Three-color photonic crystal demultiplexer based on ultralow-refractive-index metamaterial technology

We numerically demonstrate the operation of a novel class of wavelength-division demultiplexing circuit based on photonic crystal waveguides that are entirely synthesized by ultralow-refractive-index metallic nanopillars. The operational principle of the newly proposed device is based on the phenomenon of total external reflections in ultralow-refractive-index metallic photonic crystal structures (metamaterials). In addition we provide detailed design guidelines for optimum device performance. The low propagation losses and compact size, as well as temperature-insensitive operation over a wide temperature range, are only a few of the advantages of the proposed technology, making this new type of demultiplexer an excellent candidate for applications in the visible spectrum.     

Proposal for ideal 3-dB splitters-combiners in photonic crystals

We propose a structure for ideal 3-dB splitters (1 x 2)-combiners (2 x 1) in photonic crystals. In photonic crystals, ideal 3-dB splitters based on a three-port system are achievable in principle, but it is impossible to achieve ideal 3-dB combiners based on the three-port system because there is no path for a loss, owing to strong confinement of photons. The proposed structure is based on a four-port system in which the concept of a microwave circuit, the so-called rat-race circuit is adopted. Design conditions for two-dimensional photonic-crystal-based rat-race circuits have been investigated by use of the coupled-mode theory in time. With the proposed structure, a 3-dB splitter-combiner has been designed. The performance of the device was numerically calculated by the finite-difference time-domain method.     

光分组交换矩阵的实验研究

对光交换矩阵的基本机理进行了研究,介绍了所研制成功的光分组交换矩阵的基本结构、功能、性能和相关的实现技术,重点分析了质子交换型铌酸锂（APE：LiNbO3)光波导开关与相应的系统技术,给出了2．5Gbit/s异步转移模式（ATM）光信元交换实验研究结果。     

Multilayer dielectric cylindrical mirrors based on omnidirectional reflection from a one-dimensional photonic crystal

A multilayer dielectric cylindrical mirror (MDCM) based on the one-dimensional omnidirectional reflection of a photonic crystal is presented. In this case, the refractive indices of the two materials are 1.6 (polystyrene) and 4.6 (tellurium), and the corresponding optimized thicknesses are 0.75a and 0.25a. A very high reflectance over a wide frequency range is observed. In this case, a is the lattice constant of the photonic crystal. In this band, the MDCM has good reflection and focal properties. Therefore, it is feasible to use the MDCM for integrated waveguide devices. As an example, an etched diffraction grating demultiplexer based on the MDCM is also proposed. Both the operational principle and design of the device are introduced. This provides a method for designing compact integrated waveguide devices.     

Formation of photonic crystals using elastic waves amplified by the double frequency electromagnetic field

A technology is proposed for forming acoustic-wave photonic ferroelectric crystals without using photolithography. The technology is based on amplification of acoustic waves by the pumping with the double-frequency electromagnetic field. This approach allows excitation of the piezoelectric transducer in the gigahertz range by low-power radio pulses that reduces the breakdown danger for the piezoelectric layer which is only few micrometers thick or even thinner.     

超稳光生微波源研究进展

随着科技的进步以及精密测量应用技术的不断提高,超稳微波源的稳定度和噪声水平等技术要求不断提高,应用范围愈加广泛,包括高性能频标研究、网络雷达研制、深空导航系统等方面.基于超稳激光和飞秒光梳的超稳光生微波源是目前频率稳定度最高的微波频率源,相对频率稳定度可达10~(16)@1 s量级.该装置也是未来频率标准(光频标)推广应用的基础,无论是时间的产生还是绝大多数的精密测量,都需要将光频标的输出激光变换为超稳的基带频率信号后才能够实现.本文介绍了超稳光生微波源技术的发展、现状和应用需求.以国家授时中心研制的国内首套超稳微波频率源技术为主线,介绍了超稳光生微波源的原理和结构以及各组成部分的技术发展情况:超稳激光方面,着重介绍超稳光学腔研究和研制的进展以及Pound-Drever-Hall锁频技术、剩余幅度调制等噪声抑制技术;飞秒光梳方面,着重介绍目前最常用的掺铒光纤光梳系统的激光锁模、频率控制等技术发展;低噪声光电探测方面,着重介绍宽带光电探测噪声抑制技术和激光幅度噪声引起微波相位噪声的抑制技术.最后对光生超稳微波技术进行了总结和展望.     

基于自准直效应的光子晶体异质结偏振分束器

基于光子晶体的自准直效应和禁带特性,提出了一种具有非正交异质结结构的光子晶体偏振分束器.无需引入缺陷或波导,可使光波在该结构中准直无发散地传输并实现分束功能,对制造工艺的要求大大降低.利用Rsoft软件,结合平面波展开法和二维时域有限差分法,对提出的偏振分束器进行了仿真研究.结果表明,该偏振分束器在一个较大的频率范围f=0.275—0.285(a/λ)内可实现横电(TE)和横磁(TM)模的大角度偏振分离,TE和TM模的透过率均在88%以上,偏振消光比分别大于26.57 dB和17.50 dB.该结构可应用到太赫兹波段的传输系统中,a=26μm,尺寸大小为572μm×546μm,在91—95μm波长范围内可实现TE和TM模的分离.利用该结构可设计用于光通信系统(n=3.48)的偏振分束器,a=426.25 nm,结构仅为9.38μm×8.95μm.本方案结构简单,易于集成,有望在集成光路的发展中发挥重要作用.     

Simulation of surface-modified porous silicon photonic crystals for biosensing applications

In this work realistic biosensing structures based on the integration of porous silicon photonic crystals with polymer coating technology are presented. Microcavities and rugate filters are chosen as the photonic crystal configuration. The deposition of a polymer layer on the pore walls of these structures is proposed to improve the selectivity and sensitivity of the sensing function. A complete effective refractive index model including the polymer layer, the target and external effects like silicon oxidation has been developed in order to accurately simulate the structures. It is expected that the proposed structures could be used as low cost, highly integrated and highly sensitive biological sensors.     

Design of a highly sensitive photonic crystal waveguide platform for refractive index based biosensing

In this paper, a photonic crystal waveguide platform on silicon-on-insulator substrate is proposed in order to realize a highly sensitive refractive index based biosensor. Following the design, the analysis of the sensor structure are made by using the three dimensional Finite Difference Time Domain method. The principle of sensing is based on the change in refractive index, which in turn changes the output spectrum of the waveguide. Results show that the sensitivity of the sensor depends mainly on the geometrical properties of the defect region of the photonic crystal structure. The phenomenon is verified for various samples having refractive index ranging from 1 (air) to 1.57 (Bovine serum albumin). Further, the structure is compared with few other conventional photonic crystal waveguide designs to analyze the sensing performance. The estimated value of sensitivity of the sensor is found to be 260 nm/RIU with a detection limit of 0.001 RIU. This high sensitivity can enhance the performance of low-concentration analytes detection.     

Study of heat transfer characteristics in PCFG fabrication technology using heat method

The fiber gratings fabrication technology with the heating method in a photonic crystal fiber (PCF) based on structural change is examined. The principle of photonic crystal fiber gratings (PCFGs) is analyzed in theory. The heat transfer theory and finite element method are used to examine the thermal field distribution in the fiber and the influence of the air hole structure in the cladding, and the parameters of the laser beam in the process of grating fabrication are discussed. The results show that gratings can be formed by the periodic collapse of air holes in the cladding of PCFs. Under double-point heating condition, the energy is uniformly distributed in the radial direction and is approximate to Gaussian distribution in the axial direction. With the same size of the luminous spot, as the layers and radius of the air holes increase, the laser power needed to make the air holes collapse decreases. With the same laser power, as the luminous spot radius increases, the needed heating time increases. Moreover, the relationship between the laser power needed and the air filling rate is obtained as the number of layers of the air holes changes from 1 to 7. This kind of PCFG can overcome the long-term thermal instability of conventional gratings in substance and thus has great potential applications in the related field of optical fiber sensors.