An in situ rewritable electrically-erasable photo-memory device for terahertz waves

Terahertz rewritable wavefront modulator based on indium oxide and DMSO-doped PEDOT:PSS

An optically rewritable and electrically erasable terahertz (THz) wavefront modulator based on indium oxide (In2O3) and DMSO-doped PEDOT:PSS is proposed. The modulator has a three-layer structure of In2O3/PEDOT:PSS/quartz, which can weaken the THz transmission under the action of light excitation. Optically written THz Fresnel plates, which can focus the input Gaussian beam into a point, were realized. After optical excitation, the function of the device reduces slowly if it is stored in the room environment. However, the function can be stored for a long time if it is encapsulated in the nitrogen environment. If a bias voltage of 22 V is applied on the device, the function of the device can be erased in 10 seconds. The new function can be written into the device after wiping. Experiments on THz rewritable holographic devices are carried out to show the validity of this approach. This method can provide new devices for THz wavefront modulation and develop tunable optical imaging elements.

Tunable resonance of a graphene-perovskite terahertz metasurface

The combination of graphene and perovskite has received extensive research attention because its photoelectric properties are excellent for the dynamic manipulation of light-matter interactions. Combining graphene and perovskite with a metasurface is expected to effectively improve the metasurface device's performance. Here, we report a terahertz graphene-perovskite metasurface with a tunable resonance. Under 780 nm laser excitation, the device's THz transmission is significantly reduced, and the Fano resonance mode can be manipulated in multiple dimensions. We verify the experimental results using a finite-difference time-domain (FDTD) simulation. Graphene and perovskite interact strongly with the metasurface, resulting in a short-circuit effect, which significantly weakens the resonance intensity of the Fano mode. The photoinduced conductivity enhancement intensifies the short-circuit effect, reducing the THz transmission and resonance intensity of the Fano mode and causing the resonance frequency to redshift. Finally, we provide a reference value for applications of hybrid metasurface-based optical devices in a real environment by investigating the effect of moisture on device performance.

Self-powered, ultraviolet-to-near infrared broadband photodetector based on Ag-doped CsPbI3/PEDOT:PSS heterojunction

Metal halide perovskites are studied for photodetection applications because of their outstanding optical and electrical properties. A self-powered ultraviolet-to-near infrared broadband photodetector based on a Ag-doped CsPbI₃/PEDOT:PSS heterojunction was investigated. The photodetector using a CsPbI₃:Ag/PEDOT:PSS heterostructure with a planar photoconductive structure operated over a broad 355-1560 nm wavelength range in self-powered mode. A terahertz signal was modulated with the CsPbI₃:Ag/PEDOT:PSS structure at low optical excitation intensity to investigate its photodetection mechanism. The experimentally designed detector can present images of the letters "C", "N" and "U" in the visible and near-infrared wavelengths, indicating a potential broadband imaging application.

Terahertz multi-level nonvolatile optically rewritable encryption memory based on chalcogenide phase-change materials

Fast and efficient information processing and encryption, including writing, reading, and encryption memory, is essential for upcoming terahertz (THz) communications and information encryption. Here, we demonstrate a THz multi-level, nonvolatile, optically rewritable memory and encryption memory based on chalcogenide phase-change materials, Ge₂Sb₂Te₅ (GST). By tuning the laser fluence irradiated on GST, we experimentally achieve multiple intermediate states and large-area amorphization with a diameter of centimeter-level in the THz regime. Our memory unit features a high operating speed of up to 4 ns, excellent reproducibility, and long-term stability. Utilizing this approach, hexadecimal coding information memories are implemented, and multiple writing-erasing tests are successfully carried out in the same active area. Finally, terahertz photoprint memory is demonstrated, verifying the feasibility of lithography-free devices. The demonstration suggests a practical way to protect and store information and paves a new avenue toward nonvolatile active THz devices.

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Multiple intermediate states and large-area amorphization of GST in the THz regime

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4-ns operating speed, excellent reproducibility, and long-term stability

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Multiple writing-erasing tests on hexadecimal coding information memories

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THz photoprint memory and encryption memory

Morphology engineering of a hybrid perovskite for active terahertz memory modulation

Morphology engineering was investigated for hybrid perovskites CH₃NH₃PbI₃:Ag/Poly(3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) that were fabricated in both air and nitrogen environments for active terahertz (THz) memory modulation. Under low optical excitation or an applied bias, THz amplitude modulation or rapid restore in both CH₃NH₃PbI₃:Ag/PEDOT:PSS hybrid structures were demonstrated. The recovery time of the modulated THz wave in the sample fabricated in air was considerably longer than that of the sample fabricated in nitrogen because of defect states induced by a high degree of roughness. THz transmissions were used as coded pixel units and were programmed to store a 4×4 image or a multi-order signal. Hence, active THz memory modulation was demonstrated. It also has potential applications as a visible to near-infrared broad-spectrum light detector.