Formation of color centers in a soda-lime silicate glass by excimer laser irradiation

Abstract

We have investigated defect generation in soda-lime silicate and iron-doped soda-lime silicateglasses by excimer laser irradiation in order to apply coloration due to radiation-induceddefects as a coloring technique for practical glass products. The laser irradiationgenerated various kinds of defects, i.e., non-bridging oxygen hole centers (NBOHCs),E′ centers, and trapped electron centers, as does x-ray andγ-ray irradiation. The amounts of generated NBOHCs, monitored by the absorptionintensity, increased at first with the irradiation time for both the ArF and XeF lasers, andeventually became saturated. The saturated values for the ArF laser irradiation werealmost the same regardless of the laser intensity, whereas those for the XeF laserirradiation were dependent on the intensity; a higher intensity generated a largeramount of NBOHCs. From the comparison of the energies of the photon and theabsorption edge of the soda-lime silicate glasses, the defect generation reactions wereexpected to be one-photon and two-photon processes for the ArF and XeF lasers,respectively. In order to explain the defect generation behavior, we used a simple kineticmodel in which the NBOHCs are reversibly generated and annihilated through thephoto-reaction. The model includes a stretched exponential function, which is oftenobserved for reactions occurring in amorphous materials. The dependences of theamounts of the generated NBOHCs on the irradiation time and intensity of the laserpulses derived from the model were consistent with the experimental results.