光子晶体集成光电子器件

文章简要介绍了利用光子晶体实现微纳尺度上光调控的物理原理和工作机制,重点讨论了如何利用光子晶体的缺陷态实现微纳尺度的各种集成光电子器件,并结合文章作者所在研究组的研究工作经验,简单回顾了各种类型的集成光电子器件的工作原理、物理实现和光学特性.     

光子晶体集成光电子器件

文章简要介绍了利用光子晶体实现微纳尺度上光调控的物理原理和工作机制,重点讨论了如何利用光子晶体的缺陷态实现微纳尺度的各种集成光电子器件,并结合文章作者所在研究组的研究工作经验,简单回顾了各种类型的集成光电子器件的工作原理、物理实现和光学特性.     

Photonic crystal cavities and integrated optical devices

This paper gives a brief introduction to our recent works on photonic crystal (PhC) cavities and related integrated optical structures and devices. Theoretical background and numerical methods for simulation of PhC cavities are first presented. Based on the theoretical basis, two relevant quantities, the cavity mode volume and the quality factor are discussed. Then the methods of fabrication and characterization of silicon PhC slab cavities are introduced. Several types of PhC cavities are presented, such as the usual L3 missing-hole cavity, the new concept waveguide-like parallel-hetero cavity, and the low-index nanobeam cavity. The advantages and disadvantages of each type of cavity are discussed. This will help the readers to decide which type of PhC cavities to use in particular applications. Furthermore, several integrated optical devices based on PhC cavities, such as optical filters, channel-drop filters, optical switches, and optical logic gates are described in both the working principle and operation characteristics. These devices designed and realized in our group demonstrate the wide range of applications of PhC cavities and offer possible solutions to some integrated optical problems.     

Photonic crystal waveguide directional couplers as wavelength selective optical filters

Waveguide directional couplers, formed by two closely spaced linear defect waveguides in a two-dimensional photonic crystal of air holes in a semiconductor matrix, are numerically studied using plane wave expansion and finite difference time domain methods. The coupling lengths are on a wavelength scale and show a strong wavelength dependence, allowing for the design of compact wavelength selective optical filters. Applications as a channel interleaver for the 1.55 μm wavelength range and as a micrometer sized 1.31/1.55 μm wavelength demultiplexer are presented.     

Photonic crystal wires for optical parametric oscillators in isotropic media

We investigate four wave mixing in photonic crystal wire microresonators realized in an isotropic medium. One-dimensional optical parametric oscillators are numerically analyzed by solving Maxwells equations in all dimensions and including material dispersion as well as nonlinear polarization. PACS 42.65.Yj; 42.70.Qs; 42.82.Gw     

Photonic crystal cavity on optical fiber facet for refractive index sensing

Using a micromanipulation technique, a planar photonic crystal nanocavity made from a thin semiconductor membrane is released from the host semiconductor and attached to the end facet of a standard single-mode optical fiber. The cavity spectrum can be read out through the fiber by detecting the photoluminescence of embedded quantum dots. The modified fiber end serves as a fiber-optic refractive index sensor.     

Photonic crystal devices

We developed photochemically controlled photonic crystals which may be useful in novel recordable and erasable memories and/or display devices. These materials can operate in the UV, visible or near IR spectral regions. Information is recorded and erased by exciting the photonic crystal with ∼ 360 nm UV light or ∼ 480 nm visible light. The recorded information is read out by measuring the photonic crystal diffraction wavelength. The active element of the device is an azobenzene functionalized hydrogel which contains an embedded crystalline colloidal array. UV excitation forms cis-azobenzene while visible excitation forms trans-azobenzene. Larger dipole moment of the cis-form results in decrease of the free energy of mixing which causes the hydrogel to swell and to red-shift the photonic crystal diffraction with a 36 s time constant. We also observed fast ms and sub-ms transient dynamics associated with convection due to heating of the medium by UV excitation. Convective motion of the medium stretches the PCCA for about 6 μs within which the convection decays and the elastic restoring force of the PCCA brings back the stretched PCCA to its equilibrium state with 33 μs time constant. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

光半导体--光子晶体

概述了光子晶体的特性、发展历程、理论基础及其潜在应用等,特别介绍了光子晶体的制备方法.     

Photonic crystal fiber coupler

Fiber couplers made with photonic crystal fibers (PCF) are reported. Two types of PCF were fabricated by means of stacking a group of silica tubes around a silica rod and drawing them. The fiber couplers were made by use of the fused biconical tapered method. With a fiber that had five hexagonally stacked layers of air holes, a 33/67 coupling ratio was obtained, and with a one-layer four-hole fiber, a 48/52 coupling ratio was obtained. The fabrication processes and the characteristics of the PCFs and the PCF couplers are presented.     

Photonic crystal beam splitters

In this work, the beam splitter with two input ports and two output ports in two-dimensional photonic crystals is studied through the finite-difference time-domain method. The beam splitter consists of two orthogonally cross line defects. The diameter of the two diagonal air holes at the intersection of the two line defects was modified. The input light can be identically divided into the two output ports. The beam splitters can be applied in the photonic crystal Mach-Zehnder interferometers or photonic crystal optical switches.     

Photonic crystal optical switch using a new slow light waveguide and heterostructure Y-junctions

In this paper we propose a photonic crystal Mach-Zehnder interferometer (MZI) based on a new coupled-cavity waveguide, where its advantage over the previous type of photonic crystal coupled-cavity waveguide is discussed. A heterostructure Y-junction is comprised of square and hexagonal lattices of the new coupled-cavity waveguide. It is designed by applying the temporal coupled-mode theory and is optimized, where an overall throughput efficiency of more than 90% is achieved at the wavelength of 1.55 μm. The design of the Y-junction is performed using finite-difference time-domain method. The designed heterostructure Y-junction is used in the structure of a MZI, where its arms are approximately as short as 24 μm. Finally, the transient response of the proposed optical switch is investigated.     

Photonic crystal with epsilon negative and double negative materials as an optical sensor

Two ternary photonic crystals are proposed for sensing applications. The first one is composed of an air layer as an analyte sandwiched between two double negative material (DNM) layers whereas the second one consists of an air layer sandwiched between two epsilon negative material (ENM) layers. The transmission spectrum is studied for two different values of the refractive index of the analyte layer with ?n = 0.01. A specific peak in the transmission spectrum is observed and the wavelength at which the peak occurs is determined. The wavelength shift due to any change in the index of the analyte layer is also determined. The effect of varying the parameters of the DNM and ENM on the sensitivity of the sensor is discussed. It is found that the sensitivity of the structure ENM/air/ENM is much greater than that of the structure DNM/air/DNM and it is estimated as 26 times of the sensitivity of the latter structure.     

Photonic crystal surface mode microcavities

Our recent research on surface mode optical microcavities based on two-dimensional photonic crystals (PhCs) was reviewed in this paper. We presented the design, fabrication and characterization of high quality (Q) factor surface mode microcavities. Realizations of these PhCs were based on both amorphous silicon-on-insulator (SOI) structures and crystalline SOI structures.     

Photonic crystal boosted chemiluminescence reaction

With an optimized photonic crystal, the chemiluminescence intensity is enhanced by 44.9 times and the chemiluminescence emission light intensity decay rate is accelerated 3.2 times. The interaction between the chemiluminescence system and the photonic crystal is discussed. The results will exploit a new platform for the photonic crystal based chemiluminescence assay.     

光子晶体液体浓度传感器

为了有效地检测混合液体的浓度,运用平面波展开法与光子晶体禁带理论,研究了光子晶体禁带宽度和混合液体浓度的对应关系。以砷化镓(GaAs)为背景材料的三角格子空气孔二维光子晶体内分别填充不同浓度的水醋酸、水甲醇混合液体,讨论了混合液体浓度与介电常数对二维光子晶体禁带宽度的影响。模拟结果表明,在温度保持不变的情况下,浓度在0～0.60mol/kg之间变化时二维光子晶体TE模没出现光子晶体禁带而TM模出现的光子晶体禁带宽度随着混合液体浓度和介电常数的增大而逐渐变窄且向高频区域移动。这一结果为生物化学中混合液体浓度的检测方面提供很好的参考依据。     

Photonic crystal electro-optical switching cell

We investigated the physical mechanism of a photonic crystal (PhC) switching cell based on an optical directional coupler (ODC). This ODC is driven by a low power external electrical command signal, inserted in the central coupling region, which causes the changes in the refractive index.The switching process is based on the change of the bar state to the cross state owing to the external command signal. In our simulations we used the following methods: Plane Wave Expansion by MPB (MIT Photonic-Bands), Finite-Difference Time-Domain by MEEP (MIT Electromagnetic Equation Propagation), Finite Element by COMSOL Multiphysics and our own Binary Propagation Method.     

Photonic crystal slotted slab waveguides

We report on the fabrication of photonic crystal waveguides in SOI that comprise an air-slot in the centre. The slot serves to confine suitably polarised optical radiation (H-polarisation) and due to its small size, provides extremely high field intensity values out with the high index material. Adding the photonic crystal environment then provides full control over the dispersive properties of this waveguide. We demonstrate the successful operation of this structure experimentally and explain its key features.     

Photonic crystal waveguide sampled gratings

Photonic crystal waveguide sampled gratings (PCWSG) are proposed to realize multi-channel optical filter in a photonic crystal (PC) waveguide. The reflection characteristics of the filter are analyzed by using the coupled-mode theory (CMT) together with transfer-matrix method (TMM). It is shown that the reflection spectrum of the filter exhibits a group of reflection peaks, which are distributed with equal frequency spacing within the photonic crystal bandgap (PBG). The theoretically calculated results are numerically verified by using two-dimensional (2D) finite-difference time-domain (FDTD) method.