Techniques to Measure the Refractive Index of GDP and Ge-Doped GDP with Monochromatic Light

Equation-of-state experiments using VISAR require the refractive index of undoped glow discharge polymer (GDP) and Ge-doped GDP at 532-nm-wavelength light. The index was measured with two different techniques. The first technique used measurements of pulsed laser reflections off a GDP foil suspended in refractive index fluid standards. Fluids with different indices were replaced until minimum reflection was achieved; this occurred at the matching index of the fluid and GDP film. The index of the correct matching fluid (or fluid mixture) was measured with an Abbé refractometer to produce n_D (the refractive index at sodium D line, 589 nm) and was corrected for wavelength using manufacturer-supplied Cauchy equation coefficients. The second technique used interferometry to measure fringe shift over GDP and Ge-GDP bumps when submerged in various refractive index fluid standards. The fringe shift was minimized when matching the indices of the fluid and film. The refractive indices at 532 nm were 1.563 and 1.570 for undoped GDP and Ge-doped GDP, respectively.