Particle Swarm Optimization approach to identify optimum electrical pulse characteristics for efficient Gain Switching in Dual Wavelength Quantum Cascade Lasers

Numerical simulation of Gain Switching in Dual Wavelength QCLs (DW-QCLs) for short pulse generation in the mid-Infrared region is reported. A four-level rate equation model is used to investigate the QCL which consists of 48 periods of injector and active regions, emitting at 10.5 μm and 8.9 μm. The device is simulated for various inputs such as square, haversine and tangential hyperbolic electrical pulses. The optimum parameters of electrical pulse pertaining to generation of short pulses with maximum power and minimum pulse width for single wavelength and simultaneously at both wavelengths are determined using Particle Swarm Optimization (PSO) technique. The physical nature of drive current and its time period dictates the duration and peak power in both the wavelengths. It is found that square pulse of amplitude 11.12 mA and 0.1 ns produces short optical pulses of width 15.89 ps with peak power of 2.2 mW at 10.5 μm. Similarly, short optical pulses with peak power 1.8 mW and width 15.92 ps are generated by square pulse of amplitude 13.12 mA at 8.9 μm. It is also observed that tangential hyperbolic pulse of amplitude 10.79 mA and 8.47 mA produces short optical pulses with equal power and equal pulse width respectively in both the wavelengths at 0.1 ns.