Yanmei Su

In this paper, a novel beam direction controllable multi-junction Vertical-Cavity Surface Emitting Laser (VCSEL) is proposed. By etching periodic blazed gratings on the 300 μm in length rectangular triple-junction VCSEL surface insulating layer, the defect of multi-beam emission of current micro-structured lasers is successfully suppressed, and a high power directional single beam was achieved according to the simulation. In addition, by integrating VCSELs with blazed gratings of different grating periods into an array, the emission directions of the laser beams can cover a large field of view (FOV) of 130°. Considering the complexity of the blazed grating fabrication, the diffraction effects using a 3-step multilevel grating as an alternative are also simulated in this paper, and the results demonstrate that it can also achieve the same FOV theoretically. By integrating VCSELs with different beam deflection angles into an array, it is expected to be applied to all-solid-state light detection and ranging (LiDAR) systems for direct scanning.

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.

In this paper, a single emission peak microstructured lasers array for beam control is proposed. And lasers in the array can emit beams in specific directions with low vertical divergence angles. The initial phase control is introduced to solve the problem of multiple emission peaks in a vertical far-field pattern. Both simulation and experimental analyses corroborate that the intensity of high-order diffraction peaks can be suppressed by introducing an appropriate starting position. Experimental results showcase the achievement of a low vertical divergence angle of 0.95° and an expansive angle sweep range of 61.2°. Furthermore, leveraging a taper structure, a horizontal divergence angle of 3.7° and a typical optical output power of 28 mW are obtained.

A chip-level optical beam steerer is an inevitable choice for next-generation light detection and ranging (LiDAR). The research on optical phased array (OPA) is the most intriguing. However, the complexity of control and calibration speed limit the full potential as the number of channels increases. In this paper, an improved stochastic parallel gradient-descent algorithm combined with the Nesterov accelerated gradient method (NSPGD) is presented and applied in a 512-channel OPA. This algorithm can reduce the phase calibration time of large-scale OPA and demonstrates a better convergence performance than traditional SPGD. Compared with the traditional SPGD and hill-climbing (HC) algorithm, optimized convergence performance of NSPGD is shown. The side mode suppression ratio (SMSR) of over 10dB for 512-channel OPA is obtained with the NSPGD algorithm, and the convergence speed is twice that of traditional SPGD. In addition, a temperature-controlled OPA is also studied to stabilize the whole calibration system.

In this paper, a microstructured laser with modulated periodic microstructures for beam control is proposed for the first time. Lasers using modulated periodic microstructures can emit beam with lower vertical divergence angle for the same number of microstructures. And lasers with specific period length can transmit beam in specific direction. These lasers emitting beams with different emission directions can be integrated into an array. And this array can be used directly as a transmitter chip of LiDAR. Both simulation and experimental results show that the modulated periodic microstructures can effectively reduce the vertical divergence angle. In the experiment, the lowest vertical divergence angle of 0.88° and a large angle sweep range of 41.5° have been obtained. A horizontal divergence angle of 4.3° is achieved with the taper structure. Typical optical power is 29 mW.

Optical neural networks (ONNs) are getting more and more attention due to their advantages such as high-speed and low power consumption. However, in a non-ideal environment, the noise and low-bits control may heavily lead to a decrease in the accuracy of ONNs. Since there is AD/DA conversion in a simulated neural network, it needs to be quantified in the model. In this paper, we propose a quantitative method to adapt ONN to a non-ideal environment with fixed-point transmission, based on the new chip structure we designed previously. An MNIST hand-written data set was used to test and simulate the model we established. The experimental results showed that the quantization-noise model we established has a good performance, for which the accuracy was up to about 96%. Compared with the electrical method, the proposed quantization method can effectively solve the non-ideal ONN problem.