Subcategory: Materials Science
Daniel Hart - Hampton University
Co-Author(s): Uwe Hommerich, Eiei Brown and Al Amin Kabir, Hampton University, Hampton, VA; Sudhir Trivedi, Brimrose Corporation of America, Sparks, MD
The understanding of trace gases such as CO, CO2, CH4, and SO2 are necessary in the development of the chemistry and dynamics of Earth and other planets in our solar system. These and similar greenhouse molecules have strong absorption peaks in the mid-IR (3-7 µm) spectral region. For laser remote sensing of trace gases, there is a need for the development of compact and efficient lasers operating in the mid-IR region. Also, blackbody radiation from the Sun and the Earth causes interference in space laser systems. However, the Sun’s blackbody radiation extends to ~2 microns and Earth’s radiation begins to reemit at ~ 6 microns. Being able to take advantage of this 2-6 micron window would provide unprecedented sensitivity in this region. Among solid-state laser type materials, the oxide crystal YAG (Yttrium Aluminum Garnet) is the most widely used laser host and has high maximum phonon energy of ~ 700 cm-1. The large maximum phonon energy in YAG, however, leads to strong fluorescence quenching of rare earth centers for wavelengths > 2000 nm. This study compares the absorption and emission properties (spectral and lifetimes) of Dysprosium (Dy3+) doped TlPb2Br5 and KPb2Br5 crystals as possible new MIR gain media. Both halide crystals have maximum phonon energies of only ~150 cm-1. The investigated materials were synthesized from commercially available starting materials of PbBr2, KBr, and TlBr. 2 wt% of DyBr3 was added during synthesis for doping experiments. Following several purification steps, bulk crystals were grown using vertical Bridgman technique resulting in small samples (~3mmx3mmx2mm) useful for initial spectroscopic studies. Emission bands centered at ~2.8 m and 4.3 m were observed from Dy: TPB and Dy: KPB following optical pumping at ~1.3 m or ~1.7 m. The 4.3 m emission bands were further investigated for their room-temperature lifetimes and emission cross sections. The 4.3 m emission lifetimes for Dy:TPB and Dy:KPB were 5.2 ms and 4.4 ms, respectively. The peak emission cross sections for Dy:TPB and Dy:KPB were ~0.5 x 10-20 cm2 and ~0.2 x 10-20 cm2, respectively. More details of the spectroscopic studies for Dy: TPB and Dy: KPB and an evaluation for infrared laser applications will be discussed at the conference.ERN_2018_Dan_UH_revised.docx
Funder Acknowledgement(s): The work at Hampton was supported by the National Science Foundation (grants HRD-1649150 and HRD-1137747). D. Hart is grateful for support by the NASA Pathways Research Engineering Fellowship.
Faculty Advisor: Uwe Hommerich, firstname.lastname@example.org
Role: Emission Cross Section Calculations, Emission Measurements, and Life time Measurements