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 the fabrication of high-power, high-spectral-purity GaSb-based laterally coupled distributed feedback (LC-DFB) lasers emitting at 2 μm. Second-order Chromium-Bragg-gratings are fabricated alongside the ridge waveguide by lift off. Due to the introduction of gain coupling, the lasers exhibit a stable single mode operation [side-mode suppression ratio (SMSR) >40 dB] from 10 °C to 50 °C and the maximum SMSR is as high as 53 dB. At a heat-sink temperature of 10 °C, the lasers emit more than 40 mW continuous-wave in a single longitudinal mode. A high external quantum efficiency of 48% is obtained, resulting in a notable increase in power conversion efficiency peaking at 13%. The lasers achieve a comparable output power with that of the index-coupled LC-DFB lasers, while maintaining a better single mode performance. Thus, we prove the feasibility of the metal-grating LC-DFB structure to achieve high-power, frequency-stable semiconductor lasers through a simpler and much more convenient way.

High-performance p-B-n infrared photodetectors based on In0.53Ga0.47As/Ga0.51As0.49Sb type-II superlattices with an Al0.85Ga0.15AsSb barrier on an InP substrate have been demonstrated. These photodetectors exhibit 50% and 100% cutoff wavelengths of ∼2.1 μm and ∼2.6 μm, respectively. At a bias voltage of −100 mV bias voltage, the device exhibits a peak responsivity of 0.618 A/W at 2.1 μm, corresponding to a quantum efficiency of 36.5%. The device exhibits a saturated dark current shot noise limited specific detectivity (D*) of 4.12 × 1010 cm·Hz1/2/W (at a peak responsivity of 2.1 μm) under −100 mV applied bias at 300 K.

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.