All-Optical Reconfigurable Metamaterial Employing the Self-Assembly of CdTe Quantum Dots

Positively and negatively charged polyelectrolytes, namely, Poly(diallyldimethylammonium chloride) and Poly(styrene sulfonate), respectively, were employed to disperse and deploy negatively charged quantum dots on an otherwise passive metamaterial structure with a resonant frequency of 0.62 THz, by employing a layer-by-layer, self-assembly scheme. Upon exposure to a UV source with a wavelength of 365 nm the amplitude modulation was observed to increase with increases in the number of deposited bi-layers, until a modulation maximum of 2.68% was recorded enabling an all-optical, dynamically reconfigurable metamaterial geometry. Furthermore, amplitude modulation was subsequently observed to decrease with further increases in the number of layers employed due to quenching and shadowing effects. The experimental observations reported herein will enable the utilization of all-optical reconfigurable THz devices for communication and data transmission applications.

Design of Evolvable Hardware for Robotic Navigation

This paper presents an integrated on line learning system to evolve programmable logic array (PLA) controllers for navigating an autonomous robot in a two dimensional environment. The integrated on line learning system consists of two learning modules: one is the module of reinforcement learning based on temporal difference learning based on genetic algorithms, and the other is the module of evolutionary learning based on genetic algorithms. The control rules extracted from the module of reinforcement learning can be used as input to the module of evolutionary learning, and quickly implemented by the PLA through on line evolution. The on line evolution has shown promise as a method of learning systems in complex environment. The evolved PLA controllers can successfully navigate the robot to a target in the two dimensional environment while avoiding collisions with randomly positioned obstacles.

Two-dimensional reconfigurable electronics enabled by asymmetric floating gate

Reconfigurable devices with customized functionalities hold great potential in addressing the scaling limits of silicon-based field-effect transistors(FETs).The conventional reconfigurable FETs are limited to the applications in logic circuits,and the commonly used multi-gate programming strategies often lead to high power consumption and device complexity.Here,we report a reconfigurable WSe_(2) optoelectronic device that can function as photodiode,artificial synapse,and 2-bit memory in a single device,enabled by an asymmetric floating gate(AFG)that can continuously program the device into different homojunction modes.The lateral p-n homojunction formed in the AFG device exhibits high-performance self-powered photodetection,with a responsivity over 0.17 A·W^(-1) and a wide detection spectral range from violet to near-infrared region.The AFG device can also mimic synaptic features of biological synapses and achieve distinct potentiation/depression behaviors under the modulation of both drain-source bias and light illumination.Moreover,when working as a 2-bit memory via the transition between n-n+and p-n homojunctions,the AFG device shows four distinct conductive states with a high on/off current ratio over 106 and good repeatability.Combining reduced processing complexity and reconfigurable functionalities,the WSe_(2) AFG devices demonstrate great potential towards high-performance photoelectric interconnected circuits.

具有高对称性可重构整流的单栅PdSe_(2)/WS_(2)二极管

二维材料由于其丰富的材料组合和可调节的能带结构,为构建可重构的电子器件提供了绝佳的机会.本文使用PdSe_(2)/WS_(2)范德瓦尔斯平面结构造了具有高对称性p-n/n-p结模式的单栅极可重构二极管.栅极调制的带-带隧穿机制为反向整流提供了与正偏同等的电流,同时器件通过控制双极性的WS_(2)构成同质n-p结实现了高反向整流比.通过栅压调制,器件的p-n/n-p结模式能够形成高度对称,整流比具有1E−04到1E+04的无极调节能力,器件因此显示出高性能的可重构整流功能.我们也基于双模整流功能构建了逻辑反相器.本工作有助于拓展二维材料多功能器件的研究.

Low-Cost Beam Steering that Covers the Entire Azimuthal Plane Powered by Amplitude-Only Synthesis of a Quintuple-Dipole Source

A new amplitude-only synthesis approach in quintuple electric dipoles(EDs)is proposed to enable the regulation of power flow in the azimuthal plane.The regulation methodology is investigated analytically with double ED,triple ED and quintuple ED models.First,when the phase difference between the EDs switches,the double ED model,acting as a reconfigurable source,can work in two modes with different power flow directions,i.e.,unidirectional mode and bidirectional mode.Then,from the triple ED model,it is verified that the power flow in the two working modes can be regulated to the desired direction in the azimuthal plane with high precision by controlling the feeding amplitudes of the dipoles.Moreover,a quintuple ED model is developed to enhance the symmetry and consistency of the power flow regulation in the plane.Finally,a prototype of the azimuthal beam steering system,including digitally controlled radio-frequency(RF)frontend tuning circuits,optimized practical feeding elements,and an end-fire radiator,is designed,fabricated and measured.Both unidirectional and bidirectional modes are observed,and satisfactory single-beam and dual-beam steering performance in the azimuthal plane is achieved.Unlike most phased arrays that realize beam steering by configuring phases,the beam steering of the proposed reconfigurable source in each mode can be arbitrarily synthesized only by the amplitudes of the quintuple feeding elements,which provides a new route for realizing low-cost and multifunctional beam-steering systems.