Combined frequency comb and continuous wave cavity-enhanced optical-optical double-resonance spectrometer in the 1.7...

Area of Science:

• Molecular Spectroscopy
• Quantum Optics
• Laser Physics

Background:

• Optical-Optical Double-Resonance (OODR) spectroscopy is a powerful technique for probing molecular energy levels.
• Previous OODR methods often face limitations in spectral coverage or transition-specific accuracy.

Purpose of the Study:

• To develop and demonstrate a novel OODR spectrometer combining a frequency comb and a continuous wave (CW) laser probe.
• To achieve simultaneous broad spectral coverage and high-precision measurements of molecular transitions.

Main Methods:

• Utilized a 3.3 µm CW pump laser and two cavity-enhanced probes: a broadband frequency comb (1.64-1.8 µm) and a tunable CW laser (1.6-1.75 µm).
• Employed methane's R(0) transition in the v3 band as the pump source.
• Detected sub-Doppler OODR transitions in methane's 2v3 and 3v3 bands.

Main Results:

• Simultaneously detected 37 ladder-type and 6 V-type transitions with sub-MHz accuracy using the frequency comb probe.
• Measured selected transitions with kHz accuracy and high signal-to-noise ratio using the CW probe.
• Reported kHz-level accuracy for Lamb dips in methane's 2v3 band transitions.

Conclusions:

• The synergistic use of comb and CW probes in OODR spectroscopy offers enhanced capabilities for precision measurements.
• This technique opens new avenues for studying molecular energy levels not accessible from the ground state.
• The developed spectrometer provides a versatile platform for high-accuracy molecular spectroscopy.