Crystal Growth and Energy Transfer in Cr2+:CdSe and Cr2+:CdSSe Systems

该项目旨在更好地了解基于Cr2+掺杂硫化物的激光介质中的材料特性/加工关系。1)用物理气相输运(PVT)和高温溶液区带法生长掺杂浓度在1016-1019ion/cc范围内的Cr2+：CdSe和Cr2+：CdSxSe1-x大块单晶。讨论的问题包括：高掺杂浓度下掺杂和缺陷形成的热力学限制和S合金化的影响；铬的其他氧化态(如Cr1，Cr3，Cr4)的形成以及Cd或Se超压对控制化学计量比的作用；2)将进行光谱测量，以解决以下问题：这些晶体在建议的工作波长下是否有效发射；是否存在令人满意的能量流动路径，以便材料可以被泵浦(激活)以产生所需的反转；是否存在足够大的寄生损耗，足以抑制激光作用；在这种宿主中，Cr2+的激发途径是什么，包括泵浦更高能态以实现有效的红外发射的可能性。CdSSe基质的几个固有优点是：能够获得单晶，存在自然双折射，可以通过调节S/Se的比例来调整性质。基于Cr2+：CdSe及其相关三元化合物的可调谐固态中红外激光器为开发用于遥感、污染监测、军事和医疗应用的实用光源提供了机会。与行业组织和国家实验室的密切互动和合作将继续下去，帮助加速开发与材料研究成果相结合的有用光学设备。%该项目既涉及基础研究问题，又涉及教育问题，并通过将学生教学和培训纳入具有高度技术相关性的材料科学领域，将研究和教育结合起来，以激励学生在相关领域从事职业。菲斯克大学是一所历史悠久的黑人学院和大学(HBCU)，致力于增加未被充分代表的少数族裔在自然科学方面的参与。该项目将加强其长期努力，从代表性不足的群体中招募、培训和指导学生。

This project seeks better understanding of materials properties/processing relationships in laser media based on Cr2+ doped chalcogenides. Two experimental focus areas will be pursued: 1) growth of bulk single crystals of Cr2+:CdSe and Cr2+:CdSxSe1-x crystals with a range (1016 -1019 ions/cc) of dopant concentrations by physical vapor transport (PVT) and high temperature solution zoning. Issues addressed include: thermodynamic limits of doping and defect formation at high dopant concentrations and the effect of S alloying; formation of other oxidation states of Cr (e.g. Cr+1 , Cr+3 , Cr+4 ) and the role of Cd or Se overpressure to control stoichiometry; 2) spectroscopic measurements will be conducted to address questions such as: do these crystals emit efficiently at the proposed wavelength of operation; are there satisfactory energy flow pathways such that the material can be pumped(activated) to produce the required inversion; are parasitic losses present that are substantial enough to inhibit laser action; what are the excitation pathways of Cr2+in this host, including the possibility of pumping higher energy states to achieve efficient infrared emission. Several intrinsic advantages of the CdSSe host are: demonstrated ability to achieve single crystals, presence of natural birefringence, possibility of tailoring properties by adjusting the S/Se ratio. Tunable solid state mid-IR lasers based on Cr2+:CdSe, and its related ternary compounds, represent an opportunity for developing practical light sources for remote sensing, pollution monitoring, military and medical applications. Close interactions and collaborations with industrial organizations and national labs will continue, helping to accelerate the development of useful optical devices in conjunction with materials research outcomes. %%% The project addresses both basic research issues and education, and the integration of research and education through incorporation of student teaching and training in an area of materials science of high technological relevance, serving to motivate students to pursue careers in related areas. Fisk University is a Historically Black College and University (HBCU) committed to increasing the participation of underrepresented minorities in physical sciences. This project will augment its long-standing effort to recruit, train and mentor students from underrepresented groups.***