On the optimization of the gallium arsenide injection laser for maximum CW power output

A basic mathematical model of the injection laser is employed to investigate several questions dealing with the maximum obtainable power output and factors which impose practical limitations on it. With the aid of the rate equations for electron and photon densities and a simple model of thermal resistance, it is shown that there is an optimum value of diode area WL and of the parameter
S = \alphaL/\ln(1/R)
, which suggests that the CW power output can not be increased indefinitely with larger diodes. Rough numerical results are presented for CW operation at 77°K, assuming parabolic bands and band-to-band transitions without conservation of crystal momentum.