New Beam Scanning Model for High-Speed Operation Using KTa$_{1-x}$Nb$_{x}$O$_{3}$ Crystals

Abstract

We propose a new beam scanning model that is applicable to electrooptic materials with electron traps. With this model, we can achieve both high-speed operation and wide-angle scanning, because the operating speed is limited not by the electron mobility but by the frequency limit of the electrooptic effect of the materials. The voltage dependence of the scanning angle at 100 kHz using a KTa1-xNbxO3 crystal is consistent with the property predicted by the proposed model.

Injected-charge-driven increase in electro-optic effect of KTN crystals

“…Moreover, our results in this paper will lead to modification of the previous model of beam scanning. 11 In the previously model, it was assumed that the dielectric constant did not change before and after applying high voltage. We consider the densities of the trapped electrons must be overestimated in the previous model because they were obtained only from equation (1) using the dielectric constant before applying high voltage.…”

“…9,10 We have recently reported a KTN EO beam scanner that employs a new beam scanning model and demonstrated fast beam scanning using the KTN crystal. 11 Beam scanning was realized as a result of the electric field distribution resulting from the trapped electrons. With this model, we can achieve high-speed beam scanning because the operating speed is limited by the frequency limit of the EO effect of the materials rather than by the electron mobility.…”

Electro-optic and Acousto-optic Laser Beam Scanners

“…This specific distribution is attributed to "trapped charges" inside the crystal, as a result of electrons injected into the crystal from the electrodes (Miyazu et al, 2011). This effect was referred to as the space-charge effect and is superimposed on the Kerr effect (Nakamura et al, 2008(Nakamura et al, , 2006Naganuma et al, 2009). Assuming the laser beam enters the crystal along the optical axis of the crystal, see Fig.…”

Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] KTN crystal, a perovskite-type oxide material, well recognized for its excellent EO performance where the index modulation is proportional to the square of the electric field, can realize rapid response, strong control of the refractive index and much lower driving energy comparing to LiNbO 3 for the same change ∆n in the refractive index. For this reason, KTN-based single crystal has been considered as promising materials, and has then been substantially investigated and successfully exploited in such diverse areas as EO deflection, [6][7][8] EO scanner, 9 a fast varifocal lens [10][11][12][13] and so on. 14,16,17 Mn:Fe:KTN crystal doped with both iron and manganese simultaneously are of particular interest because of its two competing subsystems of dipole moments and exhibits faster EO response than single-doped crystal.…”