RUI: Synthesis and Optical Spectroscopy of Thulium Sensitized Potassium Lead Chloride Laser Materials

Loyola University Maryland, Inc., Baltimore MD

Investigators

Abstract

0245455 Ganem The proposed research is on thulium-sensitized potassium lead chloride KPb2C15 laser crystals. Research will include synthesizing these materials and performing optical spectroscopy using absorption and laser-induced fluorescence techniques. The KPb2C15 crystalline host is a material that has both mechanical stability and low-phonon energies. When KPb2C15 is doped with rare earth ions, the reduced phonon energies enable useful infrared fluorescence transitions that would be absent in traditional oxide or fluoride laser crystals. Since it is a mechanically stable low-phonon energy crystal, it shows promise for the development of rugged, durable, high-powered, solid-state rare earth-based infrared lasers. Thulium is widely used to sensitize infrared lasers for pumping with low-cost 800 nm diodes. To date no studies of the use of thulium in KPb2C15 have been conducted. The research will measure thulium absorption, emission, and energy transfer to the rare earth ions Pr 3+ and Er 3+ co-doped into KPb2C15. Intellectual Merit of Proposed Research: Interest in low-phonon energy laser materials, especially chloride crystals, has increased significantly in recent years. Long-wavelength electronic transitions are more likely to radiate in a chloride host because the reduced phonon energies inhibit multi-phonon relaxation. Some recent examples: Lasers based on Pr 3+ in LaC13 have been operated at 1.7, 5.2 and 7.2 um with this last transition operating at room temperature. The problem of extreme moisture sensitivity and mechanical instability remains for LaCl3 and has limited the practicality of these devices. The use of KPb2C15, the subject of this proposal, is of merit because it is a mechanically stable chloride crystal and will make possible the development of practical chloride-based infrared lasers. As part of the work under my current NSF grant, we have demonstrated a room temperature diode-pumped 4.6 um Er 3+ laser using KPb2C15. The proposed work is to improve both the Er 3+ laser and Pr 3+ lasers with Tm 3+ sensitization. Broad Impacts of Proposed Research: The proposed research will impact both education programs and vital areas of technology. The technological impact will occur in two areas of special interest to the United States government. - Remote sensing- As of this writing, the Department of Energy (DOE), through its Office of Defense Nuclear Nonproliferation (NN), is funding an SBIR proposal to develop low-phonon energy materials, including KPb2C15, as part of a program to fund support technologies for sensors used in national security applications. - Infrared countermeasures (IRCM) One motivation for developing the erbium-doped KPb2C15 laser is for IRCM. The 4.6 micron operating wavelength is ideally suited for IRCM since it falls in an atmospheric transmission window between 4 and 5 microns. The significance of the IRCM applications has motivated the Navy to fund a Phase I SBIR contract for the growth of rare earth doped KPb2C15. Thulium-doped KPb2C15 is an area of research not under active exploration by the companies under contract, however it is of interest to them because of the potential to expand the market for the material. The educational impact of this RUI proposal (Research at Undergraduate Institutions), described in the RUI impact statement, includes: undergraduate participation, outreach to other schools (including urban K-12 schools and an all women college) and teaching-research integration.