Evaluation of grating periods by using pulsed laser source

In this paper, a measurement method with a mode-locked laser source for evaluation of grating periods, which is based on the laser diffraction method with the Littrow configuration, is proposed. Optical frequencies of the mode-locked laser, which are referred to as the optical frequency comb, have deterministic mode frequencies with equal intervals in the frequency domain. Since the frequency of each comb mode can be highly stabilized by a high precision external standard, measurement accuracy of the laser diffraction method is expected to be improved. In this study, a prototype optical setup based on the proposed method is developed, and some experiments are carried out to verify the feasibility of the proposed method.