## 4 Conclusions  
This paper offered a robust approach for accurately measuring the dispersion curve of polycrystalline PMN-PT based on interference patterns in FTIR spectroscopy in a wide range of optical wavelengths for the first time. The dispersion curve was used to define the transmission of this ceramic. The dielectric constant of the PMN-PT ceramic was defined as a function of temperature through a capacitance bridge configuration and a high-accuracy LCR meter. The Curie temperature of PMN-PT ceramic was found close to the room temperature, where the dielectric constant peaks at about 12,000. A polarization-independent EO laser beam steerer based on a 7.5 mm \(\times\) 7.5 mm \(\times\) 40 mm polycrystalline PMN-PT was designed in this study to steer light from visible to mid-IR. The optimum number of interfaces for this EO beam steerer was found as two, considering no internal reflection and minimum partial back-reflections. The only EO beam steerer that does not need crystalline orientation adjustment so far was the one offered by [PERSON] from NTT Photonics Laboratories in Japan [7]. However, since that steerer was based on charge injection and it is impossible to inject charges to a thick medium uniformly, the medium must be a fraction of a millimeter thick. Therefore, that EO steerer could steer only an 80 \(\upmu\)m laser beam and resolved only 20 spots. For the first time, this paper offered an EO beam steerer, which was similarly polarization-independent and did not need any crystalline orientation adjustment, but it could resolve \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Deflection (mrad.mm/kV)**} \\ \hline
**Wavelength (\(\upmu\)m)** & **LiTaO\({}_{3}\)** & **Polycrystalline PMN-PT** \\ \hline
0.633 & 9.41 & 61.6 \\
1.55 & 7.78 & 54.88 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparing the performance of polycrystalline PMN-PT to LiTaO\({}_{3}\) in deflection light at visible and near-IR. Figure 23: The phase retardance versus applied electric field on PMN-PT ceramic for four wavelengths (532, 633, 1550, and 4500 nm). up to 1400 spots. The voltage per millimeter applied on the EO medium in this paper was only two times more than the one presented by [PERSON], but the number of the resolvable spots was 70 times more. The deflection angle for the wavelengths of 532, 632.8, 1550, and 4500 nm was measured in the lab in terms of mrad\(\cdot\)mm/kV at 25 \({}^{\circ}\)C and 40 \({}^{\circ}\)C temperatures to define the EO coefficients associated with those four wavelengths at two different temperatures for the first time. The calculated EO coefficients, refractive indices, transmission, and dielectric constant were used as inputs of a simulation model developed with COMSOL Multiphysics. The simulation model was used to calculate the voltage and electric field distribution as well as the birefringence. The EO beam steerer's performance, including the deflection angles, was simulated and compared to the measured values. The EO coefficients and the refractive indices were used to define the halfwave electric field, and the results were compared to the measured values. The phase retardance associated with those four wavelengths was determined. The results show that the EO coefficient of PMN-PT ceramic is not strongly varying by the temperature, but it drops from 15.68 \(\times\) 10\({}^{-16}\) for green laser (532 nm) to 2.18 \(\times\) 10\({}^{-16}\) for mid-IR (4500 nm). That significant drop in the EO coefficient reduced the number of resolvable spots of the EO beam steerer, developed in this study, from 1403 to 23. Although the result shows the EO coefficient of bulk PMN-PT ceramics is an order of magnitude smaller than gold nanoparticles measured by [PERSON] and [PERSON] [8] at 633 nm, the bulk PMN-PT offers other benefits like higher transmission at mid-IR, very low thermal dependency, less EO dispersion and ability to address larger apertures.