Optical Logic Devices Research Articles

Ultra-fast all-optical encoder using photonic crystal-based ring resonators

Optical encoders are one of the important optical logic devices required in optical communications and optical signal processing. In this paper, we proposed a novel structure for designing an all-optical 4-to-2 optical encoder based on photonic crystals. For this purpose, four photonic crystal-based ring resonators were located between the input and output ports which results in improved coupling efficiencies between input and output waveguide and reduced cross-reflection between the input ports. The central wavelength of the photonic crystal-based ring resonators is 1555 nm. However, due to its wide bandwidth the proposed structure can be used for a wide range of optical waves. In the proposed structure, the delay time and the ON/OFF contrast ratio are 1.8 ps and 9.2 dB, respectively. The other advantages of the proposed structure is that we did not use nonlinear materials in designing the proposed structure, so there is no need for high amount of optical intensities.

Principle and noise performance of optical phase arithmetic devices using four wave mixing

The existing theoretical equations cannot provide an excellent guidance for developing four-wave mixing (FWM)-based optical logic devices, though the experiments have been done in several researches. The optimization of noise figure performances of such devices should be further investigated. In the paper, the universal analytic expressions for the amplitude and phase of the idler in degenerate or non-degenerate FWM process under pump depletion are derived in detail from the nonlinear coupled-mode equations for guiding optical waves propagation in highly nonlinear fiber. The universal analytic expressions are obtained by the first-and the third-kind of elliptic integrals. By using equivalent infinitesimal to calculate the limit of phase sensitive amplification, we find out the initial phase relationship between the idler and the input guided wave for phase-independent amplification, which is crucially important for explaining the operating principles of the FWM-based adder and subtracter. As an example, the configuration of non-degenerate FWM-based hybrid arithmetic device with three logic functions of A+B-C, A+C-B, and B+C-A for QPSK signals is presented, and then the noise transfer characteristics in terms of signal-to-noise ratio (SNR) and error vector magnitude (EVM) are taken into account by adjusting the fiber length, input wavelength, and optical power. The calculation results show as follows. 1) This kind of arithmetic device has a noise figure of about 1.1 dB and an input SNR of more than 24 dB is necessary for the symbol error rate of 10-3 without forward error correction, corresponding to an output EVM of 23.2%. 2) The length of highly nonlinear fiber used in the hybrid arithmetic device may be taken flexibly, provided that the variation of FWM conversion efficiency is controlled in a range of 1 dB relative to the maximum, with an EVM fluctuation of less than for the idlers. 3) The hybrid arithmetic device has an operating optical bandwidth of about 16 nm for the SNR degradation of 1.3 dB. 4) The output EVM increases with the increase of input power, and the allowable input power should be no more than 100 mW for an input SNR of 28 dB, noting that the larger the input SNR, the higher the allowable input power is.

Design of All Optical XOR Gate based on Photonic Crystal Ring Resonator

Abstract The photonic crystals (PhC) play an important role in building all optical logic devices and also recommended as solution for opto-electronic bottleneck in terms of speed and size. This paper put forward a design of XOR gate using Photonic Crystal Ring Resonator (PCRR). The ring resonator is a device which provides output on the basis of coupling of mode fields from a linear waveguide to circular ring. The proposed work is designed using two-dimensional (2D) square lattice photonic crystals within the dimensions of 37 a × 37 a $\left( {37a \times 37a} \right)$ by putting silicon (Si) rods in silica (SiO2). The study of device is carried out using finite-difference-time-domain (FDTD) method and verified using MATLAB.

Ultracompact CMOS-compatible optical logic using carrier depletion in microdisk resonators

We present a CMOS-compatible optoelectronic directed logic architecture that achieves high computational throughput (number of operations per second per unit area) by its ultracompact form factor. High speed-to-power performance is also achieved, by the low capacitance and high junction-to-mode overlap of low-radii SOI vertical pn junction microdisk switches. By using wavelength-division multiplexing and two electrical control signals per disk, each switch performs (N)OR, (N)AND, and X(N)OR operations simultaneously. Connecting multiple switches together, we demonstrate higher-order scalability in five fundamental N-bit logic circuits: AND/OR gates, adders, comparators, encoders, and decoders. To the best of our knowledge, these circuits achieve the lowest footprint of silicon-based multigigabit-per-second optical logic devices in literature.

Design of a Compact Logic Device Based on Plasmon-Induced Transparency

Optical logic device is an important part of optical computing. In this letter, we investigate a novel and compact logic device based on plasmon-induced transparency (PIT). This device consists of a pair of hexagonal ring resonators coupled with two parallel metal-insulator-metal (MIM) waveguides. According to the temporal coupled-mode theory, the appropriate detuning between the resonance wavelengths of two resonators act as the key factor to achieve the PIT. The finite-difference time-domain simulations reveal that by changing the refractive index, logic states 1 and 0 which are represented by the high and low levels of the optical power can be achieved at the through and drop port. So the proposed structure can implement the function of logical operations XOR and XNOR simultaneously. This device is suitable for on-chip optical computing, and it may provide a new way for the realization of plasmonic logic device.

Implementation of all-optical NAND logic gate and half-adder using the micro-ring resonator structures

The computation of digital combinational and sequential logic functionality in the optical domain is one of the most important aspects, which opens the door of fast, secure and efficient switching and communication activity in the modern technological scenario. The proposed paper describes the working optical micro-ring resonator and its application as power optical switching device. Micro-ring resonator constructed by the non-linear material (GaAs–AlGaAs) behaves as powerful optical switching devices. Now, the proper configurations and appropriate arrangement of optical micro-ring resonator gives the concepts related to the realization of the optical NAND and Half adder functionality. Hence paper describes the theoretical aspects for the implementation of all-optical NAND logic gate and one of the most important combinational digital circuits as half adder. The paper includes the relevant MATLAB simulation result, which describes the working of proposed optical logic device.

Nonlinear behavior of the emission in the periodic structure of InAs monolayers embedded in a GaAs matrix

We report time-resolved photoluminescence (TRPL) measurements performed at different temperatures for the Bragg structure containing 60 InAs monolayer-based quantum wells (QWs) periodically arranged in a GaAs matrix. TRPL data reveal an appearance of the additional superradiant (SR) mode originated from coherent collective interaction of QWs. The SR mode is not manifested in the case if a small number of QWs is excited, then only an exciton emission related to the InAs QWs dominates the PL spectrum. The SR mode demonstrates a superlinear dependence of the intensity and radiative decay rate on the excitation power and its intensity increases at elevated temperatures compared to the excitonic emission. The photoluminescence delay time is much shorter for the SR mode indicating that the relaxation of hot excitons can occur via stimulated scattering processes. The specific behavior of the SR emission can have a strong potential for different applications such as optical logic devices, superluminescent diodes, optical switches, and low-threshold lasers. Time-resolved photoluminescence image at low temperature for the Bragg structure consisting of InAs monolayer-based quantum wells (inset).

Actively phase-controlled coupling between plasmonic waveguides via in-between gain-assisted nanoresonator: nanoscale optical logic gates.

The development of nanoscale optical logic gates has attracted immense attention due to increasing demand for ultrahigh-speed and energy-efficient optical computing and data processing, however, suffers from the difficulty in precise control of phase difference of the two optical signals. We propose a novel conception of nanoscale optical logic gates based on actively phase-controlled coupling between two plasmonic waveguides via an in-between gain-assisted nanoresonator. Precise control of phase difference between the two plasmonic signals can be performed by manipulating pumping rate at an appropriate frequency detuning, enabling a high contrast between the output logic states "1" and "0." Without modification of the structural parameters, different logic functions can be provided. This active nanoscale optical logic device is expected to be quite energy-efficient with ideally low energy consumption on the order of 0.1 fJ/bit. Analytical calculations and numerical experiments demonstrate the validity of the proposed concept.

Study of all-optical logic XNOR gate based on XGM in linear optical amplifier

Future digital optical communication cannot develop without all-optical high-speed optical devices, especially in the field of high speed large capacity optical transmission, all-optical packet switching and optical computing, and thus optical logic devices are becoming a hotter spot of research. Based on the cross-gain modulation (XGM), a novel scheme of all-optical logic XNOR gate using linear optical amplifier (LOA) is presented in this paper. LOA results show a good gain characteristic, which can get better output logic operation than traditional semiconductor optical amplifier (SOA). Choosing suitable injection current, wavelength scope of the input signal and CW power can achieve better logic operation effect.

All-optical S-R flip flop using 2-D photonic crystal

The photonic crystals (PhC) draw significant attention to build all optical logic devices and considered one of the solutions for the opto-electronic bottleneck via speed and size. The paper presents a novel all optical SR flip flop memory based on two optical NOR gates using 2D PhC. The design of optical Flip Flop is based on four nonlinear photonic crystal ring resonator and T-type waveguide. The total size of the proposed optical memory flip flop is equal to 30 μm × 30 μm. The structure has lattice constant ‘a’ is equal to 630 nm and bandgap range from 0.32 to 044. The flip flop design has a switching time in few Picoseconds and low power input of 50 mW. The PhC structure has a square lattice of silicon rod with refractive index of 3.39 in air. The overall design and the results are discussed through the experimental implementation and the numerically simulation to confirm its operation and feasibility.

A dual-stimuli-responsive fluorescent switch ultrathin film.

Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP@PTBEM and Rf-PSS with cationic layered double hydroxide (LDH) nanoplatelets to obtain the (Rf-PSS/LDH/SP@PTBEM)n UTFs (n: bilayer number). The assembly process of the UTFs and their luminescence properties, as monitored by fluorescence spectroscopy and scanning electron microscopy (SEM), present a uniform and ordered layered structure with stepwise growth. The resulting Rf-PSS/LDH/SP@PTBEM UTF serves as a three-state switchable multicolor (green, yellow, and red) luminescent system based on stimulation from UV/Vis light and pH, with an acceptable reversibility. Therefore, this work provides a facile way to fabricate stimuli-responsive solid-state film switches with tunable-color luminescence, which have potential applications in the areas of displays, sensors, and rewritable optical memory and fluorescent logic devices.

Ultrafast, superhigh gain visible-blind UV detector and optical logic gates based on nonpolar a-axial GaN nanowire.

Nonpolar a-axial GaN nanowire (NW) was first used to construct the MSM (metal-semiconductor-metal) symmetrical Schottky contact device for application as visible-blind ultraviolet (UV) detector. Without any surface or composition modifications, the fabricated device demonstrated a superior performance through a combination of its high sensitivity (up to 10(4) A W(-1)) and EQE value (up to 10(5)), as well as ultrafast (<26 ms) response speed, which indicates that a balance between the photocurrent gain and the response speed has been achieved. Based on its excellent photoresponse performance, an optical logic AND gate and OR gate have been demonstrated for performing photo-electronic coupled logic devices by further integrating the fabricated GaN NW detectors, which logically convert optical signals to electrical signals in real time. These results indicate the possibility of using a nonpolar a-axial GaN NW not only as a high performance UV detector, but also as a stable optical logic device, both in light-wave communications and for future memory storage.

Table-top mirror based parallel programmable optical logic device

Abstract Light rays can easily be reflected to different path by mechanical movement of mirrors. Using this basic operational principle we can design parallel programmable optical logic device (PPOLD) by arranging mirrors on a table. The ‘table-top mirror’ models of this proposed circuit have been shown here. We can program it to design all the two input 16-Boolean logical expressions from a single design. The design is based on only plane mirrors. No active optical material is used in this design. Not only that the proposed circuit is optically reversible in nature. Moreover this design is very simple in sense. It can be fabricated in MEMS based optical switches.

Synthesis and Characterization of Plasmonic Resonant Guided Wave Networks

Composed of optical waveguides and power-splitting waveguide junctions in a network layout, resonant guided wave networks (RGWNs) split an incident wave into partial waves that resonantly interact within the network. Resonant guided wave networks have been proposed as nanoscale distributed optical networks (Feigenbaum and Atwater, Phys. Rev. Lett. 2010, 104, 147402) that can function as resonators and color routers (Feigenbaum et al. Opt. Express 2010, 18, 25584-25595). Here we experimentally characterize a plasmonic resonant guided wave network by demonstrating that a 90° waveguide junction of two v-groove channel plasmon polariton (CPP) waveguides operates as a compact power-splitting element. Combining these plasmonic power splitters with CPP waveguides in a network layout, we characterize a prototype plasmonic nanocircuit composed of four v-groove waveguides in an evenly spaced 2 × 2 configuration, which functions as a simple, compact optical logic device at telecommunication wavelengths, routing different wavelengths to separate transmission ports due to the resulting network resonances. The resonant guided wave network exhibits the full permutation of Boolean on/off values at two output ports and can be extended to an eight-port configuration, unlike other photonic crystal and plasmonic add/drop filters, in which only two on/off states are accessible.

All-optical approach for conversion of a binary number having a fractional part to its decimal equivalent to three places of decimal using single system optical tree architecture

Several optical methods have been proposed for implementation of all optical logic and arithmetic devices during the last few decades. In this regard, the role of optical tree architecture can be mentioned as an important approach for conversion of an optical data from binary to decimal and vice-versa. In this communication, the authors propose a new concept of conversion of a binary number having fraction (fractional value) to its equivalent decimal counterpart to any desired number of places after decimal using a single optical circuit with outputs rearranged. In this operation, optical tree and some nonlinear material based switches are used properly owing to their high speed.

Polystyrene Kerr nonlinear photonic crystals for building ultrafast optical switching and logic devices

In recent years all-optical switching and logic devices have received extensive attention due to their potential applications in next generation ultrahigh-speed information processing and optical computing. Kerr nonlinear photonic crystals (NPC) offer a promising route to realize all-optical switching with ultrafast response time and low pump power based on simple and robust physical mechanisms. In this feature article, we present our extensive investigation on Kerr NPCs made from polystyrene, an organic polymer material with large Kerr nonlinearity and extremely fast response time down to several femtoseconds, and their application to build ultrafast, low power, and high contrast optical switching and logic devices. Several relevant issues are discussed and analyzed, including the principal working mechanism of all-optical switching and logic devices in Kerr NPCs, preparation of polystyrene NPCs by means of microfabrication and self-assembly techniques, characterization of optical switching performance by means of femtosecond pump-probe technique, and synthesis of silicon–polystyrene hybrid NPCs by means of nano-imprint technology as a promising route to construct switching, modulating, and logic devices compatible with popular silicon photonics.

New simulative studies on performance of semiconductor optical amplifier based optical switches like frequency converter and add-drop multiplexer for optical data processors

Optics has proved its successful role in parallel logic, arithmetic or algebraic operations. So many different methods on optical data processing were proposed and implemented in last few decades. For implementing the all optical logic and arithmetic devices it needs different types of encoding principle like, polarization encoding principle, frequency encoding principle, intensity encoding principle and phase encoding principle. As the frequency is the basic characteristics of light, so frequency encoding principle is the most reliable one among all other encoding principles. Currently frequency encoding technique is established as a promising one for all optical processing, as frequency of light does not change normally after reflection, refraction, absorption etc. Again Semiconductor optical amplifier (SOA) can be used for different successful frequency conversions. Here in this technique ‘1’ logic state is represented by a frequency ν2 then ‘0’ state is represented by another frequency ν1 instead of intensity variation. In this paper the authors describe the simulation study of the performances of SOA in various optical switches like frequency conversion and add-drop multiplexer.

Electric Spaser in the Extreme Quantum Limit

We consider theoretically the spaser that is excited electrically via a nanowire with ballistic quantum conductance. We show that, in the extreme quantum regime, i.e., for a single conductance-quantum nanowire, the spaser with a core made of common plasmonic metals, such as silver and gold, is fundamentally possible. For ballistic nanowires with multiple-quanta or nonquantized conductance, the performance of the spaser is enhanced in comparison with the extreme quantum limit. The electrically pumped spaser is promising as an optical source, nanoamplifier, and digital logic device for optoelectronic information processing with a speed of ~100 GHz to ~100 THz.

Towards integrated nanoplasmonic logic circuitry

Surface plasmon polaritons (SPPs) may serve as ultimate data processing expedients in future nanophotonic applications. SPPs combine the high localization of electrons with the bandwidth, frequency and propagation properties of photons, thus supplying nature with the best of two worlds. However, although plasmonics have recently gained constantly growing scientific attention, logic devices that operate on SPPs on a deep nanometer scale are yet to be demonstrated. Here, we design, fabricate and experimentally verify the smallest, first ever reported all optical nanoplasmonic XOR logic gate. The introduced XOR device is based on a novel engineerable interferometry scheme with extremely compact dimensions of λ(3)/15,500, which can be used to realize a variety of plasmonic logic functionalities. We use frequency modulated Kelvin probe microscopy to provide evidence of binary XOR functionality performed directly on SPPs with λ(3)/80,000 mode volumes. An extinction ratio of 10 dB is achieved for a device length of 150 nm, increasing up to 30 dB for a device length of 280 nm. Our findings confirm plasmonics as the favorite data carriers in integrated all optical logic devices operating on the deep nanoscale, and pave the way to the development of future ultrafast information processing technologies based on SPPs.

Tunable thermo-optic switch based on fluid-filled photonic crystal fibers

A tunable thermo-optic intensity-modulated switch is investigated theoretically and numerically. It is based on the infiltration of temperature-sensitive mixture liquids into index-guiding photonic crystal fibers (PCFs). The switching function attributes to the thermo-optic effect of the effective refractive index of the cladding. The simulation illustrates that the switch presents a tunable transition point according to the concentration of the mixture liquids, and the on-off switching functionality can be realized within a narrow temperature range of 2 °C. The switches have wide application for innovative all-in-fiber optical communication and logic devices.