Evaluation of the Free Spectral Range of an Etalon by Referring an Optical Frequency Comb

抄録

We develop an alignment monitoring system which adopts a three-dimensional length measurement grid based on multiple absolute distance interferometers. Each interferometer refers an interval of an optical pulse train of an optical frequency comb filtered out by an etalon. The interval is determined by a free spectral range, FRS of the etalon, which should be evaluated accurately with an uncertainty better than several ppm. Here, we evaluate the FSR from a distance between interference signal peaks generated by the etalon and the optical frequency comb by referring a repetition frequency of the optical frequency comb. Then, we compensate the evaluation based on a relation between the observed peak distance change against the repetition frequency change of the optical frequency comb.