Electro-refraction and electro-absorption in poled polymer Fabry–Perot étalons

Abstract

Poling and orientational relaxation: Comparison of nonlinear optical mainchain and sidechain polymers Photorefractive composite materials with bifunctional charge transporting secondorder nonlinear optical chromophores Large nonbiased alloptical bistability in an electroabsorption modulator using pinip diode and asymmetric Fabry-Perot cavity structureWe present a simple experimental procedure that uses a slowly rotating étalon to measure simultaneously the electro-refraction and electro-absorption in a poled polymer. Both effects generally contribute to the measured signal from such material systems and can be distinguished by rotating the sample and observing asymmetric peaks in the signal. The experimental results show the expected increase in both electro-refraction and electro-absorption as the probe wavelength approaches the absorption band of the chromophore. Furthermore, the dispersion of the complex electro-optic coefficient displays a periodic variation that we attribute to multiple-étalon interference. The stratified nature of the thin-film structure causes the multiple-reflection interference. This artifact will pollute most of the standard electro-optic characterization techniques for poled-polymer films.

Simplified Reflection Fabry-Perot Method for Determination of Electro-Optic Coefficients of Poled Polymer Thin Films

“…Eldering et al [12] demonstrated the use of a transmission mode FP etalon with angle scanning at a fixed wavelength to study second-order nonlinear properties of polymer materials by fitting numerical data based on a relatively simple analysis of the multilayer structure requiring two semitransparent electrodes. O'Brien et al [13] introduced a variation of the transmission FP technique using a thick glass substrate. The use of FP analysis was later applied by Pretre et al [14] to decal-deposited reflection FP structures in order to measure complex linear optical and electro-optic parameters as well as to characterize the inverse piezoelectric contribution.…”

“…Equations (9), (11), and (12) are all that is needed to determine r 13 and r 33 in this simplified model. In the next section, we explore the validity of using Equation (6) for the practical multilayer structure of Figure 2(b).…”

“…In addition, these interferometric methods require careful aligning of the signal and reference beams and the interference pattern is susceptible to drift. Although the Mach-Zehnder method can be used to determine both r 13 and r 33 , the Michelson method can only measure r 13 and a separate experimental technique must be used to get r 33 . The modified attenuated total reflection (ATR) method [9,10] can also measure r 13 and r 33 separately, without an assumption for the value of the ratio r 13 /r 33 as required in both the simple and rigorous Teng-Man reflection methods [2][3][4].…”

“…A large area infrared photo-detector is used to detect reflected light over a wide range of angles of incidence in order to collect angular data without the need for the rotation stage used in [14] to maintain alignment as the laser source arm rotates. In order to analyze the experimental data for determination of the two independent EO coefficients r 13 and r 33 of poled polymer thin films, we consider the phase condition for reflection minima for two different FP resonator structures shown in Figure 2: (a) the idealized simple three layer structure (air/NLOP/air) and (b) the multilayer structure (glass/TCO/NLOP/metal). We first use the mathematical expression for reflectivity to discuss the phase condition from the simple three layer structure, which can be found in most optics textbooks [15].…”

“…Finally the EO coefficients r 13 and r 33 are obtained using (12) where V is the peak applied voltage to the film, and n o , n e , and d 3 are the separately measured anisotropic indices and thickness of the NLOP film. Figure 3.…”