High-efficiency ultra-fast all-optical photonic crystal diode based on the lateral-coupled nonlinear elliptical defect

An all-optical Fano-like diode featuring a nonlinear lateral elliptical micro-cavity and a reflecting column in the photonic crystal waveguide is proposed. The asymmetric micro-cavity is constructed by removing one rod and changing the shape of the lateral rod from a circle to an ellipse. A reflecting pillar is also introduced into the waveguide to construct an F–P cavity with the elliptical defect and enhance the asymmetric transmission for the incident light wave transmitting rightwards and le...     

Design of ultrahigh-contrast all-optical diodes based on coupled nonlinear photonic crystal defects

We design and investigate the unidirectional transmission behavior of coupled photonic crystal defects with instantaneous Kerr nonlinearity. Theoretical analysis based on coupled-mode theory and numerical simulations based on finite-difference time-domain techniques indicate that ultrahigh-contrast all-optical diodes can be achieved by properly misaligning the frequencies of the coupled cavities. The transmission contrasts of such configurations composed of three and four cavities are demonstrated to be as high as 518 and 7015, with 42.8% and 46.3% forward transmissions, respectively.     

Modeling of two-photon absorption in nonlinear photonic crystal all-optical switch

We present an approach of taking the two-photon absorption effect into account and apply it to analyze an all-optical switch by means of the finite-difference time-domain method. It is shown for a shortened model of the device that the impact of the two-photon absorption on the functionality of the device is drastic. Therefore, under realistic conditions, it should be borne in mind when designing all-optical devices.     

Band structures in nonlinear photonic crystal slabs

The finite-difference time-domain method was used to analyze band structures in two-dimensional Kerr-nonlinear photonic crystal slabs. A triangular lattice of circular air rods was considered. Results show red-shifting of the band structure due to the nonlinearity and the incident intensity. The red-shift of the band gap between the first and the second bands is maximal when the air rod radius is in the range 0.2a to 0.25a, where a is the period.     

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.     

基于六角格子光子晶体波导的高效全光二极管设计

提出了一种基于六角格子光子晶体波导微腔和Fabry-Perot(FP)腔非对称耦合的全光二极管结构, 它由一个包含非线性Kerr介质的高Q值微腔与一个光子晶体波导中的FP腔组成. 通过有限时域差分方法对其传输特性进行了仿真, 发现通过两腔的非对称耦合可以实现在特定光强度下的正向传输、反向截止的功能. 在靠近微腔方向光入射时, 特定强度的光可以激发非线性微腔的Kerr效应, 改变了Fano腔的共振频率, 从而变成透射状态. 而远离微腔方向光入射, 由于这个不对称的结构造成场局域的分布不对称, 激发微腔Kerr效应的光强还不够, 所以光不能透射. 所设计的全光二极管结构具有良好的性能参数: 最大透射率高和高透射比、光强阈值低和易于集成等.     

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.     

双光子吸收对光子晶体定向耦合全光开关的影响

 利用时域有限差分方法,在非线性条件下,考虑双光子吸收效应的同时,建立了分析2维光子晶体定向耦合波导光开关的模型。数值计算结果表明,对于长度较短的波导耦合器件,在强控制光和非线性条件下,双光子吸收效应会对波导的耦合作用产生一定的影响,从而改变入射光的透射特性,使光开关控制的动态过程发生变化。故而在设计全光开关器件时,对强控制光条件下的非线性双光子吸收效应有必要作为影响因素考虑进去。     

双光子吸收对光子晶体定向耦合全光开关的影响

利用时域有限差分方法,在非线性条件下,考虑双光子吸收效应的同时,建立了分析2维光子晶体定向耦合波导光开关的模型。数值计算结果表明,对于长度较短的波导耦合器件,在强控制光和非线性条件下,双光子吸收效应会对波导的耦合作用产生一定的影响,从而改变入射光的透射特性,使光开关控制的动态过程发生变化。故而在设计全光开关器件时,对强控制光条件下的非线性双光子吸收效应有必要作为影响因素考虑进去。     

基于高非线性光子晶体光纤Sagnac环形镜的全光开关

设计了一种新颖的、低开关功率的全光开关. 将高非线性光子晶体光纤和双向抽运掺饵光纤放大器引入Sagnac环形镜内，破坏了环形镜的对称性，利用交叉相位调制作用使反向传输的两路信号光产生非线性相移，从而实现开关效应. 理论分析表明：开关功率与放大器的增益倍数和光子晶体光纤非线性系数的积成反比，在实验中所得开关功率约40 mW，消光比约为15.9 dB，并且信号光透过率随脉冲控制光峰值功率呈余弦变化，实验结果与理论分析相吻合. 关键词： 全光开关 高非线性光子晶体光纤 环形镜 交叉相位调制     

Design and simulation of an all-optical photonic crystal AND gate using nonlinear Kerr effect

A photonic crystal optical limiter with a sharp input-output characteristic curve is initially designed in this paper. Thereafter; using an optimized Y-junction, a new topology for an all-optical photonic crystal AND gate is proposed. The mentioned gate has a transition time less than 1?ps, a delay time less than 0.4?ps and occupies an area less than 100?μm². The 1,550?nm input lasers should have a power equal to 10W to be able to trigger the switching mechanism. The photonic crystal used for this purpose is a two dimensional triangular lattice of holes in a GaAs substrate. PWE and FDTD methods are used to simulate the proposed structure. Time domain simulations confirm the switching mechanism of the proposed AND gate.     

Ultrahigh-contrast and wideband nanoscale photonic crystal all-optical diode

We experimentally realize a nanoscale all-optical diode in a photonic crystal heterostructure with broken spatial inversion symmetry, performing independent of optical nonlinearity. The physical mechanism lies in unique dispersion relations of the photonic crystal and the transition of incident light between different electromagnetic Bloch modes. An ultrahigh transmission contrast of 10(3) order, a large operating bandwidth of over 50 nm, and an ultralow photon intensity of less than 10 kW/cm(2) are reached simultaneously.     

Kerr nonlinear switch based on ultra-compact photonic crystal directional coupler

In this paper, an all optical switch based on nonlinear photonic crystal directional coupler has been simulated and analyzed by the finite difference time domain (FDTD) method. The lunched pump signal increases the refractive indices of the central row of the coupler, due to nonlinear Kerr effect, hence the coupler works in the nonlinear conditions and lightwave guides to the other output port. We have tried to increase the coupling efficiency and reduce the required power in the nonlinear status by optimizing the bends structure and increasing the interaction between dielectric and lightwave signal. Therefore, the input signal beam can be controlled to be exchanged between two output ports to earn the highest output power ratio and the smallest amount of power required for nonlinear performance, the physical length of the coupler is determined to be 20a, where a is the structure lattice constant.     

Electro-tunable one-dimensional photonic crystal structures based on grooved silicon infiltrated with liquid crystal

The paper reports on composite periodic structures fabricated by means of wet anisotropic etching of (1 1 0)-oriented Si on a SOI platform and infiltrated with liquid crystal E7. The electro-optical effect under low voltages was registered for inter-digital structures by both optical microscopy and micro-Raman spectroscopy.     

Two bit all-optical analog-to-digital converter based on nonlinear Kerr effect in 2D photonic crystals

We have demonstrated the performance of a novel design for a single wavelength 2-bit all-optical analog-to-digital converter (ADC). This converter consists of two high efficient channel drop filters with a coupled cavity-based wavelength selective reflector in a 2D photonic crystal with total length of 15.87 μm. The A/D conversion is achieved by using nonlinear Kerr effect in the cavities. The output ports switch to state ‘1’ at different input power levels to generate unique states preferred for an ADC. This conversion is simulated by the finite difference time domain (FDTD) method for 5 different power levels. The proposed structure can function as a two-bit ADC with a 60 mW/μm input pulse and its maximum sampling rate is found to be ~ 45 GS/s.     

T-shaped polarization beam splitter based on two-dimensional photonic crystal waveguide structures

A T-shaped polarization beam splitter based on two-dimensional photonic crystal is proposed, which is composed of three waveguides: one input and two output. Unpolarized beams incident from the input port will be separated into two different polarization modes and outputted individually by two different coupling structures. Simulation results can be obtained by the finite-difference time-domain (FDTD) method. In the normalized frequency range of 0.3456 < \(\omega \alpha /2\pi {}c\) < 0.37, multiple frequencies can obtain high transmission efficiency simultaneously for both TE and TM modes. And the degree of polarization is very closed to 1 for both output ports at this frequency range. When the normalized frequency \(f=0.3534 \omega \alpha /2\pi {}c\), the transmission efficiency, respectively, is 88 % and \(91\) % for TE modes and TM modes. The extinction ratio is all 30dB for both modes. The polarization beam splitter attains the requirement we expected by analyzing simulation results.     

Fabrication of three-dimensional photonic crystal structures containing an active nonlinear optical chromophore

Direct laser writing by two-photon polymerization of photosensitive materials has emerged as a very promising technique for rapid and flexible fabrication of photonic crystals. In this work, a photosensitive silica sol-gel containing the nonlinear optical chromophore Disperse Red 1 is synthesized, and the two-photon polymerization technique is employed to fabricate three-dimensional photonic crystals with stop-gaps in the near-infrared. The composite material exhibits minimal shrinkage during photopolymerization, eliminating the need for shrinkage compensation or the fabrication of support structures.