**6.2 FTIR measurement setup**

The adopted experimental setup takes full advantage of the original commercial FTIR measurement structure (Varian 2000 FT-IR) (Chen et al., 2008). The intended investigations are facilitated by putting an extra polarizer (Perkin-Elmer) in front of the detector and some predetermined number of optical attenuators (Varian) before the sample (see, Fig. 12). Figs. 13(a) and 13(b) show the detector calibration results under different numbers of attenuating sheets for both the p- and s-wave incidence, respectively. As is obvious, the detected intensities degraded linearly with the number of attenuators installed and the spectra remain morphologically similar.

Lightwave Refraction and Its Consequences: A Viewpoint of

interfacial jump of *E*|| as addressed by Eq. (26).

Microscopic Quantum Scatterings by Electric and Magnetic Dipoles 233

intensities (via using the above attenuator films) (Chen et al., 2008). Even though a PVDF film encompasses many double layers along its thickness, the reason the above theoretical derivations based on a single double layer (see Fig. 5) should still apply is that there are nonuniform vertical polarizations (or, electric fields) at the surface. In other words, the resultant gradients in the incident-light-responsive planar dipole moment would then render nonzero

Fig. 14. Experimental results on asymmetric reflection among conjugate light paths and

Since it is the reflectivity that is of interest, at each incident angle and under a specified degree of attenuation, the reflection is normalized with respect to the corresponding reference value in the absence of a PVDF film as shown in Fig. 13 (a) and 13 (b) (Chen et al., 2008). Figs. 14 (a) and 14 (b) illustrate the arising of asymmetric reflections between

enhanced reflectivity at different numbers of attenuators.

Fig. 13. Calibration on detected spectral effects when employing different numbers of attenuators under normal incidence of (a) p- and (b) s-polarized lights, respectively.

#### **6.3 Evidence of asymmetric reflections and enhanced reflectivities for attenuated incident lights**

In the reflectivity ( 2 2 *Rr E E* | | *r i* 0 0 ) experiments, each electrically-poled -PVDF film (thickness 16-18 m) is subjected to IR light irradiation at varying incident angles and beam

Fig. 13. Calibration on detected spectral effects when employing different numbers of attenuators under normal incidence of (a) p- and (b) s-polarized lights, respectively.

**6.3 Evidence of asymmetric reflections and enhanced reflectivities for attenuated** 

In the reflectivity ( 2 2 *Rr E E* | | *r i* 0 0 ) experiments, each electrically-poled -PVDF film (thickness 16-18 m) is subjected to IR light irradiation at varying incident angles and beam

Fig. 12. FTIR measurement setup.

**incident lights** 

intensities (via using the above attenuator films) (Chen et al., 2008). Even though a PVDF film encompasses many double layers along its thickness, the reason the above theoretical derivations based on a single double layer (see Fig. 5) should still apply is that there are nonuniform vertical polarizations (or, electric fields) at the surface. In other words, the resultant gradients in the incident-light-responsive planar dipole moment would then render nonzero interfacial jump of *E*|| as addressed by Eq. (26).

Fig. 14. Experimental results on asymmetric reflection among conjugate light paths and enhanced reflectivity at different numbers of attenuators.

Since it is the reflectivity that is of interest, at each incident angle and under a specified degree of attenuation, the reflection is normalized with respect to the corresponding reference value in the absence of a PVDF film as shown in Fig. 13 (a) and 13 (b) (Chen et al., 2008). Figs. 14 (a) and 14 (b) illustrate the arising of asymmetric reflections between

Lightwave Refraction and Its Consequences: A Viewpoint of

dimmer light is more outstanding than that of a brighter one.

detector. An incident angle range is scanned from 50.5°to 59.5°(

0.015°, and then its conjugate range from -50.5°to -59.5°(

Fig. 16. Configuration of PVDF Brewster angle measurement.

Parameters Beam

Poled- PVDF

Table 1. PVDF Brewster angles measurement.

**7. PVDF experiment on varying Brewster angle** 

**7.1 PVDF new Brewster angle**

withdrawing from the beam path.

data are given in Table 1.

Microscopic Quantum Scatterings by Electric and Magnetic Dipoles 235

features strongly endorse the above theoretical claim that the reflectivity variation of a

The experimental set up is as arranged in Fig. 16, where a light beam of 0.686 mm radius from the He-Ne laser (of the wavelength of 632.8 nm) is converted into p-wave mode after getting through the polarizer (Tsai et al., 2011). Two double convex lenses, with focal lengths being 12.5 cm and 7.5 cm, respectively, are for shrinking down the beam radius to 0.19 mm to reduce the width of light reflection off the PVDF surface. The reflected light is then further focused by a lens (of 2.54 cm focal length) before reaching the diode power

intensity is varied between 100% (8.54 mW) and 10% power by moving an attenuator into or

The fitted curves for the measured Brewster angles for the two conjugate incident paths, under 100% and 10% laser beam intensities, on both the - and poled- films, are shown in Fig. 17 and Fig. 18, respectively (Tsai et al., 2011). It can be seen that Brewster angles measured via the two conjugate incident paths differ considerably. Such difference becomes more outstanding on the poled- PVDF film, and in particular, when the laser beam is attenuated to 10%, as predicted by the theory of the authors (Liao et al., 2006). The typical


 ( ) *B i* 

54.695° 10 % 55.3875° 0.6925°

 54.62° 100 % 55.77° 1.05° 54.38° 10 % 56.245° 1.865°

*<sup>B</sup>*

intensity ( ) *B i* 

*<sup>i</sup>* ) with an accuracy of

*<sup>i</sup>* ), while the incident light

conjugate incident paths (e.g., incidence at 30 versus 330) for both the p- and s-polarized infrared lights under various degrees of intended attenuation (Chen et al., 2008). In the above, the incident angle is defined by rotating clockwise the poled-PVDF sample under top-view of the setup of Fig. 12. Hence, reversing the light reflection path indeed causes a different reflected power to arise, as predicted by the aforementioned theoretical exploration. Note that, however, in traditional FTIR measurements, decrease in the detected intensity has been routinely attributed to increased absorption by PVDF films. Nevertheless, for an obliquely incident light the beam path within PVDF is only slightly larger than that in a normal incident situation. Thus, the resultant infinitesimal increase in PVDF absorption should never be sufficient to account for the detected large difference in reflected power. Notably, the detected decrease in intensity should instead be attributed to enhanced reflection caused by distributed dipoles on the poled PVDF films.

Fig. 15. Observed distinct asymmetric reflection among conjugate light paths under two attenuator films and at varying incident angles.

Furthermore, for both p- and s-polarized incident waves, the variations in reflectivity are more significant in the situations where more attenuation is imposed, complying with the above theoretical expectation. Namely, the second terms in the above-derived Eqs. (28) and (29) are more enhanced under the situation of smaller incident light electric field (or power). Lastly, even though the appearance of FTIR-detected spiky saturation peaks in Figs. 14 (a) and 14 (b) actually imply loss in the signal-to-noise ratios when under heavy attenuation of the incident power, several unsaturated features, e.g., in Figs. 15(a) and 15(b) still remain (wherein 2 sheets of attenuators are employed) (Chen et al., 2008). Such evidenced spectral features strongly endorse the above theoretical claim that the reflectivity variation of a dimmer light is more outstanding than that of a brighter one.
