Power scaling in conventional broad-area (BA) lasers often leads to the operation of higher-order lateral modes, resulting in a multiple-lobe far-field profile with large divergence. Here, we report an advanced sawtooth waveguide (ASW) structure integrated onto a wide ridge waveguide. It strategically enhances the loss difference between higher-order modes and the fundamental mode, thereby facilitating high-power narrow-beam emission. Both optical simulations and experimental results illustrate the significant increase in additional scattering loss of the higher-order modes. The optimized ASW lasers achieve an impressive output power of 1.1 W at 4.6 A at room temperature, accompanied by a minimal full width at half maximum lateral divergence angle of 4.91°. Notably, the far-field divergence is reduced from 19.61° to 11.39° at the saturation current, showcasing a remarkable 42% improvement compared to conventional BA lasers. Moreover, the current dependence of divergence has been effectively improved by 38%, further confirming the consistent and effective lateral mode control capability offered by our design.

We report on a GaSb-based superluminescent diode optimized for high-power broadband operation around a wavelength of 2 μm. The high optical power was achieved by the high-quality epitaxial InGaSb/AlGaAsSb type-I quantum well gain material, which was processed into a double-pass amplification configuration. To prevent lasing at high current injection while enabling strong amplified spontaneous emission, a cascade cavity suppression waveguide geometry was designed to connect the vertical rear facet with the reflectivity-suppressed angled front facet. A Ta2O5/SiO2 ultra-low antireflection coating with a minimum reflectivity of 0.04% was applied to the front facet for further cavity suppression. This combination allowed the superluminescent diodes to demonstrate a record high single-transverse-mode output power of up to 152 mW under continuous-wave operation at room temperature, with a broad spectral band of 42 nm full width at half maximum. A 25% promotion in optical power has been realized compared to current state-of-the-art devices in this wavelength range, without sacrificing spectral bandwidth. The high-power spectral density characteristics, along with a good beam quality, are well suited for absorption spectroscopy applications and hybrid integration with silicon technology.

GaSb-based single-transverse-mode narrow ridge waveguide (RW) lasers with high power and simultaneous good beam quality have broad application prospects in the mid-infrared wavelength region. Yet its design and formation have not been investigated systematically, while the beam characteristics that affect their suitability for specific applications remain rarely analyzed and optimized. The present work addresses these issues by theoretically establishing a waveguide parameter domain that generalizes the overall possible combinations of ridge widths and etch depths that support single-transverse-mode operation for GaSb-based RW lasers. These results are applied to develop two distinct and representative waveguide designs derived from two proposed major optimization routes of model gain expansion and index-guiding enhancement. The designs were evaluated experimentally based on prototype 1-mm cavity-length RW lasers in the 1950 nm wavelength range, which were fabricated with waveguides having perpendicular ridge and smooth side-walls realized through optimized dry etching conditions. The model gain expanded RW laser design with a relatively shallow-etched (i.e., 1.55 $$\upmu$$μ m) and wide ridge (i.e., 7 $$\upmu$$μ m) yielded the highest single-transverse-mode power to date of 258 mW with a narrow lateral divergence angle of 11.1 $$^\circ$$∘ full width at half maximum at 800 mA under room-temperature continuous-wave operation, which offers promising prospects in pumping and coupling applications. Meanwhile, the index-guiding enhanced RW laser design with a relatively deeply etched (i.e., 2.05 $$\upmu$$μ m) and narrow ridge (i.e., 4 $$\upmu$$μ m) provided a highly stable and nearly astigmatism-free fundamental mode emission with an excellent beam quality of M $$^2$$2 factor around 1.5 over the entire operating current range, which is preferable for seeding external cavity applications and complex optical systems.

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.

Antimonide semiconductor laser diodes with high brightness are ideal light sources for a variety of applications. However, the traditional structure of broad-area (BA) lasers with high-power output is normally accompanied by a multi-lobed far field profile and large lateral divergence. In this paper, we put up an on-chip microstructure for mode filtering. The excellent mode control capability is doubly confirmed by optical field simulations and complete device measurements. The optimized device shows an enhanced continuous-wave output power in exceeding of 1.3 W at room temperature, along with a reduced threshold current and increased peak power conversion efficiency. Moreover, it exhibits an ultra-stable lateral far field with a 45.6% reduction in divergence and a notable 75.5% improvement in current dependence compared with conventional BA diode lasers. The minimum divergence is as low as 5.64° for full width at half maximum definition.

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.