All-optical Logic Gates Research Articles

High-speed all-optical logic gate using QD-SOA and its application

The scheme to realize high-speed (~250 Gb/s) all-optical Boolean logic gates using semiconductor optical amplifiers with quantum-dot (QD-SOA) is introduced and analyzed in this review. Numerical si...

Realization of Ultra-Accurate and Compact All-Optical Photonic Crystal OR Logic Gate

By unique combination of single-line defects, Mach-Zehnder interferometer, and ring resonators, we propose a novel, easy-to-fabrication and linear scheme for realizing accurate and compact all-optical OR logic gate based on 2-D photonic crystal structures. To obtain the transmission spectra of the structure, we considered the entire structure as a single cavity and then we applied a fast Fourier transform to the transmitted spectral power densities at the output port and the unexcited input port; this strategy enhances the control on unwanted port-to-port power reflections and hence increasing the distinction between logic levels. Simulating the electromagnetic wave propagation in the proposed device reveals that the accurate all-optical OR logic gate is obtained. The achieved contrast ratio between logic levels is $\sim 7.27$ dB. Moreover, since all ports are located on the same side and the size of the structure is $12.5~\mu \text{m} \times 16~\mu \text{m}$ . It is fully compacted and has the ability of dense integration. The proposed structure is completely easy-to-fabrication and designed for using in future high accuracy photonic integrated circuits.

Reconfigurable All-Optical Logic Gates Using Single Semiconductor Optical Amplifier at 100-Gb/s

All-optical NOR, OR, and AND logic gates are experimentally demonstrated at a bit rate of 100 Gb/s with single semiconductor optical amplifier (SOA) associated with careful optical filtering. Correct logic results and clear eye openings are achieved by all the logic gates. These three different logic gates are easily reconfigurable by deploying continuous wave light at the input of the SOA and changing the parameters of the filter at the output of the SOA. We also propose an enhanced method of construction for higher quality OR logic gates by deploying and combining blue- and red-shift filtering simultaneously with phase modulation.

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.

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.

Performance analysis of an all-optical logic gate based on a single I/Q modulator with direct detection.

This paper investigates the performance of an all-optical logic gate scheme based on a single in-phase and quadrature (I/Q) modulator with direct detection. The proposed scheme of an all-optical logic gate is simple, high speed, and easily reconfigured to realize 24 logic states by adjusting bias voltages, peak-to-peak voltages of the driven RF signals, and the phase shift. As the scheme to realize logic gates is based on the irregular use of a commercially available I/Q modulator and laser source, a specialized logic gate system including a laser, I/Q modulator, and driven RF module should be optimally designed to obtain the best performance. With the system's extinction ratio (ER) and Q-factor as metrics, the performance of the proposed logic gate scheme is analyzed theoretically and numerically in this paper. We first give a new theoretical model of the I/Q modulator. Next, taking the OR gate as an example, the simulations are carried out to analyze performance under the influence of some key factors in the system. Results show that the extinction ratio of the whole system is affected by the phase shift between the two arms of the I/Q modulator and the extinction ratios of two Mach-Zehnder modulators (MZMs), while Q-factor is further influenced by the output power of the laser and the insertion loss of the MZMs in the I/Q modulator. For an I/Q modulator with MZMs having an extinction ratio of 20 dB, the minimum laser output power to obtain a system's ER higher than 16 dB is 3 dBm, while in order to obtain a Q-factor higher than 6, the output power of the laser must not be <10 dBm.

Interaction potential between discrete solitons in waveguide arrays.

Using a variational approach, we obtained the interaction potential between two discrete solitons in optical waveguide arrays. The resulting potential bears the two features of soliton-soliton and soliton-waveguide interaction potentials where the former is similar to that of the continuum case and the latter is similar to the effective Pierls-Nabarro potential. The interplay between the two interaction potentials is investigated by studying its effect on the soliton molecule formation. It is found that the two solitons bind if their initial separation equals an odd number of waveguides, while they do not bind if their separation is an even number, which is a consequence of the two solitons being both either at the intersites (unstable) or being onsite (stable). We derived the equations of motion for the solitons' centre of mass and relative separation and provided analytic solutions for some specific cases. Favourable agreement between the analytical and numerical interaction potentials is obtained. Possible applications of our results to all-optical logic gates are pointed out.

Design and simulation of photonic crystal based all-optical logic gate and modulator using infiltration

We propose all-optical logic gate and modulator using nonlinear Kerr effect. The hybrid structure based on 2-D photonic crystal slab with triangular air-hole lattice is used for this purpose. The proposed cavity of switch structure is designed by infiltration of air holes with low refractive index and high third-order nonlinear coefficient polystyrene. Using numerical simulation, we present a fast logic gate with maximum on/off ratio of 26.61 dB, and minimum switching time window of 5.66 ps, while the maximum threshold power is 181 mW. We, also, propose a modulator which can operate with the bit rate as high as above 70 Gbps.

High-speed all-optical NAND/AND logic gates using four-wave mixing Bragg scattering.

A high-speed all-optical NAND logic gate is proposed and experimentally demonstrated using four-wave mixing Bragg scattering in highly nonlinear fiber. NAND/AND logic functions are implemented at two wavelengths by encoding logic inputs on two pumps via on-off keying. A 15.2-dB depletion of the signal is obtained for NAND operation, and time domain measurements show 10-Gb/s NAND/AND logic operations with open eye diagrams. The approach can be readily extended to higher data rates and transferred to on-chip waveguide platforms.

Implementation of a Reconfigurable Optical Logic Gate Using a Single I/Q Modulator With Direct Detection

We propose and investigate a new scheme to realize all-optical logic gates using a single I/Q modulator with direct detection. Both intensity and phase of the optical signal are utilized to represent the four different states of two binary inputs, whereas direct detection is used to map the four states to the corresponding binary output. This structure is very simple and has the potential to reach high speed. All of the basic logic gates can be implemented by adjusting the bias voltages of the two arms, peak–peak voltages of the driving signals, and the phase shift. Experiments are successfully carried out to realize all six basic logic gates at the data rate up to 10 Gb/s with eye diagrams clearly observed. Extinction ratios (ERs) of the output signals are increased for all these logic gates, compared with the original input signals. ER decreases when increasing the data rate from 1 to 10 Gb/s. Up to 24 logic gates can be implemented by using a single I/Q modulator.

Efficient Reversible Multiplexer Design Using proposed AllOptical New Gate

The interest for transmission capacity in overall information systems keeps on expanding because of developing utilization of Internet and high-transfer speed applications, for example, video. All-optical signal processing is one promising system for giving the essential limit and offers payload transparency, power utilization which scales proficiently with expanding bit rates, lessened handling inertness, and ultrafast signal processing. These networks do not have any optical to electrical converters because signal is photonic throughout its path and thus energy is conserved which is otherwise wasted in conversion of photons to electrons and back. Thus to achieve this, various configurations of Mach-Zehnder Interferometers are used which make signal processing quite fast and also power consumption is reduced. For all-optical switching to become a reality, integration is necessary to significantly reduce the cost of manufacturing, installation, and operation. One promising integrated all-optical logic gate is the semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) which has advantages like faster switching time, ease of fabrication, lesser power and high speed. As transistor count is increasing day by day, power consumption is increased so it has put a limit on transistor count. Therefore reversible logic has come into picture which has remarkable property of dissipating lesser power. So digital circuits are designed with only consists of reversible logic gates and thus researchers are aiming at designing new gates to reduce the optical cost and delay of the circuits. In this paper a new gate has been proposed and multiplexer design is shown with improved optical cost and delay and also

Design of all-optical simultaneous AND, NAND, OR, and NOR logic gates using phase-based control of three coupled waveguides

In this paper, we present a novel phase-based structure for implementing the all-optical multi-function logic gates. The proposed structure which is composed of three coupled waveguides allows us to simultaneously access OR/NOR and AND/NAND logic functions from different output ports. The phase of middle waveguide plays the role of control tool which defines the logical values of outputs. The output ports can be switched from OR/NOR to AND/NAND logic functions by changing the control phase from 24 $$^{\circ }$$ to 237 $$^{\circ }$$ , respectively. Beam propagation method has been employed in order to accomplish the simulations of light propagation.

All-optical logical gates based on photoinduced molecules reorientation in amorphous polymer films

A type of all-optical logical gate based on two kinds of refractive index grating in azo-dye doped polymer film is studied in this paper. Using interference recording method with two 532[Formula: see text]nm laser beams, the transient refractive gratings can be formed in poly(methyl methacrylate) (PMMA) films containing azo-dye Disperse Red 13 (DR13). The characteristics of the transient gratings in films which are recorded by two 532[Formula: see text]nm laser beams with different polarization states are investigated by monitoring the first-order diffraction intensity of the readout He–Ne laser beam (632.8[Formula: see text]nm). It is found that the transient gratings in the polymeric films can be established and decayed in several seconds. Furthermore, we realize XOR and XNOR all-optical logical operation based on the relationship among the polarization states of the recording beams, the reading beam, and the diffraction beam.

Optical logic gates based on semiconductor optical amplifier Mach–Zehnder interferometer: design and simulation

All-optical logic gates are designed to extend the existing design to a higher number of bits, to use the same gate in multifunctions, and to add new gate designs. This type of gate is based on semiconductor optical amplifier (SOA) nonlinearities, since the SOA can provide a strong change of the refractive index together with high gain. The SOA is used with a Mach–Zehnder interferometer (MZI) forming an SOA-MZI structure which is used to perform the logic gates XOR, NOR, OR, and XNOR. Two binary input data signals are used with different number of bits (4, 6, 8, and 16 bit) at 10 Gbps. This work includes the study of the effect of the number of bits on the received power, minimum bit error rate, and maximum Q-factor.

Low-photon-number optical switch and AND/OR logic gates based on quantum dot-bimodal cavity coupling system.

We propose a new scheme based on quantum dot-bimodal cavity coupling system to realize all-optical switch and logic gates in low-photon-number regime. Suppression of mode transmission due to the destructive interference effect is theoretically demonstrated by driving the cavity with two orthogonally polarized pulsed lasers at certain pulse delay. The transmitted mode can be selected by designing laser pulse sequence. The optical switch with high on-off ratio emerges when considering one driving laser as the control. Moreover, the AND/OR logic gates based on photon polarization are achieved by cascading the coupling system. Both proposed optical switch and logic gates work well in ultra-low energy magnitude. Our work may enable various applications of all-optical computing and quantum information processing.

Improved design of all-optical photonic crystal logic gates using T-shaped waveguide

In this paper, we propose new structures of all-optical logic gates based on two-dimensional photonic crystal of square type lattice with Si rods in air background. The proposed structures are based on T-shaped waveguide with optimized edge rod radius. An extra reference input port is included in the structure along with the actual input ports required for a logic gate. The simulation results show that the proposed T-shape waveguide can work as a NOT gate and a dual T-shape waveguide can work as NOR, XNOR and NAND gate with proper change in the phase values of logic ‘1’ input. The proposed structures have fast response time with value not more than 0.35 ps. The size of these structures is also small. It is expected that these new T-shaped structure based all-optical logic gates are suitable for large scale optical integration and can potentially be used in on-chip photonic integrated circuits.

Tunable all-optical gates in 2D discrete cavity solitons with local defect

We numerically studied the existence of discrete cavity solitons in a two-dimensional array of coupled optical cavities with Kerr nonlinearity influenced by a local Gaussian defect. Effect of the defect on soliton on/off switching by injecting a writing/erasing external beam is also discussed. The interaction of two adjacent solitons, mediated by a defect is considered and effect of the positive and negative defect on the independency interval is determined. Finally all-optical NOR and NAND logic gates are proposed which are tunable by well-adjusting the defect height.

All-optical XOR and OR logic gates based on line and point defects in 2-D photonic crystal

In this paper, we have proposed an all-optical logic gate structure based on line and point defects created in the two dimensional square lattice of silicon rods in air photonic crystals (PhCs). Line defects are embedded in the ГX and ГZ directions of the momentum space. The device has two input and two output ports. It has been shown analytically whether the initial phase difference between the two input beams is π/2, they interfere together constructively or destructively to realize the logical functions. The simulation results show that the device can acts as a XOR and an OR logic gate. It is applicable in the frequency range of 0–0.45 (a/λ), however we set it at (a/λ=) 0.419 for low dispersion condition, correspondingly the lambda is equal to 1.55µm. The maximum delay time to response to the input signals is about 0.4ps, hence the speed of the device is about 2.5THz. Also 6.767dB is the maximum contrast ratio of the device.

Realization of an ultrafast all-optical Toffoli logic gate based on the phase relation between two second order nonlinear optical signals

A Toffoli logic gate (CCNOT gate) is a universal reversible logic gate from which all other reversible gates can be constructed. It has a three-bit input and output. The goal of our work was to realize a Toffoli gate where all inputs and outputs are realized optically, which allows for ultrafast switching processes. We demonstrate experimentally that a Toffoli logic gate can be created based on nonlinear multi-wave interactions of light with matter. Using femtosecond laser pulses, the all-optical Toffoli gate is based on the coherence of the optical signals produced via the nonlinear optical processes. Sum frequency (SF) and second harmonic (SH) generations are combined in such a way so as to yield the complete truth table of the universal reversible logic gate.

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.