共查询到20条相似文献,搜索用时 15 毫秒
1.
Real-time holographic reflection gratings in volume media of azo-dye-doped poly(methyl methacrylate) 总被引:1,自引:0,他引:1
Real-time formation of holographic reflection gratings is experimentally demonstrated in thick media of Disperse Red 1- (DR-1) doped poly(methyl methacrylate) at a nonresonant wavelength (647 nm). Our diffraction efficiencies of 30% and 23% are achieved for reflection gratings inscribed by spatial modulation of intensity and polarization, respectively, and are believed to be the highest achieved for a dye-doped polymer. In addition to the recording of amplitude and phase, the polarization state is also recorded and reconstructed. 相似文献
2.
A novel type of sampled fiber Bragg gratings (FBGs) written in polarization-maintaining fiber (PMF) is proposed. The reflection spectrum, time delay, and group velocity dispersion (GVD) of the gratings are analyzed. In addition, the reflection spectrum is optimized by apodization. The scheme of multi-wavelength output based on the gratings is proposed, which could be used as a multi-wavelength polarization filter in the density wavelength division multiplexed (DWDM) system. 相似文献
3.
Separating lights into different paths according to the polarization states while keeping their respective path's polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters(PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles. 相似文献
4.
弱双折射光纤布喇格光栅反射偏振对温度响应特性的研究 总被引:1,自引:0,他引:1
理论分析了切趾弱双折射光纤布喇格光栅反射偏振相关特性与温度之间的关系.数值模拟了切趾弱双折射光纤光栅的反射谱、偏振相关损耗和差分群时延随波长变化曲线.实验测出了不同温度下反射谱、偏振相关损耗和差分群时延随波长变化曲线.根据实验结果对偏振相关损耗和差分群时延的变化情况作出了分析.反射偏振相关损耗呈现两个峰值,随温度增加两峰漂移程度相同,表明偏振相关损耗无明显差异.差分群时延最大值随温度增加成线性向长波方向漂移,证明了光纤光栅正交模损耗变化的等同性.综合理论分析与实验结果表明:切趾弱双折射光纤布喇格光栅的偏振特性随温度产生明显的变化,其正交模变化呈现等比例特性. 相似文献
5.
We report diffraction gratings recording in polymer dispersed liquid crystals (PDLC) material with a beam suffering total internal reflection from the sample air surface. The real time diffraction efficiency kinetics as well as the polarization, voltage behavior and angular selectivity of the gratings are studied at different reconstruction geometries. An increase of three times of the diffraction efficiency in case of applied voltage is observed for one of these geometries in opposite to typical PDLC switchable gratings. Such dependence appears in most of the geometries and is connected to the specific formation of two gratings by the Stetson scheme. 相似文献
6.
Switchable dual-wavelength Erbium-doped fiber ring laser with cascaded fiber Bragg gratings 总被引:1,自引:0,他引:1
Jae-Ho Han 《Optik》2010,121(24):2266-2268
We have experimentally shown wavelength mode switching in a dual-wavelength Erbium-doped single cavity fiber laser where the initial two wavelengths of 1 nm spacing are determined by the cascaded reflection type short-period fiber Bragg gratings having two different centre wavelengths of 1550.5 and 1551.5 nm. The lasing mode depends on the polarization in the ring cavity to migrate from one wavelength to another or operates in both modes in a polarization beam splitter output. To effectively control the polarization in the ring cavity, the polarization controllers were positioned before and after the polarization beam splitter. This method of wavelength switching provides a simple way of mode tuning in dual-wavelength fiber lasers. 相似文献
7.
均匀光纤布拉格光栅的反射偏振相关损耗特性 总被引:6,自引:0,他引:6
研究了单模光纤布拉格光栅的偏振相关损耗(PDL)特性.运用耦合模理论和琼斯(Jones)矩阵提出了反射光的有效偏振相关损耗(PDLeff),并模拟r其随光栅参数和双折射量的变化性质.光栅反射光的偏振相关损耗在反射谱的带边处明显地表现出来,特别是带边比较陡峭时.结果表明,光栅的有效偏振相关损耗明显地依赖于光栅的结构参数和... 相似文献
8.
In magneto-optical gratings the magnetic dipolar coupling superimposed on the electric dipolar one introduces nonreciprocity and spectral discrimination between circular polarization states, measured by a Zeeman-like splitting of the photonic Bragg resonances. In a nonlinear regime the degree of nonreciprocity is modified by the photoinduced interplay of these splittings and their Stark-like shifts. We predict novel magneto-optical modulation schemes for switching between orthogonal circular polarization states of transmission or reflection operated by means of an intense linearly polarized optical pulse train. 相似文献
9.
Zhao Chun-Liu Yang Xiufeng Lu Chao Ng Jun Hong Guo Xin Partha Roy Chaudhuri Dong Xinyong 《Optics Communications》2004,230(4-6):313-317
A novel and simple Erbium-doped fiber laser by using cascaded fiber Bragg gratings (FBGs) written in high-birefringence fibers for switchable multi-wavelength operation is proposed. Due to two-peak reflection with orthogonal polarizations of the FBG, the polarization hole-burning effect in the cavity is greatly enhanced. Experimental results show that the stable dual- and three-wavelength lasing operation with very narrow wavelength separation (0.39 nm) can be generated at room temperature. The configuration is simple and flexible. Only by adjusting polarization controllers (PCs), the laser can be switched among the stable single-, dual- and three-wavelength lasing operations. 相似文献
10.
用瑞利-傅里叶(Rayleigh-Fourier)数值方法及椭偏测量,研究了高反射正弦形浅光栅的偏振特性.当正向入射条件下,光栅周期与波长之比满足某一关系时,其反射光电场的两垂直方向分量相移差大的特性,制成了一种新颖的双折射滤光片,文中给出了这种双折射滤光片的初步实验结果. 相似文献
11.
12.
Droplet deformation and alignment are achieved in holographic polymer-dispersed liquid-crystal reflection gratings by applying an in situ shear during recording. High diffraction efficiency (99%) is obtained for light polarized parallel to the shear, with nearly zero efficiency for perpendicular polarization, and no increase of incoherent scattering. Permanent polarization dependence is related to stress-induced morphology changes of liquid-crystal droplets that are frozen by polymerization. The system is studied by electron microscopy and modeled by anisotropic coupled-wave and scattering theory. The morphology is consistent with the theory of small deformations of liquid droplets in fluid flow. Diffraction efficiency measurements are in agreement with theory incorporating this morphology as well as concomitant orientation and alignment of liquid-crystal molecules. 相似文献
13.
The TE/TM polarization conversion characteristics of dielectric grating composed of left-handed materials for the case of
plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous
mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using
left-handed gratings. This can hardly achieve in the conventional right-handed gratings. Comparisons of polarization conversion
properties between right-handed gratings and left-handed gratings are given with physical explanations. This unique merit
of left-handed periodic structure is of important significance for accurate design of new millimeter wave TE/TM polarization
converters. 相似文献
14.
The diffraction properties of reflection volume holographic gratings are studied when the gratings are illuminated by an ultrashort beam with arbitrary temporal profiles. The modified Kogelnik's theory of coupled waves is used. Simple analytical expressions for spectral and temporal distribution of the transmitted and diffracted are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the reflection volume grating on the temporal profiles of the input ultrashort pulse are investigated. Study shows that the bandwidth of the reflection volume holographic gratings varies with the grating parameters more slowly than the transmitting volume holographic gratings. For three different temporal profiles, numerical results about diffraction properties of the reflection volume holographic gratings are given and compared with the transmitting volume holographic gratings. 相似文献
15.
F. Lagugné-Labarthet T. Buffeteau C. Sourisseau 《Applied physics. B, Lasers and optics》2002,74(2):129-137
The polarization properties of the optical set-up used for holographic recording of diffraction gratings on azopolymer thin
films are analyzed. The state of polarization of circularly polarized light is fully analyzed after reflection on a mirror
at various incidences (Lloyd-mirror set-up). The Stokes analysis is performed using a photopolarimeter and the phase shift,
the ellipticity and the azimuth orientation are compared with those calculated from Fresnel formulae. At large angles of incidence,
an initially right circularly polarized (RCP) beam becomes elliptically polarized with an azimuth of nearly +45°. From these
results, holographic diffraction gratings are recorded on an azobenzene-containing polymer thin film using (i) co- and contra-circularly
polarized beams and (ii) a right circularly polarized beam interfering with a +45° linearly polarized light beam. Using Jones-matrix
formalism, the polarization states of the diffracted orders from the birefringence (Δn) and the surface-relief (2Δd) gratings
are derived and compared with experimental measurements. Finally, the induced local birefringences and surface-relief amplitudes
are discussed in connection with atomic force microscopy measurements. The diffraction efficiencies obtained under the (+45°+RCP)
and (LCP + RCP) (where LCP = left circularly polarized) configurations are thus compared and discussed.
Received: 5 October 2001 / Revised version: 26 November 2001 / Published online: 17 January 2002 相似文献
16.
Highly efficient and functionalized polarization gratings have been recorded in azobenzene-containing mesogenic composites with twisted nematic cell configurations. The polarization gratings formed in azobenzene-containing mesogenic composites show a high diffraction efficiency of more than 45% and convert the polarization state of light at the same time. The polarization direction of the diffracted laser beams can be controlled by the twisted angle of the nematic cell. These characteristics of the polarization gratings are well explained by means of Jones calculus. 相似文献
17.
Control of reflectivity of a relief grating in a high-index film overlaid on a monomode glass waveguide was achieved by adjustment of the superstrate refractive index with liquids. Weak gratings reflecting at 1531 nm were inscribed by UV laser ablation. The grating reflectivity was measured as the ratio of the transmission outside the reflection band, at 1536 nm, to that at the Bragg wavelength. Reflectivity with an air superstrate was <0.3 dB for both polarizations. In the TE polarization the grating strength increased to 20.5 dB after application of a liquid of index 1.45. In the TM polarization the strength increased to 27 dB with a superstrate index of 1.50. Good agreement was found with a theoretical model based on beam propagation. 相似文献
18.
Yonggang Wu Zihuan Xia Zhenhua Wang Renchen Liu Pinglin Tang Gang Lv Heyun Wu 《Optics Communications》2012,285(12):2840-2845
A perpendicular dual-grating (PDG) guided-mode resonance filter was constructed by placing two identical waveguide gratings close to and their grooves perpendicular to each other. Multilayer waveguide theory was used to estimate the resonant wavelength for the TE and TM polarization incidences, and the rigorous coupled wave analysis (RCWA) was used to investigate the resonant wavelength, the lineshape and linewidth of the resonant peaks for arbitrary polarization incidences. The filter presents identical spectral characteristics for normally incident wave with arbitrary polarization. The separation of the resonant reflection peaks corresponding to the TE0 and TM0 split modes were realized by properly selecting the geometrical and material parameters of the grating layers and the waveguide layers. Measurement of the nano air gap between 0 and 0.4 p by determining one of the two resonant reflection peaks of the TE0/TM0 split modes was achieved without being interfered by the TM0/TE0 split modes. 相似文献
19.
We propose and demonstrate an efficient and simple wavelength switchable dual-wavelength passively mode-locked fiber ring
laser based on a semiconductor saturable absorber mirror (SESAM) and a cascaded sequence of fiber Bragg gratings (FBGs). The
efficient self-starting mode-locked operation was realized with a SESAM. Dual-wavelength pulses with a wavelength spacing
of 12.49 nm were obtained which was determined by the reflection peaks of the FBGs used in the experiment. In addition, by
rotating the polarization controllers (PCs), the switchable dual-wavelength operation was simply achieved via exploiting wavelength-dependent
loss mechanism. 相似文献
20.
The main conditions and parameters for obtaining surface relief total internal reflection diffraction gratings in conical mounting are presented. Calculated and experimental investigations reveal that there are ranges of grating periods, incidence angles, diffraction angles and gratings depths for which such gratings could be obtained, both for TE and TM polarizations. With optimized grating parameters the diffraction efficiency of the total internal reflection diffraction gratings can be greater than 90%. 相似文献