All optical half adder based on photonic crystal resonant cavities

In this paper, we are going to propose and design an all optical half adder based on photonic crystal structures. For realizing the proposed structure, we will use two nonlinear resonant cavities inside a two-dimensional photonic crystal structure. Nonlinear resonant cavities will be created by replacing the ordinary rods via defect rod made of nonlinear material such as doped glass. Plane-wave expansion and finite difference time domain methods will be used for simulating the proposed structure. For the proposed structure, the maximum delay time is about 3 ps.     

Ultra-fast all-optical full-adder based on nonlinear photonic crystal resonant cavities

In this paper, a new photonic crystal-based full-adder for the summation of three bits has been proposed. For realizing this device, three input waveguides are connected to the main waveguide. An optical power splitter is placed at the end of this waveguide. Concerning the amount of optical intensity inside this waveguide, two nonlinear resonant cavities transmit the waves toward the correct ports. When the cavities do not drop the optical waves, the splitter guides them toward the output ports. The maximum delay time of the presented structure is around 0.5 ps and shows the fastest response among the reported works. This improvement is obtained due to using the resonant cavities. The time analysis results in a maximum working frequency of 2 THz. Also, designing the structure in 93 µm² demonstrates that it is more compact than the previous works. The normalized low and high margins are obtained around 10% and 85%, respectively. So, the proposed device is capable of considering optical processing circuits.

     

Compact eight-channel wavelength demultiplexer using modified photonic crystal ring resonators for CWDM applications

An eight-channel wavelength demultiplexer by cascading of ring resonators (RRs) in photonic crystal (PhC) structure is proposed in this paper. In designing of this demultiplexer, we used eight square-shaped PhC RRs with different refractive index (RI) of defect rods to generate a distinctive resonance wavelength. Each PhC RR has a specific resonance wavelength with tuning a variety of design parameters such as RI of a whole, defect and inner rods and radius of defect rods. In operating wavelength of λ₀?=?1497 nm, the transmission power and quality factor (Q) of single RR are discovered as 96% and 1000, respectively. The average power transmission, channel spacing, crosstalk and full width at half maximum are found by finite difference time domain method to be about 96?±?1%, 2.25 nm, ??35 dB and 1.5 nm, respectively. Simulation outcomes demonstrate that the designed demultiplexer has a proper operation. The footprint of the designed device is about?~?115 μm², which makes this device a promising for future photonic integrated circuits.

     

Investigation on 2D photonic crystal-based eight-channel wavelength-division demultiplexer

In this paper, eight-channel wavelength-division demultiplexer (WDDM) is proposed and designed using two-dimensional photonic crystal (2DPC) ring resonator whose corresponding functional parameters such as transmission efficiency, resonant wavelength, Q factor are investigated. The proposed structure consists of bus waveguide, dropping waveguide and square ring resonators. Eight different channels are dropped by altering the cavity size and radius of the defect rods. The plane-wave expansion (PWE) and finite-difference time-domain (FDTD) methods are employed to analyse the photonic band gap (PBG) of periodic and non-periodic structure and to arrive normalized transmission spectra, respectively. The resonant wavelengths of eight-channel demultiplexers are 1496.9, 1502.3, 1506.9, 1512.3, 1515.0, 1520.4, 1525.3 and 1530.6 nm. The average transmission efficiency, Q factor and spectral width of proposed demultiplexer are 81%, 825 and 1.8 nm, respectively. The mean channel spacing is about 4.2 nm. The size of the demultiplexer is small; hence, it can be utilized for photonic integrated circuits (PIC).     

基于液体选择填充光子晶体光纤的波分解复用器研究

设计了一种基于液体选择填充三芯光子晶体光纤的1.31/1.55um波分解复用器。中间为缺失一个空气孔的普通二氧化硅纤芯,左右两纤芯填充了不同折射率的液体材料。根据光纤的消逝场耦合的模式理论,不对称相邻波导存在波长相关耦合。不同填充折射率的两纤芯与中间纤芯分别耦合,构成两个不同响应波长的光滤波器。通过选择合适光纤长度,可实现不同波长光的分离。采用全矢量有限元法分析了光纤的传输特性,讨论了填充不同折射率液体时波导间的模式耦合,得到了其匹配波长与耦合长度。基于光束传播法仿真发现,长度为4.88 mm的光纤能实现1.31/1.55 um波长光的解复用。     

具有谐振腔的弯折光子晶体波导特性研究

为了研究基于光子晶体波导的高性能滤波器,采用调节谐振腔结构和优化耦合结构等方法,基于耦合模理论,在正方格光子晶体中设计了3种光子晶体弯折波导,并进行了理论分析和仿真验证,利用时域有限差分法取得了3种波导在S波段及C波段上的工作特性数据。结果表明,3种波导在不同波段表现出良好的带阻或带通特性,且其结构截止传输波长和通带传输波长随整体介质柱相对介电常数增加向长波方向移动,介电常数ε_r每增加0.3,截止传输波长和通带传输波长均增加6nm左右。这一结果对微型光传感器、微型光通信器件、集成光路等方面的设计都是有帮助的。     

Modeling of two-dimensional photonic crystal resonant cavities incorporating elliptically shaped dielectric cylinders

Modeling of photonic crystal structures is an ongoing challenge. This letter is devoted to the theoretical modeling of photonic crystal resonant cavities, composed of elliptically shaped dielectric pillars. Through this rigorous study, we can examine the impact of the elliptical-shape deformations to important quantities related to the photonic crystal cavity performance, such as the quality factor and the resonance frequency.     

一种新型多模干涉型光子晶体波分解复用器

基于二维光子晶体中多模干涉效应（MMI）设计了一种新型的三波长波分解复用器,该结构能有效分离1310/1500/1550nm三个波段的波长。并且,当我们改变该波分解复用器的相关结构参数时,该结构能拓展至其他波段。除此之外,该结构也能单独作为两波长波分解复用器对1310/1550nm实现分离。通过计算,该波分解复用结构三个波长的透射率均在91%以上。与此同时,借助于平面波展开法及时域有限差分法,我们对光波在该结构的传播效率及传播行为进行了计算及模拟。     

5 GHz-spaced, eight-channel optical FDM transmission experimentusing guided-wave tunable demultiplexer

A 5 GHz-spaced, eight-channel optical FDM transmission experiment using a guided-wave tunable demultiplexer is presented. 400 Mbit/s intensity-modulated optical carriers are multiplexed and transmitted through 13 km single-mode fibre. One of the carriers is selected by the tunable demultiplexer and directly detected     

A three-dimensional optical photonic crystal

We report on the successful fabrication of a working three-dimensional (3D) crystal operating at optical wavelength λ. The minimum feature size of the 3D structure is 180 nm. The 3D crystal is free from defects over the entire 6-inch silicon wafer and has an absolute photonic bandgap (PBG) centered at λ~1.6 μm. Our data provides the first conclusive evidence for the existence of a complete 3D PBG in optical λ. This development will pave the way to tinier, cheaper, more effective waveguides, optical switches and lasers     

5 GHz-spaced, eight-channel, guided-wave tunable multi/demultiplexer for optical FDM transmission systems

A 5GHz-spaced, eight-channel, guided-wave tunable multi/demultiplexer for optical frequency-division-multiplexing (FDM) transmission systems is demonstrated. It is constructed with high-silica channel waveguides and thin-film heaters loaded on the waveguides for frequency tuning     

Ultra-high-Q optical filter based on photonic crystal ring resonator

In this study, a photonic crystal ring resonator with a triangular lattice is used to design an optical filter. The proposed structure is able to filter the central wavelength of 1548 nm with a transmission coefficient of over 95%. Moreover, this structure has an ultra-high-quality factor (Q) of about 1290. With altering the features of the structure including the refractive index, the lattice constant and the radius of the rods in the resonator core, their effects on the central wavelength of the filter, transmission coefficient, quality factor and bandwidth are investigated. The plane wave expansion and finite-difference time-domain methods are used to extract photonic band gap and investigate the photonic behavior of the proposed structure, respectively.     

A novel proposal for all-optical decoder based on photonic crystals

In this paper, a new structure for all-optical 2-to-4 decoder is proposed which consists of six nonlinear photonic crystal ring resonators. The lattice constant of the main structure is a = 600 nm, and the refractive index and radii of rods are 3.1 and 0.2a, respectively. Simulation results have proved correct operation states of the decoder and numerical analysis is done in order to additional evaluation. The maximum and minimum power levels for logic 0 and 1 are \(0.1P_{\mathrm{in}}\) and \(0.37P_{\mathrm{in}}\) where \(P_{\mathrm{in}}\) is input power. The maximum cross talk and insertion loss are calculated about ?38 and ?20 dB, respectively. Since the operation speed of the decoder is more than 160 GHz, it will be appropriate candidate for being employed in ultrahigh-speed optical communication systems.     

Coupled mode theory of optical resonant cavities

This paper presents a theory describing coupled optical resonant cavities by means of systems of time-dependent coupled equations for the field amplitudes of standing waves in each resonator. The coupling coefficients entering the theory are derived from first principles. To the author's knowledge, this theory is new. The coupling coefficients can approximately be related to the amplitude transmission coefficients of traveling waves passing between the two resonant cavities. This relationship is checked for an example. Finally, we show that the mode amplitudes of one cavity can be eliminated so that the field in the other cavity becomes coupled to samples of itself taken at earlier times. The coupled-cavity theory applies to cavities with loss or gain. It is here expressed in scalar approximation, but it can easily be extended to vector fields.     

Study of wavelength demultiplexer based on two-dimensional photonic crystals

A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain （FDTD） method and plane wave extension （PWE） method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.     

Study of wavelength demultiplexer based on two-dimen-sional photonic crystals

A wavelength demultiplexer based on two dimensional photonic crystal waveguides is proposed. By using the finite difference time domain (FDTD) method and plane wave extension (PWE) method, the transmission spectra and the distributions of mode field are obtained, and the wavelength demultiplexer has been synthesized. The characteristics of the device are obtained.     

Multimode optical demultiplexer for DWDM with liquid crystal enabled functionalities

We have developed a liquid-crystal-based multimode optical demultiplexer (DEMUX) with additional functionalities such as switching and power equalization. Demultiplexing 16-channel 100-GHz-spaced signals into a 62.5-/spl mu/m multimode-fiber array is demonstrated. The central wavelength of each channel is designed according to the International Telecommunication Union grid. Adjacent channel crosstalk is less than -30 dB. The average 1and 3-dB passbands of the DEMUX are 12.5 and 22.5 GHz, respectively. A maximum extinction ratio of 16.2 dB is achieved. Different channels can be switched with rise and fall times of /spl sim/10 and /spl sim/70 ms, respectively. The outputs of the channels are equalized to -65 dBm. The variation between different channels reduced from /spl sim/10 dB to less than 0.5 dB.     

基于光子晶体光纤的受激拉曼散射全光波长转换研究

基于光纤中前向瞬态受激拉曼散射效应分析理论,利用光子晶体的高非线性特性,对光子晶体光纤拉曼波长转换进行了数值分析,并建立了全光波长转换设计方案的理论模型,给出了设计原理框图及实现方法。用OptiSystem对四路探测光进行波长转换仿真,仿真结果表明:所设计的全光波长转换器同时对四路探测光实现波长转换,转换输出的信号光码型和输入泵浦信号光码型一致,并且所得到的眼图线迹清晰,眼睛张开度良好。论证了该设计方案可行。     

Higher order optical resonant filters based on coupled defect resonators in photonic crystals

In this paper, a general methodology for the design of higher order coupled resonator filters in photonic crystals (PCs) is presented. In the proposed approach, the coupling between resonators is treated as though it occurs through a waveguide with an arbitrary phase shift. The coupling through the waveguide is analyzed theoretically, based on the coupled-mode theory in time. The derived theoretical model suggests a way to extend an equivalent circuit approach, previously demonstrated with a certain value of a phase shift, to the higher order filter design with an arbitrary phase shift. The validity of the proposed approach is confirmed by the design of a third-order Chebyshev filter having a center frequency of 193.55 THz, a flat bandwidth of 50 GHz, and ripples of 0.3 dB in the passband. The characteristics of the designed filter are suitable for wavelength-division-multiplexed (WDM) optical communication systems with a 100-GHz channel spacing. The performance of the designed filter is numerically calculated using the two-dimensional (2-D) finite-difference time-domain (FDTD) method.