Modeling and improving the output power of terahertz master-oscillator power-amplifier quantum cascade lasers

Abstract

A model based on carrier rate equations is proposed to evaluate the gain saturation and predict the dependence of the output power of a terahertz master-oscillator power-amplifier quantum cascade laser (THz-MOPA-QCL) on the material and structure parameters. The model reveals the design rules of the preamplifier and the power extractor to maximize the output power and the wall-plug efficiency. The correction of the model is verified by its agreement with the experiment results. The optimized MOPA devices exhibit single-mode emission at ∼ 2.6 THz with a side mode suppression ratio of 23 dB, a pulsed output power of 153 mW, a wall-plug efficiency of 0.22%, and a low divergence angle of ∼6°×16°, all measured at an operation temperature of 77 K. The model developed here is helpful for the design of MOPA devices and semiconductor optical amplifiers, in which the active region is based on intersubband transitions.

Independent Control of Mode Selection and Power Extraction in Terahertz Semiconductor Lasers

“…Notably, in the terahertz (THz) frequency range, the merging between the photonic and electronic concepts aroused a variety of novel cavity designs for high power single-mode terahertz quantum cascade lasers (THz-QCLs). − For example, the third-order distributed feedback THz-QCLs were proven to be promising for low-divergence beam emission and high power efficiency . Biasco et al demonstrated continuous-wave highly efficient low-divergence terahertz wire lasers .…”