We present broad area distributed Bragg reflector lasers with up to five active regions epitaxially stacked in a common waveguide emitting nanosecond pulses around 905nm for LIDAR. Optimized for pulsed operation and implementation of a surface Bragg grating, the diode laser emits in a higher order vertical mode. 2mm long diode lasers with five active regions and a 200µm wide current aperture integrated in an inhouse high pulse current electronic driver provide pulse powers >200W at slightly >100A in 10ns long pulses. The emission spectrum features a spectral bandwidth of <0.3nm and a temperature-related shift of <70pm/K.
KEYWORDS: Pulsed laser operation, Laser bars, Laser stabilization, Semiconductor lasers, LIDAR, Near field optics, Active optics, Near field, Blue lasers, Waveguides
Diode lasers providing nanosecond long optical pulses are key components for light detection and ranging (LiDAR) systems employed in, e.g., autonomous vehicles. However, achieving high resolution at large distances in real world scenarios remains a challenge due to the high currents required for high pulse powers. To reduce the currents needed, several laser diodes, separated by tunnel junctions, can be epitaxially stacked in series. Here, we present a 4 mm long laser with a stripe width of 50 μm comprising three InGaAs quantum wells and two GaAs tunnel junctions placed in the antinodes and nodes of the 2nd order vertical mode, respectively, to realize a shared optical waveguide. 1 mm long surface Bragg gratings stabilize the emission wavelength. Implemented in a 48-emitter laser bar soldered p-side down on a CuW submount and integrated in an inhouse developed electronic driver providing pulse currents up to 1 kA in a few nanoseconds, pulse powers exceeding 2 kW are achieved in 8 ns long pulses at a 10 kHz rate. Comparison with a similar module using a laser bar with a single active region shows a threefold increase of pulse power. The optical spectrum of the laser bar with a peak wavelength around 910 nm features a spectral bandwidth of only about 0.3 nm (3 dBc) and a wavelength shift with temperature of only 0.07 nm/K which is the same as what was achieved with single active regions. Results of reliability tests show no degradation of performance for more than 6000 h.
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