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...     

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.     

Dynamic wavelength tuning of channel-drop device in two-dimensional photonic crystal slab

Dynamic and external tuning of the operating wavelength of a channel add/drop device based on a two-dimensional photonic crystal slab is demonstrated. Thermo-optical effect, where the temperature increase is induced by the absorption of external light, is utilised for the tuning. The tuning speed is shown to be as fast as 20 /spl mu/s.     

二维光子晶体窄带滤波器研究

由于光子晶体存在带隙,只要在完整的二维光子晶体中引入线缺陷,那么原来处于禁带处特定波长的光也能沿着形成的波导传播,从而该光子晶体就具备了滤波的功能,再在线型波导的一侧设计个点缺陷,利用时域有限差分法分析发现,在缺陷处耦合出来的光不仅仅光强增大了,而且半高宽也变小了,这就与窄带滤波器的功能十分吻合。此外,只要根据光子晶体的晶格常数和椭圆介质柱的半径与窄带滤波器的中心波长关系,通过调整光子晶体的晶格常数和介质柱的半径,就可以改变窄带滤波器的中心波长。     

Experimental verification of numerically optimized photonic crystal injector, Y-splitter, and bend

We present the experimental measurement of a photonic crystal (PhC) device comprising an injector, Y-splitter, and 60/spl deg/ bend. The complete device consists of a 9-/spl mu/m-long injector tapering down from 5 /spl mu/m into a triangular-lattice-of-holes single-line defect waveguide with period a=430 nm and 36.2% air filling factor (corresponding to a radius over period (r/a) ratio of 0.30), an optimized Y-junction, 60/spl deg/ bend and output injectors, with a total device footprint of 30 /spl mu/m. This is etched into a GaAs/AlGaAs heterostructure using chlorine/argon chemically assisted ion beam etching (CAIBE). An erbium-doped fiber amplifier (EDFA)-based source and Fabry-Perot technique are used to characterize the device. The device displays a bandwidth of approximately 110 nm in the 1.55 /spl mu/m window, and a transmission of 70% relative to the same length of 5-/spl mu/m-wide waveguide. This is compared with three-dimensional finite-difference time-domain (3-D FDTD) results, which have a bandwidth and transmission of 120 nm and 75%, respectively. The highlight of this paper is the close agreement of the numerically optimized complete microcircuit with its experimental equivalent, and the significant improvement in bandwidth over previous work on Y-junctions.     

High-efficiency broad-band transmission through a double-60/spl deg/ bend in a planar photonic Crystal single-line defect waveguide

We present two designs to improve the transmission of a conventional double-60/spl deg/ bend in a single-line defect planar photonic crystal waveguide by locally optimizing the shape and the size of air holes of a photonic crystal lattice at the corners. We fabricate these devices on a silicon-on-insulator substrate and characterized them using tunable laser sources over a wavelength range from /spl lambda/=1.259 /spl mu/m to /spl lambda/=1.641 /spl mu/m. As we show, over a 9% bandwidth, less than 1-dB loss/bend was observed. In order to theoretically validate these experimental results, the three-dimensional finite-difference time-domain simulations are performed and found to agree with the experimental results.     

Nanofabrication of 1-D photonic bandgap structures along a photonic wire

A strongly-guided one-dimensional (1-D) waveguide called a photonic wire has high spontaneous emission coupling efficiency, enabling one to realize low-threshold lasers. Combined with the use of 1-D photonic bandgap structures consisting of arrays of holes etched within the photonic wire, novel microcavity lasers can be realized. We report the nanofabrication of a photonic bandgap structure for 1.5 /spl mu/m wavelength along a InGaAsP photonic wire, and discuss numerical simulations for its electrodynamics.     

基于二维光子晶体的多频段太赫兹波滤波器研究

基于二维光子晶体,提出一种多频段 太赫兹(THz)波滤波器。在光子晶体中引入3条平行的横向波导,通过改变介质柱的半 径或插入半径较小的介质柱在 相邻波导之间构成耦合区域,使特定频率的THz波从中部波导耦合至上、下侧光子晶体波 导并分别从端口2和1输出, 其余的THz波经中部波导从端口3输出,最终达到多频段滤波的效果。利用时域有限差 分法和平面波展开法对所提出 的器件计算和仿真结果显示,频率为f=3.24和3.75THz的THz波分 别从端口1、2和3输出中,传输效率分 别达到95%和99% ,表明本文结构能很好实现多频段滤波效果。     

光子晶体波导与微腔耦合的三通道波分复用器

为了实现对光波有效的选择输出,并且使光波的带宽很小,设计了微腔耦合的三通道波分复用器。对该器件采用时域有限差分法和微腔与波导间耦合模进行研究。首先,根据微腔选择不同频率的光波,设计光子晶体滤波器模型。然后,基于光子晶体耦合模理论,由定向耦合波导和一个高品质因子微腔构成的波分复用器。最后,为了提高输出光的透射效率,在波分复用结构的主波导的输出端,增加五个介质柱,形成一个反射层。实验结果表明:此结构能够通过微腔选择不同频率的光波,经过优化设计后的波分复用模型,光波的透射率得到了提高,波长λ=1.763μm的光波达到透射率将近90%。在光子晶体中取多个微腔可以选择输出更多波长的光波,所以这种结构在光子晶体集成器件的制作上有很好的应用前景。     

八通道光子晶体滤波器的设计与仿真

设计了一种具有高隔离度的八通道光子晶体滤波器,并应用时域有限差分法分析计算了在晶格常数相同的条件下,点缺陷微腔局域频率与光子晶体介质柱半径之间的变化规律。在此基础上,对该八通道滤波器的传输特性进行了仿真。结果表明,晶格常数取540nm时,该滤波器各信道的中心频率在1 510～1 580nm,信道间隔小于9.5nm,信道间隔离度均大于35dB。     

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.     

Tunable photonic crystal coupled-cavity laser

We report the development of a tunable photonic crystal coupled-cavity laser diode based on InP. The laser consists of two photonic crystal channel waveguides that are coupled through a photonic crystal mirror segment in /spl Gamma/-M direction. The cavity lengths define the respective mode spacings in the cavities. The tuning characteristics of the device are compared with results obtained from a transfer matrix model. Quasi-continuous tuning is achieved in a 29.6-nm window with 36 wavelength division multiplexing channels spaced 0.8 nm apart (ITU grid). The simplicity of fabrication and promising output characteristics should make this tunable laser design an interesting source for monolithic integration into highly integrated photonic circuits.     

光子晶体齿状波导的滤波特性研究

为了设计基于光子晶体波导的高性能滤波器件,在2维正方格子光子晶体波导结构中引入一系列齿状缺陷,采用有限元法对齿状光子晶体波导的传输特性进行了数值仿真和理论分析。结果表明,对于单个齿状缺陷,缺陷产生的共振频率使得在光子晶体波导通频域带出现带隙结构,可以实现良好的窄带滤波,并且通过改变齿状缺陷深度可以有效地控制缺陷的共振频率;引入多个齿状缺陷,缺陷之间会经过耦合作用形成一系列缺陷态,使得在光子晶体波导导通频域中出现宽带的带隙结构,可以实现宽带滤波。该光子晶体波导滤波器对窄/宽带滤波可根据波导结构中引入的齿状缺陷进行简单灵活调节。此研究在设计基于光子晶体波导的光子滤波器件方面具有潜在的应用价值。     

High efficiency coupling technique for planar photonic crystalwaveguides

A high efficiency coupling technique for photonic crystal waveguides is proposed. The technique is based on setting a single defect within a tapered photonic crystal waveguide. Simulation results show that the optimised scheme maximises the power transmission up to 87.5% at a wavelength of λ = 1.55 μm for a 0.5 μm-long photonic crystal taper     

Tunable Optical Notch Filter Realized by Shifting the Photonic Bandgap in a Silicon Photonic Crystal Line-Defect Waveguide

A tunable optical notch filter was realized by thermally shifting the TM-like (the light's electric field perpendicular to the substrate) bandgap of a silicon photonic crystal slab W1 line-defect waveguide with silica cladding. This device is compact-its footprint is 340times16 mum², excluding the electrode pads. The 3-dB bandwidth of the device was about 5 nm, and the extinction ratio at the center wavelength was as high as 40 dB. A maximum center wavelength shift of 17.9 nm was attained at a heating power of 0.7W, with a tuning efficiency of 25.5 nm/W. The tuning response time was less than 100 mus     

Photonic crystal channel drop filters based on circular-shaped cavities

This paper presents a novel photonic crystal-based channel drop filter in a silicon-on-insulator platform. The proposed structure consists of two line-defect waveguides and a special circular cavity between them. The effects of structural parameters and fabrication errors on resonant wavelength and drop efficiency of output signal are analyzed. Band structure calculations and propagation of electromagnetic field through device are done by plane wave expansion and finite-difference time-domain methods, respectively. In our design, drop efficiency of more than 81% and quality factor of about 2246 are achievable. Simulation results show the effectiveness of the proposed filter for narrowband applications in photonic communication systems.     

Room temperature photonic crystal defect lasers at near-infraredwavelengths in InGaAsP

Room temperature lasing from optically pumped single defects in a two-dimensional (2-D) photonic bandgap (PBG) crystal is demonstrated. The high-Q optical microcavities are formed by etching a triangular array of air holes into a half-wavelength thick multiquantum-well waveguide. Defects in the 2-D photonic crystal are used to support highly localized optical modes with volumes ranging from 2 to 3 (λ/2n)³. Lithographic tuning of the air hole radius and the lattice spacing are used to match the cavity wavelength to the quantum-well gain peak, as well as to increase the cavity Q. The defect lasers were pumped with 10-30 ns pulses of 0.4-1% duty cycle. The threshold pump power was 1.5 mW (≈500 μW absorbed)     

异质结构光子晶体微腔实现多通道可调谐滤波

为解决WDM系统中多信道同时滤波问题,设计并研究了缺陷对一种异质结构光子晶体多通道滤波器的调制机制,结果表明:在光子晶体环形滤波通道中引入点缺陷形成复合缺陷,可克服光子晶体环形腔结构的多模特性,实现单通道内的单纵模滤波;对于各个通道,复合缺陷中点缺陷的折射率对输出端透射谐振波长具有调谐作用,且对各通道的可调谐滤波作用彼此独立,随着点缺陷折射率的增大,输出的谐振波长出现红移现象。所设计的异质结构结构光子晶体对WDM系统实现多信道滤波功能提供理论和设计参考。     

Experimental demonstration of high coupling efficiency between wide ridge waveguides and single-mode photonic Crystal waveguides

The experimental demonstration of a high efficiency coupling technique based on setting a single defect within a photonic crystal (PhC) taper is reported. The samples were fabricated on a Silicon-on-insulator substrate and a 3-/spl mu/m-wide ridge waveguide was used to couple the light into and out of a single-mode PhC waveguide. Transmission efficiencies higher than 70% for wavelengths at 1.55 /spl mu/m are demonstrated which sharply improves the transmission efficiency achieved with butt-coupling and conventional PhC tapers.     

Large dispersion in photonic crystal waveguide resonator

Group delay and chromatic dispersion of a Fabry-Perot resonator embedded in a photonic crystal waveguide have been directly measured at 1.55 /spl mu/m wavelength using the phase-shift technique. The photonic crystal waveguide resonator was fabricated in an InGaAsP/InP heterostructure and was designed to show a channel spacing of 100 GHz. Group velocity dispersion up to 250 ps/nm was observed.