Light-induced second-harmonic generation in glass via multiphoton ionization

Abstract
Irradiating glass by intense light at frequencies ω and 2ω generates a semipermanent dc electric field in the glass that transforms the glass into a phase-method optical-frequency doubler. We map out this dc electric field over a wide variety of experimental conditions. We show that its symmetries are predicted by a theory based on the interference of competing multiphoton ionization channels.