Presentation Information
[3G01【女子大学院生優秀賞2024】]Broadband vibrational spectroscopy using infrared pulses generated by laser-induced air plasma
*Risako Kameyama1 (1. The Institute for Solid State Physics, The University of Tokyo)
Vibrational sum-frequency generation (V-SFG) spectroscopy is a surface/interface-sensitive technique based on a second-order nonlinear optical process. However, conventional V-SFG suffers from limited detection bandwidth due to the phase-matching conditions of IR pulse generation using solid nonlinear crystals, restricting coverage to ~400 cm-1, and making low-frequency IR generation below 800 cm-1 difficult. To overcome this, we adopted broadband IR pulses produced via two-color laser-induced air plasma. This technique offers ultra-broad spectral coverage and sub-100 fs pulse durations. In a proof-of-principle experiment polymer film on gold, we successfully obtained vibrational spectra across 600–3000 cm-1, consistent with Raman and IR spectra. Further improvements extended the measurable range to 150–4000 cm-1, enabling the detection of transverse optical phonons in GaAs (~270 cm-1). This system can also be applied to bulk IR absorption measurements. Due to its ultrashort pulse duration, this technique holds promise for future time-resolved studies of both interfacial and bulk molecular dynamics.