An optically driven digital metasurface for programming electromagnetic functions
Xin Ge Zhang, etc
Metasurfaces are engineered surfaces that consist of subwavelength periodic elements and can be used to manipulate electromagnetic waves. Multifunctional or reconfigurable electromagnetic meta-devices based on a direct-current biasing system can be built using lumped electronic components. However, such meta-devices require bulky power supplies, field-programmable gate arrays, electrical wires and complex control circuits. Here, we report a digital metasurface platform that can be programmed optically to implement electromagnetic functions. Our digital platform has 6?×?6 subarrays, each of which contains 4?×?4 metasurface elements based on electronic varactors integrated with an optical interrogation network based on photodiodes. The interrogation network can convert visible light illumination patterns to voltages and applies bias to the metasurface elements, generating specific microwave reflection phase distributions. To illustrate the capabilities of our approach, we use the optically driven digital metasurface for external cloaking, illusion and dynamic vortex beam generation.
Wafer-scalable, aligned carbon nanotube transistors operating at frequencies of over 100?GHz
Christopher Rutherglen, etc.
Nature Electronics,2020,3: 156–164
Wireless device technology operating in the millimetre-wave regime (30 to 300?GHz) increasingly needs to offer both high performance and a high level of integration with complementary metal–oxide–semiconductor (CMOS) technology. Aligned carbon nanotubes are proposed as an alternative to III–V technologies in such applications because of their highly linear signal amplification and compatibility with CMOS. Here we report the wafer-scalable fabrication of aligned carbon nanotube field-effect transistors operating at gigahertz frequencies. The devices have gate lengths of 110?nm and are capable, in distinct devices, of an extrinsic cutoff frequency and maximum frequency of oscillation of over 100?GHz, which surpasses the 90?GHz cutoff frequency of radio-frequency CMOS devices with gate lengths of 100?nm and is close to the performance of GaAs technology. Our devices also offer good linearity, with distinct devices capable of a peak output third-order intercept point of 26.5?dB when normalized to the 1?dB compression power, and 10.4?dB when normalized to d.c. power.
Bidirectional optical signal transmission between two identical devices using perovskite diodes
Chunxiong Bao, etc
The integration of optical signal generation and reception into one device—thus allowing a bidirectional optical signal transmission between two identical devices—is of value in the development of miniaturized and integrated optoelectronic devices. However, conventional solution-processable semiconductors have intrinsic material and design limitations that prevent them from being used to create such devices with a high performance. Here we report an efficient solution-processed perovskite diode that is capable of working in both emission and detection modes. The device can be switched between modes by changing the bias direction, and it exhibits light emission with an external quantum efficiency of over 21% and a light detection limit on a subpicowatt scale. The operation speed for both functions can reach tens of megahertz. Benefiting from the small Stokes shift of perovskites, our diodes exhibit a high specific detectivity (more than 2?×?1012?Jones) at its peak emission (~804?nm), which allows an optical signal exchange between two identical diodes. To illustrate the potential of the dual-functional diode, we show that it can be used to create a monolithic pulse sensor and a bidirectional optical communication system.
A flexible phased array system with low areal mass density
Published: 17 May 2019
Mohammed Reza M.Hashemi, etc.
Phased arrays are multiple antenna systems capable of forming and steering beams electronically using constructive and destructive interference between sources. They are employed extensively in radar and communication systems but are typically rigid, bulky and heavy, which limits their use in compact or portable devices and systems. Here, we report a scalable phased array system that is both lightweight and flexible. The array architecture consists of a self-monitoring complementary metal–oxide–semiconductor-based integrated circuit, which is responsible for generating multiple independent phase- and amplitude-controlled signal channels, combined with flexible and collapsible radiating structures. The modular platform, which can be collapsed, rolled and folded, is capable of operating standalone or as a subarray in a larger-scale flexible phased array system. To illustrate the capabilities of the approach, we created a 4?×?4 flexible phased array tile operating at 9.4–10.4?GHz, with a low areal mass density of 0.1?g?cm?2. We also created a flexible phased array prototype that is powered by photovoltaic cells and intended for use in a wireless space-based solar power transfer array.