Possibility of diagnostics of the prebreakdown state in the surface region of a solid transparent dielectric based on the broadening of the spectrum of a giant pulse and on the change in the Brewster angle

An analysis is made of the influence of the absorption of energy by the surface of a transparent dielectric on the damage to the ends of this dielectric under the action of a giant laser pulse of nanosecond duration. It is shown that an electron avalanche in a surface layer ~1 μ thick due to the surface absorption develops much more rapidly than in the bulk. Calculations are made allowing for the threshold of electron avalanche multiplication. It is shown theoretically that a transmitted giant pulse suffers a frequency shift Δω, due to the development of an electron avalanche, and a change in the Brewster angle Δθ_B due to an increase in the electron density in the surface layer of the dielectric. An experimental method is proposed in which the values of Δω and Δθ_B are used to determine the avalanche multiplication threshold and the avalanche growth time.