Giant enhancement of the second harmonic generation efficiency in poled multilayered silica glass structures

Multilayered thin-film doped silica structures are experimentally demonstrated as an effective tool to enhance the second-order nonlinear properties induced in thermally poled glass devices. A 204-fold improvement is obtained in the second harmonic generated (SHG) in a poled structure with a 3 μm-thick multilayered stack consisting of sub- 100 nm-thick alternating germanium-doped and undoped silica layers compared to poled bulk silica glass. The induced nonlinearity is localized within the layered region, indicating that the multilayered design can be used to precisely control the thickness and the location of the nonlinearity. Such artificial nonlinear structures can be used to overcome the main limitations of existing poled glass devices, therefore opening the door to practical implementations of efficient active devices in silica glass.