Spectral flattening of supercontinua with a spatial light modulator

Abstract

We demonstrate the generation of broad spectra with a flat intensity distribution from originally highly structured supercontinua, obtained with femtosecond pulses in a photonic crystal fiber. This is accomplished by truncating the spectra at a constant level using a liquid crystal based spatial light modulator. The technique is useful for astronomical spectrograph calibration using frequency combs, where it allows to equalize the optical power of the calibration lines. This enables an improved calibration accuracy by maximizing each line’s signal-to-noise ratio.