A multi-channel chaotic laser generating device and a chaotic laser generating method

Abstract

The application provides a multi-channel chaotic laser generating device and a laser generating method. The laser generating device provided by the application comprises a chaotic laser generating module, which is used for generating chaotic laser; a vortex multiplexing module, which is used for enabling the chaotic laser to carry multi-order OAM information; and an information collecting module, which is used for collecting the chaotic laser carrying multi-order OAM information emitted by the vortex multiplexing module. The device has a simple structure, can achieve double security of an optical communication system, can improve the communication capacity of the system, can realize high-speed, secure and free-space laser secure communication, can provide a possibility for utilization of the spatial dimension of chaotic light beams, can improve the capacity of optical communication while realizing information secure transmission, and can achieve technical effects by only simulating new multi-order multiplexing phase plate images and loading the images on the vortex multiplexing module when parameters and actual demands change, without the need of increasing or decreasing components, and the operation is simple and flexible.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical communication, and particularly relates to a multi-channel chaotic laser generating device and a chaotic laser generating method. BACKGROUND

[0002] In recent years, with the rapid development of the semiconductor industry and information technology, the Internet industry has risen, and higher requirements have been put forward for the transmission capacity and security of the communication system. Chaotic laser is a signal similar to noise signal in time domain waveform and spectrum, and its typical characteristics are initial value sensitivity and long-term unpredictability. As a physical layer encryption means, the security of the chaotic signal mainly depends on the hardware parameters of the device, and therefore has better security performance than traditional algorithm encryption mode. Vortex beam is a special light field carrying orbital angular momentum (OAM) and having a unique spiral phase structure, and its phase expression is exp (ilθ), wherein l is a topological charge number, and θ is an azimuth angle. Vortex beams with different topological charge numbers are orthogonal to each other, which provides a possibility for the multiplexing of communication in the spatial dimension, and is of great significance to improve the communication capacity. In addition, the information demodulation of OAM communication needs to receive the light field completely, and the tilt and incomplete reception can reduce the probability of correctly demodulating information, and therefore can further enhance the security of the free space optical communication system in the physical layer. In summary, if the vortex multiplexing technology and chaotic laser are combined, the optical communication system can be doubly encrypted, and the capacity of the optical communication can be improved.

[0003] In recent years, the researches on chaotic laser at home and abroad mainly focus on proposing various methods with complex light feedback configurations to break the inherent relaxation oscillation effect of the external cavity semiconductor laser, so as to improve the bandwidth of the chaotic carrier, and however, the development and utilization of the spatial dimension of the chaotic laser are rarely reported. SUMMARY

[0004] In view of the problems in the prior art, the application provides a multi-channel chaotic laser generating device and a laser generating method. The device has a simple structure, can achieve double security of the optical communication system, can improve the communication capacity of the system, and realizes high-speed, secure and free space laser secure communication.

[0005] To achieve the above technical purpose, the technical scheme adopted by the application is:

[0006] A multi-channel chaotic laser generating device, comprising:

[0007] a chaotic laser generating module, configured to generate chaotic laser,

[0008] a vortex multiplexing module, configured to enable the chaotic laser to carry multi-order OAM information,

[0009] an information collection module, configured to collect the chaotic laser carrying the multi-order OAM information emitted by the vortex multiplexing module.

[0010] As a preferred solution, the vortex multiplexing module is loaded with a multi-order multiplexing phase plate, and the multi-order multiplexing phase plate is an image file,

[0011] The chaotic laser emitted by the laser generation module is incident into the vortex multiplexing module, and a required multi-order multiplexing phase plate can be calculated and simulated according to Formula 1, and the chaotic laser can generate chaotic laser carrying multi-order orbital angular momentum information after being modulated by the multi-order multiplexing phase plate,

[0012] (1)

[0013] wherein l and p are respectively a topological charge number and a radial index, θ is an azimuthal angle, ω0 is a beam waist radius, r is a radial component of a cylindrical coordinate, and i is an imaginary unit.

[0014] As a preferred solution, the multi-order multiplexing phase plate is a second-order multiplexing phase plate, and the chaotic laser can generate chaotic laser carrying second-order OAM information after being modulated by the second-order multiplexing phase plate, and a required second-order multiplexing phase plate can be calculated and simulated according to Formula 2,

[0015] (2)

[0016] wherein, , l1 and l2 are respectively topological charge numbers of two beams of Laguerre-Gaussian (LG) light beams, and in the formula, .

[0017] The generation process of the two beams of Laguerre-Gaussian (LG) light beams is as follows: the laser generated by the chaotic laser generation module is incident onto an SLM through a chaotic laser vortex multiplexing module, the SLM is loaded with a second-order OAM multiplexing phase plate, the SLM modulates the spatial phase of the chaotic laser, and the modulated beam of chaotic laser carries second-order OAM information.

[0018] As a preferred solution, the multi-order multiplexing phase plate is obtained by simulation on a computer through a commonly used simulation software, and then the simulated multi-order multiplexing phase plate is loaded onto a spatial light modulator of the vortex multiplexing module. Common simulation software includes Maple, MATLAB, Mathematica, etc., and all of them can achieve the technical effects of the present application.

[0019] As a preferred solution, the vortex multiplexing module comprises a mechanically adjustable linear polarizer (LP) and a spatial light modulator (SLM), the multi-order multiplexing phase plate is loaded on the SLM, the chaotic laser emitted by the laser generation module is adjusted by the LP, and then is incident on the SLM, and after phase modulation by the SLM, chaotic laser carrying multi-order OAM information is generated.

[0020] Preferably, the mechanically adjustable linear polarizer can adjust the polarization state of the chaotic laser emitted by the laser generation module to linear polarization, and by rotating the direction of the linear polarizer, the polarization direction of the incident chaotic laser is adjusted to be consistent with the direction of the extraordinary light (e light) refractive index of the SLM. Preferably, the SLM is a reflective liquid crystal spatial light modulator.

[0021] As a preferred solution, the chaotic laser generation module comprises a distributed feedback laser (DFB), a polarization controller (PC), a fiber coupler (FC), a variable optical attenuator (VOA), a fiber mirror (M), and an isolator (OI) arranged along the laser emission direction.

[0022] As a preferred solution, the signal acquisition module comprises a fiber coupler (Col.2), a photodetector (PD), and an oscilloscope (OSC) arranged along the laser emission direction. After the multi-order vortex multiplexing chaotic laser passes through Col.2, it is captured by PD, and finally the time-domain waveform of the chaotic laser carrying multi-order OAM multiplexing information is collected and analyzed by OSC.

[0023] The FC is used for beam splitting or coupling in the optical fiber link, and the Col.2 is used for coupling spatial light into the optical fiber.

[0024] The collection of the spatial light field of the chaotic laser carrying multi-order OAM multiplexing information only needs a CCD (Charge-coupled Device, CCD), which is not shown in the drawings of the present patent, and the CCD is a prior art, which will not be described in the present application.

[0025] By using the above device, the present application further provides a chaotic laser generation method, comprising the following steps:

[0026] S1: a chaotic laser generation module generates chaotic laser;

[0027] S2: based on the light field superposition principle shown in formula 1, a multi-order multiplexed phase plate image is simulated and generated, and the multi-order multiplexed phase plate image is loaded on an SLM of a vortex multiplexing module;

[0028] (1)

[0029] Wherein, l and p are respectively the topological charge number and the radial index, θ is the azimuth angle, ω0 is the beam waist radius, r is the radial component of the cylindrical coordinate, and i is the imaginary unit;

[0030] S3: the vortex multiplexing module modulates the phase of the chaotic laser emitted by the chaotic laser generation module, so that it carries multi-order OAM information;

[0031] S4: the signal acquisition module respectively acquires the time domain waveform and the spatial light field of the multi-order vortex multiplexed chaotic laser emitted by the vortex multiplexing module.

[0032] The advantages of the present application are:

[0033] 1. The multi-channel chaotic laser generation device provided by the present application has simple structure, provides the possibility for the use of spatial dimension of chaotic light beams, realizes information secret transmission, and improves the capacity of optical communication;

[0034] 2. When the parameters and actual requirements change, the present application only needs to simulate and output new multi-order multiplexed phase plate images loaded on the vortex multiplexing module to achieve the technical effect, without the need to increase or decrease components, and the operation is simple and flexible. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the multi-channel chaotic laser generation device provided in an embodiment of the present application;

[0036] Figure 2 It is the light field distribution of the 1st order and 3rd order vortex light beam multiplexing provided in an embodiment of the present application;

[0037] Figure 3 It is the phase distribution of the 1st order and 3rd order vortex light beam multiplexing provided in an embodiment of the present application;

[0038] Figure 4 It is the time domain waveform and power spectrum of the chaotic laser carrying multi-order OAM information provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] The features and exemplary embodiments of various aspects of the present application will be described below in detail, in order to make the purposes, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, but not to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0040] In one specific embodiment of the present application, as shown in Figure 1 A multi-channel chaotic laser generating device is provided, comprising:

[0041] a chaotic laser generating module for generating chaotic laser,

[0042] a vortex multiplexing module for carrying multi-order OAM information by the chaotic laser,

[0043] an information acquisition module for acquiring the chaotic laser carrying multi-order OAM information emitted by the vortex multiplexing module.

[0044] In one embodiment of the present application, the vortex multiplexing module is loaded with a multi-order multiplexing phase plate, and the multi-order multiplexing phase plate is an image file,

[0045] The chaotic laser emitted by the laser generating module is incident into the vortex multiplexing module, and the required multi-order multiplexing phase plate can be calculated according to formula 1, and the chaotic laser carrying multi-order orbital angular momentum (OAM) information can be generated after the chaotic laser passes through the modulation of the multi-order multiplexing phase plate,

[0046] (1)

[0047] Wherein, l and p are respectively the topological charge number and the radial index, θ is the azimuth angle, ω0 is the beam waist radius, r is the radial component of the cylindrical coordinate, and i is the imaginary unit.

[0048] In one embodiment of the present application, the laser generated by the chaotic laser generating module is chaotic laser in time domain, and is still Gaussian beam in spatial distribution, and after the phase is modulated by the SLM loaded with the vortex phase plate, the Laguerre-Gaussian beam (LG) is formed.

[0049] For the Laguerre-Gaussian (LG) beam, at p=0, z=0, the composite vortex light field after superposition of multiple LG beams can be expressed as:

[0050]

[0051] Wherein, z is the transmission distance, the meaning of other physical parameters is as described above, which will not be repeated here.

[0052] In one embodiment of the present application, the multi-order multiplexed phase plate is a second-order multiplexed phase plate. The chaotic laser passes through the modulation of the second-order multiplexed phase plate to generate chaotic laser carrying second-order OAM information, and the superposition of two-order LG beams (l1, l2) is produced. According to the above formula, the phase information after superposition is:

[0053]

[0054] Wherein, , , l1 and l2 are the topological charge numbers of two chaotic laser beams, and in the formula .

[0055] According to the above formula, the required multi-order multiplexed phase plate image can be calculated and simulated. The chaotic laser passes through the modulation of the SLM loaded with the second-order multiplexed phase plate to become a second-order vortex multiplexed chaotic laser.

[0056] In one embodiment of the present application, the multi-order multiplexed phase plate is obtained by simulating on a computer through a commonly used simulation software, and the simulated multi-order multiplexed phase plate is directly loaded onto the vortex multiplexing module.

[0057] In one embodiment of the present application, the vortex multiplexing module comprises a linear polarizer and a spatial light modulator. The multi-order multiplexed phase plate is loaded on the SLM. The chaotic laser emitted by the laser generating module passes through the adjustment of the LP and then is incident on the SLM. After the phase modulation of the SLM, the chaotic laser carrying multi-order vortex phase information is generated.

[0058] Here, the loading is to display the multiplexed phase plate picture on the liquid crystal screen of the spatial light modulator through software.

[0059] In one embodiment of the present application, the linear polarizer can adjust the polarization state of the chaotic laser emitted by the laser generating module to linear polarization. The polarization direction of the incident chaotic laser is consistent with the extraordinary light (e light) refractive index direction of the SLM. When the refractive index directions are consistent, the maximum modulation efficiency can be obtained.

[0060] Specifically, the linear polarizer used in the present application can be a mechanical linear polarizer, and the polarization direction of the incident chaotic laser is adjusted to the required direction through mechanical adjustment. In one embodiment of the present application, the SLM is a reflective liquid crystal spatial light modulator. The chaotic laser is incident on the surface of the SLM. The SLM loads the multi-order multiplexed phase plate image. After the phase modulation of the chaotic laser, it is reflected to become chaotic laser carrying multi-order OAM information.

[0061] In one embodiment of the present application, the chaotic laser generation module comprises a distributed feedback laser, a polarization controller, a fiber coupler, an adjustable optical attenuator, a fiber mirror, a fiber isolator arranged along the laser emission direction.

[0062] In actual working conditions, the laser emitted by the distributed feedback laser passes through the polarization controller, the fiber coupler and the adjustable optical attenuator to reach the fiber mirror. After the reflection of the laser by the fiber mirror, the adjustable optical attenuator further controls the intensity of the reflected light, which is fed back to the active region of the distributed feedback laser, thereby disturbing the steady state of the distributed feedback laser and making it enter the chaotic state. The chaotic laser is then emitted again. The chaotic laser passes through the fiber isolator and the collimator and is emitted into the vortex multiplexing module.

[0063] In the present application, the polarization controller is used to adjust the polarization state of the laser; the collimator is used to collimate the emitted chaotic laser; the fiber coupler is used to divide the laser emitted by the distributed feedback laser into two paths; and the fiber isolator controls the one-way passage of the chaotic laser, thereby blocking the return of the chaotic laser to the chaotic laser generation system.

[0064] In one embodiment of the present application, the signal acquisition module comprises a fiber coupler, a photodetector and a high-speed oscilloscope arranged along the laser emission direction. The multi-order vortex multiplexing chaotic laser passes through the fiber coupler, is captured by the photodetector, and is finally collected and analyzed by the high-speed oscilloscope in the time domain. Since the vortex beam is a spatial dimension light field distribution, a CCD can be used to collect its light field distribution, which is not indicated in the figure.

[0065] The structural diagram of the chaotic laser generation device provided in one embodiment of the present application is shown in Figure 1 .

[0066] Using the above device, the present application further provides a chaotic laser generation method, comprising the following steps:

[0067] S1: The chaotic laser generation module generates chaotic laser;

[0068] S2: Based on the light field superposition principle shown in formula 1, a multi-order multiplexing phase plate image is simulated and calculated, and the multi-order multiplexing phase plate image is loaded on the vortex multiplexing module;

[0069] (1)

[0070] Wherein, l and p are the topological charge number and the radial index, respectively, θ is the azimuth angle, ω0 is the beam waist radius, r is the radial component of the cylindrical coordinate, and i is the imaginary unit;

[0071] S3: The vortex multiplexing module modulates the phase of the chaotic laser emitted by the chaotic laser generation module to generate chaotic laser carrying multi-order OAM information;

[0072] S4: The signal acquisition module acquires the time-domain waveform and spatial light field distribution of the multi-order vortex multiplexing chaotic laser emitted by the vortex multiplexing module.

[0073] According to formula 1, the phase information of the superimposed light field is taken to generate a multi-order multiplexed phase plate image, and this step can be operated by using common mathematical simulation software.

[0074] The technical solutions of the present application will be further described below in combination with the drawings and specific embodiments.

[0075] The chaotic laser generated by the emitted light of the DFB laser after the external optical feedback structure has a central wavelength of 1550 nm. After the collimator is emitted, the beam waist radius ω0 of the chaotic laser is 1.875 mm.

[0076] Taking two-order OAM multiplexing as an example, l1 and l2 are respectively set to 1 and 3, and through the simulation calculation of formula (2) P phase , the light field at z=0 position after 1-order and 3-order vortex beams are multiplexed Figure 2 and the 2-order multiplexed phase plate Figure 3 can be obtained.

[0077] After the vortex phase plate shown in Figure 3 is loaded into the spatial light modulator, the phase modulation of the chaotic laser emitted by the DFB can be performed. The originally spatially distributed Gaussian chaotic laser is modulated into chaotic laser carrying 1-order and 3-order OAM. Figure 2 , Figure 3 The horizontal and vertical coordinates have no actual physical meaning, and are the cross section along the axial direction of the beam propagation.

[0078] After the time-domain waveform and power spectrum of the chaotic laser of the composite vortex light field are acquired by the high-speed oscilloscope OSC, as shown in Figure 4 , the time-domain waveform shows the irregular noise-like characteristics, and the power spectrum shows that the effective bandwidth of the chaotic laser is 8.5 GHz, which shows that the evolution of the spatial light field does not affect the time-domain and frequency-domain characteristics of the chaotic laser.

Claims

1. A multi-channel chaotic laser generator, characterized in that, include: A chaotic laser generator module is used to generate chaotic lasers. A vortex multiplexing module is used to enable chaotic lasers to carry multi-order OAM information. The information acquisition module is used to acquire chaotic lasers carrying multi-order OAM information emitted from the vortex multiplexing module; The vortex multiplexing module loads a multi-level multiplexed phase board, which is an image file. The chaotic laser emitted from the laser generating module is incident on the vortex multiplexing module. The required multi-order multiplexing phase plate can be calculated according to Formula 1. After being modulated by the multi-order multiplexing phase plate, the chaotic laser can generate a chaotic laser carrying multi-order OAM information. (1) in, For the complex electric field distribution of the multiplexed beam, l n Let θ be the topological charge number of different OAM beams (n = 1, 2, 3, ..., N, where N is an integer), θ be the azimuth angle, ω0 be the beam waist radius, r be the radial component of the cylindrical coordinates, and i be the imaginary unit.

2. The multi-channel chaotic laser generator according to claim 1, characterized in that: The multi-order multiplexed phase plate is a second-order multiplexed phase plate. After being modulated by the second-order multiplexed phase plate, the chaotic laser can generate a chaotic laser that simultaneously carries second-order OAM information. At this time, the required second-order multiplexed phase plate can be calculated and simulated according to Formula 2. （2） Among them, P phase To superimpose the phase of the beam, Let represent the complex electric field distribution of the second-order multiplexed beam. l1 and l2 are the topological charges of the two Laguerre-Gaussian (LG) beams, respectively. A(r) is the electric field envelope amplitude, primarily reflecting how the intensity of the light field attenuates with radial distance θ. B(r, l) is the radial component of the electric field, describing how the beam distribution in the radial direction changes with the topological charge l. B(r, l1) and B(r, l2) describe the radial component of the electric field distribution with topological charges l1 and l2, respectively. θ is the azimuth angle, r is the radial component of the cylindrical coordinates, and i is the imaginary unit. , In the formula ω0 is the waist radius.

3. The multi-channel chaotic laser generator according to claim 1, characterized in that: The vortex multiplexing module includes an LP and an SLM. The multi-order multiplexing phase plate is loaded on the SLM. The chaotic laser emitted by the chaotic laser generation module is adjusted by the LP and then incident on the SLM. After phase modulation by the SLM, a chaotic laser carrying multi-order OAM information can be generated.

4. The multi-channel chaotic laser generator according to claim 3, characterized in that: The SLM is a reflective liquid crystal spatial light modulator.

5. The multi-channel chaotic laser generator according to claim 1, characterized in that: The chaotic laser generating module includes a distributed feedback laser, a polarization controller, an optical fiber coupler, a tunable optical attenuator, an optical fiber mirror, an optical fiber isolator, and a collimator arranged along the laser emission direction.

6. The multi-channel chaotic laser generator according to claim 1, characterized in that: The information acquisition module includes an optical fiber coupler, a photodetector, and a high-speed oscilloscope arranged along the laser emission direction. The chaotic laser carrying multi-order OAM information is captured by the photodetector after passing through the optical fiber coupler, and finally the time-domain waveform of the chaotic laser is acquired and analyzed by the high-speed oscilloscope.

7. A chaotic laser generation method based on the multi-channel chaotic laser generator according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: The chaotic laser generation module generates chaotic laser; S2: Based on the principle of light field superposition shown in Formula 1, simulate and calculate to generate a multi-level multiplexed phase plate image, and load the multi-level multiplexed phase plate image into the vortex multiplexing module; (1) in, For the complex electric field distribution of the multiplexed beam, l n For different OAM beams, the topological charge number is (n=1, 2, 3, ..., N, where N is an integer), θ is the azimuth angle, ω0 is the beam waist radius, r is the radial component of the cylindrical coordinates, and i is the imaginary unit; S3: The vortex multiplexing module modulates the phase of the chaotic laser emitted from the chaotic laser generator module, enabling it to carry multi-order OAM information. S4: The information acquisition module acquires the temporal waveform and spatial optical field of the multi-order vortex multiplexed chaotic laser emitted from the vortex multiplexing module.

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