SIMULATION OF THE DEGRADATION OF OPTICAL-GLASS SUBSTRATES CAUSED BY UV IRRADIATION WHILE COATING

The radiation induced degradation of optical glass substrates during t hin film deposition, which has been shown previously, is studied using simulation. Influence of UV irradiation by spectral lamps and excimer laser on fused silica acid borosilicate glasses is investigated. Phot othermal deflection is used to measure the increase in BK7 absorption versus time during UV irradiation. We also study means permitting a cu ring of UV induced absorption: first thermal annealing, and second foc using a visible laser beam onto the irradiated area. The results show that UV radiation can be responsible for an important part of substrat e absorption increase while coating, (C) 1998 Elsevier Science B.V.