REFRACTIVE-INDEX MEASUREMENT AT HIGH-SPATIAL-RESOLUTION BY SOURCE DOUBLING

We report a new interferometric technique for measuring the refractive index of a thin solid sample at submillimetric resolution. Source doubling is obtained with a modified triangular common path arrangement used to generate a spatially distributed interferogram detected by a CCD line sensor. When inserted into the optical path, the sample alters the distance between the two secondary point sources, thereby changing the fringe spacing. We determined the refractive index at 632.8 nm by measuring the change. The spatial resolution of the measurement is limited by the size of the primary source and the magnification of the probe spot-forming lens. The technique is employed to determine the refractive index of a microscope slide with 150-mum probe spots.