High-accuracy and wide dynamic range frequency-based dispersion spectroscopy in an optical cavity

Area of Science:

• Spectroscopy
• Gas detection
• Metrology

Background:

• Cavity-enhanced techniques offer high precision but are limited by amplitude propagation and detection accuracy.
• A need exists for spectroscopic methods with reduced systematic errors for challenging gas detection applications.

Purpose of the Study:

• To demonstrate a frequency-based molecular dispersion spectroscopy method for highly accurate gas detection.
• To overcome the accuracy limitations of existing intensity-based spectroscopic techniques.

Main Methods:

• Utilizing sub-Hertz precision frequency measurements of optical cavity resonances.
• Implementing frequency-based molecular dispersion spectroscopy without requiring linear, high-bandwidth, or phase-sensitive detectors.
• Demonstrating traceability of spectral axes to the primary frequency standard.

Main Results:

• Achieved sub-per-mille accuracy and a wide dynamic range, surpassing previous spectroscopic methods.
• Demonstrated high sensitivity of 5×10^-11 cm^-1 and high speed limited by cavity response time.
• Experimentally validated the superiority of frequency-based over intensity-based spectroscopy.

Conclusions:

• Frequency-based molecular dispersion spectroscopy offers superior accuracy, sensitivity, and speed for gas detection.
• The method is versatile, applicable across Doppler to collisional regimes without experimental modification.
• This approach motivates the replacement of intensity-based absorption spectroscopy with frequency-based dispersion spectroscopy for high-accuracy applications.