Wavelength shift determination using a dual-path heterodyne Mach–Zehnder interferometer

This paper introduces a dual-path heterodyne Mach–Zehnder interferometer adopted for wavelength shift determinations. In this interferometer, two parallel incident beams are separated into two interference pairs which are then recombined to generate two interference signals. A parallel plate is placed on the path of one wave of an interference pair, so the phase difference of the interference signals is a function of the plate and beam wavelength, and the interferometer is thus able to determine the wavelength shift of the incident beam. A setup constructed to realize the proposed interferometer is described, it shows that the interferometer has a resolution up to 1.1 × 10−10 (λ2/nm), and the experimental results of applying this setup not only agree the validity of the interferometer but also indicate that the interferometer has a stability of 6.5 × 10−10 (λ2/nm).