TEMPORAL AND SPECTRAL ANALYSIS FOR MID-INFRARED FOUR-WAVE MIXING IN QUANTUM INTERSUBBAND STRUCTURE

We design a quantum cascade (QC) intersubband structure for four-wave mixing (FWM) generation from In0.53Ga0.47As/In0.52Al0.48As in the mid-infrared spectral region which can be described by third-order nonlinear optical susceptibility. In this structure, increasing FWM is accomplished by band engineering which modify energy of subbands. To analyze FWM characteristics in a QC structure, the evolution in time and spectral domain of pump and probe input optical pulses with different frequencies during propagation is calculated and simulated by using finite-difference beam propagation method. Central frequencies of pump and probe pulses which are used for driving the amplifier are 37.97 THz and 32.61 THz, respectively. Third order susceptibility responsible for FWM resonance nonlinearity of the structure is enhanced by two orders of magnitude. As power of input pulses rises, the value of the FWM output signal increases but the pulse loses its initial shape. Gain saturation and dispersion play a major role in shaping the output pulse. Results reveal that the FWM optical pulse characteristics are highly sensitive to the pulse power and QC parameters in the time and frequency domains.