Ultrafast Condensed-Phase Dynamics Using Mid-Infrared and Terahertz Spectroscopies
Physical Measurement Laboratory, Nanoscale Device Characterization Division
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Femtosecond laser methods are used to measure ultrafast carrier and energy dynamics in condensed phase and nanoscale materials. These include tunable mid-infrared (MIR) or visible/ultraviolet (Vis-UV) excitation with multichannel MIR or Terahertz (THz) generation-detection methods for time-resolved spectroscopy, hyperspectral and thermal imaging, and related nonlinear spectroscopies. Systems investigated include carriers in semiconductors and 2D/TMD thin films, metal plasmons, photoreactions and vibrational energy transfer of inorganic species in solution, crystals and on surfaces. Emphasis is placed on developing vibrational and THz nanoprobes (e.g., scattering Near-Field Optical Microscopy or s-SNOM) to investigate novel solar cell and photovoltaic materials, electronic-vibrational energy transfer processes (excitons) and nanoscale carrier processes in conductive materials. We are also developing THz methods to perform thermal imaging in active 3D integrated circuits.
Apparatus includes (1) two Ti:Sapphire 20 fs oscillators, each with kHz regenerative amplifiers and UV-visible IR OPAs; (2) a THz pump-probe spectrometer and high power s-SNOM imaging apparatus; (3) nonlinear crystals for sum, mid-IR, and THz generation; (4) CCDs and mid-IR/THz focal-plane arrays for multichannel detection and imaging applications; and (5) MIR and THz Fourier transform infrared spectrometers for static sample spectroscopy. For more detailed information and recent publications, please see Web pages at: https://www.nist.gov/people/edwin-j-heilweil