Optical Logic Research Articles

Vertical 1T’‐WTe2/WS2 Schottky‐Barrier Phototransistor with Polarity‐Switching Behavior

AbstractIn recent years, 2D reconfigurable phototransistors (RPTs) have been applied in broadband convolutional processing, retinomorphic hardware devices, and non‐volatile memorizers. However, there has been a lack of investigation into all‐2D Schottky junctions used in RPT with polarity control behavior. Herein, a vertically stacked multilayered WS2/WTe2 Schottky RPT is reported. The semimetal characteristics of 1T’‐WTe2 is designed to form a built‐in electric field of 69 meV across the heterojunction and WS2 exhibits gate‐tunable characteristics. Therefore, reconfigurable rectifying behavior and self‐driven bidirectional photo response can be achieved. The phototransistor possesses a gate‐tunable rectification ratio ranging from 10−2 to 105, and the corresponding logic half‐wave rectifier shows excellent switchable rectifying states. Under 635 nm illumination, the responsivity can be adjusted from −1325 to 430 mA W−1 with reversed signs. Meanwhile, the maximum power conversion efficiency is 2.84%, and the specific detectivity is 1.47 × 1012 Jones. The device shows both negative and positive responsivity with linear gate dependence within a voltage window of 10 V. Impressively, nonvolatile photovoltaic performance can be demonstrated by reversing short‐circuit current and open‐circuit voltage by applying and releasing pulsed gate voltage. Finally, reconfigurable polarization behavior, single‐pixel imaging, and the optical logic circuit are applicable to the heterostructure.

All-optical 8-QAM signal demodulator based on 2D photonic crystals

This paper proposes a novel two-dimensional photonic crystal-based 8-QAM signal demodulator with a unique combination of nonlinear cavities and line defects. It consists of chalcogenide cylinders arranged in a square lattice against an air background. The proposed structure enables 8-QAM signal demodulation in an all-optical environment. Instead of the photoelectric conversion process, the structure converts the communication signal into the corresponding optical logic signal by distinguishing the intensity and phase differences of the incident light. The performances are analyzed and calculated by using the finite difference time-domain method and the plane wave expansion method. Simulation results illustrate that the maximum response time of the demodulator is 1.067 ps, and the minimum light contrast ratio is 4.39 dB.

A versatile device for implementing the optical quantum gates in multiple degrees of freedom

Optical quantum logic gates are the basic elements for building optical quantum computer. Usually, to implement different logic gates, different optical elements and frameworks are needed. Here, we propose a versatile device that a modified Sagnac interferometer composed of a spatial light modulator (SLM) for implementing multiple optical gates within a classical light framework. We demonstrate that the device can manipulate the polarization and full-field spatial modes of photons to perform multi-qubit logic operations. And versatile conversions between different logic gates are achieved by simply altering the hologram imposed on SLM. Our device shows a good performance in exploring the photon’s full degrees of freedom, which makes it an appropriate candidate for integrated optical computing.

Simultaneous realization of FIR-based multimode optical thermometry and photonic molecular logic gates in Er3+ and Yb3+ co-doped SrTiO3 phosphor

Er3+ and Yb3+ co-doped SrTiO3 phosphors were synthesized and characterized by using the x-ray powder diffraction method, field emission scanning electron microscopy, and photoluminescence spectroscopy. The samples were subjected to thorough luminescence analysis. Under 980 nm infrared (IR) excitation, the (2H11/2,4S3/2) → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ gave green and red emissions, respectively. The up-conversion mechanism of the synthesized phosphor was studied using the power-dependent emission spectra of the SrTiO3:Yb3+, Er3+ phosphor. A rate equation model for the up-conversion mechanism of SrTiO3:Yb3+, Er3+ has been proposed. The temperature-dependent responses of various thermal and non-thermally coupled emission lines of Er3+ ions were used to elaborate the thermal sensing capabilities of the synthesized phosphor. The fluorescence intensity ratio technique was used for the temperature sensing measurements. Sensing measurements were performed in the temperature range of 303 to 618 K. Relative sensitivities of 1.28% K−1, 0.15% K−1, 0.98% K−1, and 0.15% K−1 were observed using various thermally and non-thermally coupled energy levels. Furthermore, using heat and incident IR excitation as physical inputs, we have shown that the synthesized phosphor can also be used to design various elementary logic gates such as AND, INHIBIT, and DEMULTIPLEX photonic molecular logic gates. A high switching ratio of ∼143% for the AND gate and ∼44.8% for the INHIBIT gate was observed using the scheme presented in this manuscript. The synthesized phosphor has the potential to be used as a bifunctional material for optical thermometry and molecular logic devices.

Non-covalent Supramolecular 1D Alternating Copolymer in Crystal toward 2D Anisotropic Photon Transport.

To realize organic integrated optoelectronic circuits, there is a need for anisotropic optical waveguides at the micro/nanoscale. Anisotropic alignment of one-dimensional (1D)-ordered supramolecular structures composed of light-emissive π-conjugated molecules in a crystal may meet the requirements of such waveguides. Here, we designed a bipyridyl-appended acrylonitrile-based π-conjugated molecule 1, which produced a 1D supramolecular polymer constructed through non-covalent bonding between a lone pair in 1 and a σ-hole in 1,4-diiodo-2,3,5,6-tetrafluorobenzene 2. The 1D copolymer of 1 and 2 is aligned horizontally with the two-dimensional (2D) crystal surface because of the angle-controlled supramolecular synthons. As a result of control over the non-covalent bonding direction, anisotropic photoluminescence and photon transport (optical waveguiding) characteristics are realized by orienting the transition dipole moment horizontally with respect to the 2D surface. Compared with the loss coefficient αL =52dBcm-1 for the long-axis direction of the 2D platelet cocrystal, a very large difference of αS =2111dBcm-1 is present in the crystal short-axis direction. The anisotropic waveguiding ability, αL/αS, is estimated to be 41, which is more than an order of magnitude greater than previously reported 2D platelet crystal waveguides. This supramolecular synthon provides an approach to designing anisotropic photon transporters and highly regulated optical logic circuits.

Achieving Ultralong Room-Temperature Phosphorescence in Two-Dimensional Metal Halide Perovskites by Alkyl Chain Engineering.

Two-dimensional (2D) metal halide perovskites with highly efficient ultralong room-temperature phosphorescence (URTP) are rare due to their uncertain structures and complicated intermolecular interactions. Herein, by varying the alkyl length of organic units, we synthesized two single-component 2D metal hybrid perovskites, i.e., B-MACC and B-EACC, with obvious URTP emission. In particular, B-EACC exhibits a green-yellow URTP emission with an ultralong lifetime (579 ms) and a high efficiency (14.86%). It is found that the molecular packing of B-EA+ cations because of the presence one more carbon in the alkyl chain affords strong hydrogen bonding and π-π stacking interactions, which immobilizes and reduces the triplet exciton quenching. Moreover, B-MACC and B-EACC with space-time dual-resolved characteristics can be utilized for dynamic information encryption and optical logic gate applications. This study is the first to disclose the relation between the characteristics of molecular packing and the resultant URTP of 2D metal hybrid perovskites, significantly advancing the development of next-generation URTP materials for versatile applications.

Multi-level optical memory with logical operation modulated by surface barrier in a single CH3NH3PbI3 perovskite micro/nanowire device

CH3NH3PbI3 is a potential candidate for optical information storage because of its excellent photoelectric response and hysteresis effect. However, the interface mechanism of the CH3NH3PbI3-based memory is still controversial, and the precise control of the resistive switching effect requires an effective method. Here, single CH3NH3PbI3 micro/nanowire devices with symmetric Ag electrodes were constructed. The role of the reversible redox reaction on the Ag electrode to modulate the interfacial barrier has been proposed, and the hysteresis behavior of the device can be precisely controlled by adjusting the illumination intensity and bias polarity. For example, when strong light and high voltage are applied at the same time, the device exhibits a symmetrical negative differential resistance effect; after being subjected to strong light and high voltage, the device exhibits a bipolar resistive switching effect, and the polarity of the large voltage determines the I-V curve wrapping way. On this basis, the device obtains multi-level optical storage and logic operation functions. This work provides a new way to understand the synergistic memory effect of light and bias on halide perovskite, which is expected to be further applied in the integrated field of optical nonvolatile memory and logical.

One‐dimensional molecular co‐crystal alloys capable of full‐color emission for low‐loss optical waveguide and optical logic gate

AbstractThe luminescence color of molecule‐based photoactive materials is the key to the applications in lighting and optical communication. Realizing continuous regulation of emission color in molecular systems is highly desirable but still remains a challenge due to the individual emission band of purely organic molecules. Herein, a novel alloy strategy based on molecular co‐crystals is reported. By adjusting the molar ratio of pyrene (Py) and fluorathene (Flu), three types of molecular co‐crystal alloys (MCAs) assemblies are prepared involving Py‐Flu‐OFN‐x%, Py‐Flu‐TFP‐x%, Py‐Flu‐TCNB‐x%. Multiple energy level structure and Förster resonance energy transfer (FRET) process endow materials with tunable full‐spectra emission color in visible region. Impressively, these MCAs and co‐crystals can be successfully applied to low optical loss waveguide and optical logic gate by virtue of all‐color luminescence from blue across green to red, together with smooth surface of one‐dimensional microrods, which show promising applications as continuous light emitters for advance photonics applications.

Realizing efficient emission and triple‐mode photoluminescence switching in air‐stable tin(IV)‐based metal halides via antimony doping and rational structural modulation

AbstractRecently, many lead‐free metal halides with diverse structures and highly efficient emission have been reported. However, their poor stability and single‐mode emission color severely limit their applications. Herein, three homologous Sb3+‐doped zero‐dimensional (0D) air‐stable Sn(IV)‐based metal halides with different crystal structures were developed by inserting a single organic ligand into SnCl4 lattice, which brings different optical properties. Under photoexcitation, (C25H22P)SnCl5@Sb·CH4O (Sb3+−1) does not emit light, (C25H22P)2SnCl6@Sb‐α (Sb3+−2α) shines bright yellow emission with a photoluminescence quantum yield (PLQY) of 92%, and (C25H22P)2SnCl6@Sb‐β (Sb3+−2β) exhibits intense red emission with a PLQY of 78%. The above three compounds show quite different optical properties should be due to their different crystal structures and the lattice distortions. Particularly, Sb3+−1 can be successfully converted into Sb3+−2α under the treatment of C25H22PCl solution, accompanied by a transition from nonemission to efficient yellow emission, serving as a “turn‐on” photoluminescence (PL) switching. Parallelly, a reversible structure conversion between Sb3+−2α and Sb3+−2β was witnessed after dichloromethane or volatilization treatment, accompanied by yellow and red emission switching. Thereby, a triple‐mode tunable PL switching of off–onI–onII can be constructed in Sb3+‐doped Sn(IV)‐based compounds. Finally, we demonstrated the as‐synthesized compounds in fluorescent anticounterfeiting, information encryption, and optical logic gates.

Electro-optical hybrid full-adder based on surface plasmon polaritons

Optical computing has advantages such as high speed and anti-electromagnetic interference, and the adder is the key component that composes optical computing units. This paper proposes an electro-optic hybrid full-adder based on surface plasmon polaritons, which combines the advantages of flexible circuit control, storability, high speed and electromagnetic interference immunity in optical computing. By using surface plasmon polariton technology, the limitation of optical diffraction is overcome, and the size of the full-adder is limited to 26.7 µm2, which improves the integration of more logical computing units on a single chip. By utilizing the MOS structure, the addition operation function of optical logic is controlled, thus reducing the junction capacitance area and improving the operation speed. The feasibility of the design scheme was verified through FDTD simulation experiments, and the correctness of the logic was achieved when the transmission rate exceeded 200 Gbit. This research provides a theoretical and practical reference for the electro-optical hybrid full addition operation of surface plasmon polaritons.

Intrinsic photomixing detector based on amorphous silicon for envelope mixing of optical signals

In this work, a promising device for direct optical envelope mixing, the Intrinsic Photomixing Detector (IPD) based on hydrogenated amorphous silicon, is reported. The IPD directly generates a photocurrent proportional to the nonlinear mixing of two optical modulation envelope functions. Experiments illustrate efficient mixing in the visible range at low light levels down to ϕ1 = 4.36 mW/cm2 (444 nm) and ϕ2 = 1.03 mW/cm2 (636 nm). Modulation frequencies exceeding the MHz range are demonstrated. Electro-optical simulations identify defect-induced electrical field screening within the absorber to cause the nonlinear mixing process, opening-up the opportunity to tailor devices toward application-specific requirements. The IPD functionality paves the way toward very simple but high-performance photodetectors for 3D imaging and ranging for direct optical convolutional sensors or for efficient optical logic gates. Using amorphous silicon provides a photodetector material base, which can easily be integrated on top of silicon electronics, enabling fill factors of up to 100%.

Encryption Using Optical Pseudo-Random Binary Sequence Based on Optical Logic Gate

In this paper, we propose a scheme for high-speed all-optical Pseudo-Random Binary Sequence (PRBS) generator and use it for generating keystream for encryption. This PRBS generator design is based on Linear Feedback Shift Registers (LFSR) and optical XOR and AND gates. The optical logical gates are based on quantum dot-semiconductor optical amplifier Mach-Zehnder interferometer (QD-SOA-MZI). With two photon absorption (TPA) in quantum dot-semiconductor optical amplifier (QD-SOA), this kind of optical logic gates performs well when processing data in an ultra-fast timescale and therefore able to function as high speed PRBS generator. Result shows that it’s possible for this scheme to realize all-optical encryption and decryption at high process rate up to 320 Gb/s. We simulated different ways of generating keystream with schemes such as cascaded generator, parallel generator and alternating step generator. These generators use more than one LFSR. Result shows that the schemes we use can function as stable and complex keystream generators.

Design of All-Optical Subtractors Utilized with Plasmonic Ring Resonators for Optical Computing

In this paper, a novel plasmonic all-optical half-subtractor and full-subtractor are designed for optical computing. The structure of plasmonic subtractors consists of a metal–insulator–metal (MIM) waveguide and rectangular ring resonators covered by a graphene layer. Due to the nonlinear optical properties of graphene, the states of the plasmonic resonators can be controlled by the pump intensity of a pump beam focused on the graphene layer. The resonators can work as all-optical switches with an ultra-fast response time to constitute optical logic devices according to the directed logic mechanism. A finite-difference time-domain method is utilized to numerically investigate the transmission of the output signals which represent the results of subtraction operations. Simulation results obtained indicate that the proposed plasmonic devices have the ability to implement half-subtraction and full-subtraction with a small feature size and fast response time, and provide a new concept and method for the design and realization of optical computing devices.

Optical Logic Gates Based on Z-Shaped Silicon Waveguides at 1.55 μm.

In the last ten years, silicon photonics has made considerable strides in terms of device functionality, performance, and circuit integration for a variety of practical uses, including communication, sensing, and information processing. In this work, we theoretically demonstrate a complete family of all-optical logic gates (AOLGs), including XOR, AND, OR, NOT, NOR, NAND, and XNOR, through finite-difference-time-domain simulations using compact silicon-on-silica optical waveguides that operate at 1.55 μm. Three slots, grouped in the shape of the letter Z, make up the suggested waveguide. The function of the target logic gates is based on constructive and destructive interferences that result from the phase difference experienced by the launched input optical beams. These gates are evaluated against the contrast ratio (CR) by investigating the impact of key operating parameters on this metric. The obtained results indicate that the proposed waveguide can realize AOLGs at a higher speed of 120 Gb/s with better CRs compared to other reported designs. This suggests that AOLGs could be realized in an affordable manner and with improved outcomes to enable the satisfaction of the current and future requirements of lightwave circuits and systems that critically rely on AOLGs as core building elements.

Self-Assembled π-Conjugated Organic/Polymeric Microresonators and Microlasers

Optical microresonators are minute dielectric objects that are utilized as essential components in micrometer-scale light and laser sources, optical integrated circuits, micro-displays, chemo- and biosensors, and so forth. Particularly, microresonators made from organic and polymeric materials find unique applications owing to its structural flexibility, color tunability, and functionality with simple fabrication process, low cost and low energy consumption. In this Account, we highlight our recent progress on the organic/polymeric microresonators made through precisely controlled self-assembly process. The microstructures display novel optical functions such as circularly polarized luminescence emission, lasers, light energy harvesters, optical gate operations, optical memories and authentications, and optical sensing for environmental changes and mechanical forces. Our methodology for the precise design and control of organic and polymeric microstructures, will bridge between nanometer-scale supramolecular chemistry and bulk materials and will pave the way toward flexible optical and laser applications. Precise control of microstructures by self-assembly of π-conjugated organic molecules and polymers offers materials with sophisticated optical functions such as optical resonators and lasers, circularly polarized luminescence emitters, optical logic gate operations, optical memories, and light energy harvesting, which are utilized as optical sensors for environmental changes and mechanical forces.

Design of All-Optical Logic Half-Adder Based on Photonic Crystal Multi-Ring Resonator

In this paper, a novel design of an all-optical half-adder (HA) based on two two-ring resonators in a two-dimensional square-lattice photonic crystal (PC) structure without nonlinear materials is proposed. The all-optical HA comprises AND and XOR gates where each gate is composed of cross-shaped waveguides and two-ring resonators in a 2D square-lattice PC that are filled with silicon (Si) rods in silica (SiO2). The AND and XOR gates are analyzed and simulated using plane-wave expansion (PWE) and finite-difference time-domain (FDTD) methods. Simulation results show that light guiding inside the device functions as AND and XOR gates. Thus, the proposed device has the potential for use in optical arithmetic logic units for digital computing circuits. The structure comprises an optical AND gate and an optical XOR gate that were designed to work at the C-band spectrum. Results show that there is a clear distinction between logic states 1 and 0 with a narrow power range that leads to a better robust decision on the receiver side for minimized logic errors in the photonic decision circuit. Thus, the proposed HA can be a key component for designing a photonic arithmetic logic unit.

Magnetically tunable ultralow threshold optical bistability by exciting LRSPR in InAs/graphene layers at the terahertz region.

With the experimental corroboration employing a transfer matrix method, an analytical observation of optical bistability using long-range surface plasmon resonance (LRSPR) through the external magnetic field is presented for a very low threshold value. The proposed analytical method has been verified with the reported experimental data provided by Liu etal. [Curr. Appl. Phys.29, 66 (2021)1567-173910.1016/j.cap.2021.06.003]. Now theoretical analysis is further extended in the proposed multilayered structure comprising an InAs layer sandwiched between two graphene layers, whose electromagnetic response at 2THz can be regulated by employing a magnetic field and may tune the optical bistability without modifying the geometry or the characteristics of the structure. The observed threshold intensity for the switch-up is 6.6615×104 W/c m 2 at 0.001T; thus, this analytical approach is able to achieve 2 orders lower threshold for magnetically tunable upswitching of the optical bistable process. This suggested magnetically adjustable optical bistable arrangement gives a possibility for the comprehension of optical logic gates, optic memory, opto-transistors, and switches at a low switching threshold due to extraordinary features of the composite layers due to local field amplification of the graphene layer.

Parallelized and Cascadable Optical Logic Operations by Few-Layer Diffractive Optical Neural Network

Optical computing has gained much attention due to its high speed, low energy consumption, and the fact that it is naturally parallelizable and multiplexable, etc. Single-bit optical logic gates based on a four-hidden-layer diffractive optical neural network (DONN) have been demonstrated with paired apertures. Here, we show a parallel-logic operation strategy based on two-hidden-layer DONN, showcasing their efficiency by multiple-bit (up to 16-bit) optical logic (e.g., NAND) operations. In addition, we demonstrate how NAND-DONN units can be utilized to achieve NOR and AND operations by flipping and cascading the DONN.

Experimental Realization of Topologically‐Protected All‐Optical Logic Gates Based on Silicon Photonic Crystal Slabs

AbstractAs the field of topological photonics has developed over the past 10 years, it has been proven that the combination of topology and photons is very beneficial to the design of robust optical devices against some disturbances. However, most of the work on robust optical logic devices stays at the theoretical level. There are very few topologically‐protected logic devices fabricated in experiments. Here, the experimental fabrication of a series of topologically‐protected all‐optical logic gates is reported. Seven topologically‐protected all‐optical logic gates (OR, XOR, NOT, XNOR, NAND, NOR, and AND) are fabricated on silicon photonic platforms, which show strong robustness even if some disorders exist. These robust logic devices are potentially applicable in future optical signal processing and computing applications.

Spatial modulation of refractive index in a dense atomic ensemble using Laguerre–Gaussian beams

We propose a scheme to investigate the spatial modulation of the refractive index in a dense atomic ensemble under the action of the Laguerre–Gaussian (LG) beams. Theoretical derivations based on a density-matrix approach associated with numerical simulations are utilized to study the behaviors of the index of refraction, showing that the azimuthal and radial mode indices (i.e., l 2 and p 2) of the LG beams significantly affect the real and imaginary parts of the refractive index. To be specific, the number of the dispersive peaks is determined by ( p 2 + 1 ) | l 2 |, and there are 2 | l 2 | lossless petals in conjunction with p 2 concentric absorption rings centered on the vortex center. Furthermore, by tuning the phase values of the electric and magnetic components of the electromagnetic field, the index of refraction can be drastically tuned from negative to zero to positive and accompanied by periodic absorption and amplification. This investigation provides a powerful tool for manipulating the index of refraction through a nonlinear interaction between atoms and the vortex beams and suggests potential applications in optical switching, logic gates, and optical storage with spatially varying refractive indices.