All-optical Logic Gates Research Articles

Transition from saturable absorption to reverse saturable absorption in MoTe2 nano-films with thickness and pump intensity

Nonlinear optical effect such as saturable absorption (SA) and reverse saturable absorption (RSA) play a key role for all-optical logic gates, in which transition between them is a challenging issue for the optoelectronic applications. Herein, we find MoTe2 nano-films fabricated with liquid-phase exfoliation and a vacuum filtration method which demonstrate both SA and RSA with different thicknesses and pump intensity. The SA nonlinear optical susceptibility for thick film (100 nm) is Imχ(3) ∼ 10−11 esu. However, the thin film (30 nm) exhibited RSA with the Imχ(3) as high as ∼9.96 × 10−11 esu. The different nonlinear optical response with the thickness is due to the interlayer coupling effect. Under high pump intensity, the thick MoTe2 film also demonstrates transition from SA to RSA. The four energy-level model is employed to analyze the competition between the ground-state and excited-state absorption. We found that the conversion of SA to RSA depends not only on pump intensity but also on the absorption cross-section and transition probability between energy level. The transition properties of SA and RSA for MoTe2 films can be used in all-optical logic gates, fast optical switch, optical limiter, mode storage and so on.

All-optical logic gates based on XPM effect under the PAM-ASK modulation in a symmetric dual NLDC

We investigate the possibility of achieving all-optical logical gates based in a symmetric double non-linear directional coupler (NLDC) working with pulses of 2 ps coded for the pulse amplitude modulation-amplitude shift keying (PAM-ASK), in a digital keying. The effects of group velocity dispersion, nonlinear self phase modulation and cross phase modulation (XPM) are taken into account in a lossless theoretical setup scheme. We analyze the amplitude and shape of the output pulses as a function of the modulation factor \((|\varepsilon |)\) to show that an OR gate can be readily realizable. Further, we also implement an optical sign phase shift in one of the NLDC input channels after the PAM-ASK modulator. We identify parameter regions on which the logical operations NAND, OR and XOR can be performed with the respective re-configurable scheme set by PAM-ASK modulation technique under the XPM effect.

Ultra-compact all-optical phase-controlled NAND, OR, XOR, XNOR, and NOT multi-function logic gate

We propose a novel multi-function logic gate in order to attain all NAND, OR, XOR, XNOR, and NOT logic functions in a single structure with controlling the phase of input lights. Beam propagation analysis illustrates that the highest insertion loss of structure is − 0.05 dB in whole C-band. The output on–off logic level contrast ratio for NAND, OR, XOR, XNOR, and NOT logic functions are 28.2, 28.2, 30.2, 30.2, and 30.2 dB, respectively. The structure which is composed of one multimode interference region with ultra-small size of 1.5 µm × 12.2 µm is a promising candidate for ultra-compact systems.

A novel proposal for an all-optical Galois field adder using nonlinear PhCRRs

Adding nonlinear rods to photonic crystal ring resonators is a common way used for designing all-optical logic gates. In this paper, we will use the same method for designing an all-optical Galois field adder. The proposed structure can be realized by parallel combination of four optical XOR gates; therefore, for realizing the proposed structure, we designed the basic XOR gate then created the final structure by combining four XOR gates.

In brief

PAGE 582 Researchers in Germany present a red emitting laser with V-shaped surface grooves in the p-confinement layer, which result in low radiation losses. The laser will be suitable for many applications that require laser sources that emit high-power at precisely defined wavelengths, such as interferometry, free-space communication, metrology and light detection. PAGE 558 A collision avoidance scheme for ground vehicles is proposed in work from Korea. The scheme including a modified turn algorithm improves driving performance by minimising sudden curvature changes and side-slips of the vehicle. A non-linear estimator for time-to-collision is also introduced to increase collision avoidance. Surface grooves in a red emitting laser result in low radiation losses to produce high output power. PAGE 584 Work from the US demonstrates that a 3D metamaterial structure with back-to-back, vertically oriented metallic cross dipoles efficiently linearly polarises light. The control over light polarisation in the presented metamaterial surpasses that of traditional 2D polarisers due to a reduction in reflected and transmitted polarisation. A scheme to improve driving performance reduces sudden changes in curvature of ground vehicles. PAGE 580 Researchers in Japan design an all-optical AND logic gate using photonic crystal (PC) quantum dot semiconductor optical amplifiers (QDSOA) for optical equipment, like multiplexers. The proposed gate is compared to traditional QDSOA optical gates and the incorporation of a PC is shown to reduce energy consumption and device volume. Efficient linear polarisation of light with a 3D metamaterial structure. PAGE 595 A method to resolve terrain features to adjust the trajectory of a mobile robot using vibrations from vehicle-terrain interactions is reported in work from Korea. The presented algorithm allows a robot that explores an unfamiliar area to efficiently plan their path across different surfaces with differing features and textures. An all-optical quantum dot semiconductor photonic crystal AND logic gate is presented with low energy consumption. Vehicle-terrain interactions are used to adjust a planned route for efficient terrain exploration.

All-optical logic gates based on coupled heterostructure waveguides in two dimensional photonic crystals

In this study, all-optical logic gate with multifunctional performance have been designed in two-dimensional coupled photonic crystal waveguides (CPCWs) employing modulation of the refractive index in the coupling region. A two dimensional finite-difference time domain (2D-FDTD) was employed in our numerical simulations. It is shown that by switching the optical signal to different input waveguide ports, the proposed device can function as AND, OR, NOR and NOT gates operating at many or single wavelength. Our simulation results show that the optimized devices have very good transmission efficiencies, a broad frequency range and the contrast ratios between the output ports reveal a satisfactory level. Our results not only provide a simple on chip platform for next generation logic optical circuits, but also open up the possibility for the realization of ultrahigh speed signal processing, and future photonic crystal based all-optical integrated circuits.

All-Optical Multiple Logic Gates Based on Spatial Optical Soliton Interactions

In this letter, all-optical logic gates with attraction and repulsive interactions of coherent spatial optical solitons have been designed in a bulky nonlinear Kerr medium. The logic gates comprise logical AND and OR gates by the attraction of two obliquely propagating inphase spatial optical solitons and logical NOR and XNOR gates based on repulsive interaction among three out of phase spatial optical solitons. The numerical results show that soliton interactions perform a high contrast power level between ON/OFF states. The proposed model is applicable to design phase-modulated logical gates too. The simplicity and ease for fabrication of the proposed logic gates would be a potential key component for the future of all-optical logical photonic devices and computational photonic circuits.

Design and performance analysis of all-optical cascaded adder using SOA-based MZI

With the performance enhancements in all-optical signal processing and switching schemes in terms of data rate and processing speed, various devices enabled with all-optical operation are becoming primary requirements for current and future telecommunications and data networks. All-optical logic gates represent the best solution to realize both combinational as well as sequential devices in the optical domain, representing the basic building blocks for optical computing circuits. We propose herein an all-optical cascaded adder whose elementary blocks are a half-adder and full-adder, designed using semiconductor optical amplifier (SOA)-based Mach–Zehnder interferometer (MZI) gate configurations. They have high thermal stability and require low power. The nonlinear effects in the SOA device are used to implement different logic operations. The proposed cascaded adder was simulated in OptiSystem. The optical signal-to-noise ratio, bit error rate (BER), and Q-factor values were evaluated for different data rates. The design showed good performance up to 60 Gbps. The proposed design could find application in implementation of multistage arithmetic logic units.

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.

Multifunctional logic gates based on silicon hybrid plasmonic waveguides

Nano-scale Multifunctional Logic Gates based on Si hybrid plasmonic waveguides (HPWGs) are designed by utilizing the multimode interference (MMI) effect. The proposed device is composed of three input waveguides, three output waveguides and an MMI waveguide. The functional size of the device is only 1000 nm × 3200 nm, which is much smaller than traditional Si-based all-optical logic gates. By setting different input signals and selecting suitable threshold value, OR, AND, XOR and NOT gates are achieved simultaneously or individually in a single device. This may provide a way for ultrahigh speed signal processing and future nanophotonic integrated circuits.

All-optical clocked flip-flops and random access memory cells using the nonlinear polarization rotation effect of low-polarization-dependent semiconductor optical amplifiers

Basic configurations of various all-optical clocked flip-flops (FFs) and optical random access memory (RAM) based on the nonlinear polarization rotation (NPR) effect of low-polarization-dependent semiconductor optical amplifiers (SOA) are proposed. As the constituent elements, all-optical logic gates and all-optical SR latches are constructed by taking advantage of the SOA’s NPR switch. Different all-optical FFs (AOFFs), including SR-, D-, T-, and JK-types as well as an optical RAM cell were obtained by the combination of the proposed all-optical SR latches and logic gates. The effectiveness of the proposed schemes were verified by simulation results and demonstrated by a D-FF and 1-bit RAM cell experimental system. The proposed all-optical clocked FFs and RAM cell are significant to all-optical signal processing.

Realization of all-optical NAND and NOR logic functions with photonic crystal based NOT, OR and AND gates using De Morgan’s theorem

In this article, we propose the realization of photonic crystal based all-optical universal logic gates, NAND and NOR with basic logic gates viz. NOT, AND and OR in two level logic using De Morgan’s theorem. As per the theorem, NAND or NOR gate can be designed with two NOT gates in first level, cascaded to a second level OR gate or AND gate, respectively. Initially, the basic logic gates are designed and optimized such that their implementation in the design of NAND and NOR gates cannot degrade the threshold value of logic levels. Length of the input waveguides in each design is kept common so as to have a change in the interference of the input signals with a phase difference of 0° and 180°. The proposed basic logic gates are resulted with a contrast ratio of 11.04, 8.24, and 5.18 dB, respectively. While the calculated values of contrast ratio of NAND and NOR gates are 5.81 and 4.02 dB, respectively. Moreover, the bit rate of the proposed designs is above 7.485 Tbps which shows their inevitable usage in high speed data communication networking.

All-optical photonic crystal logic gates using nonlinear directional coupler

In this paper, a nonlinear photonic crystal structure consisting of a nonlinear directional coupler and junctions for the design of all-optical logic gates is proposed. A bi-functional photonic crystal structure is initially designed which provides different two XOR or OR logic operations. Thereafter, by applying some modifications in the basic structure, new topologies for all-optical XNOR, NOR and AND logic gates are proposed. Nonlinear rods of the proposed structure are made of silicon nanocrystal to create required phase shift. The finite difference time domain and plane wave expansion methods are used to evaluate the proposed structures. Our simulation results show that the proposed gates can operate with a bit rate of more than 1 Tbits/s and also, inputs and output of the proposed logic gates are homogeneous with the required power of 3W for switching operation.

Two and three-input all-optical logic gates on a planar three-core photonic crystal fiber

In this paper, we numerically demonstrate the acquisition of two all-optical devices that perform the OR and AND logic operations using a solid core Photonic Crystal Fiber (PCF) with three symmetrical cores in planar array using solitonic pulses modulated in PAM-ASK. We numerically simulated the propagation of 100 femto-second (fs) solitonic pulses through the PCF and solved the coupled-mode equations using the 4th order Runge-Kutta method. For the first device, we obtained the passive three-input OR and AND all-optical logic gates, which operated with high performance, so they could be used to replace more complex optical circuits (in which the occurrence of Boolean expressions like the three-input OR and three-input AND are very common) without the need for concatenation therefore saving space and eliminating problems regarding the cascading of logic gates. For the second device, we obtained the active two-input OR and AND all-optical logic gates, which operated with exceptionally high contrast ratios and could therefore be used in optical signals processing.

A type of all-optical logic gate based on graphene surface plasmon polaritons

In this paper, a novel type of all-optical logic device based on graphene surface plasmon polaritons (GSP) is proposed. By utilizing linear interference between the GSP waves propagating in the different channels, this new structure can realize six different basic logic gates including OR, XOR, NOT, AND, NOR, and NAND. The state of “ON/OFF” of each input channel can be well controlled by tuning the optical conductivity of graphene sheets, which can be further controlled by changing the external gate voltage. This type of logic gate is compact in geometrical sizes and is a potential block in the integration of nanophotonic devices.

Computational analysis of solitons all-optical logic NAND and XNOR gates using semiconductor optical amplifiers

Solitons all-optical logic NAND and XNOR gates using semiconductor optical amplifiers-assisted Mach–Zehnder interferometers are computationally analyzed at a data rate of 80 Gb/s. The investigation of the output quality factor is included. All-optical logic gates are capable of operating at 80 Gb/s with logical correctness and acceptable quality.

Realization of all optical logic gates using universal NAND gates on photonic crystal platform

In this paper, the design of all-optical logic gates using the combination of universal NAND gates has been proposed. The photonic crystal structure consists of triangular lattice arrangement of air holes in silicon. Initially, the all optical NAND gate has been designed and optimized. Further, the optimized NAND gates have been used and arranged in a combination such that the combined structure behaves as an all-optical logic gate specifically, NOT, AND, OR, XOR and XNOR. The truth table for the designed all-optical logic gates has been verified at an operating wavelength of 1.55 μm. The proposed all optical gates exhibit a response period of 2.168 ps with a bit rate of 0.461 Tb/sec. Further, the contrast ratio for the designed gates has also been obtained.

A new modulation method to generate all-optical logic gates in an AOTF

We propose a new method of optical modulation using a conventional acousto-optic tunable filter. In this device the all-optical logic gates, namely AND and OR, are obtained by simultaneously operation of optical double sideband (ODSB) modulation and a pulse position frequency domain modulation (PPFDM). This device shall operate with ultrashort soliton light pulses 100 ps. In this way, a pulse will carry two bits of information after been encoded by the modulation proposed here. We then analyze the modulation ODSB—PPFDM for input pulses, polarized in the two input modes, allowing a variation in the modulation parameter for each input pulse. A phase difference Δϕ = π rad was considered between both input pulses, it was obtained the occurrence of an AND (OR) logical gate at lower (upper) sideband of the TE output pulse as well as at upper (lower) sideband of the TM output pulse.

Symmetry-protected collisions between strongly interacting photons.

Realizing robust quantum phenomena in strongly interacting systems is one of the central challenges in modern physical science. Approaches ranging from topological protection to quantum error correction are currently being explored across many different experimental platforms, including electrons in condensed-matter systems, trapped atoms and photons. Although photon-photon interactions are typically negligible in conventional optical media, strong interactions between individual photons have recently been engineered in several systems. Here, using coherent coupling between light and Rydberg excitations in an ultracold atomic gas, we demonstrate a controlled and coherent exchange collision between two photons that is accompanied by a π/2 phase shift. The effect is robust in that the value of the phase shift is determined by the interaction symmetry rather than the precise experimental parameters, and in that it occurs under conditions where photon absorption is minimal. The measured phase shift of 0.48(3)π is in excellent agreement with a theoretical model. These observations open a route to realizing robust single-photon switches and all-optical quantum logic gates, and to exploring novel quantum many-body phenomena with strongly interacting photons.

Multi-mode interference-based photonic crystal logic gates with simple structure and improved contrast ratio

We present a MMI-based photonic crystal all-optical logic gate structure for logic functions such as XNOR, XOR, OR and NAND with square-type lattice of Si rods in air host. Phase-based logic inputs produce intensity-based logic outputs with high contrast ratio. The calculated ON to OFF contrast ratio for the logic functions XNOR/XOR and OR/NAND is 40.41 and 37.40 dB, respectively. Further, it is improved by 11.53 and 12.46% for XNOR/XOR and OR/NAND logic functions, respectively, by reducing the back reflection with the introduction of absorbing waveguides. The structure in both the forms has a fast response period that is less than or equal to 0.131 ps. The size of the structure is quite compact with dimension \(6.4\,\upmu \hbox {m} \times 8.8\,\upmu \hbox {m}\).