Transmittance and phase matching of BBO crystal in the 3−5 μm range and its application for the characterization of mid-infrared laser pulses

Abstract

We uncover that thin (of few tens of μm thickness) BBO crystal exhibits reasonable transmittance and phase matching in the 3 − 5.2 μm range. We also provide refined dispersion equations of the ordinary and extraordinary refractive indexes for the 0.188 − 5.2 μm wavelength range, which were derived using an extended set of the refractive index values from direct measurements available in the literature and from indirect refractive index evaluation based on large collection of tuning curves provided by Light Conversion Ltd., and our own measurements of the sum-frequency mixing between the fundamental wavelength of Ti:sapphire laser and wavelength-tunable mid-infrared pulses. In particular, the uncovered mid-infrared features of BBO were exploited for the characterization of the ultrashort laser pulses at 4 μm and over an ultrabroad wavelength range, demonstrating simultaneous sum-frequency generation-based frequency-resolved optical gating of the signal and idler pulses from an optical parametric amplifier, and difference frequency pulse with central wavelengths of 1.3, 2.1 and 3.5 μm, respectively, using BBO crystal of 20 μm thickness.