Gray Scale Lithography Technology for Asymmetric Resonant Cavities of Micro - and Meso-Scale Lasers, Amplifiers and Filters

0000170 LeePI和他的团队将研究通过灰度光刻制造的新型光子器件，该器件利用了一种称为非对称谐振腔（ARC）的新型光学谐振微腔。 ARC是一种基于全（或部分）内反射的紧凑辩证微腔，其已被证明支持高Q模式，以高方向性发射并且（在半导体中红外激光器的情况下）具有高输出功率。 ARC的概念是基于圆柱形或球形回音壁谐振器的平滑椭圆变形。 在下面提出的工作之前，在开发ARC基器件中仅有限地使用了复杂的现代光刻技术，这需要亚微米精度和良好控制的高度轮廓。 他们将研究以玻璃、掺铒玻璃、砷化镓、InGaAs/GaAlAs和硅/锗为基础的ARC，并利用新开发的灰度光刻技术，进一步展示ARC在介观光学器件中的有用特性。 具体而言，他们希望测试和演示以下重要功能：改善ARC微激光器在宽波段和增益材料范围内的激射特性。ARC微激光器从两种不同的模式激射发射的可能性，即发射方向性和波长都不同。证明ARC基光放大器的类似特性。由于与ARC的非倏逝波耦合，改善了波导和ARC微谐振器之间的输入-输出耦合，从而大大改善了设计容差。演示如何利用ARC谐振的独特方向特性进行对波分有用的滤波操作平面集成光学中的多路复用（WDM）应用。演示将平面传播或发射转换为垂直于平面传播或发射的器件配置。 提出的新方案是带有辅助中反射器的ARC，或轴锥圆顶ARCS。 这些配置基本上依赖于灰度光刻的独特功能。光刻可以应用于定义横向形状，但曝光控制将定义表面轮廓。 UCSD将开发两种互补的制造方法。 一种是基于用于高度轮廓为5微米的ARC的干法蚀刻，另一种是基于用于轮廓为5微米的Sandia的LIGA铸造工艺。 这两种方法都将采用灰度光刻，这是加州大学圣地亚哥分校的先驱，它是上级优于二元光刻生产更高质量和更低成本的光学元件。 然而，灰度级技术必须通过在灰度级掩模上采用更厚的类金刚石涂层以用于更宽的曝光动态范围和更厚的模拟光致抗蚀剂层来修改。 桑迪亚的LIGA工艺现在只适用于二进制光刻;但他们已经同意与我们合作，将灰度光刻引入他们的LIGA工艺。 此外，Sandia迄今为止只生产PMMA，金属和陶瓷的LIGA部件，而ARC的首选材料是玻璃，硅和锗。 设计、生产和测试任意3D形状的细观光学器件的令人兴奋的可能性，可以通过灰度技术实现。 灰度技术在桑迪亚LIGA铸造工艺中的应用以及用于重定向ARC发射的介观光学是全新的。这是UCSD和耶鲁大学之间的合作项目。 Yale（ADS和RKC）将负责确定待制造ARC的形状、尺寸和材料。 UCSD（SHL）将负责ARC的制作和样品检查。 耶鲁大学（RKC）将测量制造的ARC的性能，并向耶鲁大学设计小组和UCSD的制造小组提供反馈，同时专注于集成光学领域和电信领域WDM部分的可能应用。

0000170LeeThe PI and his group will study novel photonic devices fabricated by gray-scale lithography which exploit a new type of optical resonant micro-cavity known as an Asymmetric Resonant Cavity (ARC). The ARC is a compact dialectic micro-cavity based on total (or partial) internal reflection which has been shown to support high-Q modes, emit with high directionality and (in the case of semiconductor mid-infrared lasers) with high output power. The ARC concept is based on smooth oval deformations of cylindrical or spherical whispering gallery resonators. Prior to the work proposed below, only limited use has been made of sophisticated modem lithographic techniques in developing the ARC-based devices, which require sub-micron accuracy and well-controlled height profiles. They will investigate ARCs based on glass, Er-doped glass, GaAs, InGaAs/GaAlAs and silicon/germanium.The proposed project will demonstrate further useful properties of ARCs for meso-optical devices, by employing the newly developed gray scale lithography. Specifically they hope to test and demonstrate the following important features:Improved lasing characteristics of ARC micro-lasers over a wide range of wavelength bands and gain materials.The possibility of lasing emission from ARC micro-lasers from two qualitatively different modes, i.e. different in both emission directionality and wavelength.Demonstrate similar properties for ARC-based optical amplifiers.Improved input-output coupling between waveguides and ARC micro-resonators due to nonevanescent coupling to ARCS, resulting in much improved design tolerances.Demonstrate how to exploit unique directional properties of ARC resonances for filtering operations useful for wavelength division multiplexing (WDM) applications in planar integrated optics.Demonstrate device configurations which convert planar propagation or emission to propagation or emission perpendicular to the plane. Configurations proposed are ARCs with auxiliary mesoreflectors, or axicon-domed ARCS. These configurations rely essentially on unique features of gray-scale lithography.Lithography can be applied to define lateral shapes, but exposure control will define the surface profiles. UCSD will develop two complimentary fabrication methods. One is based on dry etching for ARCs of height profiles 5 microns and another on Sandia's LIGA foundry process for profiles 5 microns. Both methods will employ gray scale lithography, which UCSD pioneered, and which is superior to binary lithography for producing higher quality and lower cost optical components. However, the gray scale technology must be modified by employing thicker diamond-like-coatings on the gray scale masks for wider dynamic ranges of exposure, and thicker analog photoresist layers. The LIGA process at Sandia now works only with binary lithography; but they have agreed to work with us to introduce gray scale lithography into their LIGA process. Moreover, Sandia has produced LIGA parts only in PMMA, metals and ceramics to date, whereas the preferred materials for ARCs are glass, silicon and germanium. The exciting possibility of designing, producing and testing meso-optics of arbitrary 3D shapes, is within reach with gray-scale technology. Application of gray scale technology to Sandia's LIGA foundry process as well as meso-optics for redirecting ARC emission is totally new.This is a collaborative project between UCSD and Yale. Yale (ADS and RKC) will be responsible in defining the shapes, sizes and materials of ARCs to be fabricated. UCSD (SHL) will be responsible for the fabrication of ARCs and sample examination. Yale (RKC) will measure the fabricated ARCs in terms of their performance and provide feedback to the Yale design group and to the fabrication group at UCSD, while focusing on possible application to the integrated optics field and WDM part of the telecommunications field.***