Abstract

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_s≈λ_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 biréfringent nonlinear crystals like BBO, most often used for ultrabroadband OPA [1], the second condition is simultaneously fulfilled at pump wavelengths λ_P far from the 800 mil spectral range, in which high-power femtosecond Tksapphire laser systems operate with high stability at kHz repetition rates.

© 2007 IEEE