Experimental results of aging and thermal effects in high-power laser diodes

This paper describes the aging and thermal effects of high-power GaAlAs laser diodes constructed by Spectra Diode Laboratory (SDL) with multiple stripes, containing single- and multiple-quantum wells. Thermal effects are described for laser diodes constructed by McDonnell Douglas Astronautics Company/Optoelectronics Center (MDAC/OEC) with a single broad stripe containing a single-quantum well. The laser diodes are grown using metalorganic chemical vapor deposition (MOCVD). Experimental data are given showing the aging and thermal effects of these laser diodes while operating CW for different on-times and operating up to 2.0 W for an overdriven SDL commercial laser diode, 4.0 W for a SDL engineering prototype and 5.0 W for a MDAC/OEC prototype. Thermal effects are observed by operating at different intervals between shots and power levels when cooled by a fin heat-sink or thermoelectric cooler. Aging is caused by operating the laser diodes at elevated optical power levels. The characteristics used to describe these effects include: (1) optical power versus current, (2) efficiency versus optical power, (3) beam intensity distribution and (4) divergence. Laser diode output powers decreased by 2.5 percent to 22 percent because of aging. The different cooling methods resulted in a difference in output power of 7 percent.