Jian Li

We demonstrate a monolithic extended-cavity vertical-cavity surface-emitting laser (VCSEL) achieving a linewidth of 890 kHz, which, to our knowledge, ranks among the narrowest reported for this class of lasers. The device incorporates an extended cavity and an intermediate reflector monolithically integrated into the epitaxial structure, forming a coupled configuration that significantly increases photon circulation path and enhances mode selectivity. The device has an emitting wavelength of 795 nm, with a side-mode suppression ratio of 40 dB. This work validates the feasibility of using monolithic extended cavities to achieve sub-megahertz linewidths in VCSELs without external feedback or complex packaging, offering a promising pathway for applications in coherent optical communications, laser spectroscopy, and quantum sensing.

The integration of aluminum gallium nitride (AlGaN) with silicon substrates attracts significant attention due to the superior UV sensitivity of AlGaN and the cost-effectiveness as well as mechanical robustness of silicon. A PIN ultraviolet photodetector with a peak detection wavelength of 274 nm is presented in this paper. By employing a SiN nucleation layer and a step-graded buffer, a high-quality AlGaN-based photodetector structure with a dislocation density of 2.4 × 10⁹/cm² is achieved. A double-temperature annealing technique is utilized to optimize the Ohmic contact of the n-type AlGaN. The fabricated UV photodetector attains a dark current of 0.12 nA at −1 V and a peak responsivity of 0.12 A/W.

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 silicon‐based room temperature (RT) continuous wave (CW) operation quantum well (QW) laser emitting at 850 nm is reported in this article. By applying the dislocation filter superlattice, the threading dislocation density of the GaAs pseudosubstrate on Si is reduced to 1.8 × 10⁷ cm⁻². The metal‐organic chemical vapor deposition‐grown laser structure with GaAs/GaAsP QW and InAlAs active region dislocation blocking layer are fabricated into broad‐stripe Fabry–Perot laser diodes. A typical threshold current and threshold current density of 286 mA and 715 Acm⁻² are obtained with 2 mm cavity length and 20 um stripe width samples. A 94.2 mW single‐facet output power lasing around 854 nm and a 0.314 WA⁻¹ slope efficiency is measured under RT CW operation. After a 10‐min aging process, the tested laser can operate stably under continuous operation conditions at RT and the lifetime can be approximated using an exponential fitting curve, indicating a good life reliability of this QW laser.

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.

The enhancement of the reliability of the silicon-based III–V quantum well lasers, especially of those on an on-axis Si (001) substrate, is of great importance now a days for the development of Si-based photonic and even optoelectronic integrated circuits and is really quite challenging. As an experimental advancement, mainly by inserting a pair of InAlAs strained layers separately into the upper and lower AlGaAs cladding layers to effectively prevent the formation of the in-plane gliding misfit-dislocations within the boundary planes of the active region, the longest room-temperature and continuous-wave lifetime of the InGaAs/AlGaAs quantum well lasers on an on-axis Si (001) substrate with a cavity length of 1500 µm and a ridge width of 20 µm has been prolonged from a very initial record of ∼90 s to the present length longer than 31 min. While, the highest continuous-wave operation temperature of another one with a cavity length of 1000 µm and a ridge width of 10 µm has been shown as 103 °C with an extracted characteristic temperature of 152.7 K, further enhancement of the device reliability is still expected and would mainly depend on the level of the threading-dislocation-density reduction in the GaAs/Si virtual substrate.

We designed and demonstrated a temperature-stable, wide-tuned, high-power Vertical External Cavity Surface-emitting Laser (VECSEL) with a simple linear cavity. The quantum well is optimized by using the commercial PICS3D software to obtain wide gain and good thermal performance. The curve of BF has also been optimized, and a birefringent filter (BF) with a thickness of 1mm is selected as the tuning element. Then, we obtained a continuously adjustable range cover from 1044.5 nm to 1092.1 nm, 8 W of output power, and temperature-stable VECSEL, which verifies the feasibility of the design. Based on the experimental results, we concluded that the gain intensity corresponding to the tuning range should be at least greater than 163 e ²⁶ /cm ⁻³ s ⁻¹ eV ⁻¹ before the growth process ensures a wide tuning range. For the first time, to the best of our knowledge, we designed and obtained the tuning result of VECSEL in the linear cavity, and this is of great significance to the design of VECSEL with wide-tuning, high-power, and good temperature stability.