带有光子晶体波导的微型随机激光器研究

文中采用有限时域差分(FDTD)法研究了ZnO随机介质与光子晶体波导相结合的微型激光器的辐射特性和频谱特性,用平面波展开法分析了光子晶体能带特性。数值研究结果表明:由于光与随机介质相互作用,使得光在该微型激光器中放大,损耗减小,存在较长滞留时间,同时随机介质局域光的能力变强,激光的阈值降低,而且含四方格子结构光子晶体的激光器具有良好的激光特性和调制作用。该新型器件的设计与研究将为研制可嵌入集成光子芯片的、低阈值的微型激光器提供理论基础。     

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。     

光子晶体波导传输特性研究

在完整二维光子晶体中引入线缺陷后,就形成了二维光子晶体波导。将时域有限差分方法(FDTD)用于光子晶体波导传输特性研究,计算了光子晶体波导的透射率频率分布,给出不同结构的光子晶体波导的光场分布及能流密度示意图。     

二维三角晶格介质柱光子晶体线缺陷波导慢光研究

以二维三角晶格介质柱光子晶体线缺陷波导为研究对象,通过平面波展开(PWE)法对光在波导中传输时的慢光特性进行了仿真分析,发现光子晶体的填充因子以及线缺陷中的柱子半径大小决定了慢光导模在光子带隙中的传输特性.随着填充因子的增大,光子晶体波导的导模群速度迅速减小.缺陷柱的半径大小对导模群速度的影响要强于填充比.通过调整填充因子和缺陷柱半径,得到了导模群速度小于0.01c的波导结构.结合慢光导模的群速度色散(GVD)特性分析,发现极慢光区域的GVD值位于105～106量级,能够保证光的高效传输.     

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...     

光子晶体技术--(二)光子晶体光波导

简介了二维(2-D)光子晶体结构和通过在光子晶体中引入线缺陷形成的光子晶体光波导。重点介绍直波导、弯波导、Y分支光波导和光子晶体光波导与光纤的耦合。     

GeSbSe光子晶体波导结构设计及传输特性研究

利用平面波展开法计算Ge Sb Se基质光子晶体带隙,研究光子晶体波导中带隙与空气孔(或介质柱)半径的变化关系,并结合光子晶体波导的工作波长,设计出周期为500 nm,半径为150 nm的三角晶格空气孔型Ge Sb Se光子晶体波导。采用时域有限差分法模拟所设计的直线型光子晶体波导和60°弯曲光子晶体波导的传输特性,模拟结果显示在传统结构光子晶体波导中,直线型光子晶体波导具有很高的光学传输效率,但在60°弯曲型波导中的传输效率较低,分析原因为光子晶体波导直线区域与弯曲区域光的传播模式不同。因此对60°弯曲型Ge Sb Se光子晶体波导进行了结构优化,优化后的光子晶体波导可以在较宽的波长范围内具有很高的传输效率。     

不同介电常数材料光子晶体慢光特性研究

在研究光子晶体慢光波导中,能带结构和色散特性是两个最重要的问题.采用平面波展开法及相关的数学理论推导,研究不同的介电常数材料对光子晶体线缺陷波导中慢光传播性质的影响,对二维线缺陷光子晶体慢光特性进行模拟和计算.仿真结果显示:随着材料介电常数的增大,慢光波导的相对禁带宽度增加,缺陷模式导光频率降低,群速度减小.因此,选择...     

光子晶体线缺陷波导中的慢光研究

研究了线缺陷光子晶体波导中的慢光现象。运用平面波展开法对线缺陷光子晶体波导结构进行了模拟计算,分析了填充因子作为敏感结构参量,其变化对色散性质和群速度的影响。发现光子晶体的填充因子决定了光子晶体带隙中导模的传输特性。随着填充因子的增加,光子晶体波导中的群速度先增大再减小。可以证明,通过改变光子晶体的填充因子,群速度可以达到0.01c以下。     

基于方形孔线缺陷的新型光子晶体零色散慢光结构研究

为了获得最优化的光子晶体零色散慢光结构,在传统的光子晶体线缺陷波导结构的基础上,进一步在线缺陷上下两侧各引入了两排方形空气孔,并进一步优化了这两排方形孔的结构参数。通过平面波展开法(PWE)与时域有限差分法(FDTD)进行数值分析表明,这种新型结构的光子晶体波导能够在中心波长1550 nm处实现带宽为8.34 nm、平均群折射率为61、群速度色散(GVD)为104量级的理想宽带慢光。     

Light propagation characteristics of straight single-line-defectwaveguides in photonic crystal slabs fabricated into asilicon-on-insulator substrate

Straight single-line defect optical waveguides in photonic crystal slabs are designed by the finite difference time-domain method and fabricated into a silicon-on-insulator (SOI) wafer. By employing an airbridge structure, clear light propagation for both polarizations is observed without any leakage along the waveguide. This experimental result is well explained by photonic bands of pure guided modes. Minimum propagation loss is estimated to be 11 dB/mm. This value is lower than that reported so far for three-line-defect waveguides with an SOI slab structure and almost comparable to that for an index confinement waveguide with a rectangular Si core. This propagation loss is dominated by the scattering loss by some irregularities. However, photonic crystal waveguides have the possibility of an essential lower scattering loss than in the index confinement waveguide because of the inhibition of radiation modes by the photonic bandgap     

AlGaAs-based two-dimensional photonic crystal slab with defectwaveguides for planar lightwave circuit applications

An AlGaAs-based near-infrared 2-D photonic crystal (PC) with an air-bridge structure featuring defect waveguides has been developed. For the sample without defect waveguides, measurements of the optical transmission characteristics in the wavelength range from 850 nm to 1100 nm showed a deep attenuation due to a bandgap with 30-35 dB attenuation and transmittance of nearly 100% for the guided modes. Optical propagation properties of defect waveguides were obtained by two methods: measurements of transmission spectra and plan-view observations of the optical beam trace along the waveguide with an infrared-vidicon camera. 3-D finite-difference time-domain simulations for the band structure and transmission spectra in the air-bridge slab with and without defect waveguides have revealed the appearance of four defect propagation modes specific to the defect waveguide, between two slab modes for the defect-free photonic crystal slab. These defect modes were experimentally identified in the measured transmission spectra     

Coupling between photonic crystal waveguides

A calculation procedure for evaluation of the coupling length of two parallel coupled channel waveguides in a planar photonic crystal is proposed. The first step of the calculation is evaluation of the band structure of a photonic crystal containing two coupled linear defects. The eigenvalue corresponding to eigenstates localized in the linear defect (the waveguide) is split due to the coupling. This splitting is treated within the coupled-mode theory that yields a simple relation between the splitting and the coupling length. The MIT photonic bands code is used to evaluate the coupling between channel waveguides in silicon./sup 1/ These calculations show that in contrast to the finite-difference time-domain approach, the method is effective for three-dimensional light propagation.     

Evaluation of self-collimated beams in photonic crystals for optical interconnect

Self-collimated beams and photonic bandgap mirrors in photonic crystals are evaluated for applicability in an on-chip interconnect system. Simulations using the plane-wave expansion and finite-difference time-domain methods are utilized to design and evaluate the theoretical performance of these systems, called a virtual waveguide due to borderless confinement of the signal. The effect of systematic and random fabrication errors on the performance is characterized. Coupling efficiency is virtually unaffected by misalignment, but is found to be a strong function of the length of the waveguide and the frequency of light. Additional routing capabilities of sharp 90/spl deg/ turns and signal crossings with no crosstalk are demonstrated. Photonic crystal virtual waveguides are ideal structures for on-chip optical signal routing.     

利用光子晶体波导定向耦合差频产生毫米波

文章利用耦合波理论研究了光子晶体两平行直波导的定向耦合差频特性,得出以频率相近的两单频波入射两波导输入端口时,波导中的光场分布的解析表达式,并采用时域有限差分法计算了耦合波导中的模场分布.计算结果表明:通过波导的耦合作用可以在两平行波导中检测到入射波的差频包络,其时域特性与理论分析相符.提出了利用光子晶体定向耦合波导实现光波-毫米波的转换.     

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。     

Design and fabrication of silicon photonic crystal optical waveguides

We have designed and fabricated waveguides that incorporate two-dimensional (2-D) photonic crystal geometry for lateral confinement of light, and total internal reflection for vertical confinement. Both square and triangular photonic crystal lattices were analyzed. A three-dimensional (3-D) finite-difference time-domain (FDTD) analysis was used to find design parameters of the photonic crystal and to calculate dispersion relations for the guided modes in the waveguide structure. We have developed a new fabrication technique to define these waveguides into silicon-on-insulator material. The waveguides are suspended in air in order to improve confinement in the vertical direction and symmetry properties of the structure. High-resolution fabrication allowed us to include different types of bends and optical cavities within the waveguides.     

Photonic Crystal Slab Waveguides Based on Antiresonant Reflecting Optical Waveguide Structures

A novel two-dimensional photonic crystal slab waveguide based on an antiresonant reflecting optical waveguide (ARROW) structure is proposed and designed. Lightwaves propagating in this waveguide are confined by antiresonance reflection vertically and the photonic band gap laterally. In order to obtain the characteristics of the ARROW-based photonic crystal waveguides, the three-dimensional finite-difference time-domain simulations are performed. With a lateral adiabatic taper, a coupling efficiency of 80.3% from a single-mode fiber to the ARROW-based photonic crystal waveguide of a single-line defect is obtained. In addition, propagation losses less than 10 dB/mm and bend losses of 0.23 and 0.39 dB/bend for the designed 60$^{circ}$ and 120$^{circ}$ bends are achieved at an operating wavelength of $1.55~mu{hbox {m}}$.      

Theoretical Study of Directional Emission Enhancement From Photonic Crystal Waveguides With Tapered Exits

We utilize an approach based on the idea of tapering waveguide exits to increase the directional emission of the light waves emitted from photonic crystal waveguides. It is shown that the enhancement of the directional beaming can be achieved under certain tapered configurations due to the interference pattern created at the exit of the waveguide. The output radiation profile is observed with the finite-difference time-domain method and a 75% reduction in the divergence angle of the out-coupled beam is achieved with the modified waveguide ends.