Optical Gate Research Articles

Programmable Parallel Optical Logic Gates on a Multimode Waveguide Engine

Optical logic gates have been proposed and demonstrated on a function programmable waveguide engine constructed using buried silicon nitride waveguides in polymer and a set of thermal electrodes. The device can perform logic AND or OR operations for the input signals A and B, each containing two bits of information, in parallel. The input signals, in the form of binary current values in the electronic domain, are applied to a subset of thermal electrodes, while the computed logic states are converted to optical intensity variations at the single-mode waveguide outputs. The rest of the electrodes work as weights to define the device function, either AND or OR, by adjusting the light interference in the multimode waveguide through thermo-optic effect. Simulations were first performed to reveal the nonlinear response of the received light intensity with respect to the applied current, thus allowing complex and effective manipulation of the light field on the waveguide engine. After chip fabrication and system integration, 65,536 experiments were performed automatically. The data are fed into a sorting program to find the valid settings that satisfy the respective truth table out of the 283,852,800 possible input/weight/output combinations. Four cases of operations for the AND and OR gates are presented in the end, with different bar and contrast values. This simple, low-cost yet powerful engine may be further developed for applications in on-chip photonic computing and signal switching.

2D- PhC based all optical AND, OR and EX-OR logic gates with high contrast ratio operating at C band

In this article, photonic crystal (PhC) based all-optical logic gates, namely AND, OR and EX-OR have been explored and their characteristics are reported. Two-dimensional (2D) PhC based logic gates are proposed using a hexagonal lattice with T-shaped structure by incorporating line defects. The total size of the device is 84 µm2 and it operates at a wavelength of 1550 nm (C band). The designed optical logic gates are investigated using 2D finite difference time domain simulators by means of the plane wave expansion method. Parameters, such as response time and contrast ratio of the designed all-optic logic gates, are analyzed. The proposed AND, OR and EX-OR logic gates offer a contrast ratio of 14.48 dB, 14.57 dB and 12.9 dB respectively with, in order, response times of 0.159 ps, 0.168 ps and 0.1672 ps. The designed logic gates work in the third optical window as they are operating at the 1550 nm wavelength. To specify the performance of the proposed logic gates, their field distribution has been determined and is exhibited. The designed logic gates are suitable for use in photonic integrated circuits, all optical computing and optical sensing applications.

On‐Chip Chiral Mode Switching by Encircling an Exceptional Point in an Anti‐Parity‐Time Symmetric System

AbstractDynamically encircling the exceptional point (EP) of an anti‐parity‐time (anti‐PT) symmetric system can achieve chiral mode switching between symmetry‐broken eigenmodes, which is especially important for developing nanophotonic devices. However, the realization of anti‐PT‐symmetric systems on a chip still remains significantly challenging as precisely controlling the parameters of nanophotonic structures is difficult. Herein, a novel anti‐PT‐symmetric system is designed and constructed on a silicon‐on‐insulator chip by taking advantage of subwavelength gratings to help engineer nanophotonic structures. Consequently, on‐chip chiral switching between symmetry‐broken eigenmodes is experimentally realized by dynamically encircling the EP in parametric space of the proposed anti‐PT‐symmetric system. Moreover, the achieved chiral mode switching exhibits high output power ratios (≥ 6.4 dB) at 1550 nm, wide‐band response that covers C‐band completely, and great thermal stability up to 90 °C, which indicate desirable performance features for practical applications in optical communication. This study paves an avenue for realizing on‐chip chiral switching between symmetry‐broken modes, which shows great promise for developing nanophotonic devices, such as optical switching, logic gates, and isolators, in optical telecommunication bands.

Realization of optical logic gates using on-chip diffractive optical neural networks

Optical computing is highly desired as a potential strategy for circumventing the performance limitations of semiconductor-based electronic devices and circuits. Optical logic gates are considered as fundamental building blocks for optical computation and they enable logic functions to be performed extremely quickly without the generation of heat and crosstalk. Here, we discuss the design of a multi-functional optical logic gate based on an on-chip diffractive optical neural network that can perform AND, NOT and OR logic operations at the wavelength of 1.55 µm. The wavelength-independent operation of the multi-functional logic gate at seven wavelengths (over a bandwidth of 60 nm) is also studied which paves the way for wavelength division multiplexed parallel computation. This simple, highly-integrable, low-loss, energy-efficient and broadband optical logic gate provides a path for the development of high-speed on-chip nanophotonic processors for future optical computing applications.

Intense green photoluminescence and upconversion-based intrinsic optical bistability in Ho3+/Yb3+ codoped CaSc2O4 and upconversion in Ho3+/Yb3+ codoped CaY2O4 phosphors

The present study details the downshifting, frequency upconversion and intrinsic optical bistability in CaSc2O4:Ho3+/Yb3+ and upconversion in CaY2O4:Ho3+/Yb3+ phosphors synthesized by a complex-based precursor solution method. The X-ray powder diffraction confirms the formation of highly crystalline phosphors with pure orthorhombic phase. Fourier transform infrared studies of synthesized phosphors show vibrational bands due to the presence of Ca–O, Sc–O and Y–O groups. The diffuse reflectance spectra show a number of bands in the UV–vis–NIR regions due to presence of Ho3+ and Yb3+ ions. The values of optical band gap (Eg) are found to be 5.69 eV and 5.58 eV for the Ho3+/Yb3+ codoped CaSc2O4 and CaY2O4 phosphors, respectively. The Ho3+/Yb3+ codoped CaSc2O4 phosphors display intense green downshifting emission upon 454 nm excitations. The lifetime of green luminescence of CaSc2O4:Ho3+/Yb3+ phosphors with varied Yb3+ concentrations have also been measured. The decay curves show a non-exponential nature fitted to the Inokuti-Hirayama model and the energy transfer microscopic parameters have been also calculated. The Ho3+/Yb3+ co-doped CaSc2O4 and CaY2O4 phosphors display intense green alongwith weak blue, red, and near-infrared upconversion (UC) emissions upon 980 nm excitations. The spectral color purity (Sgr) of CaSc2O4:Ho3+(1%)/Yb3+(5%) phosphor is calculated to be 0.78. Importantly, the variation of pump power generates intrinsic optical bistability (IOB) in the CaSc2O4:Ho3+(1%)/Yb3+(5%) phosphor for the green emission, which is not observed in the CaY2O4:Ho3+(1%)/Yb3+(5%) phosphor. Therefore, the Ho3+/Yb3+ co-doped CaSc2O4 phosphor could potentially be used in UC-based devices, optical memory devices, optical gates, optical transistors and switching devices for optical communications.

Dual-color light emission and optical waveguide behavior in core-shell heterostructures based on surface doping of cocrystal with rare earth ions

Organic core-shell structures/heterostructures are burgeoning as active photonic materials, i.e., optical waveguides, controllable multi-emissions, input-output optical logic gates. Here, a new conception that rare-earth (RE) ions as the surface dopants for the construction of organic cocrystal@RE complexes core-shell heterostructures was first proposed. Organic cocrystal Tpy-1,4-DITFB (Tpy = 2,2’:6′,2″-terpyridine; 1,4-DITFB = 1,4-diiodotetrafluorobenzenes) as inner-core has been designed. The RE ions of Eu(Ⅲ) and Tb(Ⅲ) are dopped on the surfaces of Tpy-1,4-DITFB cocrystal via epitaxial growth method. The effect of the compositions and morphologies of core-shell heterostructures on the optical behaviors were investagted via fluorescence spectroscopy. Spatially adjacent dual-color emission in the di-block core-shell heterostructures brings about tunable regulation of optical waveguide modes, offering potential applications for input/output optical logic gate and biomedical.

A Novel Decomposed Optical Architecture for Satellite Terrestrial Network Edge Computing

Aiming at providing a high-performance terrestrial network for edge computing in satellite networks, we experimentally demonstrate a high bandwidth and low latency decomposed optical computing architecture based on distributed Nanoseconds Optical Switches (NOS). Experimental validation of the decomposed computing network prototype employs a four-port NOS to interconnect four processor/memory cubes. The SOA-based optical gates provide an ON/OFF ratio greater than 60 dB, enabling none-error transmission at a Bit Error Rate (BER) of 1 × 10−9. An end-to-end access latency of 122.3 ns and zero packet loss are obtained in the experimental assessment. Scalability and physical performance considering signal impairments when increasing the NOS port count are also investigated. An output OSNR of up to 30.5 dB and an none-error transmission with 1.5 dB penalty is obtained when scaling the NOS port count to 64. Moreover, exploiting the experimentally measured parameters, the network performance of NOS-based decomposed computing architecture is numerically assessed under larger network scales. The results indicate that, under a 4096-cube network scale, the NOS-based decomposed computing architecture achieves 148.5 ns end-to-end latency inside the same rack and zero packet loss at a link bandwidth of 40 Gb/s.

Multibit NOT logic gate enabled by a function programmable optical waveguide.

Multibit logic gates are of great importance in optical switching and photonic computing. A 4-bit parallel optical NOT logic gate is demonstrated by an optical switching/computing engine based on a multimode waveguide. The multimode interference (MMI) patterns can be altered by thermal electrodes because the number of guided modes, their profiles, and propagation constants can all be altered via the thermo-optic effect. Instead of conventional forward design based on time-consuming simulations, the proposed engine can update the thermal electrodes automatically and monitor the change of the interference in a synchronized and rapid way until the desired function is reached, all experimentally. We name the system "function programmable waveguide engine" (FPWE). As opposed to solutions where the phase or amplitude of light is taken as the signal, the input stays in the electronic domain, and the output is converted into optical intensity variations, calculated from a truth table. This simple, low-cost yet powerful engine may lead to the development of a new set of devices for on-chip photonic computing and signal switching.

Security enhancement of visible light communication system using proposed 2D-WMZCC codes under the effects of eavesdropper

Abstract Security postulates of visible light communication (VLC) is a paramount area of consideration due to its deployment in military, businesses, and residential establishments. Optical code division multiplexing (OCDMA) is prominent multiples access technique to serve multiple users and offer better security as compared to other available techniques such as wavelength and time division multiplexing (TDM). Wavelength conversion, multicode keying, optical logic gates, and quantum key distribution are some of the widely used security enhancement techniques but come at high cost and greater complexity. Zero cross correlation codes (ZCC) with integration of time dimension is an ultimate solution to the complex security improvement techniques but conventional two dimensional (2D) ZCC codes has an utmost issue of adjacent weights (W) and time (t) in the code which can be easily decoded by eavesdropper. Therefore, in this work, a novel weight managed ZCC (WMZCC) OCDMA code is presented with the non-adjacent W and t in the code matrix for making authentic information decoding difficult. Proposed 2D-WMZCC codes are investigated for 5 users at 100 Gbps over VLC link length of 5 m using polarization division multiplexed (PDM) quadrature phase shift keying (QPSK) and digital signal processing in terms of log symbol error rate (log SER), Q factor and bit error rate (BER). Further, a detailed comparison of 2D-WMZCC codes is performed with existing 2D diagonal identity matrix (DIM) codes and results revealed that former one exhibits better security than later OCDMA code.

Optical Computing: Status and Perspectives.

For many years, optics has been employed in computing, although the major focus has been and remains to be on connecting parts of computers, for communications, or more fundamentally in systems that have some optical function or element (optical pattern recognition, etc.). Optical digital computers are still evolving; however, a variety of components that can eventually lead to true optical computers, such as optical logic gates, optical switches, neural networks, and spatial light modulators have previously been developed and are discussed in this paper. High-performance off-the-shelf computers can accurately simulate and construct more complicated photonic devices and systems. These advancements have developed under unusual circumstances: photonics is an emerging tool for the next generation of computing hardware, while recent advances in digital computers have empowered the design, modeling, and creation of a new class of photonic devices and systems with unparalleled challenges. Thus, the review of the status and perspectives shows that optical technology offers incredible developments in computational efficiency; however, only separately implemented optical operations are known so far, and the launch of the world’s first commercial optical processing system was only recently announced. Most likely, the optical computer has not been put into mass production because there are still no good solutions for optical transistors, optical memory, and much more that acceptance to break the huge inertia of many proven technologies in electronics.

Switchable Nonlinear Optical Absorption of Metal–Organic Frameworks

AbstractMetal–organic frameworks (MOFs) are widely explored owing to their excellent nonlinear optical (NLO) properties. However, researchers have mainly focused on designing new structures of MOF crystals to adjust the NLO response while ignoring the influence of the number of metal–ligand coordination bonds on the NLO properties of MOFs. In this study, the influence of the coordination numbers of MOFs on their NLO properties is studied for the first time. Herein, MOFs with different coordination numbers, using trifluoroacetic acid as an auxiliary agent, are synthesized and their NLO properties are tested using the Z‐scan technique. The results reveal that the NLO absorption properties of MOFs with high coordination numbers can be effectively modulated from saturable absorption to reverse saturable absorption by increasing the excitation intensity. First‐principles calculations show that a change in the coordination numbers leads to a change in the charge transfer from metal to ligand, thereby resulting in different NLO responses. The MOFs with a high coordination number have potential applications in novel optical switches or logic gates. These results provide a reference for the precise adjustment of the NLO properties of MOFs.

Fiber End-Facet Integrated Non-Volatile Optical Switch Based On Ge2Sb2Te5

The silicon photonic integrated network based on the thermo-optical or electro-optical effect generally has the disadvantages of volatile, large footprint, and significant energy loss. Here, we propose and demonstrate an all-optical controllable switch device with non-volatile, broadband adjustable, and bistable fast switching performance by integrating the phase-change material (Ge2Sb2Te5) on the optical fiber. By adjusting the energy of the laser pulse train exerting on the optical fiber, the phase state of the phase-change material can be switched, thereby realizing the ON and OFF function of the optical switch. As a result, a non-volatile optical switch with a wide bandwidth working range (up to 60 nm) and a significant transmission contrast (2 dB) is demonstrated. This device is expected to help realize fast and broadband optical routing in fiber optical communication networks as the optical switch. Furthermore, its logic operation function can impart optical fiber with new storage and computing functionalities except for transmission and sensing. It can be combined with an optical field-programmable gate array (OFPGA) and play a part in optical fiber photonic circuitry in the future.

Application of the ultrashort pulse position modulation method in the frequency domain and dual optical sideband modulation, based on the acoustic-optical filter of photonic crystal fibers to obtain optical logic gates

An acousto-optical filter with tunable polarization based on photonic crystal fibers is used to propose a method of optical modulation, from the modulation by positions of ultrashort pulses in the frequency domain (PPFDM) and the modulation in dual optical sideband simultaneously. So apply this method for generating optical logic gates. It can be shown that AND and OR logic gates can be obtained when a soliton of 55.5-fs time width is encrypted initially generating two bits of information by the modulation method proposed here. We analyzed the optical double-sideband PPFDM modulation for the pulses (bits), polarized in the two input modes, allowing a variation in the εcod encoding parameter for each pulse. One input pulse in relation to another is allowed a phase difference Δϕ = 1.28π, because analyzing the frequency curve as a function of a phase variation, it is observed that it is in this phase that we obtain the most reliable logic gates.

The Design and Simulation of a Novel Optical Adder Depending on Optical Tri-state Gates

Essential approaches involving photons are among the most common uses of parallel optical computation due to their recent invention, ease of production, and low cost. As a result, most researchers have concentrated their efforts on it. The Basic Arithmetic Unit BAU is built using a three-step approach that uses optical gates with three states to configure the circuitry for addition, subtraction, and multiplication. This is a new optical computing method based on the usage of a radix of (2): a binary number with a signed-digit (BSD) system that includes the numbers -1, 0, and 1. Light with horizontal polarization (LHP) (↔), light with no intensity (LNI) (⥀), and light with vertical polarization (LVP) (↨) is represented by -1, 0, and 1, respectively. This research proposes new processor designs for addition. As a result, the design can achieve m addition operations with an operand length of n bits simultaneously. To explain and justify the theoretical design idea, the three steps of adding a BSD are numerically simulated. The constructing process is thought to be more precise and faster because the time to add does not depend on the length of the word. For all entries, all bits are implemented simultaneously, boosting the system's efficiency. A simulation model for six addition processes with a total bit count of 15 bits across all entries is presented in this work performing in a one-time parallelism manner.

Microring resonator based optical logic gates

Microring resonator based optical logic gates

Efficient and Compact Optical NOR Gate based on Photonic Crystal Platform

Efficient and Compact Optical NOR Gate based on Photonic Crystal Platform

Interaction between Graphene Nanoribbon and an Array of QDs: Introducing Nano Grating

In this work, the interaction between an array of QDs and Graphene nanoribbon is modeled using dipole–dipole interaction. Then, based on the presented model, we study the linear optical properties of the considered system and find that by changing the size, number, and type of quantum dots as well as how they are arranged, the optical properties can be controlled and the controllable grating plasmonic waveguides can be implemented. Therefore, we introduce different structures, compare them together and find that each of them can be useful based on their application in optical integrated circuits. The quantum dot arrays are located on a graphene nanoribbon with dimensions of 775 × 40 nm2. Applying electromagnetic waves with a wavelength of 1.55 µm causes polarization in the quantum dots and induces surface polarization on graphene. It is shown that, considering the large radius of the quantum dot, the induced polarization is increased, and ultimately the interaction with other quantum dots and graphene nanoribbon is stronger. Similarly, the distance between quantum dots and the number of QDs on Graphene nanoribbon are basic factors that affect the interaction between QDs and nanoribbon. Due to the polarization effect of these elements between each other, we see the creation of the effective grating refractive index in the plasmonic waveguide. This has many applications in quantum optical integrated circuits, nano-scale atomic lithography for nano-scale production, the adjustment coupling coefficient between waveguides, and the implementation of optical gates, reflectors, detectors, modulators, and others.

High extinction ratio thermo-optic based reconfigurable optical logic gates for programmable PICs

In this paper, a new scheme is proposed to realize reconfigurable and multifunction optical logic gates (XOR, XNOR, NAND, and OR) using a Mach–Zehnder interferometer with a tunable thermo-optic phase shifter (TOPS). The reconfigurable optical logic gates are realized by tuning the phase of an optical signal using TOPS without changing the physical device structure. The logical input “0” or “1” is considered corresponding to the phase of the optical signal at TOPS. The logical output of the proposed device depends on the light intensity at output ports. The device is designed on silicon on insulator (SOI) platform and the simulation result shows that the on–off extinction ratio is greater than 37 dB at 1550 nm and >25 dB for the C-band. Moreover, it has a low insertion loss of 0.09 dB at a wavelength of 1550 nm and <0.8 dB for the C-band window. The proposed optical logic gates can be a promising logical device for programmable photonic integrated circuits.

Contributions of bulk and surface energies in stabilizing metastable polymorphs: A comparative study of group 3 sesquioxides La2O3, Ga2O3 , and In2O3

Sesquioxides are an important class of compounds which are used in various applications such as optical glasses, high-power electronics, and gate dielectrics. Using density functional theory, we investigated bixbyite ${\mathrm{La}}_{2}{\mathrm{O}}_{3}, {\mathrm{In}}_{2}{\mathrm{O}}_{3}$, and ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$; hexagonal ${\mathrm{La}}_{2}{\mathrm{O}}_{3}$; corundum ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$; and monoclinic ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$. We compared the predicted structural properties for each material using the local density approximation (LDA) and the generalized-gradient approximation [GGA PBE (Perdew-Burke-Ernzerhof)]. We found that LDA predicts the correct ground state structure for all three sesquioxides; however, GGA PBE predicts the incorrect ground state structure for ${\mathrm{La}}_{2}{\mathrm{O}}_{3}$. To gain better insight on why this happens, we calculated the phonon properties and the free energy for all structures to determine phase transition temperatures. Additionally, we determined the transition pressure for ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. We also studied several surface terminations for each compound and determined the lowest-energy surface for each structure as well as the interfacial energy for ${\mathrm{La}}_{2}{\mathrm{O}}_{3}$.

Determining code parameters to achieve the maximum bandwidth efficiency in fiber-optic CDMA systems

Abstract This paper first determines the generalized optical orthogonal code (GOOC) parameters to minimize the bit error probability in fiber-optic code division multiple access systems. The systems use on-off keying as the modulator and the optical AND logic gate as the receiver. In situations where the problem of finding the lowest bit error probability has more than one answer, we introduce and examine four approaches to choose the optimal answer. Finally, by employing a complete search of code parameters, we determine GOOC parameters (if there are any) to achieve the maximum bandwidth efficiency considering the design constraints, i.e., the number of network users and the maximum acceptable probability of error.