Study On Near-infrared Broadband Femtosecond Optical Parametric Amplification In BBO Crystal

Femtosecend optical parametric amplification (OPA) is an important tunable device for producing ultashort pulses for its large gain and broad gain bandwidth. Recently, pulses with 4fs duration have been generated by noncollinear phase-matched optical parametric amplifier pumped by 400nm in BBO crystal in the visible spectral range. However, it is impossible to obtain an amplified near-infrared signal with sub-10fs duration. In this dissertation,the usage of achromatic phase matching in femtosecend OPA for obtaining amplified near-infrared signal pulses with broad bandwidth is studied, which found a base to produce pulses with sub-10fs duration in the whole spectral range from the visible to the near-infrared .The main contents of this dissertation are listed below:1. The theory of femtosecend OPA is reviewed.The coupled equations are derived from Maxwell's equations. The signal and idler intensities, the parametric gain are solved .The properties of nonlinear crystal BBO is presented. The walk-off angle and the spatial walk-off effect, the group velocity mismatch and the temporal walk-off effect are discussed.2. The spectral bandwidth of noncollinear phase-matched optical parametric amplification (NOPA) is theoretical studied. Broadband phase matching conditions of the NOPA have been given both in the visible and the infrared spectral range. The effects of noncollinear angle and angularly dispersion of signal pulse on the phase-mismatch, the gain and the parametric bandwidth are studied. A new method is presented to choose the optimized noncollinear angle and angularly dispersion for visible and near-infrared OPA. As an example, the optimized parameters to obtain the broadest bandwidth in the NOPA pumped by the blue light of 400nm in BBO crystal are found both in the he visible and near-infrared spectral range.3. The experience of near-infrared type-Ⅰphase-matched femtosecond NOPA is studied. The parametric superfluorescence is obtained.The amplified near-infrared signal beam continuously tunable from 800 nm to 1050 nm is obtained. The broadest gain bandwidth of the signal is 42 nm and also the duration of the pulses supported by some bandwidth can be less than 20fs .And the signal pulse energy is 0. 3μJ and the conversion efficiency is greater than 2%.4. The improved design of near-infrared femtosecend OPA is reported. The two...