各向异性泄漏模式调制器用于Holovideo的表征
Summary
This work describes fabrication and characterization of anisotropic leaky mode modulators for holographic video.
Abstract
Holovideo displays are based on light-bending spatial light modulators. One such spatial light modulator is the anisotropic leaky mode modulator. This modulator is particularly well suited for holographic video experimentation as it is relatively simple and inexpensive to fabricate1-3. Some additional advantages of leaky mode devices include: large aggregate bandwidth, polarization separation of signal light from noise, large angular deflection and frequency control of color1. In order to realize these advantages, it is necessary to be able to adequately characterize these devices as their operation is strongly dependent on waveguide and transducer parameters4. To characterize the modulators, the authors use a commercial prism coupler as well as a custom characterization apparatus to identify guided modes, calculate waveguide thickness and finally to map the device’s frequency input and angular output of leaky mode modulators. This work gives a detailed description of the measurement and characterization of leaky mode modulators suitable for full-color holographic video.
Introduction
最全息显示技术，诸如像素化光阀以及MEMS器件和体波的声光调制器，过于复杂，以允许在其发展广泛参与。像素化调节剂，尤其是那些具有滤光层和有源背平面，可能需要几十图案形成步骤以生成5，并且可以通过扇出6的限制。图案形成步骤的数量越大越高设备的复杂性，以及更严格的制造协议必须要达到合理的器件产率7。体波声光调制器不适合自己在片基础的过程8,9。各向异性泄漏模式调制器，然而，仅需要两个构图步骤来制作和使用相对标准的微细加工技术10,11。这些方法的可访问性有可能使用温和的制造设施的任何机构参与h的发展olographic视频显示技术的12。
器件制造的简易性可以是诱人的，但是，由于该设备的正常功能是强烈地依赖于它必须仔细地测量和调整，以实现期望的器件特性的波导。例如，如果波导太深，该设备的操作带宽将会缩小13。如果该波导太浅，该设备可能无法对红色照明工作。如果波导退火时间过长，波导的深度轮廓的形状会失真，并且红色，绿色和蓝色的转换可以不坐在频域中14相邻。在这项工作中作者提出的工具和技术来执行此鉴定。
泄漏模式调制器由一个质子交换波导indiffused压电的表面上，X切割的铌酸锂基片15,16。在一端的波导是铝叉指换能器， 见图1。光被引入到使用棱镜耦合器17的波导。该换能器然后启动表面声波随光中沿着y轴的波导contralinearly交互。这引导光线进入该泄漏出波导进入批量，最后退出从边缘衬底的泄漏模式的互动夫妇面对18,19。这种相互作用也从旋转偏振TE引导光的偏振极化TM泄露模式的光。表面声波模式的全息图，并且它是能够扫描和整形的输出光，以形成全息图象的。
波导是由质子交换创建。首先，铝被沉积在衬底上。然后铝被图案化光致光刻和蚀刻以暴露所述衬底的区域成为波导通道。剩余的铝用作硬面具。的基板浸渍在苯甲酸的熔融从而改变在曝光区域的表面折射率。该装置被移除，清洗和在马弗炉中退火。波导的最终深度决定漏模的转换次数。波导深度还确定每个引导到模式转换的每种颜色4的频率。
铝换能器通过剥离形成。形成波导之后，电子束抗蚀剂被旋涂在衬底上。一个叉指式换能器被用电子束图案，以形成一个线性调频传感器旨在到负责控制在波导器件色200 MHz频段响应。手指周期由Λƒ= v，其中，Λ，是指周期，V确定为声音在衬底的速度和，ƒ，是射频（RF）。该换能器将有必须匹配到75欧姆有效操作20的阻抗。
<P类=“jove_content”>该引导到漏模相互作用发生在用于照明的光的不同波长的不同的频率，因此红色，绿色和蓝色光可以在频域中进行控制。被发送到叉指式变换器的RF信号所产生的声表面波的图案。该输入信号的RF转换为在表面声波模式的空间频率。波导可被制造，使得低频信号控制红色光的角扫描和幅度，而中间频率控制绿光和高频控制蓝光。作者已经确定了一套波导的参数允许所有三种这些相互作用是在频域中分开和相邻的，使所有三种颜色可以与它的商品的图形处理单元的最大带宽（单个200MHz的信号来控制图形处理器）。由GPU信道的带宽匹配到一个漏模调制器，系统变得完全平行和高度可扩展的。通过增加带宽配对GPU和漏模式调制器的渠道，人们可以构造任意大小的全息显示器。
创建设备之后，它被小心地表征，以验证是否为引导到漏模过渡频率是适合于彩色的频率控制。首先，将引导模式的位置是由一个商业棱镜耦合确定为确认该波导具有适当的深度和引导模式的正确数量。然后，该装置被安装并包装后，它们被放置在定制棱镜耦合器映射扫描输出的光的输入频率。所得数据给出的频率输入响应和用于红色，绿色和蓝色光的器件进行测试的角的输出响应。如果设备已经正确制造，该装置输入响应将被分离频率和输出响应会在角重叠。当此确定后，该设备已准备好用于在全息视频显示器使用。
该设备已被打包前的第一次测量进行。波导深度是由商业棱镜耦合来确定。这可以只用一个照明波长来完成（一般632纳米红色），但作者已经修改了其商业棱镜耦合，以允许它收集为红色，绿色和蓝色光的模式信息。包装后，该装置经受一个定制棱镜耦合其中记录偏转输出光作为输入RF的功能的第二次测量。这些测量的详细说明如下。还给出制造步骤。
Protocol
Representative Results
Discussion
每个器件的设计有两个关键步骤，质子交换和LOR中的发展。两个的，质子交换时间决定了波导，这反过来又决定了引导到漏模的转换，可控频率带宽，以及用于光的每一种颜色的每个关键设计参数的数量的深度。在红二导模需要。如果有更多的存在，那么带宽牺牲。如果少存在，那么没有被引导到泄漏模式过渡的保证。按照步骤2.2.1的说明纠正质子交换倍，达到预期的效果。
…
Offenlegungen
The authors have nothing to disclose.
Acknowledgements
作者非常感谢来自空军研究实验室的合同FA8650-14-C-6571和DAQRI LLC的资金支持。
Materials
| X-Cut Lithium Niobate | Gooch and Housego | 99-00630-01 | Lithium Niobate 3″ Diameter X-CUT Wafer 1mm Polish/Polish |
| Positive Photo Resist 1 | EMD Performance Materials | AZ 3330 F Photoresist | Used in the creation of the proton exchange mask. |
| Photoresist Developer | EMD Performance Materials | AZ MIF 300 | Develops AZ3330 and LOR 3A |
| Aluminium | International Advanced Materials | AL13 | 99.999% Pure |
| Aluminium Etch | Transene | Type A Aluminum Etchant | |
| Benzoic Acid | Sigma Aldrich | 109479-500G | 99% Pure |
| Acetone | Fisher Chemical | UN1009 | |
| IPA | Fisher Chemical | UN1219 | 99.5% pure Isopropyl Alcohol |
| Acidic Piranha etch | Cyantek Corperation | Nanostrip | |
| Under Layer Resist | Micro Chem | LOR 3A | Bottom layer used for liftoff. |
| Positive Photo Resist | Micro Chem | 950 PMMA A9 | Top layer used for liftoff |
| Anisole | Micro Chem | A Thinner | |
| Conductive polymer aqueous solution | Mitsubishi Rayon Company | AquaSAVE | |
| MIBK (4-Methyl-2-pentanone) | Sigma Aldrich | 360511 | Develops PMMA |
| NMP (1-methyl-2-pyrrolidone) | Sigma Aldrich | 328634 | Used for liftoff |
| Name of the Equipment | Company | Catalog Number | Comments/ Description |
| E-beam Evaporator | Denton Vacuum | Integrity 20 | Any equivalent equipment would suffice. |
| Thin Film Spinner | Laurell Technologies Corporation | WS-400A-6NPP-LITE | Any equivalent equipment would suffice. |
| Mask Aligner | Karl Suss America Inc. | MA 150 CC | Any equivalent equipment would suffice. |
| Automatic Dicing Saw | Disco Corperation | Disco Dad 320 | Any equivalent equipment would suffice. |
| Muffle Furnace | Thermo Scientific | FB1415M | Any equivalent equipment would suffice. |
| Electron Microscope | FEI | XL30 ESEM | Any equivalent equipment would suffice. |
| Dehydration Oven | Lab-Line Instruments | Ultra-Clean 100 (3497M-3) | Any equivalent equipment would suffice. |
| Hot Plate | Thermo Scientific | SP131325 | Any equivalent equipment would suffice. |
| Polisher | Ultra Tec Mfg., Inc. | Ultrapol End & Edge Polisher | Any equivalent equipment would suffice. |
| Class IIIb 12V RBG Lasers: Wavelengths(nm): 638, 532, and 445 | Bought second-hand. Probably pulled from a laser projector. Any equivalent equipment would suffice. | ||
| Signal Generator | Agilent | 8648D | Now found at Keysight. Obsolete. Any equivalent equipment would suffice. Needed Frequency sweep 9 KHz-1000 MHz. |
| Signal Amplifier | Mini-Circuits | TB-17 | Necessary only to overcome the limitations of the signal generator. |
| Power Meter Controller | ThorLabs | PM100D | With power meter model S130C. Any equivalent equipment would suffice. Needed sensitivity 500pW |
| Linear Actuator Controller | Newport | ESP7000 | With linear actuator model MFN25PP. Any equivalent equipment would suffice. Needs 0.1mm accuracy. |
| AutomatedDeviceCharacterization.vi | LabView | Experimental Control Software by BYU | Found in the appendix |
| CompareWDMmodes.m | MATLab | Analytical Software by BYU | Found in the appendix |
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