A system with adjustable phase rotation angle between modes of vector optical field along with distance

Abstract

The present invention discloses a system for adjusting the phase rotation angle between modes of a vector optical field with distance, which includes a Gaussian light source, a beam expander, a diagonal linearly polarized light generator, a generating system for vector beams with arbitrary structures, and a detection device. A digital micromirror device (DMD) is provided in the vector beam generating system, which can realize flexible regulation of the phase rotation angle between modes of the vector optical field with distance during transmission only through topological charge modulation without using any specially processed optical elements. These results have potential application prospects in related fields such as micro-particle manipulation and quantum optics. The device has the characteristics of flexible regulation, low cost, fast refresh speed, wide application range, and easy integration.

Description

Technical Field

[0001] The present invention relates to the field of optics, and particularly to a system for adjusting the inter-mode phase rotation angle of a vector light field with distance. Background Art

[0002] As is well known, lasers have many physical properties and thus play an important role in information transmission. Currently, they have been widely applied in fields such as medicine, industry, and optical communication. For example, amplitude affects the intensity of observing an object; frequency affects the observation of color; and phase distribution affects the form of the interaction between light and matter. Nowadays, in the field of photonics, there are a vast number of reports on optical vortices and photon orbital angular momentum. Especially since 1992 when Allen et al. revealed the concept that Laguerre-Gaussian beams can carry orbital angular momentum, various new types of spatial light fields carrying orbital angular momentum have gradually come into people's sight. In particular, a two-dimensional vector light field formed by coupling the two degrees of freedom of the vortex structure and polarization state of photons in an inseparable manner has more novel and unique vector manipulation characteristics in multiple dimensions, which has aroused extensive interest in the vector control of light fields.

[0003] Currently, the research on vector light fields mainly focuses on the regulation of the transverse and longitudinal vector characteristics of the light field: among them, the transverse regulation of the light field includes the transverse distribution regulation of information such as light field intensity, polarization state, and phase; the longitudinal regulation of vector light fields is mostly limited to the research on the novel properties demonstrated by the polarization characteristics of vector light fields under specific conditions. For example, under the condition of tight focusing, the vector light field with a radial polarization distribution has a super-strong tight focusing force, which has great application potential in fields such as material microfabrication. The diverse phase distributions of vector light fields can provide diverse interaction modes between light and matter. Especially under free transmission conditions, flexibly regulating the phase transmission characteristics of the light field is of great significance to the field of micro-particle manipulation. However, so far, flexibly manipulating the phase information during the free transmission of the light field is still an urgent problem to be solved. Summary of the Invention

[0004] To overcome the above-mentioned defects in the prior art, the present invention provides a system for adjusting the inter-mode phase rotation angle of a vector light field with distance, which can realize the adjustable phase rotation angle of the light field by using the topological charge regulation of the circular Airy vortex vector light field.

[0005] Technical Solution

[0006] A system for adjusting the inter-mode phase rotation angle of a vector light field with distance includes a Gaussian light source, a beam expander, a diagonal linearly polarized light generator, a generating system for an arbitrary structure vector beam, and a detection device arranged in sequence from left to right. A digital micromirror device DMD for digitally regulating the light field parameters is provided in the generating system.

[0007] Further, the beam expander includes a first lens with a focal length of 20 mm and a second lens with a focal length of 200 mm, and the beam expander can collimate the beam and expand its size by ten times.

[0008] Further, the diagonal linearly polarized light generator includes a half-wave plate for adjusting the polarization state of the output beam to 45 degrees diagonally.

[0009] Further, the generating system includes a Wollaston prism.

[0010] Further, the generating system further includes a quarter-wave plate, and the generating system further includes a third lens with a focal length of 150 mm and a fourth lens with a focal length of 150 mm.

[0011] Further, the generating system further includes the digital micromirror device DMD, and the hologram loaded on the digital micromirror device DMD includes a digital grating. By adjusting the grating coefficient, two circularly polarized light beams with left and right handedness can be made to propagate along the same transmission path.

[0012] Further, the circular Airy vortex vector beam generated by the generating system is expressed as:

[0013]

[0014] where cosθ, is the weight factor, (r,φ) are the cylindrical coordinate parameters, and are the left and right handed circular polarization basis vectors. Additionally, is the phase difference between the two polarization basis vectors, and serve as two orthogonal spatial mode basis vectors, which are respectively circular Airy vortex beams carrying orbital angular momentum, is the Planck constant.

[0015] Further, the circular Airy vortex beam can be expressed as:

[0016]

[0017] where Ai() represents the Airy function; r is the radius, r0 is the main ring radius of the beam; a is the cut-off factor; ω is the beam waist radius; m is the topological charge; v is the initial emission angle parameter.

[0018] Further, the topological charge parameter of the circular Airy vortex vector beam is regulated by the digital micromirror device DMD, thereby manipulating the rotation angle of the phase between the beam modes as the beam propagates.

[0019] Further, the detection device includes a polarizer with an adjustable rotation angle.

[0020] Furthermore, the detection device further includes a CCD receiving device.

[0021] Furthermore, the generated light beam is passed through the analyzer 8 with angles adjusted to 0°, 45°, 90°, and 135° respectively, and then the CCD receiving device 9 is used to record the light intensities Ih, Id, Iv, and Ia of the four light beams under different conditions.

[0022] Furthermore, through the obtained four light intensities Ih, Id, Iv, and Ia, the Stokes parameters S1 and S2 can be obtained. The specific relationship is as follows:

[0023] S1 = Ih h - Id v , S2 = Iv d - Ia a

[0024] Furthermore, through the Stokes parameters S1 and S2, the inter-mode phase distribution of the generated vector light beam can be obtained. The specific relationship is as follows:

[0025] φ = arctan(S2 / S1)

[0026] Furthermore, by observing the inter-mode phase of the light beam, as the transmission distance of the light beam increases, the inter-mode phase rotates, and the rotation angle is related to the topological charge parameter of the light beam. The specific relationship is as follows:

[0027]

[0028] Furthermore, without changing the optical path, the circular Airy vortex vector light beam can realize the regulation of the inter-mode phase angle of the vector light field with distance based on topological charge modulation only by changing the topological charge parameter in the circular Airy vortex vector light beam loaded on the digital micromirror device DMD.

[0029] Advantageous Effects

[0030] Compared with the prior art, the present invention has the following advantageous effects:

[0031] There is no need to process materials with special structures, and it has the characteristics of wide application range, high flexibility, and simple digital control. In addition, the structure of the present invention is simple and the cost is low. Without the need for any optical components, the computer can control the DMD to change the parameters of the target vector light beam, thereby flexibly controlling the rotation angle of the inter-mode phase of the light field. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of a system for adjusting the rotation angle of the inter-mode phase of a vector light field with distance according to the present invention;

[0033] Figure 2 Schematic diagrams of the rotation of the inter-mode phase of circular Airy vortex vector beams with topological charges {m1, m2} being {1, -1}, {1, 0}, and {1, -2} respectively, corresponding to Figs. (a), (b), and (c).

[0034] Reference numerals

[0035] Gaussian light source A, beam expander B, diagonal linearly polarized light generator C, generation system D, detection device E, first lens 1, second lens 2, Wollaston prism 3, quarter-wave plate 4, third lens 5, fourth lens 6, digital micromirror device DMD7, analyzer 8, CCD receiving device 9 Detailed implementation mode

[0036] To better illustrate and elaborate on the content of the present invention, the following will be described in conjunction with the drawings and implementation examples:

[0037] There is Figure 1 - Figure 2 As shown, a system for adjusting the rotation angle of the inter-mode phase of a vector light field with distance includes a Gaussian light source A, a beam expander B, a diagonal (45°) linearly polarized light generator C, a generation system D for an arbitrary-structured vector beam, and a detection device E arranged in sequence from left to right. The generation system D is provided with a digital micromirror device DMD7 for digitally regulating the light field parameters.

[0038] Further, the beam expander B includes a first lens 1 with a focal length of 20 mm and a second lens 2 with a focal length of 200 mm. The beam expander B can collimate the beam and expand its size by ten times.

[0039] Further, the diagonal linearly polarized light generator C includes a half-wave plate (not shown) for adjusting the polarization state of the output beam to 45 degrees diagonally.

[0040] Further, the generation system D includes a Wollaston prism 3 for projecting a +45° linearly polarized light into two beams with equal light intensity along the horizontal and vertical polarization directions, and the transmission angle between the two beams with orthogonal polarization states is 1.5°.

[0041] Further, the generation system D also includes a quarter-wave plate 4 for changing the horizontal and vertical linear polarization states to left-handed and right-handed circular polarizations respectively. The generation system D also includes a third lens 5 with a focal length of 150 mm and a fourth lens 6 with a focal length of 150 mm.

[0042] Further, the generation system D also includes the digital micromirror device DMD7. The hologram loaded by the digital micromirror device DMD7 includes a digital grating. By adjusting the grating coefficient, the two beams of left-handed and right-handed circularly polarized light can be made to transmit along the same transmission path.

[0043] Furthermore, the circular Airy vortex vector beam generated by the generation system D is expressed as:

[0044]

[0045] where cosθ, is the weight factor, (r, φ) are the cylindrical coordinate parameters, and are the left- and right-handed circular polarization basis vectors. Additionally, is the phase difference between the two polarization basis vectors, and serve as two orthogonal spatial mode basis vectors, which are circular Airy vortex beams carrying orbital angular momentum respectively, is the Planck constant.

[0046] Furthermore, the circular Airy vortex beam can be expressed as:

[0047]

[0048] where Ai() represents the Airy function; r is the radius, r0 is the radius of the main ring of the beam; a is the cut-off factor; ω is the beam waist radius; m is the topological charge; v is the initial emission angle parameter.

[0049] Furthermore, without moving any optical components, the circular Airy vortex optical field can be regulated by the digital micromirror device DMD7 through a computer for the topological charge parameter of the target optical field, so as to realize the regulation of the inter-mode phase angle with the beam transmission distance.

[0050] Furthermore, the detection device E includes a polarization analyzer 8 with adjustable angle and a CCD receiving device 9. By recording the light intensities under different conditions, the inter-mode phase distribution of the beam is reconstructed, so as to realize the observation of the rotation of the inter-mode phase angle of the beam with the beam transmission.

[0051] Furthermore, the generated beam is passed through the polarization analyzer 8 with angles adjusted to 0°, 45°, 90° and 135° respectively, and then the light intensities Ih, Id, Iv and Ia of the four beams under different conditions are recorded by the CCD receiving device 9.

[0052] Furthermore, the Stokes parameters S1 and S2 are obtained through the four light intensity values Ih, Id, Iv and Ia.

[0053] Furthermore, through the Stokes parameters S1 and S2, the transverse inter-mode phase distribution of the obtained target optical field is reconstructed, so as to observe the angular rotation of the phase with the beam transmission.

[0054] Furthermore, by modulating the topological charge parameter of the light beam and measuring the inter-mode phase of the light beam during the transmission process, the control of the rotation angle of the inter-mode phase with respect to the distance can be achieved.

[0055] Specifically, the Gaussian light source A is a 532 nm laser source. Modulating it into a circular Airy vortex vector optical field can achieve controllable rotation of the inter-mode phase of the optical field with respect to the transmission distance.

[0056] Figure 2 Shows three circular Airy vortex vector optical fields with different topological charge parameters {m1, m2} The transverse inter-mode phase diagrams under three different conditions where the transmission distances are z = 0 mm, z = 720.0 mm, and z = 783.0 mm respectively. Other parameters of the light beam are a = 0.4, ω = 0.1, r0 = 1, v1 = v2 = 0. As the transmission distance increases, the inter-mode phase of the vortex optical field with topological charge parameter {1, -1} does not rotate, that is, Δφ = 0 as shown in Fig. (a); the inter-mode phase of the vortex optical field with topological charge parameter {1, 0} rotates clockwise by π / 2, that is As shown in Fig. (b); the inter-mode phase of the vortex optical field with topological charge parameter {1, -2} rotates counterclockwise by π / 3, that is As shown in Fig. (c); the relationship between the rotation angle of the inter-mode phase and the topological charge parameter satisfies: Therefore, the topological charge parameter of the target vector light beam can be regulated by the digital micromirror device DMD7, thereby controlling the rotation angle of the inter-mode phase of the optical field with respect to the distance.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the technical solutions of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims

1. A system for adjusting the phase rotation angle between modes of a vector optical field with distance, characterized in that: It includes a Gaussian light source (A), a beam expander (B), a diagonal linearly polarized light generator (C), a generating system (D) for an arbitrary structured vector beam, and a detection device (E) arranged in sequence from left to right. The beam expander (B) includes a first lens (1) with a focal length of 20 mm and a second lens (2) with a focal length of 200 mm. The diagonal linearly polarized light generator (C) includes a half-wave plate. The generating system (D) includes a Wollaston prism (3), a quarter-wave plate (4) for changing the polarization state of the beam, a third lens (5) with a focal length of 150 mm, a fourth lens (6) with a focal length of 150 mm, and a digital micromirror device DMD (7) for digitally regulating the light field parameters. The detection device (E) includes an analyzer (8) and a CCD receiving device (9); The circular Airy vortex vector beam generated by the generating system (D) is expressed as: Among them, is the weight factor, and (r, φ) are the cylindrical coordinate parameters. and are the left - and right - hand circularly polarized basis vectors. Additionally, is the phase difference existing between the two polarization basis vectors. and serve as two orthogonal spatial mode basis vectors, which are circular Airy vortex beams carrying orbital angular momentum respectively. is the Planck constant. The circular Airy vortex beam can be expressed as: where Ai() represents the Airy function; r is the radius, r0 is the main ring radius of the beam; a is the cut-off factor; ω is the waist radius; m is the topological charge; v is the initial emission angle parameter; By selecting two spatial modes and with different topological charges m1 and m2, an operation with adjustable rotation of the inter-mode phase angle of the obtained light beam can be realized. The specific relationship is as follows: Through the digital micromirror device DMD (7), digital regulation of the topological charge parameter of the target beam can be achieved, so as to realize flexible regulation of the inter-mode phase rotation angle of the vector light field based on topological charge modulation with the transmission distance.

2. A system for adjusting the phase rotation angle between modes of a vector optical field with distance according to claim 1, characterized in that: Without moving any optical components, the circular Airy vortex light field can pass through the digital micromirror device DMD (7), and the target light field is digitally binary encoded by a computer to generate any circular Airy vortex vector beam that meets the requirements.

3. The system for adjusting the phase rotation angle between modes of a vector optical field according to claim 2, wherein: By adjusting the angles of the analyzer (8) to 0°, 45°, 90°, and 135° respectively, and then using the CCD receiving device (9) to record the corresponding light intensities, the Stokes parameters S1 and S2 can be obtained. The specific relationship is: S1 = I h -I v , S2 = I d -I a .

4. A system for adjusting the phase rotation angle between modes of a vector optical field with distance according to claim 3, characterized in that: Using the obtained Stokes parameters S1 and S2, the inter-mode phase distribution of the vector light field can be reconstructed, so as to realize the observation that the inter-mode phase angle of the obtained beam rotates with the transmission of the beam. The specific relationship is: φ = arctan(S2 / S1).

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