Anisotropy of acousto-optic figure of merit for LiNbO_3 crystals: anisotropic diffraction

Abstract

We have developed a method for the analysis of anisotropy of an acousto-optic figure of merit (AOFM), which is valid for the case of anisotropic diffraction in the trigonal crystals of the point symmetries 3m, 32, and 3¯m. The method is verified via the example of LiNbO₃ crystals. The relations for the effective elasto-optic coefficients and the AOFM are obtained for the three types of acousto-optic (AO) interactions peculiar for the anisotropic AO diffraction: the interaction of a so-called type VII with a quasi-longitudinal acoustic wave and the interactions of types VIII and IX with two quasi-transverse acoustic waves. The AO diffraction geometries providing maximal AOFM values have been determined for each of the mentioned interaction types. We have found that the maximum AOFM proper for LiNbO₃ is equal to 15.9×10^-15 s³/kg. This value is achieved at the type IX of AO interactions in the interaction plane rotated by 60.0 deg around the principal X axis with respect to the principal X-Z plane. The type VIII of AO interactions is characterized by a comparable AOFM (15.1×10^-15 s³/kg), which is realized in the Y-Z interaction plane. A close comparison of our results with the available experimental data demonstrates their fairly good agreement.

The anisotropy of acoustooptic figure of merit for the collinear diffraction in LiNbO3 crystals

“…[15,16] for the trigonal crystals that belong to the symmetry groups 3m, 32 and 3m . One of the mirror symmetry planes in LiNbO 3 is perpendicular to the crystallographic axis a [17], while the c axis is parallel to the three-fold symmetry axis.…”

“…The relations for the EEC suitable for the anisotropic diffractions have been derived elsewhere [15,16]. They correspond to the interactions with quasi-longitudinal (QL) and two quasi-transverse (QT 1 and QT 2 ) waves.…”

“…These interactions correspond to so-called types VII, VIII and IX, respectively (see in Refs. [15,16]). The wave QT 1 is polarized in the interaction plane XZ parallel to the Z axis, and the polarization of the wave QT 2 is perpendicular to this plane.…”

Anisotropy of acoustooptic figure of merit in KH2PO4 crystals

“…After that we rotate our interaction plane around Z and X axis (see, e.g., Refs. [23][24][25]). For the interaction planes rotated by some angle Z  around the Z axis or by X  around the X axis (i.e., in the new coordinate system X Y Z   ), the structure of the elastic stiffness tensor is changed.…”

“…Recently we have developed a general method that allows for determining those directions of propagation and polarization of the optical and acoustic waves (AWs) which ensure maximal AOFM magnitudes [19][20][21][22][23][24][25]. In particular, TeO 2 , LiNbO 3 , -BaB 2 O 4 , NaBi(MoO 4 ) 2 and some others crystals have been studied as examples.…”