During the 1994 Clementine lunar mapping mission, portions of 25 orbits were dedicated to a search for lunar horizon glow (LHG) using the spacecraft star tracker navigation cameras. Previous putative detections of LHG were believed to result from forward scattering of sunlight by exospheric dust grains with radii ≈ 0.1 µm, observable above the limb from within the shadow of the Moon near orbital sunrise or sunset. We have examined star tracker image sequences from five Clementine orbits in which the limb occulted the Sun, and was at least partially shadowed from earthshine, minimizing the chance of stray light contamination. No LHG appears in the image data, or in any of the net brightness images, after subtraction of a reference zodiacal light model. However, some of the images display faint excess limb brightness that appears to be solar streamer structure. Therefore, we derive upper limits for the amount of dust in the lunar exosphere that could be hidden by these brightness fluctuations using a dust‐scattering simulation code and simple exponential dust profiles defined by surface concentration n₀ and scale height H. Simulations using grains of radius 0.1 µm show that fluctuations in the observed excess brightness can be matched by a dust exosphere with a vertical column abundance n₀H of 5–30 cm⁻² and overlying mass <10⁻¹² g cm⁻². These dust upper limit estimates are highly dependent on assumed grain size due to the rapid increase in per‐grain brightness with grain radius.

InAs/GaAs quantum dot (QD) laser monolithically grown on silicon is one of the potential approaches to realizing silicon-based light sources. However, the mismatch between GaAs and Si generates a high density of threading dislocations (TDs) and antiphase boundaries (APBs), which trap carriers and adversely affect device performance. In this paper, we present a simple method to reduce the threading dislocation density (TDD) merely through GaAs buffer, eliminating the intricate dislocation filter layers (DFLs) as well as any intermediate buffer layers whose compositions are different from the target GaAs. An APB-free epitaxial 2.5 µm GaAs film was grown on exact Si (001) by metalorganic chemical vapor deposition (MOCVD) with a TDD of 9.4 × 10⁶cm⁻². InAs/GaAs QDs with a density of 5.2 × 10¹⁰cm⁻² were grown on this GaAs/Si (001) virtual substrate by molecular beam epitaxy (MBE) system. The fabricated QD laser has achieved a single facet room temperature continuous-wave output power of 138 mW with a threshold current density of 397 A/cm² and a lasing wavelength of 1306 nm. In this work, we propose a simplified method to fabricate high-power QD lasers, which is expected to promote the application of photonic integrated circuits.

This article presents a numerical simulation and experimental study on thermal management of high-power large-area vertical-cavity surface-emitting laser (VCSEL) arrays. We fabricated 1 $\times$ 1 mm and 5 $\times$ 5 mm VCSEL arrays and constructed their respective 3-D electro-thermal coupling models. Detailed information about the thermal power within the VCSEL arrays was obtained through theoretical analysis. Combined with the experimental data, the thermal distribution of the arrays was calculated. Furthermore, a random function with Gaussian distribution was used to simulate random voids in the packaging, and the thermal characteristics of devices with void ratios of 0%, 5%, and 10% were analyzed. Through theoretical simulations and experimental measurements, a detailed quantitative analysis of the thermal effects of GaAs substrates on high-power VCSEL arrays was performed. This work demonstrates that effective thermal management of the array can be achieved by removing the substrate and controlling the void ratio to below 5%.

We have demonstrated the integration of subwavelength gratings (SWG) into a 795 nm vertical cavity surface emitting laser (VCSEL) with inverse surface relief to achieve coordinated control of the mode and polarization. At a grating period of around 0.5 μm and an etching depth range of 60 nm to 100 nm, the reflectivity was higher than 91%. A high reflectivity difference was introduced between different modes, effectively suppressing high-order modes with a side mode suppression ratio (SMSR) of 38 dB. The SWG exhibited different refractive indices for the transverse electric (TE) and transverse magnetic (TM) components, increasing anisotropy and thus enhancing the orthogonal polarization suppression ratio (OPSR) to 26.7 dB. The predesign and relaxed fabrication tolerances of grating parameters may facilitate the mass production of highperformance VCSELs for applications in quantum sensing systems

Vertical-cavity surface-emitting lasers (VCSELs) are essential for exhibiting single-transverse-mode output characteristics, which are critical for applications in quantum sensing, optical interconnection, and laser printing. In this study, we achieved stable single-transverse-mode lasing using extended-2λ-cavity with an oxide aperture diameter of 7.08 μm. The device demonstrated a high output power of 6.8 mW and a narrow linewidth of 49.8 MHz at room temperature. Additionally, it maintained stable single-mode emission at 794.8 nm and achieved a side-mode suppression ratio (SMSR) exceeding 40 dB within the temperature range of 25 °C~85 °C, thereby meeting the requirements of ⁸⁷Rb atom quantum sensors. The fabricated device obtained high-power and narrow linewidth single-transverse-mode operation by a monolithic extended cavity without introducing additional processing procedures, which is expected to promote the commercial viability of VCSELs in quantum sensing.

A highly strained InGaAs quantum well (QW) vertical-cavity surface-emitting laser (VCSEL) with low threshold current density, high efficiency and output power emissions around 1130 nm was grown by MOCVD. Its static characteristics at room temperature and high operation temperature were studied in detail. The 7 μm oxide aperture device exhibits a threshold current of 0.68 mA, corresponding to a threshold current density of 1.7 kA/cm². The slope efficiency is 0.43 W/A and the maximum output power is 3.3 mW. Continuous-wave (CW) operation in the 10–80 °C temperature range is observed. The slope efficiency is almost constant at 10–80 °C. The threshold current becomes lower at high temperatures thanks to the alignment between gain peak and cavity mode. The 3 μm oxide aperture device’s lasing in single mode with the RMS spectral width of 0.163 nm and orthogonal polarization suppression ratio (OPSR) is ~15 dB at 25 °C. The small-signal response analysis indicates that reducing the parasitics of the device and refining the fabrication process will improve the dynamics response characteristics. These results indicate that the 1130 nm GaAs-based VCSEL with highly strained InGaAs QWs is expected to be used as source for silicon photonics.