Corona poling and real-time second-harmonic generation study of a novel covalently functionalized amorphous nonlinear optical polymer

Abstract

Thin films for optical second-harmonic generation (SHG) were prepared from a newly designed and synthesized amorphous polymer that incorporated a high density of active nonlinear optical groups (p-nitroaniline as attached side groups). For alignment of the nonlinear groups a very high electric field was applied by a corona discharge to the polymer films above Tg (125 °C). The subsequent freezing process resulted in a polymer film initially exhibiting a very high second-order nonlinear coefficient, d33=31 pm/V, measured by the Maker-fringe technique, plus excellent thermal, mechanical, and optical properties. The dynamics of polar alignment and decay, studied by in situ poling (or depoling) and SHG measurements, indicated a multiple exponential behavior with the average relaxation time somewhat longer than expected from extrapolation of the dielectric relaxations data according to the Williams–Landel–Ferry equation. The frozen-in SHG behavior at room temperature (∼100 °C below Tg) relaxed after 5 days to a stabilized value of 19 pm/V for d33.

Nonlinear Optical Susceptibility of a Model Guest-Host Polymeric System as Investigated by Electrooptics and Second-Harmonic Generation

“…The measured d. 3 and r,, are shown in Fig.3 Table I). To determine the value of Ep, we used the film thickness data, determined from the waveguiding experiment using the Metricon, which simultaneously provides the refractive index and film thickness data.…”

“…The AC field is along the 3-axis. The coefficient r. 3 interfaced to a PC. The sample assembly mounted on the goniometer stage was placed in an oven which is temperature controlled to the accuracy of ± 0.5 0 C. The electric field poling was carried out inside the temperature controlled oven.…”

Second harmonic generation in partially ordered media and at interfaces: analysis of dynamical and orientational factors

“…In situations where such isotropy can be removed or is naturally lacking, SHG is allowed and can hence provide a very sensitive tool for detecting preferential molecular orientation. For example SHG has been used to gauge molecular orientation: at fluid interfaces [2,3]; within cell membranes [4,5]; of dipolar chromophores in poled polymers [6,7] and of molecules within molecular sieves [8]. In circumstances where preferential orientation arises, theory requires the application of suitably weighted three-dimensional rotational ensemble averages in order to arrive at the nett media response.…”

Dipolar interaction assisted effects on second harmonic generation

“…The technique of corona poling was also used to obtain higher orientation of the chromophores. This technique is similar to that employed by Eich et al 6 The glass transition temperatures of the samples were determined by a DSC (Perkin Elmer Delta series). The refractive indices of the samples were determined by a prism coupler (Matricon) modified for the multiple wavelength operation.…”