We investigate the absorption spectra of poly (methyl methacrylate) (PMMA) thin films doped with Disperse Orange 11 (DO11) dye molecules which change under illumination with visible light. Dichroism measurements of the kinetics of the transmission changes at 472 nm at room and low temperatures (−60• C ± 2 • C) have been investigated. Our data show that the photoisomerisation reaction and the light-induced polar orientation depend on the molecular structure of the polymer. Simultaneous UV-visible spectroscopy at low temperature confirms the existence of two forms of DO11 molecules (keto and enol forms), which are responsible for the interaction with irradiating laser light and forming an anisotropic structure inside the PMMA/DO11 thin film.

We investigate the dichroism characteristics of poly (methyl methacrylate) PMMA thin films doped with DO11, DO3, DSR13 and DSR1 dye molecules, which change under illumination with visible light. Our data show that photoisomerisation, phototautomerization reactions and light-induced polar orientation are dependent on the molecular structure of the polymer. Polar structure and molecular size, as well as the chemical structure of PMMA host, are the dominant parameters that determine both the extent and speed of dichroism buildup and relaxation processes. Two forms of DO11 molecules (keto and enol forms), and two other forms of azo-based dyes (trans and cis forms) are responsible for the interaction with irradiating laser light and forming an anisotropic structure inside the PMMA/dye thin films.

A new experimental and theoretical method has been presented for measuring the refractive index of liquids and transparent solids. The experimental setup is based on a modified version of the Michelson interferometer employing a rotation stage. This technique allows us the determination of the refractive index of a given liquid (or a transparent sample) accurately to high precision, with an accuracy limited only by the precision in the determination of the rotation angle.

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