We present weakly tapered ridge waveguide distributed Bragg reflector lasers with three active regions epitaxially stacked in a common waveguide emitting nanosecond pulses around 905nm for LIDAR. The vertical structure is optimized for pulsed operation and implementation of a surface Bragg grating for emission in the 2nd order vertical mode. 6mm long diode lasers with a 25μm output aperture, integrated in an inhouse high pulse current electronic driver, provide a pulse power ⪆20W, a beam propagation ratio M2~4.5, and a brightness of ~16W(mm mrad). The emission spectrum features a spectral bandwidth of ⪅0.3nm and a temperature-related shift of ⪅70pm/K.
Diode lasers providing nanosecond high power optical pulses are key components for light detection and ranging (LiDAR) systems used for, e.g., distance measurements. For autonomous vehicles, good beam quality is an important aspect to achieve the required high spatial resolution. While 30 μm broad area devices can achieve pulse powers >20 W emitting at 905 nm, the beam quality factor M2 is about ten and further degrades with increasing stripe width. Tapered-Ridge-Waveguide (TRW) lasers with 23 μm wide output apertures reduced the M2 to about 2.2 without power loss. However, deployment of such lasers also requires a low temperature-dependent wavelength shift allowing for narrowband spectral filters. Here, we present TRW Distributed Bragg Reflector (DBR) lasers with a 23 μm wide output aperture. For emission around 905 nm the active region comprises an InGaAs single quantum well embedded in an AlGaAs waveguide. A surface Bragg grating is implemented into an unpumped section of the device enabling a wavelength shift of only 0.07 nm/K. The electrical interface realized by a nanosecond pulse driver developed in-house delivers pulse currents up to some 10 A within 2 ns to 5 ns pulses at 10 kHz. We investigate different designs of the trenches etched to define the ridge-waveguide. Beam quality factors of about three are achieved at pulse powers of about 10 W. Experimental results on the optical power, the near and far field profiles, and spectral characteristics are presented. Integration into an electrical driver module allows for reliability tests on an application relevant testbed.
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