Molecular χ(2) gratings via electron-beam lithography

Abstract

We show that the nonlinear optical activity of an organic molecule may be quenched by electron irradiation. Exploiting this effect, we inscribe periodic ͑2͒ patterns in the molecular films by means of a scanning electron microscope. The second harmonic diffraction efficiency of the resulting ͑2͒ gratings is measured. The relative intensity of the diffraction orders observed agrees with the expectations for a sheet of nonlinear dipoles with a periodic modulation. No linear diffraction is seen. The present method allows realizing any type of two-dimensional ͑2͒ pattern with a resolution only limited by the electron beam patterning capabilities.

Surface Nonlinear Gratings by Direct Multiphoton Microscope Writing

“…It has been demonstrated with 6 ns frequency doubled mode‐locked Nd:YAG lasers forming an interference pattern, and with 100 mW from a CW krypton laser at 530.9 nm . Electron‐beam lithography is central in nanotechnology because of the level of control that it offers, for total or partial desorption of several types of organic films . Controlling the temperature and electron kinetic energy allows for partially damaging the molecular composition or for inducing reactions selectively; however, with these techniques, one usually has to move the sample in order to image the recorded region.…”

“…Equivalently, it can be shown that the position of the m order of diffracted second harmonic is given by: …”

“…[8] One key idea in the study of surface nonlinear interactions is that the optical layer interactions should be independent of the substrate. [9][10][11][12] Several optical nonlinear effects from fluorescent or nonfluorescent chromophores deposited as molecular films have been demonstrated; [13][14][15][16][17][18][19][20][21][22] specifically, the surface nonlinear diffraction. [13][14][15][16][17] Nonlinear optical interactions allow new and exciting possibilities for applications even when the linear optical response is uninteresting.…”

“…[9][10][11][12] Several optical nonlinear effects from fluorescent or nonfluorescent chromophores deposited as molecular films have been demonstrated; [13][14][15][16][17][18][19][20][21][22] specifically, the surface nonlinear diffraction. [13][14][15][16][17] Nonlinear optical interactions allow new and exciting possibilities for applications even when the linear optical response is uninteresting. Surface nonlinear diffraction through homogeneous periodical patterns inscribed onto the molecular films can be exploited for recording nonlinear gratings in waveguides; coupling into waveguide structures, microresonators or plasmonic devices; another advantage is the faster acquisition times, thus preventing sample degradation.…”

Nonlinear optics in spheres: from second harmonic scattering to quasi‐phase matched generation in whispering gallery modes

“…When the nonlinear material is only covering the surface of the resonator it is, in principle, possible to achieve a periodic grating with the correct pitch. Recently, it was shown that the nonlinearity of molecular layers deposited on a flat surface could be quenched at will using an electron beam gun [70]. Exploiting this effect, periodic χ (2) patterns were inscribed on flat molecular films by means of a scanning electron microscope.…”