white-light generation is sapphire, which allows the generation of a high quality single filament spanning from the blue to the NIR with modest input energy.This paper investigates the optimization of femtosecond continuum generation in single crystals of several common laser host materials. The absolute spectral energy density, pump threshold, pulse-to-pulse stability and beam profile are studied in dependence on the focal length, numerical aperture, crystal thickness, pump pulse energy and pump wavelength. Also, initialising processes for white-light generation like self-focusing, self-steepening and self-phase-modulation and their dynamic interaction are studied. From the three processes mentioned, it is confirmed that self-focusing is the process which triggers white-light generation.