Wavelength measurement of a Helium-Neon laser using a Michelson-type amplitude division interferometer

This paper describes a way to experimentally calculate the wavelength of the light emitted by a Helium-Neon laser, model HNLS008R, which according to its technical manual has 0.8 mW of power and wavelength 632.8 nm. The experiment is based on Michelson's light interference theory, which consists of using a light source that illuminates a beam splitter, which allows dividing the light wave into two paths, one is directed towards a fixed mirror and the other towards a mobile mirror, these optical elements allow reflecting the light with the same angle of incidence producing a superposition of waves in the form of circular finges. When the movable mirror moves about its optical axis, a movement in the fringes of the order of half a wavelength is observed. The equations governing the behavior of the interference fringes in the experiment are also described and the expression to calculate experimentally the wavelength as a function of the number of fringes, the displacement of the moving mirror and the wavelength of the source under test is obtained. Finally, the experimental results are compared with the technical data provided by the manual of the device, concluding that the laser still conserves a stability in the wavelength, so it is still reliable to be used in optical experimental arrangements.