| Abstract |
In the present study, the photosensitivity of phosphate glass to ultrashort, ultraviolet laser radiation is demonstrated. The glass material that was studied, is named IOG-1 Er/Yb codoped, and is fabricated from Schott, USA. The study of its photosensitivity was performed in three steps.
During the first step, samples were irradiated with a KrF laser working at a wavelength of 248nm and for three different pulse durations 120fs, 500fs and 5ps. By performing spectrophotometric measurements on the UV irradiated samples, their absorption spectra were recorded. By applying the Kramers-Kronig theoretical model to these spectra, the changes of refractive index due to the creation of color centers in the volume of the exposed material, were calculated. The induced color centers were identified by analyzing the absorption spectra in Gaussian bands, and their concentrations were calculated by using Smakulas formula. In order to identify the changes induced in the optical absorption gap of the irradiated samples, the theory of Davis and Mott was applied. Furthermore in order to enhance our understanding on the induced structural changes, micro-Raman measurements were performed. From the up-mentioned results, conclusion could be done about the changes induced in the chemical order of the material.
In the second step, in order to examine the photosensitivity mechanisms further and to improve our understanding of defect formation, 1-dimensional Bragg gratings were inscribed into the glass matrix. For that procedure, ultrashort pulses from a KrF laser emitting at 248nm, and for pulse duration of 120fs, 500fs, 5ps were used again. By measuring the diffraction efficiency of the gratings, the total refractive index changes were calculated and compared with these estimated from the Kramers-Kronig relationship. Refractive index changes calculated from the Kramers-Kronig technique and from the diffraction efficiency measurements was up to 4*10-4 and 8*10-5 each.
As a third and final step, in order to examine if photo-induced changes would affect the mechanical properties of the material, Knoop Hardness measurements were performed. These measurements were performed on samples irradiated with ΚrF laser emitting at 248nm, and for pulse duration of 120fs, 500fs, 5ps. Finally by using the Knoop Hardness measurements and by applying Marshall theoretical model, changes on the elastic modulus of the irradiated samples were determined.
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Μελέτη των οπτικών και δομικών ιδιοτήτων της φωσφορικής υαλώδους μήτρας IOG1 έπειτα από έκθεση σε ακτινοβολία υπερβραχέων παλμών υπεριώδους λέιζερ
