The energy levels, wave functions and the second-order nonlinear susceptibilities are calculated in GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As asymmetric quantum well (AQW) by using an asymmetric model based on the parabolic and non-parabolic band. The influence of non-parabolicity can not be neglected when analyzing the phenomena in narrow quantum wells and in higher lying subband edges in wider wells. The numerical results show that under double resonance (DR) conditions, the second-order difference frequency generation (DFG) and optical rectification (OR) generation susceptibilities in the AQW reach 2.5019 mm/V and 13.208 mm/V, respectively, which are much larger than those of the bulk GaAs. Besides, we calculate the absorption coefficient of AQW and find out the two pump wavelengths correspond to the maximum absorption, so appropriate pump beams must be selected to generate terahertz (THz) radiation by DFG.
A low-threshold efficient high-repetition-rate eye-safe optical parametric oscillator(OPO) is presented.The OPO is based on an x-cut non-critically phase-matched(NCPM) KTA intra-cavity pumped by an acousto-optically(A-O) Q-switched Nd:YVO4 laser.At 10 kHz,the lowest threshold of 0.75 W and the signal power of 0.6 W are got,corresponding to the single pulse energy of 60 μJ and the peak power of 20 kW.Tuning the frequency,the maximum output power at 1536 nm is 1.03 W at 30 kHz with an optical-to-optical conversion efficiency of 12.26%.The fluctuation of the output power is 2.1% during 2 h operation.
