OPTICAL, THERMOOPTICAL, ELECTROOPTIC, AND PHOTOELASTIC PROPERTIES OF BISMUTH-GERMANATE (BI4GE3O12)

To assess the suitability of bismuth germanate as an electro-optic mat erial for high precision applications, we have confirmed and extended previous data on its refractive index, electro-optic tensor element r( 41), and thermal expansion coefficient. In addition, we have measured the thermo-optic coefficient dn/dT, the temperature dependence of the electro-optic coefficient, and the stress-optic tensor elements. From the stress-optic tensor elements and previously published data, we hav e computed the strain-optic tensor elements. The index of refraction i s given, to a good approximation, by the single-term Sellmeier equatio n, n(2) - 1 = s(0) lambda(02)/[1 - (lambda(0)/lambda)(2)], with s(0) = 95.608 mu m(-2) and lambda(0) = 0.1807 mu m. The thermo-optic coeffic ient is 3.9 x 10(-5)/degrees C at 632.8 nm and 3.5 x 10(-5)/degrees C at 1152.3 nm. The electro-optic tensor element varies between approxim ately 1.05 and 1.11 pm/V over the spectral range of 550-1000 nm; its n ormalized effective change with temperature is approximately 1.54 x 10 (-4)/degrees C. The thermal expansion coefficient is 6.3 x 10(-6)/degr ees C over the range 15-125 degrees C. Values of the stress-optic tens or elements are q(11) - q(12) = -2.995 x 10(-13) m(2)/N and q(44) = -0 .1365 x 10(-12) m(2)/N. The strain-optic tensor elements are p(11) - p (12) = -0.0266 and p(44) = -0.0595. (C) 1996 Optical Society of Americ a.