新型5×5分束达曼光栅的设计与制作北大核心

基于理论设计了一种面内旋转对称的新型5×5分束达曼光栅,研究并优化了光栅制作中曝光、显影及深刻蚀等关键工艺参数。采用接触式曝光和感应耦合等离子体（ICP）刻蚀技术,在石英基底上制作出达曼光栅结构。实验中通过优化石英基底上接触式曝光时间和显影时间,较好控制了曝光图形失真;进一步通过控制ICP刻蚀工艺参数,获得了刻蚀深度为（750±10）nm的石英衬底,实现了达曼光栅器件的制备。通过衍射光学特性评测得到了理论设计的零级衍射场均匀分布的5×5点阵,总的衍射效率达到53%,不均匀性仅为0.19%。实验证明了理论设计与工艺技术的可靠性,为达曼光栅器件的集成光学系统应用奠定基础。     

感应耦合等离子体技术用于熔融石英表面凹凸光栅的刻蚀

感应耦合等离子体(ICP)刻蚀技术是一种新的干法刻蚀技术,具有刻蚀速率高和各向异性刻蚀等优点,并且能够独立控制等离子体密度和自偏置电压。然而,在利用这种技术进行刻蚀的过程中,经常会发生聚合物的沉积,从而阻碍了刻蚀过程的继续。我们报道了在熔融石英表面刻蚀光栅时不产生聚合物沉积的技术,给出了优化参数。所制作的熔融石英普通光栅和600线／mm的高密度光栅的表面很干净,没有聚合物沉积。光栅衍射效率的实际测量值和预期的理论值吻合得很好。最后还研究了ICP技术的刻蚀速度,刻蚀均匀性和过程可重复性等参数。     

上海光机所首次采用石英玻璃研制出高性能偏振分光器

上海光机所周常河课题组最近利用高密度等离子体刻蚀设备、半导体光刻工艺技术和激光全息技术，发展出石英玻璃深刻蚀技术，成功地在石英玻璃基底上加工出优化深度的亚波长光栅，实验证明其具有很高的偏振隔离度和衍射效率，是非常优良的偏振分光器件。     

感应耦合等离子休技术用于熔融石英表面凹凸光栅的刻蚀

感应耦合等离子体(ICP)刻蚀技术是一种新的干法刻蚀技术，具有刻蚀速率高和各向异性刻蚀等优点，并且能够独立控制等离子体密度和自偏置电压。然而，在利用这种技术进行刻蚀的过程中，经常会发生聚合物的沉积，从而阻碍了刻蚀过程的继续。我们报道了在熔融石英表面刻蚀光栅时不产生聚合物沉积的技术，给出了优化参数。所制作的熔融石英普通光栅和600线／mm的高密度光栅的表面很干净，没有聚合物沉积。光栅衍射效率的实际测量值和预期的理论值吻合得很好。最后还研究了ICP技术的刻蚀速度．刻蚀均匀性和过程可重复性等参数。     

80 mm×80 mm衍射光栅零级衍射效率实验研究

研制了一种用于激光惯性约束聚变研究的衍射光栅。光栅的制作采用离子束刻蚀方法,光栅尺寸为80 mm×80 mm,工作周期为90μm,对1.053、0.527、0.351μm 3种波长的激光束进行谐波分离。利用YLF激光器系统对衍射光栅的性能参数进行测试,结果表明,衍射光栅对波长为0.351μm的三倍频激光束零级衍射效率为79.7%。     

基于多层抗蚀剂的GaAs基微纳光栅深刻蚀工艺

采用电子束光刻技术制备出了深刻蚀的GaAs基微纳光栅。针对电子束曝光过程中存在的由邻近效应引起的光栅结构图形失真和变形的问题,本课题组采用厚度较薄的PMMA A4抗蚀剂和SiO₂薄膜形成多层抗蚀剂来减小邻近效应,同时将SiO₂薄膜作为硬掩模,实现了高深宽比的光栅结构。此外,针对电感耦合等离子体刻蚀过程中光栅结构出现长草的现象,通过增强电感耦合等离子体的物理刻蚀机制,有效消除了结构底部的草状结构。扫描电镜测试结果显示：将100 nm厚SiO₂作为硬掩模,可以实现周期为1.00μm、占空比为0.45、刻蚀深度为1.02μm的光栅结构,该光栅结构具有陡直的侧壁形貌以及良好的周期性和均匀性。在该工艺条件下,电感耦合等离子体刻蚀工艺对SiO₂掩模的刻蚀选择比可达26.9∶1。最后,将该结构应用于分布式布拉格反射锥形半导体激光器中,获得了线宽为40 pm的激光输出。这表明,采用电子束光刻技术制备的光栅结构对半导体激光器具有很好的选模特性。     

适用于阵列波导光栅制作的厚SiO2陡直刻蚀技术

采用ICP-98型高密度等离子体刻蚀机进行了厚SiO2陡直刻蚀技术的研究,利用双层掩膜技术解决了"微掩膜现象"问题,刻蚀获得12.4μm的陡直SiO2光波导剖面,并将这一刻蚀技术用于阵列波导光栅的制作中.     

用于惯性约束聚变系统中的色分离光栅近场衍射研究

色分离光栅（CSG）是一种重要的谐波分离衍射光学元件，它的近场衍射调制可能导致其自身及其后续光学元件的激光诱导损伤。根据色分离光栅的实际制作过程建立了包含对位误差、占空比误差、刻蚀深度误差、塌边误差等多种制作误差的色分离光栅加工误差模型。并基于标量衍射理论，采用傅里叶分析方法，利用该模型推导得到了色分离光栅近场内光强分布公式，并针对惯性约束聚变（ICF）驱动器终端光学系统的色分离光栅进行了计算模拟，得出了近场调制随各种加rf：制作误差的变化关系。计算结果表明深度误差和塌边误差对光束近场调制订很大影响，对位误差相对影响较小，而相互影响更加严重。该色分离光栅近场分析和计算模拟方法也可用于其他衍射光学元件。     

玻璃变晶体的技术:偏振分束深刻蚀石英光栅

通过引入深刻蚀光栅结构,普通的石英玻璃可以表现出类似双折射晶体的偏振分光性能.这种深刻蚀光栅是一种亚波长光栅结构,仅存在两个衍射级次,通过光栅表面刻蚀深度的优化控制,实现不同偏振方向的光出射到不同衍射级次上,实现了偏振分光的功能.     

紫外激光刻蚀氧化锆陶瓷初步研究

描述了KrF准分子激光对氧化锆陶瓷的微刻蚀实验,研究了脉冲刻蚀深度与脉冲数的关系(刻蚀速率),刻蚀的槽的形貌,并进行了刻蚀小孔的初步研究,得到直径为40μm,深度为25μm的微孔矩阵。为KrF激光对该材料的加工提供实验数据。     

A pixellated grating array using photoelectrochemical etching on aGaAs waveguide

We have demonstrated and evaluated a grating array outcoupler fabricated by photoelectrochemical (PEC) etching, a manufacturable and practical approach for fabrication of grating-based III-V semiconductor waveguide devices. An array of submicron period gratings was etched into photolithographically delineated areas in a single PEC step. The fabricated devices are: 10-μm wide rib waveguides with 0.35-μm first-order outcoupling gratings; and 10-μm wide rib waveguides with 10 μm×10 μm pixellated areas of gratings. Device characterization demonstrates the effectiveness of outcoupling grating fabrication using PEC and that the pixellated grating outcoupler is an effective and simple means of generating an optical beam array     

64×64点阵达曼光栅的设计与实现

分析了偶数点阵达曼光栅的设计原理与特性。利用数值优化方法 ,获得了一组 6 4× 6 4点阵达曼光栅解。光栅模版用电子束制版法制成 ,其最细线宽为 2 .5 μm。用光刻法实现了这一位相光栅 ,并比较了不同位相光栅制作法的优缺点。原子力显微镜测得的光栅深度曲线与 6 4× 6 4点阵实验结果表明 ,此光栅结果接近理论值。     

248 nm KrF准分子激光零级抑制石英相位掩模器的研制

实验研制了针对波长２４８ｎｍＫｒＦ准分子激光的零级抑制石英相位掩模器。用双层掩蔽和图形转移技术，在双面抛光的石英基片上以ＣＨＦ３／Ｏ２为反应气体，用反应离子刻蚀技术制作了具有良好完整性、周期１．０８５μｍ的石英相位掩模器。实际测量表明其零级衍射效率被抑制到５．９７％。     

Recording of efficient high-order Bragg reflectors in opticalfibres by mask image projection and single pulse exposure with anexcimer laser

A technique using high resolution mask projection for creating efficient Bragg grating reflectors in optical fibres by single excimer laser pulse exposure is described. Using a deep UV projection system with a large image field size and micrometre resolution, gratings with periods between 1 and 6 μm have been recorded in Ge-doped fused silica fibres that produce high order Bragg reflections in the wavelength range 1.43-1.65 μm     

编码孔径光谱成像仪中凸面闪耀光栅的研制

针对一款基于DMD的光谱维编码Offner光谱成像仪对凸面闪耀光栅的性能要求,提出了一种凸面闪耀光栅的宏观-微观一体化优化设计方法,利用三维偏振光追迹算法有机融合了宏观层面的Offner光学系统设计与微观层面的凸面闪耀光栅槽型设计。介绍了编码孔径Offner光谱成像系统的组成和工作原理,并结合系统的使用要求设计了一款平均衍射效率为85.47%的中波红外凸面闪耀光栅。在此基础上,采用超精密单点金刚石车床成功制备了曲率半径为120 mm、周期为99.945 μm、闪耀角为1.1783°、槽深为1.834 μm的凸面闪耀光栅。测试结果表明,在3~5 μm光谱范围内,最大衍射效率为93.46%,平均衍射效率为84.29%,与理论设计值较为吻合,验证了凸面闪耀光栅设计方法的有效性。     

Femtosecond laser writing Bragg gratings in pure silica photonic crystal fibres

The fabrication of Bragg gratings in pure silica photonic crystal fibres using ultra-violet femtosecond laser radiation at 267 nm is reported. Gratings have been fabricated with a depth of up to 10 dB and an average index change of /spl Delta/n> 4/spl times/10/sup -4/. Thermal annealing investigations indicate that our grating type is not type II.     

利用动态相位掩膜板法制作光纤光栅

在相位掩膜板法光纤Bragg光栅(FBG)制作系统中,通过高精度陶瓷压电(PZT)促动器对相位掩膜板进行运动控制,实现对光栅折射率交流调制量和相位的任意调制,从而实现相移、切趾和啁啾等FBG的制作,从而提高FBG制作工艺的灵活性。     

Silicon thin‐film solar cells with rectangular‐shaped grating couplers

As an alternative to randomly textured transparent conductive oxides as front contact for thin‐film silicon solar cells the application of transparent grating couplers was studied. The grating couplers were prepared by sputtering of aluminium‐doped zinc oxide (ZnO) on glass substrate, a photolithography and a lift‐off process and were used as periodically textured substrates. The period size and groove depth of these transparent gratings were tuned independently from each other and varied between 1 and 4 μm and 100–600 nm. The optical properties of rectangular‐shaped gratings and the opto‐electronic behaviour of amorphous and microcrystalline silicon solar cells with integrated grating couplers as a function of the grating parameters (period size P and groove depth h_g) are presented. The optical properties of the gratings are discussed with respect to randomly textured substrates and the achieved solar cell results are compared with the opto‐electronic properties of solar cells deposited on untextured (flat) and randomly textured substrates. Copyright © 2005 John Wiley & Sons, Ltd.     

UV-Inscribed Optical Fiber Gratings in Mid-IR Range and Their Laser Applications

We have UV-inscribed fiber Bragg gratings (FBGs), long-period gratings (LPGs), and tilted fiber gratings (TFGs) into mid-IR 2m range using three common optical fiber grating fabrication techniques (two-beam holographic, phase mask, and point-by-point). The fabricated FBGs have been evaluated for thermal and strain response. It has been revealed that the FBG devices with responses in mid-IR range are much more sensitive to temperature than that in near-IR range. To explore the unique cladding mode coupling function, we have investigated the thermal and refractive index sensitivities of LPGs and identified that the coupled cladding modes in mid-IR range are also much more sensitive to temperature and surrounding medium refractive index change. The 45 tilted fiber gratings (45-TFGs) as polarizing devices in mid-IR have been investigated for their polarization extinction characteristics. As efficient reflection filters and in-cavity polarizers, the mid-IR FBGs and 45-TFGs have been employed in fiber laser cavity to realize multi-wavelength 2 m Tm-doped CW and mode locked fiber lasers, respectively.