Cavity mode-width spectroscopy with widely tunable ultra narrow laser

Area of Science:

• Atomic, Molecular and Chemical Physics
• Optical Spectroscopy
• Laser Physics

Background:

• Cavity-enhanced spectroscopy utilizes optical cavities to enhance light-matter interactions.
• Cavity Ring-Down Spectroscopy (CRDS) is a common technique but requires fast signal detection.
• High absorption conditions pose challenges for traditional spectroscopic methods.

Purpose of the Study:

• Introduce and validate Cavity Mode-Width Spectroscopy (CMWS) as a complementary technique to CRDS.
• Demonstrate CMWS's ability to determine absorption coefficients without high-speed signal measurements.
• Showcase the application of CMWS for spectral line shape measurements.

Main Methods:

• Developed a cavity-enhanced spectroscopic technique based on measuring the spectral width of optical cavity modes.
• Employed an ultra-narrow laser system, specifically two phase-locked external cavity diode lasers (ECDLs).
• Utilized precise frequency control and tunability (± 20 GHz) for accurate measurements.

Main Results:

• Successfully measured the spectral line shape of the P7 Q6 O₂ line in the O₂ B-band.
• Demonstrated that CMWS determines absorption coefficients by measuring spectral width.
• Showcased the technique's applicability in the 687 to 693 nm wavelength range.

Conclusions:

• CMWS is a viable alternative to CRDS, particularly advantageous under high absorption conditions.
• The technique relies on precise laser frequency control and narrow linewidths.
• CMWS offers a valuable tool for absorption coefficient determination in various applications.