We have proposed an ultracompact all-optical photonic crystal AND gate based on nonlinear ring resonators, consisting of two Kerr nonlinear photonic crystal ring resonators inserted between three parallel line defects. We have employed a Si nanocrystal as the nonlinear material for its appropriate nonlinear properties. The gate has been simulated and analyzed by finite difference time domain and plane wave expansion methods. The proposed logic gate can operate with a bit rate of about 120 Gbits/s.

All-optical ultracompact photonic crystal AND gate based on nonlinear ring resonators

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 $$277\,\text{ mW}/\upmu \text{m}^{2}$$
 . 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 $$1.55\,\upmu \text{m}$$
 . Since the structure has a simple geometric shape with clear operating principle, it is potentially applicable for photonic integrated circuits.

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

The arrival of the big data era has driven the rapid development of high-speed optical signaling and processing, ranging from long-haul optical communication links to short-reach data centers and high-performance computing, and even micro-/nano-scale inter-chip and intra-chip optical interconnects. On-chip photonic signaling is essential for optical data transmission, especially for chip-scale optical interconnects, while on-chip photonic processing is a critical technology for optical data manipulation or processing, especially at the network nodes to facilitate ultracompact data management with low power consumption. In this paper, we review recent research progress in on-chip photonic signaling and processing on silicon photonics platforms. Firstly, basic key devices (lasers, modulators, detectors) are introduced. Secondly, for on-chip photonic signaling, we present recent works on on-chip data transmission of advanced multi-level modulation signals using various silicon photonic integrated devices (microring, slot waveguide, hybrid plasmonic waveguide, subwavelength grating slot waveguide). Thirdly, for on-chip photonic processing, we summarize recent works on on-chip data processing of advanced multi-level modulation signals exploiting linear and nonlinear effects in different kinds of silicon photonic integrated devices (strip waveguide, directional coupler, 2D grating coupler, microring, silicon-organic hybrid slot waveguide). Various photonic processing functions are demonstrated, such as photonic switch, filtering, polarization/wavelength/mode (de)multiplexing, wavelength conversion, signal regeneration, optical logic and computing. Additionally, we also introduce extended silicon+ photonics and show recent works on on-chip graphene-silicon photonic signal processing. The advances in on-chip silicon photonic signaling and processing with favorable performance pave the way to integrate complete optical communication systems on a monolithic chip and integrate silicon photonics and silicon nanoelectronics on a chip. It is believed that silicon photonics will enable more and more emerging advanced applications even beyond silicon photonic signaling and processing.

On-chip silicon photonic signaling and processing: a review

In this paper, a nonlinear photonic crystal structure is proposed in order to implement all-optical NOT and OR logic gates. The proposed structure includes combiners and limiters. The limiters are designed using ring resonator. Also, the combiners are optimized with changing the radius of rods near the crosspoint of waveguides in order to enhance the performance of structure. Nonlinear rods of proposed structure are made of silicon nanocrystal which has been used in order to create the frequency shift for different values of input power. Plane wave expansion and finite difference time domain methods have been utilized to simulate the performance of proposed logic gate. Simulation results show that the ON–OFF logic-level extinction ratio and bit rate are −18.7 dB and 333 Gbit/s, respectively.

All-optical photonic crystal NOT and OR logic gates using nonlinear Kerr effect and ring resonators

Photonic crystals are considered as the suitable structures for creating all-optical processors because of low loss and high capability in guiding and controlling the light. This paper contains a comprehensive review of the principles, different types of designing methods and operational improvements of optical logic gates. The presented designs are investigated and categorized into three groups of all-optical photonic crystal logic gates based on interference waveguides, resonator structures and self-collimation phenomenon. Two former structures can be designed by utilizing linear or nonlinear materials while the later one performs just in linear regime and is independent from the input beam intensity. In general, the main purpose of previously accomplished studies has been presenting the designs to be resulted in broad operational bandwidth, low power consumption, high switching speed, high contrast ratio and excellent integration capability by trading off between different parameters. Also a comprehensive study has been done on the advantages and disadvantages of different design methods.

Photonic crystal logic gates: an overview

All-optical flexible 20-Gb/s logic and gate based on cascaded sum- and difference-frequency generation in a periodically poled lithium niobate waveguide is proposed and experimentally demonstrated. The theoretical analyses further indicate that 40-, 80-, and 160-Gb/s ultrahigh-speed logic and operations can potentially be performed. Moreover, it is expected that the and output can be tuned in a wide wavelength range (67 nm) with slight fluctuation of the Q-factor and extinction ratio.

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PPLN-Based Flexible Optical Logic and Gate

We report the single-to-multiple channel wavelength conversions of 1.57-ps pulses based on cascaded second-harmonic generation and difference frequency generation in quasi-phase-matched periodically poled lithium niobate waveguides. For single-to-single channel wavelength conversion, no external cavity laser is required with use of a fibre ring laser. The conversion efficiency is about -21.44 dB. The converted idler wavelength can be tuned from 1526.4 nm to 1537.5 nm as the lasing pump wavelength is varied from 1566.1 nm to 1555.0 nm. By employing several input pumps, tunable single-to-dual and single-to-triple channel wavelength conversions are experimentally demonstrated.

Single-to-Multiple Channel Wavelength Conversions and Tuning of Picosecond Pulses in Quasi-Phase-Matched Waveguides

The development of excessively tilted fiber gratings (Ex-TFGs) provides a new type of sensing device with high refractive index (RI) sensitivity, low thermal crosstalk and vector sensing property Due to the asymmetric grating structure of Ex-TFG, the light in the core is coupled into high order forward-propagating cladding modes and split into two orthogonal polarization states, resulting in dual-peak resonances in the transmission spectrum The Ex-TFG also exhibits a non-circularly symmetrical near field distribution, which endows an exceptional orientation sensing capability Benefitting from the unique mode coupling behavior, Ex-TFGs have been studied and developed for many different sensing applications, such as polarization dependent torsion and loading sensors, vector accelerometer and magnetometer, and a variety of low thermal crosstalk bio/chemical sensors This paper will review the recent study and development of Ex-TFGs in terms of mode coupling mechanism, fabrication method, transmission and sensor characteristics and the novel applications in sensing areas

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Excessively Tilted Fiber Grating Sensors

Optical fiber distributed acoustic sensing (DAS) based on phase sensitive optical time domain reflectometry (ϕ-OTDR) has a great demand in many application fields with large signals, such as railway safety monitoring, cable vibration detection, etc. However, due to the inherent limits of phase unwrapping algorithm, the large signal whose phase change exceeds π cannot be recovered correctly by DAS. In this work, the differential-unwrapping-integral (DUI) algorithm is proposed and demonstrated to replace the traditional unwrapping algorithm for large signal recovery. By utilizing differential operation to compress the signal amplitude, the large phase signal can be converted into small signal which can be recovered through unwrapping. Then, multiple integral operations and polynomial fitting compensation algorithm are applied onto the differential signal to recover the original phase signal without any signal-to-noise ratio(SNR) sacrificed. In theory, the maximum measurable phase of DUI can be improved 1390 times compared with traditional DUI algorithm. Further, the experimental results demonstrate that the dynamic range of DAS with DUI can reach up to 131.7 dB. Moreover, DUI algorithm has been tested and verified in the field test for recording the digging signals with large amplitude. This scheme can be applicable for all phase-demodulation-based sensing techniques without increasing the system complexity.

Sun Qizhen

Papers

PPLN-Based Flexible Optical Logic and Gate

Single-to-Multiple Channel Wavelength Conversions and Tuning of Picosecond Pulses in Quasi-Phase-Matched Waveguides

Excessively Tilted Fiber Grating Sensors

Large Dynamic Range Optical Fiber Distributed Acoustic Sensing (DAS) With Differential-Unwrapping-Integral Algorithm

Theoretical investigation on refractive index sensor basedon Bragg grating in micro/nanofiber