Optically Nonlinear Structures in Glass by Electron Lithography: Direct Writing

Abstract

Standard e-beam lithography system is used for writing a set of charged regions in glass, which provide patterned area possessing electric-field-induced quadratic optical nonlinearity. Patterned glass provides second optical harmonic generation (SHG) under a normal incident fundamental wave. Grating-like regions with periodicity from 2 to 32 μm demonstrate diffraction-like radiation patterns due to the interference of the second harmonic waves in the far-field radiation zone. Polarization studies of SHG using a grating of nonlinear regions allowed us to conclude that the Kleinman symmetry for the third order nonlinear susceptibility of isotropic media, χ_xxyy⁽³⁾_/χ_xxxx⁽³⁾ = χ_xyxy⁽³⁾_/χ_xxxx⁽³⁾ = 1/3, is valid with a high accuracy despite of the participation of DC electric field in the nonlinear interaction. A second harmonic radiation pattern can be specified by the geometry of a structure written by e-beam lithography.