A method and system for generating optical skyrmions with adjustable topological texture

Abstract

The application discloses a kind of topological texture adjustable optical Sgminzi generation method and system.The method and system contain two core components of liquid crystal spatial light modulator and variable phase retarder, by adjusting the holographic phase of liquid crystal spatial light modulator and the control voltage of variable phase retarder, can be regulated as topological texture customizable Sgminzi light beam with a linear polarization base mode Gaussian light beam, realizes the topological texture adjustable generation of optical Sgminzi.The application can be widely applied in free space laser communication and other frontier application scenarios with high energy utilization rate, fast response speed, rich topological texture, simple system structure, stability, easy adjustment.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a method and system for generating optical skyrmions with tunable topological texture. Background Technology

[0002] Skyrmions are topologically protected quasiparticle structures, first proposed in 1962 by British physicist Heinrich Skyrmion during his research on the unified field theory of meson-baryon interactions. They have since been confirmed to exist in Bose-Einstein condensates, liquid crystal materials, ferromagnets, acoustics, and torsional electrons. Among these, magnetic skyrmions have demonstrated high stability, small size, and low driving energy, making them a promising candidate for future storage technologies and attracting widespread attention from the scientific and industrial communities.

[0003] In recent years, the concept of skyrmions has been introduced into the field of optics and has frequently appeared in various optical systems. These topological quasiparticles with skyrmion-like textured light field distributions are called optical skyrmions, and beams with cross-sectional topological textures of optical skyrmions are called skyrmion beams. Typical forms of optical skyrmions mainly include Néel-type, Bloch-type, inverse-type, and bihalf-type skyrmions of different orders. Early discovered optical skyrmions include Néel-type electric field vector skyrmion arrays in evanescent light fields and Bloch-type spin vector skyrmions under tight focusing conditions. Later, under paraxial conditions, optical skyrmions based on Stokes vector theory were proposed. These are the first type of optical skyrmions that can propagate in free space, and their tunability is relatively more free than in other optical fields. They can realize special textures such as Néel-type, Bloch-type, inverse-type, and bihalf-type skyrmions, making them excellent carriers of optical information. At the same time, due to their anti-turbulence capabilities brought about by their topological characteristics, they have shown great application potential in the field of free-space laser communication.

[0004] Currently, scholars both domestically and internationally have conducted some research on the generation of Stokes vector skyrmions, proposing methods such as liquid crystal spatial light modulators and holography to generate optical skyrmions with tunable topological textures, namely Néel-type, Bloch-type, and inverse skyrmions. However, these methods suffer from low energy efficiency and complex optical paths that are difficult to construct. Later, with the introduction of quasiparticles, the concepts of optical skyrmions and other topological quasiparticles have been continuously enriched, and the textures that the original modulation methods could generate began to show limitations. Researchers have designed more complex gradient-refractive-index lenses to draw skyrmion textures on the fiber end face, which has solved the problem of the limited modulatorable textures of the original modulation methods to some extent. However, this makes the optical path structure more complex, requiring high-precision splicing of a large number of components, making texture replacement difficult and unable to meet the channel capacity requirements of free-space laser communication. Therefore, there is an urgent need to develop an optical skyrmion generation method with low energy loss, simple optical path, and tunable topological textures that can be achieved rapidly. Summary of the Invention

[0005] In view of this, the present invention discloses a method and system for generating optical skyrmions with tunable topological texture.

[0006] The present invention provides a method for generating optical skyrmions with tunable topological texture. By loading a liquid crystal spatial light modulator to modulate the phase of a fundamental Gaussian beam, a specific and controllable phase modulation is introduced. In addition, a phase delay is introduced by adjusting a variable phase delayer. This method can control a fundamental Gaussian beam into a skyrmion beam with customizable topological texture, thereby realizing the tunable generation of optical skyrmions with tunable topological texture.

[0007] The holographic phase loaded onto the liquid crystal spatial light modulator is a spiral phase, and its pure phase modulation function is:

[0008]

[0009] Where -s is the spiral phase order, used to control the order of generating optical skyrmions, i.e., the skyrm number s; Angular coordinates; This is the initial phase, used to control the conversion of optical skyrmions between the Néel and Bloch types.

[0010] A variable phase retarder can introduce an adjustable optical path difference of 0 to λ between the fast and slow axes, controlling the conversion of optical skyrmions between positive (Néel or Bloch) type, inverse type, and bihalfon.

[0011] The present invention provides an optical skyrmion generation system with tunable topological texture, comprising a laser, a polarizer, a liquid crystal spatial light modulator, and a variable phase delayer, wherein:

[0012] The laser is used to generate a fundamental Gaussian beam;

[0013] The polarizer is placed in the laser path behind the laser, with its polarization direction at 45° to the horizontal plane, and is used to generate a 45° inclined linearly polarized fundamental mode Gaussian beam.

[0014] The liquid crystal spatial light modulator is placed in the laser optical path behind the polarizer. It is loaded with a spiral phase. When a Gaussian beam with a 45° oblique linear polarization fundamental mode is incident on the liquid crystal spatial light modulator, it can be decomposed into a horizontal linear polarization component and a vertical linear polarization component with equal intensity. The horizontal linear polarization component will be modulated by the spiral phase, while the vertical linear polarization component remains unchanged and still maintains the fundamental Gaussian mode. At this time, the transverse topological texture of the output beam of the liquid crystal spatial light modulator is the optical bihalf.

[0015] The variable phase delayer is placed in the laser optical path behind the liquid crystal spatial light modulator, with the fast axis tilted at 45°. With the addition of a control voltage, the optical bihalf-particles output from the liquid crystal spatial light modulator can be modulated into positive / negative bihalf-particles, skyrmions, or other topological quasiparticles.

[0016] The present invention has the following beneficial effects:

[0017] (1) The present invention provides a topologically adjustable optical skyrmion generation method based on pure phase modulation, which has high energy utilization and fast response speed.

[0018] (2) The optical skyrmion generation method with adjustable topological texture of the present invention can generate a variety of optical skyrmions and other topological quasi-particles as needed, and has broad prospects in the field of optical communication.

[0019] (3) The optical skyrmion generation system with adjustable topological texture of the present invention has a simple, stable and easy-to-adjust system structure, and can be applied to a variety of cutting-edge application scenarios. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an optical skyrmion generation system with tunable topological texture according to the present invention, wherein 1-laser, 2-polarizer, 3-liquid crystal spatial light modulator, and 4-variable phase delayer.

[0021] Figure 2 In Embodiment 1 of the present invention, the spiral phase loaded on the liquid crystal spatial light modulator The diagram shows that s = 1 at this point.

[0022] Figure 3The simulation and experimental results of the optical skyrmion generation system with tunable topological texture of the present invention in generating a first-order Néel-type skyrmion are shown in Example 1. The left side is the Stokes vector distribution diagram of the outgoing beam obtained by simulation calculation, and the right side is the Stokes vector distribution diagram of the outgoing beam obtained by experiment.

[0023] Figure 4 In Embodiment 2 of the present invention, the spiral phase loaded on the liquid crystal spatial light modulator The diagram shows that s = 5 at this point.

[0024] Figure 5 The simulation and experimental results of the optical skyrmion generation system with tunable topological texture of the present invention in generating 5th-order bihalfons are shown in Example 2. The left side is the Stokes vector distribution diagram of the outgoing beam obtained by simulation calculation, and the right side is the Stokes vector distribution diagram of the outgoing beam obtained by experiment. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] First, we will briefly introduce the principle of the optical skyrmion generation method with tunable topological texture of the present invention.

[0027] In a general sense, the Stokes vector skyrmion can generally be regarded as the superposition of beams with orthogonal spatial modes and polarization states, and its expression is:

[0028]

[0029] Where u1(r) and u2(r) are two orthogonal spatial intensity distributions, and here the initial phase... Representing the phase difference between two modes, |p1> and |p2> are two mutually orthogonal polarization states, typically left-handed and right-handed circularly polarized light, but also horizontally and vertically polarized light. For optical skyrmions, they can be decomposed on the left / right-handed circularly polarized orthogonal basis {|L>,|R>}, one of which is the fundamental mode Gaussian beam |LG0>, and the other is the single-mode vortex beam |LG0>. -s The resulting s-order optical skyrmion is:

[0030]

[0031] in, For a -s-order single-mode vortex beam, by selecting parameters s and The values ​​can be used to give the three common forms of optical skyrmions: Néel type: s = 1, Bloch type: s=1, Inversion: s=-1, In this invention, parameters s and Spiral phase that can be loaded onto a liquid crystal spatial light modulator To regulate:

[0032]

[0033] Therefore, by adjusting the parameters s and s of the pure phase modulation function on the liquid crystal spatial light modulator... The order and form of optical skyrmions can be controlled.

[0034] Based on this, if the orthogonal polarization basis of left / right circularly polarized light in an optical skyrmion is transformed into other orthogonal polarization bases, an optical skyrmion with unchanged skyming number but significantly altered texture can be obtained. This transformation of the orthogonal polarization basis can be achieved using a variable phase retarder. For a waveplate with a phase retardation angle δ and an angle θ between the fast axis and the x-axis, the expression for the Jones matrix in Cartesian coordinates is as follows:

[0035]

[0036] When θ = ±45°, the Jones matrix can be simplified to:

[0037]

[0038] Considering that the input light of the variable phase delayer is a superposition of horizontally and vertically linearly polarized light, calculate the output light of the corresponding components:

[0039]

[0040] It can be observed that the first and second terms have orthogonal bases and both have a modulus of 1, forming a new pair of unit orthogonal bases. It can be deduced that the output light through the variable phase retarder satisfies the requirements of a generalized skyrmion. When the phase delay angle δ = kπ (k = 0, 1, 2…), the base is a horizontal / vertical linear polarization base, and the output beam is a bihalf-wave. When δ = kπ + π / 2 (k = 0, 1, 2…), the base is left-handed / right-handed circularly polarized light, and the output is a standard optical skyrmion. When δ has other values, other optical skyrmions can be output. This process can cover all unit polarization orthogonal bases, enriching the polarization texture of optical skyrmions and greatly increasing the types and range of optical skyrmions we can control.

[0041] The present invention provides an optical skyrmion generation system with tunable topological texture, such as... Figure 1As shown, the device comprises a laser, a polarizer, a liquid crystal spatial light modulator, and a variable phase retarder. The laser generates a fundamental Gaussian beam. The polarizer, positioned in the laser path behind the laser, is polarized at a 45° angle to the horizontal plane to generate a 45° linearly polarized fundamental Gaussian beam. The liquid crystal spatial light modulator, also positioned in the laser path behind the polarizer, is loaded with a spiral phase. When the 45° linearly polarized fundamental Gaussian beam is incident on the liquid crystal spatial light modulator, it can be decomposed into a horizontally polarized component and a vertically polarized component with equal intensity. The horizontally polarized component is modulated by the spiral phase, while the vertically polarized component remains unchanged, maintaining the fundamental Gaussian mode. The transverse topological texture of the output beam from the liquid crystal spatial light modulator at this time is the optical bihalf. The variable phase retarder, positioned in the laser path behind the liquid crystal spatial light modulator with its fast axis at a 45° angle, and with an applied control voltage, can modulate the optical bihalf output from the liquid crystal spatial light modulator into positive / negative bihalf, skyrmions, or other topological quasiparticles.

[0042] The following, in conjunction with embodiments, briefly introduces the modulation performance of a topologically tunable optical skyrmion generation method and system of the present invention.

[0043] Example 1: Generation of first-order Néel-type skyrmions

[0044] In this embodiment, the laser wavelength λ = 1617 nm, and the modulation phase loaded on the liquid crystal spatial light modulator is as follows: Figure 2 As shown, where s = 1, The variable phase retarder adjusts the control voltage to make the additional optical path difference λ / 4, i.e., the phase delay angle δ = π / 2. The fundamental mode Gaussian beam can be passed through this system to obtain a first-order Néel-type Skyrmion beam, i.e., a first-order Néel-type optical Skyrmion. Figure 3 As can be seen from the numerical simulation and experimentally measured topological texture of optical skyrmions in this embodiment, the experimental results are in complete agreement with the numerical simulation results.

[0045] Example 2: Generating a 5th-order bihalf-substance

[0046] In this embodiment, the laser wavelength λ = 1617 nm, and the modulation phase loaded on the liquid crystal spatial light modulator is as follows: Figure 4 As shown, where s = 5, The variable phase retarder adjusts the control voltage to achieve an additional optical path difference of λ, i.e., a phase delay angle δ = 2π. A fundamental Gaussian beam passing through this system yields a 5th-order bihalf-beam, i.e., a 5th-order bihalf-beam. Figure 5 As can be seen from the numerical simulation and experimentally measured topological texture of optical skyrmions in this embodiment, the experimental results are in complete agreement with the numerical simulation results.

[0047] The above embodiments demonstrate that the optical skyrmion generation method and system with tunable topological texture of the present invention has good performance.

[0048] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for generating optical skyrmions with adjustable topological texture, comprising the following steps: (1) loading a modulation phase by a liquid crystal spatial light modulator; (2) introducing a phase delay by adjusting a variable phase retarder, wherein when the phase delay angle of the variable phase retarder is kπ (k=0, 1, 2……), a double half skyrmion is outputted; when the phase delay angle of the variable phase retarder is (kπ+π / 2) (k=0, 1, 2……), a standard optical skyrmion is outputted; and when the phase delay angle of the variable phase retarder is other values, other optical skyrmions are outputted. The above method can be used to control a Gaussian beam into a skyrmion beam with adjustable topological texture, thereby realizing the generation of optical skyrmions with adjustable topological texture. introducing specific and controllable phase modulation for the base mode Gaussian beam, wherein -s is the spiral phase order, which is used to control the order of the generated optical skyrmion, i.e. the skyrmion number s; is an angular coordinate; is an initial phase, which is used to control the conversion of the optical skyrmion between the Néel type and the Bloch type; The method comprises a laser, a polarizer, a liquid crystal spatial light modulator, and a variable phase retarder. The laser is used to generate a Gaussian beam.

2. A topologically textured optical soliton generation system, comprising: The polarizer is disposed in the laser light path behind the laser, and the polarization direction is 45° to the horizontal plane, which is used to generate a 45° linearly polarized Gaussian beam. The liquid crystal spatial light modulator is disposed in the laser light path behind the polarizer, and the liquid crystal spatial light modulator loads a spiral phase, which can decompose the 45° linearly polarized Gaussian beam into a horizontal linearly polarized component and a vertical linearly polarized component, wherein the horizontal linearly polarized component is modulated by the spiral phase, and the vertical linearly polarized component remains unchanged and maintains the Gaussian mode, and the transverse topological texture of the output beam of the liquid crystal spatial light modulator is an optical double half skyrmion. The variable phase retarder is disposed in the laser light path behind the liquid crystal spatial light modulator, and the fast axis is placed at 45°, and the variable phase retarder is attached with a control voltage, which can control the output optical double half skyrmion behind the liquid crystal spatial light modulator into a positive / negative double half skyrmion, a skyrmion, or other topological quasi-particles. ​ ​

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