Wavelength-Stabilized Multi-Active Region DBR and DFB Broad-Area and Ridge-Waveguide Lasers for High Peak-Power Pulsed Operation

For LiDAR applications, compact, robust, and mass-producible light sources generating high-peak power nanosecond-long pulses are essential. This paper presents an investigation of power scaling in semiconductor lasers via the number of epitaxially stacked active regions in a single vertical waveguide supporting a higher order mode, chip length, output aperture width, and lateral waveguide design. All devices are wavelength-stabilized using surface gratings integrated either as a passive section at the rear facet of the diode laser as a distributed-Bragg-reflector (DBR) or along the full length of the chip in a distributed feedback (DFB) design. A 4 mm long broad-area (BA) DBR laser with a stripe width of 200 μm and five active regions delivered approximately 171 W at 80 A, a factor of 6.6 more peak pulse power than the standard 6 mm long single active region DBR laser with 50 μm stripe width. A corresponding 3 mm long 3-active region DFB-BA laser achieved more than 125 W at 129 A. These BA lasers have a lateral beam propagation ratio M<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}\approx$</tex-math></inline-formula> 30. In contrast, weakly tapered ridge waveguide (TRW) lasers were found to generate more than 20 W with an M<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> of about 3 and an excellent lateral brightness of 24 W<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula> mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-1}$</tex-math></inline-formula>mrad<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-1}$</tex-math></inline-formula>.