Cavity ring-down spectroscopy at 2-μm wavelength assisted by a comb-locked optical parametric oscillator

Area of Science:

• Spectroscopy
• Molecular Physics
• Quantum Optics

Background:

• Cavity ring-down spectroscopy (CRDS) is a powerful technique for sensitive molecular detection.
• Precise frequency measurements are crucial for molecular identification and characterization.
• Optical frequency combs provide a stable and accurate frequency reference.

Purpose of the Study:

• To develop a comb-locked cavity ring-down spectrometer for high-precision molecular spectroscopy at 2 μm.
• To investigate the performance of the developed spectrometer by probing N2O transitions.
• To measure absolute center frequencies of N2O transitions with high accuracy.

Main Methods:

• Utilizing an external-cavity diode laser offset-frequency locked to a singly-resonant optical parametric oscillator (SRO).
• Locking the SRO to a self-referenced optical frequency comb stabilized by a GPS-disciplined Rb-clock.
• Probing N2O transitions in hot vibrational bands using the developed spectrometer.

Main Results:

• Demonstrated high-precision molecular spectroscopy at 2 μm.
• Observed a previously uncharacterized N2O transition.
• Achieved absolute center frequency measurements with a 1-σ global uncertainty of 108 kHz.

Conclusions:

• The developed comb-locked CRDS system enables high-accuracy molecular spectroscopy.
• The instrument successfully measured N2O transitions, including a novel one.
• This work contributes to improved molecular databases and spectroscopic measurements.