Simultaneous measurement of refractive index and thickness by low coherence interferometry considering chromatic dispersion of index

Low coherence interferometry can provide simultaneous measurement of refrac tive index n and thickness t of a transparent plate, as reported recently b y some research groups. Precise measurement of n and t is impossible unless chromatic dispersion of index is taken into account. We then proposed and demonstrated a unique technique for simultaneous measurement of phase index n(p), group index n(g) and thickness t using a special sample holder. This paper describes a novel technique for simultaneous measurement of n(p), n( g) and t using an approximate expression of the chromatic dispersion in ter ms of n,. The approximate expression of chromatic dispersion does not requi re use of the special sample holder, and n(p), n(g) and t are determined fr om two measurable quantities with an accuracy of 0.3% or less, for the samp le thickness was around 1 mm. In addition, it is possible to shorten the me asurement time compared with the above method.