Reversible and irreversible alterations of the optical thickness of PQ/PMMA volume recording media samples. Part I: Experiment.

Experimental research into changes of the optical thickness of phenanthrenequinone-doped polymethyl methacrylate samples in the process of irradiation by a 473 nm laser is presented. It was demonstrated that heating-induced reversible changes lead to a decrease in the optical thickness. The temperature coefficient of the relative changes of the optical thickness was measured to be -1.40×10-5  К-1, which matches the data published by other authors. It is also established that the irreversible changes induced by the photochemical transformation lead to an increase in the optical thickness outside of the absorption band of the samples (λ>530  nm), where the relative change of which at λ=532  nm is +3.7×10-5. It was demonstrated that the reversible and irreversible changes do not compensate for each other in the process of sample exposure.