Optical constants of crystalline Bi₂Sr₂CaCu₂O 8+δ by Brillouin light scattering spectroscopy

Abstract

Room-temperature optical constants of crystalline Bi2Sr2CaCu2O 8 + δ were determined using data extracted from Brillouin light scattering spectra. Optical extinction coefficient-to-refractive index ratios at a wavelength of 532 nm were obtained from bulk phonon peak linewidth and frequency shift measurements and range from 0.19 ⩽ 2 κ / n ⩽ 0.29 for directions close to the crystallographic c-axis. These ratios, and optical extinction coefficients, absorption coefficients, and imaginary parts of the dielectric function determined from these ratios and known refractive index, are in general agreement with values found in optical reflectance studies, but are 5–7 times larger than those extracted from optical interference measurements.

Influence of incommensurate structure on the elastic constants of crystalline Bi2Sr2CaCu2O8+δ by Brillouin light scattering spectroscopy

“…Brillouin spectra were collected for light incident at angles ranging from 10° θ i 75°(corresponding to ∼5°-28°from the crystallographic c-axis) to the sample normal by rotating the sample about an axis normal to the plane of incidence as shown in [13]. Bulk acoustic phonon velocities, V B , were determined directly from spectral peak frequency shifts using the well-known Brillouin equation f B = 2nV B /λ, where f B is the bulk phonon frequency shift and n = 2.0 is the refractive index of Bi-2212 [14][15][16].…”