Method to measure frequency change of tunable laser based on Jamin shearing interferometer

摘要

A method to measure the frequency change of the tunable laser based on a Jamin shearing interferometer is proposed. The Jamin shearing interferometer is composed of two Jamin plates, two shearing plates and a retardation plate. The tunable laser beam is split into two beams by one Jamin plate. The retardation plate is placed in one of two beams to provide additional phase retardation. Two beams pass two shearing plates, respectively, and are combined by the other Jamin plate to form lateral shearing interferogram. In course of tuning, interference fringes are shifted as a whole and its spacing is kept constant. By detecting displacement of fringes, the frequency change of the laser is obtained. In experiments, we observed that interference fringes were shift periodically when the laser diode was modulated sinusoidally. A series of interferogram in which fringes are shifted as a whole with the variation of the frequency are obtained. The feasibility of the method is verified.