Optical system for focusing multi-polarization state light field at different points based on scattering focusing

Abstract

The application discloses an optical system for realizing multi-polarization-state light field focusing at different points based on scattering focusing, which comprises a laser for emitting laser light and incident to a 4f system; the 4f system is used for superimposing two beams of orthogonal circularly polarized light to generate a vector light field, and comprises a spatial light modulator capable of modulating the phase of the light field, a first Fourier lens, a second Fourier lens, a double-hole filter, a double-cemented wave plate and a Ronchi grating; the elements are arranged in the order of the spatial light modulator, the first Fourier lens, the double-hole filter, the double-cemented wave plate, the second Fourier lens and the Ronchi grating; the double-hole filter is close to the double-cemented wave plate, and the distance between each element is the focal length f of the Fourier lens; the corresponding vector transmission matrix is calculated by extracting different polarization-state components in the medium backscattering speckle, and the different polarization-state multi-point simultaneous focusing after the scattering medium is realized by using the vector transmission matrix of different components, and the focusing position can be arbitrarily controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, in particular to an optical system for realizing multi-polarization-state light field focusing at different points based on scattering focusing. BACKGROUND

[0002] The scattering of tiny particles in the computer scattering medium will make the light wave deviate from the original propagation direction, resulting in a disordered light field and forming speckles. In the early days, people believed that scattering was irreversible. In 2007, the Mosk group used wavefront modulation technology to change the wavefront phase of light after passing through the scattering medium, making it realize focusing after the medium, which attracted widespread attention. In addition, the propagation process of light in complex medium has also been proven to be characterized by vector transmission matrix (VTM). In just a few decades, the scattering light field regulation based on wavefront shaping technology has developed rapidly and has been widely used in many fields.

[0003] With the development of scattering light field regulation based on wavefront shaping, focusing different polarization states of light field after scattering medium has attracted more and more interest. Similarly, light fields with special phase distribution such as caustic or vortex light field have attracted the attention of scholars because of their special focusing characteristics. However, most of the researches are limited to traditional conditions, and the research on reconstruction and regulation after high-order scattering medium is still not rich.

[0004] In 2012, Tripathi et al. proposed a method for measuring VTM. This method can measure the VTM of the scattering medium through a four-step phase shift method, and focus the target light field through phase conjugation, but the focused light field is usually consistent with the incident light polarization state or hybrid polarization state. At present, there is no flexible and stable method to produce light fields with different polarization states simultaneously after the scattering medium, so exploring such a method is an urgent problem to be solved. SUMMARY

[0005] In order to overcome the defects in the prior art, the present application provides an optical system for realizing multi-polarization-state light field focusing at different points based on scattering focusing, which realizes the calculation of the vector transmission matrix of the vector light field based on orthogonal circularly polarized light, and realizes the reconstruction of the vector light field after the high-order scattering medium by using the vector transmission matrix. The corresponding vector transmission matrix can be calculated by extracting different polarization state components in the speckle after the medium, and different polarization state multi-point focusing after the scattering medium can be realized by using the vector transmission matrix of different components, and the arbitrary regulation of the focusing position can be realized.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: the optical system for realizing multi-polarization-state light field focusing at different points based on scattering focusing comprises:

[0007] laser, for emitting laser and incident 4f system;

[0008] the 4f system, for superimposing two beams of orthogonal circularly polarized light to generate a vector light field, comprising a spatial light modulator capable of modulating the phase of the light field, a first Fourier lens, a second Fourier lens, a double-hole filter, a double-cemented wave plate and a Ronchi grating; the order of arrangement is spatial light modulator, first Fourier lens, double-hole filter, double-cemented wave plate, second Fourier lens, Ronchi grating, double-hole filter close to double-cemented wave plate, and the distance between each element is the focal length f of the Fourier lens; after the laser is incident on the spatial light modulator, the +1 order beams of x-axis and y-axis on the rear spectrum plane are extracted through the double-hole filter, and the two beams of light pass through the double-cemented wave plate through different cemented surfaces to convert into circularly polarized light with orthogonal left-handed and right-handed polarization directions, and finally the two beams of light are combined into a vector light beam through the Ronchi grating;

[0009] high-order scattering medium, for allowing the vector light beam to pass through and scatter;

[0010] first microscopic objective lens and second microscopic objective lens, for zooming the speckles generated after the high-order scattering medium; the first microscopic objective lens is used for converging the energy of incident light to penetrate the high-order scattering medium, and the second microscopic objective lens is used for collecting the scattered light signal after penetrating the high-order scattering medium;

[0011] wave plate and polarizer, for extracting different polarization state components in the outgoing speckle to obtain speckles of different polarization states;

[0012] CMOS receiver, for receiving the light signal emitted after the polarizer and transmitting to the control device;

[0013] wherein, by using phase modulation based on the 4f system, the generated vector light field is as shown in the following formula one:

[0014] , (formula one);

[0015] wherein is the amplitude, and are the additional phases of x direction and y direction loaded into the spatial light modulator.

[0016] Further, the vector light field obtained by coherently superimposing two orthogonal circularly polarized light beams with left-handed and right-handed polarization directions passes through the high-order scattering medium, and the vector transmission matrix (VTM) thereof is as shown in the following formula two: , (formula two);

[0017] where m, n, p, q represent the input plane (m, n) point and the output plane (p, q) point respectively.

[0018] Further, the vector beam is focused on the high-order scattering medium through the first microscope objective, then collected by the second microscope objective, and transmitted to the CMOS receiver in the form of intensity speckle pattern. The wave plate and the polarizer extract components of different polarization states, which are transmitted to the CMOS receiver in the form of intensity speckle pattern, and each column of the Hadamard matrix is taken as an input mode, and the whole components of the vector transmission matrix (VTM) of the high-order scattering medium are obtained according to the four-step phase shift method and by measuring the corresponding input mode calibration elements.

[0019] Further, by performing conjugate operation on the whole vector transmission matrix (VTM), the modulation wavefront phase is obtained and loaded to the spatial light modulator, so as to overcome the scattering effect of the high-order scattering medium, and the modulation function of the spatial light modulator is shown in the following formula three:

[0020] , (formula three);

[0021] wherein represents the modulation depth, represents the spatial carrier frequency.

[0022] Further, by adding an arbitrary target phase, such as a twisted phase , a vortex phase , in the holographic phase pattern of the spatial light modulator, the focal caustic and vortex light fields with different polarization states can be focused at different positions on the back focal plane of the high-order scattering medium at the same time, and the modulation function of the spatial light modulator is shown in the following formula four:

[0023] , (formula four);

[0024] wherein , ; represents the modulation depth, represents the spatial carrier frequency, , , and respectively represent the phase of the Hadamard base corresponding to , , and , the left-handed and right-handed circularly polarized light is regulated by and respectively, so that multiple light fields with different polarization states can be generated at the same time and focused at different positions on the focal plane behind the scattering medium.

[0025] Furthermore, the higher-order scattering medium is an anisotropic material made of zinc oxide (ZnO) nanoparticles.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The vector transfer matrix corresponding to the different polarization state components in the speckle behind the medium is calculated, and the vector transfer matrix of different components is used to achieve simultaneous focusing of multiple points with different polarization states after passing through the scattering medium, and the focusing position can be arbitrarily adjusted.

[0028] (2) It is highly flexible and can calculate the vector transfer matrix of the vector light field based on orthogonally circularly polarized light, and use the vector transfer matrix to reconstruct the vector light field after passing through a higher-order scattering medium, and the structure is stable.

[0029] (3) It is suitable for fields where multiple objects with different polarization states need to be focused simultaneously on the back focal plane of a high-order scattering medium. It features convenient operation, flexible control, and stable effect. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the present invention;

[0031] Figure 2 This is a schematic diagram of light fields with different polarization states that are simultaneously focused at different positions within the same focal plane by the system provided by the present invention.

[0032] Figure 3 This is a schematic diagram of a focused light field with different polarization states carrying a distorted phase generated by the system provided by the present invention.

[0033] In the diagram: 1. 4f system; 2. Spatial light modulator; 3. First Fourier lens; 4. Two-aperture filter; 5. Cemented doublet. 5. Waveplate; 6. Second Fourier lens; 7. Ronche grating; 8. First microscope objective; 9. Scattering medium; 10. Second microscope objective. Wave plate 11, polarizer 12, CMOS receiver 13. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] like Figures 1-3As shown, the technical scheme adopted by the present application is as follows: the embodiment provides an optical system for realizing multi-polarization state light field focusing at different points based on scattering focusing, which comprises a 4f system 1 generating a vector light field based on orthogonal circularly polarized light under the control of a control device, a laser for emitting laser and incident to the 4f system, a first microscopic objective 8 for converging a target, a high-order scattering medium 9, a second microscopic objective 10 for amplifying a target, a wave plate 11, a polarizer 12, a CMOS receiver 13 and the control device (such as Figure 1 a computer on the right side of the middle).

[0036] The high-order scattering medium 9 is used for allowing the vector light beam to pass through and be scattered, and is preferably an anisotropic material made of zinc oxide (ZnO) nanoparticles. The first microscopic objective 8 and the second microscopic objective 10 are used for zooming the speckle generated after the high-order scattering medium 9; the first microscopic objective 8 is used for converging the energy of incident light to penetrate the high-order scattering medium 9, and the second microscopic objective 10 is used for collecting the scattered light signal after penetrating the high-order scattering medium 9; The wave plate 11 and the polarizer 12 are used for extracting components of different polarization states in the light signal collected by the second microscopic objective 10; and the CMOS receiver 13 is used for receiving the different component light signals extracted after the polarizer 12 and transmitting the light signals to the control device.

[0037] Further, as shown in the figure, Figure 1 The 4f system is used for superimposing two beams of orthogonal circularly polarized light to generate a vector light field, which comprises a spatial light modulator 2 capable of modulating the phase of the light field, a first Fourier lens 3, a second Fourier lens 6, a double-hole filter 4, a double-cemented wave plate 5 and a Ronchi grating 7; the elements are arranged in the order of the spatial light modulator 2, the first Fourier lens 3, the double-hole filter 4, the double-cemented wave plate 5, the second Fourier lens 6, the Ronchi grating 7, and the double-hole filter 4 is close to the double-cemented wave plate 5, and the distance between each element is the focal length f of the Fourier lens. After the laser is incident to the spatial light modulator 2, the +1 order light beams on the x-axis and the y-axis on the rear spectrum plane are extracted through the double-hole filter 4, and the two beams of light are converted into circularly polarized light with orthogonal left-handed and right-handed polarization directions through the different cemented surfaces of the double-cemented wave plate 5, and finally the two beams of light are combined into a vector light beam through the Ronchi grating 7; the input light field with different polarization and phase distribution depends on the hologram loaded on the spatial light modulator.

[0038] Further, the generated vector light field is shown in the following formula one by using the phase modulation based on the 4f system

[0039] , (formula one).

[0040] in It is the amplitude. and These are the additional phases in the x and y directions, respectively, loaded into the spatial light modulator 2.

[0041] Furthermore, the vector light field obtained by the coherent superposition of two circularly polarized lights with orthogonal left-handed and right-handed polarization directions passes through the higher-order scattering medium 9, and its vector transfer matrix (VTM) is shown in the following formula 2:

[0042] (Formula 2);

[0043] Where m, n, p, q represent the input plane point (m, n) and the output plane point (p, q), respectively.

[0044] Furthermore, the vector beam is focused onto the higher-order scattering medium 9 by the first microscope objective 8, and then collected by the second microscope objective 10, and then... Waveplate 11 and polarizer 12 extract components of different polarization states and transmit them to CMOS receiver 13 in the form of intensity speckle map. Each column of the Hadamard matrix is ​​used as the input mode. The elements are calibrated by measuring the corresponding input modes according to the four-step phase shifting method, thereby obtaining all components of the vector transfer matrix (VTM) of the higher-order scattering medium 9.

[0045] Furthermore, by performing a conjugate operation on the entire vector transfer matrix (VTM), the modulation wavefront phase is obtained and loaded into the spatial light modulator 2, thereby overcoming the scattering effect caused by the higher-order scattering medium 9. The modulation function of the spatial light modulator 2 is shown in the following formula 3:

[0046] (Formula 3);

[0047] in Indicates modulation depth. Indicates spatial carrier frequency, , , and These represent the VTM. , , and The corresponding phases of the Hadamard basis, left-handed and right-handed circularly polarized light passing through... and By adjusting the light, multiple light fields with different polarization states can be generated simultaneously behind the scattering medium 9, which are focused at different positions on the focal plane.

[0048] Furthermore, by adding an arbitrary target phase, such as a distorted phase, to the holographic phase map of the spatial light modulator 2... , vortex phase , the focal plane on the high-order scattering medium after the focal plane on the different positions can be focused simultaneously with different polarization states of the focal and vortex light field, the modulation function of the spatial light modulator 2 is as follows formula four:

[0049] , (formula four);

[0050] wherein , .

[0051] Specifically, the light source is a laser source with a wavelength of 532 nm, and a kind of optical system based on scattering focusing can realize the generation of target focal vector vortex light field and the measurement of vector optical transfer matrix, and then the different polarization components of the vector transfer matrix are used to realize the simultaneous focusing of different polarization components of the vector light field at different positions on the same focal plane after the scattering medium 9;

[0052] Figure 2 It is described that the system can generate light fields with different polarization states focused at different positions on the same focal plane after the scattering medium 9;

[0053] Figure 3 It is described that the system can generate different polarization state focusing light field carrying twisted phase after the scattering medium 9.

[0054] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An optical system for focusing multi-polarization state light fields at different points based on scattering and focusing, characterized in that, include: Laser for emitting laser light and incident on a 4f system (1); The 4f system (1) is used to superimpose two orthogonally circularly polarized beams to generate a vector light field, and includes a spatial light modulator (2) capable of modulating the phase of the light field, a first Fourier lens (3), a second Fourier lens (6), a dual-aperture filter (4), and a double cemented carbide. Waveplate (5) and a Ronchi grating (7); arranged in the following order: spatial light modulator (2), first Fourier lens (3), dual-aperture filter (4), double cemented plate Waveplate (5), second Fourier lens (6), Ronche grating (7), double-aperture filter (4) tightly bonded together Waveplate (5), and the distance between all other components is the focal length f of a 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 spectrum are extracted through the dual-aperture filter (4), and the two beams are respectively made to pass through the double cemented carbide. The different cemented surfaces of the waveplate (5) are converted into circularly polarized light with orthogonal left-handed and right-handed polarization directions. Finally, the two beams are combined into a vector beam by the Ronchi grating (7). A higher-order scattering medium (9) is used to allow a vector beam to pass through and be scattered; The first microscope objective (8) and the second microscope objective (10) are used to scale the speckle generated behind the higher-order scattering medium (9); the first microscope objective (8) is used to focus the energy of the incident light to penetrate the higher-order scattering medium (9), and the second microscope objective (10) is used to collect the light signal scattered after penetrating the higher-order scattering medium (9). Wave plate (11) and polarizer (12) are used to extract different polarization state components in the outgoing speckle and obtain speckle with different polarization states; The CMOS receiver (13) is used to receive the light signal emitted after the polarizer (12) and transmit it to the control device; The vector optical field generated by phase modulation based on a 4f system is shown in Equation 1 below: (Formula 1); in It is the amplitude. and These are the additional phases in the x and y directions respectively loaded into the spatial light modulator (2); The vector light field obtained by the coherent superposition of two circularly polarized lights with orthogonal left-handed and right-handed polarization directions passes through the higher-order scattering medium (9), and its vector transmission matrix is ​​shown in the following formula 2: (Formula 2); Where m, n, p, q represent the input plane point (m, n) and the output plane point (p, q), respectively; The vector beam is focused onto the higher-order scattering medium (9) by the first microscope objective (8), then collected by the second microscope objective (10), and then... Waveplate (11) and polarizer (12) extract components of different polarization states and transmit them to CMOS receiver (13) in the form of intensity speckle map. Each column of the Hadamard matrix is ​​used as the input mode. The elements are calibrated by measuring the corresponding input mode according to the four-step phase shifting method, thereby obtaining all components of the vector transmission matrix of the higher-order scattering medium (9).

2. The optical system for focusing multi-polarization state light fields at different points based on scattering focusing according to claim 1, characterized in that: By performing a conjugate operation on the entire vector transmission matrix, the modulation wavefront phase is obtained and loaded into the spatial light modulator (2), thereby overcoming the scattering effect caused by the higher-order scattering medium (9). The modulation function of the spatial light modulator (2) is shown in the following formula 3: (Formula 3); in Indicates modulation depth. Indicates the spatial carrier frequency.

3. The optical system for focusing multi-polarization state light fields at different points based on scattering focusing according to claim 2, characterized in that: By adding a distorted phase to the holographic phase map of the spatial light modulator (2) or vortex phase At least one of them can simultaneously focus caustic and vortex light fields with different polarization states at different positions on the back focal plane of the higher-order scattering medium. The modulation function of the spatial light modulator (2) is expressed as follows in Formula 4: (Formula 4); in , ; Indicates modulation depth. Indicates spatial carrier frequency, , , and These represent the vector transfer matrix respectively. , , and The corresponding phases of the Hadamard basis, left-handed and right-handed circularly polarized light passing through... and By adjusting the light field, multiple light fields with different polarization states can be generated simultaneously behind the higher-order scattering medium (9) and focused at different positions on the focal plane.

4. The optical system for focusing multi-polarization state light fields at different points based on scattering focusing according to claim 1, characterized in that: The higher-order scattering medium (9) is an anisotropic material made of zinc oxide nanoparticles.

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