Extinction Contrast Research Articles

All-optical logic gates based on optimized coherent perfect absorber and fuzzy inference system

All-optical logic gates (AO-LGs) are key elements that play a pivotal role in the development of future all-optical computing and all-optical computers. In this paper, benefiting from particle swarm optimization (PSO), an optimized metasurface unit cell in the far-infrared (FIR) frequency band is presented as the basis of four port controlling light with the light system. This system, known as coherent perfect absorption (CPA), could be applied as AO-LGs in certain conditions. NOT, AND, OR, NAND, NOR, XOR, and XNOR logic gates can be implemented with the proposed method. The remarkable innovation of this article is the use of a fuzzy inference system (FIS) instead of a crisp threshold. Different calculated parameters like extinction ratio (ER = 96.2 dB), contrast ratio (CR = 99.54 dB), amplitude modulation (AM = 0.7 dB), and eye-opening (EO = 99%), besides the possibility of utilizing the proposed system for various kind of CPA films, prove the impressive effects of FIS applying as a novelty in this work. Small dimensions and low power consumption are other characteristics of the proposed method that are obtained as a result of using optimized metasurface-based CPA.

All-optical matching systems based on the squarer for QPSK and 8PSK optical signals

Photonic firewall which can conduct the data identification and intrusion detection directly at the optical layer is a high-speed and low-energy network security equipment. For the photonic firewall, the all-optical matching system is the core part. This paper focuses on designing all-optical matching systems for high-order phase modulated optical signals. Based on the squarer, two all-optical matching systems are designed for Quadrature Phase Shift Keying (QPSK) and 8 Phase Shift Keying (8PSK) optical signals respectively. The systems mainly consist of squarers, multiplexers, AND gates and regenerators. The squarer is implemented based on the four-wave mixing (FWM) effect of highly nonlinear fiber (HNLF). The theoretical analysis and simulation verification are conducted for the proposed system. The performances of feasibility and noise impact are evaluated for the proposed system with the data rate of 100 Gbaud. The results show that the system can correctly identify and localize the target sequence with the length of 4 and 8 symbols in the data sequence with the length of 16 symbols. The impact of noise is evaluated by the extinction ratio (ER) and contrast ratio (CR). The ER of two all-optical matching systems reaches 0 dB when the optical signal-to-noise ratio (OSNR) of input optical signal is about 5.59 dB and 9.24 dB respectively. The CR of two all-optical matching systems reaches 0 dB when the OSNR of input optical signal is about 4 dB and 8.62 dB respectively.

Comparing extinction and contrast effects for operant wheel running and lever pressing on a multiple schedule

Extinction and positive contrast effects were assessed on a multiple schedule with lever pressing as the operant in one component and wheel running as the operant in the other component. FR 15 schedules produced 15% sucrose reinforcement in each component. Contrast for both operants was generated by placing responding in the alternate component on extinction. Results showed that extinction decreased and contrast increased both lever-pressing and wheel-running rates. However, the magnitude of the changes was greater for lever pressing. Extinction increased and contrast decreased postreinforcement pause (PRP) duration for lever pressing, but for wheel running, extinction decreased PRP duration while contrast did not change PRP duration. Finally, outcomes for lever pressing decreased with extinction and increased with contrast, but for wheel running, outcomes did not change with extinction and increased with contrast. These differences in contrast and extinction effects were explained by an automatic reinforcement effect generated by wheel-running, but not lever pressing. These findings provide further support for an automatic reinforcement effect generated by wheel running.

Reconfigurable all-optical pattern-matching system for phase modulation formats based on phase-sensitive amplification in highly nonlinear fiber

All-optical pattern-matching system is to compare the input data with the target sequence to implement the data filtering directly in the optical layer. However, for current all-optical pattern-matching systems, one pattern-matching system can only match one modulation format, which limits its application. In this paper, a reconfigurable all-optical pattern-matching system for phase modulation formats is proposed. Taking advantage of phase-sensitive amplification (PSA) in highly nonlinear fiber (HNLF), the system can match various phase modulation formats through optical switches configured by a controller. We first evaluate the feasibility of the proposed system for binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modulation formats with the transmission rates of 100 Gbaud and 200 Gbaud. The results show that our proposed system can correctly recognize and locate the position of the target sequence. Next, we analyze the extinction ratio (ER), contrast ratio (CR), Q factor, and bit error rate (BER) by changing the optical signal-to-noise ratio (OSNR) values of BPSK and QPSK signals to evaluate the noise performance. The proposed reconfigurable all-optical pattern-matching system provides an effective method to recognize signals with different phase modulation formats, which is suitable for future dynamically reconfigurable optical networks.

Silicon microring resonator based all-optical 3-input majority gate and its applications

In this study, we propose an all-optical majority gate using silicon waveguide-based microring resonator for the first time to our knowledge. All-optical microring resonator based majority gate has attractive properties such as energy-efficient, ultra-high-speed, and compact which are essential for optical computing. We have designed different logic circuits such as AND, OR, NOR, NAND, and one-bit full adder by exploiting the majority gate with inverter circuits. Optoelectronic conversion which limits the operational speed is avoided in our design. The operational speed of our design is nearly 260 Gbps. The required pump power for switching is only 1.66 mW for micro-ring resonator based switch which is very less comparatively. These designs have been realized in MATLAB as well as in Ansys Lumerical finite difference time domain (FDTD) simulation platform. The "figure of merits" of the presented majority gate is achieved numerically through simulation. The obtained values of extinction ratio and contrast ratio are much higher for the proposed majority gate and the values are 28.11 dB and 32.88 dB, respectively. The on-off ratio is also high for single microring resonator and it is 38.2 dB.

Ultrafast All-Optical Switching Using Doped Chromoprotein Films

Next-generation communication networks require > Tbit/s single-channel data transfer and processing with sub-picosecond switches and routers at network nodes. Materials enabling ultrafast all-optical switching have high potential to solve the speed limitations of current optoelectronic circuits. Chromoproteins exhibit a large light-controlled refractive index change alleviating the driving energy requirements for optical switching. Here, we report femtosecond transient grating experiments demonstrating the feasibility of < 200 fs all-optical switching by hydrated thin films of photoactive yellow protein and compare the results with those obtained using bacteriorhodopsin. Possibilities for the practical utilization of the scheme in extremely high-speed optical modulation and switching/routing with nominally infinite extinction contrast are discussed.

All optical comparator using tera hertz optical asymmetric demultiplexer (TOAD)

TOAD or Tera Hertz Optical Asymmetric Demultiplexer is an optical switch. Using this switch, we have invented an optical comparator. This optical comparator circuit is very simple in structure with a higher speed (200 Gbps) and finds useful application in optical computation and communication network system. We have simulated all three outputs in detail and shown the eye diagram of all three outputs of the optical comparator. We found high values of extinction ratio (ER), contrast ratio (CR), and quality factor (Q value) for the three outputs of the comparator.

Design of electro-optic Mach–Zehnder interferometer based all-optical binary half adder and half subtractor

By exploiting the phenomena of optical switching, different logical and arithmetic operations can be performed. This paper presents a novel optimized design structures to perform addition and subtraction of two binary digits using electro-optic effect based Mach–Zehnder interferometer operating at 1460 nm in the S band. The proposed structures are numerically simulated and designed using beam propagation method and MATLAB software. The different performance parameters like extinction ratio, contrast ratio, insertion loss, amplitude modulation and relative eye opening have been evaluated and the optimized structure yields maximum ER of 33.22 dB and 28.76 dB for half adder and half subtractor respectively. Additionally, a comparison of the proposed structures is presented with the previously designed structures.

Ultrafast Electro‐Absorption Switching in Colloidal CdSe/CdS Core/Shell Quantum Dots Driven by Intense THz Pulses

AbstractNext‐generation high‐speed optical networks demand the development of ultrafast optical interconnects capable of Tbit s−1 data rates. By utilizing colloidal CdSe/CdS core/shell quantum dots, gated by intense THz pulses, a proof of concept of an all‐optical femtosecond electro‐absorption switch is presented in this work. Without any additional enhancement of the THz electric field, an extinction contrast of more than 6 dB and transmission changes in the visible of more than 15% are achieved, with the latter setting a new record for solution‐processed electro‐absorption materials at room temperature. The absence of physical artifacts, originating from electrodes and field enhancing structures, allows to employ a simple and intuitive numerical model, which rationalizes the large field‐induced electro‐absorption response. Supported by theoretical calculations, the importance of the energy band alignment of heterostructure quantum dots are discussed for the first time and suggest that further improvement of the modulation depth and contrast may be achieved with Type‐II quantum dots.

Design and modeling of multi-operation bit-manipulator logic circuit using lithium niobate waveguides

Abstract In this work, a high-performance multioperation bit-manipulator is presented. The presented electro-optical design can perform several bit-manipulations such as bidirectional bit-shifting, bit-rotation, multiply-by-2 and divide-by-2, and sequence designing operation. The technique relies on the electrooptic principle in lithium niobate. Lithium niobate-based waveguides have been used to design Mach–Zehnder interferometer, which is the fundamental optical switching element of the whole model. Extinction ratio, contrast ratio, and insertion loss values computed for the simulated results are 29.16 dB, 29.48 dB, and 0.77 dB, respectively.

Design of all-optical Johnson counter using SOA-MZI at 100 Gb/s

All-optical networks utilize optical memory elements as the basic building blocks for optical signal processing and for providing high performance computing applications. In this communication, we propose and realize an integrable scheme for the design of all optical Johnson counter utilizing D flip flops (DFFs). All optical counter have been designed using cascaded DFFs memories and a single clock pulse have been applied as input to the counter. The DFF has been implemented by employing semiconductor optical amplifier - Mach Zehnder Interferometer (SOA-MZI) based all optical NAND and NOT gates. The performance of the device has been investigated in terms of extinction ratio, Q factor, amplitude modulation and contrast ratio verifying its operation at 100 Gb/s.

Polarization rotation-based all-optical AND gate using single semiconductor optical amplifier and implementation of a majority gate

Abstract Semiconductor optical amplifier-based polarization rotation is utilized in designing all-optical AND gate at 100 Gbps. The AND gate shows high extinction ratio (ER ∼ 15 dB), contrast ratio (CR ∼ 18 dB) and quality factor (Q-factor ∼ 16 dB). The effect of the amplified spontaneous emission noise on the performances is also investigated. The AND gate has relative eye opening (REO) varying from 93.52 to 97.1% for 10–30 dB unsaturated gain. Using the AND gate a majority voting gate is designed and analyzed and has Q ∼ 11.7 dB with REO ∼ 91%.

All-optical ripple carry adder based on SOA-MZI configuration at 100 Gb/s

Ripple carry adders are broadly used for the addition of n-bit input sequences in arithmetic and logic units and for performing packet-header processing in all optical packet switched networks. In this paper, we have proposed the novel design of 2-bit ripple carry adder based on semi-conductor optical amplifier- Mach Zehnder Interferometer (SOA-MZI) configuration at 100Gb/s. The XOR, OR and AND gates have been employed as basic gates in the design of ripple carry adder. The four input signals of the adder circuit and the resultant outputs attained are at the same wavelength. The performance of the proposed device has been analyzed in terms of extinction ratio(ER), contrast ratio(CR), quality factor(QF) and amplitude modulation(AM) at the output.

Design of multiplexing circuit using electro-optic effect based optical waveguides

Abstract The multiplexer is a combinational circuit that transfers multiple data inputs over a single output line. The input data are selected and transferred to the output line based on the selection line. In this work, 2 × 1 and 4 × 1 multiplexer is proposed. The proposed multiplexer has been worked out using the electro-optic principle. It is implemented using lithium niobate-based Mach–Zehnder interferometer (LN-MZI). LN-MZI is used as an optical switching device. The performance parameters extinction ratio, contrast ratio and insertion loss have been computed and found 31.31, 28.02 and 0.043 dB respectively.

All-optical integrated 2-to-4 decoder and 1-to-4 demultiplexer circuit with enable using SOA based MZI

Abstract In this paper, we propose an all-optical integrated 2-to-4 decoder and a 1-to-4 demultiplexer circuit using SOA based MZI (Mach–Zehnder Interferometer) architecture. The proposed device has been applied an enable signal along with two data input signals at the same wavelength. Four output signals from 2-to-4 decoder and 1-to-4 demultiplexer have been attained at the same wavelength. The output timing diagrams of 2-to-4 decoder and 1-to-4 demultiplexer for different input data conditions with clear eye opening patterns confirms the operation of the proposed logic device at 10 Gb/s. Maximum value of extinction ratio, contrast ratio and minimum value of amplitude modulation achieved for the different output waveforms are 12, 9.5 and 0.1 dB respectively. Easy integration with active and passive devices and simple architecture makes this device suitable for all-optical processing.

Design of Hamming Code Checker Using Titanium-Diffused Lithium Niobate-Based Waveguide

ABSTRACTThis work presents an electro-optic effect-based design for the widely used Hamming code for checking single bit errors in the received data. The structure is based on Mach-Zehnder Interferometer, designed using Titanium-diffused Lithium Niobate-based waveguides. The proposed device has been successfully tested using the beam propagation method. For a received 7-bit code, the three simultaneously generated check bits are combined to check the error position. Critical performance parameters like extinction ratio (24.39dB), contrast ratio (25.711dB), insertion loss (0.041dB), and amplitude modulation (0.079dB) calculated for the overall device are within acceptable limits for the feasibility of the device.

Label-Free Single-Molecule Imaging with Numerical-Aperture-Shaped Interferometric Scattering Microscopy.

Our ability to optically interrogate nanoscopic objects is controlled by the difference between their extinction cross sections and the diffraction-limited area to which light can be confined in the far field. We show that a partially transmissive spatial mask placed near the back focal plane of a high numerical aperture microscope objective enhances the extinction contrast of a scatterer near an interface by approximately T–1/2, where T is the transmissivity of the mask. Numerical-aperture-based differentiation of background from scattered light represents a general approach to increasing extinction contrast and enables routine label-free imaging down to the single-molecule level.

Investigation of Penetration Depth and Defect Image Contrast Formation in Grazing Incidence X-ray Topography of 4H-SiC Wafers

Synchrotron X-ray Topography has been shown to be a vital tool for the nondestructive characterization of defects in 4H-SiC crystals [1-2]. Techniques utilizing reflection geometry are particularly useful for discerning defects at different depths below the crystal surface. For example, in studying defects in SiC pin diode structures, which typically comprise a buffer layer homoepitaxially grown on a substrate, with the drift layer grown on top of the buffer layer, it is important to be able to discriminate the depth at which particular defect configurations reside. This is particularly important for the characterization of defects resulting from relaxation processes such as interfacial dislocations and half loop arrays [3]. There are generally two approaches adopted depending of the level of perfection of the crystal. In deformed regions (such as around dislocation cores) the penetration depth is simply determined by photoelectric absorption. In perfect regions it is determined by extinction. Extinction contrast predicts particularly shallow penetration depths in these geometries, whereas kinematical theory predicts much deeper penetration depths. However, even under the kinematical diffraction conditions, the penetration depth calculated theoretically by just considering a dislocation as a single line is much smaller than the value measured experimentally. In our study we compared two models involving different diffracting volumes. In one model, the volume is defined by the misorientation larger than the FWHM of the rocking curve in the vicinity of the dislocation core. In another model, the contrast is naturally formed by simulating the photoelectric absorption profile of the diffraction beam according to the local lattice plane tilt by assuming the dislocation image formation is dominant by orientation contrast. We will present a comparison between measured penetration depths in grazing incidence geometry with these two approaches and develop an optimized model to explain our observations. [1] Muller, G.S., et al., Volume production of high quality SiC substrates and epitaxial layers: Defect trends and device applications. Journal of Crystal Growth, 2012. 352(1): p. 39-42. [2] Dudley, M., et al., Characterization of 100 mm diameter 4H-Silicon carbide crystals with extremely low basal plane dislocation density, Material Science Forum,2001. 65: p. 353-356. [3] Wang, H., Dudley, M., et al., Studies of the Origins of Half-Loop Arrays and Interfacial Dislocations Observed in Homoepitaxial Layers of 4H-SiC. Journal of Electronic Materials, 2015. 44(5): p. 1268-1274

All-Optical 3:8 Decoder with the Help of Terahertz Optical Asymmetric Demultiplexer

An all-optical 3:8 decoder unit with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed. The all-optical 3:8 decoder unit with a set of all-optical full-adders and optical exclusive-ORs (XORs), can be used to perform a fast central processor unit using optical hardware components. We try to exploit the advantages of TOAD-based optical switch to design an integrated all-optical circuit which can perform decoding of signal. A theoretical model is presented and verified through numerical simulation. The new method promises both higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuit of enhanced functionality in which decoder is the basic building block. The operation of the proposed circuit is parallel in nature. The impact of the switching energy with small signal gain and variation of extinction ratio and contrast ration with control pulse energy of the switching outcome is explored and assessed by means of numerical simulations.

A scanning cavity microscope.

Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm2; we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems.