Optimisation of power efficiency of (Ga Al)As injection lasers operating at high power levels

The overall power efficiency of semiconductor heterostructure lasers operating well above threshold has been calculated in terms of the power output per unit width P/W, the length l, the end reflectivity R, the absorption coefficient ¿¿ and the conductivity per unit area ¿¿. At currents sufficiently beyond threshold, the efficiency, optimised with respect to ¿¿l and R, depends only on the parameter (P/W) ¿¿/¿¿iE2g¿¿ where ¿¿i is the internal efficiency and Eg is the bandgap voltage. The form of this dependence and the range of reflectivity, laser length and power level for which it is applicable are derived. The results are compared with those which have been derived previously for lower relative power levels where optimum efficiency is obtained by operation reasonably close to threshold.