RU126483U1 - MULTI-CHANNEL POLARIZATION-INDEPENDENT ADAPTIVE DEVICE FOR RECORDING WEAK DYNAMIC INFLUENCES - Google Patents

Abstract

1. A multi-channel polarization-independent adaptive device for recording weak dynamic effects, containing a source of reference and signal coherent light waves, a beam splitter that divides the coherent wave into two waves, the reference and signal, moreover, the coherent light waves intersect at right angles to each other, and in their place A photorefractive crystal is installed at the intersections to form holograms, a reference coherent light wave is passed through a quarter-wave phase plate to give it an optical polarization, and at least one photodetector, characterized in that the quarter-wave phase plate is installed after the beam splitter, the device contains N photodetectors, the reference coherent wave is directed into the photorefractive crystal along the [100] axis, the signal coherent wave is transmitted through an N-channel splitter that separates the signal coherent wave on N signal waves directed into the photorefractive crystal along the [001] axis by means of multimode fiber optical fibers, after the photorefractive crystal and signal waves are passed through the focusing lens on the N photodetectors, the number of channels equal to the number splitter fotopriemnikov.2. The device according to claim 1, characterized in that a laser is used as a source of a reference coherent light wave and a signal coherent light wave. The device according to claim 1, characterized in that a crystal of cubic symmetry is used as a photorefractive crystal to form a hologram. The device according to claim 1, characterized in that as a beam splitter uses

Description

The utility model relates to the field of optoelectronics and can be used in the construction of adaptive hypersensitive sensors based on dynamic holograms recorded in photorefractive crystals. The device is designed to detect weak physical influences.

A device for anisotropic diffraction of light waves containing a laser, a polarizer, a phase plate, a crystal (Delaye Ph., Blouin A., Drolet D., de Montmorillon LA, Roosen G., Monchalin J.-P. Detection of ultrasonic motion of a scattering surface by photorefractive InP: Fe under an applied dc field // J. Opt. Soc. Am. B. - 1997. - Vol.14. - No.7. - P.1723-1734).

Two linearly polarized waves interact in a crystal under anisotropic diffraction conditions. The phase difference between the transmitted and diffracted waves is introduced due to their transmission through the quarter-wave plate-polarizer system.

The disadvantages of this device are the presence of an additional polarizer, the operation of which leads to additional losses of light power, and the use of only linear polarization as a signal beam of a light beam.

A device based on vector mixing of waves in a cubic crystal in the presence of an alternating electric field is also known (Kamshilin AA, Prokofiev VV Fast adaptive interferometer with a photorefractive GaP crystal // Optics Letters. - 2002. - Vol.27. - No.19. - P.1711-1713).

The known device contains sources of light coherent waves, which are arranged so that the light waves intersect at an angle to each other. At their intersection, a photorefractive crystal of cubic symmetry is installed to form a dynamic hologram. Two waves get into the crystal, one of which is a signal one, and the other a reference one. Waves have different polarization states - linear and elliptical. The waves propagate in the crystal at a small angle to each other, as a result of which a transmission-type holographic grating with a low diffraction efficiency is formed in the crystal. To improve the efficiency of the device using an external alternating electric field obtained from an alternator.

The disadvantages of the known device include:

- large spatial period of the holographic lattice;

- low metrological parameters;

- use as a signal beam of the light beam only linear polarization.

Non-volatile adaptive device for linear phase demodulation is also known RF patent No. 75760 for utility model “Non-volatile adaptive device for linear phase demodulation”, IPC G02F 1/00, 2008. The device contains a fiber-optic sensor and a laser arranged in such a way that light waves emitted by them are directed relative to each other at an angle close to 180 °, a photorefractive crystal located at the intersection of these light waves, a photodetector located on the same horizontal axis as the signal light in lnoy fiber optic sensor for the photorefractive crystal, a polarizer disposed on one horizontal axis between the optical fiber sensor and the photorefractive crystal, and the two phase plates are disposed on the same horizontal axis between the laser and the photorefractive crystal. The intensity of the signal wave is recorded by a photo detector.

The disadvantages of this device include:

- the presence of high optical losses introduced into the signal wave by a polarizer;

- reduced sensitivity;

- the presence of polarizing noise;

- use as a signal beam of the light beam only linear polarization.

Closest to the claimed device is a technical solution according to RF patent No. 92731 for the utility model “Polarization-independent adaptive linear phase demodulation device”, IPC G02F 1/00, priority date 10/26/2009. The device contains a fiber-optic sensor and a laser reference signal waves, arranged so that coherent light waves intersect at an angle to each other, a photorefractive crystal of cubic symmetry is installed at the intersection point to form a hologram and a photodetector. The reference coherent light wave is passed through the phase quarter of the wave plate to give it an elliptical polarization. After the phase quarter of the wave plate of the device, a beam splitter and two mirrors are installed. The beam splitter divides the coherent reference wave into two waves, and the mirrors direct the coherent reference waves into the photorefractive crystal at right angles to each other along the axes of the photorefractive crystal [100] and [001]. The coherent signal wave is directed into the photorefractive crystal at right angles to the coherent reference waves along the axis of the photorefractive crystal [010].

This technical solution for its functional purpose and for its technical nature is the closest to the claimed and taken as a prototype.

The disadvantages of this device include:

- the presence of optical loss;

- reduced sensitivity;

- the presence of polarizing noise.

The objective of this utility model is to create a multi-channel polarization-independent adaptive device for recording weak dynamic effects, which will allow simultaneous measurements of several parameters of the studied object or measurement of the parameters of the studied object at several points, as well as reduce optical loss, eliminate polarization noise and increase the sensitivity of the device, and in addition, it will eliminate cross-channel influence on each other and provide independent th operation of the channels of the device separately.

The problem is solved in that in a multichannel polarization-independent adaptive device for recording weak dynamic effects, containing a source of a reference and signal coherent light waves, a beam splitter that divides the coherent wave into two waves, the reference and signal, the coherent light waves intersecting at right angles to each other, and at their intersection a photorefractive crystal is installed to form holograms. The reference coherent light wave is passed through the quarter-wave phase plate to give it an elliptical polarization, with the quarter-wave phase plate installed after the beam splitter. The device also contains N photodetectors and an N-channel splitter. The reference coherent wave is directed into the photorefractive crystal along the [100] axis. The signal coherent wave is passed through an N-channel splitter that separates the signal coherent wave into N signal waves directed into the photorefractive crystal along the [001] axis by means of multimode fiber optical fibers. After the photorefractive crystal, the signal waves are transmitted through a focusing lens onto N photodetectors. The number of channels of the splitter is equal to the number of photodetectors.

A laser is used as a source of a reference coherent light wave and a signal coherent light wave.

A crystal of cubic symmetry is used as a photorefractive crystal to form a hologram.

A non-polarizing beam splitting cube with a division coefficient close to 50:50 is used as a beam splitter.

A multi-mode fiber optic splitter is used as an N-channel splitter.

In the claimed multi-channel polarization-independent adaptive device for recording weak dynamic effects, common features for him and for his prototype are:

- reference and signal coherent light waves intersect at right angles to each other;

- at the intersection of light coherent waves, a photorefractive crystal of cubic symmetry is installed to form a hologram;

- a reference coherent light wave is passed through a quarter-wave phase plate to give it an elliptical polarization;

- photodetector.

A comparative analysis of the proposed technical solution and prototype shows that the first has, in contrast to the prototype, the following essential features:

- the presence of N signal waves obtained by passing a common signal wave through an N-channel multimode fiber optic splitter, and sent to the photorefractive crystal of cubic symmetry along the [001] axis through multimode fiber optical fibers;

- after a photorefractive crystal of cubic symmetry, the signal waves are transmitted through a focusing lens to the photodetectors;

- the coherent reference wave is directed into the photorefractive crystal of cubic symmetry at right angles to the coherent signal waves along the axis of the photorefractive crystal [100];

- the presence of a laser as a common source of reference and signal waves.

The set of essential features of the claimed utility model has a causal relationship with the achieved technical result.

The essence of the technical solution is illustrated by the drawing, which shows a diagram of a multi-channel polarization-independent adaptive device for recording weak dynamic effects, where are indicated:

1 - laser

2 - beam splitter

3 - phase quarter-wave plate

4 - common signal wave

5 - N-channel fiber splitter

6 - sensitive elements

7 - N signal waves

8 - photorefractive crystal

9 - reference wave

10 - focusing lens

11 - N photodetectors.

In the drawing, the axes [001], [010], [100] of a photorefractive crystal of cubic symmetry are additionally indicated.

A multichannel polarization-independent device for recording weak dynamic effects is part of any interferometer and is designed to mix (combine) the reference and N signal light waves. The device contains a fiber-optic laser for generating reference and signal waves, while the coherent light waves 7 and 9 intersect at right angles to each other, at their intersection a photorefractive crystal of 8 cubic symmetry is installed to form a hologram and N photodetectors 11. Reference coherent light wave 9 is passed through a phase quarter-wave plate 3 to give it an elliptical polarization. The total signal coherent wave 4 is passed through an N-channel splitter 5, which divides the signal wave into N waves directed to the photorefractive crystal 8 along the [001] axis, and the coherent reference wave 9 is directed to the photorefractive crystal 8 at right angles to N coherent signal waves 7 along the axis of the photorefractive crystal [100]. After the photorefractive crystal, 8 N signal waves 7 are transmitted through a focusing lens 10 to the photodetectors 11.

Multichannel polarization-independent device operates as follows. The device is an adaptive interferometer, in which multimode optical fibers 6, which are a sensor network, are used as sensitive elements. The number of channels of the device is 2-1000. Two waves are fed from laser 1 — reference 9 and the general signal 4. Reference 9, passing through the quarter-wave plate 3, enters the photorefractive crystal 8 along the main crystallographic axis [100] by means of multimode optical fibers 6. Signal wave 4 enters the N-channel fiber splitter 5, where it is divided into N signal waves 7. Next, N signal waves 7 through multimode fiber optical fibers 6, which act as sensitive elements, fall into the photorefractive crystal 8 along the main crystallographic axis [001] perpendicular to the reference wave 9. The interference of each of the N signal waves 7 with the reference wave 9 due to the photorefractive effect leads to the formation of phase holographic phase gratings in the crystal, the wave vectors of which are directed at angles of 45 degrees to the main axes of the photorefractive crystal 8. The interaction of N signal waves 7 with the reference wave 9 in the photorefractive crystal 8 leads to the conversion of phase modulation to modulation of the radiation intensity. The conversion of phase changes to intensity changes (phase demodulation) is linear. In this case, there is no interaction between the signal waves, because in such a geometry, when the reference and signal waves intersect at a right angle in the photorefractive crystal, due to the anisotropy of the electro-optical effect, the interaction of the signal waves among themselves is forbidden if they propagate strictly in the [001 direction ], which eliminates the possibility of crosstalk between the channels. The detection of physical effects by the device is as follows. Sensitive elements of the device are located in the studied area, the impact of which on them leads to modulation of the phase of the signal waves passing inside. At the output of the device, photodetectors register the radiation intensity in each channel, while the number of photodetectors is equal to the number of channels in the device.

Claims (5)

1. A multi-channel polarization-independent adaptive device for recording weak dynamic effects, containing a source of reference and signal coherent light waves, a beam splitter that divides the coherent wave into two waves, the reference and signal, moreover, the coherent light waves intersect at right angles to each other, and in their place A photorefractive crystal is installed at the intersections to form holograms, a reference coherent light wave is passed through a quarter-wave phase plate to give it an optical polarization, and at least one photodetector, characterized in that the quarter-wave phase plate is installed after the beam splitter, the device contains N photodetectors, the reference coherent wave is directed into the photorefractive crystal along the [100] axis, the signal coherent wave is transmitted through an N-channel splitter that separates the signal coherent wave on N signal waves directed into the photorefractive crystal along the [001] axis by means of multimode fiber optical fibers, after the photorefractive crystal and signal waves are passed through the focusing lens on the N photodetectors, the amount of branching channels equal to the number of photodetectors. 2. The device according to claim 1, characterized in that a laser is used as a source of a reference coherent light wave and a signal coherent light wave. 3. The device according to claim 1, characterized in that a cubic symmetry crystal is used as a photorefractive crystal to form a hologram. 4. The device according to claim 1, characterized in that a non-polarizing beam splitting cube with a division ratio close to 50:50 is used as a beam splitter. 5. The device according to claim 1, characterized in that a multimode fiber optic splitter is used as the N-channel splitter.

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