SU780773A1 - Active interferometer - Google Patents

Description

(54) ACTIVE INTERFEROMETER

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The invention relates to laser technology and makes it possible to measure small changes in the optical density of a medium or small linear displacements.

A known passive interferometer containing an optical resonator formed by two mirrors, inside of which the medium under study is placed,. and an external source of optical radiation. However, such an interferometer, due to the nonlinearity of its apparatus function, does not allow measurements that are simultaneously accurate and wide-range.

An active interferometer is known that is closest in technical essence to the proposed i containing an optical resonator formed by two mirrors, inside which a phase element is arranged in series, a gas discharge laser tube with end windows and the medium 2 under investigation. Phase element coI 2

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It is made of two separate plates, close to a quarter-wave. The hardware function of this interferometer is linear, so an increase in the measurement range does not reduce their accuracy. However, the adjustment of the range is carried out mechanically;: the action on the phase element (by turning the quarter-wave plates relative to each other), which is not necessary

10 a fairly accurate adjustment of the instrument over the range of measurements, stability and reproducibility of the instrument settings. In addition, the need for turning the plates requires the presence of a special turning mechanism inside the laser resonator. -

The purpose of the invention is to increase the control accuracy and simplify the design,

Claims (2)

This is achieved by the fact that the gas discharge of the laser tube is placed in a solenoid coaxially with it, and the phase element is designed as a phase gap with a fixed phase anisotropy and is located on the site of one of the windows of the gas discharge laser tube. : -, - The drawing shows the active interferometer. In the proposed interferometer between the mirrors 1 forming the optical resonator, the phase 2 is placed, the laser discharge tube 3 with windows 4 located at an angle of 3-5 to the tube axis is located inside the solenoid 5 coaxially with it and the volume with the test medium 6, The active interferometer is as follows. An optical quantum generator consisting of a laser tube 3 and a phase-exciter resonator formed by mirrors 1 and phase element 2 operates in a stable generation mode with two orthogonally polarized longitudinal modes with frequencies (11 / W. The inter-mode splitting tC - 2. is fixed because it is determined by the unchanged phase anisotropy introduced into the resonator by element 2, the change in the optical density iSn of the medium under study in volume 6 or the displacement of one of the mirrors 1 along the axis of the resonator by The optic density leads to a change in the optical length of the resonator and, as a result, to the frequency shift of the ruyom1x modes by an amount the same for both iodine and the projec- tional frequency of it, respectively. Iyten the shape of each generation mode changes (and therefore, Lm), linearly, f. their total intensity remains unchanged. The contribution of one of them to the transient radiation is emitted by the polarizer 7 and recorded by the photoreceiver 8. The change in intensity is fTi by OH or O b. -l l The measurement range of the OI or O is determined by the offset of the frequency d, icotopOMy corresponds to a FULL linear adjustment of the intensity of the detected mode from zero to the maximum value. It is known that the value of b depends both on the intermode distribution 1, 12,, 1 and on the splitting properties of the active medium. In the axial magnetic field, the line amplification is laser. Due to the Zeeman effect, the transition is split into two O-components. When the intensity changes, the magnetic field H varies the position of the maxima of the zeuman doublet of relativity (JU. At the same time, D smoothly changes from the limits x to x at and dk, ax ° is determined only by the phase anisotropy introduced by the element 2. . „;, it is possible to ensure how many miVi. The bottom is small, up to zero HO at a fixed intermode splitting is determined by the magnetic properties of the laser transition. The interferometer allows to measure plasma densities in the range of 10 to 10-6 cm while significantly The design of the device is simplified and its remote control is provided. Claim 1. Active interferometer, containing an optical resonator formed by two mirrors, inside which there is a phase element sequentially, a gas discharge laser tube With end windows and the medium being studied differing from With the purpose of monitoring accuracy and simplify the design, the gas discharge of the laser tube is placed in a solenoid coaxially with it, and the phase element is designed as a phase plate with fixed phase anisotropy 2. The interferometer according to claim 1, is different from the fact that the phase ele- ment is located on the site of one of the windows of the gas discharge laser tube. Sources of information that are taken by the WHO during examination 1.Pnitsky L.N. Laser plasma diagnostics. Atomizdat, M., 1978, p. 143. 2. Kozin G. I. and others. ZHTF, 1973, t.43, U-. 1-781 prototype.