RU2699055C1 - System for simultaneous control of several laser beams by means of a fixed liquid crystal matrix - Google Patents

Abstract

FIELD: communication equipment.

SUBSTANCE: invention relates to electrical communication, particularly, to control of laser light beams, and can be used in systems of quantum cryptography through free space and for communication between several aircrafts (AC) and / or aircraft and ground stations. In system for simultaneous control of several laser beams by means of fixed liquid crystal matrix containing liquid crystal matrix SLM, lasers, photodiodes, angle reflectors, fiber-optic cables, fasteners, and also comprises two transceiving units, optically interconnected, each of the above units comprises an inclined turning mechanical platform made with possibility of mutual orientation of the above units to each other, at that, on each of said inclined-turning platforms there arranged are said liquid crystal matrix (SLM) with photodiodes fixed on it, corner reflector, transceiving device connected by means of fiber-optic cables with at least two collimators, as well as a computer; liquid crystal matrix (SLM) surface is divided into at least two regions allocated for receiving and transmitting channels, wherein liquid crystal array SLM is configured to simultaneously focus and / or change direction in real time of at least two laser beams generated by laser of receiving / transmitting device, and independent simultaneous monitoring of said areas of SLM surfaces by changing voltage supplied thereto, controlled by control unit.

EFFECT: technical result consists in creating a system which enables simultaneous control of several laser beams using SLM without loss of time for switching between channels and correction of aberrations simultaneously in all channels with achieving a technical result, which consists in reducing the time of transmitting information.

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Description

FIELD OF THE INVENTION

The invention relates to techniques for electrical communication, in particular to the field of control of laser light beams, and can be used in quantum cryptography systems through free space and for communication between several between several aircraft (LA) and / or LA and ground stations.

This technical solution relates to the field of control of laser and light beams by deflecting and focusing using a spatial light modulator (SLM). SLM is a two-dimensional array of pixels consisting of liquid crystals and electrodes underneath. An array of pixels can be located both on a reflective surface and on a transparent one. A phase profile (pattern) is formed on the SLM, during diffraction by which the light is deflected by a certain angle and / or focused. By changing the voltage at the electrodes, you can change the phase (optical path) of the wave reflected from the SLM in the region of the pixel array. Thus, SLM is a phase modulator, in which the phase profile (pattern) can be changed programmatically in real time. SLM is stationary in space, does not require a mechanical orientation system, therefore SLM-based beam control systems are compact, reliable, lightweight and convenient for installation, for example, on unmanned aerial vehicles.

BACKGROUND

Currently, a number of patents are known: [1, 2, 3, 4], as well as review articles [5, 6] on SLMs and laser and light beam control devices using SLMs. In the prototype of this application [1], a pattern is formed on SLM, during diffraction by which the light is deflected by a certain angle or focused. In various configurations, the prototype can change the beam direction (field of view), change the viewing angle, focus, and it is possible to change the focus direction between several objects or directions with high frequency, realizing tracking them in real time (multiplexing). Guidance and retention of beams is carried out by the general methods described in patents [3, 4].

The disadvantage of the prototype [1] is that for monitoring laser beams in optical communication problems, the communication time is divided between channels, reducing the effective transmission rate more than n times, where n is the number of channels. Loss of communication speed occurs due to the finite switching time between channels.

The main goal of the SLM beam control device proposed in this application is to eliminate this drawback and simultaneously control multiple beams using SLM without loss of time for switching between channels.

In the device [2], the SLM performs the function of correcting aberrations. The disadvantage of the device [2] is the correction of aberrations in only one channel, while in our device, the correction of aberrations can be carried out simultaneously in all channels.

SUMMARY OF THE INVENTION

The technical problem of the claimed invention is to create a system that allows simultaneous control of multiple laser beams using SLM without loss of time switching between channels and correcting aberrations simultaneously in all channels with the achievement of a technical result, which consists in reducing the time of information transfer.

The specified technical result is achieved in a system for simultaneously controlling at least two laser beams using a fixed liquid crystal matrix containing an SLM liquid crystal matrix, lasers, photodiodes, corner reflectors, fiber optic cables, two transceiver assemblies, optically interconnected, each of the said nodes contains an inclined-rotary mechanical platform, configured to mutually orient the said nodes together, while on each of the mentioned utyh pan-tilt platforms has said matrix liquid crystal SLM, with photodiodes fixed thereto, a corner reflector, a transceiver connected by optical fiber cables to at least two collimators, the control unit; the surface of the SLM liquid crystal matrix is divided into at least two areas allocated to the receiving and transmitting channels, while the SLM liquid crystal matrix is configured to simultaneously focus and / or change the direction in real time of at least two laser beams generated by the receiving laser - transmitting device and independent simultaneous control of these areas of the SLM surfaces by changing the voltage supplied to them, controlled by the control unit .

An additional feature is that the laser beams focus at an angle of 0.3 radians relative to the angle of incidence.

An additional feature is that the focal lengths corresponding to the patterns of different rays differ by 2 times.

An additional feature is that the area of orientation change of the mechanical platform is 2π steradian.

An additional feature is that guidance on the coordinates of the transceiver nodes is carried out from satellite navigation systems GPS / GLONASS.

An additional feature is that the transmitting and receiving devices are designed to operate in quantum mode, where the level of the transmitting signal is reduced to the level of single photons, and single photon detectors are used in the receiving part of the devices.

In the proposed device, channel separation (multiplexing) is achieved by dividing the SLM surface into several different parts, as shown in Fig. 1, while each part is capable of performing all the functions of the prototype [1] independently of other parts in real time simultaneously for all channels, without the need to switch between channels.

SLM can also carry out the function of correcting aberrations simultaneously for each channel, in the same way as it was done for only one of the channels in the US patent [2]

The device can be used to control beams in optical wireless communication systems. In particular, but not limited to, using the SLM, it is possible to organize the multiplexing of transmission and reception channels as indicated in FIG. 2.

An optical communication system consists of two identical transceiver nodes, called Device 1 and Device 2, located at two communication subscribers. Each Device has a receiver and a transmitter having fiber input / output, equipped with at least two collimators. The radiation from the transmitter from the collimator is directed to one of the SLM regions, and the radiation to the receiver is directed to the detector collimator from another SLM region. As an example, in the implemented system there are two transceivers, one for each of the subscribers. The transmitter of one of the subscribers is optically paired with the receiver of the other subscriber.

BRIEF DESCRIPTION OF THE DRAWINGS

The essence of the proposed technical solution, which consists in the description of features, technical elements and its advantages, is illustrated by examples of specific, but not limiting the claimed technical solutions, embodiments with reference to the accompanying drawings, which are not necessarily drawn to scale, and on which:

FIG. 1 shows the division of a SLM surface into regions corresponding to different channels. Phase profiles (patterns) corresponding to these areas are set independently, which makes it possible to control simultaneously several light beams incident each on the corresponding group of SLM cells.

FIG. 2 shows a general scheme for the integration of modules and units of Devices 1 and 2 between which optical communication is carried out with simultaneous control of two beams (receiving and transmitting) using SLM.

FIG. 3 shows an example of an SLM pattern. Two independent SLM regions are visible, each of which corresponds to its own beam. In the implemented system, the beams are focused at an angle of 0.3 radians relative to the angle of incidence. Focal lengths corresponding to patterns of different beams differ by 2 times.

FIG. 4 is a schematic diagram of a liquid crystal matrix SLM.

SUMMARY OF THE INVENTION

The invention can be implemented in an optical communication system, a general diagram of which is shown in FIG. 2. The system consists of two identical transceiver nodes (Device 1 and Device 2), between which optical communication is made through free space with simultaneous control of two beams (Channel A and Channel B) using SLM. Each device consists of a movable pan-tilt mechanical platform, SLM, a transceiver (PPU) having a fiber input and output and equipped with at least two collimators, as well as a control unit.

A movable tilt-and-turn mechanical platform guides the receiving-transmitting node of the paired subscriber. The area of orientation change of the mechanical platform is 2π steradian. Guidance is carried out according to the coordinates of the nodes, which are obtained from satellite navigation systems GPS / GLONASS. Photodiodes are mounted on the SLM for feedback of the guidance system. The angle of incidence of radiation on the SLM is 10 degrees. For feedback of the guidance system, Centronic OSD15-5T photodiodes were used with a maximum spectral sensitivity in the region of 800–900 nm, which corresponds to laser wavelengths. The radiation transmitted from the Devices 1, falls on the corner reflector of the Device 2 and is recorded by photodiodes.

Liquid crystals of the SLM matrix are placed between two electrodes, one of which is solid and the other is divided into cells (Fig. 4). The mirror is used to reflect the incident signal. A coverslip is necessary for protection. Each cell has its own voltage, which leads to a rotation of the crystals, and hence a change in the refractive index. Cell groups are controlled by independently supplied voltage, which makes it possible to control simultaneously several light beams incident each on the corresponding region of SLM cells. The surface area of the SLM is divided into two areas reserved for the receiving and transmitting channels. Laser radiation reflected from the corresponding SLM region enters the receiver collimator, and laser radiation emerging from the transmitter collimator is reflected from the SLM and propagates towards the paired subscriber unit. The control panel is connected to a control unit that encodes / decodes information, controls the control panel, pattern calculation and SLM control. The SLM provides precise guidance and focusing using the average optical signal power recorded by the receiver as feedback.

The receiving channel of Device 1 is optically coupled to the transmitting channel of Device 2, and the transmitting channel of device 1 is optically coupled to the receiving channel of device 2.

The receiving and transmitting modules can operate in quantum mode. For this, the signal level of the transmitting device is reduced to the level of single photons, and the detector uses a single photon detector. The laser needed to form the quantum optical channel also serves as a guidance laser when operating at high power. After pointing to Device 2, the laser switches to low power mode, and on Device 2 the receiving equipment of the quantum channel is launched.

In the areas of the SLM matrix corresponding to the receiver and transmitter of each subscriber, patterns are generated corresponding to a flat lens of arbitrary focal length, located arbitrarily to the beam axis. With the help of the formed lenses replacing the movable lenses, an independent change in direction and focusing of the beams corresponding to the receiver and transmitter occurs on the SLM; tuning, focusing of several light beams simultaneously without changing the relative position of the mechanical elements of the optical system.

The control of the number of channels, greater than 2, and the further splitting of the SLM into a larger number of regions is carried out completely similarly to the control of two beams.

By applying to the SLM a special type of pattern, using methods similar to [2], the aberrations caused by, for example, the passage of beams through a turbulent atmosphere are corrected.

USED MATERIALS

[1] US Patent US 7,283,291 B2 High speed beam steering / field of view adjustment

[2] US Patent 9,917,989 B2

[3] Japanese Patent No. 25122, 1969

[4] Patent RU 2328077

[5] Mane-Si Laure Lee, Brigitte Loiseaux, Daniel Dolfi, Sylvie Tonda & Jean-Pierre Huignard "Review of Information Display Vol. 3 (3), p 24-29 (2002)

[6] Uzi Efron "Spatial of liquid crystal spatial light modulators at Thales research & technology: Technology and applications" Journal Light Modulators: Technology and Applications)) Proceedings of SPIE (2001)

Claims (6)

1. System for simultaneous control of at least two laser beams using a fixed liquid crystal matrix, containing two identical transceiver nodes with a laser and a photodiode, between which optical communication is made through free space, each transceiver node contains an inclined rotary platform (PUF), controlled by a control unit on which a liquid crystal matrix (SLM) is located, characterized in that each transceiver is connected via fiber optical cables with at least two collimators, and the control unit controls the PUF, pattern calculation and SLM control in such a way that there is an independent change in direction and focusing of the beams corresponding to the receiver and transmitter, while the liquid crystal matrix contains an array of pixels consisting of liquid crystals, placed between two electrodes and placed on the surface of the specified matrix; the specified surface of the matrix is divided into at least two areas reserved for the receiving and transmitting channels; one of these electrodes is solid, and the other is divided into cells configured to simultaneously control the light beams by means of an independently applied voltage, while a mirror is used on the electrode divided into cells to reflect the incident signal, and a cover mirror is located on the solid electrode for guard. 2. The system according to claim 1, characterized in that the laser beams are focused at an angle of 0.3 radians relative to the angle of incidence. 3. The system according to claim 1, characterized in that the focal lengths corresponding to the patterns of different rays differ by a factor of 2. 4. The system according to claim 1, characterized in that the region of orientation change of the tilting-rotating mechanical platform is 2π steradian. 5. The system according to p. 1, characterized in that the guidance on the coordinates of the transceiver nodes is carried out from satellite navigation systems GPS / GLONASS. 6. The system according to claim 1, characterized in that the receiving and transmitting devices are configured to operate in quantum mode, where the level of the transmitting signal is reduced to the level of single photons, and single photon detectors are used in the receiving part of the devices.

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