W dniu 15 kwietnia 2021 roku o godzinie 12:30 na platformie Webex (https://fizyka-umk.webex.com/fizyka-umk/) prof. Aleksandra Foltynowicz (Department of Physics, Umeå University, Sweden) wygłosi wykład pt. „High-Resolution Optical Frequency Comb Fourier Transform Spectroscopy".
Fourier transform spectroscopy (FTS) based on optical frequency combs offers a number of advantages over conventional Fourier transform infrared (FTIR) spectroscopy based on incoherent sources. The high spectral brightness of the comb sources allows measuring molecular spectra with high signal-to-noise ratios in a much shorter acquisition time, and their spatial and temporal coherence enables using multipass cells and cavities to increase the absorption sensitivity. What is more, the resolution of comb-based FTS is given by the linewidth of the comb modes rather than the optical path difference (OPD) in the spectrometer, provided that the OPD is matched to the inverse of the comb mode spacing. This implies that spectra with kHz resolution can be measured using an OPD of the order of a few tens of cm, which is impossible with conventional FTIR spectrometers.
I will present applications of comb-based FTS to high-resolution measurements in the near- and mid-infrared spectral range. In the near-infrared, we used cavity-enhanced complex refractive index spectroscopy to derive absorption and dispersion spectra of entire molecular bands from the broadening and shift of the cavity modes caused by the molecular sample. In the mid-infrared, we used direct absorption spectroscopy to measure and assign spectra of halogenated volatile organic compounds at 3.3 µm, and to retrieve center frequencies of N2O and CH4 transitions at 8 µm with precision better than 200 kHz. Finally, we employed a near-infrared comb as a probe in sub-Doppler resolution optical-optical double-resonance spectroscopy to measure and assign highly-excited states of methane in the 9000 cm-1 range.
Organizatorem Kolokwium Czwartkowego jest Instytut Fizyki UMK w Toruniu.
https://fizyka-umk.webex.com/fizyka-umk/j.php?MTID=me33a272f5b4f2929763ab6a9ec513bfd numer spotkania (kod dostępu): 183 854 1663, hasło spotkania: CKFA