Measurement of the effective optical path length of diffusing integrating cavities using time-resolved spectroscopy

Area of Science:

• Optics and Photonics
• Spectroscopy
• Materials Science

Background:

• Accurate measurement of effective optical path length (EOPL) is crucial for understanding light propagation in diffusing media.
• Existing methods may have limitations in characterizing complex scattering environments.

Purpose of the Study:

• To introduce and validate a novel time-resolved spectroscopic method for measuring EOPL in diffusing cavities.
• To demonstrate the method's capability across different port fractions and wavelengths.

Main Methods:

• Utilized a 710 nm short-pulsed laser (0.7 ns FWHM) as the light source.
• Analyzed temporal response curves to determine the time for uniform optical field establishment (approx. 4 ns).
• Calculated EOPL by selecting appropriate initial times based on light scattering events (5-6 times).

Main Results:

• Successfully measured EOPL for a diffusing cavity using the developed time-resolved spectroscopy method.
• Demonstrated the ability to obtain EOPLs for varying port fractions.
• Verified a previously reported theoretical EOPL law with experimental spectroscopic results.

Conclusions:

• The presented time-resolved spectroscopy method offers a reliable way to measure EOPL in diffusing cavities.
• This technique is applicable for characterizing optical properties at different wavelengths.
• The findings contribute to a better understanding of light transport in scattering media.