Optical pumping injection cavity (OPIC) for high-efficiency mid-IR “W” lasers

We report a new optical pumping injection cavity (OPIC) approach that combines a high pump absorbance with long pump wavelength and a thin active layer. High absorbance is achieved by tuning an etalon cavity to the pump wavelength, which brings about multiple passes of the pump beam through the active region. A 12-½ period distributed Bragg reflector (DBR) consisting of alternating AlAs_0.08Sb _0.92 and GaSb layers was grown onto the GaSb substrate. The 2λ_pump central cavity consisted of a 0.51 μm thick GaSb spacer, a 100 Å AlAs_0.08Sb_0.92 hole-blocking layer, a l0-period InAs/GaSb/InAs/AlAsSb (17 Å/35 Å/17 Å/44 Å) W active region, another hole-blocking layer, and another spacer. The OPIC pump cavity was completed by a 7-period top GaSb/AlAsSb DBR. Although the OPIC is resonant in the vertical direction at λ_pump, at the mid-IR wavelength, the mirror stacks function as cladding layers and the spacers function as high-index separate confinement regions. Thus the laser operates in an edge-emitting configuration. Pumping was by 107 ns pulses from a 2.098 μm Ho:YAG laser, operating at a repetition rate of 1 Hz