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Abstract:
Dual-comb spectroscopy offers an unprecedented tool for spectroscopy due to its high temporal resolution, high spectral resolution, and broadband coverage. In this thesis, we further developed dual-comb spectroscopy by utilizing its temporal resolution capability to probe the evolution of laser-induced plasma (LIP) over time scales from μs to ms with a temporal resolution on the order of < 20 μs. In order to fully leverage the power of dual-comb spectroscopy, we developed the method of burst mode dual-comb spectroscopy. We have optimized the capability to study time evolution in a single shot while optimizing spectral resolution and optical bandwidth. In our group, we have demonstrated sources that cover from ∼ 700 nm to 1560 nm using laser sources such as Ti: Sapphire laser, Yb fiber laser, and Er fiber laser. We further extended the coverage of frequency comb to the ultraviolet regime using two approaches. The 1st approach is quadrupling the fundamental laser 1064 nm using two stages of second harmonic generation (SHG) to achieve deep UV 265 nm, which enabled us to demonstrate the 1st DUV dual-comb spectroscopy onto laser-induced plasmas. The 2nd approach utilizes intra-cavity high harmonic generation where we performed a proof-of-concept UV dual-comb spectroscopy using 3rd harmonics around 350 nm and measured etalon and Cs transition. This UV dual-comb spectroscopy using intra-cavity high harmonic generation is scalable to vacuum UV (VUV) and extreme UV (EUV) below 100 nm, which makes it an ideal tool for precision spectroscopy in the VUV and EUV.
Please email Kane Zhang at kanezhang@arizona.edu or me for Zoom link.