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LAMMP Seminar Video
Laser-induced flourescence spectroscopy for application in chemical and biological sensing and optical refrigeration
Eric Kumi Barimah, PhD

Laser-induced breakdown spectroscopy (LIBS) is an innovative technique that has been used as a method for fast elemental analysis in real time. Conventional ultraviolet-visible (UV-VIS) LIBS has been applied to detect the elemental composition of different materials, including explosives, pharmaceutical drugs, and biological samples. The extension of conventional LIBS to the infrared region (∼1-12 μm) promises to provide additional information on molecular emission signatures due to rotational-vibrational transitions. In this research, a pulsed Nd: YAG laser operating at 1064nm was focused onto several sodium compounds and potassium compounds to produce an intense plasma at the target surface. Several distinct infrared (IR) atomic emission signatures were observed from all sodium and potassium containing compounds. The atomic emission lines observed from the investigated samples matched assigned transitions of neutral sodium and potassium atoms published in the National Institute of Standards and Technology (NIST) atomic database. The observed molecular emission showed strong correlation with the conventional Fourier Transform Infrared Spectrometry (FTIR) absorption spectra of the investigated samples. In the second part of this research, Tm3+ doped solids have shown promising results for laser cooling applications at IR wavelengths of ~2 μm. The extended IR fluorescence of the involved Tm3+ transition (3H6 → 3F4), however, requires low-phonon energy hosts reducing the detrimental effect of non-radiative decay through multi-phonon relaxation. In this work the temperature dependent absorption and emission properties of Tm doped KPC (hνmax<200 cm-1) and KPB (hνmax<140 cm-1) crystals were evaluated for applications in laser cooling. Employing a continuous-wave laser operating at 1.907 μm, Tm: KPC and Tm: KPB crystals revealed a very small heat load resulting in temperature increase of ∼ 0.3 (± 0.1)oC. The results derived from IR imaging were also confirmed by the fluorescence thermometry experiments, which showed only minimal changes in the FIR intensity ratio of the green Er3+ fluorescence lines from Er:KPC.

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