High-SNR mid-infrared dual-comb spectroscopy using active phase control cooperating with CWs-dependent phase...

Area of Science:

• Spectroscopy
• Molecular Physics
• Quantum Optics

Background:

• Mid-infrared (MIR) dual-comb spectroscopy (DCS) offers rapid and accurate molecular metrology.
• Maintaining coherence between frequency combs in the MIR region for high-quality spectral analysis presents significant challenges due to comb frequency instability.

Purpose of the Study:

• To develop a comb-teeth resolved MIR DCS system with enhanced coherence and signal-to-noise ratio.
• To overcome the limitations of current MIR DCS techniques for precise molecular characterization.

Main Methods:

• Implemented active phase control using four actuators integrated into near-infrared (NIR) seed combs for coherence maintenance.
• Utilized parallel difference frequency generation (DFG) with PPLN waveguides to create a coherent MIR dual-comb spectrometer.
• Employed CWs-dependent (CWD) resampled interferogram timing correction to optimize DCS performance.

Main Results:

• Achieved a significant improvement in the merit of DCS, increasing from 7.5 × 10^5 to 2.5 × 10^6.
• Successfully measured methane hot-band absorption spectra (v3 band) using the developed MIR DCS.
• Demonstrated excellent agreement with HITRAN database values, with a standard deviation on recording residual of 0.76%.

Conclusions:

• The developed MIR DCS with active phase control and CWD interferogram timing correction effectively enhances coherence and SNR.
• This advanced technique shows significant potential for precise characterization of rovibrational transitions in MIR molecules.
• The system provides a robust platform for high-accuracy molecular metrology in the mid-infrared spectrum.