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Enhanced optical Kerr nonlinearity of graphene/Si hybrid waveguide
摘要： In this work, we experimentally study the optical Kerr nonlinearities of graphene/Si hybrid waveguides with enhanced self-phase modulation. In the case of CMOS compatible materials for nonlinear optical signal processing, Si and silicon nitride waveguides have been extensively investigated over the past decade. However, Si waveguides exhibit strong two-photon absorption (TPA) at telecommunication wavelengths, which leads to a signi?cant reduction of the nonlinear ?gure-of-merit (FOM). In contrast, a silicon nitride based material system usually suppresses the TPA but simultaneously leads to the reduction of Kerr nonlinearity by one order of magnitude. Here, we introduce a graphene/Si hybrid waveguide, which maintains the optical properties and CMOS compatibility of Si waveguides, while enhancing the Kerr nonlinearity, by transferring over to the top of the waveguides. The graphene/Si waveguides are measured to have an enhanced nonlinear parameter of 510 W(cid:2)1 m(cid:2)1, compared with that of the Si waveguide of 150 W(cid:2)1 m(cid:2)1. An enhanced nonlinear FOM of 2.48 6 0.25 has been achieved, which is four times larger than that of the Si waveguide of 0.6 6 0.1. This work reveals the potential application of graphene/Si hybrid waveguides with high Kerr nonlinearity and FOM for nonlinear all-optical signal processing.
关键词： nonlinear all-optical signal processing,graphene/Si hybrid waveguide,optical Kerr nonlinearity,CMOS compatible,self-phase modulation
更新于2025-11-28 14:23:57
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One-step Fabrication of Bio-Compatible Coordination Complex Film on Diverse Substrates for Ternary Flexible Memory
摘要： Recently, resistance random access memories (RRAMs) have been studied extensively arising from the increasing demand for information. However, its flexible device remains challenging because the active materials involved need to be nontoxic, non-polluting, distortion-tolerable, and bio-degradable as well adhesive to diverse flexible substrates. In this paper, we employed tannic acid (TA) and iron ion (Fe (III)) coordination complex as the active layer in sandwich-like (Al/active layer/substrate) device to achieve memory performance. A nontoxic, biocompatible TA-Fe (III) coordination complex was synthesized by one-step self-assembly solution. The memory performance of TA-Fe (III) retention time up to 15000 s, yield up to 53%. Furthermore, the TA-Fe (III) coordination complex can form high-quality film and show stable ternary memory behaviors on various flexible substrates, such as polyethylene terephthalate (PET), polyimide (PI), printer paper and leaf. The device can be degraded by immerse in vinegar solution. Our work will broaden the application of organic coordination complex in flexible memory device with diverse substrates.
关键词： Bio-compatible,RRAM,ternary memory,flexible
更新于2025-11-21 11:18:25
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TiO <sub/>2</sub> metasurfaces: From visible planar photonics to photochemistry
摘要： TiO2 metasurfaces have been intensively studied in the past few years. To date, the TiO2 metadevices only used their high reflective index (n). The controllable light extinction coefficient (k) of TiO2 has not been exploited yet. Here, we converted TiO2 metasurfaces to black TiO2 metasurfaces and explored their new opportunities in photochemistry. A complementary metal oxide semiconductor (CMOS)–compatible technique has been developed to reversibly and precisely control the absorption of TiO2 metasurfaces without spoiling their internal nanostructures. Consequently, two types of black TiO2 metasurfaces were realized for photochemical experiments. The metasurface with an ultrawide absorption band can substantially enhance the white light absorption and accelerate the solar-based photochemistry process by a factor of 18.7. The other metasurface with an absorption band of <20 nm only responded to the resonant wavelengths, making the photochemistry process capable of being monitored in real time. In addition, the reversible switch between normal and black states makes TiO2 metasurfaces suitable for dynamic metadevices as well.
关键词： photochemistry,CMOS-compatible technique,black TiO2,dynamic metadevices,TiO2 metasurfaces
更新于2025-10-24 16:33:39
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - High Voltage Excitation and Nonlinear Transmission of a 16 MHz AlN-Based Piezoelectric Micro-Machined Ultrasonic Transducer
摘要： This paper reports the performance of a 25 μm AlGaN-based micro-piezoelectric transducer (MPT) under high voltage excitation and determination. The proposed MPT array consists of 23×28 elements fabricated on a silicon-on-insulator (SOI) substrate with 1 μm AlGaN thin film on 24 μm silicon membrane. With all the array elements electrically connected together, the electric impedance of the MPT was 11.5–7.22 kΩ at 24.7 MHz resonance frequency in air and 3.21–7.24 kΩ at 22.8 MHz when the device was water charged. The laser Doppler vibrometer (LDV) measurements showed that the transmission efficiency and the bandwidth for free vibration were 1.6 nm/V and 1.0%, respectively. The resonance modes were specifically associated with the material parameters and the initial state of the device. Moreover, nonlinear behavior was observed when increasing the input mean power exceeded 24 mW. This strategy is potentially applied to CMOS-compatible high-resolution ultrasound imaging.
关键词： AlGaN,CMOS-compatible,Ultrasound,High voltage,Micro-piezoelectric transducer
更新于2025-09-23 15:22:29
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Embedded Near-Infrared Sensor with Tunable Sensitivity for Nanoscale CMOS Technologies
摘要： Near-infrared (NIR) sensors has become one of the key components in applications, such as temperature, proximity, and even ?ngerprint sensing. A novel full-CMOS (Complementary Metal-Oxide-Semiconductor) compatible near-infrared sensor is proposed and demonstrated in this article. This sensing device consists of a gateless transistor, enabling near-infrared photon absorption in the channel region. With a tunable channel barrier, this near-IR sensor also features a dynamic photo-response with an extending sensing range up to 60 dB.
关键词： full-silicon NIR photodetector,near-infrared sensing,CMOS process compatible
更新于2025-09-23 15:22:29
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Rate-compatible QC-LDPC codes based on PEXIT
摘要： An improved extension method based on protograph extrinsic information transfer (PEXIT) charts is proposed to design rate-compatible quasi-cyclic low-density parity-check (QC-LDPC) codes with more ?exible rates and better performance. The masking matrix of the highest-rate code can ?rst be constructed column by column to own the lowest decoding threshold. Then, an extension algorithm is proposed to obtain the masking matrices of lower-rate codes with ?exible rates. Finally, the base matrices with small amount of short cycles are designed and the parity-check matrices of rate-compatible QC-LDPC codes are obtained through matrix extension. Simulations show that compared with the existing codes, the proposed codes have more ?exible rates while achieving better performance.
关键词： masking matrix,rate-compatible,PEXIT,decoding threshold,QC-LDPC codes
更新于2025-09-23 15:21:21
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Over 15.7% Efficiency of Ternary Organic Solar Cells by Employing Two Compatible Acceptors with Similar LUMO Levels
摘要： Efficient organic solar cells (OSCs) are fabricated using polymer PM6 as donor, and IPTBO-4Cl and MF1 as acceptors. The power conversion efficiency (PCE) of IPTBO-4Cl based and MF1 based binary OSCs individually arrive to 14.94% and 12.07%, exhibiting markedly different short circuit current density (JSC) of 23.18 mA cm?2 versus 17.01 mA cm?2, fill factor (FF) of 72.17% versus 78.18% and similar open circuit voltage (VOC) of 0.893 V versus 0.908 V. The two acceptors, IPTBO-4Cl and MF1, have similar lowest unoccupied molecular orbital levels, which is beneficial for efficient electron transport in the ternary active layer. The PCE of optimized ternary OSCs arrives to 15.74% by incorporating 30 wt% MF1 in acceptors, resulting from the simultaneously increased JSC of 23.20 mA cm?2, VOC of 0.897 V, and FF of 75.64% in comparison with IPTBO-4Cl based binary OSCs. The gradually increased FFs of ternary OSCs indicate the well-optimized phase separation and molecular arrangement with MF1 as morphology regulator. This work may provide a new viewpoint for selecting an appropriate third component to achieve efficient ternary OSCs from materials and photovoltaic parameters of two binary OSCs.
关键词： organic solar cells,morphology regulators,compatible acceptors,ternary strategy
更新于2025-09-23 15:21:01
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Laser Direct Writing Assisted Fabrication of Skin Compatible Metal Electrodes
摘要： Skin-compatible electrodes have been studied intensively for its application in wearable electronics. To satisfy various deformations of electronic skin, it requires to fabricate a highly conductive, mechanically stable, flexible, and stretchable electrode. Here, a feasible laser direct writing (LDW) process is carried out to fabricate micro-spring structured metal electrodes. The metal electrodes show high conductivity and transparency with sheet resistance of 4.8 ohm per square and at transmittance of 83%. It is worthy of noting that, the metal electrodes have an excellent mechanical–electrical stability, where stretching over 75% and bending over 5000 times induces resistance variance less than 5% and 2%, respectively. The excellent mechanical and electrical behavior of the micro-spring metal electrodes are promising to be useful for wearable electronics. The LDW process may facilitate the design and prototype of the skin compatible metal electrodes in the coming future.
关键词： wearable electronics,skin-compatible electrodes,electro-deposition,laser direct writing
更新于2025-09-23 15:21:01
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Effects of Size and Localized States in Charge Carrier Dynamics and Performance of Solution Processed Graphene Quantum Dots/Silicon Heterojunction near-UV Photodetectors
摘要： Influence of size and localized defect states on photogenerated carrier recombination dynamics, which affects the performance of graphene quantum dots (GQDs) based Si-compatible near-UV heterojunction photodetectors, is reported. GQDs of varying size from ~3.0 to ~8.0 nm have been prepared by a top down method of oxidative cutting of graphene oxide followed by hydrothermal reduction and gradient centrifugation at different speeds. Structural, compositional, photophysical characteristics and photocarrier dynamics of different sized samples have been studied. Spectroscopic features and carrier dynamics of GQDs are effectively controlled by their size and localized surface states, which also determine the average recombination lifetime of photo-generated carriers. Two-terminal vertical heterojunction photodetector devices fabricated using solution processed quantum dots exhibit superior performance over a broad spectrum with a peak response in the near UV (380 nm) region. The device fabricated using ~6.0 nm diameter GQDs displayed highest peak responsivity of 3.5 A/W showing an interesting correlation with carrier dynamics. To our best knowledge, this is the only report in graphene quantum dots or carbon nanostructure genre, showing the direct correlation between size of the quantum dots and localized surface states on photocarrier dynamics and consequential performance of photodetector devices.
关键词： Graphene quantum dots,carrier dynamics,heterojunction,Si-compatible,near-UV photodetectors
更新于2025-09-23 15:21:01
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Multiband Fractal Metasurface with Linear to Linear and Linear to Circular Polarization Conversion
摘要： Mapping the brain centers that mediate the sensory-perceptual processing of visceral afferent signals arising from the body (i.e., interoception) is useful both for characterizing normal brain activity and for understanding clinical disorders related to abnormal processing of visceral sensation. Here, we report a novel closed-system, electrohydrostatically driven master–slave device that was designed and constructed for delivering controlled ?uidic stimulations of visceral organs and inner cavities of the human body within the con?nes of a 3T magnetic resonance imaging (MRI) scanner. The design concept and performance of the device in the MRI environment are described. In addition, the device was applied during a functional MRI (fMRI) investigation of visceral stimulation related to detrusor distention in two representative subjects to verify its feasibility in humans. System evaluation tests demonstrate that the device is MR-compatible with negligible impact on imaging quality [static signal-to-noise ratio (SNR) loss <2.5% and temporal SNR loss <3.5%], and has an accuracy of 99.68% for ?ow rate and 99.27% for volume delivery. A precise synchronization of the stimulus delivery with fMRI slice acquisition was achieved by programming the proposed device to detect the 5 V transistor–transistor logic (TTL) trigger signals generated by the MRI scanner. The fMRI data analysis using the general linear model analysis with the standard hemodynamic response function showed increased activations in the network of brain regions that included the insula, anterior and mid-cingulate and lateral prefrontal cortices, and thalamus in response to increased distension pressure on viscera. The translation from manually operated devices to an MR-compatible and MR-synchronized device under automatic control represents a useful innovation for clinical neuroimaging studies of human interoception.
关键词： automation,fMRI,electrohydrostatic actuation,visceral afferent processing,MR-compatible sensors and actuators
更新于2025-09-23 15:19:57