基于MEMS闪耀光栅的波分复用器的研究

针对刻划光栅因周期误差和刻线的不平整所带来的鬼线和杂散光的不足和缺陷,提出了基于MEMS闪耀光栅的波分复用器的构成方法,介绍了基于MEMS闪耀光栅的波分复用器的基本组成,介绍了MEMS闪耀光栅的工艺实现以及提高其衍射效率的方案.在LabVIEW中对MEMS闪耀光栅进行了数值仿真分析,同时在ZEMAX中对波分复用器进行了光线追迹,其结果证明了MEMS闪耀光栅应用于波分复用器中的可行性.     

反应离子束刻蚀工艺制作闪耀罗兰光栅

相比类矩形槽罗兰光栅,闪耀罗兰光栅的衍射效率较高,更有利于光谱分析仪器的设计与应用,而国内外尚无产品级闪耀罗兰光栅产品.本文通过类矩形槽形及闪耀槽形的衍射效率优化设计及对比,获得了闪耀槽形优化设计结果;利用反应离子束刻蚀设备制作出3块200~450 nm波段、线密度为2 400 gr/mm、口径为Φ63.5 mm的闪耀罗兰光栅,其中光栅2的峰值衍射效率达到了65%@220 nm,较HORIBA Jobin Yvon公司生产的类矩形槽罗兰光栅产品整体衍射效率高25%,与理论衍射效率相当.实验结果表明,本文所采用的反应离子束刻蚀工艺可实现高衍射效率闪耀罗兰光栅制作,且工艺可控、稳定,所制作的闪耀罗兰光栅衍射效率高于国外同类产品.     

用于分频的闪耀光栅设计及衍射行为研究

详细地介绍了用于分频的闪耀光栅设计方法 ;推导了影响元件性能的衍射效率公式 ;并研究了纵横向工艺误差对其衍射行为的影响。模拟结果显示在 8%和 5%纵横向相对误差范围内 ,该闪耀光栅具有良好的分色效果。     

溶胶凝胶法制备闪耀光栅及特性研究

采用一步催化法，制备ZrO2光敏溶胶，用提拉法形成了单层光敏凝胶膜。采用紫外光刻技术，将掩摸图形转移到光敏凝胶膜上，通过曝光角度的控制，实现具有一定倾角的闪耀光栅制备，以紫外分光光度计，红外分光光度计，原子力显微镜等方法对光敏凝胶膜及光栅图形进行了性能测试及表征。并用355nm激光系统进行衍射效率及激光损伤阈值测定。获得了周期为2μm，高度为60nm，闪耀角为3°的闪耀光栅。     

自由空间的微闪耀光栅光开关

微光学元件在现代光学中具有重要的作用,通过制作8台阶的微闪耀光栅列阵,控制周期参数,利用其在空间的闪耀输出与级连,可以实现2×2、4×4以及8×8的光开关功能,光信号交换透明,无光电-电光转换过程。对微闪耀光栅输出信号的串扰分析表明,微闪耀光栅光开关可以有效的抑制串扰问题,在全光网络通信中具有一定的应用。     

集成光学头用的波导光栅耦合器的制作与性能研究

对集成光学头用的波导光栅器件的制作技术进行了研究。采用热氧化和离子束增强沉积方法分别在Si衬底上制备了SiO2层和玻璃波导层,制成了以Si为基底的光波导．采用PCVD法在该光波导上制备Si-N层,用全息干涉光刻法在Si-N层上制作了周期为1μm的等周期直线光栅,并用离子束刻蚀技术将该光栅转移到了Si-N层中。光栅的倾角约20～30°;一级衍射效率可达120％,具有明显的闪耀光栅特征。该光栅可用作导波光输入输出耦合器。     

光刻胶灰化用于全息离子束刻蚀光栅制作

针对全息离子束刻蚀衍射光栅制作中,光刻胶光栅浮雕图形的制作是至关重要和困难的,引入O2反应离子刻蚀对光刻胶光栅进行灰化处理,给出光刻胶灰化技术在全息离子束刻蚀衍射光栅制作闪耀光栅、浅槽矩形位相光栅、自支撑透射光栅中的具体应用。实验结果表明,这一新工艺的突出优点是降低了苛刻的全息曝光、显影要求,使得光栅线条光滑、线空比和槽深可控。     

新型反射式闪耀光栅楔形平板

提出并设计了一种新型光学元件——反射式闪耀光栅楔形平板。在玻璃楔形平板的倾斜表面上加工锯齿形闪耀光栅,在光栅的表面镀相应的金属反射膜,形成反射式闪耀光栅。当光线垂直楔形平板底面入射时,闪耀级次的衍射光可以沿入射方向返回,使该级次衍射光的能量得到充分利用,可以应用在在需要保持反射光线方向不变的场合。该元件兼具闪耀光栅和楔形平板的特性,通过实验对光线的能量和方向特性进行了验证,实验结果表明, 1级衍射光沿入射光线方向返回,并且能量的89.36%都集中在这一级上。转角测量的实验结果表明,该元件能使转角测量的范围扩大为0~360°以及大于360°的任意角度,转角测量的重复性精度可以达到0.632″。     

光刻胶灰化用于全息离子束刻蚀光栅制作

针对全息离子束刻蚀衍射光栅制作中，光刻胶光栅浮雕图形的制作是至关重要和困难的，引入伤反应离子刻蚀对光刻胶光栅进行灰化处理，给出光刻胶灰化技术在全息离子束刻蚀衍射光栅制作闪耀光栅、浅槽矩形位相光栅、自支撑透射光栅中的具体应用。实验结果表明，这一新工艺的突出优点是降低了苛刻的全息曝光、显影要求，使得光栅线条光滑、线空比和槽深可控。     

利用光栅闪耀特性优化低通滤波器

为了滤除有效光信号中的光噪声，本文提出了一种利用光栅的闪耀特性将噪声和有效信号之间的夹角角度差放大，再通过光阑得到有效光信号的方法。通过分析和仿真，使用光栅的1、2级闪耀对入射时微小角度差进行放大比较适宜。放大倍数会随着闪耀光栅的周期的减小而增大。负斜入射角度差的放大效果比正斜入射的效果更好。     

Fabrication and simulation of diffractive optical elements with superimposed antireflection subwavelength gratings

With the aim of reducing surface reflections and increasing the diffraction efficiency we investigated the superposition of subwavelength phase gratings onto blazed phase gratings. With direct-write electron-beam lithography bare blazed gratings and blazed gratings carrying subwavelength gratings were fabricated and their optical performances compared. For TE polarization the subwavelength-carrying gratings showed a maximum diffraction efficiency of 90.6%, whereas the corresponding maximum value for the bare grating was 86.3%. The experiment was simulated with rigorous diffraction theory.     

Mo/Si multilayer-coated ruled blazed gratings for the soft-x-ray region

Two Mo/Si multilayer-coated blazed gratings have been fabricated for operation at soft-x-ray wavelengths above the Si L edge, λ ≥ 12.4 nm, at (near) normal incidence. The sawtooth profile of the grating structure was mechanically ruled into a 200-nm Au film that was deposited onto a plane glass substrate. To smooth the rough Au surface and to prevent interdiffusion of the Au film with the upper Mo/Si multilayer, a carbon film was evaporated onto the Au grating surface of one of the gratings before the deposition of the multilayer coating. We matched the multilayer grating, working on blaze in the third diffraction order, in which an absolute diffraction efficiency of 3.4% at a wavelength of 14 nm was measured, whereas only 1.1% was achieved for a similar grating (without a carbon interlayer). These efficiencies are higher than those obtained for other ruled blazed gratings reported in the literature. As a result of the multilayer and grating periodicity, the wavelength of diffraction can be tuned bya rotation of the grating, which is important for application in a soft-x-ray monochromator.     

Extreme-ultraviolet efficiency measurements of freestanding transmission gratings

We report new, near-normal-incidence, transmission grating efficiency results at selected extreme-ultraviolet wavelengths between 4.5 and 30.5 nm for two transmission gratings, one with a period of 200 nm and the other with a period of 400 nm. These gratings consist of opaque gold bars separated by open spaces that have been produced by photolithography techniques commonly used to produce electronic components. The gold bars and the open spaces are nominally of the same width. Both gratings have a thickness of 470 nm. The transmission efficiency at the central, first, and, when possible, second order of diffraction was measured. In addition, guided-wave phenomena at nonnormal angles of incidence, as well as transmission differences depending on which side of the grating was illuminated, were investigated. The observed guided-wave effects allow one to selectively enhance the transmission of the grating at desired wavelengths, as is realized with a blazed reflection grating.     

Diffraction efficiency of 200-nm-period critical-angle transmission gratings in the soft x-ray and extreme ultraviolet wavelength bands

We report on measurements of the diffraction efficiency of 200-nm-period freestanding blazed transmission gratings for wavelengths in the 0.96 to 19.4 nm range. These critical-angle transmission (CAT) gratings achieve highly efficient blazing over a broad band via total external reflection off the sidewalls of smooth, tens of nanometer thin ultrahigh aspect-ratio silicon grating bars and thus combine the advantages of blazed x-ray reflection gratings with those of more conventional x-ray transmission gratings. Prototype gratings with maximum depths of 3.2 and 6 μm were investigated at two different blaze angles. In these initial CAT gratings the grating bars are monolithically connected to a cross support mesh that only leaves less than half of the grating area unobstructed. Because of our initial fabrication approach, the support mesh bars feature a strongly trapezoidal cross section that leads to varying CAT grating depths and partial absorption of diffracted orders. While theory predicts broadband absolute diffraction efficiencies as high as 60% for ideal CAT gratings without a support mesh, experimental results show efficiencies in the range of ～50-100% of theoretical predictions when taking the effects of the support mesh into account. Future minimization of the support mesh therefore promises broadband CAT grating absolute diffraction efficiencies of 50% or higher.     

Technique for detecting flaws in metallic surfaces using an optical system with phase-type blazed gratings

In this paper, we evaluate a novel flaw-detection technique for metallic surfaces based on the use of phase-type blazed gratings. Transparent blazed gratings were prepared by the soft nanoimprint method involving the transfer of a template (a reflective grating structure used for spectroscopy) onto silicone rubber. The blazed gratings were then integrated into an imaging system to observe the reflective metal sample. Due to the low-pass-filtering properties of the gratings, the captured image was notably blurred. This characteristic aids in flaw detection on metallic surfaces because the captured image is adequate to distinguish flaws in the targeted area on the basis of the texture of the rough surface, including any other structures that were unintended. The use of double-sided gratings with crossing grating vectors was found to be efficient for homogenous low-pass filtering. Such flaw-detection techniques are expected to be useful for conducting quality inspections of rolled steel plates since the surface contains both a rough surface and undesirable flaws.     

Diffraction based phase compensation method for phase-only liquid crystal on silicon devices in operation

A method to measure the optical response across the surface of a phase-only liquid crystal on silicon device using binary phase gratings is described together with a procedure to compensate its spatial optical phase variation. As a result, the residual power between zero and the minima of the first diffraction order for a binary grating can be reduced by more than 10 dB, from -15.98 dB to -26.29 dB. This phase compensation method is also shown to be useful in nonbinary cases. A reduction in the worst crosstalk by 5.32 dB can be achieved when quantized blazed gratings are used.     

Recording of concave diffraction gratings in counterpropagating beams using meniscus blanks

The most technological way of recording blazed concave holographic gratings is by using the direct- and back-reflected beams. Usually plano-concave blanks are used for diffraction grating fabrication. To compensate the refraction at the plane back surface of the blank, one has to use additional elements or two-step recording mountings. Another solution is to use diffraction grating blanks having zero optical power. A number of gratings with different groove frequencies have been fabricated using concave—convex blanks. The theoretical investigation of the aberration properties of the recording mountings, and the experimental study of the grating properties are discussed. Using the CODE V program it is shown that a significant reduction in the aberration size of the virtual recording source can be achieved by optimization of the radius of curvature of the blank back surface. The experimental results confirm the possibility of achieving gratings that can be used in flat-field spectrometers with a limit of resolution of about 2–3 nm even in the case where an aberrated virtual recording source is used.     

Gray-scale masks for diffractive-optics fabrication: I. Commercial slide imagers

Fabrication of diffractive optics with binary masks requires multiple photolithographic processes to produce high-efficiency elements. Alignment or etching errors at any stage of fabrication decrease the efficiency of the element. We developed an easily accessible procedure that reduces fabrication complexity and costs by using a single gray-scale mask. The gray-scale patterns are generated by commercial slide imagers and are then photoreduced onto low-contrast film plates. Multiple-level or continuous relief structures (kinoforms) may be constructed by use of the photoreduced gray-scale patterns as lithographic masks. Diffractive-optic lenses and blazed gratings were fabricated in photoresist with this procedure. First-order diffraction efficiencies as high as 85% were measured for the blazed gratings. The advantages and the limitations of this technique are discussed.     

Design of transmission blazed binary gratings for optical limiting with the form-birefringence theory

The structure of transmission blazed binary gratings for optical limiting is designed with the form-birefringence theory. This kind of grating has subwavelength features, can imitate the transmission blazed grating effectively, and has higher efficiencies than a transmission blazed grating with a subwavelength structure. The diffraction efficiencies are calculated and analyzed. For the normal incident light with 10.6 microm wavelength, the transmissivities for the designed grating at 0 degrees deviation angle for TE and TM polarizations are 0.05% and 5.09%, respectively, which are basically identical to the results of the finite-difference time-domain method. The diffraction efficiencies of the first transmitted order for TE and TM polarizations are 93.95% and 83.88%, respectively.