Giant Enhancement of Optical Second Harmonic in Poled Glasses by Cold Repoling
For the first time, we demonstrated that additional poling at room temperature (cold repoling) of a soda-lime glass thermally poled in open anode configuration causes an increase of the optical second harmonic signal by more than an order of magnitude. Performed experiments allow relating this increase in the optical nonlinearity of the glass to the orientation of hydrogenated dipoles in the vicinity of the glass surface. This indicates that both frozen electric field and dipole orientation are responsible for the nonlinearity of thermally poled alkali-containing glasses. Observed dipole orientation in glasses is of interest for molecular physics and electrodynamic studies.