Materials World Network: Quasi-Phase Matching in Non-Centrosymmetric Wide Band Gap Semiconductors.

技术摘要：在材料研究部的支持下，北卡罗来纳州立大学(NCSU)的宽带隙小组和斯洛文尼亚卢布尔雅那大学的量子光学小组建立了一个合作小组，以探索将非中心对称宽带隙半导体用作非线性光学材料的可行性。在这项工作中，AlGaN(AlGaN)将作为一种模型材料，用于研究这类半导体作为高质量准相位匹配结构在二次谐波(SHG)中的适用性。作为一种宽禁带半导体，这将允许倍频将可用的半导体激光器的波长转移到较短波长的范围，而在这些波长范围内没有注入激光器。原则上，它应该允许最短波长在紫蓝色区域的半导体激光器的输出倍频，并产生波长接近200 nm的紧凑、相干的深紫外光光源。这一国际合作旨在展示基于宽带隙氮化物的倍频的准相位匹配结构，并开发在UV光谱中有效的倍频的基本非线性光学概念，这在其他系统中是无法实现的。为了实现这一点，需要解决两个主要挑战：(1)证明AlGaN合金的周期性横向极性控制；(2)发展对这些结构的非线性光学特性的基本认识。NCSU的团队解决了第一个挑战，他们在III-氮化物的生长和极性控制方面的专业知识已经得到展示。卢布尔雅那大学的量子光学小组以其在利用不同材料的非线性光学特性方面的独特能力和专业知识解决了第二个挑战。周期性的AlGaN结构是用金属有机化学气相沉积生长和制备的，合金成分和结构几何形状的选择是基于卢布尔雅那小组的光学研究。非技术综述：基于氮化铝镓半导体的非线性光学器件可以为在电磁光谱的深紫外区产生激光提供广泛的载体，这是任何其他固态技术都无法达到的。这可以在医疗保健、生物防御以及其他商业和国防应用中找到用途。在深紫外光中使用光源将导致不同的化学和生物气溶胶的检测系统，从而在其他流出物中提供各种污染物的检测。总体而言，这项研究将导致材料将用于处理自然资源的保护和扩展的应用：(1)允许有效利用和传输电能，(2)通过使用紫外线发光二极管消毒获得清洁饮用水，以及(3)排放和其他流出物检测。此外，这一具有挑战性的项目将提供在北卡罗来纳州立大学和卢布尔雅那大学之间建立研究协作和学生交流的机会。这个机会也将帮助学生和研究人员接触到NCSU和卢布尔雅那大学实现这项研究的最先进的设施，同时建立一个为建立未来职业生涯而建立的国际网络。

TECHNICAL SUMMARY: With support from the Division of Materials Research, a collaboration between the Wide-Bandgaps group at North Carolina State University (NCSU) and the Quantum Optics group at the University of Ljubljana, Slovenia, has been established to explore the feasibility of using non-centrosymmetric wide bandgap semiconductors as nonlinear optical materials. In this work, AlGaN (aluminum gallium nitride) will serve as a model material for the investigation of the applicability of this semiconductor class as the high-quality quasi phase-matched structures for second harmonic generation (SHG). As a wide bandgap semiconductor, this will allow for SHG to shift the wavelength of available semiconductor lasers to the range of shorter wavelengths, where injection lasers are not available. In principle, it should allow for the frequency doubling of the output of a semiconductor laser with the shortest wavelength in the violet-blue region and produce a compact, coherent deep ultraviolet light source with wavelengths approaching 200 nm. This international collaboration seeks to demonstrate quasi-phase matched structures for SHG based on wide bandgap nitrides and to develop fundamental nonlinear optical concepts for efficient SHG in the UV spectrum that cannot be achieved in other systems. In order to realize this, two main challenges need to be met: (1) the demonstration of periodic lateral polarity control in AlGaN alloys, and (2) the development of the basic understanding of nonlinear optical characteristics of these structures. The group at NCSU addresses the first challenge, where their expertise in growth and control of polarity in III-nitrides has been demonstrated. The Quantum Optics group at the University of Ljubljana addresses the second challenge with their unique capabilities and expertise in harnessing non-linear optical properties of different materials. The periodic AlGaN structures are grown and fabricated using metalorganic chemical vapor deposition, with the choice of alloy composition and structure geometry based on the optical research by the group at Ljubljana. NON-TECHNICAL SUMMARY: Nonlinear optical devices based on the aluminum gallium nitride semiconductors can provide a broad-based vehicle for laser light generation in the deep ultraviolet region of the electromagnetic spectrum, which is not accessible by any other solid-state technology. This can find uses in health care, bio-defense and other commercial and defense applications. The use of light sources in the deep UV will lead to detection systems of different chemical and biological aerosols, providing for detection of a variety of pollutant agents among other effluents. In general, this research will lead to materials that will be used for applications that deal with the preservation and extension of natural resources by: (1) allowing for the efficient use and transmission of electrical energy, (2) availability of clean potable water through disinfection by the use of UV light emitting diodes, and (3) emissions and other effluents detection. In addition, this challenging project will provide the opportunity to establish a research collaboration and student exchange between North Carolina State University and the University of Ljubljana. This opportunity will also help expose the students and researchers to state of the art facilities within NCSU and the University of Ljubljana for realizing this research, while at the same time building an international network for establishing future careers.