All-optical XOR Gate Research Articles

Fano Resonance Excited All-Optical XOR, XNOR, and NOT Gates with High Contrast Ratio

We have presented all-optical XOR, XNOR, and NOT gates using metal-insulator-metal (MIM)-coupled ring resonator. The performance of the device is evaluated by finite difference in time-domain (FDTD) method. The proposed gate utilizes a unique phenomenon of Fano resonance to excite logic OFF/ON state. Fano resonance has quite asymmetric resonance profile and the transmission spectrum of Fano profile abruptly drops to a minimum value at the resonance condition. Due to this unique resonance phenomenon, a large value of contrast ratio is obtained. The proposed XNOR gate offers a contrast ratio (C.R.) of 20.66 dB while XOR and NOT gates offer C.R. 12.8 and 18.8 dB respectively. The variation of contrast ratio is also studied against different input wavelength and it is reported that the obtained value of contrast ratio is an optimum value for the proposed structure. The device is compact sized with small dimension 0.31 λ02, where λ0 = 1.55 μm. The proposed device opens up the avenues for designing on-chip optical gates in the field of high-speed optical communication networks.

Realization of XNOR logic function with all-optical high contrast XOR and NOT gates

In this article, we propose the realization of XNOR logic function by using all-optical XOR and NOT logic gates. Initially, both XOR and NOT gates are designed, simulated and optimized for high contrast outputs. T-shaped waveguides are created on the photonic crystal platform to realize these logic gates. An extra input is used to perform the inversion operation in the NOT gate. Inputs in both the gates are applied with out of phase so as to have a destructive interference between them and produce negligible intensity for logic ‘0'. The XOR and NOT gates are simulated using Finite Difference Time Domain method which results with a high contrast ratio of 55.23 dB and 54.83 dB, respectively at a response time of 0.136 ps and 0.1256 ps. Later, both the gates are cascaded by superimposing the output branch of the waveguide of XOR gate with the input branch of the waveguide of NOT gate so that it can be resulted with compact size for XNOR logic function. The resultant structure of XNOR logic came out with the contrast ratio of 12.27 dB at a response time of 0.1588 ps. Finally, it can be concluded that the proposed structures with fair output performance can suitably be applied in the design of photonic integrated circuits for high speed computing and telecommunication systems.

All-optical logic gates in plasmonic metal–insulator–metal nanowaveguide with slot cavity resonator

We demonstrate the compact all-optical logic XOR and OR gates in subwavelength plasmonic metal–insulator–metal waveguides with slot cavity resonators, especially for telecommunication wavelengths, with an extinction ratio of 25 dB, which can provide nanoscale logic integrated circuits. The gates behavior is based on suppression or enhancement of resonant modes in a slot cavity resonator induced by a change in position of input ports. The performance of the gates is discussed analytically and verified by the numerical method of finite-difference time-domain (FDTD).

Ultracompact all-optical logic gates based on nonlinear plasmonic nanocavities

Abstract In this study, nanoscale integrated all-optical XNOR, XOR, and NAND logic gates were realized based on all-optical tunable on-chip plasmon-induced transparency in plasmonic circuits. A large nonlinear enhancement was achieved with an organic composite cover layer based on the resonant excitation-enhancing nonlinearity effect, slow light effect, and field confinement effect provided by the plasmonic nanocavity mode, which ensured a low excitation power of 200 μW that is three orders of magnitude lower than the values in previous reports. A feature size below 600 nm was achieved, which is a one order of magnitude lower compared to previous reports. The contrast ratio between the output logic states “1” and “0” reached 29 dB, which is among the highest values reported to date. Our results not only provide an on-chip platform for the study of nonlinear and quantum optics but also open up the possibility for the realization of nanophotonic processing chips based on nonlinear plasmonics.

Digital Optical Physical-Layer Network Coding for mm-Wave Radio-Over-Fiber Signals in Fiber-Wireless Networks

We demonstrate a digital Optical Physical-layer Network Coding (OPNC) for mm-wave fiber-wireless signals modulated with up to 2.5 Gb/s On/OFF Keyed (OOK) data. The proposed OPNC concept uses an all-optical XOR gate comprising a Semiconductor Optical Amplifier-Mach Zehnder Interferometer (SOA-MZI) with SOAs being driven at low moderate electrical currents in order to perform the all-optical encoding between the OOK envelopes of the data, ignoring the high-frequency Sub-Carrier (SC) signal. In this scheme, network coding is performed on-the-fly at the central office and the resultant packet is broadcasted at the client nodes, where the decoding takes place. We demonstrate experimental results of OPNC using OOK data signals modulated on a 10 GHz SC with the aid of a second all-optical XOR gate for the decoding process at the client's site, reporting error-free performance for both synchronous/asynchronous data packets. The scenario of all optical encoding for 60 GHz SC frequencies followed by electrical decoding at the end-users is evaluated via PHY-layer simulations. Going a step further and considering the network level, we present a performance improvement on the network throughput by using the proposed network coding.

Dispersion on all-optical logic XOR gate using semiconductor optical amplifier

The effect of dispersion on an all-optical logic XOR gate is simulated and investigated. This Boolean function is realized by using semiconductor optical amplifiers-based Mach–Zehnder interferometer (SOAs-MZI). The dependence of the output quality factor (Q-factor) on input pulse energy, pulse width, SOA’s carrier lifetime, linewidth enhancement factor (α-factor) and saturation power has been examined and assessed. The obtained results confirm that the XOR gate implemented with the proposed scheme is capable of operating at a data rate of 80 Gb/s with logical correctness and high output Q-factor.

Simulation of soliton all-optical logic XOR gate with semiconductor optical amplifier

In this new study, a soliton all-optical logic XOR gate is numerically simulated and investigated. This Boolean function is realized by using a semiconductor optical amplifier (SOA)-assisted Mach–Zehnder interferometer. The dependence of the output quality factor (Q-factor) on the soliton characteristics and SOA’s parameters has been examined and assessed. The obtained results confirm that the soliton XOR gate implemented with the proposed scheme is capable of operating at a data rate of 80 Gb/s with logical correctness and high output Q-factor.

Ultrafast surface plasmon-polariton logic gates and half-adder.

In this paper, we present a plasmonic model system for the realization of ultrafast all-optical NOT, AND, OR, and XOR gate operations using linear interference effects in dielectric crossed waveguide structures. The waveguides for the surface plasmon-polaritons are produced by a simple but highly accurate microscopic lithographic process and are optimized for single mode operation at an excitation laser wavelength of 800 nm. The functionality of the presented structures is demonstrated using sub-30 fs laser pulses from a mode locked titanium:sapphire laser. Using leakage radiation microscopy we show ultrafast SPP switching and logic operations of one basic structure consisting of two crossed waveguides with an additional output waveguide along the bisecting line of the input waveguides. The individual gates are realized on a footprint of 10 µm × 20 µm. Experimental investigations are supported by finite-difference time-domain simulations, where good agreement between experimental results and numerical simulations is obtained. To exploit the high precision of the fabrication method and its huge potential for realizing functional complex plasmonic circuitry we experimentally demonstrate a half-adder structure and its operation by combining and cascading several plasmonic waveguide components and logic gate elements on an area of only 10 µm × 28 µm.

Simulation of high quality factor all-optical logic gates based on quantum-dot semiconductor optical amplifier at 1 Tb/s

The ultrafast performances of all-optical logic XOR, AND and OR gates are numerically simulated. These Boolean operations are realized by employing the quantum-dots semiconductor optical amplifiers (QDs-SOAs). The theoretical study is carried out when the effect of amplified spontaneous emission (ASE) is taken into account in the simulation analysis. The dependence of the output quality factor (Q-factor) on signals and QD-SOA's parameters is also investigated and discussed. The obtained results indicate that these all-optical logic gates are capable of operating at 1Tb/s with high output Q-factor provided that these parameters are properly optimized.

Numerical analysis of optical logic gate based on nonlinear optical loop mirror with a photonic crystal fiber

Ultrafast all-optical XOR and XNOR logic gates have been analyzed based on photonic crystal fiber (PCF) nonlinear optical loop mirror (NOLM). The performance of the logic operation is evaluated numerically using the coupled nonlinear Schrödinger equation and split step Fourier method. The wavelength allocation, peak power and the pulse width of signal with respect to the group velocity dispersion (GVD) and the nonlinearity of PCF affect the performance of logic gate. A highly nonlinear PCF with flattened dispersion is proposed to obtain 1 Tb/s operation.

Analysis of all-optical logic XOR gate for 100 Gb/s phase-shift keying modulated data signals in semiconductor optical amplifier-based Mach-Zehnder interferometer

The performance of all-optical logic XOR gate for phase-shift keying modulated data signals has been numerically simulated. This Boolean operation is realized by using a Mach-Zehnder interferometer utilizing semiconductor optical amplifier. The effect of the parameters that are critical for the performance of the scheme on the quality factor is taken into account and investigated. The analysis shows that if these parameters are optimized then the all-optical XOR gate scheme can operate with high performance at data speed of 100 Gb/s for the first time.

Generation of logic gates based on a photonic crystal fiber Michelson interferometer

We present a numerical investigation of all-optical logical gates based in a Michelson interferometer (MI) of micro structured fibers, also known as photonic crystal fibers (PCF). We considered an ultra-short pulse propagating along the system in three distinct regimes of pump power. We determine several relevant quantities to characterize the system performance such as transmission, extinction ratio and crosstalk as a function of the dephasing added to one of the Bragg gratings of the Michelson interferometer (MI). High-order effects, such as third-order dispersion, intrapulse Raman scattering and self-steepening were included in the nonlinear generalized Schrödinger equation governing the pulse propagation. Our results show that the proposed device can be used to obtain all-optical XOR, OR and NOT logic gates.

All-Optical XOR Gate Using Single Quantum-Dot SOA and Optical Filter

In this paper, we propose to implement an all-optical XOR gate for 160 Gb/s return-to-zero data signals using a single quantum-dot semiconductor optical amplifier (QD-SOA) assisted by a detuned optical filter (OF). These two elements are connected in series in a probe-dual pump configuration. By conducting numerical simulations, we thoroughly investigate and assess the impact of the critical performance parameters on the Q <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -factor. The analysis of the obtained results against this metric enables us to specify the data signals peak power, QD-SOA small signal gain, current density, electron relaxation time from the excited state to the ground state and linewidth enhancement factor, and OF detuning, bandwidth and shape, for which the XOR logic is executed at the target data format and rate both with logical correctness and high quality. The confirmation of its design feasibility combined with its simplicity and ultrafast capability makes the XOR gate scheme promising for exploitation in all-optical signal processing and switching applications.

On the design of all-optical gates based on quantum-dot semiconductor optical amplifier with effect of amplified spontaneous emission

The performances of all-optical logic XOR, AND and OR gates have been simulated. These Boolean operations are realized by using a Mach–Zehnder interferometer utilizing semiconductor optical amplifier (SOA) with quantum-dot (QD) active region. The study is carried out when the effect of amplified spontaneous emission is taken into account in the simulation analysis. Results show that these logic gates are capable of operating at a data speed of 250 Gb/s with high output quality factor ( $$Q$$ -factor). The dependence of the output $$Q$$ -factor on signals and QD–SOA parameters is also investigated and discussed.

Performance of all-optical XOR gate based on two-photon absorption in semiconductor optical amplifier-assisted Mach–Zehnder interferometer with effect of amplified spontaneous emission

The performance of all-optical XOR gate is simulated and investigated. This Boolean function is realized by using a Mach–Zehnder interferometer (MZI) and exploiting the nonlinear effect of two-photon absorption (TPA) in semiconductor optical amplifier (SOA) incorporated in the MZI arms. By adjusting the input pulse intensities to be high enough, the TPA-induced phase change can be larger than the regular gain-induced phase change and hence support ultrafast operation in dual rail switching mode. The numerical study is carried out by taking into account the effect of amplified spontaneous emission (ASE). The dependence of the output quality factor ( $$Q$$ -factor) on critical data signals and SOAs parameters is examined and assessed. The obtained results confirm that the XOR gate implemented with the proposed scheme is capable of operating at a data rate of 250 Gb/s with logical correctness and high output $$Q$$ -factor.

Ultrafast All-Optical Signal Processing Using Optically Pumped QDSOA-Based Mach–Zehnder Interferometers

In this paper, we investigate the performance of all-optical logic circuits using quantum-dot semiconductor optical amplifier Mach-Zehnder interferometer (QDSOA-MZI) structures. For the first time, temporal changes in the linewidth enhancement factor (LEF) is analyzed under both optical and electrical pumping schemes using the nonlinear state space model (NSSM) for QDSOAs. We found that significant reduction in the LEF recovery time along with significant increasing in the LEF value of QDSOAs are two important factors that enhance the performance of optically pumped QDSOA-MZI-based all-optical logic gates. Simulation results show that optically pumped QDSOA-MZI structures can be used for implementation of all-optical logic circuits that can operate at bit rates higher than 160 Gb/s, which can never be reached using conventional electrical pumping schemes due to the long-phase recovery time in an electrically pumped QDSOAs. Furthermore, we study the effect of homogeneous broadening on the performance of all-optical logic gates. Moreover, dynamic response of a four-input all-optical XOR gate as a simple all-optical logic circuit is investigated and effect of cascading of optical gates on the performance of all-optical logic circuits is studied.

Silicon photonic crystal all-optical logic gates

All-optical logic gates, including OR, XOR, NOT, XNOR, and NAND gates, are realized theoretically in a two-dimensional silicon photonic crystal using the light beam interference effect. The ingenious photonic crystal waveguide component design, the precisely controlled optical path difference, and the elaborate device configuration ensure the simultaneous realization of five types of logic gate with low-power and a contrast ratio between the logic states of “1” and “0” as high as 20 dB. High power is not necessary for operation of these logic gate devices. This offers a simple and effective approach for the realization of integrated all-optical logic devices. ► Five types of all-optical logic gates are realized theoretically in a two-dimensional silicon photonic crystal structure. ► High contrast ratio between the logic states of “1” and “0” as high as 20 dB is reached. ► There is no high power requirement for the operation of these logic gate devices.

Multilayer photonic logic gate integrated into microelectronic chip

An all-optical XOR gate was designed to take advantage of the previously unused silicon dioxide (SiO 2 ) interconnect layers in a microelectronic chip. The device relies on the coupling of modes between parallel waveguides and the interaction of the modes with the metal interconnects of a silicon chip to obtain a phase difference between input arms. When the signals from the two input arms interfere, the result is a logic XOR operation due to the phase difference. The design was numerically implemented, and a contrast of 18.7 dB was obtained with a 13.2-μm-long logic gate.

All-optical multiple-channel logic XOR gate for NRZ-DPSK signals based on nondegenerate four-wave mixing in a silicon waveguide

We report an all-optical multiple-channel exclusive OR (XOR) gate for 10 Gbits/s non-return-to-zero differential phase-shift keying (NRZ-DPSK) signals using nondegenerate four-wave mixing in a silicon waveguide. The function of the logic XOR gate is experimentally demonstrated using 40 bit DPSK sequences. Also, the eye diagram of the XOR signal is clearly observed as the incident signals are both modulated by DPSK sequences originating from 2(31)-1 pseudorandom binary sequences.

Demonstration of All-Optical Divider Circuit Using SOA-MZI-Type xor Gate and Feedback Loop for Forward Error Detection

We investigated the feasibility of using an optical divider circuit with a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI)-based exclusive or (XOR) gate for an all-optical forward error detection and correction scheme with a cyclic code. We employed a conventional cyclic code scheme: the same divider circuit acts as both encoder and decoder with a given generator polynomial. The divider circuit consists of cascaded XOR circuits and feedback lines. Therefore, the performance of the XOR circuit is one of the key factors for realizing an all-optical scheme. We numerically investigated the operation performance of the SOA-MZI-based all-optical XOR gate. Dynamic operation was simulated using rate equations via the transfer matrix method. The XOR function was also investigated experimentally. The eye diagram obtained from the simulation at a bit rate of 10 Gb/s showed good qualitative agreement with experimental results. Additionally, we confirmed that the optimal condition for a high quality factor (Q-factor) is obtained with equal power for each signal. Next, we demonstrated all-optical divider processing with the SOA-MZI-based XOR circuit and a feedback line that forms the generator polynomial x + 1. The preliminary results for division operation could be verified.