铁电薄膜铁电性能与温度关系的一种实时测量实验方法

介绍了一种实时测量铁电薄膜的铁电性能与温度关系的实验方法,为进一步研究铁电薄膜的特性提供了实验基础。     

光子晶体波导中的孤子传输及其延迟特性研究

研究了正方晶格和三角晶格空气背景硅介质柱光子晶体线缺陷波导导模左带隙边缘处的亮孤子脉冲传播特性及其慢光延迟特性. 采用平面波展开法仿真分析了波导相邻两行介质柱大小r₁和r₂以及波导宽度D对孤子脉冲传输所需峰值功率P₀和延迟时间T_s的影响,总结了其变化规律. 通过调整波导结构得到了正方晶格和三角晶格优化波导结构,优化后,正方晶格结构波导P₀减小了81.17%,T_s增加了66.32%;三角晶格结构波导P₀减小了73.7%,T_s增加了67.63%,实现了孤子传输性能的大幅度优化. 关键词： 光子晶体波导 光孤子 峰值功率 延迟时间     

Resonant optical transmission through a one-dimensional photonic crystal adjacent to a thin metal film

We theoretically and experimentally reveal that the large resonant optical transmission (ROT) can be realized through a one-dimensional photonic crystal adjacent to a thin metal film, at a frequency in the original band-gap of the photonic crystal (PC). The influence of periodic number of PC and the thickness of the adjacent metal on the transmission frequency and intensity is studied in detail. An optimum design is given to reach the maximum transmission efficiency, meanwhile a mechanism underlining the ROT phenomenon is proposed. An effective admittance-matching theory is proposed to understand this effect and quantitatively determine the operating frequency, which matches very well with the simulated and measured results. The effects might be very useful to realize some optical filters and sensor devices since the structure is easy for mass production and is matured technically to be prepared in industry.     

基于光纤的三维可调胶体光子晶体

用改进的垂直沉积法在光纤端面制备了高质量的SiO₂胶体光子晶体,经过烧结、固化构成胶体光子晶体-光纤结构. 用扫描电子显微镜确定了样品为面心立方密排结构,其密排面平行于光纤基底表面. 利用全光纤传感网络测试了该胶体光子晶体,反射峰中心位于845 nm处,与Bragg理论计算值符合很好. 将该样品浸入不同折射率的液体中,反射光谱的峰值位置随着液体折射率的改变而发生偏移,近似呈线性关系,实现了峰位可调. 对于不同浓度引起的液体折射率的变化,基于光纤的胶体光子晶体结构也能够很好地分辨出来. 关键词： 可调胶体光子晶体 2微球')" href="#">SiO₂微球 Bragg反射 光纤     

通讯波段禁带胶体光子晶体的制备及实验参数研究

采用直径为700nm的二氧化硅微球,通过垂直沉积法在玻璃基片上制备了位于光通讯波段的禁带胶体光子晶体。研究了不同蒸发温度、湿度条件、干燥过程对样品晶体质量的影响。用扫描电子显微镜(SEM)对其形貌进行了观测。实验结果表明,在温度为65℃,相对湿度为70%,缓慢干燥条件下制备出的样品具有较好的晶体质量,晶体在大范围内保持了面心立方(FCC)单晶结构,其(111)面平行于生长基片。     

Long-range propagation of plasmon polaritons in a thin metal film on a one-dimensional photonic crystal surface

We present experimental results on ultralong-range surface plasmon polaritons, propagating in a thin metal film on a one-dimensional (1D) photonic crystal surface over a distance of several millimeters. This propagation length is about 2 orders of magnitude higher than the one in the ordinary Kretschmann configuration at the same optical frequency. We show that a long-range surface plasmon polaritons propagation may take place not only in a (quasi)symmetrical scheme, where a thin metal film is located between two media with (approximately) the same refraction index, but also in a scheme where the thin metal film is located between an appropriate 1D photonic crystal and an arbitrary (air, water, etc.) medium. The ultralong-range surface plasmon polaritons are potentially important for biosensors, plasmonics, and other applications.     

A study of the propagation of electromagnetic pulses through photonic crystal structures

A mathematical model for the study of two- and three-dimensional photonic crystals and of waveguide systems based on them was designed and applied. The numerical algorithm for the construction of the solution was built using such numerical methods as the method of finite differences in the time domain (FDTD), the TS/SF method, and the method of a perfectly matched layer (PML), which makes it possible to apply the algorithm under consideration to the study of other waveguide systems as well. The results of the simulation of particular waveguide systems are presented.     

Pressure and temperature controlled self-assembly of high-quality colloidal crystal films on optical fibers

High-quality annular colloidal multilayer films coated on an optical fiber were fabricated from aqueous solutions by the modified vertical deposition method with controllable pressure and temperature. The resulting cylindrical annulus was characterized by the scanning electron microscopy (SEM), and the SEM images illustrated the [111]-like plane of face-centered-cubic (fcc) structures parallel to the surface of the optical fiber. Transmission spectra demonstrated deep photonic band gap (PBG) of up to 76% and steep photonic band edge (PBE) of up to 5.2%/nm, as well as the excellent cylindrical symmetry was affirmed with off-axis incidence light. With the angles of out-of-plane incidence increasing from 0 to 60°, the peak positions and transmittance decreased gradually which agreed well with the Bragg formula.     

CdSe量子点滤光片尺寸、温度依赖的光学特性

为了缩小光谱仪体积使之适用于军事卫星等领域,本文将胶体量子点作为滤光材料,研究了CdSe胶体量子点滤光片的光学特性.本文采用热注入法合成出了高质量的CdSe胶体量子点,经过对苯二胺消光处理制备成CdSe胶体量子点滤光片.利用透射电子显微镜(TEM)进行样品形貌结构的表征及粒径尺寸的测量,并分别在不同温度下进行了紫外.可...     

Fabrication of two-dimensional elliptic photonic lattices in photorefractive crystal by optical induction method

We fabricate two-dimensional elliptic photonic lattices in iron-doped lithium niobate photorefractive crystal for the first time with optical induction method. The experimental setup of our method is very simple and flexible without complicated optical adjustment system. We analyze and verify the two-dimensional elliptic photonic lattices by plane wave guiding, far field diffraction pattern imaging, and Brillouin-zone spectroscopy. Induced elliptic photonic lattices can stably exist for a long time in the iron-doped lithium niobate crystal. The induced two-dimensional elliptic photonic lattices might offer an easy method to study generic band gap phenomena in anisotropic periodic structures.     

Temperature dependence of birefringence in olarization-maintaining photonic crystal fibres

In this paper,the temperature dependence of birefringence in polarization maintaining photonic crystal fibres(PMPCFs) is investigated theoretically and experimentally.Utilizing the structural parameters of the PM-PCF samples in the experiment,two effects leading to the birefringence variation under different temperatures are analysed,which are the thermal expansion of silica material and the refractive index variation due to the temperature variation.The actual birefringence variation of the PM-PCF is the combination of the two effects,which is in the order of 10-9 K-1 for both fibre samples.Calculation results also show that the influence of refractive index variation is the dominant contribution,which determines the tendency of the fibre birefringence variation with varying temperature.Then,the birefringence beat lengths of the two fibre samples are measured under the temperature,which varies from -40℃ to 80℃.A traditional PANDA-type polarization maintaining fibre(PMF) is also measured in the same way for comparison.The experimental results indicate that the birefringence variation of the PM-PCF due to temperature variation is far smaller than that of the traditional PMF,which agrees with the theoretical analysis.The ultra-low temperature dependence of the birefringence in the PM-PCF has great potential applications in temperature-insensitive fibre interferometers,fibre sensors,and fibre gyroscopes.     

Adaptive split-step Fourier method for simulating ultrashort laser pulse propagation in photonic crystal fibres

In this paper, the generalized nonlinear Schr\"{o}dinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton self-frequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.     

Cladding-ring-equivalent effective index method for analyzing the propagation characteristics of multi-cladding photonic crystal fibers

Cladding-ring-equivalent effective index method (CREEIM) is proposed to analyze the propagation characteristics in the multi-cladding photonic crystal fibers (MCPCFs). The effective indices and dispersions of the step index two and three-cladding structures are calculated with the Sellmeier formula. The accuracy of CREEIM is competitive to the results calculated by the multipole method (MPM). With different structure parameters, the differences between two methods are evaluated with the relative error R_E of effective index and relative difference R_D of dispersion. This method is also used to analyze the mode cut-off and nonlinear characteristics in the three-cladding structure PCFs by calculating the mode effective index n_eff instead of complex mode field distribution.     

Tunable properties of light propagation in photonic liquid crystal fibers

Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].     

Soliton-like propagation of light pulses in a nonlinear photonic crystal

On the basis of computer simulation, we analyze the dynamics of interaction of subpulses localized inside certain layers of a one-dimensional nonlinear photonic crystal. Localized subpulses are shown to move and interact like solitons. Possible scenarios of their interaction are described: a spatially periodic regime, the merging of several subpulses with similar characteristics into a single higher intensity and more slowly propagating subpulse, and the formation of an immovable pulse in a layer of the photonic crystal. To verify the results of the computer simulation and to elucidate the nature of spatially localized structures forming, a comparison with the analytical solution for a medium with cubic nonlinearity is performed.     

从光子晶体效应到表面等离子波的实时演变

文章报道了激光诱导太赫兹表面等离子谐振效应。采用激光抽运-太赫兹波探测技术,实时改变单晶硅中的载流子浓度,使其介电特性从类绝缘体演变为类金属导体,以支持表面等离子谐振效应,进而实现太赫兹波在周期性亚波长单晶硅孔阵列中的实时可控制谐振增强传输。同时还通过实验观测到太赫兹波从光子晶体效应到表面等离子波的实时演变。文章作者采用Fano模型对实验结果进行模拟分析,获得了与实验数据一致的理论拟合。     

从光子晶体效应到表面等离子波的实时演变

文章报道了激光诱导太赫兹表面等离子谐振效应。采用激光抽运-太赫兹波探测技术，实时改变单晶硅中的载流子浓度，使其介电特性从类绝缘体演变为类金属导体，以支持表面等离子谐振效应，进而实现太赫兹波在周期性亚波长单晶硅孔阵列中的实时可控制谐振增强传输。同时还通过实验观测到太赫兹波从光子晶体效应到表面等离子波的实时演变。文章作者采用Fano模型对实验结果进行模拟分析，获得了与实验数据一致的理论拟合。     

A novel method of rapidly modeling optical properties of actual photonic crystal fibres

<正>The flexible structure of photonic crystal fibre not only offers novel optical properties but also brings some difficulties in keeping the fibre structure in the fabrication process which inevitably cause the optical properties of the resulting fibre to deviate from the designed properties.Therefore,a method of evaluating the optical properties of the actual fibre is necessary for the purpose of application.Up to now,the methods employed to measure the properties of the actual photonic crystal fibre often require long fibre samples or complex expensive equipments.To our knowledge, there are few studies of modeling an actual photonic crystal fibre and evaluating its properties rapidly.In this paper,a novel method,based on the combination model of digital image processing and the finite element method,is proposed to rapidly model the optical properties of the actual photonic crystal fibre.Two kinds of photonic crystal fibres made by Crystal Fiber A/S are modeled.It is confirmed from numerical results that the proposed method is simple,rapid and accurate for evaluating the optical properties of the actual photonic crystal fibre without requiring complex equipment.     

Birefringence sensitivity to temperature of polarization maintaining photonic crystal fibers

In this paper, we investigate the birefringence of polarization maintaining photonic crystal fibers (PM-PCFs) under thermal effect. Modeling and simulation of PM-PCFs under thermal effect are conducted. Birefringence in a PM-PCF as a function of the temperature is measured experimentally. The experimental results are in agreement with theoretical calculation, and show that the relative temperature dependent birefringence coefficient of the PM-PCF, dΔn/dT/Δn, is 2.93×10^?5/°C, which is typically ～35 times less than that of conventional panda fibers. The insensitivity of polarization properties in PM-PCFs to temperature is demonstrated. These findings have important benefits in fiber optic systems and sensors, especially in fiber optic gyroscopes (FOG) where it translates into a lower polarization error and thus a higher measurement precision.     

Analysis of femtosecond optical pulse propagation in one-dimensional nonlinear photonic crystals using finite-difference time-domain method

In this paper, we have used the finite-difference time-domain (FDTD) method to analyze the optical pulse propagation in a nonlinear, one-dimensional photonic crystal (1DPC). Hyperbolic secant pulses with various carrier wavelengths are utilized in this study. In a nonlinear regime, a 1DPC introduces a photonic band-gap whose central wavelength and width depend on the input pulse intensity. In the present work, three different cases are considered. These correspond to the carrier wavelengths of the incident pulses being out of, near to, and partially in the band-gap. For each case, the effect of nonlinearity on pulse propagation is investigated. Also, we have analyzed the two-frequency regime, in which each of the two pulses has a different carrier frequency (wavelength). This kind of study can be done directly with FDTD without any further computational burden but it is somewhat complicated using nonlinear coupled-mode equations (NLCME) and nonlinear Schrödinger equation (NLSE), which require separate treatments for each carrier wavelength.