新型光子晶体THz滤波器

提出了一种新型基于光子晶体的太赫兹滤波器,该滤波器在线缺陷中设计了由三个点缺陷构成的谐振腔,能够实现双波长的高效滤波功能。文中使用平面波展开法(PWM)分析了正方晶格光子晶体的带隙结构,并利用时域有限差分法(FDTD)研究了滤波器的一些性能指标。仿真结果表明,该新型滤波器能够把频率为3.413 THz和3.222 THz的太赫兹波滤出,并且具有滤波带宽窄、体积小等优点。     

基于光子晶体光纤F-P腔的高压电器温度传感器系统

基于光子晶体光纤F-P的窄带滤波特性和液晶折射率对温度变化敏感特性,提出了一种用于高压电器温度测量的温度传感器系统.该系统主要由液晶填充的光子晶体光纤F-P腔传感器、光纤F-P滤波器、放大电路和显示模块组成.将向列型液晶填充在光子晶体光纤F-P腔内,温度变化引起最大反射光强点波长的变化,采用光纤F-P腔滤波器解调出光波...     

光子晶体的研究及其在传感器中的应用

光子晶体是指具有光子带隙(PBG)特性的人造周期性电介质结构,有时也称为PBG光子晶体结构。按照光子晶体的光子禁带在空间中所存在的维数,可以将其分为一维光子晶体、二维光子晶体和三维光子晶体。光子晶体传感器应用包括应变传感器、温度传感器、化学传感器、光子晶体光纤传感器、长周期光纤光栅(LPFG)生物传感器、LPFG化学传感器等。本文从光子晶体传感器的概述、研究现状和应用几方面对光子晶体传感器的应用进展进行了综述,希望对光子晶体传感器有一个比较全面的了解。     

PCF色散系数与场分布的近似特性分析

本文基于等效折射率模型将光子晶体光纤等效为传统阶跃光纤,通过对微结构中基模的本征方程的求解,得到了包层有效折射率、归一化频率、群速度色散系数以及电场分布等特性与波长的关系,并分别讨论了光子晶体光纤孔间距固定和孔半径固定的情况下对光纤特性的影响,分析表明,通过改变光子晶体光纤的结构参数可以适当地调整光纤的特性,从而对不同的应用场合下光子晶体光纤的定性设计提供了一定的理论依据。     

Energy‐efficient liquid‐crystal displays (e2‐LCDs) using a photonic‐crystal backlight system

Abstract— Cholesteric liquid crystals automatically form one‐dimensional photonic crystals. For a photonic crystal in which light‐emitting moieties are embedded, unique properties such as microcavity effects and simultaneous light emission and light reflection can be expected. Three primary‐color photonic‐crystal films were prepared based on cholesteric liquid crystal in which fluorescent dye is incorporated. Microcavity effects, i.e., emission enhancement and spectrum narrowing, were observed. Two types of demonstration liquid‐crystal displays (LCDs) were fabricated using the prepared photonic‐crystal films in a backlight system. One is an area‐color LCD in which a single photonic‐crystal layer is used for each color pixel and the other is a full‐color TFT‐LCD in which three stacked photonic‐crystal layers are used as light‐conversion layers. The area‐color LCD was excited by using 365‐nm UV light, and the full‐color TFT‐LCD was excited by using 470‐nm blue LED light. Because of the photonic crystal's unique features that allow it to work as light‐emitting and light‐reflecting layers simultaneously, both LCDs demonstrate clear readable images even under strong ambient light, such as direct‐sunlight conditions, under which conventional displays including LCDs and OLED displays cannot demonstrate clear images. In particular, an area‐color LCD, which eliminated color filters, gives clear images under bright ambient light conditions even without backlight illumination. This fact suggests that a backlight system using novel photonic‐crystal layers will be suitable for energy‐efficient LCDs (e²‐LCDs), especially for displays designed for outdoor usage.     

Two-Dimensional Tunable and Temperature-Insensitive Lyot Filter for FM-to-AM Compensation

Utilizing polarization maintaining photonic crystal fiber(PM-PCF)with the low temperature coefficient of birefringence,a two-dimensional tunable and temperature...     

Photo‐aligned photonic ferroelectric liquid crystal fibers

Preliminary studies of photonic crystal fibers (PCFs) partially infiltrated with photo‐aligned ferroelectric liquid crystals (FLCs) under the influence of external electric field are reported. The proper alignment of the FLC molecules is achieved by generating a photo‐aligning layer on the inner side of the PCF microcavities. The sulfonic azo dye, which is used as an alignment layer, offers a variable anchoring energy depending on the irradiation energy, and thus, a good control on the FLC alignment inside microchannels is possible. Moreover, a state of polarization of the light being guided inside the PCF infiltrated selectively with FLC changes under the influence of external electric field.     

空心光子晶体光纤在拉曼光谱仪中的应用

针对拉曼散射是一种弱散射,同时由于空心光子晶体光纤(HC—PCF)能显著增强光与填充介质之间的相互作用,提出将HC—PCF应用到拉曼光谱仪中,利用平面波展开法对HC—PCF的光子带隙与场分布进行模拟分析,探讨了HC—PCF的参数对拉曼散射强度的影响。通过理论研究发现光子晶体光纤可根据实际应用的需要,通过改变光纤的周期结构或包层气孔之间的间距来改变光子带隙,从而可传输不同波段的光。结果表明了HC—PCF在拉曼光谱仪中应用的可行性,为拉曼光谱仪在分子结构检测与分析提供了新的技术方法,也为HC—PCF的应用和研究开拓了广阔前景。     

A Boundary Integral Equation Method for Photonic Crystal Fibers

A boundary integral equation for the eigenmode of photonic crystal fibers is formulated and numerically solved using the Nystr?m method. The real and imaginary parts of the propagation constant, which are related to the dispersion and the confinement loss of fibers, are obtained using a secant method. This formulation is very flexible to handle the fiber geometry, and therefore can be applied to photonic crystal fibers with novel refractive index profile and hole geometry.Min Hyung Cho: Support for this work is partially provided by the National Science Foundation Grant DMS-0408309 and the Department of Energy Grant DE-FG02-05ER25678.     

二维复式晶格光控四波长太赫兹波调制器

给出的基于复式晶格光子晶体的太赫兹波调制器是一种用数字基带信号对太赫兹载波进行强度调制的外调制器。该调制器利用复式晶格一个点缺陷可同时调制两个缺陷模的特点来同时控制四束不同太赫兹波的传输,从而实现对太赫兹载波的通、断调制。这种基于复式晶格光子晶体的调制器具有光子禁带大、体积小,了等许多优点。     

A broadband wide‐incident‐angle reflective polarization converter

Abstract— A high‐performance reflective polarization converter which could be used in a backlight recycling system for liquid‐crystal‐display (LCD) devices is proposed. The device consists of a twisted‐nematic (TN) liquid‐crystal film, a uniaxial A‐plate, and a reflector. The configuration parameters, such as thickness and orientation of the films, are optimized using a genetic algorithm. As a result, the design can convert light from TM to TE polarization (or TE to TM) at a maximum 99.7%, minimum 91.3%, and average 96.7% conversion efficiency for the entire visible spectrum and incident angle from 0 to 60°. Such a broadband reflective polarization converter is particularly useful for enhancing the light efficiency and reducing the power consumption of LCDs.     

Numerical analysis of fiber optical parameter amplifier based on triangular photonic crystal fiber

Due to triangular photonic crystal fiber (PCF) high nonlinearity and low dispersion slope, using the condition that the different linear phase shift combination must satisfy the phase match, the expressions of gain and bandwidth for one-pump fiber-optic parametric amplifiers (1P-FOPA) based on PCF in the normal and abnormal dispersion regimes are derived respectively. Then, 1P-FOPAs performance comparison among PCF, dispersion-shifted fiber (DSF) and highly nonlinear fibers (HNLF) are carried out by numerical simulations. It is shown that the 1P-FOPA based on triangular PCF can provide higher peak gain over wider bandwidth. When the pump wavelength is at the zero-dispersion wavelength (ZDWL), about 108.7 nm single-pass gain bandwidth and 91.4 dB peak gain can be obtained; when in the normal dispersion regime and near zero-dispersion wavelength, not less than 46 nm single-pass gain bandwidth 77.1 nm away from pump can be achieved. Finally the influence of dispersion fluctuation is analyzed, and the result shows that the tolerance of the 1P-FOPA based on photonic crystal fiber is better.     

三态光纤通信收发器的设计与实现

针对三态光纤通信的原始设计光路图,依据可控光源的特点和时间冗余技术,提出了2种相应的光路简化方案,得到了较易实现的工程光路图,通过液晶器件实现偏振键控,以嵌入式系统控制液晶器件的显示,制作了一台三态光纤通信收发器,实现了单工、单光纤、单信道的三态光纤通信。试验证明了三态光纤通信原理的正确性和可行性,为三态光纤通信走向实用奠定了实验基础。     

Holographic display technology based on liquid crystal device

Holographic display technology can reconstruct the same images of the original objects exactly, which has played a more and more important role and become the goal of the three‐dimensional display. As liquid crystal devices can modulate the polarization state of light, they have been widely used in the holographic display to modulate the phase and amplitude of information. Among them, liquid crystal spatial light modulator and liquid crystal lens are two important devices in the holographic diffraction. In this paper, several liquid crystal devices have been introduced and the holographic display technologies based on these liquid crystal devices have been discussed. The merits and demerits of these technologies based on the liquid crystal devices have been analyzed, and the outlook of the holographic display is given in the end.     

Multifunctional glassy liquid crystals for photonics

Abstract— As an emerging class of photonic materials, morphologically stable glassy liquid crystals, were developed following a versatile molecular design approach. Glassy cholesteric liquid crystals with elevated phase‐transition temperatures and capability for selective‐wavelength reflection and circular polarization were synthesized via deterministic synthesis strategies. Potential applications of glassy cholesteric liquid crystals include high‐performance polarizers, optical notch filters and reflectors, and circularly polarized photoluminescence. A glassy nematic liquid crystal comprising a dithienylethene core was also synthesized for the demonstration of nondestructive rewritable optical memory and photonic switching in the solid state.     

一维光子晶体液晶微谐振腔的温度特性

在光子晶体中引入液晶缺陷,形成一维光子晶体液晶微谐振腔.用传输矩阵法研究了这种微谐振腔的温度特性,用E1液晶微谐振腔进行了模拟数值计算.计算结果表明,液晶微谐振腔的特性与温度和液晶分子排列密切相关;对于液晶排列沿平行介质表面的微谐振腔,当温度升高时缺陷峰波长向长波长方向漂移,半高宽度增大, 品质因子减小;而液晶排列沿介质表面法向的微谐振腔的温度变化情况则相反;温度灵敏度和透射峰高度均随温度升高而增大.温度特性为非线性关系,并随温度接近液晶相变点而变化迅速,与现有的各向同性材料微谐振腔的温度特性不同.     

基于光子晶体光纤的血糖监测系统研究

介绍了以光子晶体光纤为核心,结合光电微损法血糖监测技术,设计了新型的血糖监测系统。根据血样中不同血糖含量对光吸收不同的原理,利用MSP430对光进行控制,通过三探头光纤束传感器传输,照射到被测血样,调制后,带有血糖信息的反射光由光电转换放大,输入MSP430,经A／D转换后计算出血糖含量。系统具有操作简便、功耗小等特点。     

Low‐voltage and high‐transmittance blue‐phase liquid‐crystal device with slanted electrodes

Abstract— A low‐voltage (～10 V_rms) and high‐transmittance (～90%) polymer‐stabilized blue‐phase liquid‐crystal (BPLC) device with a slanted‐electrodes structure is proposed. Unlike the vertical‐field‐switching (VFS) mode in which oblique incident light and a vertical field are employed, the proposed device utilizes normal incident light and an oblique field. The slanted electrodes generate a strong and uniform oblique electric field, which contributes in obtaining low voltage and high transmittance. Moreover, no couple films or prism sheets are needed, which helps to enhance the optical efficiency and simplify of the device structure. This device has great potential application for emerging BPLC displays and photonic devices.     

Polarization‐independent modulation for projection displays using small‐period LC polarization gratings

Abstract— Progress in the use of liquid‐crystal polarization grating (LCPG) to modulate unpolarized (and polarized) light with a grating period as small as 6.3 μm is reported. Similar to LCPGs formed at larger periods (11 μm) reported previously, polarization‐independent switching, predominantly three diffraction orders, maximum contrast ratios of ～100:1 for unpolarized broadband light, very low scattering, and diffraction efficiencies >98% continue to be observed. The smaller period led to an expected lower threshold voltage, even though the thickness was greater. Because the smaller grating period enables a brighter result from a Schlieren projection scheme for a microdisplay using the LCPG light valve, the inherent tradeoffs involved with both material and design parameters are discussed, and prospects for a polarization‐independent projection display are commented upon.     

Electric‐field‐driven LC lens for 3‐D/2‐D autostereoscopic display

Abstract— The use of an electric‐field‐driven liquid‐crystal (ELC) lens cell for switching between a 3‐D and 2‐D display is proposed. Due to the phase retardation of the non‐uniform LC directors, an ELC lens functions the same as a geometric lens. The parameters of an ELC for 3‐D applications are optimized through the simulation of the electrode configuration and voltage levels. A prototype was made where the ELC lens is placed in front of a liquid‐crystal display (LCD) 15 in. on the diagonal with a 99‐μm subpixel pitch. Under zero voltage, the ELC lens is a transparent medium and the users can see a clear 2‐D image. In 3‐D mode, the ELC lens array performs the same as a cylindrical lens array to the incident vertical polarization under suitable driving voltages. Placing a half‐wave plate between the LCD and ELC lens is proposed to change the polarization of the LCD to be parallel with the polarization lens direction of the ELC lens. The measurement of the horizontal luminance profile, performance of the ELC lens, and feasibility for 3‐D/2‐D switching was verified. The fabrication process for the ELC lens is compatible with the current LCD production process and enables the accurate control of the lens pitch of the ELC lens.