We report electrically pumped continuous-wave (CW) InAs/GaAs quantum dot lasers directly grown on planar exact silicon (001) with asymmetric waveguide structures. Surface hydrogen-annealing for the GaAs/ Si (001) templates and low-temperature growth for GaInP upper cladding layers were combined in the growth of the laser structure to achieve a high slope efficiency. For the broad-stripe edge-emitting lasers with 2-mm cavity length and 20-µm stripe width made from the above laser structure, a threshold current density of 203.5 A/cm² and a single-facet slope efficiency of 0.158 W/A are achieved at ∼1.31 µm band under CW conditions. The extrapolated mean-time-to-failure reaches up to 21000 hours at room temperature, which is deduced from the data measured from C-mount packaged devices. Importantly, these results can provide a practical strategy to realize 1.3 µm wavelength band distributed feedback lasers directly on planar exact Si (001) templates with thin buffer layers.

An 1500 nm thick collector layer is adopted in the uni-travelling-carrier photodiode (UTC-PD) to reduce the PD's capacitance, while the PD's diameter is set to be 20 μm for better saturation performance and optical coupling characteristic of a signal from a single mode fiber. By optimizing biasing voltage and input light intensity, the electric field intensity in the collector layer would be controlled to make the photo-generated electron in the UTC-PD transiting at around its peak drift velocity in the collector layer and at the same time to make the UTC-PD obtaining it minimum capacitance. Together with the optimization of the doping distribution in UTC-PD's cliff layer and its collector layer, the UTC-PD's high-speed performance and saturation performance can be further improved. An optimized 20 μm diameter UTC-PD with a simulated 106 GHz 3 dB bandwidth and 21.02 dBm output RF power at 25 GHz is designed. It proposes a discussion to realize high speed, high saturation performance UTC-PD together with high coupling efficiency from a single mode optical fiber by bringing the electric field determined drift velocity performance of its uni-traveling- carrier, the electron, into full play.

A novel Microstructure PIN photodiode (MPIN-PD) using the ray-optic theory of light trapping effect is presented and analyzed numerically. The MPIN-PD is proposed from an ordinary large-diameter PIN-PD by introducing an obconical shape surrounded by a V-groove trench. The photon-material interaction is increased by using the microstructure in the PIN-PD. It can control light and cause syntony in the absorption layer, reducing the junction capacitance of the PD, and suppressing the tradeoff between the efficiency and bandwidth. Thus, both 3- dB bandwidth and quantum efficiency can be improved simultaneously. The parameters of the MPIN-PD, including the depth and apex angles of the micro-structure, the distance between the cone and V-groove trench are carefully studied to estimate their positive effects of the performance of the MPIN-PD. The transmission line model is exploited for the specific structure to design the electrodes’ distribution.

Recently, numerous wearable devices for gesture recognition have been reported, however, most of them are fabricated by assembling the separately-designed sensing layers with the substrate through linking agents, which will lead to the shifting or detaching of the sensing layers after long-duration use. Subsequently, over-reliance on multiple filtering algorithms to smooth the collected datasets becomes very popular, unavoidably resulting in the loss of data features and overfitting. In our point of view, it is much more crucial and effective for gesture recognition performance to reinforce the stability of the sensing layers. Therefore, in this work, we designed a type of Integrated MXene/Polyurethane (I-M/PU) sensor based on textile fabrics and further prepared a data glove, a smart wristband and a smart elbow pad. A wearable system for gesture recognition with ultra-high sensitivity to strain, as well as excellent stability and durability is successfully realized by the synergy of those three devices. The collected original data by the integrated sensors was steady with specific features, making the simplification of the classification model feasible. Finally, 19 static gestures (including 9 complex gestures) with the recognition accuracy of 100% in 6998 data samples have been impressively achieved by the simple Multilayer Perceptron (MLP) algorithm, which is the state-of-art best result as we know in the gesture recognition reports without any assistant computer vision algorithms, demonstrating our solution with a promising prospect in Virtual Reality (VR) and Human-Machine Interaction (HMI) fields.

InGaAs/AlGaAs multiple quantum well lasers grown on silicon (001) by molecular beam epitaxy have been demonstrated. By inserting InAlAs trapping layers into AlGaAs cladding layers, misfit dislocations easily located in the active region can be effectively transferred out of the active region. For comparison, the same laser structure without the InAlAs trapping layers was also grown. All these as-grown materials were fabricated into Fabry-Perot lasers with the same cavity size of 20 × 1000 µm². The laser with trapping layers achieved a 2.7-fold reduction in threshold current density under pulsed operation (5 µs-pulsed width, 1%-duty cycle) compared to the counterpart, and further realized a room-temperature continuous-wave lasing with a threshold current of 537 mA which corresponds to a threshold current density of 2.7 kA/cm². When the injection current reached 1000 mA, the single-facet maximum output power and slope efficiency were 45.3 mW and 0.143 W/A, respectively. This work demonstrates significantly improved performances of InGaAs/AlGaAs quantum well lasers monolithically grown on silicon, providing a feasible solution to optimize the InGaAs quantum well structure.