Intracavity absorption with a continuous wave dye laser: quantification for a narrowband absorber

Area of Science:

• Spectroscopy
• Physical Chemistry
• Laser Physics

Background:

• Intracavity absorption is a highly sensitive detection method but faces limitations in application due to concerns about nonlinearity, experimental complexity, and reliability.
• Previous research has highlighted challenges in applying intracavity absorption to fields like chemical kinetics and photochemistry.

Purpose of the Study:

• To address concerns regarding the reliability and applicability of intracavity absorption.
• To experimentally investigate the dependence of intracavity absorption on key parameters like transition strength, concentration, absorber path length, and pump power.
• To validate the Beer-Lambert relationship within the intracavity absorption technique.

Main Methods:

• Utilized a continuous-wave (cw) dye laser system with a narrowband absorber, specifically nitrogen dioxide (NO2).
• Quantitatively measured the extent of intracavity absorption directly from the dye laser's spectral profiles.
• Compared intracavity absorption measurements with traditional extracavity measurements.

Main Results:

• Confirmed a Beer-Lambert type relationship for intracavity absorption over a practical range of parameters.
• Observed significant enhancements in absorption sensitivity, reaching up to 12,000 times compared to extracavity measurements, particularly near the lasing threshold.
• Successfully defined an intracavity absorption coefficient.

Conclusions:

• Demonstrated the reliability and practical utility of intracavity absorption for quantitative measurements.
• The technique, when properly characterized, offers substantial sensitivity enhancements valuable for chemical kinetics and photochemistry.
• Accurate transition strength ratios were obtained, validating the method's precision.