Measuring the infrared absorption in thin film coatings

Area of Science:

• Materials Science
• Optics
• Thin Film Technology

Background:

• Traditional methods for measuring thin dielectric film optical absorption rely on comparative techniques.
• These methods involve comparing coated and uncoated substrates, which can introduce inaccuracies.

Purpose of the Study:

• To develop a direct measurement technique for optical absorption in thin dielectric films.
• To eliminate the need for comparative or difference methods in absorption measurements.

Main Methods:

• A novel laser calorimetric technique was employed using long, bar-shaped samples.
• The method distinguishes between surface and bulk heat generated by laser absorption.
• Absorption coefficients were extracted from the temperature-time curve slopes.

Main Results:

• The developed technique successfully determined the optical absorption coefficient for single-layer films.
• Films of As(2)S(3), CaF(2), ThF(4), and PbF(2) on a KCl substrate were analyzed.
• Direct measurement of film absorption was achieved without comparative analysis.

Conclusions:

• The new laser calorimetric approach provides a direct and accurate method for measuring thin film optical absorption.
• This technique simplifies the measurement process by avoiding comparative substrate analysis.
• The method is applicable to various dielectric film materials.