Mimicking Neuroplasticity in a Hybrid Biopolymer Transistor by Dual Modes Modulation

Neuromorphic computing systems that are capable of parallel information storage and processing with high area and energy efficiencies, offer important opportunities for future storage systems and in‐memory computing. Here, it is shown that a carbon dots/silk protein (CDs/silk) blend can be used as a light‐tunable charge trapping medium to fabricate an electro‐photoactive transistor synapse. The synaptic device can be optically operated in volatile or nonvolatile modes, ensuring concomitant short‐term and long‐term neuroplasticity. The synaptic‐like behaviors are attributed to the photogating effect induced by trapped photogenerated electrons in the hybrid CDs/silk film which is confirmed with atomic force microscopy based electrical techniques. In addition, system‐level pattern recognition capability of the synaptic device is evaluated by a single‐layer perceptron model. The remote optical operation of neuromorphic architecture provides promising building blocks to complete bioinspired photonic computing paradigms.     

Adaptive Latent Inhibition in Associatively Responsive Optoelectronic Synapse

The association of stimuli is an important attribute in the neural basis of learning and memory. While the acquisition and extinction of association through conditioning are well emulated in artificial synaptic devices, the alteration of conditioning efficacy, which enables adaptability in learning, has yet to be demonstrated. A distinctive feature of latent inhibition is that the pre-exposure to a neutral stimulus would suppress its subsequent associative pairing with a biologically salient counterpart. This presents an adaptive advantage in suppressing the learning efficacy of irrelevant stimuli, focusing attention only on relevant cues. Given the significant impact of the regulatory function in biological synapses, an associatively responsive optoelectronic synapse based on oxide Schottky interface capable of emulating latent inhibition is demonstrated. While optical programming based on photo-assisted charge detrapping emulates the biologically salient stimulus, electrical modification acts as neutrally stimulating cues, capable of altering subsequent carrier recombination dynamics. The electrical–optical coupling is leveraged to implement inhibition and facilitation of synaptic plasticity. Subsequently, the adaptability in conditioning to regulate information uptake is demonstrated via latent inhibition. Distinct from conventional optoelectronic synapses, the proposed synaptic device offers significant advantages in adaptability in learning with an electrically tunable optical memory.     

Highly Efficient Indoor Organic Photovoltaics with Spectrally Matched Fluorinated Phenylene‐Alkoxybenzothiadiazole‐Based Wide Bandgap Polymers

The unique electro‐optical features of organic photovoltaics (OPVs) have led to their use in applications that focus on indoor energy harvesters. Various adoptable photoactive materials with distinct spectral absorption windows offer enormous potential for their use under various indoor light sources. An in‐depth study on the performance optimization of indoor OPVs is conducted using various photoactive materials with different spectral absorption ranges. Among the materials, the fluorinated phenylene‐alkoxybenzothiadiazole‐based wide bandgap polymer—poly[(5,6‐bis(2‐hexyldecyloxy)benzo[c][1,2,5]thiadiazole‐4,7‐diyl)‐alt‐(5,50‐(2,5‐difluoro‐1,4‐phenylene)bis(thiophen‐2‐yl))] (PDTBTBz‐2F_anti)‐contained photoactive layer—exhibits a superior spectrum matching with indoor lights, particularly a light‐emitting diode (LED), which results in an excellent power absorption ratio. These optical properties contribute to the state‐of‐the‐art performance of the PDTBTBz‐2F_anti:[6,6]‐phenyl‐C₇₁ butyric acid methyl ester (PC₇₁BM)‐based OPV with an unprecedented high power‐conversion efficiency (PCE) of 23.1% under a 1000 lx LED. Finally, its indoor photovoltaic performance is observed to be better than that of an interdigitated‐back‐contact‐based silicon photovoltaic (PCE of 16.3%).     

A Photoclick Hydrogel for Enhanced Single‐Cell Immunoblotting

Advances in single‐cell immunoblotting assays, which facilitate the exploration of cell‐to‐cell variation that affects biological systems from cancer development to stem cell biology, have attracted much attention. A tetrazole‐functionalized photoclick hydrogel is reported for single‐cell proteomic analysis. The gel serves as a molecular sieving matrix for sodium dodecyl sulfate–polyacrylamide gel electrophoresis and a protein immobilization scaffold for in‐gel immunoblotting. Upon a very short time (60 s) of long‐wavelength ultraviolet irradiation, it can effectively capture the electrophoretically separated proteins in the gel for the subsequent in situ antibody incubation. As a proof of concept, its performance is demonstrated in profiling cell‐to‐cell variations of P‐glycoprotein expression in GES‐1/MGC803 cell lines treated with different drugs. Combined with single‐cell immunoblotting method, employing this photoactive gel enables the monitoring simultaneously in ≈2000 individual cells of subtle protein expression level changes that may be concealed using conventional techniques. The proposed gel has the advantages of excellent electrophoretic separation ability, high protein photoimmobilization efficiency, low autofluorescence, and it can be used as a promising photoactive polyacrylamide gel for in‐gel/in situ capillary and microfluidic immunoblotting assays, especially for developing novel single cell immunoblotting methods.     

Tuning the synaptic behaviors of biocompatible synaptic transistor through ion-doping

Biodegradable and environmentally friendly artificial synapse devices are essential for the future development of neuromorphic computing. The emergence of synaptic transistors based on biocompatible polymer materials provides an ideal approach to achieve green electronics. However, modulating the synaptic properties in a wide range in a fixed biocompatible synaptic transistor is still challengeable, while it is vitally important for improving the adaptability of the synaptic device to achieve neuro-prosthetics in the future. Here, we reported the regulation of the synaptic behavior of biocompatible synaptic transistor through ion-doping, which allows to adjusting the response of the synaptic device according to a specific function. The ions doped into the insulating layer strengthen the formation of electric double layers (EDLs), which enables a remarkable regulation effect on post-synaptic current. Moreover, basic synaptic properties, including excitatory/inhibitory post-synaptic current (EPCS/IPSC), paired-pulse facilitation/depression (PPF/PPD), short-term/long-term memory (STM/LTM) are successfully demonstrated. In addition, high-pass and low-pass filtering functions are also implemented in a single synaptic device, indicating that the synapse attenuation can be effectively transformed according to the needs of the function. More importantly, this is the first work to demonstrate that the accuracy of pattern recognition of synaptic transistors, an important indicator of neuromorphic calculations, can be significantly improved via ion doping (as high as 75.96% relative to undoped devices of 41.68%). Our research provides a feasible strategy for precisely controlling synaptic behaviors, which has a profound impact on improving the adaptability of artificial synaptic devices in the field of neuromorphic computing.     

Photocrosslinkable Zwitterionic Ligands for Perovskite Nanocrystals: Self-Assembly and High-Resolution Direct Patterning

Perovskite nanocrystals (PNCs) are attractive photoactive materials in various optoelectronic devices including light-emitting diodes, solar cells, and photodetectors. However, the weakly bound surface ligands on PNCs reduce colloidal stability and cause film formation and patterning difficulties, severely restricting their practical applications. Herein, a rationally designed photocrosslinkable zwitterionic (PZ) ligand is introduced to obtain directly patternable CsPbBr₃ PNCs with enhanced colloidal stability, optical properties, and self-assembly propensity. The PZ ligands strongly interact with the pre-synthesized PNCs in solution, substantially replacing the original capping ligands and effectively passivating surface defects. This surface engineering induces strong electrostatic interactions between the PNCs, enabling the fabrication of densely packed CsPbBr₃ PNC films. Furthermore, the methacrylate group of the PZ ligands serves as a bridge for active radical propagation in the ligand shells around the PNCs upon UV exposure. Accordingly, high-resolution direct photopatterning can be achieved through ligand crosslinking, and the resulting PNC patterns (minimum line spacing of 4 µm) maintain optical stability for over 2 weeks. Therefore, this study demonstrates that a tailored ligand design strategy enables the simultaneous achievement of high colloidal stability, optical properties, photopatternability, and self-assembly propensity and has considerable potential to be extended to other PNC materials.     

Novel Photoinduced Recovery of OFET Memories Based on Ambipolar Polymer Electret for Photorecorder Application

A new design concept for novel photoresponsive flash organic field‐effect transistor (OFET) memory is demonstrated by employing the carbazoledioxazine polymer (Poly CD) as an electret. Photoactive electrets that can absorb the light effectively rather than photoactive semiconductors are proposed by the “photoinduced recovery” mechanism in the literature; however, the correlation between the chemical structure and photoresponsive electrical performances is ambiguous. In this study, it is reported for the first time that the OFET memory with trapped charges can be optically recovered by a polymer electret and the working mechanism can be explained by the structural design. The highly planar Poly CD electret exhibits photoluminescence quenching in film states, resulting in the generation of sufficient excitons to eliminate trapped charges under light excitation. Additionally, the Poly CD electret with coplanar donor–acceptor moieties is suitable for both p‐channel and n‐channel semiconductors. For p‐type memory devices, a large memory window (82 V) and stable nonvolatile retention performance with high ON/OFF ratio could be obtained. The memories also display good switching reliability for voltage‐programming and light‐erasing cycles. This study provides useful information for the development of polymer‐based photoresponsive flash OFET memories and demonstrates the practical applications of photorecorder and photosensitive smart tag.     

Tunable Volatility of Ge2Sb2Te5 in Integrated Photonics

The operation of a single class of optical materials in both a volatile and nonvolatile manner is becoming increasingly important in many applications. This is particularly true in the newly emerging field of photonic neuromorphic computing, where it is desirable to have both volatile (short‐term transient) and nonvolatile (long‐term static) memory operation, for instance, to mimic the behavior of biological neurons and synapses. The search for such materials thus far have focused on phase change materials where typically two different types are required for the two different operational regimes. In this paper, a tunable volatile/nonvolatile response is demonstrated in a photonic phase‐change memory cell based on the commonly employed nonvolatile material Ge₂Sb₂Te₅ (GST). A time‐dependent, multiphysics simulation framework is developed to corroborate the experimental results, allowing us to spatially resolve the recrystallization dynamics within the memory cell. It is then demonstrated that this unique approach to photonic memory enables both data storage with tunable volatility and detection of coincident events between two pulse trains on an integrated chip. Finally, improved efficiency and all‐optical routing with controlled volatility are demonstrated in a ring resonator. These crucial results show that volatility is intrinsically tunable in normally nonvolatile GST which can be used in both regimes interchangeably.     

光端机采用砷化镓器件后质量指标提高量试算

推导出光链路C/N指标的简化计算式,并计算光接收模块改用砷化镓材料以后、光发射机改用砷化镓放大模块以后,光链路C/N指标和CTB指标的提高量.同时还说明光接收机内光接收模块下面的电放大模块实际上是电缆网络中的第一级放大器,在系统指标设计时不宜将它并入光链路.     

Towards engineering in memristors for emerging memory and neuromorphic computing:A review

Resistive random-access memory(RRAM),also known as memristors,having a very simple device structure with two terminals,fulfill almost all of the fundamental requirements of volatile memory,nonvolatile memory,and neuromorphic characteristics.Its memory and neuromorphic behaviors are currently being explored in relation to a range of materials,such as biological materials,perovskites,2D materials,and transition metal oxides.In this review,we discuss the different electrical behaviors exhibited by RRAM devices based on these materials by briefly explaining their corresponding switching mechanisms.We then discuss emergent memory technologies using memristors,together with its potential neuromorphic applications,by elucidating the different material engineering techniques used during device fabrication to improve the memory and neuromorphic performance of devices,in areas such as ION/IOFF ratio,endurance,spike time-dependent plasticity(STDP),and paired-pulse facilitation(PPF),among others.The emulation of essential biological synaptic functions realized in various switching materials,including inorganic metal oxides and new organic materials,as well as diverse device structures such as single-layer and multilayer hetero-structured devices,and crossbar arrays,is analyzed in detail.Finally,we discuss current challenges and future prospects for the development of inorganic and new materials-based memristors.     

Photorefractive optics in three-dimensional digital memory

To exceed the capacity limitation of the surface-recording method of current optical data storage, the third dimension is introduced with photorefractive materials. Photorefractive materials are suitable for three-dimensional data storage in conjunction with nonlinear optical systems such as the two-photon absorption process of the material for recording and the confocal laser-scanning system for reading. I will describe the systems and the materials for three-dimensional digital memory with the experimental results for read-only memory with photopolymer, erasable memory with a lithium niobate crystal and rewritable memory with photochromic organic materials. The comparison between photorefractive digital three-dimensional memory with conventional holographic three-dimensional memory and near-field memory is also discussed in terms of dynamic range, noise, recording density, and accessibility     

Dual-Modal Optoelectronic Synaptic Devices with Versatile Synaptic Plasticity

Optoelectronic synaptic devices that mimic biological synapses are critical building blocks of artificial neural networks (ANN) based on optoelectronic integration. Here it is shown that an optoelectronic synaptic device based on the hybrid structure of silicon nanocrystals (Si NCs) and poly(3-hexylthiophene) (P3HT) can work with dual modes, exhibiting versatile synaptic plasticity. In the three-terminal mode, the device is a synaptic transistor, which has wavelength-selective synaptic plasticity due to potential wells enabled by the Si NCs/P3HT hybrid structure. In the two-terminal mode, it is a synaptic metal-oxide-semiconductor (MOS) device, which is capable of mimicking spike-rate-dependent plasticity (SRDP) and metaplasticity with optical stimulation. Based on the wavelength-selective synaptic plasticity a light-stimulated ANN is proposed to recognize handwritten digits with an accuracy of around 90.4%. In addition, the SRDP and metaplasticity may be well used for the simulation of edge detection of images, facilitating real-time image processing.     

Optical packet switching and buffering by using all-optical signal processing methods

We present a 1 /spl times/ 2 all-optical packet switch. All the processing of the header information is carried out in the optical domain. The optical headers are recognized by employing the two-pulse correlation principle in a semiconductor laser amplifier in loop optical mirror (SLALOM) configuration. The processed header information is stored in an optical flip-flop memory that is based on a symmetric configuration of two coupled lasers. The optical flip-flop memory drives a wavelength routing switch that is based on cross-gain modulation in a semiconductor optical amplifier. We also present an alternative optical packet routing concept that can be used for all-optical buffering of data packets. In this case, an optical threshold function that is based on a asymmetric configuration of two coupled lasers is used to drive a wavelength routing switch. Experimental results are presented for both the 1 /spl times/ 2 optical packet switch and the optical buffer switch.     

Highly compact integrated optical set-reset memory pixels forparallel processing arrays

An integrated optoelectronic device with a single-mesa structure, which functions as an optical set-reset memory or an optical inverter, is reported. The device is composed of two heterojunction phototransistors and a light-emitting diode vertically integrated on an InGaAsP/InGaAs/InP wafer grown by gas source molecular beam epitaxy. The set and reset beams are incident on a single optical window on each device and are separated by wavelength. The prototype device has shown a large on/off control ratio (27) with relatively low input optical power levels (tens of microwatts). This device concept is extendable to large integrated arrays which are capable of directly processing spatial light signals     

Holographic Recording in a Photoactive Elastomer

This work explores the use of photoactive elastomers as elastic holographic materials. Holographic gratings were recorded on stretched films of an azobenzene elastomer, which is composed of a side‐chain liquid‐crystalline polymer with azobenzene mesogens, grafted to the rubbery polybutadiene block of a styrene–butadiene–styrene (SBS) triblock copolymer. The grating‐formation dynamics measurements revealed the formation of two gratings of different natures resulting from the coupled mechanical and optical effects. A first grating, formed quickly upon exposure, is due to the photoisomerization of oriented azobenzene groups. A second grating, developed at longer exposure times, may originate from changes in the anisotropic structure of the SBS matrix, which is induced by the photochemical phase transition of azobenzene mesogens. The first grating is unstable, but the second grating remains in relaxed films. Both mechanisms can be enhanced by deformation of the film.     

Evaluating Carrier Accumulation in Degraded Bulk Heterojunction Organic Solar Cells by a Thermally Stimulated Current Technique

Here, the initial photo‐degradation of encapsulated P3HT:PCBM bulk heterojunction organic solar cells is investigated. The degraded device is recovered by thermal annealing treatment. Thermally stimulated current measurements reveal that the cause of photo‐degradation is carrier accumulation and that the degraded organic solar cell has two broad trap levels, of 0.71 and 0.81 eV. These traps are independent of the thickness of the photoactive layers, the mixing ratio of the photoactive materials and the cathode materials. In addition, it is confirmed that there is a close relationship between the degree of degradation and the amount of accumulated charge carriers.     

A fiber-optic autocollimation refractometric method for dispersionmeasurement of bulk optical materials using a widely tunable fiber Ramanlaser

A simple and highly sensitive fiber-optic autocollimation method for refractive-index dispersion measurement of solid-state and liquid bulk optical materials is presented. The method is based on the use of a double-pass multimode fiber Raman laser which generates widely tunable emission in a broadband (0.54-1.01 μm) continuous spectral range at pumping with the second harmonic of a Q-switched Nd:YAG laser. The optical fiber is used in a specific multifunctional regime where, because of its micrometric core dimensions, it serves simultaneously as a point laser source for the formation of a collimated input emission, as a highly sensitive receiver of the autocollimation backreflectance, and as a medium for nonlinear frequency conversion and generation of a broad-band continuum spectrum. The experimental results obtained in the refractive-index dispersion measurements are fitted to the Sellmeier dispersion equation and used to determine the material dispersion and additional dispersive characteristics of the test optical material     

New concept for multiple-valued optical memory

The authors propose and demonstrate a new concept for multiple-valued optical memory, instead of the usual binary optical memory, based on the recognition of an angle of the slender diffracted-light pattern from one of the slits or slender pits formed, in order, along a track of the optical disk. A photodiode array arranged in a clock face configuration is used for the light pattern recognition     

Multistability in Bistable Ferroelectric Materials toward Adaptive Applications

Traditionally thermodynamically bistable ferroic materials are used for nonvolatile operations based on logic gates (e.g., in the form of field effect transistors). But, this inherent bistability in these class of materials limits their applicability for adaptive operations. Emulating biological synapses in real materials necessitates gradual tuning of resistance in a nonvolatile manner. Even though in recent years few observations have been made of adaptive devices using a ferroelectric, the principal question as to how to make a ferroelectric adaptive has remained elusive in the literature. Here, it is shown that by locally controlling the nucleation energy distribution at the ferroelectric–electrode interface multiple‐addressable states in a ferroelectric can be created, which is necessary for adaptive/synaptic applications. This is realized by depositing a layer of nonswitchable ZnO on top of thin film ferroelectric PbZr _x Ti_{(1– x )}O₃. This methodology of interface‐engineered ferroelectric should enable realising brain‐like adaptive/synaptic memory in complementary metal‐oxide‐semiconductor (CMOS) devices. Furthermore, the temporally stable multistability in ferroelectrics should enable the designing of multistate memory and logic devices.     

Transparent and Flexible Inorganic Perovskite Photonic Artificial Synapses with Dual-Mode Operation

With the rapid development of artificial intelligence, the simulation of the human brain for neuromorphic computing has demonstrated unprecedented progress. Photonic artificial synapses are strongly desirable owing to their higher neuron selectivity, lower crosstalk, wavelength multiplexing capabilities, and low operating power compared to their electric counterparts. This study demonstrates a highly transparent and flexible artificial synapse with a two-terminal architecture that emulates photonic synaptic functionalities. This optically triggered artificial synapse exhibits clear synaptic characteristics such as paired-pulse facilitation, short/long-term memory, and synaptic behavior analogous to that of the iris in the human eye. Ultraviolet light illumination-induced neuromorphic characteristics exhibited by the synapse are attributed to carrier trapping and detrapping in the SnO₂ nanoparticles and CsPbCl₃ perovskite interface. Moreover, the ability to detect deep red light without changes in synaptic behavior indicates the potential for dual-mode operation. This study establishes a novel two-terminal architecture for highly transparent and flexible photonic artificial synapse that can help facilitate higher integration density of transparent 3D stacking memristors, and make it possible to approach optical learning, memory, computing, and visual recognition.