All-optical logic gates and a half-adder based on lithium niobate photonic crystal micro-cavities

All-optical logic gates including AND, XOR, and NOT gates, as well as a half-adder, are realized based on twodimensional lithium niobate photonic crystal(PhC) circuits with Ph C micro-cavities. The proposed all-optical devices have an extinction ratio as high as 23 dB due to the effective all-optical switch function induced by twomissing-hole micro-cavities. These proposed devices can have potential implementation of complex integrated optical functionalities including all-optical computing in a lithium niobate slab or thin film.     

Concurrent implementation of all-optical half-adder and AND & XOR logic gates based on nonlinear photonic crystal

A new design for concurrent implementation of all-optical half-adder and AND & XOR logic gates based on nonlinear photonic crystal ring resonator has been proposed. The finite different time domain and plane wave expansion methods are used to analyze the behavior of the structure. The ring resonator has a low switching time of about 0.85 ps and low switching power equal to $277\,\text{ mW}/\upmu \text{m}^{2}$ 277 mW / μ m 2 . The simulation results show that the contrast ratio is 12.78 dB for AND gate and 5.67 dB for XOR gate. Moreover, the operational wavelength of the input ports is $1.55\,\upmu \text{m}$ 1 . 55 μ m . Since the structure has a simple geometric shape with clear operating principle, it is potentially applicable for photonic integrated circuits.     

All optical NOR and NAND gate based on nonlinear photonic crystal ring resonators

In this paper we proposed optical NOR and NAND gates. By combining nonlinear Kerr effect with photonic crystal ring resonators first we designed a structure, whose optical behavior can be controlled via input power intensity. The switching power threshold obtained for this structure equal to 2 kW/μm². For designing the proposed optical logic gates we employed two resonant rings with the same structures, both rings at the logic gates were designed such that their resonant wavelength be at λ = 1550 nm. Every proposed logic gate has one bias and two logic input ports. We used plane wave expansion and finite difference time domain methods for analyzing the proposed structures.     

Design of on-chip optical logic gates in 2D silicon photonic crystal slab

Optical Review - We have demonstrated the design of two types of on-chip optical logic gates in 2D silicon PC slab, which can support AND and XOR logic gate functions at different input...     

Compact design of on-chip silicon photonic crystal AND and XOR logic devices based on the directional leakage

Optical Review - We have provided two compact designs of on-chip silicon photonic crystal (PhC) AND and XOR logic devices, which can provide multiple logic functions through different input...     

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.     

Multiple-output logic element based on an optical interference system

A multiple-output logic element using an optical interference system is proposed. The system acts as a logic gate array operating in parallel at certain positions divided over one period of the output fringe. A photoinduced refractive-index change material is incorporated in the system to perform the optical transformation of optical inputs into the phase change of a readout beam. It is shown that the logic gates obtained can be controlled arbitrarily in number and sorts by adjusting either the shift or the division of the output fringe. As an example, logic gates of AND, OR, NAND, NOR are implemented in parallel in the preliminary experiments.     

Design of ultra compact all-optical XOR and AND logic gates with low power consumption

We propose a novel ultra-compact all-optical XOR and AND logic gates without using nonlinear optics. In order to realize these devices, we adopt photonic crystal waveguides (PCWs) based on multi-mode interference devices. Numerical results show that the operating bandwidth of the ON to OFF logic-level contrast ratio of not less than 6.79 dB is 35 nm for XOR logic gate and 9 nm for AND logic gate. Proposed logic gates have the potential to be key components for an optical packet switching system due to their small feature sizes and low power consumption.     

Silicon nano crystal filled ellipse core based quasi photonic crystal fiber with birefringence and very high nonlinearity

In this paper, we have proposed a new type of quasi photonic crystal fiber (PCF) with a silicon nano crystal core. This structure can be used to sense aqueous analysis over a wavelength range of 1.00?µm to 3.00?µm. The properties of this structure are simulated using the vector-finite element method (VFEM) employing a boundary condition. The proposed model provides a significant effect of birefringence and a very high nonlinear coefficient for two different fundamental modes, which are obtained by adjusting the size of the silicon nano crystal filled ellipse core. This provides a high nonlinearity of 4.2?×?10⁵ W^?1Km^?1 and a birefringence of ? 3.2?×?10^?1 at the wavelengths 1.00?µm and 3.00?µm, respectively. Some others properties, such as the effective area, scattering loss, confinement loss, numerical aperture (NA)and power fraction are also analyzed to measure the performance of this structure. The proposed model is useful for sensing and biomedical imaging applications. The proposed structure may also find extensive applications in optical communication and sensor systems.     

Gold Nanoparticles‐Based DNA Logic Gate for miRNA Inputs Analysis Coupling Strand Displacement Reaction and Hybridization Chain Reaction

The molecular level DNA logic gates assisted by nanomaterials hold great promise for disease diagnosis applications. However, designing convenient and sensitive logic gates for molecular diagnostics still remains challenging. In this work, a DNA logic gate platform for miRNA inputs analysis based on the observation of localized surface plasmon resonance variation of gold nanoparticles (AuNPs) is fabricated. As a demonstration, two biomarkers to differentiate indolent and aggressive forms of prostate cancer, miR‐200c and miR‐605, are selected as examples of logical inputs. In addition, five DNA probes are designed according to strand displacement reaction and hybridization chain reaction which are required for DNA logical operation. Since target miRNA inputs are able to trigger DNA structural transformations, which are further used to precisely regulate salt‐induced AuNPs aggregation, miRNA inputs information can be converted to the information of AuNPs states as outputs. This developed system performs amplified detection of low‐abundant target miRNAs without the requirement of any enzymes. In addition, single base‐pair mismatched miRNAs can be effectively differentiated. High‐order logic gates can also be developed with further modifications. Therefore, the DNA AND logic gate is successfully constructed with flexible operations, which has potential in biochemical study and disease diagnosis.     

Photonic crystal cavities and integrated optical devices

This paper gives a brief introduction to our recent works on photonic crystal (PhC) cavities and related integrated optical structures and devices. Theoretical background and numerical methods for simulation of PhC cavities are first presented. Based on the theoretical basis, two relevant quantities, the cavity mode volume and the quality factor are discussed. Then the methods of fabrication and characterization of silicon PhC slab cavities are introduced. Several types of PhC cavities are presented, such as the usual L3 missing-hole cavity, the new concept waveguide-like parallel-hetero cavity, and the low-index nanobeam cavity. The advantages and disadvantages of each type of cavity are discussed. This will help the readers to decide which type of PhC cavities to use in particular applications. Furthermore, several integrated optical devices based on PhC cavities, such as optical filters, channel-drop filters, optical switches, and optical logic gates are described in both the working principle and operation characteristics. These devices designed and realized in our group demonstrate the wide range of applications of PhC cavities and offer possible solutions to some integrated optical problems.     

Demonstration of temperature resilient properties of 2D silicon carbide photonic crystal structures and cavity modes

In this paper, photonic crystal (PhC) based on two dimensional (2D) square and hexagonal lattice periodic arrays of Silicon Carbide (SiC) rods in air structure have been investigated using plane wave expansion (PWE) method. The PhC designs have been optimized for telecommunication wavelength (λ = 1.55 μm) by varying the radius of the rods and lattice constant. The result obtained shows that a photonic band gap (PBG) exists for TE-mode propagation. First, the effect of temperature on the width of the photonic band gap in the 2D SiC PhC structure has been investigated and compared with Silicon (Si) PhC. Further, a cavity has been created in the proposed SiC PhC and carried out temperature resiliency study of the defect modes. The dispersion relation for the TE mode of a point defect A1 cavity for both SiC and Si PhC has been plotted. Quality factor (Q) for both these structures have been calculated using finite difference time domain (FDTD) method and found a maximum Q value of 224 for SiC and 213 for Si PhC cavity structures. These analyses are important for fabricating novel PhC cavity designs that may find application in temperature resilient devices.     

Optics design and fabrication of 3D electrically switchable hexagonal photonic crystal

We demonstrate a holographic approach for easy and large-area fabrication of 3D photonic crystal (PhC) microstructures in a polymer-dispersed liquid crystal (PDLC) by applying a single top-cut hexagonal prism and a seven-beam interference system. Based on the expected photonic band gap of the photonic crystal, the prism parameters are designed and optimized. For example, a prism with a height h=3.73 cm and a cross angle α=66° between the side face and the base is used to fabricate 3D PhC hexagonal symmetrical structures in PDLCs. A good agreement is obtained between the theoretical calculation of the interference intensity and morphological structures. On the other hand, far-field diffraction patterns and electrical switching characteristics are also investigated. PACS 42.15.Eq; 42.40.Eq     

All optical switching in henna thin film

The optical nonlinearity in henna (Lawson (2- hydroxyl-1,4 naphthoquinone) film was utilized to demonstrate all optical switching. The nonlinear absorption of the henna film was calculated by measuring the transmission of the laser beam (λ = 488 nm) as a function of incident light intensities. The observed nonlinear absorption is attributed to a two-photon absorption process. The pump and probe technique was used to demonstrate all optical switching. The switching characteristics can be utilized to generate all-optical logic gates such as simple inverter switches (NOT) NOR, AND NAND logic functions.     

Reconfigurable photonic crystal circuits

We describe progress in the field of tuning, (re)configuration of Photonic crystal (PhC) based devices with a particular emphasis on our recent concepts and techniques that we have developed to tune and/or reconfigure the properties of photonic crystal nanocavities. We show how our hybrid approach based on photosensitive material and tapered silica fiber can tune the (Q, λ) properties of preexisting Photonic crystal cavities. We describe our alternative techniques to create ‘a posteriori’ spatially (re)configurable high‐Q cavities in a PhC platform. We show that optofluidics – the fusion of microfluidics with photonic devices – offers an unquestionable added value to the quest of a truly versatile, (re)configurable photonic crystal based photonic chip.     

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.     

A Novel Proposal for an All-Optical “and” Logic Gate Using Two-Dimensional Photonic Crystals

We present a novel proposal for an all-optical AND logic gate. It is designed based on line and point defects in two-dimensional photonic crystal (PC) rods in air with square lattice. Material of the rods is silicon with dielectric constant 11.56. Dimension of the proposed device is equal to 12.155×12.155 μm. The device elaborated has a simple structure consisting of two inputs – a main output and two idler outputs. Bit rate of the device is equal to 3·10¹² bit/s. Maximum contrast ratio is 5.84 dB. It is a good candidate for optical integrated circuits.     

基于半导体光纤环形腔激光器的新型全光AND门和NOR门

提出了一种新型的基于半导体光纤环形腔激光器(SFRL)中同时发生的四波混频效应和交叉增益调制效应同时实现全光AND门和NOR门方案，并建立了这种全光逻辑门完整的宽带理论模型.通过数值模拟的方法，研究了输入信号光峰值功率及SFRL中两个耦合器的耦合比对这种全光逻辑门输出特性的影响. 关键词： 半导体光纤环形腔激光器 全光逻辑门 四波混频 交叉增益调制     

Simulation of two photon absorption in silicon wire waveguide for implementation of all optical logic gates

All optical switching action of silicon wire waveguide for the design of the proposed logic gates is simulated. This is one possible building block of the future all optical computer or photonic devices. All optical logic gates NOT, NAND and AND gates using two photon absorption in silicon wire waveguide are presented. Use of ultra short pulse has negligible free carrier absorption effect; hence the operating speed of the gates is very high and has potential application in photonic processing. NAND gate is universal one and thus one can perform any logical operation using this. The device (Si wire WG) requires low energy pulse and is ultrafast one.     

Bioinspired Nanozymes with pH‐Independent and Metal Ions‐Controllable Activity: Field‐Programmable Logic Conversion of Sole Logic Gate System

In nature, different environmental factors make organisms to be programmed into different forms. However, it is difficult and significant to realize the field‐programmable logic conversion of sole logic system for molecular logic gates. Here, the concept of pH‐programmable “logic conversion” on the single logic gate based on the peculiar enzyme‐mimicking activity is presented. Inspired by natural enzymes with high pH‐stability and metal ions‐stimulated activity, pH‐independent and metal ions‐controllable catalase mimics (Co₃O₄ nanozymes) are designed by protein‐directed method. Although pH cannot directly change the activity of nanozymes, pH can change the existence state of metal ions and then the electron transfer rate on nanozymes. So, versatile roles of metal ions for catalase‐like and electrocatalytic activities are discovered on the premise of pH‐independency. For the proof‐of‐concept, OR/INHIBIT‐ and INHIBIT/AND‐switchable logic gates are facilely constructed using pH as the environmental stimulus and metal ions as inputs. Hence, the transformation of logic gate functions is realized without the change of logic gate elements and input molecules. This contribution may not only broaden the species and application area of nanozymes, but also open novel avenues for the molecular logic conversion and the metal ions sensor.