SBIR Phase I: Large Aperture, Periodically-Structured Gallium Arsenide for Infrared and THz Wavelength Conversion

这个小型企业创新研究(SBIR)第一阶段项目将研究新的光学键合技术，以生产周期性结构的砷化镓(GaAs)非线性晶体。在化学-生物传感、气候监测、医疗诊断、多光谱成像、激光光谱、太赫兹光谱和成像以及红外对抗等方面的应用都需要高功率、可广泛调谐的红外源。这种红外源通常是通过使用非线性晶体对高功率源进行波长转换而产生的。现有的红外波段晶体性能有限，影响了上述所有应用。与其他晶体相比，砷化镓被认为是一种优良的非线性材料，但它不能实现双折射位相匹配。为了实现波长转换，必须将砷化镓晶体加工成交替晶区层(准相位匹配，QPM)。虽然这些结构现在已经使用外延生长技术来制造-验证了QPM与GaAs的有效性-但这些方法可能永远不会生产出大功率应用所需的厘米大小的光学孔径。将对键合GaAs的界面损耗进行基础性研究，从而展示适合于高功率应用的多层、高强度、大口径结构。这项研究的结果将是对界面物理的详细物理理解，对制作结构的光机械表征，以及对基于晶片的商业生产的重要指导。该项目的更广泛的影响/商业潜力是以两种不同的方式提供具有科学、商业和社会价值的大口径非线性晶体。首先，将要研究的新的键合工艺是实现QPM GaAs中大口径波长转换器件功能的第一步。这种层状材料结构通常被称为工程非线性材料，周期极化的铌酸锂(PPLN)就是最著名的例子。PPLN已经在其红外波长转换区域(~2-5微米)取代了大多数其他非线性材料，并开启了一个多领域使用的市场，现在包括许多工程结构。周期性结构的砷化镓将把这些工程非线性材料的市场扩展到整个红外区域(~2-14微米)。其次，红外工程材料的生产将使目前难以进入、需要更高功率或在商业上不可行或不切实际的光谱区域进行新的科学研究。例如，保护我们的军队和国土免受化学和生物威胁的多光谱红外系统，比X射线更安全地询问隐藏结构(和人类)并可以探测武器和爆炸物的太赫兹系统，基础科学红外光谱研究，以及改进的医疗设备和诊断技术。

AbstractThis Small Business Innovation Research (SBIR) Phase I project will investigate novel optical bonding techniques to produce periodically-structured gallium arsenide (GaAs) nonlinear crystals. High-power, widely-tunable infrared sources are needed for applications in chemical-biological sensing, climate monitoring, medical diagnostics, multispectral imaging, laser spectroscopy, terahertz spectroscopy and imaging, and infrared countermeasures. Such infrared sources are typically created by wavelength conversion of a high-power source using a nonlinear crystal. Existing crystals for infrared bands are limited in their performance, compromising all the applications above. GaAs is recognized as a superior nonlinear material compared to other crystals, but it cannot be birefringently phase-matched. To enable wavelength conversion, GaAs crystals must be fabricated into layers of alternating crystal domains (quasi-phase-matching, QPM). While these structures have now been fabricated using epitaxial growth techniques - validating the usefulness of QPM with GaAs - those methods will likely never produce the cm-size optical apertures required for high-power applications. Fundamental studies of interfacial losses for bonded GaAs will be undertaken, leading to demonstrations of multi-layer, high-strength, large-aperture structures suitable for high-power applications. The results of this research will be detailed physical understanding of the interface physics, opto-mechanical characterization of the fabricated structures, and important guidance for wafer-based commercial production.The broader impact/commercial potential of this project is to provide large aperture GaAs nonlinear crystals that have scientific, commercial, and societal merit in two different ways. First, the novel bonding processes that will be investigated are the first steps to functional large-aperture wavelength conversion devices in QPM GaAs. Such layered material structures are generally referred to as 'engineered nonlinear materials', and Periodically-Poled Lithium Niobate (PPLN) is the most well-known example. PPLN has supplanted most other nonlinear materials in its infrared wavelength conversion region (~2-5um), and has initiated a multi-field-of-use market that now includes numerous engineered structures. Periodically-structured GaAs will extend these markets for engineered nonlinear materials across the entire infrared region (~2-14um). Second, the production of engineered infrared materials will enable new scientific investigations in spectral regions that are currently difficult to access, require higher power, or are otherwise commercially unfeasible or impractical. Examples include multispectral infrared systems to protect our military forces and homeland from chemical and biological threats, terahertz systems that can interrogate hidden structures (and humans) more safely than x-rays and can detect weapons and explosives, fundamental scientific infrared spectroscopic studies, and improved medical equipment and diagnostic techniques.