Search Results (8)

In this paper, we present a beam-combining technique to boost GaSb-based 1940 nm diode laser output power through spectral beam combining (SBC), spatial beam combining, and polarization beam combining (PBC). Four spectral beam-combining (SBC) configurations were developed using commercially available standard bars. The four SBC configurations were paired to perform PBC after spatial beam combining. The total output power of the 1940 nm laser reached 23.4 W, with the beam qualities of the combined beam achieving 10.6 in the slow axis and 11 in the fast axis. The brightness of the combined laser reached 5.4 MW·cm⁻²·sr⁻¹. Full article

Antimonide laser diodes, with their high performance above room temperature, exhibit significant potential for widespread applications in the mid-infrared spectral region. However, the laser’s performance significantly degrades as the emission wavelength increases, primarily due to severe quantum-well hole leakage and significant non-radiative recombination. In this paper, we put up an active region with a high valence band offset and excellent crystalline quality with high luminescence to improve the laser’s performance. The miscibility gap of the InGaAsSb alloy was systematically investigated by calculating the critical temperatures based on the delta lattice parameter model. As the calculation results show, In_0.54Ga_0.46As_0.23Sb_0.77, with a compressive strain of 1.74%, used as the quantum well, is out of the miscibility gap with no spinodal decomposition. The quantum wells exhibit high crystalline quality, as evidenced by distinct satellite peaks in XRD curves with a full width at half maximum (FWHM) of 56 arcseconds for the zeroth-order peak, a smooth surface with a root mean square (RMS) roughness of 0.19 nm, room-temperature photoluminescence with high luminous efficiency and narrow FHWM of 35 meV, and well-defined interfaces. These attributes effectively suppress non-radiative recombination, thereby enhancing internal quantum efficiency in the antimonide laser. Furthermore, a novel epitaxial laser structure was designed to acquire low optical absorption loss by decreasing the optical confinement factor in the cladding layer and implementing gradient doping in the p-type cladding layer. The continuous-wave output power of 310 mW was obtained at an injection current of 4.6 A and a heatsink temperature of 15 °C from a 1500 × 100 μm² single emitter. The external quantum efficiency of 53% was calculated with a slope efficiency of 0.226 W/A considering both of the uncoated facets. More importantly, the lasing wavelength of our laser exhibited a significant blue shift from 3.4 μm to 2.9 μm, which agrees with our calculated results when modeling the interdiffusion process in a quantum well. Therefore, the interdiffusion process must be considered for proper design and epitaxy to achieve mid-infrared high-power and high-efficiency antimonide laser diodes. Full article

We reported on a single-longitudinal-mode operated distributed Bragg reflector laser diode emitting at 1950 nm with an on-chip integrated power amplifier. Second-order Chromium–Bragg gratings are carefully designed and fabricated at the end of the ridge waveguide. Achieving a stable single-mode operation with a large injecting current range of 800 mA from 15 °C to 40 °C. The maximum side-mode suppression ratio (SMSR) is up to 42 dB. To increase the output power, an on-chip integrated master oscillator power amplifier (MOPA) is also introduced. MOPA-DBR lasers with different matching configurations between the gain peak and Bragg wavelength are fabricated, resulting in various amplification consequences. The best device is realized with 40 nm red-shifted between Bragg wavelength and photoluminescence (PL) peak. A power amplification of 5.6 times is achieved with the maximum output power of 45 mW. Thus, we put up the feasibility and key design parameters of on-chip integrated power amplification DBR lasers towards mid-infrared. Full article

We propose a novel graded AlGaAsSb layer growth method to achieve a super-linear interface by precisely controlling the cell temperature and valve position. Atomically smooth surface and lattice-matched epitaxy was confirmed by AFM and the HRXRD characterization of the graded AlGaAsSb layer sample. With the inserted graded layer between the cladding and waveguide layers, high-power, high-efficiency GaSb-based laser emitters and laser bars were confirmed. The linearly graded interface layer smooths the potential barrier peak between the cladding and waveguide layers, which resulted in a low turn-on voltage of 0.65 V and an ultra-low series resistance of 0.144 Ω. A maximum continuous-wave output power of 1.8 W was obtained with a high power conversion efficiency of 28% at 1.1 A and 12% at 8 A. A facet-coated laser bar was also fabricated with a record-high CW output power of 18 W. A high internal quantum efficiency of 83 was maintained at 40 °C, implying improved carrier injection efficiency, which benefits from the built-in electric field of the composition-graded AlGaAsSb layer. Full article

Symmetric narrow waveguide structure has been developed and fabricated to achieve low beam divergence and improved coupling performance of the 1.95 μm GaSb-based single-transverse-mode diode lasers. The near-field expansion effect of the narrowed 150 nm vertical waveguide design leads to a reduced fast-axis beam divergence of 44.2° full width at half maximum (FWHM) as well as 62% single-mode fiber (SMF) coupling efficiency, which has 55% relative promotion compared to the 40% efficiency of the conventional 270 nm waveguide design with 60.4° FWHM. The highest SMF coupling power of 113 mW was obtained by the 210 nm narrow waveguide lasers with lower internal optical loss at a 55% coupling efficiency, which performed balanced optimal performance with a narrowed divergence of 53.4° and a relatively high optical power of 206 mW. The high coupling efficiency and power will provide more promising prospects for the GaSb-based single-transverse-mode lasers in the widespread fiber-based and external-cavity applications. Full article

The epitaxial deposition of a precise number, or even fractions, of monolayers of indium (In)-rich semiconductors onto gallium arsenide (GaAs) substrates enables the creation of quantum dots based on InAs, InGaAs and indium phosphide (InP) for infrared light-emitting and laser diodes and the formation of indium antimonide (InSb)/GaAs strained layer superlattices. Here, a facile method based on energy-dispersive X-ray spectroscopy (EDXS) in a scanning electron microscope (SEM) is presented that allows the indium content of a single semiconductor layer deposited on a gallium arsenide substrate to be measured with relatively high accuracy (±0.7 monolayers). As the procedure works in top-down geometry, where any part of a wafer can be inspected, measuring the In content of the surface layer in one location without destroying it can also be used to map the lateral indium distribution during quantum dot formation and is a method suitable as an in-situ quality control tool for epitaxy. Full article

The optical gain spectrum has been investigated theoretically for various designs of active region based on InAs/GaInSb quantum wells—i.e., a type II material system employable in interband cascade lasers (ICLs) or optical amplifiers operating in the mid-infrared spectral range. The electronic properties and optical responses have been calculated using the eight-band k·p theory, including strain and external electric fields, to simulate the realistic conditions occurring in operational devices. The results show that intentionally introducing a slight nonuniformity between two subsequent stages of a cascaded device via the properly engineered modification of the type II quantum wells of the active area offers the possibility to significantly broaden the gain function. A −3 dB gain width of 1 µm can be reached in the 3–5 µm range, which is almost an order of magnitude larger than that of any previously reported ICLs. This is a property strongly demanded in many gas-sensing or free-space communication applications, and it opens a way for a new generation of devices in the mid-infrared range, such as broadly tunable single-mode lasers, mode-locked lasers for laser-based spectrometers, and optical amplifiers or superluminescent diodes which do not exist beyond 3 µm yet. Full article

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. Full article