Robust, fast and sensitive near-infrared continuous-filtering Vernier spectrometer.

Area of Science:

• Spectroscopy
• Laser Technology
• Cavity-Enhanced Spectroscopy

Background:

• Cavity-enhanced spectroscopy offers high sensitivity but often requires complex active stabilization.
• Previous implementations limited scan rates due to stabilization requirements.

Purpose of the Study:

• To present a novel, robust cavity-enhanced frequency comb spectrometer design.
• To eliminate the need for high-bandwidth active stabilization.
• To achieve high scan rates for improved spectral analysis.

Main Methods:

• Utilized a compact femtosecond Er-doped fiber laser.
• Employed a medium finesse cavity, diffraction grating, and custom moving aperture.
• Operated under the continuous-filtering Vernier principle without active stabilization.

Main Results:

• Demonstrated detection of CO2 and CH4 over wide spectral ranges (1.7 THz and 2.7 THz).
• Achieved high spectral resolution (6 GHz for CO2, 13 GHz for CH4).
• Reached absorption sensitivities of 5 × 10^-9 cm^-1 Hz^-1/2 and 1 × 10^-7 cm^-1 Hz^-1/2.

Conclusions:

• The new design enables robust, high-speed (up to 100 Hz) spectroscopy.
• The system achieves excellent sensitivity and resolution for gas analysis.
• Further investigation into scanning speed effects on signal amplitude is discussed.