100 THz bandwidth of optical parametric amplification in the near-IR using bismuth triborate crystals pumped at 800 nm

摘要

The concept of ultrabroadband (more than one octave) coherent amplification relies on optical parametric amplification (OPA) at achromatic phase-matching condition defined by zero group velocity mismatch (GVM) between the idler and signal pulses. In the case of a collinear type-I interaction, this condition is always fulfilled near the degeneracy wavelengths (λ{sub}S≈λ{sub}I), but the bandwidth can be further enhanced if the group velocity dispersion (GVD) of the signal and idler waves also vanishes. In this case the gain bandwidth can reach an octave value and it is determined by the fourth derivative of the wave vector mismatch with respect to frequency, at the phase matching point. Unfortunately, in birefringent nonlinear crystals like BBO, most often used for ultrabroadband OPA [1], the second condition is simultaneously fulfilled at pump wavelengths λ{sub}p far from the 800 nm spectral range, in which high-power femtosecond Ti:sapphire laser systems operate with high stability at kHz repetition rates.