高透射率慢光速的光子晶体耦合腔波导的研究

将二维三角晶格光子晶体波导和微腔结构结合,优化设计了一种二维三角晶格光子晶体共振耦合腔波导,运用时域有限差分法(FDTD)模拟共振耦合腔波导TE偏振光的透射谱,通过透射谱得到传输光的透射率和群速度。结果表明,合适参数的二维三角晶格共振耦合腔波导在波长1.551μm处的群速度为c/130、透射率为20.1%,在波长1.502μm处的群速度为c/50、透射率为29.2%。运用平面波展开法(PWE)计算的该波导的能带结构对慢光特性进行了分析。这种慢光特性的光子晶体波导将在光存储、光延迟及光子集成等方面有潜在的应用价值。     

波导基本结构对光子晶体耦合腔光波导慢光特性的影响

研究了二维光子晶体耦合腔波导的结构对慢光特性的影响,发现微腔间的距离n、填充因子r/a和缺陷柱的尺寸rd是影响光子晶体禁带中慢光导模传输特性的重要参数。随着缺陷微腔间距离的增加,导模群速度vg急剧减小;当填充因子和缺陷柱尺寸增加时,导模向低频方向移动,同时,导模群速度降低;填充因子和缺陷柱尺寸降到一定数值后,vg达到最小值,此后,当r和rd分别超出其特定值继续增大,导模群速度反而增大。取微腔之间介质柱个数为6,普通介质柱尺寸为r=0.22a,a为光子晶体晶格常数,缺陷柱尺寸为rd=0.12a,得到导模群速度最大值vgmax1.93×10-3c,带边处vg10-4c(c为光速)。这一结果显示,通过基本结构设计可以实现对光子晶体耦合腔光波导中慢光的有效控制,这将为基于光子晶体功能器件的设计和应用提供有效的支持。     

耦合腔光子晶体慢光波导结构

在单线缺陷结构中引入两个附加的相邻介质柱,构成一种新型的光子晶体耦合腔波导结构.通过平面波展开法对波导结构的的慢光特性进行了仿真分析,研究了平移线缺陷上下两侧介质柱,以及改变腔体的长度对器件色散特性和群速度的影响.结果表明:与平移缺陷上下两侧介质柱相比,通过改变腔体的长度,不仅可将光群速度低到0.03c(c为真空下的光速),而且器件的有效波长范围接近20nm.利用时域有限差分法得到波导结构的传输场分布图,研究波长的选取对入射激励光在光子晶体耦合腔波导中传输场的影响,发现结构参量优化后的光子晶体耦合腔波导仍然具有良好的传输特性.     

椭圆柱微腔光子晶体耦合腔波导的慢光特性研究

采用大介质柱和椭圆介质柱环绕微腔结构构成光子晶体耦合腔光波导(PC-CROW),在获得慢光的同时,其缓存特性也获得了提高。当普通介质柱半径为0.25a(a为光子晶体晶格常数),环绕微腔圆形大介质柱半径为0.35a时,得到小于2.37×10-4c(c为真空中的光速)的导模群速度,这比均匀介质柱微腔波导的最大群速度减小了一个数量级,存储容量也有所下降;考虑到缓存性能,为了进一步改善PC-CROW的慢光性能和缓存特性,将环绕微腔大介质柱椭圆化,在椭圆长轴为0.42a,短轴为0.20a时,获得导模群速度小于2.3053×10-4c,存储容量达到9.8214 bit,品质因子Q也达到了最大值3575.1。     

光子晶体耦合腔光波导慢光结构特性研究

研究了用于光缓存的光子晶体耦合腔光波导的结构对慢光传输特性的影响.详细讨论了微腔间距关于波导禁带、导模带宽、导模传输群速度的具体关系.计算发现,随着微腔之间距离的增加导模显著平坦化,群速度急剧减小.当相邻微腔之间距离为7个晶格常数时,获得了小于2×10~(-4)c的超小群速度.通过长度为13.23 μm的7×7超胞构成的光子晶体耦合腔光波导,产生的最大光延迟超过了400 ps,这比相同长度传统光波导产生光延迟大四个数量级.     

微腔旋转对耦合腔光波导群速度的影响

本文利用多重散射方法和时域有限差分方法,理论研究了微腔旋转对二维正方晶格光子晶体耦合腔光波导群速度的影响.研究结果表明,通过旋转微腔可以造成传播模的模式分裂,从而实现群速度的降低.当微腔旋转角度为45°时,传播模的群速度最小,两个传播模的群速度分别达到了0.0016倍和0.0009倍于真空光速,与微腔未旋转时相比降低了一个数量级.上述两种传播模群速度的差别是由传播模的空间对称性决定的. 关键词： 二维光子晶体 耦合腔光波导 群速度     

低群速度色散和低损耗的二维光子晶体慢光波导

利用平面波展开(PWE)法分析了慢光在由介质柱和空气背景构成的二维三角晶格光子晶体耦合微腔波导中的传播特性.数值模拟结果表明:随着缺陷腔之间距离的增大,导模的群速度减小很快;兼顾色散和损耗的影响,当相邻微腔间距两倍于晶格常数时,耦合微腔波导单位厚度(mm)透射比为47%,带宽为1.97 GHz,导模有效群折射率为22....     

金属嵌入对三角晶格耦合腔光波导群速度的影响

利用多重散射法和时域有限差分法理论,研究了二维三角晶格光子晶体耦合腔光波导的传输特性.理论模拟结果表明,在耦合腔光波导中嵌入半径很小的理想金属丝,能有效地减弱相邻点缺陷之间的耦合强度,实现了比真空中光速小三个数量级的群速度.     

金属嵌入对三角晶格耦合腔光波导群速度的影响

利用多重散射法和时域有限差分法理论,研究了二维三角晶格光子晶体耦合腔光波导的传输特性.理论模拟结果表明,在耦合腔光波导中嵌入半径很小的理想金属丝,能有效地减弱相邻点缺陷之间的耦合强度,实现了比真空中光速小三个数量级的群速度.     

光子晶体波导慢光特性研究

基于二维三角晶格空气孔光子晶体,通过在光子晶体单线缺陷波导两侧引入不同的耦合腔,设计了慢光特性较好的波导结构.利用平面波展开法计算波导的色散曲线,并分析慢光模式的群速度和群速度色散特性.耦合腔采用单缺陷腔时,适当调节波导宽度可以获得在零色散点群速度为0.0128c的慢光模式,对应在1.55 μm波长处的带宽为409 G...     

Silicon nano-membrane based photonic crystal microcavities for high sensitivity bio-sensing

We experimentally demonstrated photonic crystal microcavity based resonant sensors coupled to photonic crystal waveguides in silicon nano-membrane on insulator for chemical and bio-sensing. Linear L-type microcavities are considered. In contrast to cavities with small mode volumes, but low quality factors for bio-sensing, we showed increasing the length of the microcavity enhances the quality factor of the resonance by an order of magnitude and increases the resonance wavelength shift while retaining compact device characteristics. Q~26760 and sensitivity down to 15 ng/ml and ~110 pg/mm2 in bio-sensing was experimentally demonstrated on silicon-on-insulator devices.     

Giant third-harmonic in porous silicon photonic crystals and microcavities

A giant enhancement (no less than by 10³) of the optical third-harmonic generation in one-dimensional porous silicon microcavities and photonic crystals was observed experimentally. The enhancement is due to the resonant enhancement of the fundamental field in the cavity mode and the fulfillment of the phase matching condition at the photonic band gap edges of the photonic crystal and in the vicinity of the microcavity mode.     

Modeling and design of 2D photonic crystal based Y type dual band wavelength demultiplexer

In this paper, photonic bandgap (PBG) induced wave guiding application of photonic crystals is exploited to design Dual Band Wavelength Demultiplexer (DBWD) for separating two telecommunication wavelengths, 1.31 and 1.55 μm. Two designs that use silicon rods in air and embedded air holes in silicon are realized for this purpose. Plane wave expansion (PWE) method and two dimension Finite Difference Time Domain (FDTD) methods are used to design and analyze the DBWD in Y type photonic crystal structure. Numerical analysis indicates that these designs enable the separation of two wavelengths with very high optical power extinction ratios. Other filter parameters like transmittance and quality factor are also calculated to confirm superior performance of the proposed design of photonic crystal based DBWD.     

二维硅基平板光子晶体器件

硅材料在红外通讯波段具有低损耗和高折射率的特性,使得其成为集成光学领域中应用最广的材料之一.主要介绍了本课题组在二维硅基平板光子晶体中实现微纳尺度上光调控的研究进展,讨论了利用光子晶体的缺陷态实现各种集成光学器件,包括光子晶体波导、微腔和利用光子晶体波导和微腔形成的滤波器.还介绍了光子晶体中特殊的光折射现象,包括红外波...     

Chalcogenide glass photonic crystals

All-optical switching devices are based on a material possessing a nonlinear optical response, enabling light to control light, and are enjoying renewed interest. Photonic crystals are a promising platform for realizing compact all-optical switches operating at very low power and integrated on an optical integrated circuit. In this review, we show that by making photonic crystals from a highly nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the fabrication and testing of two-dimensional Ge₃₃As₁₂ Se₅₅ chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to post-tune the devices using the material photosensitivity. In one proposal we hope to introduce a double-heterostructure microcavity using the photosensitivity alone.     

Resonant behavior and selective switching of stop bands in three-dimensional photonic crystals with inhomogeneous components

We demonstrate that, in contrast with the well-studied photonic crystals consisting of two homogeneous components, photonic crystals comprised of inhomogeneous or multiple (three or more) components may bring new opportunities to photonics due to the discovered quasiperiodic resonant behavior of their (hkl) stop bands as a function of the reciprocal lattice vector. A resonant stop band cannot be switched off for any permittivity of structural components. Tuning the permittivity or structural parameters allows the selective on-off switching of nonresonant (hkl) stop bands. This independent manipulation of light at different Bragg wavelengths provides a new degree of freedom to design selective optical switches and waveguides. Transmission experiments performed on synthetic opals confirmed the theoretical predictions.     

基于光子晶体共振耦合的四波长波分复用/解复用器

谐振腔因其具有选频功能而在集成光学领域具有广泛的应用. 通过两个光子晶体环形腔、四个不同尺寸的光子晶体微腔及波导之间的耦合, 实现了1310 nm, 1550 nm, 1600 nm和1650 nm 四个波长的波分解复用．时域有限差分法模拟分析的结果表明, 仅仅通过调制输出波导边缘介质柱的半径, 即可使四个波长的输出效率均达到90%以上. 所设计的器件不但效率高, 而且尺寸小(约为12 μ m× 17 μ m), 在未来的光通信领域中具有潜在的应用价值.     

Spontaneous emission in coupled microcavity-waveguide structures at the band edge

We examine spontaneous emission and photon dynamics in a microcavity coupled to a coupled-resonator optical waveguide (CROW) in a photonic crystal. We present an efficient tight-binding approach to obtain the Green tensor in large, arbitrary systems of coupled microcavities. We use this approach to examine spontaneous emission when the microcavity is strongly coupled to the CROW at the band center and band edge. We confirm the validity of weak-coupling theories for microcavities resonant at band center and obtain strong peak splitting in the previously inaccessible case of band-edge coupled structures.     

Silicon-based two-dimensional photonic crystal waveguides

A review of the properties of silicon-based two-dimensional (2D) photonic crystals is given, essentially infinite 2D photonic crystals made from macroporous silicon and photonic crystal slabs based on silicon-on-insulator basis. We discuss the bulk photonic crystal properties with particular attention to the light cone and its impact on the band structure. The application for wave guiding is discussed for both material systems, and compared to classical waveguides based on index-guiding. Losses of resonant waveguide modes above the light line are discussed in detail.