High-resolution adjustable polarization state distribution vector light field generation system based on scattering focusing

Abstract

The invention discloses a high-resolution adjustable polarization state distribution vector light field generation system based on scattering focusing, and the system comprises a laser which is used for transmitting laser and enabling the laser to enter a 4f system; the 4f system is used for performing beam combination on orthogonal circularly polarized light to generate a vector light field, and comprises a spatial light modulator capable of performing pure phase modulation on the light field, a first Fourier lens, a second Fourier lens, a double-hole filter, a doublet # imgabs0 # wave plate and a Ronchi grating. The spatial light modulator, the first Fourier lens, the double-hole filter, the doublet # imgabs 1 # wave plate, the second Fourier lens and the Ronchi grating are arranged in sequence, the double-hole filter is tightly attached to the doublet # imgabs 2 # wave plate, and the distance between the components is the focal length f of the Fourier lens; a high-resolution vector light field in any polarization state can be generated behind an anisotropic strong scattering medium, the polarization state can be regulated and controlled, and the focusing effect of the vector light field is improved by nearly 10 times compared with that of a traditional Fourier lens.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technologies, and particularly to a high-resolution adjustable polarization state distribution vector optical field generation system based on scattering focusing. Background Art

[0002] When a light beam propagates in an anisotropic medium, phase polarization or depolarization effects will occur. After scattering by the anisotropic medium, the polarization and phase of the light change, and finally only randomly polarized outgoing speckles can be observed.

[0003] In 2007, the Mosk research group used wavefront modulation technology to enable light to be focused after passing through a scattering medium, and this research has attracted wide attention. In addition, the propagation process of light in complex media has also been proven to be able to be characterized using a vector transfer matrix (VTM). In just over a decade, the regulation of scattering light fields based on wavefront shaping technology has developed rapidly and has been widely applied in many fields.

[0004] With the development of scattering light field regulation technology based on wavefront shaping, more and more interest has been aroused in manipulating the phase of the light field passing through a scattering medium. Similarly, the vector polarization transfer matrix (VPTM) that can regulate the polarization state of the light field has attracted the attention of scholars due to its convenient regulation method. However, most of the research on the polarization state of vector beams is limited to traditional conditions, and the research on reconstructing and regulating them after passing through strongly anisotropic scattering media is currently not abundant.

[0005] In 2012, Tripathi et al. proposed a method for measuring the VTM. This method can measure the VTM of a scattering medium through the four-step phase shift method and focus on the target light field through phase conjugation. However, the focused light field is usually limited to the polarization state of the incident light and the polarization state of the focus point is uncontrollable. At present, there is no flexible and stable method on the market to reconstruct a vector optical field with high-resolution arbitrarily adjustable polarization state after passing through a strongly anisotropic scattering medium. Exploring such a method is an urgent problem to be solved at present. Summary of the Invention

[0006] In order to overcome the above deficiencies in the prior art, the present invention provides a high-resolution arbitrarily adjustable polarization state distribution vector optical field generation system based on scattering focusing, so as to realize the calculation of the vector polarization transfer matrix of a vector optical field based on orthogonally circularly polarized light, and use the vector polarization transfer matrix to realize the reconstruction of the vector optical field after passing through a strongly anisotropic scattering medium, and by adjusting the elements in a vector transfer matrix, the additional phase of any polarized light component in the vector optical field can be changed to achieve the focusing of a high-resolution arbitrarily polarized state vector optical field.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: A high-resolution adjustable polarization state distribution vector light field generation system based on scattering focusing, comprising:

[0008] A laser, configured to emit laser light and incident on a 4f system;

[0009] The 4f system is configured to combine orthogonally circularly polarized light to generate a vector light field, and includes a spatial light modulator capable of performing pure phase modulation on the light field, a first Fourier lens, a second Fourier lens, a double-hole filter, a doublet wave plate and a Ronchi grating; the sequential arrangement order is the spatial light modulator, the first Fourier lens, the double-hole filter, the doublet wave plate, the second Fourier lens, the Ronchi grating, and the double-hole filter is closely attached to the doublet wave plate. Except for this, the distance between each component is the focal length f of the Fourier lens. After the laser light is incident on the spatial light modulator, the +1 order light beams on the x-axis and y-axis of the subsequent spectral plane are extracted through the double-hole filter, and the two light beams are respectively passed through different cemented surfaces of the doublet wave plate to be converted into circularly polarized light with orthogonal left-handed and right-handed polarization directions, and finally the two light beams are combined into a vector light beam through the Ronchi grating;

[0010] An anisotropic strong scattering medium, configured to allow the vector light beam to pass through and undergo scattering;

[0011] A first microscope objective lens and a second microscope objective lens, configured to scale the speckles generated after the anisotropic strong scattering medium; the first microscope objective lens is configured to converge the energy of the incident light to penetrate the anisotropic strong scattering medium, and the second microscope objective lens is configured to collect the scattered optical signal after penetrating the anisotropic strong scattering medium; A wave plate and a polarizer are configured to control the polarization state of the light received by the CMOS receiver;

[0012] The CMOS receiver is configured to receive the polarized light signal of the polarizer and transmit it to the control device;

[0013] Among them, by using the phase modulation based on the 4f system, the generated vector light field is as shown in the following formula (1):

[0014]

[0015] where A0 is the amplitude, m represents the topological charge number, represents the initial phase, δ1 and δ2 are respectively the additional phases of the x component and y component loaded into the spatial light modulator. This vector light field is mainly determined by the topological charge number m and the initial phase , that is, by adjusting parameters such as the topological charge number and the initial phase, a vector light field with a corresponding polarization state can be obtained.

[0016] Furthermore, a vector optical field is obtained by the coherent superposition of two circularly polarized lights orthogonal to the left-handed and right-handed polarization directions and passes through the anisotropic strong scattering medium. Its vector polarization transfer matrix (VPTM) is shown in the following formula:

[0017] T = ∑ m,n,p,q [K 1,PTM (m,n,p,q)K 2,PTM (m,n,p,q)], (Formula 2);

[0018] K PTM = [K 0° K 90° K R K L T , (Formula 3);

[0019] where m, n, p, and q respectively represent the points (m, n) in the input plane and the points (p, q) in the output plane, and K PTM is the polarization transfer matrix of the beam component.

[0020] Furthermore, the vector beam is focused on the anisotropic strong scattering medium through the first microscope objective lens, and then collected by the second microscope objective lens and transmitted to the CMOS receiver in the form of a target polarization intensity speckle pattern through a wave plate and a polarizer. Taking each column of the Hadamard matrix as the input mode, according to the four-step phase-shifting method and by measuring the corresponding input mode, the components of the vector transfer matrix (VPTM) of the anisotropic strong scattering medium are obtained.

[0021] Furthermore, by performing a conjugate operation on the vector polarization transfer matrix (VPTM), the modulated wavefront phase is obtained and loaded onto the spatial light modulator, thereby overcoming the scattering effect brought by the anisotropic strong scattering medium. The modulation function of the spatial light modulator is shown in the following Formula 4:

[0022]

[0023] where γ represents the modulation depth, f0 represents the spatial carrier frequency corresponding to the Ronchi grating, and respectively represent the phase distribution carried by the left-handed and right-handed circular polarization bases. The left-handed and right-handed circularly polarized lights are respectively regulated through and so as to be able to generate a high-resolution arbitrarily adjustable polarization state vector optical field behind the scattering medium. By changing the topological charge number m and the initial phase a vector optical field with the target polarization state can be generated.

[0024] ​Furthermore, the anisotropic strong scattering medium is an anisotropic material made of zinc oxide (ZnO) nanoparticles.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) It can generate a vector light field with an arbitrary polarization state and high resolution behind the anisotropic strong scattering medium. Its polarization state can be regulated, and the focusing effect of the vector light field is nearly 10 times higher than that of the traditional Fourier lens focusing.

[0027] (2) It has high flexibility and can generate a vector light field with an arbitrary polarization state and high resolution by regulating the topological charge number and the initial phase. It can generate vortex light fields with different polarization states and high resolution, and the structure is stable.

[0028] (3) It is applicable to the fields that require focusing vector light fields with different polarization states and high resolution behind high-order scattering media, and has the characteristics of convenient operation, flexible regulation, and stable effect. Description of the Drawings

[0029] Figure 1 is a schematic structural diagram of the present invention;

[0030] Figure 2 is a schematic diagram of the scattered focused beam of the vector light field based on orthogonal circularly polarized light;

[0031] Figure 3 is that the horizontal and vertical polarization state beams pass through the scattering medium and use this system to generate a vector light field with a high-resolution adjustable polarization state;

[0032] Figure 4 is the high-resolution adjustable polarization state vortex light field generated by using this system after passing through the scattering medium. (a) is the high-resolution adjustable polarization state vortex light field generated by horizontal and vertical polarized light; (b) is the high-resolution adjustable polarization state vortex light field generated by left-handed and right-handed polarized light.

[0033] In the figure: 4f system 1, spatial light modulator 2, first Fourier lens 3, double-hole filter 4, doublet wave plate 5, second Fourier lens 6, Ronchi grating 7, first microscope objective 8, scattering medium 9, second microscope objective 10, wave plate 11, polarizer 12, CMOS receiver 13. Detailed Embodiments

[0034] 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 the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0035] As Figures 1-4 shown, the technical solution adopted by the present invention is as follows: This embodiment provides and discloses a system for generating a scattered-focusing high-resolution arbitrarily adjustable polarization state distribution vector optical field, including a 4f system 1 that generates a vector optical field based on orthogonally circularly polarized light under the control of a control device, a laser for emitting laser light and incident on the 4f system 1, a first microscope objective 8 for converging on the target, an anisotropic strong scattering medium 9, a second microscope objective 10 for magnifying the target, a wave plate 11, a polarizer 12, a CMOS receiver 13, and a control device (such as Figure 1 the computer on the right in the figure).

[0036] Among them, the anisotropic strong scattering medium 9 is used to allow the vector beam to pass through and scatter, and is preferably an anisotropic material made of zinc oxide (ZnO) nanoparticles. The first microscope objective 8 and the second microscope objective 10 are used to scale the speckles generated after the anisotropic strong scattering medium 9; the first microscope objective 8 is used to converge the energy of the incident light to penetrate the anisotropic strong scattering medium 9, and the second microscope objective 10 is used to collect the light signals scattered after penetrating the anisotropic strong scattering medium 9; The wave plate 11 and the polarizer 12 are used to control the polarization state of the transmitted light; the CMOS receiver 13 is used to receive the target polarization light signal after the polarizer 12 and transmit it to the control device.

[0037] Furthermore, as Figure 1 shown, the 4f system is used to combine orthogonally circularly polarized light to generate a vector optical field, including a spatial light modulator 2 capable of modulating the phase of the optical field, a first Fourier lens 3, a second Fourier lens 6, a double-hole filter 4, a doublet wave plate 5, and a Ronchi grating 7; the sequential arrangement is the spatial light modulator 2, the first Fourier lens 3, the double-hole filter 4, the doublet wave plate 5, the second Fourier lens 6, the Ronchi grating 7, and the double-hole filter 4 is closely attached to the doublet wave plate 5. Except for this, the distance between each element is the focal length f of the Fourier lens. After the laser is incident on the spatial light modulator 2, the +1 order beams on the x-axis and y-axis of the subsequent spectral plane are extracted through the double-hole filter 4, and the two beams of light are respectively passed through the doublet The different bonding surfaces of the wave plate 5 convert into orthogonally left- and right-handed circularly polarized light with polarized directions, and finally the two beams of light are combined into a vector beam by the Ronchi grating 7; the input light fields with different polarizations and phase distributions depend on the hologram loaded on the spatial light modulator.

[0038] Furthermore, by using the phase modulation based on the 4f system, the generated vector light field is as shown in the following formula (1):

[0039]

[0040] where A0 is the amplitude, m represents the topological charge number, represents the initial phase, δ1 and δ2 are respectively the additional phases of the x-component and y-component loaded into the spatial light modulator (2). This vector light field is mainly determined by the topological charge number m and the initial phase , that is, by regulating parameters such as the topological charge number and the initial phase, a vector light field with a corresponding polarization state can be obtained.

[0041] Furthermore, the vector light field obtained by the coherent superposition of two orthogonally left- and right-handed circularly polarized lights passes through the anisotropic strong scattering medium 9, and its vector polarization transfer matrix (VPTM) is as shown in the following formula:

[0042] T = ∑ m,n,p,q [K 1,PTM (m,n,p,q)K 2,PTM (m,n,p,q)], (Formula 2);

[0043] K PTM = [K 0° K 90° K R K L T , (Formula 3);

[0044] where m, n, p, q respectively represent the points (m, n) in the input plane and the points (p, q) in the output plane, and K PTM is the polarization transfer matrix of the beam component.

[0045] Furthermore, the vector beam passes through the first microscope objective 8 and is focused on the anisotropic strong scattering medium 9, and then is collected by the second microscope objective 10 and transmitted to the CMOS receiver 13 in the form of a target polarization intensity speckle pattern through the wave plate 11 and the polarizer 12. Taking each column of the Hadamard matrix as the input mode, according to the four-step phase-shifting method and by measuring the corresponding input mode, the components of the vector polarization transfer matrix (VPTM) of the anisotropic strong scattering medium 9 are obtained.

[0046] ​Further, by performing a conjugate operation on the vector polarization transfer matrix (VPTM), the modulated wavefront phase is obtained and loaded onto the spatial light modulator 2, thereby overcoming the scattering effect brought by the strongly anisotropic scattering medium 9. The modulation function of the spatial light modulator 2 is shown in the following formula four:

[0047]

[0048] where γ represents the modulation depth, and f0 represents the spatial carrier frequency corresponding to the Ronchi grating. and respectively represent the phase distribution carried by the left-handed and right-handed circular polarization bases. The left-handed and right-handed circularly polarized lights are respectively regulated by and so as to be able to generate a high-resolution arbitrarily adjustable polarization state vector light field behind the scattering medium 9. By changing the topological charge number m and the initial phase a vector light field with the target polarization state can be generated.

[0049] Further, by changing the topological charge number m, a high-resolution vortex light field with the target polarization can be generated behind the strongly anisotropic scattering medium, and the vector focusing effect is nearly 10 times higher than that of the traditional Fourier lens focusing.

[0050] Specifically, the light source is a laser source with a wavelength of 532 nm. Through a high-resolution arbitrarily adjustable polarization state distribution vector light field generation system based on scattering focusing, the generation of the target polarization vector can be realized, and the measurement of the vector polarization transfer matrix can be realized. Furthermore, by using its vector polarization transfer matrix, a vector light field with an arbitrarily adjustable polarization state can be generated behind the strongly anisotropic scattering medium 9.

[0051] 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 recorded 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 in the protection scope of the present invention.

Claims

1. A high-resolution tunable polarization state distribution vector optical field generation system based on scattering focusing, characterized in that, Including: A laser for emitting laser light and incident on a 4f system (1); The 4f system (1) is used to generate a vector light field by combining orthogonally circularly polarized lights, and includes a spatial light modulator (2) capable of performing pure phase modulation on the light field, a first Fourier lens (3), a second Fourier lens (6), a double-hole filter (4), a double-glued wave plate (5) and a Ronchi grating (7); the sequential arrangement order is the spatial light modulator (2), the first Fourier lens (3), the double-hole filter (4), the double-glued wave plate (5), the second Fourier lens (6), the Ronchi grating (7), and the double-hole filter (4) is closely attached to the double-glued wave plate (5), and the distance between each component is the focal length f of the Fourier lens except for this. After the laser is incident on the spatial light modulator (2), the +1 order beams on the x-axis and y-axis of the subsequent spectral plane are extracted through the double-hole filter (4), and the two beams of light are respectively passed through the double-glued different glued surfaces of the wave plate (5) to be converted into circularly polarized lights with orthogonal left-handed and right-handed polarization directions, and finally the two beams of light are combined into a vector beam through the Ronchi grating (7); An anisotropic strong scattering medium (9) for allowing a vector beam to pass through and scatter; A first microscope objective lens (8) and a second microscope objective lens (10) for scaling the speckles generated after the anisotropic strong scattering medium (9); The first microscope objective lens (8) is used to converge the energy of incident light to penetrate the highly anisotropic strongly scattering medium (9), and the second microscope objective lens (10) is used to collect the optical signal scattered after penetrating the highly anisotropic strongly scattering medium (9); The wave plate (11) and the polarizer (12) are used to control the polarization state of the light received by the CMOS receiver (13); A CMOS receiver (13) for receiving the polarized light signal of a polarizer (12) and transmitting it to a control device; Among them, using phase modulation based on a 4f system, the generated vector optical field is as shown in the following formula (1): where A0 is the amplitude, m represents the topological charge number, represents the initial phase, δ1 and δ2 are respectively the additional phases of the x-component and y-component loaded into the spatial light modulator (2). This vector optical field is mainly determined by the topological charge number m and the initial phase That is, by adjusting parameters such as the topological charge number and the initial phase, a vector optical field with a corresponding polarization state can be obtained.

2. The high-resolution adjustable polarization state distribution vector optical field generation system based on scattering focusing according to claim 1, wherein: The vector optical field obtained by the coherent superposition of two circularly polarized lights with orthogonal left-handed and right-handed polarization directions passes through the anisotropic strong scattering medium (9), and its vector polarization transmission matrix (VPTM) is as shown in the following formula: T = ∑ m,n,p,q [K 1,PTM (m,n,p,q)K 2,PTM (m,n,p,q)], (Formula 2); K PTM = [K 0° K 90° K R K L T , (Equation 3);​ where m, n, p, and q represent the points (m, n) in the input plane and the points (p, q) in the output plane, respectively, and K PTM is the polarization transfer matrix of the beam component.

3. The high-resolution adjustable polarization state distribution vector optical field generation system based on scattering focusing according to claim 2, characterized in that: The vector beam is focused on the anisotropic strong scattering medium (9) through the first microscope objective (8), and then collected by the second microscope objective (10) and transmitted to the CMOS receiver (13) in the form of a target polarization intensity speckle pattern through the wave plate (11) and the polarizer (12). Taking each column of the Hadamard matrix as the input mode, and according to the four-step phase-shifting method and by measuring the corresponding input modes, the components of the vector propagation matrix (VPTM) of the anisotropic strong scattering medium (9) are obtained.

4. The high-resolution adjustable polarization state distribution vector optical field generation system based on scattering focusing according to claim 3, wherein: By performing a conjugate operation on the vector polarization transmission matrix (VPTM), the modulated wavefront phase is obtained and loaded onto a spatial light modulator (2), thereby overcoming the scattering effect brought by the anisotropic strong scattering medium (9). The modulation function of the spatial light modulator (2) is as shown in the following formula (4): where γ represents the modulation depth and f0 represents the spatial carrier frequency corresponding to the Ronchi grating, and represent the carried phase distributions of the left-handed and right-handed circular polarization bases respectively. The left-handed and right-handed circularly polarized lights are respectively regulated through and so as to be able to generate a high-resolution arbitrarily adjustable polarization state vector light field behind the scattering medium (9). By changing the topological charge number m and the initial phase a vector light field with the target polarization state can be generated.

5. The high-resolution tunable polarization state distribution vector optical field generation system based on scattering focusing according to claim 1, characterized in that: The anisotropic strong scattering medium (9) is an anisotropic material made of zinc oxide (ZnO) nanoparticles.

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