Quantitative Determination of Sources of the Electro-Optic Effect in LiNbO3 and LiTaO3

Phys. Rev. 160, 519 – Published 15 August 1967
I. P. Kaminow and W. D. Johnston, Jr.

Abstract

The electro-optic effect in crystals can be separated into two types of microscopic interaction: an electron-lattice contribution in which the applied field produces a lattice displacement, which in turn modifies the electronic polarizability (or refractive index), and a direct electron-field contribution in which the applied field modifies the electronic polarizability in the absence of lattice displacements. The latter contribution in LiNbO3 and LiTaO3 can be estimated from second-harmonic-generation experiments by Miller and Savage, and accounts for less than 10% of the refractive-index change. Each polar-lattice optic mode in LiNbO3 and LiTaO3 (4A1+9E) contributes separately to the electro-optic effect an amount proportional to the product of its Raman-scattering efficiency and infrared oscillator strength. We have measured the absolute scattering efficiencies for LiNbO3 and LiTaO3. The oscillator strengths for LiNbO3 have been measured by Barker and Loudon. We find that the dominant contribution to the electro-optic coefficients r33 and r13 comes from the lowest-frequency A1 mode; and to r42 and r22 from the next lowest E mode. These same modes dominate the low-frequency dielectric constant. The absolute values of r13, r33, r42, and r22 calculated from the combined Raman, infrared, and second-harmonic-generation data are in excellent agreement with the electro-optic coefficients measured directly by Turner. In addition to the absolute scattering efficiencies for all the transverse and longitudinal modes in LiTaO3 and LiNbO3, we have also determined the mode frequencies and linewidths, which are important in calculating Raman gain.

DOI: http://dx.doi.org/10.1103/PhysRev.160.519

  • Received 27 March 1967
  • Published in the issue dated August 1967

© 1967 The American Physical Society

Authors & Affiliations

I. P. Kaminow and W. D. Johnston, Jr.

  • Bell Telephone Laboratories, Crawford Hill Laboratory, Holmdel, New Jersey

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