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

这个教师早期职业发展（CAREER）计划奖的研究目标是展示第一个短波长（蓝色和绿色）垂直腔面发射激光器（VCSEL）阵列，具有稳定和可预测的光偏振。该方法将使用创新的制造工艺来解决GaN基材料的问题，这些材料以前限制了短波长VCSEL的输出功率，波长范围和功能。阻碍VCSEL中光偏振的系统控制的基本挑战将通过新型材料生长工艺来克服。实现具有稳定和可预测的光偏振的短波长VCSEL将使高密度光学数据存储、高分辨率打印、照明、显示器、投影仪、微型原子钟和化学/生物传感中的独特应用成为可能，而这些应用是传统边发射激光器不容易实现的。为了解决各种需要更高功率光发射器的偏振敏感应用，这些器件将形成偏振钉扎阵列。教育和推广部分旨在促进对科学，技术，工程和数学（STEM）学科的兴趣，并在本科和K-12水平上发展科学素养。这些活动的重点是与代表性不足的学生，包括美洲原住民，西班牙裔和妇女的工作。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，继续为代表性不足的人口和当地K-12教师开展辅导活动，并开发光电设备制造技术的综合本科/研究生课程。氮化镓（GaN）的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，以实现第一个偏振钉扎GaN基VCSEL阵列和第一个半极性GaN基绿色VCSEL。新的制造方案利用带隙选择性光电化学蚀刻去除生长衬底，使高反射率的介质分布布拉格反射镜，并提供腔长度的精细控制。非极性和半极性GaN平台具有大的和高度各向异性的光学增益，这提供了一种简单的方法来实现短波长GaN基VCSEL的偏振钉扎。当组合时，这些方法使得蓝色和绿色VCSEL阵列能够适用于偏振敏感光学系统并且提供比单个VCSEL高数量级的输出功率。将来自10 × 10元件非极性蓝色VCSEL阵列的50 mW的输出功率设置为初始目标。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、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。的偏振，光谱纯度，和噪声特性的个别设备以及阵列将与共焦显微镜和相关的材料和设备的性能进行研究。最后，半极性GaN的带隙选择性光电化学蚀刻的首次研究可能揭示新的基本材料现象，并适用于其他半极性发光器件。

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.