A White Light Interferometric Microscope for Measuring Dose-Dependent Reversible Photodegradation

TL;DR

This paper introduces a white light interferometric microscope capable of spatially resolving changes in the complex index of refraction, enabling detailed study of reversible photodegradation in doped polymer materials.

Contribution

The development of a WLIM that measures spatially resolved complex refractive index changes during photodegradation, validated against spectroscopic data and models.

Findings

Measured change in absorbance consistent with spectrometer data

Refractive index change aligns with Embaye's model

WLIM effectively images optical property changes

Abstract

We have developed a white light interferometric microscope (WLIM), which can spatially resolve the change in the complex index of refraction and apply it to study reversible photodegradation of 1,4-Diamino-9,10-anthraquinone doped into (poly)methyl methacrylate. The measured change in absorbance is consistent with standard spectrometer measurements. The refractive index of a pristine sample measured with the WLIM is also found to be consistent with the spectrum found by independent means (F. Yakuphanoglu and B. Senkal, Electrical conductivity, photoconductivity, and optical properties of poly(1,4 diaminoanthraquinone) organic semiconductor for optoelectronic applications, Polym. Adv. Technol. 19, 1193 to 1198 (2008)). We report on measurements of the change in refractive index due to photodegradation, which is found to be consistent with Embaye's two population model (N. Embaye et al., Mechanisms of reversible photodegradation in disperse orange 11 dye doped in PMMA polymer, J. Chem. Phys. 129, 054504 (2008)). We show that the WLIM can be used as a powerful tool to image the complex refractive index of a planar surface and to detect changes in a material's optical properties.