Two-dimensional photonic crystal ring resonator-based channel drop filter for CWDM application

In this paper, a channel drop filter based on two-dimensional photonic crystal ring resonator (PCRR) is proposed. The proposed structure consists of bus waveguide, dropping waveguide and a ring resonator. We have focused on improving the dropping efficiency and quality factor of the structure by applying different optimization techniques. Optimized channel drop filter using PCRR is designed, and it is extended to drop three different channels by changing the inner rods radius in each ring resonator that act as a demultiplexer. As designed structure drops three different channels such as 1524, 1544 and 1565 nm, the band gap for the structure is calculated and observed by plane-wave expansion method. The normalized transmission spectra and resonance wavelengths for different radius are obtained using two-dimensional finite-difference time-domain method. The proposed PCRR-based demultiplexer has the channel spacing of about 20 nm which fulfils the requirements of coarse wavelength-division multiplexing systems. The size of the demultiplexer is small; hence, it can be utilized for photonic integrated circuits.     

A new proposal for eight-channel optical demultiplexer based on photonic crystal resonant cavities

In this paper, we used the novel defective resonant cavities to design an eight-channel photonic crystal demultiplexer. We showed that by choosing appropriate values for the width of the resonant cavity, the desired wavelengths can be separated. The proposed platform has a square lattice of dielectric rods immersed in air. The value of transmission efficiency for channels was obtained in 94\(-\)99 % range. In addition, the maximum value of crosstalk and average quality factor for channels were calculated –11.2 dB and 2200, respectively.     

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.

     

Ultra-compact 1 × 8 Channel terahertz Wave Power Splitter

Relying on 1?×?2 photonic crystal waveguide and photonic crystal resonator, a compact eight-channel terahertz wave power splitter is proposed. The mechanism of such a device is further theoretically analyzed and numerically investigated with the aid of the plane wave expansion method and the finite-difference time-domain method. With an appropriate design, the proposed power splitter can split the input terahertz wave energy equally into eight output ports at the frequency of 0.667 THz. Furthermore, the total size of the present device is of 4.33 mm?×?3.74 mm. Due to its small size, the multi-channel terahertz wave power splitter has practical applications in the terahertz wave integrated circuit fields.     

新型光子晶体四通道滤波器研究与设计

基于光子晶体环形腔缺陷与线缺陷波导之间的共振耦合原理,设计了 一种由新型环形腔和主波导组成的四通道二维三角晶格光子晶体滤波器.运用平面波展开法和时域有限差分法分析了光波在整合结构中的传输特性,并进一步讨论环形滤波器内的内部介质柱半径大小对滤波器传输特性的影响.结果表明:新改进环形的滤波器传输效率达到80％左右.通过实验...     

A Rectangular SRR Switched Slotted Microstrip Patch for Frequency Diversity Application

Planar antenna with a specific resonant mode is essential to meet the diversity demand for wireless communication. This paper presents modeling and experimental validation of a microstrip antenna design in which multiple resonant frequencies are excited based on different negative permeability response of the rectangular split ring resonator (SRR). The antenna geometry consists of a slotted patch with split ring resonator loaded between its two arms. The patch was fabricated on FR-substrate of relative permittivity ε_r?=?4.4, and has a size of 30.5 mm?×?34 mm. In the antenna desing, PIN diodes connect the outer ring and inner ring resonator of the SRR to the adjacent arms of the patch. Under various bias conditions, quad-band resonance was observed at 2.07 GHz, 2.11 GHz, 2.31 GHz, and 2.46 GHz. The measured S₁₁ results are found comparable to the simulated data, and demonstrate proper functioning of the proposed antenna with stable gain and radiation patterns.     

Microwave Dielectric Properties of BiCu<Subscript>2</Subscript>PO<Subscript>6</Subscript> Ceramics with Low Sintering Temperature

A BiCu₂PO₆ microwave dielectric ceramic was prepared using a solid-state reaction method. As the sintering temperature increased from 800°C to 880°C, the bulk density of BiCu₂PO₆ ceramic increased from 6.299 g/cm³ to 6.366 g/cm³; the optimal temperature was 860°C. The best microwave dielectric properties [permittivity (? _r ) = ～16, a quality factor (Q × f) = ～39,110 GHz and a temperature coefficient of resonant frequency (τ _f ) = ～?59 ppm/°C] were obtained in the ceramic sintered at 860°C for 2 h. Then, TiO₂ with a positive τ _f (～+400 ppm/°C) was added to compensate the τ _f value. The composite material was found to have a near-zero τ _f (+2.7 ppm/°C) and desirable microwave properties (? _r  = 19.9, Q × f = 24,885 GHz) when synthesized at a sintering temperature of 880°C. This system could potentially be used for low-temperature co-fired ceramics technology applications.     

Plasmonics refractive index sensor based on tunable ultra-sharp Fano resonance

In this paper, a plasmonics refractive index sensor with the semiring-stub system coupled to a bus waveguide is proposed. The structure can achieve wavelength band tunable and ultra-sharp Fano resonance. The coupling mechanism between the bright mode and dark mode is investigated in detail, and apparent plasmon induced transparency (PIT) is realized on the resonance wavelength. The full width at half maximum (FWHM) of the resonant wavelength is modulated by adjusting the coupled distance. The sensitivity and figure of merit (FOM) of the proposed sensor can reach up to 600 nm/RIU and 120 on the visible region, respectively, and this performance can be helpful for designing the photonic integrated circuit and optical communication, in addition, it can be applied for bio-sensing.     

High sensitive photonic crystal ring resonator structure applicable for optical integrated circuits

Quality factor and refractive sensitivity are significant parameters in designing optical devices such as filters, demultiplexers, switches and sensors. In this paper, we proposed a novel structure for photonic crystal ring resonator with octagon-shaped core. The transmission efficiency of the proposed ring resonator at \(\lambda =1551\,\hbox {nm}\) is about 99.6 % with bandwidth and quality factor values equal to 0.3 nm and 5170. The proposed structure is very sensitive upon the variation of refractive index of total structure and core part of the resonator, such that the refractive index sensitivity to the refractive index of total structure and the resonant ring core is \(\Delta \lambda /\Delta \lambda =3.1\,\hbox {nm}\,/\,0.01\) and \(\Delta \lambda /\Delta \hbox {n}=2.9\,\hbox {nm}\,/\,0.01\), respectively.     

Trapezoid 2D photonic crystal nanoring resonator-based channel drop filter for WDM systems

In the present work, a nanostructure of trapezoid photonic crystal ring resonator-based channel drop filter is designed for wavelength division multiplexing systems (WDM) to drop a channel at a center peak wavelength of 1543 nm. The proposed channel drop filter is composed of bus waveguide, drop waveguide, trapezoid nanoring resonator and reflector in a two-dimensional (2D) hexagonal lattice with circular rods arranged in air host. The trapezoid nanoring resonator is playing a very important role in WDM systems for dropping a single channel over a wide wavelength range. The photonic band gaps of perfect lattice structure and non-perfect lattice structure are absolutely calculated by plane wave expansion method. The functional properties of the designed filter are evaluated by finite difference time domain method (FDTD). The functional properties are center peak wavelength, dropping efficiency, passband width and quality factor. The FDTD method results show dropping efficiency is 100%, and quality factor is about 514.33 which are highly suitable for WDM systems. Further, lattice constant, inner and outer rod radius and refractive index difference of the structure are varied to tune the filter center peak wavelength and its corresponding functional parameters effects are investigated. The proposed nanoring resonator-based optical filter is ultra-compact size around \(14\, \upmu \hbox {m} \times 8.4\, \upmu \hbox {m}\); hence, it is extremely suitable for WDM-based photonic communication systems and photonic integrated circuits.     

Ultra-fast all-optical encoder using photonic crystal-based ring resonators

Optical encoders are one of the important optical logic devices required in optical communications and optical signal processing. In this paper, we proposed a novel structure for designing an all-optical 4-to-2 optical encoder based on photonic crystals. For this purpose, four photonic crystal-based ring resonators were located between the input and output ports which results in improved coupling efficiencies between input and output waveguide and reduced cross-reflection between the input ports. The central wavelength of the photonic crystal-based ring resonators is 1555 nm. However, due to its wide bandwidth the proposed structure can be used for a wide range of optical waves. In the proposed structure, the delay time and the ON/OFF contrast ratio are 1.8 ps and 9.2 dB, respectively. The other advantages of the proposed structure is that we did not use nonlinear materials in designing the proposed structure, so there is no need for high amount of optical intensities.     

All-optical 6- and 8-channel demultiplexers based on photonic crystal multilayer ring resonators in Si/C rods

In this paper, we employed multilayer ring resonators in a silicon rod base structure to realize 6-channel and 8-channel demultiplexers based on two-dimensional photonic crystals. Both the main rings and basic structures are composed of silicon rods, and the interior rings of the multilayer rings are composed of carbon. Employing silicon and carbon rods of different radii in multilayer ring resonators enhanced the coupling efficiency between the rings and waveguides. The average quality factor and power transmission efficiency were 4320 and 93%, respectively. Crosstalk values from \(-11\) to ?46 dB in conjunction with the mentioned characteristics suggest the use of the device for optical communication applications. The compact size of the proposed structure and the materials used make the proposed demultiplexer suitable for optical integrated circuits.     

基于慢光效应的解波分复用器的设计与研究

为了设计一种基于正方晶格光子晶体波导的三端口解波分复用器,利用光子晶体的光子带隙特性和光在光子晶体慢光波导中的传输特性,并采用平面波展开法及时域有限差分法对解波分复用器的特性进行了理论分析,数值计算了解复用器的空间和光谱分布特性。结果表明,调整波导中与波导紧邻的第1排柱子的位置,使三部分波导中传输的慢光频率发生改变,通过合理的结构设计,利用慢光模式传输的特点将不同频率的光从不同的输出端输出,可实现解复用的目的。     

Demonstration of a High-Order Mode Input Coupler for a 220-GHz Confocal Gyrotron Traveling Wave Tube

A design of high-order mode input coupler for 220-GHz confocal gyrotron travelling wave tube is proposed, simulated, and demonstrated by experimental tests. This input coupler is designed to excite confocal TE ₀₆ mode from rectangle waveguide TE ₁₀ mode over a broadband frequency range. Simulation results predict that the optimized conversion loss is about 2.72 dB with a mode purity excess of 99%. Considering of the gyrotron interaction theory, an effective bandwidth of 5 GHz is obtained, in which the beam-wave coupling efficiency is higher than half of maximum. The field pattern under low power demonstrates that TE ₀₆ mode is successfully excited in confocal waveguide at 220 GHz. Cold test results from the vector network analyzer perform good agreements with simulation results. Both simulation and experimental results illustrate that the reflection at input port S11 is sensitive to the perpendicular separation of two mirrors. It provides an engineering possibility for estimating the assembly precision.     

Room-temperature light emission from an airbridge double-heterostructure microcavity of Er-doped Si photonic crystal

We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional (2D) hexagonal photonic crystal (PC) airbridge double-heterostructure microcavity with Er-doped silicon (Si) as light emitters on siliconon-insulator (SOI) wafer at room temperature. A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence (PL) spectrum with the pumping power of 12.5 mW. The obvious red shift and the degraded quality factor (Q-factor) of resonant peak appear with the pumping power increasing, and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 mW. The resonant peak is observed to shift depending on the structural parameters of PC, which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.     

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.     

A New Type of Miniature Ultra-Wideband Band-Pass Filter with Coplanar Waveguide Fed

A novel miniature ultra-wideband (UWB) bandpass filter with coplanar waveguide (CPW) fed is proposed. The size of the filter is reduced largely because of combining the wideband couple gap and parallel-coupled CPW line (not cascading multiple resonator), and the length of realized filter is only 0.42 λ _g0 (λ _g0 is the guiding wavelength at central frequency). The measured insertion loss is less than 2.0 dB, and the group delay variation is less than 0.2 ns within the UWB passband. Basic agreement between the simulated and measured results has been achieved.     

基于波状PN结的低驱动电压电光调制器

本文研究了一种基于波状PN结的低驱动电压电光调制器,该器件在光通信系统中可以获得较高的传输效率和较低的传输损耗。器件主要由光子晶体线缺陷波导和谐振腔组成。在光子晶体平板上下侧分别添加反向偏置电压,同时在波导中心区域引入谐振腔,通过在谐振腔区域添加不同浓度的掺杂,从而在线缺陷波导处形成波状PN结。根据等离子色散效应,在光子晶体两边施加反向偏置电压时会引起掺杂区硅基平板折射率的变化,从而导致光的透射率发生改变,以此达到调制的目的。采用时域有限差分法(FDTD)分析其时域稳态场强分布、模场分布和波状PN结参数对驱动电压的影响,结果表明:在驱动电压为1.04 V时,该器件可以实现中心波长为1 584.5 nm的TE模窄带宽通、断调制,且器件的消光比高达30.8 dB,插入损耗仅有0.5 dB,Q值高达1.4×10^4。     

Spectral and power efficiency investigation in single- and multi-line-rate optical wavelength division multiplexed (WDM) networks

In order to tackle the increasing heterogeneous global Internet traffic, mixed-line-rate (MLR) optical wavelength division multiplexed (WDM) networks have emerged as the cost- and power-efficient solution. In MLR WDM networks, channels are structured as sub-bands, each of which consists of wavelengths operating at a similar data rate. By reducing the (1) spacing within a sub-band, or (2) spacing between sub-bands operating at different data rates, spectral efficiency can be improved. However, owing to high physical layer impairment levels, decrease in sub-band spacing adversely affects transmission reach of the channels, which results in higher power consumption due to requirement of increased signal regeneration. In this work, we compare power efficiency of various MLR and single-line-rate (SLR) solutions, and also investigate the trade-off that exists between spectral and power efficiency in a WDM network. Simulation results indicate that (1) for high transmission capacities, a combination of 100 Gbps transponders and 40 Gbps regenerators will obtain the highest power efficiency; (2) for long connection distances, a point of merging occurs for various SLR and MLR designs, where power consumption is independent of the frequency band distribution; and (3) for MLR systems, both spectral and power efficiency can be improved by using either shorter links with higher bandwidth assignment to 100 Gbps wavelengths, or longer links with higher bandwidth assignment to 40 Gbps wavelengths. Finally, the results indicate that focusing on spectral efficiency alone results in extra power consumption, since high quality of transmission and spectral efficiency leads to increased regeneration.     

Green Synthesis of Ag-Cu Nanoalloys Using <Emphasis Type="Italic">Opuntia ficus</Emphasis>-<Emphasis Type="Italic">indica</Emphasis>

Bimetallic Ag/Cu nanoparticles have been obtained by green synthesis using Opuntia ficus-indica plant extract. Two synthesis methods were applied to obtain nanoparticles with core–shell and Janus morphologies by reversing the order of precursors. Transmission electronic microscopy revealed size of 10 nm and 20 nm for the core–shell and Janus nanoparticles, respectively. Other small particles with size of up to 2 nm were also observed. Absorption bands attributed to surface plasmon resonance were detected at 440 nm and 500 nm for the core–shell and Janus nanoparticles, respectively. Density functional theory predicted a breathing mode type (BMT) located at low wavenumber due to small, low-energy clusters of (AgCu) _n with n = 2 to 9, showing a certain correlation with the experimental one (at 220 cm^?1). The dependence of the BMT on the number of atoms constituting the cluster is also studied.