Rapid dynamic separation method and device for radial and angular polarization components of light beam

Abstract

The invention belongs to the technical field of optics, and particularly relates to a rapid dynamic separation method and device for radial and angular polarization components of a light beam, and efficient and dynamic polarization component separation is realized by using the birefringence characteristic of an SBN uniaxial crystal and applying an adjustable electric field to the crystal in combination with an external electric field module. According to the method, radial and angular polarization components can be gradually separated and focused on different focuses in the propagation process, the positions of the focuses are flexibly controlled by adjusting the direction and size of the external electric field, and higher flexibility and accuracy are provided. Therefore, the flexibility and efficiency in the fields of optical control, high-resolution imaging, optical communication, quantum information processing and the like are remarkably improved, and more efficient and accurate light beam processing technical support is provided for the applications.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and particularly relates to a method and device for rapidly and dynamically separating the radial and angular polarization components of a light beam. Background Art

[0002] In the field of optical technology, the separation and manipulation of polarized light are key steps in many applications, including optical manipulation, high-resolution imaging, optical communication, and quantum information processing. Traditional methods mainly rely on devices such as polarization beam splitters (PBS) to separate two mutually orthogonal linearly polarized components. However, these methods have a significant technical problem: they cannot efficiently and dynamically separate the radial and angular polarization components in a light beam.

[0003] Traditional polarization elements such as polarization beam splitters (PBS) can only separate two mutually orthogonal linearly polarized components and cannot achieve efficient dynamic separation of the radial and angular polarization components in a light beam. This limits the flexibility and efficiency in applications that require precise control of the radial and angular polarization components. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for rapidly and dynamically separating the radial and angular polarization components of a light beam. By utilizing the birefringence characteristics of an SBN uniaxial crystal and combining an external electric field module to apply an adjustable electric field to the crystal, dynamic separation of the radial and angular polarization components of the light beam is achieved, so as to solve the problems proposed in the above background art.

[0005] To achieve the above purpose, on the one hand, the present invention proposes a method for rapidly and dynamically separating the radial and angular polarization components of a light beam, including the following steps:

[0006] Adjust the incident light beam to an initial state with a radial or angular polarization distribution; introduce the adjusted light beam into a uniaxial crystal, and use the birefringence effect of the uniaxial crystal to make the radial polarization component and the angular polarization component propagate in different directions and be focused respectively; apply an electric field to the uniaxial crystal through an external electric field module, and adjust the direction and magnitude of the electric field according to actual needs to control the positions of the focal points of the radial polarization component and the angular polarization component; use a spatial filter at the output end to extract the required polarization component.

[0007] Preferably, adjusting the incident light beam to an initial state with a radial or angular polarization distribution includes: using a vortex circular Airy beam as a light source.

[0008] Preferably, the uniaxial crystal is a strontium barium niobate crystal;

[0009] At a wavelength of 632.8 nm, the ordinary light refractive index n o of the strontium barium niobate crystal is 2.3117, and the extraordinary light refractive index n e= 2.2987, and the non-zero electro-optic coefficients are: γ 13 = γ 23 = 67 pm / V, γ 33 = 1340 pm / V, γ 51 = γ 42 = 42 pm / V.

[0010] Preferably, the DC high-voltage power supply used in the external electric field module has an adjustable range of plus or minus 20,000 volts, and the direction of the external electric field is applied along the z-axis direction of the strontium barium niobate crystal.

[0011] Preferably, the dielectric constant tensor before the external electric field is:

[0012]

[0013] Preferably, the application along the z-axis direction of the strontium barium niobate crystal includes: after applying an electric field along the z direction, the dielectric constant tensor becomes:

[0014]

[0015] where E 0 is the applied electric field strength.

[0016] Preferably, the change in birefringence of the strontium barium niobate crystal is:

[0017]

[0018] Preferably, the incident light beam is a left-handed circularly polarized vortex Airy beam with a topological charge number of -1, and its optical field expression is:

[0019] where C is a constant, Ai is the Airy function, r 0 is the initial radius of the main lobe, w is the scaling factor, a is the attenuation factor, is the left-handed circular polarization unit vector.

[0020] Preferably, applying an electric field to the uniaxial crystal through the external electric field module and adjusting the direction and magnitude of the electric field according to actual needs to control the positions of the foci of the radial polarization component and the angular polarization component includes:

[0021] When the external electric field E 0 is equal to 0, the foci of the radial polarization component and the angular polarization component coincide, and the position is 0.0368 m;

[0022] When the external electric field E 0 is equal to 15 kV / mm, the focus of the radial polarization component is in front, and the position is 0.0346 m;

[0023] When the external electric field E0 When it is equal to 20 kV / mm, the focus of the radially polarized component moves to 0.0332 m.

[0024] On the other hand, the present invention proposes a device for rapidly and dynamically separating the radial and azimuthal polarization components of a light beam, comprising:

[0025] A light source module for generating a vortex circular Airy beam with self-focusing characteristics;

[0026] A uniaxial crystal module for separating the radial polarization component and the azimuthal polarization component, with the input and output surfaces coated with films and transparent electrodes;

[0027] An externally applied electric field module for providing an adjustable DC high-voltage power supply;

[0028] A spatial filter located at the output end for extracting the required polarization component.

[0029] Technical effects and advantages of the present invention: The method and device for rapidly and dynamically separating the radial and azimuthal polarization components of a light beam proposed by the present invention have the following advantages compared with the prior art:

[0030] By utilizing the birefringence characteristics of the SBN uniaxial crystal and combining with the externally applied electric field module to apply an adjustable electric field to the crystal, the present invention realizes efficient and dynamic separation of polarization components. This method can not only gradually separate the radial and azimuthal polarization components during propagation and focus them on different foci, but also flexibly control the positions of these foci by adjusting the direction and magnitude of the externally applied electric field, providing higher flexibility and precision. Therefore, the present invention significantly improves the flexibility and efficiency in the fields of optical manipulation, high-resolution imaging, optical communication, and quantum information processing, providing more efficient and accurate beam processing technical support for these applications. Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of the device for rapidly and dynamically separating the radial and azimuthal polarization components of the light beam of the present invention;

[0032] Figure 2 It is a schematic structural diagram of the direction of the externally applied electric field of the present invention;

[0033] Figure 3 It is a flowchart of the method for rapidly and dynamically separating the radial and azimuthal polarization components of the light beam of the present invention;

[0034] Figure 4 It is the external electric field E in the present invention 0 When it is equal to 0, it is a schematic diagram of the propagation and evolution behavior of the light beam;

[0035] Figure 5 It is the external electric field E in the present invention 0Schematic diagram of the propagation and evolution behavior of the light beam when it is equal to 15 kV / mm;

[0036] Figure 6 In the present invention, the external electric field E 0 Schematic diagram of the propagation and evolution behavior of the light beam when it is equal to 20 kV / mm. Specific implementation manners

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] In this embodiment, there is provided a Figure 1 and Figure 2 shown fast dynamic separation device for the radial and angular polarization components of a light beam, including: a light source module 1, a uniaxial crystal module 2, an external electric field module 3, and a spatial filter 4.

[0039] Among them, the light source module 1 is used to generate a light beam with self-focusing characteristics, such as a vortex circular Airy beam (VCAB), or a light beam focused after passing through a lens; the uniaxial crystal module 2 is used for coating the input and output surfaces and plating transparent electrodes; the external electric field module 3 is used to provide an adjustable DC high-voltage power supply; the spatial filter 4 is located at the output end for extracting the required polarization components.

[0040] The polarization components include an angular polarization component 7 and an angular polarization component focus 5, a radial polarization component 8 and a radial polarization component focus 6.

[0041] The above-mentioned uniaxial crystal module 2 selects a strontium barium niobate (SBN) crystal, which belongs to the tetragonal system (TetragonalSystem), and its space group is P4bm (point group 4mm), with high symmetry and anisotropy. When an external electric field is applied along the z-axis direction, the symmetry of the SBN crystal will not change. By changing the magnitude and direction of the external electric field, the dynamic separation of the positions of the two component foci can be achieved, providing a new regulation means for related optical applications.

[0042] For the uniaxial electro-optic strontium barium niobate (SBN) crystal, at a wavelength of 632.8 nm, the ordinary light refractive index no = 2.3117, the extraordinary light refractive index ne = 2.2987, and the non-zero electro-optic coefficients are respectively: γ 13 = γ 23 = 67 pm / V, γ 33 = 1340 pm / V, γ51 = γ 42 = 42 pm / V. The maximum electro-optic coefficient of SBN can be utilized when the external electric field is along the z-axis direction. The polarization intensity caused by the electro-optic effect is:

[0043] and For the uniaxial crystal SBN, the dielectric constant tensor before applying the electric field is:

[0044]

[0045] After applying the electric field along the z direction, the dielectric constant tensor is:

[0046]

[0047] That is to say, after applying the external electric field, the crystal remains a uniaxial crystal and the principal axis direction does not change.

[0048] Its birefringence becomes

[0049]

[0050] It can be seen that by changing the magnitude of the external electric field E 0 the birefringence can be adjusted.

[0051] Based on the above-mentioned device for rapidly and dynamically separating the radial and angular polarization components of a light beam, in this embodiment, there is also provided a Figure 3 method for rapidly and dynamically separating the radial and angular polarization components of a light beam as shown in the following steps:

[0052] Adjust the incident light beam to an initial state with a radial or angular polarization distribution; specifically, use a vortex circular Airy beam as the light source.

[0053] Import the adjusted light beam into the uniaxial crystal, and utilize the birefringence effect of the uniaxial crystal to make the radial polarization component and the angular polarization component propagate along different directions and be focused respectively;

[0054] Specifically, when the light beam after the initial state adjustment enters the uniaxial crystal, due to the birefringence effect of the uniaxial crystal, the radial polarization component 8 (i.e., the e-light) and the angular polarization component 7 (i.e., the o-light) will propagate along different directions. During the propagation process, these two components are focused respectively (the focus 5 of the angular polarization component and the focus 6 of the radial polarization component), thus forming separated foci. For details, reference can be made to Figure 1 .

[0055] Apply an electric field to the uniaxial crystal through an external electric field module, and adjust the direction and magnitude of the electric field according to actual requirements (see in detail Figure 2) to control the positions of the foci of the radial polarization component and the azimuthal polarization component; it is capable of quickly and accurately controlling the positions of the separated foci, and realizing the dynamic adjustment of the beam propagation characteristics. A spatial filter is used at the output end to extract the required polarization component. Specifically as follows:

[0056] The incident light is a left-handed circularly polarized vortex Airy beam with a topological charge number l of -1, and its optical field expression is:

[0057]

[0058] where C is a constant, Ai is the Airy function, r0 is the initial radius of the main lobe, w is the scaling factor, a is the attenuation factor, is the left-handed circular polarization unit vector. The following simulation values are: r0 = 0.25mm, w = 0.014mm, a = 0.01, and the wavelength is 632.8nm. The crystal is SBN, and the crystal length is 30mm.

[0059] 1) The case where the external electric field E 0 is equal to 0. The propagation and evolution behaviors of the beam in the crystal and in the air are as Figure 4 shown. From Figure 4 it can be seen that the foci of the radial polarization component and the azimuthal polarization component coincide, and the focus appears at 0.0368m.

[0060] 2) The case where the external electric field E 0 is equal to 15 kV / mm. The beam propagation and evolution are as Figure 5 shown. Figure 5 The propagation and evolution behaviors of the beam in the crystal and in the air, where E 0 = 15 kV / mm. The foci of the two components are separated. The focus of the radial polarization component is in front, at 0.0346m, and the focus of the azimuthal polarization component is behind, with the position unchanged, at 0.0368m.

[0061] 3) The case where the external electric field E 0 is equal to 20 kV / mm. The beam propagation and evolution are as Figure 6 shown. Figure 6 The propagation and evolution behaviors of the beam in the crystal and in the air, where E 0 = 20 kV / mm. The separation distance between the foci of the two components increases. The focus of the radial polarization component is in front, at 0.0332m, and the focus of the azimuthal polarization component is behind, with the position unchanged, at 0.0368m.

[0062] In summary, the present invention utilizes the birefringence characteristics of the SBN uniaxial crystal and combines an externally applied electric field module to apply an adjustable electric field to the crystal, achieving efficient and dynamic polarization component separation. This method can not only gradually separate the radial and azimuthal polarization components during propagation and focus them on different focal points, but also flexibly control the positions of these focal points by adjusting the direction and magnitude of the externally applied electric field, providing higher flexibility and precision.

[0063] Therefore, the present invention significantly improves the flexibility and efficiency in the fields of optical manipulation, high-resolution imaging, optical communication, and quantum information processing, providing more efficient and precise beam processing technical support for these applications.

[0064] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for rapid dynamic separation of radial and angular polarization components of a light beam, characterized in that: The following steps are involved: Adjusting the incident light beam to have an initial state of radial or angular polarization distribution; The adjusted light beam is introduced into a uniaxial crystal, and the radial polarization component and the angular polarization component are propagated in different directions and focused respectively by utilizing the birefringence effect of the uniaxial crystal; Applying an electric field to the uniaxial crystal through an external electric field module, and adjusting the direction and magnitude of the electric field according to actual needs to control the positions of the foci of the radial polarization component and the angular polarization component; A spatial filter is applied at the output to extract the desired polarization component.

2. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 1, characterized in that: The step of adjusting the incident light beam to an initial state having a radial or angular polarization distribution comprises: A vortex circular Airy beam was used as the light source.

3. The method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 1, characterized in that: The uniaxial crystal is a barium strontium niobate crystal; At a wavelength of 632.8 nm, the ordinary light refractive index n of the barium strontium niobate crystal is o =2.3117, extraordinary refractive index n e =2.2987, the non-zero electro-optic coefficients are: γ 13 =γ 23 =67pm / V,γ 33 =1340pm / V,γ 51 =γ 42 =42pm / V.

4. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 3, characterized in that: The DC high voltage power supply used by the external electric field module is adjustable within a range of plus or minus 20,000 volts, and the direction of the external electric field is applied along the z-axis direction of the barium strontium niobate crystal.

5. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 4, characterized in that: The dielectric constant tensor before the external electric field is:

6. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 5, characterized in that: The z-axis direction of the barium strontium niobate crystal is applied, including: after applying an electric field along the z-direction, the dielectric constant tensor becomes: where E0 is the applied electric field strength.

7. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 6, characterized in that: The birefringence of the barium strontium niobate crystal changes as follows:

8. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 7, characterized in that: The incident beam is a left-handed circularly polarized vortex circular Airy beam with a topological charge number of -1, and its light field expression is: Where C is a constant, Ai is the Airy function, r0 is the initial radius of the main lobe, w is the scaling factor, a is the attenuation factor, is the left-handed circularly polarized unit vector.

9. A method for rapid dynamic separation of radial and angular polarization components of a light beam according to claim 8, characterized in that: The method of applying an electric field to the uniaxial crystal through an external electric field module and adjusting the direction and magnitude of the electric field according to actual needs to control the positions of the foci of the radial polarization component and the angular polarization component includes: When the external electric field E0 is equal to 0, the foci of the radial polarization component and the angular polarization component coincide with each other at a position of 0.0368m; When the external electric field E0 is equal to 15kV / mm, the focus of the radial polarization component is in the front and the position is 0.0346m; When the external electric field E0 is equal to 20 kV / mm, the focus of the radial polarization component moves to 0.0332 m.

10. A fast dynamic separation device for radial and angular polarization components of a light beam for implementing the method according to any one of claims 1 to 9, characterized in that: include: A light source module, used for generating a vortex circular Airy beam with self-focusing characteristics; Uniaxial crystal module, used to separate radial polarization component and angular polarization component, with input and output surfaces coated with films and transparent electrodes; An external electric field module is used to provide an adjustable DC high voltage power supply; A spatial filter, located at the output, is used to extract the desired polarization component.

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