Coherent dual-comb interferometry with quasi-integer-ratio repetition rates

Area of Science:

• Physics
• Spectroscopy
• Optical Engineering

Background:

• Dual-comb spectroscopy (DCS) is a powerful technique for high-resolution spectral measurements.
• Conventional DCS often requires precisely matched repetition rates between frequency combs, limiting flexibility.
• Asynchronous sampling in DCS presents challenges in data processing and potential crosstalk.

Purpose of the Study:

• To present a generalized dual-comb interferometry method enabling flexible spectral resolution and acquisition time.
• To demonstrate the capability of this method using combs with quasi-integer-ratio repetition rates.
• To overcome limitations of conventional DCS by allowing independent adjustment of comb parameters.

Main Methods:

• Utilizing two frequency combs with quasi-integer-ratio repetition rates (16.67 MHz and 100 MHz).
• Probing an 80-cm ring cavity with one comb and asynchronously sampling its impulse response with the other.
• Employing deconvolution to remove photodetector impulse response and prevent crosstalk between time-multiplexed interferograms.

Main Results:

• Successfully generated six time-multiplexed independent interferograms.
• Achieved a spectral point spacing of 16.67 MHz and a spectral signal-to-noise ratio (SNR) of 55 dB after averaging 15,000 interferograms (500 s acquisition time).
• Demonstrated that adjusting the repetition rate of one comb allows for reduced spectral point spacing or acquisition time.

Conclusions:

• The generalized dual-comb interferometry method offers enhanced flexibility compared to conventional techniques.
• This approach is robust against photodetector crosstalk through deconvolution.
• The technique paves the way for more adaptable and efficient spectroscopic measurements.