SU1278689A1 - Device for measuring optical parameters of crystals - Google Patents

Abstract

This invention relates to a measurement technique and is intended to investigate anisotronic media. , The purpose of the invention is to measure the parameters of absorbing gyrotropic crystals. The goal is achieved by the fact that the light beam from source 1 passes through a polarizer 2, an electro-optical modulator of ellipticity 3 at a frequency uJ, and is directed to a Mach-Zander interferometer, formed by beamshadow dividers 4 and 5. Four half-wavelength phase signals are introduced into the interferometer plates 6,7,8 and 9, and plates 7 and 8 rotate with frequency C, isotropic electro-optical compensator 12, isotropic electro-optical modulator 13 at frequency o) c) n mechanical interrupter 14 at frequency i At the interferometer output there is wives photodetector 15, which are connected to the input narrow-band amplifiers 16 and 17, tuned to the frequency of respectively. A half-wave plate 9 is installed (L novlen with the possibility of removal from the interferometer. If there are none, 10 or reference 11 crystals are fed to the studied orthogonal half-emitting rays, and if present, equally polarized. 1 Fig. TS9 sj 00 o 00

Description

This invention relates to a measurement technique and is intended to investigate anisotronic media.

The aim of the invention is to measure the parameters of absorbing gyrotropic crystals.

The drawing shows the proposed device.

The device contains a source of radiation 1, a polarizer 2, an electro-optical modulator 3, an elliptical type, two beamsplitters 4 and 5, forming a two-beam Mach-Zehnder type interferometer, four half-wave phase plates 6–9, a crystal under study 10, a reference crystal 11, an electro-optical isotropic compensator 12 and an electro-optical isotropic phase modulator 13, a mechanical beam interrupter 14, a photo-detector 15, narrow-band amplifiers 16 and 17, a recording device 18, a mechanism 19 for rotating half-wave plates 7 and 8, and a mechanism 20 d permescheni parallel plate 9.

The device works as follows.

The beam of light, which passed through the polarizer 2, modulator 3 and half-wave plate 6, has a modulated ellipticity and the azimuth of the major axis of the ellipse j is equal to zero. The beam of light 2 after passing through the rotating half-wave plate 8 passes through all possible polarization states, but always remains orthogonal to the beam cx, passing through the rotating half-wave plate 7, while the interference signal is zero. The frequency of E3 modulation of ellipticity (3 by several orders of magnitude higher than the frequency uij of the modulation of the azimuth of the beam d, the ray of light a, passed through the study-.

My crystal 10 changes its state of polarization, unless the state of polarization of this beam corresponds to the eigenvector of the crystal 10. In the absence of a half-wave plate 9, both beams c. and aj in this case are orthogonal, as evidenced by the absence variable component output device, as the module -. torus 13, consisting of two identical crystals, the optical axes of which are rotated with respect to

the other at 90 ° is isotropic, and its modulation frequency is uJ2

2

The measurement includes the following

operations,

1, Using a narrow-band amplifier 16 tuned to the modulation frequency oOj, which plays the role of a null indicator, fixes the parameters Ыр and Рр of the beam a, at that moment, when the latter has a state of polarization at which it passes through the crystal under study without changes . The azimuth dp and the ellipticity of Pp correspond to the eigenvector P, and the output signal is zero (there is no interference term). Through the feedback circuit, the ellipticity modulation on the crystal 3 is switched off, the rotation of the half-wave plates 7 and 8 is stopped, and thereby the parameters Np and P of the beam a,,, are fixed

2, When eigenvector parameters are known, determine the coil

. For

absorption factor X

This includes the rotation of the chopper 14, which, with a frequency f, alternately interrupts both beams of the interferometer. The Xp value is determined by the amplitude of the output signal of the narrowband amplifier 17, tuned to the frequency tJ,

 3, Phase displacement of the beam cx, i with the polarization state P is determined using half-wave plate 9, isotropic modulator 13, isotropic compensator 12 (arranged similarly to modulator I3) and amplifier 16 (with beam interrupter 14 missing), Half-wave plate 9 provides the same polarization states of the beams that feed the studied and reference crystals. Using an isotropic compensator 12, the phase shift of the beam of the beam, necessary for the phase difference between the beams to become, is determined.

0. tg

equal to the value of NpTf + g (, 1, 2,. ,,),

In this case, the output signal of the amplifier 16 is zero,

Claims (1)

4, Re-enables modulation on 5 modulator 3 and rotation of half-wave plates 7 and 8 (in the absence of plate 9 and chopper 14) and, similarly to n, 1, find the second proper vector & , 5, Similarly to n, 2 and 3, the absorption coefficient X ---- 3 and the phase shift of the beam a, with the polarization state Q, are determined. 6. By the difference Xp-Xd X, dichroism is determined, the birefringence of the crystal is found from gr + (Ng-Np) T. To determine N NQ-NP, it is necessary to measure T at two different crystal thicknesses. An apparatus for measuring optical parameters of crystals containing a radiation source and a polarizer sequentially located along the optical axis of the device; an ellipticity modulator with a frequency of 3; two beamsplitters forming a two-beam interferometer of the Mach-Zander type and a photoreceiver, two narrow-band amplifiers and a recording receiver device, as well as an electro-optical phase modulator, an interrupter and a reference crystal, the photodetector being connected to the recording device in parallel with single narrow-band amplifiers, distinguished by the fact that, in order to measure the parameters of absorbing gyrotropic crystals, it additionally contains four half-wavelength phase plates, the first half-wave plate located on the path of the first beam of the interferometer after the first beamsplitter and has an azimuth of the optical axis parallel to the azimuth the polarizer, the second half-wave plate is located on the path of the first beam of the interferometer between the first half-wave plate and the crystal under study and is installed with the possible uniformity of rotation with a frequency uJj-iiuJ around its axis coinciding with the first beam, a third half-wave plate is located on the path of the second beam of the interferometer after the first beam splitter and installed with the possibility of uniform rotation with a frequency around the axis coinciding with the second beam, and the azimuth of its optical axis the constant is rotated by 45 ° relative to the azimuth of the optical axis of the second half-wave plate; the fourth half-wave plate is located on the path of the second beam of the interferometer between the third half-wave plate The reference and reference crystal are perpendicular to the second beam of the interferometer, and the azimuth of its optical axis is 45 angle with the azimuth of the first half-wave plate, the phase compensator is electro-optical, consists of two identical crystals, the optical edges of which are mutually perpendicular, and installed on the path of the first beam of the interferometer behind the crystal under study, the electro-optical phase modulator is made identical to the electro-optical phase compensator and installed on the path of the second beam of the interferometer after this coupon crystal | and the interrupter is located on the path of both rays of the interferometer in front of the second beam splitter.