用计算机全息方法改变激光束横模的研究

以圆对称高斯光束变换为十字光束为例，提出一种全息光学元件的设计理论和方法，推导出计算机制全息图的衍射方程，同时给出设计结果的计算机模拟验证方法，动用ＨＯＥ可以解决光束能量转换效率及能量重新分配问题。     

Eu：Fe：LiNbO3晶体双光束耦合异常现象的研究

在Ｅｕ：Ｆｅ：ＬｉＮｂＯ３晶体的双光束耦合实验中，减小晶体厚度，增大泵浦光束直径，都可使指数增益系数和衍射效率增大，２θ角度响应范围加宽。升高温度亦可增大衍射效率。本文对上述实验结果进行了理论分析。     

稀土络合催化二氧化碳和环氧化物的共聚反应

以稀土络合体系ＲＥ（２０４）３－Ａｌ「Ｃｈ３ＣＨ（ＣＨ３）２」３（ＲＥ＝Ｙ,Ｎｄ,Ｐｒ,ＳＡｍ,Ｄｙ,Ｅｕ）;Ｐ２０４＝（ＲＯ）２ＰＯＯ－,Ｒ＝ＣＨ３（ＣＨ２）３ＣＨ（Ｃ２Ｈ５）ＣＨ２－催化二氧化碳（ＣＯ２）与环氧氯丙烷（ＥＣＨ）无规共聚、合成高分子量的新型聚碳酸酯。同时利用此催化体系对ＣＯ２、ＥＣＨ、环氧树脂（ＥＰ（６１８））进行三元共聚,采用元素分析、红外光谱、广角Ｘ射线衍射及热重分析（ＴＧ）     

用PECVD技术淀积PbTiO3薄膜

采用ＰＥＣＶＤ技术，以Ｐｂ（Ｃ２Ｈ５）、ＨｉＣｌ４和Ｏ２为反应源，在１７０℃温度下沉积了ＰｂＴｉＯ３功能薄膜，分别对薄膜进行了Ｘ射线荧光光谱、Ｘ光电子能谱、Ｘ射线衍射光谱和扫描电镜的化学组成及形貌等分析。     

紫外线辐照对HDPE结晶结构及化学结构的影响

采用ＤＳＣ、ＷＡＸＤ、元素分析、ＦＴ－ＩＲ、ＥＳＣＡ、ＧＰＣ、交联度和密度测定，研究了紫外线辐照了ＨＤＰＥ的结晶结构及化学结构变化。结果表明，紫外线辐照后，ＨＤＰＥ的熔融温度降低、熔融热焓升高、结晶度增大、晶胞结构未发生变化；ＨＤＰＥ分子甸主了ＣＯＯＨ、Ｃ＝Ｏ、Ｃ－Ｏ、ＯＯＨ、ＯＨ等含氧官能团，分子量降低，分子量分布加宽，基本无交联发生。     

紫外线辐照HDPE／PA6共混物界面相互作用的研究

采用ＥＳＣＡ、Ｍｏｌａｕ实验、ＳＥＭ、ＤＳＣ、ＤＭＡ、抽滤分析、ＦＴ－ＩＲ和拉抻应力－应弯曲线，研究了紫外线辐照ＨＤＰＥ／ＰＡ６共混物的界面相互作用机理。结果表明，紫外线辐照下，ＨＤＰＥ分子链上引入Ｃ＝Ｏ、ＣＯＯＨ、－ＯＨ、－ＯＯＨ、－Ｃ－Ｏ－等极性基因；在与ＰＡ６熔融共混过程中， 的Ｃ＝Ｏ、ＣＯＯＨ等基团与ＰＡ６分子我寂的酰胺基或端胺基发生化学反应，生成ＨＤＰＥ－ＰＡ６共聚物。共聚物的形成增强了     

含氮聚硅氧烷配位体及其Cu^2＋络合物的介电性能

研究了ｎ－β（氨乙基）－γ（氨丙基）三乙氧基硅烷（ＮＨ２（ＣＨ２）２ＮＨ（ＣＨ２）３Ｓｉ（ＯＥｔ）３）与二甲基二乙氧基硅烷（ＣＨ３）２Ｓｉ（ＯＥｔ）２）共水解，制备含（ＣＨ２）３ＮＨ（ＣＨ２）２ＮＨ２功能基的聚硅氧烷配位体，用ＩＲ，＾１ＨＮＭＲ和元素分析法对水解产物分析证明，ＮＨ２（ＣＨ２）２ＮＨ（ＣＨ２）３Ｓｉ（ＯＥｔ）３与（ＣＨ３）２Ｓｉ（ＯＥｔ）２进行了共水解反应，而且水解程度随ＮＨ２（ＣＨ     

电子束辐照对HDPE及其与Mg(OH)_2共混体系力学性能影响的研究EI

研究了高密度聚乙烯（ＨＤＰＥ）经电子束辐照后性能的变化，与Ｍｇ（ＯＨ）２的相容性，以及ＨＤＰＥ／Ｍｇ（ＯＨ）２共混体系的力学性能。实验结果表明，经电子束辐照后，ＨＤＰＥ分子被引入了极性基团（羰基），增加了ＨＤＰＥ与Ｍｇ（ＯＨ）２的相容性，使ＨＤＰＥ／Ｍｇ（ＯＨ）２体系的拉伸强度得到提高。     

电子束辐照对HDPE及其与Mg(OH)_2共混体系力学性能影响的研究

研究了高密度聚乙烯（ＨＤＰＥ）经电子束辐照后性能的变化，与Ｍｇ（ＯＨ）２的相容性，以及ＨＤＰＥ／Ｍｇ（ＯＨ）２共混体系的力学性能。实验结果表明，经电子束辐照后，ＨＤＰＥ分子被引入了极性基团（羰基），增加了ＨＤＰＥ与Ｍｇ（ＯＨ）２的相容性，使ＨＤＰＥ／Ｍｇ（ＯＨ）２体系的拉伸强度得到提高。     

制备SnO2薄膜时原料中水对其成膜和光电性质的影响

用无水ＳｎＣｌ４和ＳｎＣｌ４．５Ｈ２Ｏ为原料，用热喷涂法制备ＳｎＯ２薄膜，在基片温度为５３０℃时，对所制得ＳｎＯ２薄膜进行了Ｘ－射线，ＳＥＭ分析，并对其发电性质进行测定，总结出含Ｈ２Ｏ的ＳｎＣｌ４制得的ＳｎＯ２薄膜生长速度快，电阻率低。     

Holographic polarization-separation elements

Volume holographic optical elements exhibit a property that we call bidiffringence, in which the diffraction efficiency of the element is strongly dependent on the polarization of the incident beam. Dualelement, volume holographic polarization separators utilizing bidiffringence can provide high extinction ratios, and they can provide greater angular separation of the polarized beams and greater flexibility in the beam-separation parameters than conventional birefringent elements. We designed and constructed holographic polarization separators using dichromated gelatin as the holographic medium. Experimental results are compared with the results predicted by the Kogelnik coupled wave theory.     

Holographic parabolic mirror as a receiver optical front end for wireless infrared communications: experimental study

The inherent multifunctionality of holographic optical elements and their light physical weight make them an attractive solution for the receiver optics of portable terminals in indoor infrared wireless communication systems. A parabolic holographic mirror has been recorded in silver halide at a visible wavelength, and its replay wavelength has been shifted to the near infrared. Employment of proprietary swelling technology resulted in a permanent replay wavelength shift without the need for hologram sealing. Despite the relatively low diffraction efficiency of holograms recorded in silver halide in principle, an improvement in the receiver signal-to-noise ratio of more than 20 dB has been measured. The results of the conducted experiments proved undoubtedly the great potential of curved holographic mirrors as a key element of the receiver optical front end in IR wireless communication systems.     

Optical Processing of Bubble Chamber Photographs

Purely optical methods of spatial pulse width coding for coherent optical densitometry are described. The proposed coding scheme correlates the image intensity with the orientation of one edge of triangular or trapezoidal pulses. One encoding technique employs a contact screen similar to those used for half-tone printing. The image to be coded is copied through this contact screen onto hard-limiting film. This method is limited to the encoding of images with density distributions varying only slowly across the area of one pulse. A holographic encoding technique overcomes these drawbacks, utilizing the storage redundancy of holograms recorded with diffuse object beams. An array of identical holograms is reconstructed with a beam spatially modulated by the image transparency to be encoded. The array of reconstructed real images is recorded on hard-limiting film and renders a pulse-modulated version of the original image. The limiting conditions for the pulse size and the size of details in the image imposed by diffraction effects and speckle pattern are derived.     

Diffraction of optical communication Gaussian beams by volume gratings: comparison of simulations and experimental results

The diffraction effects induced by a thick holographic grating on the propagation of a finite Gaussian beam are theoretically analyzed by means of the coupled-wave theory and the beam propagation method. Distortion of the transmitted and diffracted beams is simulated as a function of the grating parameters. Theoretical results are verified by experimentation realized by use of LiNbO3 volume gratings read out by a 1550-nm Gaussian beam, typical of optical fiber communications. This analysis can be implemented as a useful tool to aid with the design of volume grating-based devices employed in optical communications.     

Formation of anisotropic diffraction gratings in a polymer-dispersed liquid crystal by polarization modulation using a spatial light modulator

Anisotropic diffraction gratings based on a holographic polymer-dispersed liquid crystal (HPDLC) are realized by interferometric exposure using a spatial light modulator (SLM). The SLM is used in the HPDLC grating formation for anisotropic holographic recordings of two-dimensional polarization states for an incident light beam. The diffraction efficiency for P-polarization and the distinctive ratio of diffraction efficiency in P-polarization to that in S-polarization increases with the signal level applied to the SLM. The resulting volume gratings exhibit diffraction efficiency of more than 60% and a distinctive ratio of diffraction over 100. The microscopic origin of the anisotropic property is investigated by an optical polarizing microscope. The novel characteristics of the anisotropic diffraction properties of HPDLC are applied to an image reconstruction technique.     

Spatio-temporal operator formalism for holographic recording and diffraction in a photorefractive-based true-time-delay phased-array processor

We present a spatio-temporal operator formalism and beam propagation simulations that describe the broadband efficient adaptive method for a true-time-delay array processing (BEAMTAP) algorithm for an optical beamformer by use of a photorefractive crystal. The optical system consists of a tapped-delay line implemented with an acoustooptic Bragg cell, an accumulating scrolling time-delay detector achieved with a traveling-fringes detector, and a photorefractive crystal to store the adaptive spatio-temporal weights as volume holographic gratings. In this analysis, linear shift-invariant integral operators are used to describe the propagation, interference, grating accumulation, and volume holographic diffraction of the spatio-temporally modulated optical fields in the system to compute the adaptive array processing operation. In addition, it is shown that the random fluctuation in time and phase delays of the optically modulated and transmitted array signals produced by fiber perturbations (temperature fluctuations, vibrations, or bending) are dynamically compensated for through the process of holographic wavefront reconstruction as a byproduct of the adaptive beam-forming and jammer-excision operation. The complexity of the cascaded spatial-temporal integrals describing the holographic formation, and subsequent readout processes, is shown to collapse to a simple imaging condition through standard operator manipulation. We also present spatio-temporal beam propagation simulation results as an illustrative demonstration of our analysis and the operation of a BEAMTAP beamformer.     

Application of holographic diffractive doublets as collimators for highly elliptical light beams edge emitted from diode lasers

Two schemes for collimation of diode laser light beams with high cross-sectional ellipticity by means of a doublet of holographic diffractive elements are proposed and designed; one of the schemes is realized and tested. In both the schemes the first element of the doublet collimates the beam in the plane of the longer axis of the ellipse, and the second element collimates it in the perpendicular plane. Each element simulates a cylindrical lens. The set-up with the focal line of the cylindrical beam oriented perpendicular to the meridional plane is realized experimentally. The elements are holographic surface-relief gratings recorded in photoresist. For recording, only homocentric diverging beams are used, which minimizes potential aberrations and optical dirt. The parameters of the elements are computed using four equations, including one equation for compensation of the aberration of the lowest order. The doublet is proposed for the He—Ne red wavelength. A collimated He—Ne laser beam is employed for quality testing of collimation in a reverse way, with this beam impinging upon the second element. Characteristics of an outgoing beam from the first element of the doublet are recorded with a charge-coupled device camera. Calculated spot diagrams are compared with cylindrical focal lines captured separately from both the elements.     

Visual method of measuring reflection-type characteristics of holographic optical elements

A highly diverging laser beam is used to measure angular and spectral selectivities and grating vector direction for reflection-type holographic optical elements (HOE's). The intensity distribution of the beam transmitted from the HOE's reveals dark, ring-shaped patterns. Since these ring patterns are formed as a result of the beam diffracted by the HOE's, the thicknesses and the diameters of the ring patterns convey information on both the angular and the spectral selectivities of the HOE's. In addition the deviation of the ring centers relative to the center of the intensity distribution reveals the grating vector direction. Determination of values related to the ring patterns permits highly accurate measurement of HOE characteristics, such as the upper limit of the diffraction wavelength, the angular and the spectral selectivities, and the grating vector direction. This is proved experimentally.     

Propagation of a decentered elliptical Gaussian beam through apertured aligned and misaligned paraxial optical systems

By expanding the hard aperture function into a finite sum of complex Gaussian functions, approximate analytical formulas for a decentered Gaussian beam (DEGB) passing through apertured aligned and misaligned paraxial apertured paraxial optical systems are derived in terms of a tensor method. The results obtained by using the approximate analytical expression are in good agreement with those obtained by using the numerical integral calculation. Furthermore, approximate analytical formulas for a decentered elliptical Hermite-Gaussian beam (DEHGB) through apertured paraxial optical systems are derived. As an application example, approximate analytical formulas for a decentered elliptical flattened Gaussian beam through apertured paraxial optical systems are derived. Our results provide a convenient way for studying the propagation and transformation of a DEGB and a DEHGB through apertured paraxial optical systems.     

Comparison of diffraction efficiencies for single-exposure and unity-contrast multiple-exposure holograms

The diffraction efficiency for a single-exposure holographic recording is compared with that of a multiple-exposure hologram recorded with maximum signal-to-bias ratio. For the multiple-exposure recording the object is illuminated point by point, and the reference wave amplitude for each subexposure is adjusted to produce a unity-contrast interferogram in the holographic recording plane. It is shown that, for the same M-point object and the same average exposure, the ratio of the single-exposure diffraction efficiency to the mulitple-exposure diffraction efficiency is proportional to M/R, where R is the reference-to-object beam ratio in the single-exposure case. This result is compared with that obtained in the multiple-exposure case when the reference wave amplitude assumes a constant value. Application areas include optical interconnects, holographic data storage, and volumetric multiplexed holograms for display.