Optoelectronic synaptic devices have been attracting increasing attention due to their critical role in the development of neuromorphic computing based on optoelectronic integration. Here we start with silicon nanomembrane (Si NM) to fabricate optoelectronic synaptic devices. Organolead halide perovskite (MAPbI 3 ) is exploited to form a hybrid structure with Si NM. We demonstrate that synaptic transistors based on the hybrid structure are very sensitive to optical stimulation with low energy consumption. Synaptic functionalities such as excitatory post-synaptic current (EPSC), paired-pulse facilitation, and transition from short-term memory to long-term memory (LTM) are all successfully mimicked by using these optically stimulated synaptic transistors. The backgate-enabled tunability of the EPSC of these devices further leads to the LTM-based mimicking of visual learning and memory processes under different mood states. This work contributes to the development of Si-based optoelectronic synaptic devices for neuromorphic computing.

We proposed a new type of transverse electric (TE) polarized mode-order converter based on a deeply-etched polygonal slot on a silicon-on-insulator waveguide. Along the transverse direction of the waveguide, two irregular boundary surfaces of the slot can introduce high-contrast index modulation on guided modes, leading to multimode interference in the slot. Therefore, when the slot is optimized, we can achieve efficient mode conversions based on the multimode interference. As examples, mode converters from the fundamental TE mode (TE 0 ) to the first-order TE mode (TE 1 ) and to the second-order TE mode (TE 2 ) have both been demonstrated with a short device length (<24.0 μm), a high mode conversion efficiency (>97.6%), and a low modal crosstalk (< −20.0 dB) over a broad wavelength range from 1500 to 1600 nm (∼100 nm). In addition, based on different polygonal slots, other types of mode conversions such as from TE 1 to TE 3 and from TE 2 to TE 1 have be realized. Fabrication tolerance of the proposed structure is analyzed. Owing to the high efficiency and compact size, the proposed structure could be applied to on-chip mode division multiplexing systems for high-density integration.

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A dual-frequency Doppler Lidar (DFDL) with high precision utilizing a monolithic integrated two-section DFB laser as the dual-frequency light source is proposed and experimentally demonstrated. The DFDL can be realized with smaller size using the monolithic integrated two-section DFB laser which is fabricated by the reconstruction-equivalent-chirp (REC) technique with high precision and low fabrication cost. The range of the measured speed is from 13.62 μm /s to 1.56 m/s, which covers 6 orders of magnitude. The largest relative error of the DFDL system is 3.16%. The DFDL system has an excellent resolution of 1.95 μm/s, which is suitable to detect micro speed changes.

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