Vortex light phase singular point decomposition device

Abstract

The utility model relates to a vortex light phase singular point decomposition device, which comprises a laser module, the laser module emits laser with resonance wavelength with an alkali metal atom D1 line, and the laser sequentially passes through an isolator, a lens A, a lens B, a reflecting mirror and a polaroid A and enters an alkali metal atom medium after being reflected by a polarization splitting prism A; the laser is emitted from the alkali metal atom medium and then is reflected by a polarization splitting prism B to enter a light collector B; incident vortex light is processed by the window sheet A, the diaphragm A, the diaphragm B, the ground glass sheet, the polaroid B and the lens C, then transmitted and enters the alkali metal atom medium through the polarization splitting prism A. The incident vortex light is emitted from the alkali metal atom medium, then transmitted and passes through the polarization splitting prism B, and is processed by the lens D and the window sheet B, and then emergent vortex light subjected to phase singular point decomposition is output. According to the method, the decomposition of the phase singular point with the larger topological charge to the phase singular point with the topological charge of + / -1 is realized, and the method has potential application value in the quantum communication technology based on the atomic medium.

Description

Technical fields:

[0001] This invention relates to the field of light-atom interaction technology in quantum optics, specifically to a device for decomposing vortex phase singularities. Background technology:

[0002] Vortex light is a laser mode with a ring-shaped intensity distribution and a spiral phase structure, its most typical feature being a phase singularity located at the center. The ratio of the change in phase of a vortex light as it rotates around the phase singularity to 2π is called the topological charge. A vortex light with a topological charge of l carries a certain amount of energy per photon. orbital angular momentum ( (This refers to Planck's constant). These unique properties of vortex light have led to its widespread application in super-resolution imaging, optical trapping, laser processing, optical tweezers, precision measurement, and quantum information processing. In particular, vortex light modes with different topological charges form a set of orthogonal complete bases, which can be used to encode information in optical communication. Theoretically, the topological charge of vortex light can take any integer value, forming an infinite-dimensional Hilbert space. Through orbital angular momentum multiplexing, the channel capacity of optical communication can be greatly improved. In vortex light-based optical communication, one of the key technologies is the decomposition of orbital angular momentum or phase singularities during the information decoding process.

[0003] Currently, the vortex phase singularity decomposition technique mainly utilizes: (1) a fork grating or a q-wave plate; (2) a spatial light modulator; and (3) a Mach-Zehnder interferometer. In the first scheme, the fork grating or q-wave plate removes the phase singularity with a topological charge of l from a beam of light by superimposing phase singularities with a topological charge of -l. By using multiple fork gratings or q-wave plates of different orders combined with single-mode fiber to project and measure the phase singularities with different topological charges, the phase singularity components with different topological charges in a beam of light can be effectively decomposed. In the second scheme, the spatial light modulator is used to realize the transformation from rectangular coordinates to logarithmic polar coordinates, which can transform the spiral wavefronts of phase singularities with different topological charges into plane wavefronts with different inclinations, and then the phase singularities can be decomposed by passing through a lens. In the third scheme, Dowell prisms with different angles are placed in a cascaded Mach-Zehnder interferometer, and the parity of the topological charge of the phase singularity can be used to achieve the decomposition of the phase singularity at the single-photon level. These technical solutions provide a feasible approach to achieving orbital angular momentum multiplexing in vortex-based optical communication. However, existing solutions can only decompose phase singularities of different topological charges, and cannot decompose phase singularities of larger topological charges into multiple phase singularities of smaller topological charges. With the increasing adoption of vortex light in optical communication and the continuous growth in demand for higher optical communication rates, there is an urgent need to further explore new technologies using vortex light to improve channel capacity.

[0004] It should be noted that the above content falls within the inventor's technical knowledge and does not necessarily constitute prior art. Utility Model Content:

[0005] The purpose of this invention is to solve the problems existing in the prior art and provide a vortex optical phase singularity decomposition device. It overturns the existing ideas of vortex optical phase singularity decomposition and presents a vortex optical phase singularity decomposition technology based on alkali metal atomic medium and electromagnetic induction transparency effect. It realizes the decomposition of phase singularities with large topological charges to phase singularities with topological charges of ±1, and provides a new way to further improve the channel capacity of optical communication based on vortex light.

[0006] A vortex optical phase singularity decomposition device, comprising:

[0007] The laser module emits a laser with a wavelength resonant to the D1 line of alkali metal atoms. The laser passes sequentially through an isolator, lens A, lens B, a reflector, polarizer A, and is reflected by polarizing beam splitter A before entering the alkali metal atom medium. After passing through the alkali metal atom medium, the laser is reflected again by polarizing beam splitter B and enters the light collector B.

[0008] After being processed by window A, aperture A, aperture B, ground glass, polarizer B, and lens C, the incident vortex light is transmitted through polarizing beam splitter A and enters the alkali metal atomic medium. After exiting the alkali metal atomic medium, the incident vortex light is transmitted through polarizing beam splitter B and processed by lens D and window B to output the outgoing vortex light with phase singularity decomposition.

[0009] The alkali metal atom medium is composed of alkali metal vapor enclosed in a cylindrical glass container, and the two end faces of the glass container are coated with an antireflection film covering the resonant wavelength of the D1 line of alkali metal atoms.

[0010] The alkali metal atom medium is placed in a heating furnace, which is connected to a temperature control module.

[0011] The alkali metal is cesium, lithium, sodium, potassium, or rubidium.

[0012] The alkali metal is cesium, the corresponding alkali metal atom is cesium atom, the alkali metal atom medium is cesium atom medium, and the laser module emits laser light corresponding to the D1 line resonance wavelength of 894.6 nm of cesium atoms.

[0013] A light collector A is located below the polarizing beam splitter A.

[0014] The present invention, by employing the above method, can bring the following beneficial effects:

[0015] This application presents a vortex-based optical phase singularity decomposition device designed based on alkali metal atomic media and electromagnetic induction transparency effect. This device decomposes phase singularities with large topological charges into phase singularities with topological charges of ±1, providing a new approach to further improve the channel capacity of vortex-based optical communication. Furthermore, this technical solution is based on the coherent interaction between light and atoms, and has potential application value in quantum communication technology based on atomic media. Attached image description:

[0016] Figure 1 This is a schematic diagram of the structure of the vortex optical phase singularity decomposition device of this utility model;

[0017] Figure 2 This utility model contains cesium atoms ( 133 Schematic diagram of the Cs)D1 line energy level;

[0018] Figure 3 This is a schematic diagram of the phase distribution of the incident and outgoing vortex beams of this invention.

[0019] Figure 4 The graph shows the variation of Λ with atomic number density for several common alkali metal atomic media.

[0020] Among them, 1. Laser module, 2. Isolator, 3. Lens A, 4. Lens B, 5. Reflector, 6. Polarizer A, 7. Polarizing beam splitter A, 8. Light collector A, 9. Alkali metal atomic medium, 10. Heating furnace, 11. Temperature control module, 12. Polarizing beam splitter B, 13. Light collector B, 14. Incident vortex light, 15. Window A, 16. Aperture A, 17. Aperture B, 18. Ground glass plate, 19. Polarizer B, 20. Lens C, 21. Lens D, 22. Window B, 23. Outgoing vortex light. Detailed implementation method:

[0021] To more clearly illustrate the overall concept of this utility model, a detailed description will be provided below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0023] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0024] like Figure 1-4 As shown, a vortex optical phase singularity decomposition device includes:

[0025] Laser module 1 emits a laser beam (which can be defined as the control light) with a wavelength resonant with the D1 line of alkali metal atoms. The laser beam passes sequentially through isolator 2, lens A3, lens B4, mirror 5, polarizer A6, and is reflected by polarizing beam splitter A7 before entering the alkali metal atom medium 9 (taking cesium atom medium as an example). The isolator 2 is used to prevent laser beams reflected from other optical elements from entering the laser module (1) in reverse and affecting the stable operation of the laser. The control light is expanded into a parallel beam with a spot radius of about 1 mm by lens A3 and lens B4. Polarizer A6 is used to prepare the control light into vertical linear polarization, so that the control light can enter the cesium atom medium 9 after being reflected by polarizing beam splitter A7. The laser beam passes through the alkali metal atom medium and is then reflected by polarizing beam splitter B before entering the light collector B. The control light resonates with the D1 line of cesium atoms. 1 / 2 (F=4)→6P 1 / 2 (F′=3) Hyperfine transition resonant coupling, such as Figure 2 As shown, light is controlled to modulate the refractive index of a cesium atomic medium in space.

[0026] The incident vortex light 14 (defined as the signal light, having a phase singularity with a topological charge of l) is processed by window A15, aperture A16, aperture B17, ground glass plate 18, polarizer B19, and lens C20, and then transmitted through polarizing beam splitter A7 into alkali metal atom medium 9 (taking cesium atom medium as an example). Ground glass plate 18 prepares the signal light into partially coherent vortex light, and polarizer B19 further prepares the signal light into horizontally linearly polarized light, so that the signal light can be transmitted through polarizing beam splitter A7 and enter the cesium atom medium. Lens C20 is used to focus the waist spot of the signal light onto the front surface of the cesium atom medium. The incident vortex light 14 exits from the alkali metal atom medium 9, is transmitted through polarizing beam splitter B12, and after being processed by lens D21 and window B22, outputs as the phase singularity-decomposed outgoing vortex light 23. The signal light acts on the cesium atom D1 line 6S. 1 / 2 (F=3)→6P 1 / 2 (F′=3) Hyperfine transition, such as Figure 2 As shown. Since the polarization directions of the signal light and the control light are perpendicular to each other, the signal light, after exiting the cesium atomic medium, will be transmitted through the polarizing beam splitter B12, thus separating from the control light reflected on the polarizing beam splitter B12. Lens D21 is used to restore the signal light focused by lens C20 into a parallel beam, which is then output through window B22. The output vortex light 23 is the vortex light after phase singularity decomposition.

[0027] The alkali metal atom medium 9 is composed of alkali metal vapor enclosed in a cylindrical glass container. The two end faces of the glass container are coated with an antireflection film covering the resonant wavelength of the D1 line of the alkali metal atoms. This prevents laser reflection from the two end faces of the glass container and between the two surfaces of the glass.

[0028] The alkali metal atomic medium 9 is placed in a heating furnace 10, which is connected to a temperature control module 11. The temperature control module 11 controls the temperature of the heating furnace 10, and thus controls the temperature of the alkali metal atomic medium 9. Since the atomic number density in the alkali metal atomic medium 9 depends on temperature, the atomic number density of the alkali metal atomic medium 9 can be controlled by this device.

[0029] The alkali metal is cesium, lithium, sodium, potassium, or rubidium, and may also include stable isotopes.

[0030] The alkali metal is cesium, the corresponding alkali metal atom is cesium atom, the alkali metal atom medium 9 is cesium atom medium, and the laser module 1 emits laser light corresponding to the D1 line resonance wavelength of 894.6 nm of cesium atoms.

[0031] A light collector A8 is located below the polarizing beam splitter A7. The light collector A8 is used to collect excess laser light and prevent scattered light from interfering with the optical path.

[0032] The principle of the vortex light phase singularity decomposition device proposed in this application is as follows: An alkali metal atomic medium can be prepared into a graded refractive index medium using the electromagnetically induced transparency effect. When vortex light propagates in the electromagnetically induced transparent alkali metal atomic medium, periodic phase singularity decomposition and recombination occur. When the length of the alkali metal atomic medium is an odd multiple of one-quarter of the period, the phase singularity with topological charge l will decompose into |l| phase singularities with topological charge 1 and |l| phase singularities with topological charge -1 along a straight line.

[0033] The specific principles are further explained below:

[0034] When the signal light enters the cesium atom medium, its cross-spectral density function can be expressed as:

[0035]

[0036] In the formula, w is the waist radius, σ is the coherence length, and (x1, y1) and (x2, y2) are the coordinates within the cross-section of the signal light. The signal light and control light act on the 6S D1 line of cesium atoms, respectively. 1 / 2 (F=3)→6P 1 / 2 (F'=3) and 6S 1 / 2 (F=4)→6P 1 / 2(F'=3) Hyperfine transitions form a Λ-type three-level optical-atomic coupling system, leading to electromagnetically induced transparency, such as Figure 2 As shown. Under the first-order approximation, the propagation process of the signal light in the cesium atom medium can be described by the generalized Huygens-Fresnel integral:

[0037]

[0038]

[0039] In the formula, k is the wavenumber of the signal light in the cesium atomic medium, A = cos(βz), B = sin(βz) / β, D = cos(βz), and

[0040]

[0041] Here, χ is the polarizability experienced by the signal light as it propagates in the cesium atom medium, which can be expressed as:

[0042]

[0043] In the formula, r 2 =x 2 +y 2 N is the atomic number density, d is the cesium atom D1 line dipole matrix element, and ε0 is the vacuum permittivity. Δ is Planck's constant, Δ is the frequency detuning of the signal light, and γ is the 6S hyperfine level of the cesium atom. 1 / 2 (F=3) and 6S 1 / 2 The dephase rate between (F=4), Γ is the fine energy level 6S of the cesium atom. 1 / 2 and 6P 1 / 2 The spontaneous emission rate between them, Ω c It controls the Rabi frequency of light, w c This controls the radius of the light spot. The spectral correlation of the signal light is:

[0044]

[0045] Therefore, the phase distribution of the signal light can be obtained as follows: Where (x) r ,y r () is the phase reference point. The phase distribution of the signal light when it enters the cesium atomic medium is as follows: The phase distribution upon exiting the cesium atomic medium is as follows: Where L is the length of the cesium atomic medium. Numerical calculations show that when signal light propagates in the cesium atomic medium, periodic phase singularity decomposition and recombination occur, with a period of Λ = 2π / Re(β). A phase singularity with topological charge l decomposes into |l| phase singularities with topological charge 1 and |l| phase singularities with topological charge -1. When the length of the cesium atomic medium is an odd multiple of Λ / 4, the decomposed phase singularities are distributed along a straight line, as shown below. Figure 3 As shown in the figure (the first row is the phase distribution of the incident vortex light, and the second row is the phase distribution of the outgoing vortex light). Figure 4 Table 1 lists several common alkali metal atomic media ( 133 Cs、 85 Rb、 87 Rb and 23 The Λ values ​​of Na under different atomic number densities.

[0046] When implementing this technical solution, a cesium atom medium can be used, and the following parameters can be referenced: atomic number density 5×10⁻⁶. 17 m -3 The atomic medium length is 10.1 mm, the control light Rabi frequency is 10 MHz, the control light spot radius is 1 mm, the control light frequency detuning is 0 MHz, the signal beam waist radius is 10 μm, and the signal light frequency detuning is -10 MHz.

[0047] Table 1. Λ values ​​of several common alkali metal atomic media at different atomic number densities.

[0048]

[0049] The above-described specific embodiments should not be construed as limiting the scope of protection of this utility model. For those skilled in the art, any alternative improvements or modifications made to the embodiments of this utility model shall fall within the scope of protection of this utility model.

[0050] Any aspects of this utility model not described in detail are known to those skilled in the art.

Claims

1. A device for resolving vortex optical phase singularities, characterized in that, include: The laser module emits a laser corresponding to the D1 line resonance wavelength of alkali metal atoms. The laser passes sequentially through an isolator, lens A, lens B, a reflector, polarizer A, and is reflected by polarizing beam splitter A before entering the alkali metal atom medium. After passing through the alkali metal atom medium, the laser is reflected again by polarizing beam splitter B and enters the light collector B. After being processed by window A, aperture A, aperture B, ground glass, polarizer B, and lens C, the incident vortex light is transmitted through polarizing beam splitter A and enters the alkali metal atomic medium. After exiting the alkali metal atomic medium, the incident vortex light is transmitted through polarizing beam splitter B and processed by lens D and window B to output the outgoing vortex light with phase singularity decomposition.

2. The vortex optical phase singularity decomposition device according to claim 1, characterized in that, The alkali metal atom medium is composed of alkali metal vapor enclosed in a cylindrical glass container, and the two end faces of the glass container are coated with an antireflection film covering the resonant wavelength of the D1 line of alkali metal atoms.

3. The vortex optical phase singularity decomposition device according to claim 2, characterized in that, The alkali metal atom medium is placed in a heating furnace, which is connected to a temperature control module.

4. A vortex optical phase singularity decomposition device according to claim 1 or 3, characterized in that, The alkali metal is cesium, lithium, sodium, potassium, or rubidium.

5. The vortex optical phase singularity decomposition device according to claim 4, characterized in that, The alkali metal is cesium, the corresponding alkali metal atom is cesium atom, the alkali metal atom medium is cesium atom medium, and the laser module emits laser light corresponding to the D1 line resonance wavelength of 894.6 nm of cesium atoms.

6. A vortex optical phase singularity decomposition device according to claim 1 or 5, characterized in that, A light collector A is located below the polarizing beam splitter A.

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