All-optical computing based on convolutional neural networks

The rapid development of information technology has fueled an ever-increasing demand for ultrafast and ultralow-en-ergy-consumption computing.Existing computing instruments are pre-dominantly electronic processors,which use elec-trons as information carriers and possess von Neumann architecture featured by physical separation of storage and pro-cessing.The scaling of computing speed is limited not only by data transfer between memory and processing units,but also by RC delay associated with integrated circuits.Moreover,excessive heating due to Ohmic losses is becoming a severe bottleneck for both speed and power consumption scaling.Using photons as information carriers is a promising alternative.Owing to the weak third-order optical nonlinearity of conventional materials,building integrated photonic com-puting chips under traditional von Neumann architecture has been a challenge.Here,we report a new all-optical comput-ing framework to realize ultrafast and ultralow-energy-consumption all-optical computing based on convolutional neural networks.The device is constructed from cascaded silicon Y-shaped waveguides with side-coupled silicon waveguide segments which we termed“weight modulators”to enable complete phase and amplitude control in each waveguide branch.The generic device concept can be used for equation solving,multifunctional logic operations as well as many other mathematical operations.Multiple computing functions including transcendental equation solvers,multifarious logic gate operators,and half-adders were experimentally demonstrated to validate the all-optical computing performances.The time-of-flight of light through the network structure corresponds to an ultrafast computing time of the order of several picoseconds with an ultralow energy consumption of dozens of femtojoules per bit.Our approach can be further expan-ded to fulfill other complex computing tasks based on non-von Neumann architectures and thus paves a new way for on-chip all-optical computing.

Resorcinol-formaldehyde resin-based porous carbon spheres with high CO_2 capture capacities

Porous carbon spheres are prepared by direct carbonization of potassium salt of resorcinol-formaldehyde resin spheres, and are investigated as COadsorbents. It is found that the prepared carbon materials still maintain the typical spherical shapes after the activation, and have highly developed ultra-microporosity with uniform pore size, indicating that almost the activation takes place in the interior of the polymer spheres. The narrow-distributed ultra-micropores are attributed to the "in-situ homogeneous activation"effect produced by the mono-dispersed potassium ions as a form of -OK groups in the bulk of polymer spheres. The CS-1 sample prepared under a KOH/resins weight ratio of 1 shows a very high COcapture capacity of 4.83 mmol/g and good CO/Nselectivity of7-45. We believe that the presence of a welldeveloped ultra-microporosity is responsible for excellent COsorption performance at room temperature and ambient pressure.

Mid-infrared lasers on silicon operating close to room temperature

Mid-infrared(MIR)wavelength is strategical important band for thermal imaging,remote sensing,free space communication,etc.Recent progresses in integrated mid-infrared photonics on silicon offer an alternative platform for manufacturing low-cost and high-performance MIR system in high volumes.However,light source has always been a grand challenge for integrated photonics and it is even harder to monolithically integrate MIR laser on silicon which could be operated at room temperature.

Nonlinear optical properties of integrated GeSbS chalcogenide waveguides

In this paper, we report the experimental characterization of highly nonlinear Ge Sb S chalcogenide glass waveguides.We used a single-beam characterization protocol that accounts for the magnitude and sign of the real and imaginary parts of the third-order nonlinear susceptibility of integrated Ge23 Sb7 S70(GeSbS) chalcogenide glass waveguides in the near-infrared wavelength range at λ =1580 nm. We measured a waveguide nonlinear parameter of 7.0±0.7 W^(-1)· m(-1), which corresponds to a nonlinear refractive index of n_2=0.93±0.08 × 10^(-18) m^2∕W,comparable to that of silicon, but with an 80 times lower two-photon absorption coefficient βTPA=0.010± 0.003 cm∕GW, accompanied with linear propagation losses as low as 0.5 dB/cm. The outstanding linear and nonlinear properties of Ge Sb S, with a measured nonlinear figure of merit FOMTPA=6.0 ±1.4 at λ =1580 nm, ultimately make it one of the most promising integrated platforms for the realization of nonlinear functionalities.

Electrically programmable phase-change photonic memory for optical neural networks with nanoseconds in situ training capability

Optical neural networks (ONNs), enabling low latency and high parallel data processing withoutelectromagnetic interference, have become a viable player for fast and energy-efficient processing andcalculation to meet the increasing demand for hash rate. Photonic memories employing nonvolatile phase-change materials could achieve zero static power consumption, low thermal cross talk, large-scale, andhigh-energy-efficient photonic neural networks. Nevertheless, the switching speed and dynamic energyconsumption of phase-change material-based photonic memories make them inapplicable for in situ training.Here, by integrating a patch of phase change thin film with a PIN-diode-embedded microring resonator,a bifunctional photonic memory enabling both 5-bit storage and nanoseconds volatile modulation wasdemonstrated. For the first time, a concept is presented for electrically programmable phase-changematerial-driven photonic memory integrated with nanosecond modulation to allow fast in situ training and zerostatic power consumption data processing in ONNs. ONNs with an optical convolution kernel constructedby our photonic memory theoretically achieved an accuracy of predictions higher than 95% when testedby the MNIST handwritten digit database. This provides a feasible solution to constructing large-scalenonvolatile ONNs with high-speed in situ training capability.

大尺寸高端显示器件用薄膜晶体管Al–Mo复合电极坡度的形成过程与可控调节

栅极坡度角(PA)对薄膜晶体管(TFT)性能和良率具有重要影响,如何将坡度角调节到合适的范围是TFT量产中关键技术之一.本文以大尺寸高端显示器件用a-Si TFT的Al/Mo、Mo/Al/Mo电极在磷酸系溶液下刻蚀得到的坡度角为研究对象,探究了膜层结构、Mo厚度、刻蚀时间对坡度角的影响.结果表明:在Al/Mo结构中,随着顶Mo厚度增加,Al与光刻胶之间的间隙增加,刻蚀液更易侵入,侧向刻蚀增强,坡度角减小;在Mo/Al/Mo三层电极结构中,随着底Mo厚度增加,底Mo和中间临近的Al侧壁发生电偶腐蚀,Al侧壁上形成氧化物钝化层,Al刻蚀速率减慢,坡度角变小.水池效应将导致刻蚀液残留在电极底部,阻碍新鲜刻蚀液与底部接触,底部刻蚀速率低于顶部;故当刻蚀时间延长时,底部和顶部刻蚀速率差进一步增大,导致坡度角减小.得到了Mo/Al/Mo坡度角与顶Mo和底Mo厚度回归方程,为调节坡度角和优选Mo厚度提供了依据.此电极坡度角的调节技术可为确保TFT的良率和性能提供参考.

有机卤素键晶体及其在光电子学中的应用

有机卤素共晶是由两个或者更多不同组分通过碳卤键构成的.因其多样化的化学物理特性,及在有机光电子学领域的潜在应用价值,有机卤素共晶引起了研究者的广泛关注.本综述文章中,我们简单总结了有机卤键共晶的制备方法和在光电子器件领域应用的最新进展.此外,我们还讨论了目前有机卤键共晶的研究方向及面临的技术挑战,同时对有机卤键共晶的进一步研究和应用前景进行了展望.

Graphene-based all-optical modulators

All-optical devices,which are utilized to process optical signals without electro-optical conversion,play an essential role in the next generation ultrafast,ultralow power-consumption optical information processing systems.To satisfy the performance requirement,nonlinear optical materials that are associated with fast response,high nonlinearity,broad wavelength operation,low optical loss,low fabrication cost,and integration compatibility with optical components are required.Graphene is a promising candidate,particularly considering its electrically or optically tunable optical properties,ultrafast large nonlinearity,and high integration compatibility with various nanostructures.Thus far,three all-optical modulation systems utilize graphene,namely free-space modulators,fiber-based modulators,and on-chip modulators.This paper aims to provide a broad view of state-of-the-art researches on the graphene-based all-optical modulation systems.The performances of different devices are reviewed and compared to present a comprehensive analysis and perspective of graphene-based all-optical modulation devices.

Construction of porous covalent organic polymer as photocatalysts for RhB degradation under visible light

In the present work,a novel porous,and chemically stable amine-based covalent organic polymer(POP-1) was designed and synthesized under solvothermal conditions.The porosity,crystallinity,chemical stability,electrochemical properties,and diffuse reflectance of POP-1 were investigated via N_2 sorption experiment,power X-ray diffraction,thermogravimetric analysis,cyclic voltammetry,and ultraviolet visible near infrared spectrometry,respectively.POP-1 exhibits good chemical stability in both acidic and alkaline aqueous solutions,as well as in organic solvents.Undoped POP-1 can be directly used as a photocatalyst for rhodamine B irradiation degradation under light-emitting diode and natural light.The E_a of POP-1 for RhB degradation is 82.37 kJ/mol.Furthermore,POP-1 can be reused as a catalyst in RhB degradation without degraded catalytic activity.

High spatial and temporal resolution synthetic aperture phase microscopy

A new optical microscopy technique,termed high spatial and temporal resolution synthetic aperture phase microscopy(HISTR-SAPM),is proposed to improve the lateral resolution of wide-field coherent imaging.Under plane wave illumination,the resolution is increased by twofold to around 260 nm,while achieving millisecond-level temporal resolution.In HISTR-SAPM,digital micromirror devices are used to actively change the sample illumination beam angle at high speed with high stability.An off-axis interferometer is used to measure the sample scattered complex fields,which are then processed to reconstruct high-resolution phase images.Using HISTR-SAPM,we are able to map the height profiles of subwavelength photonic structures and resolve the period structures that have 198 nm linewidth and 132 nm gap(i.e.,a full pitch of 330 nm).As the reconstruction averages out laser speckle noise while maintaining high temporal resolution,HISTR-SAPM further enables imaging and quantification of nanoscale dynamics of live cells,such as red blood cell membrane fluctuations and subcellular structure dynamics within nucleated cells.We envision that HISTR-SAPM will broadly benefit research in material science and biology.

基于有机微/纳米晶体形貌和光学性质的可控调制

基于有机小分子的低维有机微纳米晶体因在有机场效应晶体管、电化学传感器、太阳能电池等领域的潜在应用而备受关注.本文从分子聚集模式、形貌调控、光学性质调控等方面综述了近十年来有机微纳米晶体的研究进展.首先介绍了分子聚集体模式对有机微/纳米晶体物理化学性质(进而对其光学性质和形貌)的潜在影响,接着总结了形貌调控的多种方法和详细过程.此外,我们还探究了导致有机微/纳米晶体不同光学性质的机理和调控方法.最后,我们从可控性和分子结构-聚集行为-微/纳米结构-光学性质之间的不定量关系提出了有机微/纳米晶体领域目前面临的挑战,展望了具有可调形貌和光学特性的有机晶体应用于实际光电器件中的前景.这篇综述将促进有机微/纳米晶体的可控合成及结构与光学性能关系的基础研究和实际应用方面的发展.

Monolithically integrated stretchable photonics

Mechanically stretchable photonics provides a new geometric degree of freedom for photonic system design and foresees applications ranging from artificial skins to soft wearable electronics.Here we describe the design and experimental realization of the first single-mode stretchable photonic devices.These devices,made of chalcogenide glass and epoxy polymer materials,are monolithically integrated on elastomer substrates.To impart mechanical stretching capability to devices built using these intrinsically brittle materials,our design strategy involves local substrate stiffening to minimize shape deformation of critical photonic components,and interconnecting optical waveguides assuming a meandering Euler spiral geometry to mitigate radiative optical loss.Devices fabricated following such design can sustain 41%nominal tensile strain and 3000 stretching cycles without measurable degradation in optical performance.In addition,we present a rigorous analytical model to quantitatively predict stressoptical coupling behavior in waveguide devices of arbitrary geometry without using a single fitting parameter.

Free-spectral-range-free filters with ultrawide tunability across the S+C+L band

Optical filters are essential parts of advanced optical communication and sensing systems.Among them,the ones with an ultrawide free spectral range(FSR)are especially critical.They are promising to provide access to numerous wavelength channels highly desired for large-capacity optical transmission and multipoint multiparameter sensing.Present schemes for wide-FSR filters either suffer from limited cavity length or poor fabrication tolerance or impose an additional active-tuning control requirement.We theoretically and experimentally demonstrate a filter that features FSR-free operation capability,subnanometer optical bandwidth,and acceptable fabrication tolerance.Only one single deep dip within a record-large waveband(S+C+L band)is observed by appropriately designing a side-coupled Bragg-grating-assisted Fabry–Perot filter,which has been applied as the basic sensing unit for both the refractive index and temperature measurement.Five such basic units are also cascaded in series to demonstrate a multichannel filter.This work provides a new insight to design FSR-free filters and opens up a possibility of flexible large-capacity integration using more wavelength channels,which will greatly advance integrated photonics in optical communication and sensing.

Angle-selective perfect absorption with two-dimensional materials

Two-dimensional(2D)materials have great potential in photonic and optoelectronic devices.However,the relatively weak light absorption in 2D materials hinders their application in practical devices.Here,we propose a general approach to achieve angleselective perfect light absorption in 2D materials.As a demonstration of the concept,we experimentally show giant light absorption by placing large-area single-layer graphene on a structure consisting of a chalcogenide layer atop a mirror and achieving a total absorption of 77.6%in the mid-infrared wavelength range(~13μm),where the graphene contributes a record-high 47.2%absorptivity of mid-infrared light.Construction of such an angle-selective thin optical element is important for solar and thermal energy harvesting,photo-detection and sensing applications.Our study points to a new opportunity to combine 2D materials with photonic structures to enable novel device applications.

Precise Synthesis of Organic Heterostructures via the Synergy Approach of Polymorphism and Cocrystal Engineering for Optical Applications

Organic heterostructures that can integrate the physiochemical properties of two or more substances have atracted widespread attention in the field of optoelectronics.However,the epitaxial growth process between different organic material molecules is unpredictable,and the precise synthesis of organic heterostructures is stll particularly challenging.Herein,through the synergy approach of polymorphism and cocrystal engineering,a series of organic branched heterostructures have been successfully prepared.Interestingly,by simply adjusting the solvent ratio,different crystalline phases of perylene microplates can be epitaxilly grown on the perylene-OFN cocrystal microwires,which provides a feasible approach for the preparation of organic heterostructures.Meanwhile,these as-prepared organic branched heterostructures can realize multi-channel and multi-color emission,and act as optical logic gates,which promotes the multifunctional integrated optoelectronics.

3D integrated photonics platform with deterministic geometry control

3D photonics promises to expand the reach of photonics by enabling the extension of traditional applications to nonplanar geometries and adding novel functionalities that cannot be attained with planar devices.Available material options and device geometries are,however,limited by current fabrication methods.In this work,we pioneer a method that allows for placement of integrated photonic device arrays at arbitrary predefined locations in 3D using a fabrication process that capitalizes on the buckling of a 2D pattern.We present theoretical and experimental validation of the deterministic buckling process,thus demonstrating implementation of the technique to realize what we believe to be the first fully packaged 3D integrated photonics platform.Application of the platform for mechanical strain sensing is further demonstrated.

Self-Driven Photo-Polarized Water Molecule-Triggered Graphene-Based Photodetector

Flowing water can be used as an energy source for generators,providing a major part of the energy for daily life.However,water is rarely used for information or electronic devices.Herein,we present the feasibility of a polarized liquid-triggered photodetector in which polarized water is sandwiched between graphene and a semiconductor.Due to the polarization and depolarization processes of water molecules driven by photogenerated carriers,a photo-sensitive current can be repeatedly produced,resulting in a high-performance photodetector.The response wavelength of the photodetector can be fine-tuned as a result of the free choice of semiconductors as there is no requirement of lattice match between graphene and the semiconductors.Under zero voltage bias,the responsivity and specific detectivity of Gr/NaCl(0.5 M)W/N-GaN reach values of 130.7 mA/W and 2.3×10^(9)Jones under 350 nm illumination,respectively.Meanwhile,using a polar liquid photodetector can successfully read the photoplethysmography signals to produce accurate oxygen blood saturation and heart rate.Compared with the commercial pulse oximetry sensor,the average errors of oxygen saturation and heart rate in the designed photoplethysmography sensor are~1.9%and~2.1%,respectively.This study reveals that water can be used as a high-performance photodetector in informative industries.