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

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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.***