En route to broadly tunable middle-infrared optically and electrically pumpable Cr2+ and Fe2+ doped II-VI semiconductor lasers

该项目的目的是进一步探索Cr2+：ZnSe晶体作为电激励下宽可调中红外激光的潜在候选者的能力。所提出的假设是，低维Cr2+：ZnSe结构可以对量子阱和量子点中的电子-空穴对提供量子限制，并伴随着激子到掺杂离子的有效能量转移，这将为带间光或电激发下的Cr2+激光提供一条有效的途径。我们的理论基础与众所周知的观察结果有关：在体相和薄膜中，由于有效的自由载流子捕获伴随着Cr2+的中心内中红外发射，锌硒铬显著降低了锌硒可见光发射的效率。需要解决的问题包括：a)用热扩散、脉冲激光沉积和溶胶-凝胶技术分别制备高光学质量和高量子效率的掺铬块体、薄膜、量子阱和量子点；b)在带间和电激发下主体离子与Cr2+离子之间的能量通路的物理机制；c)在带间光激发下受激发射的理论建模和实验实现以及块体和纳米结构中的电致发光。将研究的方法将导致低成本、光学和电可泵浦的、可广泛调谐的中红外激光光源的突破性进展，这将影响医疗、环境、科学和反恐应用，如：爆炸物、化学和生物战剂及其前体的检测、工业过程控制以及患者呼气中具有重要医学意义的分子化合物的测量。这一开发项目的成果将作为“技术机会”提供给美国激光和光电子公司，以最大限度地发挥该项目的社会影响。拟议计划的一个关键组成部分是培训科学家和工程师。这种劳动力发展将涉及(I)将研究成果纳入阿拉巴马大学系统的两个校区教授的四门课程，(Ii)研究生培训，以及(Iii)通过REU网站进行本科生研究。该计划将让不同教育水平的研究生和本科生(包括NSF资助的阿拉巴马州少数族裔参与联盟AMP的学生)接触激光、光学光谱学、材料和纳米物理等主题。这将鼓励在这些领域从事研究生和研究生工作，有助于使科学和工程研究生课程和工作场所多样化。

The objective of this program is to further explore capabilities of Cr2+:ZnSe crystals as potential candidates for broadly tunable middle infrared lasing under electrical excitation. The hypothesis to be verified in the proposed project is that low dimensional Cr2+:ZnSe structures can provide quantum confinement of the electron-hole pairs in quantum wells and quantum dots accompanied by effective energy transfer from excitons to dopant ions which will enable an efficient pathway for Cr2+ lasing under interband optical or electrical excitation. Our rationale relates to the well known observation that in bulk and thin film ZnSe chromium reduce considerably the efficiency of ZnSe visible emission due to effective free-carrier capture accompanied by intra-center mid-IR emission from Cr2+. Among the problems to be addressed are a) fabrication and characterization of high optical quality and high quantum efficiency Cr doped bulk, thin films, quantum wells and quantum dots prepared by thermal diffusion, pulsed laser deposition, and sol-gel technology, respectively; b) physical mechanisms of the energy pathways between the host and Cr2+ ions under interband and electrical excitation in the bulk and nanostructures c) theoretical modeling and experimental realization of stimulated emission under interband optical excitation as well as electroluminescence in the bulk and the nanostructures. Broader Impacts.The approaches to be investigated will lead to ground-breaking advances for low-cost optically and electrically pumpable broadly tunable mid-IR laser sources which will impact medical, environmental, scientific, and counter-terrorism applications such as: detection of explosives, chemical and biological warfare agents and their precursors, industrial process control, and measurement of medically important molecular compounds in the exhaled breath of patients. The outcome of this development project will be offered as "technology opportunity" for U.S. laser and photonics companies in order to maximize the societal impact of the project. A critical component of the proposed program is training of scientists and engineers. This workforce development will involve (i) incorporation of findings into four courses taught to two campuses of the University of Alabama System, (ii) graduate student training, and (iii) undergraduate student research through REU site. The program will expose graduate and undergraduate students (including those in NSF-funded Alabama Alliance for Minority Participation AMP) at different education levels to topics in lasers, optical spectroscopy, materials and nanophysics. This will encourage the pursuit of graduate and post-graduate work in these fields helping to diversify both science and engineering graduate programs, and the workplace.