Pulse Shaping of Ultrashort Laser Pulses with Nonlinear Optical Crystals

We present a detailed description of the pulse shaping of ultrashort laser pulses with nonlinear optical crystals by introducing a time delay between two fundamental pulses. We demonstrate that the frequency reconversion process from a second-harmonic pulse to fundamental pulses will play an important role in fundamental pulse compression and train pulse generation. A collinear type II potassium dihydrogen phosphate (KDP) crystal can be used to achieve complete pulse shaping for a 1053 nm wavelength. Under conditions of a 50 GW/cm2 fundamental intensity, a 1.0 ps fundamental pulse duration and a 0.7 ps delay time, the second-harmonic pulse can be compressed to 0.14 ps. In addition, the fundamental pulse can be compressed to 0.3 ps by introducing an intensity unbalance into the two fundamental pulses. Furthermore, the train pulse can be generated by increasing the fundamental intensity over 20 GW/cm2. A train pulse with three 0.1 ps individual pulses with a 2.5 THz frequency interval can be generated for a 100 GW/cm2 fundamental intensity. We also demonstrate that pulse shaping with a noncollinear type I BBO crystal can be achieved at wavelengths near 800 nm.