Multiple defect characterization in finite-size waveguiding photonic bandgap structures

A powerful and efficient model recently proposed by the authors based on the leaky mode propagation method is used to characterize photonic bandgap structures incorporating multiple defects, having arbitrary shape and geometrical parameter values. The importance of the defect-mode characterization in photonic bandgap materials is due to the intensive use of defects for light localization to design very promising optical devices. This paper provides a new, efficient method to model defects in waveguiding, finite-size photonic bandgap devices and analytical and closed-form expressions for the reflection and transmission coefficients and out-of-plane losses,which is very useful and easily implemented under any operating conditions. Moreover, the method has been applied to examine the capabilities of waveguiding photonic bandgap devices in dense wavelength division multiplexing filtering applications. Therefore, the design of two optical filters for such applications has been carried out and optimal design rules have been drawn using the new model.     

Tunable bandpass microwave filters based on defect commandable photonic bandgap waveguides

A new type of tunable filter based on a commandable defect in the bandgap of a periodic CPW structure is proposed. The defect level is tuned either mechanically by adding a covering slab over the device or electrically by polarising diodes located at the defect. The validity of this concept is experimentally demonstrated at 4 GHz. This kind of filter is well suited for applications in the 10 to 60 GHz frequency range.     

基于全固光子带隙光纤的传感器的特性研究

为了实现对基于全固光子带隙光纤（AS-PBF）的传感器的特性研究,采用了双锥型模式干涉仪的结构,使用熔接机在一根AS-PBF上间隔一段距离制作两个锥形光纤,制备出一种基于双锥型模式干涉的特种光纤传感器。与传统单模光纤或折射率传导的光子晶体不同,AS-PBF的纤芯有效折射率较低,而包层有效折射率较高。通过理论分析和实验验证,测量研究了这种光纤结构对温度和轴向应力的响应。实验结果表明,温度灵敏度和轴向应力灵敏度分别为~63pm/oC和~-1.74nm/ N。与长周期光栅、布拉格光栅相比,基于全固带隙光纤的双锥型模式干涉传感器具有制备简单、结构紧凑等优势,在光纤传感领域具有广泛的应用前景。     

Characteristics of a photonic crystal defect waveguide-coupled quantum-dot photodiode

We have investigated the characteristics of an In/sub 0.4/Ga/sub 0.6/As self-organized quantum-dot (QD) resonant-cavity photodiode. The QD epitaxy and the design of the two-dimensional photonic crystal cavity are tailored for 1.3-/spl mu/m wavelength operation. The input excitation to the photodiode is provided with an in-plane defect waveguide designed with the same photonic crystal. The measured spectral photocurrent characteristics reflect mode coupling between the waveguide and detector and the resonant cavity effect due to total internal reflection and photonic bandgap confinement. The photocurrent response is explained with a model involving the circulating fields in the cavity. The characteristics are also dependent of cavity size. Enhancement and narrowing (/spl sim/ 10 nm) of the photoresponse at /spl lambda//spl sim/1.3 /spl mu/m are observed. A spectral dip, of /spl sim/ 10-nm width, also observed at 1.3 /spl mu/m is possibly due to the anticrossing mechanism, uniquely present in photonic crystal waveguides.     

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.     

Properties of photonic bandgap in one-dimensional mutlicomponent photonic crystal

Photonic crystals have beenthe subject of researchformore than one decade since the year 1987 when E.Yablonovlitch[1]and S.John[2]first discovered them.Aphotonic crystal is a structure whose refractive indexismodulated periodically,and the resultant photo…     

Two-dimensional Kagome photonic bandgap waveguide

The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes is investigated with respect to the width of the 2D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out     

四方格子全固光子带隙光纤带隙特性研究

基于平面波展开法,对四方格子全固光子带隙光纤带隙随结构的变化特性进行了数值模拟,并与具有相同结构参数三角格子全固光子带隙光纤进行了比较,数值结果表明带隙的位置由高折射率棒的结构参数决定,而与高折射率棒的排列方式和棒之间的间距无关,这一结果与反谐振效应非常吻合。最后对理想和实际拉制出的四方格子的全固态光子带隙光纤的带隙进行了比较,得出了在设计光纤时,应利用较低的带隙的结论。     

Honeycomb photonic bandgap fiber with a modified core design

Air-silica honeycomb fiber with a modified core design is introduced. The core has a concentrated high-index region. Such core design helps defect core mode stay in the cladding's photonic bandgap for a longer wavelength range (>1000 nm) as compared to conventional design. We further point out the importance of our core design in reducing the number of defect modes supported by the fiber structure.     

Meander microstrip photonic bandgap filter using a Kaiser taperingwindow

Compact photonic bandgap structures in microstrip technology with reasonable physical sizes have recently been proposed as efficient frequency-band reflectors. Here, it is shown how the application of a Kaiser tapering window to the periodic pattern etched in the ground plane of the structure provides appreciable performance improvement, reducing both passband ripple and stopband attenuation and increasing bandwidth     

Block copolymers as photonic bandgap materials

Block copolymers self-assemble into one-, two-, and three-dimensional periodic equilibrium structures, which can exhibit photonic bandgaps. This paper outlines a methodology for producing photonic crystals at optical length scales from block copolymers. Techniques for enhancing the intrinsic dielectric contrast between the block copolymer domains, as well as increasing the characteristic microdomain distances, and controlling defects are presented. To demonstrate the applicability of this methodology, a self-assembled one-dimensional periodic structure has been fabricated that reflects visible light. The wealth of structures into which block copolymers can assemble and the multiple degrees of freedom that can be built into these materials on the molecular level offer a large parameter space for tailoring new types of photonic crystals at optical length scales     

新型复式矩形光子晶体完全带隙分析

文章提出一种复式矩形光子晶体结构,首先利用平面波展开法(PWM)计算这种光子晶体的能带结构,然后对结构参数值进行优化,得到较大的光子带隙.分析结果表明, 当采用单晶硅作为介质柱材料时,长方晶格的晶格常数比值为0.35～0.45,正方介质柱边长与长方晶格长轴比值为0.45～0.50,得到的完全带隙可达到0.50～0.58,完全带隙率达到近39%,这对于研制性能优良的光子晶体器件具有重要意义.     

光子带隙型光子晶体光纤温度传感特性分析

为了提高光子带隙型光子晶体光纤的温度灵敏度,提出了在纤芯环上并入高折射率液体圆柱的新结构,并利用全矢量有限元法对提出的结构进行了仿真,得到了温度对光纤有效折射率、纤芯能量和有效模面积等传输特性的影响。结果表明,随着温度的升高,光纤的有效折射率和有效模面积会减小,纤芯能量会增加,且零群速率色散点向短波长方向移动,尤其在短波长条件下光纤传输特性随温度变化趋势更加明显。该研究提高了光子带隙型光子晶体光纤传输特性的温度灵敏度,使其更加适合于温度传感方面的应用。     

光子带隙光纤准直器回波损耗研究

研究了一种光子带隙光纤准直器。为了降低回波对光源的干扰,通常光纤准直器的回波损耗不应低于60 dB。由于带隙光纤端面没有反射,因此满足这一条件的带隙光纤准直器GRIN透镜入射面的倾斜角与普通光纤准直器不同。从高斯光束通过光学系统的一般模型出发,利用矩阵光学和高斯光束耦合理论,推导了光线传输矩阵。结合实际应用中光纤及GRIN透镜的参数,仿真分析了尾纤与GRIN透镜之间的间距及GRIN透镜的参数对准直器回波损耗的影响。结果表明,镀有增透膜时,当光子带隙光纤准直器的GRIN透镜入射面倾角等于3时,回波损耗大于60 dB。研究结果对进行光子带隙光纤准直器的设计具有指导意义。     

Non-uniform distributions of photonic bandgap microstripline structures

With the advent of planar photonic bandgap (PBG) materials different topologies of PBG structures have been proposed to improve the bandpass and band rejection performances of microwave signals. Conventional circular patterned PBGs have constraints in the broadband performance due to the high ripple heights in S-parameters. In this paper, we suggest two novel configurations with non-uniform dimensions of circular patterned PBG to improve the stopband bandwidth and the ripples. The dimensions of the circles are varied proportionally to the Binomial and Shebyshev polynomial distributions. The S-parameter performances with respect to frequencies have been presented. It is seen that Shebyshev distribution produce excellent performances by suppressing ripples and generating sharp cut-offs.     

Channel drop filter using a single defect in a 2-D photonic crystal slab waveguide

This paper describes a theoretical and experimental analysis of the channel drop filter using a single defect formed near the two-dimensional (2-D) photonic crystal slab waveguide. First, we calculate the transmission spectrum of a 2-D photonic crystal waveguide and show that high transmittance for a wide wavelength range (/spl sim/60 nm) is obtained in the 1.55-/spl mu/m region. We also show that a defect state having a wavelength within the high transmission wavelength range can be formed in the photonic bandgap by introducing a single defect of appropriate radius. Next, we fabricate several devices and show that the emission wavelength from each defect can be tuned by changing the defect radius. The measured tuning characteristics coincide well with the calculated results. From the near-field pattern of the device, we estimate the emission efficiency of the present device at almost a few tens percent. We clarify the structural condition in order to obtain the maximum output efficiency and show that tuning of emission wavelength while maintaining high output efficiency is possible by selecting appropriate defect radius and position. Based on these results, we propose an ultrasmall channel drop filter for a wavelength-division-multiplex optical communication system.     

Research on highly nonlinear photonic bandgap fibers

Since thefirst photonic crystal fiber (PCF) wasfabri-cated by Knight J C and his colleagues[1]at 1996 ,thistype of fibers ,consisting of a central defect region sur-rounded by multiple air holes running alongits length,has been the subject of much interes…     

Dielectric waveguides in two-dimensional photonic bandgap materials

We investigate the performance and guiding properties of waveguides fabricated in a finite two-dimensional (2-D) photonic bandgap (PBG) structure. Confinement in the direction perpendicular to the plane of periodicity is achieved by fabricating the 2-D PBG structure in a high dielectric layer enclosed by two lower dielectric layers. Simulations using the finite-difference time-domain (FDTD) method are performed to investigate the energy transport in such waveguides. Good qualitative agreement is found with the experimental observations