SDL diode laser produces increased diffraction-limited output power at 635 nm
Researchers from SDL Inc. (San Jose, CA) demonstrated what they claim to be the first diffraction-limited continuous-wave (CW) output power of more than 400 mW at 635 nm in a flared unstable-resonator semiconductor laser. Previously, the diffraction-limited visible output-power levels have been about 30 mW, obtained in a narrow-stripe single-mode laser and limited by the high optical densities occurring at the laser facet. Broad-area devices reduce these optical densities but produce multimode output. The new device combines a narrow 4-µm-wide index-guided single-mode region with a flared gain-guided region--the width of this section increases linearly over the 1500-µm amplification region to 180 µm at the output aperture. The optical power density at the broad aperture is held well below the catastrophic optical damage limit while providing single-mode power levels on the order of hundreds of milliwatts. The researchers expect the laser will be appropriate for applications including high-density data storage, high-speed printing, displays, and solid-state laser pumps. Optical design of such systems, however, must accommodate the additional astigmatism of this source.