E. G. Spencer

ELECTRO‐OPTIC COEFFICIENTS OF FERROELECTRIC STRONTIUM BARIUM NIOBATE

Linear electro‐optic coefficients as large as r ∼ 4 × 10‐5 cm/statvolt have been measured in the system of ferroelectric strontium barium niobates, SrxBa1‐xNb2O6. In the first crystals x varies from 0.75 to 0.25, with Curie temperatures ranging from ∼60°C to 250°C. At 15 Mc, the respective half‐wave field distance products range from 48 to 1236 V.

Dielectric materials for electrooptic, elastooptic, and ultrasonic device applications

In order to realize the advantages of using lasers for communications, means must be obtained to modulate with sufficient bandwidth and capacity, deflect, switch, frequency translate, or otherwise effect a modification of the optical beam in a predictable manner. This problem has provided the incentive for extensive materials research directed toward the development of any crystal capable of low-loss optical transmission whose properties can be modified by an electric or magnetic field or applied external stress, and whose properties, at the same time, will interact in some specified manner with the optical beam. In this paper some dielectric materials for these uses currently in various stages of development will be described.

Electro-Optic Coefficients in Single-Domain Ferroelectric Lithium Niobate

This paper presents the results of measurements by the Senarmont compensator method of the dc electro-optic coefficients at a wavelength of 6328 A and observations of electro-optic modulation at radio frequencies in single-domain crystals of lithium niobate (LiNbO3), a trigonal crystal of point group 3m. Tables of electro-optic properties and measurements are included, as well as a series of optical interference figures for various static field conditions. The magnitudes of the dc coefficients were found to be r22=2.0×10−7 cm/statvolt and |0.9r33−r13|=5.2×10−7 cm/statvolt.

ULTRASONIC PROPERTIES OF BISMUTH GERMANIUM OXIDE

Temperature dependence of the elastic wave losses is reported for bismuth germanium oxide, Bi12GeO20, a strongly piezoelectric crystal of point group 23. At 296°K and at 500 Mc/sec the attenuation, Γ, is 0.11 dB/μsec and at 118 Mc/sec is 0.008 dB/μsec. At 4.2°K and at 500 Mc/sec, Γ is 5 × 10−4 dB/μsec and at 118 Mc/sec is 2.7 × 10−4 dB/sec. At intermediate temperatures five loss peaks are observed, the origins of which as yet have not been determined. A shear wave velocity and the longitudinal wave velocity in the [110] direction are 1.77 × 105 and 3.42 × 105 cm/sec, respectively. The low elastic wave velocities and loss in Bi12GeO20, the low crystallization temperature, the piezoelectric coupling and the fact that it is cubic suggest possible advantages for device application involving storage of information at vhf and microwave frequencies.