Localisation of the induced second-order non-linearity within Infrasil andSuprasil thermally poled glasses

Spatial Maker fringe experiments have allowed us to render evident large di fferences in the shape of the second-order chi((2)) susceptibility, induced by thermal poling, in Infrasil and Suprasil silica plates. To determine mo re accurately the spatial repartition of the induced chi((2)), two methods were used. The first one consists of increasing the pump beam internal angl e span by placing a pair of hemispherical lenses against both sides of the poled plates. The second consists of polishing the plates and then measurin g the second harmonic power generated within the samples. We explain all th e experimental observations by the existence of a bulk chi((2)) within the whole volume of Suprasil poled glass. (C) 2000 Elsevier Science B.V. All ri ghts reserved.