Dual-comb spectroscopy using plasmon-enhanced-waveguide dispersion-compensated quantum cascade lasers.

Area of Science:

• Spectroscopy
• Quantum Cascade Lasers
• Mid-Infrared Optics

Background:

• Dual-comb spectroscopy (DCS) is a powerful technique for molecular analysis.
• Achieving fast response times and high resolution in mid-infrared DCS remains a challenge.

Purpose of the Study:

• To develop a sub-millisecond response time mid-infrared dual-comb spectroscopy system.
• To demonstrate the system's performance using gas samples.

Main Methods:

• Utilized a balanced asymmetric dual-comb setup with dispersion-compensated quantum cascade lasers.
• Employed a computational phase and timing-correction procedure for coherence validation and averaging.
• Measured spectra of Bromomethane (CH3Br) and Freon 134a (CH2FCF3) around 7.8 μm.

Main Results:

• Achieved sub-millisecond response times.
• Demonstrated a noise-equivalent absorption better than 1×10-3 Hz-1/2.
• Obtained a spectral resolution of 9.8 GHz (0.326 cm-1) over a 1 THz (32 cm-1) bandwidth.
• Reported an average optical power exceeding 1 mW per spectral element.

Conclusions:

• The developed system offers a significant advancement in mid-infrared spectroscopy speed and performance.
• The computational correction method effectively validates laser coherence and enables averaging.
• This technology has potential applications in real-time gas analysis and monitoring.