<title>Refractive index changes in solid-state laser materials</title>

Abstract

In this work the application of Thermal Lens (TL) and Z-scan techniques to the study of thermo-optical and spectroscopic properties of Solid-State Laser Materials (SSLM) is described. The theorectical basis for quantitative measurements is discussed together with the advantages and limitations of the methods. We discuss applications of the TL technique to the study of thermal diffusivity, the temperature coefficient of optical path length (<i>ds/dT</i>), heat efficiency (the fraction of absorbed energy converted into heat) and the florescence quantum efficiency (<i>&#951;</i>). Several approaches to determine <i>&#951;</i> and the study Energy Transfer mechanisms in SSL materials doped with Nd³⁺, Y³⁺, Tm³⁺ and Er³⁺ are presented. The electronic contribution to the nonlinearity was investigated using the Z-scan technique in the time-resolved mode. The measurements were performed spectroscopically allowing the determination of the lineshapes of real and imaginary parts of the nonlinear refractive index (<i>n</i>₂) in resonance with laser transitions. The results are interpreted considering resonant and nonresonant contribution to <i>n</i>₂. We also compare the magnitude of electronic and thermal refractive index changes in SSL.