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We present our recent efforts to improve power rating, efficiency, reliability, and cost of diode laser bars in the 88x nm wavelength band. QCW kW-class diode laser bars are grown by metal-organic chemical vapor deposition (MOCVD), and are cleaved, passivated, coated, and die bonded onto either standard copper CS-style heat sinks using indium solder, or onto expansion matched CuW CS heat sinks using AuSn solder. In an effort to realize high power operation, the high efficiency 880-nm epitaxial design has been optimized. Bars of varying fill factors, cavity lengths, and facet coating reflectivities are explored to improve the rated electrical to optical (E-O) efficiency up to approximately 70% under low duty cycle QCW operations. The enhanced E-O efficiency makes possible not only the passive cooling of the devices, but also reliable operation in the kW power range. We demonstrate that the semiconductor laser bars can survive over 100 million laser shots working in QCW mode. It is expected that the development of these passively cooled, highly efficient and highly reliable QCW kW-class diode laser bars will enable commercial applications.

Surface-emitting distributed feedback (SE-DFB) diode lasers possess many advantages compared to edge emitters, in terms of power, brightness and spectral characteristics. We have demonstrated 312 W and 68 W of peak power at 1-s pulse duration and 100-Hz repetition rate from single 97x nm SE-DFB laser chips with electrically-pumped stripe of 3.75 mm2and 0.18 mm2respectively, achieving a power density of 378 W/mm2. Under the same pulsing condition, we have also demonstrated current-limited 206 W of peak power out of a 100 m / 0.22 NA fiber with only two 2x1 chiplevel SE-DFB laser arrays.

We report on our progress to obtaining a 1540 nm SE-DFB laser with curved, second order grating capable of producing extremely high peak power for eye-safe range finding applications. Higher peak power can be extracted from SE-DFB lasers since the emission area is three orders of magnitude larger than for edge emitters. Ten-times narrower spectral width and four-times lower thermal shift of emission wavelength allows for the use of narrower filters on the range finder detector, providing a higher signal-to-noise ratio. Furthermore, a curved second-order diffraction grating in our SE-DFB laser allows for a higher brightness source, which makes transmitter optics geometry more compact and simpler.