Mid-infrared (MIR) laser sources have demonstrated diverse applications in science and technology. For spectroscopy applications, numerous molecules have unique absorption features in this range, and one needs a spectrally broad coherent laser source for parallel detection of mixtures of species. Frequency down-conversion in nonlinear optical materials via second-order nonlinear susceptibility is one of the promising techniques to generate the spectral coverage of more than an octave in the MIR, assisted by emerging novel crystals. The nonlinear light-matter interactions in such special crystals as ZnSe ceramics have not been analyzed. Additionally, through the use of high-intensity few-cycle optical pulses, high-order nonlinear effects such as four-wave mixing, multiphoton absorption, and nonlinear refraction come into play beyond conventional second-order nonlinear interaction. In this thesis, the nonlinear interactions for generating broadband MIR were studied through both experimental and numerical approaches. First, a nonlinear frequency conversion model based on random phase matching was developed in zinc-blende polycrystalline structures. Monte Carlo simulation statistically verifies that a disordered material could perform on par with a quasi-phase-matched material for frequency conversion in ultrafast interactions. Second, the nonlinear interaction in orientation-patterned GaP combined with an optical parametric oscillator was numerically analyzed. A wave propagation model discovers that third-order nonlinearity plays an important role in the process of spectral evolution. Finally, using a 2.35-µm Cr:ZnS mode-locked laser, nonlinear absorption and nonlinear refractive index were characterized in the Z-scan technique for GaP, ZnSe, GaSe, and ZGP crystals. The visualization of nonlinear interactions and the uncovering of nonlinear parameters will be a guide for optimizing experimental systems and will further advance the development of MIR laser sources.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd2020-1886 |
| Date | 01 December 2021 |
| Creators | Kawamori, Taiki |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations, 2020- |
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