We describe here a grating interferometer with extremely high stability and which can be used as a differential refractometer. The instrument uses heterodyne techniques to achieve high sensitivity. We present an analysis of the operation of the system and results which show that it has a long term stability of the order of 1/1500 wavelength over 2 h.
© 1991 Optical Society of America
Thomas H. Barnes, Kenji Matsumoto, Tomoaki Eiju, Kyofumi Matsuda, and Noatake Ooyama, "Grating interferometer with extremely high stability, suitable for measuring small refractive index changes," Appl. Opt. 30, 745-751 (1991)