Measurement of the wavelength dependence of birefringence for optical disk substrates

The in-plane and vertical birefringence of polycarbonate plastic substrates of optical disks are measured for wavelengths between 360 and 860 nm, which covers the full range of interest for blue as well as for the current red and infrared recording. It is found that the birefringence generally decreases as the measurement wavelength is increased. In a typical case, the in-plane birefringence, Δn‖ goes from 1.7 × 10(-5) to 1.2 × 10(-5), and the vertical birefringence, Δn⊥, drops from 7.5 δ 10(4-) to 5.7 × 10(4-) in the wavelength range from 360 to 860 nm.