We present recent development of single lateral mode 1050 nm laser bars. The devices are based on an InGaAs/AlGaAs single quantum well and an asymmetric large optical cavity waveguide structure. By optimizing the AlGaAs composition, doping profiles, and QW thickness, the low internal loss of 0.5 cm-1 and high internal quantum efficiency of 98% are obtained. A standard bar (10% fill factor; 4mm cavity length) reaches 72% peak electro-optical efficiency and 1.0 W/A slope efficiency at 25°C. To achieve high single lateral mode power, the current confinement and optical loss profile in lateral direction are carefully designed and optimized to suppress higher order lateral modes. We demonstrate 1.5W single lateral mode power per emitter from a 19-emitter 10mm bar at 25°C. High electro-optical efficiency are also demonstrated at 25°C from two separate full-bar geometries on conduction cooled packaging: 20 W with <50% electro-optical efficiency from a 19-emitter bar and 50 W with <45% electro-optical efficiency from a 50-emitter bar.
KEYWORDS: Semiconductor lasers, High power diode lasers, Reliability, High power lasers, Solid state lasers, Solid state electronics, Fiber lasers, Diodes, Materials processing, Printing, Data conversion, Fiber couplers
Key applications for 780-830nm high power diode lasers include the pumping of various gas, solid state, and fiber laser media; medical and aesthetic applications including hair removal; direct diode materials processing; and computer-to-plate (CtP) printing. Many of these applications require high brightness fiber coupled beam delivery, in turn requiring high brightness optical output at the bar and chip level. Many require multiple bars per system, with aggregate powers on the order of kWs, placing a premium on high power and high power conversion efficiency. This paper presents Coherent’s recent advances in the production of high power, high brightness, high efficiency bars and chips at 780-830nm. Results are presented for bars and single emitters of various geometries. Performance data is presented demonstrating peak power conversion efficiencies of 63% in CW mode. Reliability data is presented demonstrating <50k hours lifetime for products including 60W 18% fill factor and 80W 28% fill factor conduction cooled bars, and <1e9 shots lifetime for 500W QCW bars.
We present kW QCW vertical and horizontal arrays composed of 200W bars (peak power) at 8xxnm wavelength. We
also present an unique Bar-on-Submount design using the electrically insulating submounts, which can provide a
platform for simple and flexible horizontal array construction. The p-n junction temperature of the arrays under QCW
operation is modeled with FEA software, as well as measured in this research. Updated reliability test results for these
kW arrays will be also reported. As the examples, we present the performance of the vertical arrays with > 57% Wall-Plug-Efficiency and the horizontal arrays with < 23 degree fast axis divergence (FWHM), both with 808nm wavelength.
The available wavelength for such arrays ranges from 780nm to beyond 1 um. Coherent also have the capability to
produce the array with wide and relatively uniform spectrum for athermal pumping of solid-state lasers, by integrating
diode lasers bars with different wavelength into single array.
We present the reliability of high-power laser diodes utilizing hard solder (AuSn) on a conduction-cooled package
(HCCP). We present results of 50 W hard-pulse operation at 8xx nm and demonstrate a reliability of MTTF > 27 khrs
(90% CL), which is an order of magnitude improvement over traditional packaging. We also present results at 9xx nm
with a reliability of MTTF >17 khrs (90% CL) at 75 W. We discuss finite element analysis (FEA) modeling and time
dependent temperature measurements combined with experimental life-test data to quantify true hard-pulse operation.
We also discuss FEA and measured stress profiles across laser bars comparing soft and hard solder packaging.
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