Micro-integrated high-power infrared laser source for short-pulse pumping applications
Reaching high optical output powers at excellent beam qualities has always been a challenging objective in diode laser development. FBH successfully processes Bragg-grating-stabilized tapered diode lasers with reliable output powers in the watt range at high beam qualities . In order to address applications in the ten watt scale and beyond, a laser system was developed which is capable of almost loss free combination of two laser beams. The coupled radiation reaches optical output powers of more than 12 W in continuous wave mode at a wavelength of 980 nm. Furthermore, the high beam quality of the single emitters is maintained, achieving an output beam quality factor of M² < 1.5 in vertical as well as lateral dimension.
The polarization characteristics of the tapered laser beams were utilized to couple the laser beams inside the module. By rotating the polarization of one emitter, two beams can be combined using a thin film polarizer. The polarizer itself was adapted to withstand the high radiation intensities (>1 kW/cm²) and enable maximum coupling efficiency at the given wavelength of 980 nm. To ensure undisturbed performance of the single emitters, thermal simulations of the complete module were carried out. Based on the results, the mechanic-optical setup was optimized in order to avoid thermal crosstalk between the components. The complete setup was micro-integrated into an FBH-developed butterfly housing with a footprint as small as 76 x 54 x 15 mm³.
A key application for these laser modules is pumping of solid-state lasers for ultra-short pulses. The small size of the modules supports the compact integration into existing and newly developed systems. At the same time, the optical pumping geometries of solid-state lasers can be simplified. The high beam quality supports efficient pumping without the need for challenging beam shaping optics. Additionally, by thermal manipulation of the Bragg gratings, the emitted wavelength can be precisely tuned in a range of more than two nm to meet the exact absorption characteristics of the pumped medium. This concept is easily adaptable to tapered laser diodes of different wavelengths.
 B. Sumpf, K. Paschke, "Spectrally stabilized high-power high-brightness DBR-tapered lasers in the VIS and NIR range", Proc. SPIE 10518, Laser Resonators, Microresonators, and Beam Control XX, Photonics West, San Francisco, USA, Jan 27 - Feb 01, 1051817 (2018); DOI: doi.org/10.1117/12.2288425.