CAREER: Short-Wavelength Vertical-Cavity Surface-Emitting Laser Arrays Using Nonpolar and Semipolar GaN

职业：使用非极性和半极性 GaN 的短波长垂直腔表面发射激光阵列

• 批准号: 1454691
• 负责人: Daniel Feezell
• 金额: $ 50万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1454691&HistoricalAwards=false
• 关键词: CAREER; Short; Wavelength; Vertical; Cavity

The research objective of this Faculty Early Career Development (CAREER) Program award is to demonstrate the first short-wavelength (blue and green) vertical-cavity surface-emitting laser (VCSEL) arrays with stable and predictable light polarization. The approach will use an innovative fabrication process to address issues with GaN-based materials that have previously limited the output power, wavelength range, and functionality of short-wavelength VCSELs. Fundamental challenges that have prevented systematic control of light polarization in VCSELs will be overcome with novel materials growth processes. The realization of short-wavelength VCSELs with stable and predictable light polarization will enable unique applications in high-density optical data storage, high-resolution printing, lighting, displays, projectors, miniature atomic clocks, and chemical/biological sensing that are not easily accomplished with conventional edge-emitting lasers. To address a variety of polarization-sensitive applications that require higher-power light emitters, the devices will be formed into polarization-pinned arrays. The educational and outreach components are aimed at promoting interest in science, technology, engineering, and mathematics (STEM) disciplines and developing scientific literacy at the undergraduate and K-12 levels. These activities are focused on working with underrepresented students, including Native Americans, Hispanics, and women. Specific educational objectives are to collaborate with the Southwestern Indian Polytechnic Institute on an education and outreach program, continue mentoring activities for underrepresented populations and local K-12 teachers, and develop a combined undergraduate/graduate course in fabrication techniques for optoelectronic devices. The unique material properties of nonpolar and semipolar orientations of Gallium nitride (GaN) will be combined with a novel flip-chip fabrication scheme to enable the first polarization-pinned GaN-based VCSEL arrays and the first semipolar GaN-based green VCSELs. The novel fabrication scheme utilizes band-gap-selective photoelectrochemical etching to remove the growth substrate, enable high-reflectance dielectric distributed Bragg reflector mirrors, and provide fine control of the cavity length. The nonpolar and semipolar GaN platform exhibits large and highly anisotropic optical gain, which provides a simple method to achieve polarization pinning in short wavelength GaN-based VCSELs. When combined, these approaches enable blue and green VCSEL arrays that are applicable to polarization-sensitive optical systems and provide orders-of-magnitude higher output powers than single VCSELs. An output power of 50 mW from a 10x10 element nonpolar blue VCSEL array is set as an initial target. The thorough study of nonpolar and semipolar VCSELs will generate new fundamental knowledge about the correlations between polarization-pinning with band structure, higher-order modes, gain-cavity resonance offset, and operating conditions. The polarization, spectral purity, and noise properties of individual devices as well as arrays will be investigated with confocal microscopy and correlated to the material and device properties. Finally, the first investigation of band-gap-selective photoelectrochemical etching on semipolar GaN may reveal new fundamental materials phenomena and be applicable to other semipolar light-emitting devices.

该学院早期职业发展（职业）计划奖的研究目标是展示第一个具有稳定且可预测的光偏振的短波长（蓝色和绿色）垂直腔表面发射激光器（VCSEL）阵列。该方法将采用创新的制造工艺来解决氮化镓基材料的问题，这些问题此前限制了短波长 VCSEL 的输出功率、波长范围和功能。新型材料生长工艺将克服阻碍 VCSEL 中光偏振系统控制的基本挑战。实现具有稳定且可预测的光偏振的短波长 VCSEL 将使高密度光学数据存储、高分辨率印刷、照明、显示器、投影仪、微型原子钟和化学/生物传感等领域的独特应用成为可能，而这是传统边缘发射激光器难以实现的。为了满足需要更高功率光发射器的各种偏振敏感应用，这些器件将形成偏振钉扎阵列。教育和外展部分旨在提高本科生和 K-12 年级学生对科学、技术、工程和数学 (STEM) 学科的兴趣并培养科学素养。这些活动的重点是与代表性不足的学生合作，包括美洲原住民、西班牙裔和女性。具体的教育目标是与西南印度理工学院合作开展教育和推广计划，继续为弱势群体和当地 K-12 教师提供指导活动，并开发光电器件制造技术的本科/研究生联合课程。氮化镓 (GaN) 非极性和半极性取向的独特材料特性将与新颖的倒装芯片制造方案相结合，以实现首款偏振固定 GaN 基 VCSEL 阵列和首款半极性 GaN 基绿色 VCSEL。该新颖的制造方案利用带隙选择性光电化学蚀刻来去除生长衬底，实现高反射率电介质分布式布拉格反射镜，并提供对腔长度的精细控制。非极性和半极性GaN平台表现出大且高度各向异性的光学增益，这提供了一种在短波长GaN基VCSEL中实现偏振钉扎的简单方法。结合起来，这些方法可实现适用于偏振敏感光学系统的蓝色和绿色 VCSEL 阵列，并提供比单个 VCSEL 高几个数量级的输出功率。 10x10 元件非极性蓝色 VCSEL 阵列的 50 mW 输出功率被设置为初始目标。对非极性和半极性 VCSEL 的深入研究将产生关于偏振钉扎与能带结构、高阶模式、增益腔谐振偏移和工作条件之间的相关性的新的基础知识。将使用共焦显微镜研究单个器件以及阵列的偏振、光谱纯度和噪声特性，并将其与材料和器件特性相关联。最后，对半极性 GaN 的带隙选择性光电化学蚀刻的首次研究可能会揭示新的基本材料现象，并适用于其他半极性发光器件。