Penetration of Silver Granules into Quartz Glass Under Powerful Laser Beam Action

We investigated the granular silver films deposited on the surface of quartz glass plate, and found that silver granules penetrate into pores of the quartz, when irradiated by a powerful laser beam (we used a CO₂-laser, lambda= 10.6 mum power P = 8 W). The penetration is caused, firstly, by melting of silver because of heating, and secondly, by a photoeffect on silver granules and capture of electrons by traps of the quartz, plate. The electrostatic field leads to migration of Ag ions into the surface layer of quartz. We investigated the dependence of properties of the waveguide on beam exposition. The measurements of reflection coefficient and refractive index reveal that a step-type waveguide (for red and infra-red light) is created under the surface of quartz. Also we investigated the absorption band of a colloidal solution of Ag in quartz. The band's position reveals that silver occupies less than one tenth of waveguide volume. Typical granule radius inside quartz is 3 nm. It is revealed with microphotographs