Refractive index of Bi-substituted gadolinium iron garnet films grown by liquid-phase epitaxy

Abstract

Refractive indices of (GdBi)3Fe5O12 and (GdBi)3(FeAlGa)5O12 films on Nd3Ga5O12 substrates were measured at 0.633 μm by a waveguide technique. The dispersion of refractive index was determined from the interference spectra over the wavelength region of 0.5–2.0 μm. Wavelength dispersion was analyzed by the Sellmeier oscillator formulation: n2=1+E01 Ed1/(E201−E2) +E02 Ed2/(E202−E2). Increase in refractive index with increase in Bi3+ concentration is attributed to a decrease in oscillator energy E01 and an increase in dispersion energy Ed1 associated with oxygen–2p–iron-3d charge transfer transitions enhanced by hybridization of bismuth-6s2 and oxygen-2p electrons.