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Optically Nonlinear Structures in Glass by Electron Lithography: Direct Writing
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 diffractionlike 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, χxxyy(3)/χxxxx(3) = χxyxy(3)/χxxxx(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.