Mid-Infrared (MIR) light can interact with molecules by selectively exciting molecular vibrational modes. On one hand, in combination with photonic structures, MIR can target specific vibrational states of molecular to influence chemical reactions; on the other hand, IR spectroscopy has long been used as a molecular sensing tool. In this talk, I will discuss recent advancement in my lab, focusing on these two key topics. In the first topic, I will explain how photonic environments can modify molecular dynamics through strong light-matter coupling. This strong coupling leads to the molecular vibrational polaritons – a hybrid quasiparticle between light and matter. Using two-dimensional infrared (2D IR) spectroscopy, we have demonstrated that strong coupling to photonic environments can efficiently promote energy transfer within or between molecules, subsequently slowing down competing reaction pathways. This research provide insights into designing photonic structures to modify chemical landscapes and influence reaction pathways. In the second topic, I will present the latest development in fast-scanning vibrational sum frequency generation (VSFG) microscopy, tailored to differentiate collagen tissues in healthy and tumorous conditions. We revealed distinct spectral signatures between healthy and tumorous tissues, which arise from the coherent nature of VSFG signals – akin of a microscopic Young’s double slit experiment. VSFG’s unique power to resolve varying alignments of collagen fibrils empowers it as a distinctive label-free technique for tumor identification in the future.
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