Emission device for inhibiting light intensity flicker by using awnward light beam

Abstract

The invention discloses a transmitting device for inhibiting light intensity flicker by using a sharp light beam. The transmitting device comprises a laser generation module and a phase modulation module. A Gaussian beam is emitted from the laser generation module, is subjected to phase modulation by the phase modulation module and then becomes a frontal beam, the frontal beam is emitted into a space for transmission, and a light intensity flicker suppression effect can be realized at a receiving end. The transmitting device for inhibiting light intensity flicker solves the problem of poor real-time performance of a self-adaptive optical system at the transmitting end, is simple in structure, low in cost and easy to implement, reduces the maintenance difficulty and cost of the system, and can obtain higher receiving power and smaller light intensity flicker results.

Description

Technical Field

[0001] The invention belongs to the field of space laser communication and space laser transmission, and in particular to a transmitting device for suppressing light intensity flicker based on a sharp light beam, which can be applied to a system transmitting end to suppress light intensity flicker of an output laser. Background Art

[0002] Light waves transmitted in the atmosphere will produce turbulence effects such as light intensity flicker, wavefront distortion, and beam drift. Light intensity flicker seriously affects the beam quality of the transmitted laser. Suppressing the flicker of atmospheric turbulence has always been a very important research topic in the field of space laser communication and space laser transmission.

[0003] At present, the main method to solve the problem of light intensity flicker is to introduce adaptive optical technology at the transmitter end. By measuring the distorted phase of the beacon light passing through the entire link and using a deformable mirror to load the conjugate distorted phase to compensate the optical path, the light intensity flicker of the signal light can be effectively suppressed. Transmitter-end adaptive optical technology has good turbulence suppression effect and mature technology, and has been widely used in aerospace monitoring, astronomical observation and other fields. However, there are certain limitations in using transmitter-end adaptive optical technology to suppress light intensity flicker. For example, for long-distance space laser communications, when the uplink and downlink paths are inconsistent, that is, the wavefront advance angle is large, the feedback distorted wavefront is poor in real time, resulting in a decrease in flicker suppression effect. In order to solve the problem of untimely feedback from the transmitter-end adaptive optical system, it is very necessary to find a new transmitter-end flicker suppression method.

[0004] The sharp beam is synthesized by multiple radially symmetric Airy beams. The symmetrical Airy beams in all directions interfere with each other to eliminate the transverse wave vector, so that the beam can be stably transmitted in turbulence and reduce the light intensity flicker effect. Many teams have studied the sharp beam since its discovery, proving that it can maintain stable transmission at the kilometer level, and it is expected to become an important technology to solve the light intensity flicker effect caused by atmospheric turbulence, providing a solid guarantee for laser transmission. Summary of the invention

[0005] In order to overcome the problem of poor real-time performance of the existing adaptive optical system at the transmitting end in suppressing light intensity flicker, the present invention provides a transmitting device that uses a sharp light beam to suppress light intensity flicker. The device can effectively improve the receiving power of the system, reduce the light intensity flicker index at the receiving end when the laser is transmitted in the atmosphere, and significantly improve the availability of the space laser system.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A transmitting device that uses a sharp beam to suppress light intensity flickering, the device comprises a laser generating module and a phase modulation module, wherein:

[0008] The laser generating module is used to generate and emit a Gaussian beam;

[0009] The phase modulation module includes a sharp phase screen. The Gaussian beam is phase modulated by the sharp phase to become a sharp beam, which is emitted into space for transmission.

[0010] Furthermore, the wavelength of the Gaussian beam output by the laser generation module is , the waist radius is , the polar diameter of the polar coordinate system is , then the complex amplitude of the Gaussian beam is The expression is:

[0011] (1)

[0012] When the Gaussian beam passes through the sharp phase screen, the sharp phase will be loaded onto the Gaussian beam. The modulation depth of the sharp phase is The modulation index is , k is the wave vector, is the phase normalization coefficient, i is the imaginary unit, then the sharp phase The expression is:

[0013] ] (2)

[0014] Complex amplitude of a Gaussian beam loaded with sharp phase for:

[0015] ] (3)

[0016] After the Gaussian beam is loaded with the sharp phase, it becomes a sharp beam. After the sharp beam is transmitted in space for a distance L, the intensity flicker index of the sharp beam is obtained. :

[0017] (4)

[0018] In the formula, Indicates the average received power.

[0019] Furthermore, a turbulence phase screen is provided behind the edge phase screen to simulate the influence of atmospheric turbulence on the edge beam. The turbulence intensity is recorded as D / r0, where D is the beam aperture, r0 is the atmospheric coherence length, and the turbulence wavefront phase introduced by the turbulence phase screen is recorded as , the beam expression after the turbulent phase screen is becomes:

[0020] ](5).

[0021] Furthermore, the laser generation module includes a laser output fiber head and a collimating lens which are sequentially arranged along the optical path, and the divergence angle of the output Gaussian beam is adjusted by adjusting the relative position of the laser output fiber head and the collimating lens.

[0022] Furthermore, a telescope module is arranged after the phase modulation module for laser beam expansion and emission.

[0023] Furthermore, the edge phase screen or turbulent phase screen is realized based on a spatial light modulator or a phase plate or a deformable mirror.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The present invention discloses a transmitting device that uses a sharp light beam to suppress light intensity flicker. By using a sharp light beam at the transmitting end of a space laser system, the problem of low receiving power and high light intensity flicker index at the receiving end of the system is effectively solved, and the light intensity flicker caused by atmospheric turbulence is well suppressed.

[0026] Compared with the existing adaptive optical technology for suppressing the light intensity flicker effect at the transmitting end, the system of the present invention has a simple structure, low cost, high real-time turbulence suppression and good effect. The use of a sharp light beam to suppress light intensity flicker does not require the introduction of a complex correction system and algorithm. Only by using a modulation device at the transmitting end, a sharp light beam with kilometer-level transmission and concentrated energy can be obtained to suppress the light intensity flicker problem caused by atmospheric turbulence. It can effectively improve the receiving power of the space laser system and reduce the light intensity flicker index of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural diagram of a transmitting device that uses a sharp light beam to suppress light intensity flickering according to the present invention;

[0028] Figure 2 is the sharp phase image loaded during the implementation of the present invention;

[0029] Figure 3 This is a turbulence-free far-field image obtained at 1 km using the device of the present invention;

[0030] Figure 4 These are 9 groups of turbulent wavefront phase images used in the implementation of the present invention;

[0031] Figure 5 This is the far-field image with turbulence obtained by a Gaussian beam at 1 km;

[0032] Figure 6 This is a far-field image with turbulence obtained at 1 km during the implementation of the present invention;

[0033] Figure 7The average received power diagram of the far field of the Gaussian beam and the sharp beam after modulation using the device of the present invention.

[0034] Reference numerals:

[0035] 101-laser output fiber head, 102-collimator, 201-edge phase screen, 202-turbulent phase screen, 1-laser generation module, 2-phase modulation module, 3-telescope module. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] In space laser systems, the light intensity flicker effect caused by atmospheric turbulence has a great impact on the average power and signal jitter of the received signal, and the transmitting end adaptive optical system has the problems of poor real-time performance and complex structure. Therefore, the present invention uses the anti-turbulence characteristics of the sharp beam itself and uses the sharp beam as the transmitting beam to correct the flicker effect and simplify the turbulence suppression system. Figure 1 In the laser generating module 1, the wavelength of the Gaussian beam outputted by the laser output fiber head 101 and the collimator 102 is =1550nm, beam waist radius =100mm, represents the polar diameter of the polar coordinate system, and the telescope aperture D in telescope module 3 is 200 mm. The complex amplitude of the Gaussian beam The expression is:

[0038] (1)

[0039] Without adding the phase modulation module 2, the Gaussian beam of the laser generation module 1 is directly emitted into space through the telescope module 3 for transmission, or it can be directly output into space through the phase modulation module 2 without the telescope module 3, and the transmission distance L=1km. The sampling screen has an aperture of 900mm, the number of sampling points N=900×900, which is placed perpendicular to the optical axis, and the receiving aperture is a circular aperture of 100mm in the center of the receiving screen, and the Gaussian spot diameter in the far field is obtained. 200mm, receiving power au;

[0040] Then, a phase modulation module 2 is added behind the laser generation module 1, wherein the phase modulation module only includes a sharp phase screen 201. The sharp phase screen 201 can be based on a spatial light modulator or a phase plate. This embodiment uses a sharp phase screen 201 based on a spatial light modulator, and its normalized phase factor , 1.5, modulation depth , k is the wave vector, i is the imaginary unit, and the modulation depth , modulation index , k is the wave vector, i is the imaginary unit, and the modulation depth , modulation index , load the following edge phase:

[0041] ] (2)

[0042] Complex amplitude of a Gaussian beam loaded with sharp phase for:

[0043] ] (3)

[0044] The edge phase distribution is as follows Figure 2 As shown in the figure, after being transmitted 1 km in space, the received far-field light spot is as follows Figure 3 As shown, the far-field spot diameter of the sharp beam can be obtained =34.4mm, received power =13261a.u.

[0045] Furthermore, a turbulent phase screen 202 is added after the sharp phase screen 201, and the modulated sharp beam is compared with the Gaussian beam before modulation after passing through the turbulent environment. The simulation is performed for an environment with a turbulence intensity of D / r0=10. Figure 4 The figure shows the schematic diagram of the first nine groups of turbulent wavefronts, where D is the telescope aperture and r0 is the atmospheric coherence length. The Gaussian beam without the modulation of the sharp phase screen 201 is output by the laser generation module 1, and is emitted after passing through the turbulent phase screen 202 and the telescope module 3 in sequence. After transmitting a distance L in space, the received far-field light spot is as follows: Figure 5 As shown, the average received power is au, flicker index =0.2145. Before the turbulent phase screen 202 and after the collimator 102 of the laser generating module 1, the sharp phase screen 201 shown in formula (2) is added to modulate the Gaussian beam. The generated sharp beam passes through the turbulent phase screen 202 and the telescope module 3 in sequence and is emitted. After transmitting a distance L in space, the received far-field light spot is as follows: Figure 6 As shown, the average received power au, flicker index Calculated according to the following formula:

[0046] (4)

[0047] The scintillation index of the sharp beam is =0.0356.

[0048] The turbulence wavefront phase introduced by the turbulence phase screen 202 is recorded as , the beam expression after the turbulent phase screen 202 is becomes:

[0049] ] (5)

[0050] Figure 7 The average received power diagram of the far field of the Gaussian beam without turbulence phase screen 202 modulation and the sharp beam after turbulence phase screen 202 modulation can be clearly found that after the sharp phase screen 202 modulation, the average received power at the receiving end is increased by 130.95%, and the scintillation index is Reduced by 5.03 times.

[0051] It can be seen from the above embodiments that in a space laser system, the problem of reduced average received power and light intensity flickering caused by atmospheric turbulence can be corrected using the sharp beam method, which has good real-time performance, a simple system and significant effects.

[0052] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A transmitting device that uses a sharp beam to suppress light intensity flicker, characterized in that: The device comprises a laser generating module and a phase modulation module, wherein: The laser generating module is used to generate and emit a Gaussian beam; The phase modulation module includes a sharp phase screen. The Gaussian beam is phase modulated by the sharp phase to become a sharp beam, which is emitted into space for transmission.

2. The emitting device for suppressing light intensity flicker using a sharp beam according to claim 1, characterized in that: The wavelength of the Gaussian beam output by the laser generation module is , the waist radius is , the polar diameter of the polar coordinate system is , then the complex amplitude of the Gaussian beam is The expression is: （1） When the Gaussian beam passes through the sharp phase screen, the sharp phase will be loaded onto the Gaussian beam. The modulation depth of the sharp phase is The modulation index is , k is the wave vector, is the phase normalization coefficient, i is the imaginary unit, then the sharp phase The expression is: ]（2） Complex amplitude of a Gaussian beam loaded with sharp phase for: ]（3） After the Gaussian beam is loaded with the sharp phase, it becomes a sharp beam. After the sharp beam is transmitted in space for a distance L, the intensity flicker index of the sharp beam is obtained. : （4） In the formula, Indicates the average received power.

3. The emitting device for suppressing light intensity flicker using a sharp beam according to claim 2, characterized in that: A turbulence phase screen is also provided behind the edge phase screen to simulate the influence of atmospheric turbulence on the edge beam. The turbulence intensity is recorded as D / r0, where D is the beam aperture, r0 is the atmospheric coherence length, and the turbulence wavefront phase introduced by the turbulence phase screen is recorded as , the beam expression after the turbulent phase screen is becomes: ]（5）。 4. The emitting device for suppressing light intensity flicker using a sharp beam according to claim 1, characterized in that: The laser generating module comprises a laser output fiber head and a collimating lens which are sequentially arranged along the optical path. The divergence angle of the output Gaussian beam is adjusted by adjusting the relative positions of the laser output fiber head and the collimating lens.

5. The emitting device for suppressing light intensity flicker using a sharp beam according to claim 1, characterized in that: The phase modulation module is followed by a telescope module for laser beam expansion and emission.

6. The emitting device for suppressing light intensity flicker using a sharp beam according to claim 1, characterized in that: The edge phase screen or turbulent phase screen is realized based on a spatial light modulator or a phase plate or a deformable mirror.

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