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Field-Resolved Infrared Metrology

Dr. Ioachim Pupeza, Experimental Physics, MPQ

Our research primarily addresses the development of novel tools and techniques for field-resolved spectroscopy (FRS) of molecular vibrations in the IR spectral region (wavelengths >2µm). IR vibrational spectroscopy yields insights into molecular composition, structure and conformation. Among its numerous applications, further improvement of the sensitivity of state-of-the-art vibrational spectroscopy promises to lead to breakthroughs in the early detection of diseases.

Field-resolved spectroscopy of impulsively excited molecular vibrationsPic. 1. Field-resolved spectroscopy of impulsively excited molecular vibrations.

We harness the advantages of employing phase-stable, broadband, ultrashort IR pulses and electric-field-resolved detection for vibrational spectroscopy. Most importantly, the phase-coherent superposition of all frequency components of the IR source into an ultrashort, waveform-stable pulse enables confinement of the impulsive excitation event to a ~100-femtosecond time window. Sampling of the resulting electric field, as the most fundamental ensemble-averaged physical measurable of the vibrationally excited sample, allows one to distinguish between the time-domain fingerprints of these vibrations and the fast decaying instantaneous response of the sample (see illustration above). Thus, FRS permits IR-background-free detection of molecular fingerprints and, therefore, has the potential to provide unparalleled sensitivity and specificity for vibrational spectroscopy.