Optical Constants of Crystalline Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ by Brillouin Light Scattering Spectroscopy

TL;DR

This study measures the optical constants of crystalline Bi$_2$Sr$_2$CaCu$_2$O$_{8+eta}$ using Brillouin light scattering, providing data that align with some optical methods but show higher absorption values.

Contribution

It introduces a novel application of Brillouin light scattering to determine optical constants of this superconductor material.

Findings

Optical extinction coefficient-to-refractive index ratios range from 0.19 to 0.29 near the c-axis.

Optical constants agree with reflectance data but are 5-7 times larger than interference measurements.

The study provides detailed optical property data at 532 nm wavelength.

Abstract

Room-temperature optical constants of crystalline Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ 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 $0.19 \leq 2\kappa/n \leq 0.29$ 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.