Abstract
Cascade pumping of type-I quantum well gain sections was utilized to increase output power and efficiency of GaSb-based diode lasers operating in a spectral region from 1.9 to 3.3 μm. Carrier recycling between quantum well gain stages was realized using band-to-band tunneling in GaSb/AlSb/InAs heterostructure complemented with optimized electron and hole injector regions. Coated devices with an ~100-μm-wide aperture and a 3-mm-long cavity demonstrated continuous wave (CW) output power of 1.96 W near 2 μm, 980 mW near 3 μm, 500 mW near 3.18 μm, and 360 mW near 3.25 μm at 17–20 °C—a nearly or more than twofold increase compared to previous state-of-the-art diode lasers. The utilization of the different quantum wells in the cascade laser heterostructure was demonstrated to yield wide gain lasers, as often desired for tunable laser spectroscopy. Double-step etching was utilized to minimize both the internal optical loss and the lateral current spreading penalties in narrow-ridge lasers. Narrow-ridge cascade diode lasers operate in a CW regime with ~100 mW of output power near and above 3 μm and above 150 mW near 2 μm.
Highlights
Cascade pumping originally proposed in [1] became recognized as a carrier delivery scheme leading to high-power room temperature continuous wave operation of semiconductor lasers utilizing gain sections based on electron transitions between subbands in the conduction band—quantum cascade lasers (QCLs) [2,3]—and interband transitions in the type-II quantum well—interband cascade lasers (ICLs) [4]
In multiple-quantum well (QW) diode lasers, the carrier transport considerations often dwarf a positive impact of an increased number of active QWs and, in certain cases, restrict the height of carrier localization barriers in individual QWs degrading temperature stability of laser parameters
Another benefit of cascade pumping includes the redistribution of the voltage drop across auxiliary layers of the laser heterostructure over multiple active regions, leading to improvement of the overall power conversion efficiency
Summary
Cascade pumping originally proposed in [1] became recognized as a carrier delivery scheme leading to high-power room temperature continuous wave operation of semiconductor lasers utilizing gain sections based on electron transitions between subbands in the conduction band—quantum cascade lasers (QCLs) [2,3]—and interband transitions in the type-II quantum well—interband cascade lasers (ICLs) [4]. In multiple-QW diode lasers, the carrier transport considerations (such as buildup of the transparency current and development of pumping inhomogeneity often causing the degradation of both differential gain and injection efficiency) often dwarf a positive impact of an increased number of active QWs and, in certain cases, restrict the height of carrier localization barriers in individual QWs degrading temperature stability of laser parameters. Another benefit of cascade pumping includes the redistribution of the voltage drop across auxiliary layers of the laser heterostructure over multiple active regions, leading to improvement of the overall power conversion efficiency. The utilization of series rather than parallel connection of the type-I QWs gain sections, i.e., their cascade pumping, should enhance the performance characteristics of diode lasers
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