Optical and physical parameters of Plexiglas 55 and Lexan

Abstract

The following parameters have been obtained for Plexiglas 55 and Lexan: refractive index n at 486.1 nm, 589.3 nm, and 656.3 nm, the thermooptic constant dn/dT at 632.8 nm, the linear thermal expansion coefficient; the photoelastic constants q₁₁, q₁₂, p₁₁, and p₁₂; and the elastic moduli c₁₁, c₁₂, s₁₁, and s₁₂. The experimental value for the density derivative of refractive index ρ(dn/dρ)_T deviates by only a small amount from the value calculated from the Lorentz-Lorenz equation. This is the expected result for molecular solids. The density variation with temperature is the dominant contribution to dn/dT.