Speaker
Description
We demonstrate the first cavity-enhanced spectrometer fully operating in a deep cryogenic regime down to 4 K. Not only the sample but the entire cavity, including the mirrors and cavity length actuator [1], is uniformly cooled down ensuring the thermodynamic equilibrium of the gas sample. The setup is designed in a way that efficiently attenuates both external vibrations and those originating from the cryocooler itself ensuring stable operation of the optical cavity. High tunability of the wavelength is achieved by implementation of an optical parametric oscillator (OPO) pumped by the 1064 nm CW seed laser amplified to 10 W. This instrument opens the way to a variety of fundamental and practical applications [2].
We demonstrate a high-resolution CRDS measurement of the S(0) 1-0 line in molecular hydrogen. Our approach allows for carrying out measurements at thermal equilibrium in the lowest temperature to date, being able to obtain clear spectra in temperatures below 5 K. Our result improves the previous best measurement of this line by three orders of magnitude. The deviation of our measurement from the most recent theoretical value is as small as 88 kHz [3]. With a total theoretical combined uncertainty of 380 kHz this corresponds to validating the quantum theory for molecules at the tenth significant digit.
References:
1. M. Słowiński et. al., Rev. Sci. Instrum. 93, 115003 (2022)
2. K. Stankiewicz et. al., Cavity-enhanced spectroscopy in the deep cryogenic regime for quantum sensing and metrology, Nature Physics (accepted: 30.01.2026)
3. K. Pachucki & J. Komasa, J. Chem. Theory Comput. 21, 12664–12673 (2025)