Tomsk State University. Physical Department.
Laboratory of training physics experiment
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Fabry - Perot  Interferometer   Обратно  Далее  
Since the spectral instruments of high resolving power have been of great value in optics and atomic physics, they are of enormous interest in the physics course. The cost of scientific instruments is very high, that is why usually there are no in physics laboratories. Earlier there was an opinion that high resolution devices operation can be demonstrated only in close circle.

In our laboratory since 1962 we have been designing several Fabry-Perot etalons. We have simplified the construction so that the demonstration did not require a long-term high resolving stability of the tuned device. That is why the device barrel had been turned from an ordinary offcut of thick-walled tube. The plates can be simply coated with aluminium or multiple dielectric coating in 546.1 nm. The optimum distance between the mirrors was specified with a ring with three fixed balls 3.2 mm in diameter. The balls taken from bearings were selected and slightly grinded.

It should be pointed that in our laboratory the devices are made with non-standard distance between mirrors. The Fabry-Perot etalon has a rising resolving power, as the distance between mirrors is getting wider. Meanwhile the space between rings reduces and the size of the whole pattern is getting smaller. That is why demonstrating a large high-aperture pattern of lines of an equal inclination in a lecture room, we apply the etalon with small space between mirrors, it is about 0.1 mm. The maximal resolution of this device is used in the other extreme variant: the etalon with distance between mirrors of 30 cm is applied for Doppler effect measurement in an optical range. The device with a medial value, about several millimeters, is useful for observation of hyperfine structure of spectral lines and Zeeman effect.

The picture shows the lines of an equal inclination pattern. The rings which have been created by a mercury green line and an orange doublet of 2 nm in distance are obvious. The light source is a mercury lamp. And in the third, the etalon with the small space between mirrors about 0,1 mm is applied to demonstration the rings of an equal inclination in a lecture auditorium. The picture of lines of an equal inclination is shown. The rings formed by a green line and an orange doublet of mercury with distance in 2 nm are visible.
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