Design considerations and analytical approximations for high continuous-wave power, broad-waveguide diode lasers

Accurate analytical approximations are derived for the equivalent transvers e spot size, d/Gamma (<5% error), and the transverse beamwidth theta(1/2) ( <2% error), of broad-waveguide-type diode lasers, over a wide range in wave guide width: from the first-order-mode cutoff to the third-order-mode cutof f. The analytical formulas are found to be in good agreement with experimen tal values. For low-series-resistance and thermal-resistance devices, it is found that the junction-temperature rise Delta T-j in continuous wave (CW) operation is a strong function of both the characteristic temperature T-1 for the external differential quantum efficiency eta(D) as well as of the h eatsink thermal resistance. If the device has relatively temperature-insens itive eta(D) (i.e., T1 greater than or similar to 1000 K) the maximum CW po wer as well as the power density at catastrophic optical mirror damage, (P) over bar(COMD), are limited, for a given active-region material, only by t he heatsink heat-removal ability. For large d/Gamma, 0.97 mu m emitting, 10 0 mu m stripe InGaAs/InGaAs(P)/GaAs devices with T-1 = 1800 K, record-high CW and quasi-CW (100 mu s wide pulses) output powers are obtained. The rati o of quasi-CW to CW (P) over bar(COMD) values is only 1.3, in contrast to d evices of poor carrier confinement and subsequent low-T-1 values (similar t o 140 K), for which the ratio is 1.9, and whose maximum CW powers are simil ar to 40% less than those obtainable from high-T-1 devices. (C) 1999 Americ an Institute of Physics. [S0003-6951(99)03421-X].