Combined frequency comb and continuous wave cavity-enhanced optical-optical double-resonance spectrometer in the 1.7 $\mu$m range

Abstract

We present an optical-optical double-resonance (OODR) spectrometer based on a 3.3 $\mu$m continuous wave pump and two cavity-enhanced probes: a frequency comb tunable in the 1.64 - 1.8 $\mu$m range, and a comb-referenced continuous wave (CW) laser tunable in the 1.6 - 1.75 $\mu$m range. The comb probe provides broad spectral coverage (bandwidth up to 7 THz) for simultaneous detection of many sub-Doppler OODR transitions with sub-MHz line position accuracy, while the CW probe allows targeting individual transitions with kHz accuracy and higher signal-to-noise ratio in shorter time. Using the pump stabilized to the frequency of the R(0) transition in the $\nu$${}_3$ band of methane and the comb probe covering the 5550 to 6070 cm${}^{-1}$ interval, we detect 37 ladder-type transitions in the 3$\nu$${}_3$ $\leftarrow$ $\nu$${}_3$ band region and 6 V-type transitions in the 2$\nu$${}_3$ band region and assign them using available theoretical predictions. Using the CW probe, we measure selected ladder- and V-type transitions with much higher precision. We also detect Lamb dips in the R(0)- R(3) transitions of the 2$\nu$${}_3$ band and report their center frequencies with kHz level accuracy. The synergy effects of the comb- and CW-OODR open new possibilities in precision spectroscopy of levels that cannot be reached from the ground state.

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Cited by in corpus (4)

• Assignment of collision-induced four-level double-resonance transitions in the 3$\nu$${}_3$ $\Leftarrow$ $\nu$${}_3$ spectral region of methane
• Measurement and assignment of E-symmetry states in the 6010-6110 cm${}^{-1}$ and 8940-9150 cm${}^{-1}$ ranges of methane using optical frequency comb double-resonance spectroscopy
• Theory of Lineshapes in Optical-Optical Double Resonance Spectroscopy
• Optical frequency comb double-resonance spectroscopy of the 9030-9175 cm${}^{-1}$ states of ethylene