All optical active high decoder using integrated 2D square lattice photonic crystals

The paper introduces a novel all optical active high 2 × 4 decoder based on 2D photonic crystals (PhC) of silicon rods with permittivity of ε = 10.1 × 10^?11 farad/m. The main structure of optical decoder is designed using a combination of five nonlinear photonic crystal ring resonator, set of T-type waveguide, and line defect of Y and T branch splitters. The proposed structure has two logic input ports, four output ports, and one bias input port. The total size of the proposed 2 × 4 decoder is equal to 40 μm × 38 μm. 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 realization and the numerically simulation to confirm its operation and feasibility.     

A 2*4 all optical decoder switch based on photonic crystal ring resonators

Based on photonic crystal ring resonators and nonlinear Kerr effect in this paper, we proposed a 2*4 all optical decoder switch. Our proposed structure has two logic input ports and one bias input port. This decoder switch has four output ports. Via these two logic input ports, we control the bias signal to transfer toward which output port. We employed numerical methods such as plane wave expansion and finite difference time domain methods for analyzing the proposed structure.     

All-optical digital 4 × 2 encoder based on 2D photonic crystal ring resonators

The photonic crystals draw significant attention to build all-optical logic devices and are considered one of the solutions for the opto-electronic bottleneck via speed and size. The paper presents a novel optical 4 × 2 encoder based on 2D square lattice photonic crystals of silicon rods. The main realization of optical encoder is based on the photonic crystal ring resonator NOR gates. The proposed structure has four logic input ports, two output ports, and two bias input port. The photonic crystal structure has a square lattice of silicon rods with a refractive index of 3.39 in air. The structure has lattice constant ‘a’ equal to 630 nm and bandgap range from 0.32 to 044. The total size of the proposed 4 × 2 encoder is equal to 35 μm × 35 μm. The simulation results using the dimensional finite difference time domain and Plane Wave Expansion methods confirm the operation and the feasibility of the proposed optical encoder for ultrafast optical digital circuits.     

A novel proposal for all-optical compact and fast XOR/XNOR gate based on photonic crystal

In this paper, we aim to design an all-optical device, which can perform XOR and XNOR functions in a single structure. The proposed structure will be realized by cascading two nonlinear resonant rings. The functionality of the proposed structure is based on controlling the optical behaviour of optical rings via optical intensity. The final structure has one bias and two input control ports, along with two output ports. One port acts as an XOR and the other acts as an XNOR gate. The maximum delay times for the XOR and XNOR gates are 1.5 and 2.5?ps, respectively. Therefore, the working bit rates for the XOR and XNOR gates are 666 and 400?Gbit/s, respectively.     

A novel proposal for all optical 3 to 8 decoder based on nonlinear ring resonators

In this paper, a 3 to 8 optical decoder was proposed using nonlinear photonic crystal ring resonators. For realizing the 3 to 8 decoder, we combined seven 1 to 2 optical decoders. In the proposed structure, X, Y and Z serve as input ports. By combination of these ports, one can control which output port to be ON. The maximum time delay of the proposed structure is about 6?ps.     

Symmetric operating point for increasing the extinction ratio of semiconductor based optical loop mirrors

Terahertz optical asymmetric demultiplexors (TOADs) use a semiconductor optical amplifier in an interferometer to create an all-optical switch and have potential uses in many optical networking applications. Here we demonstrate and compare experimentally a novel and simple method of dramatically increasing the extinction ratio of the device using a symmetrical configuration as compared to a ‘traditional’ configuration. The new configuration is designed to suppress the occurrence of self-switching in the device thus allowing signal pulses to be used at higher power levels. Using the proposed configuration an increase in extinction ratio of 10 dB has been measured on the transmitted port whilst benefiting from an improved input signal power handling capability.     

The designs of a scalable optical packet switching architecture

Abstract

This paper proposes a new switching architecture to be used in all optical packet switching networks. The proposed switch is derived from an original 2 × ?2 two‐stage multi‐buffer switched delay line based optical switching node, known as an M‐Quadro node. By incorporating bypass lines into the M‐Quadro architecture and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. Furthermore, we show that such architecture is scalable for a generic multiple stages optical packet switch with a larger number of input/output ports.     

All-optical compact encoder assembled by polymer fibres

An all-optical encoder based on a 3 × 3 crossed structure was assembled by stacking three polymer fibres. The encoding functions were predicated theoretically and demonstrated experimentally with very good agreement. The total insertion loss of the device is about 1 dB and the extinction ratio is larger than 10 dB. The output state can be controlled by launching optical signals to different input port, and the input state can be identified according to the output state. We believe that the all-optical compact encoder would be used in high-density PICs.     

Structural and optical properties of phosphate-zinc-nickel oxide glasses for narrow band pass absorption filters

Novel two phosphate glass systems with compositions 50P₂O₅–30ZnO–20NiO and 50P₂O₅–30ZnO–20[NiCl_2–6H₂O] were prepared using a conventional melt-quench technique. The absorbance and transmittance were measured using a spectrophotometer in the spectral range between 190 and 1100 nm. The data demonstrates that the system acts as a narrow bandpass optical absorption filter, with a transmission band in the UV region of 311–376 nm, which is centred at 350 nm and has a full width half maximum (FWHM) of almost 34 nm, whereas, the red region is the UV region of 617–684 nm, and centred at 650 nm and has a full width half maximum (FWHM) of nearly 32 nm. However, the refractive index (n), optical band gap (E_opt), non-linear refractive index n₂, third order non-linear susceptibility χ⁽³⁾ and non-linear absorption coefficient β were also calculated. It was apparent that the non-linear refractive index, third order non-linear susceptibility and non-linear absorption coefficient increases by decreasing the optical energy gap. Finally, we investigated the structure of the prepared glasses by using Raman and FTIR spectra. We found that the local network structure based mainly on Q¹ and Q² tetrahedron units connected by P–O–P linkages.     

A fully integrated high IP1dB CMOS SPDT switch using stacked transistors for 2.4 GHz TDD transceiver applications

A transmit/receive (T/R) switch is an essential module of every modern time division duplex (TDD) transceiver circuit. A T/R switch with high power handling capacity in CMOS process is difficult to design due to capacitive coupling of radio frequency signals to the substrate. This paper proposes a single-pole-double-throw (SPDT) T/R switch designed in a standard Silterra 130 nm CMOS process for high-power applications like RFID readers. The results reveal that, in 2.4 GHz ISM band, the proposed switch exhibits a very high input P1dB of 39 dBm with insertion loss of only 0.34 dB and isolation of 40 dB in transmit mode but 1.08 dB insertion loss and 30 dB isolation in receive mode. Stacked thick-oxide triple-well transistors, resistive body floating and negative control voltages are used to achieve such lucrative performance. Moreover, the chip size of the designed switch is only 0.034 mm² as bulky inductors and capacitors are avoided. The Monte-Carlo and corner analyses confirm that the performance of the switch is also quite stable and reliable.     

Tunable all-optical switch/demultiplexer using nonlinear MMI waveguides

In this paper, a tunable optical switch/demultiplexer has been presented based on nonlinear multimode interference waveguides. The proposed structure can be utilized as a multi-wavelength optical switch or dynamic wavelength division demultiplexer. This dual application of the structure has been designed based on the cooperation of self-imaging and self-guiding phenomena of multimode waveguides. Simulation results show the mean value of insertion loss equal to ?1.91 dB for the switching application of structure. Also, the wavelengths with 3 nm channel spacing and almost 3 nm full width at half power of outputs can be received in the multiplexing application. Two-dimensional beam propagation method has been utilized in order to simulate and verify the performance of proposed device.     

Novel tunable dynamic tweezers using dark-bright soliton collision control in an optical add/drop filter

We propose a novel system of the dynamic optical tweezers generated by a dark soliton in the fiber optic loop. A dark soliton known as an optical tweezer is amplified and tuned within the microring resonator system. The required tunable tweezers with different widths and powers can be controlled. The analysis of dark-bright soliton conversion using a dark soliton pulse propagating within a microring resonator system is analyzed. The dynamic behaviors of soliton conversion in add/drop filter is also analyzed. The control dark soliton is input into the system via the add port of the add/drop filter. The dynamic behavior of the dark-bright soliton conversion is observed. The required stable signal is obtained via a drop and throughput ports of the add/drop filter with some suitable parameters. In application, the trapped light/atom and transportation can be realized by using the proposed system.     

On chip optical isolator based on non-linear silicon photonic crystal by using asymmetric engineering waveguide

We propose an optical isolator formed in a nanoscale structure based on non-linear silicon photonic crystal that can be easily realized on an optical integrated chip. The structure comprises an engineered waveguide that is coupled to a L₂ cavity. By using a passive ultra-compact cavity-based isolator, without changing incident characteristics such as mode or frequency in outputs, an admirable transmission contrast of 20.5 dB with a small insertion loss (in the forward direction) of ?14.8 dB is achieved. The isolator attains a broad isolating linewidth operation of 0.9 nm without bistability response that is outstanding in comparison with the currently proposed cavity-based isolators. The non-linear Fano resonances that are created by the interplay between the non-linearity and spatial asymmetry notion in the structure play a critical role in the isolator efficiency. In this study, the finite-difference time-domain and finite element methods are used for simulations.     

Novel all-optical logic gate using an add/drop filter and intensity switch

A novel design of all-optical logic device is proposed. An all-optical logic device system composes of an optical intensity switch and add/drop filter. The intensity switch is formed to switch signal by using the relationship between refraction angle and signal intensity. In operation, two input signals are coupled into one with some coupling loss and attenuation, in which the combination of add/drop with intensity switch produces the optical logic gate. The advantage is that the proposed device can operate the high speed logic function. Moreover, it uses low power consumption. Furthermore, by using the extremely small component, this design can be put into a single chip. Finally, we have successfully produced the all-optical logic gate that can generate the accurate AND and NOT operation results.     

Nonlinearity suppression of Mach–Zehnder modulator based on optical carrier processing in radio-over-fiber links

A highly linear transmitter that consists of a dual-drive Mach–Zehnder modulator (DD-MZM), an optical gain, and an optical phase shifter in radio-over-fiber links is proposed and demonstrated by simulation. The optical carrier is split equally with one part driving the DD-MZM, while the other part remaining unmodulated. By properly adjusting the magnitude and phase shift of unmodulated optical carrier, two kinds of main origins of third-order IMD (IMD3) have equal intensity and opposite phase, and cancel each other out. The comparison of the proposed technique and double-sideband modulation by MZM is presented. Simulation results shown that the spurious-free dynamic range of 125.3 dB Hz^2/3 is achieved, which is about 26 dB more than a quadrature biased MZM.     

Design and modelling of dispersion-engineered rib waveguide for ultra broadband mid-infrared supercontinuum generation

We report a dispersion-engineered As₂Se₃ chalcogenide glass rib waveguide structure for ultra broadband mid-infrared supercontinuum generation across molecular ‘fingerprint region’. The proposed rib waveguide structure offers non-linear coefficient as high as 18,250 W^?1 km^?1 at 2.5 μm. Supercontinuum spectrum spanning 2–15 μm, which not only covers the both atmospheric transparent windows (3–5 μm and 8–13 μm) in the mid-infrared domain but also covers the important molecular ‘fingerprint domain’, is obtained using only 4 mm-long rib waveguide structure. To the best of our knowledge, such broadband mid-infrared supercontinuum spectrum in As₂Se₃-based chalcogenide waveguide geometry is reported for the first time. The proposed design of rib waveguide has potential for robust, integrated and low-cost supercontinuum sources in various applications including frequency comb generation, chemical sensing, food quality control and early cancer diagnostics.     

A simultaneous all-optical half/full-subtraction strategy using cascaded highly nonlinear fibers

Using non-linear effects such as cross-gain modulation (XGM) and cross-phase modulation (XPM) inside two highly non-linear fibres (HNLF) arranged in cascaded configuration, a simultaneous half/full-subtracter is proposed. The proposed simultaneous half/full-subtracter design is attractive due to several features such as input data pattern independence and usage of minimal number of non-linear elements i.e. HNLFs. Proof of concept simulations have been conducted at 100 Gbps rate, indicating fine performance, as extinction ratio (dB) > 6.28 dB and eye opening factors (EO) > 77.1072% are recorded for each implemented output. The proposed simultaneous half/full-subtracter can be used as a key component in all-optical information processing circuits.     

Sparse monolithic compliant mechanisms using continuum structural topology optimization

A formulation for design of continuous, hinge‐free compliant mechanisms is developed and examined within a continuum structural topology optimization framework. The formulation makes use of two distinctly different sets of springs, the first of which are artificial springs of relatively large stiffness attached to the input and output ports of the mechanism model, and the second of which are springs attached only to the output port with smaller stiffnesses that represent the resistance of the workpiece as it is manipulated by the mechanism. The proposed formulation involves solving two nested optimization problems. In the inner problem the arrangement of a constrained amount of structural material is optimized to maximize the mechanism's mutual potential energy in response to a force loading at the input port while working against the stiff artificial springs on the input and output ports. As the relative stiffness of the artificial springs increases, the material continuity of the mechanism also increases to the point where de facto ‘hinge’ regions are eliminated. In the outer problem, the artificial springs are removed and one solves for an appropriate amount of structural material that yields the desired finite deformation compliance characteristics of the mechanism when working against the real workpiece resistance. Different aspects of the proposed formulation are demonstrated on a number of examples and discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Insertion loss in terms of four-port network parameters

Usually, power filters are characterised by their insertion loss (IL). By definition, the IL is applicable to two-port networks, but most filters have a higher number of ports. Single-phase power filters are four-port networks and measurements of their suppression characteristics require one measurement for the commonmode (CM) and another for the differential-mode (DM) IL. Normally, the measurement apparatus have unbalanced ports and CM measurements are relatively easy to perform. However, the DM measurements require balanced?unbalanced conversion at the input and output of the filter. Wideband transformers (baluns) are used for this conversion. Instead of measuring it directly, the CM or DM IL can be calculated from the four-port parameters of the filter. The equations for IL in terms of four-port network parameters are derived theoretically and verified experimentally. The adoption of four-port parameters in engineering practice would reduce the amount of measurement work and increase the reliability and repeatability of the results because the use of baluns or other changes in the equipment under test are not necessary.     

All-optical tunable dual Fano resonance in nonlinear metamaterials in optical communication range

Low-power, ultra-fast all-optical tunable dual Fano resonance was realized in a metamaterial coated with a non-linear nanocomposite layer composed of gold nanoparticle-doped polycrystalline barium strontium titanate and multilayer tungsten disulphide microsheets. A high non-linear refractive index of ?2.148 × 10^?11 m²/W was achieved in the nanocomposite material that originated in the non-linearity enhancement associated with the quantum confinement effect, the local-field enhancement effect, and reinforced interactions between photons and the multilayer tungsten disulphide microsheets. An ultra-low threshold pump intensity of 600 kW/cm² was obtained. An ultra-fast response time of 25.4 ps was maintained because of the fast relaxation dynamics of the bound electrons in the nanoscale polycrystalline barium strontium titanate grains. The large third-order non-linear responses of the metamaterial were confirmed with a high third harmonic generation conversion efficiency of 5.4 × 10^?5. This work may help to pave the way towards realization of ultra-high-speed information processing chips and multifunctional integrated photonic devices based on metamaterials.