Optical Pumping Injection Cavity Lasers Toward High Power Conversion Efficiency at Room Temperature

摘要

To enhance the performance of antimonide-based optically pumped semiconductor lasers emitting in the mid-infrared, recent efforts have focused on increasing the absorption of pump photons in the active region. In the optical pumping injection cavity (OPIC) approach, the pump wavelength is tuned to the resonance of an etalon cavity surrounding the laser's active region. Previously, fixed wavelength sources have been used for optical pumping (e.g., 2.1 μm Ho:YAG laser, 1.85 μm diode pump array), which provides for only a limited amount of tuning through adjustment of the incident angle. In the present study of type-Ⅱ W OPIC lasers, a far more flexible tuning range is achieved by pumping with the idler beam from an optical parametric oscillator. Two OPIC samples were grown by molecular beam epitaxy on GaSb substrates. For Sample A (grown at Sarnoff), the 10-period W-active region was comprised of 21 A InAs/34 A GaSb/21 A InAs/40 A AlSb, surrounded by 100 A AlAs_(0.08)Sb_(0.92) hole blocking layers and 5213 A GaSb spacer layers. The top (10 period) and bottom (18.5 period) Bragg reflector mirrors were composed of alternating layers of 1758 A AlAs_(0.08)Sb_(0.92) and 1451 A GaSb. Sample B (grown at NRL) had an active region comprised of InAs/GaSb/InAs/digital alloy and was designed with a broadened cavity resonance, suitable for pumping with a multi-mode source. The epitaxial structure for both samples was designed for nominal 1.85-μm resonant optical pumping, with Sample A designed for epitaxial-side-up pumping and Sample B for epitaxial-side-down pumping.