TITLE:
Beam Parameter Product Optimization for High Power SWIR Laser Diode Stack Fiber Coupling
AUTHORS:
Yves Lutz
KEYWORDS:
Semiconductor Laser, Beam Shaping, Beam Parameter Product, Spatial Multiplexing, Polarization Coupling, Laser Illuminator
JOURNAL NAME:
Optics and Photonics Journal,
Vol.12 No.2,
February
28,
2022
ABSTRACT: An optimized setup for fiber optic injection of a kilowatt peak power laser diode stack emitting in the SWIR spectral range is proposed. Starting from a fast axis collimated (FAC) and slow axis collimated (SAC) 15 bars, 19 emitters off the shelf laser diode stack, the beam is transformed using spatial beam combining and polarization coupling. Both techniques integrated in a compact design enable to couple the kilowatt level beam into a standard 600 μm core, 0.22 numerical aperture (NA) multimode optical fiber. An application in the field of long range SWIR laser illuminator for gated viewing is presented. A comparison between two illuminators is realized both based on the same laser diode stack but one using beam parameter product (BPP) reduction and one without. It could be demonstrated that BPP reduction is the best way for efficient, narrow divergence and compact semi-conductor based laser illuminators design and realization. The global laser illuminator efficiency could be improved by 75% for the narrowest divergences thanks to this approach.