A high-resolution focal vector vortex light field generation system based on scattering focusing

Abstract

The application discloses a high-resolution focal vector vortex light field generation system based on scattering focusing, which mainly comprises a 4f system for generating a focal vector vortex light field, a microscopic objective lens for converging and amplifying a target, a scattering medium and a CMOS receiver, wherein the 4f system comprises a spatial light modulator for modulating a phase. The system can generate a focal vector vortex light field of the target by regulating the focal scattering and the vortex phase, can quickly calculate a vector optical transfer matrix, and can generate a high-resolution focal vector vortex light field of the target after the scattering medium. The system is suitable for industries requiring high-resolution focal vector vortex light fields after the scattering medium. In addition, the system can generate a high-resolution focal vector vortex light field with an angular polarization state change by adding an angular phase, and has the characteristics of convenient operation, flexible regulation, high light field resolution and stable effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, in particular to a high-resolution focal vector vortex light field generation system based on scattering focusing. BACKGROUND

[0002] The traditional optical imaging rule that light propagates along a straight line is taken as a common sense in daily life, but this is a case that occurs in a relatively clean environment. The limitation of this statement is that when the light beam propagates in a non-uniform medium, phase deviation or depolarization effect may occur, and people's common sense is no longer applicable.

[0003] The wavefront phase of light changes after passing through a scattering medium, and finally only the exit speckle image can be observed. In 2007, Mosk's group used wavefront modulation technology to make the light transmitted through the scattering medium focusable, and the wavefront phase modulation technology attracted widespread attention. It is known that the optical transfer matrix can combine the exit light transmitted through the scattering medium with the incident light, and use the phase conjugation technology to realize focusing and imaging at any position and time. In recent years, with the continuous study of scattered light, scattering focusing technology has become more and more rich. Through the study of the properties of scattered light, through various ways, the application of focusing and imaging through scattering medium has been realized.

[0004] Focal caustic light field with special phase distribution has attracted the attention of scholars due to its self-focusing, self-reconstruction, self-healing and other characteristics and special focusing characteristics. Similarly, vector light field has always been widely concerned due to its non-uniform polarization state in space. However, most of the research on focal caustic light beam is limited to scalar light field, and the application of focal caustic vector light field to vector light field with non-uniform polarization state is not rich at present.

[0005] In 2012, Tripathi et al. proposed a method for measuring VTM. With this method, the VTM of the scattering medium can be calculated, and the target light field can be focused through phase conjugation and four-step phase shift method. However, for complex vector light field, such as focal caustic vortex vector light field, there is no flexible and stable method to generate focal caustic vector vortex light field behind the scattering medium at present, especially the focal caustic vector vortex light field with high resolution. Therefore, it is urgent to explore such a method. SUMMARY

[0006] In order to solve the above problems, a high-resolution focal vector vortex light field generation system based on scattering focusing is invented in this work. This method can generate target focal vector vortex light field by controlling focal and vortex phase, which not only can quickly calculate vector optical transfer matrix, but also can generate target focal vector vortex light field with high resolution behind the scattering medium.

[0007] Technical solution

[0008] A high-resolution caustic vector vortex light field generation system based on scattering focusing includes a laser generator, a 4f system (1) that generates a vector light field based on the superposition of two orthogonally circularly polarized beams, a microscope objective (3) for focusing the target, a scattering medium (4), a microscope objective (5) for magnifying the target, a CMOS receiver (6), and a control device. The 4f system (1) includes a spatial light modulator (2) that modulates the phase. The microscope objective (3) that focuses the target is used to focus the energy of the incident light to penetrate the scattering medium (4), and the microscope objective (5) that magnifies the target is used to collect the scattered signal after passing through the scattering medium (4). The 4f system (1) includes a spatial light modulator (2) that modulates the phase, two Fourier lenses, a dual-aperture filter, and a double cemented doublet. The system consists of a waveplate and a Ronchi grating. A dual-aperture filter is used to extract the +1 order beams on the x-axis and y-axis of the spatial light modulator (2) after reflection. The two beams are then passed through a double cemented plate. Different cemented surfaces of the waveplate are converted into left-handed and right-handed circularly polarized light. The left-handed and right-handed circularly polarized light are then superimposed collinearly through a Ronchi grating to generate a target vector beam. The input light field with different polarization and phase distribution depends on the hologram loaded on the spatial light modulator (2).

[0009] Using phase modulation based on the 4f system (1), the generated vortex optical field of the caustic vector is shown in the following formula:

[0010] (Formula 1);

[0011] Where A0 represents the amplitude. , , , , where n represents the vortex topological charge number and a represents the caustic coefficient. , Indicates wavelength. Represents the polar radius in polar coordinates. Indicates the initial phase. and These are the additional phases loaded into the spatial light modulator (2) in the x and y directions, respectively. The caustic vector vortex light field is mainly composed of... and caustic phase term in With vortex phase term The determination is made by adjusting the parameters of the caustic coefficient 'a' and the vortex topological charge 'n' to obtain the caustic vector vortex light field with the corresponding caustic intensity and the phase of the target vortex.

[0012] Further, the vectorial light field is obtained by the coherent superposition of two orthogonal circularly polarized lights passing through the scattering medium (4), and its vectorial transmission matrix (VTM) is shown in the following formula two:

[0013] (Formula two);

[0014] where m, n, p, q represent the input plane (m, n) point and the output plane (p, q) point, the vectorial light beam is focused on the scattering medium (4) through the microscope objective (3) converging on the target, and then collected by the microscope objective (5) amplifying on the target and transmitted to the CMOS receiver (6) in the speckle intensity diagram, taking each column of the Hadamard matrix as the input mode, according to the four-step phase shift method and by measuring the corresponding input mode calibration elements, the whole components of the VTM of the scattering medium (4) are obtained.

[0015] Further, the conjugate operation is performed on the vectorial transmission matrix (VTM) as a whole, and the obtained modulation wavefront phase is loaded to the spatial light modulator (2) to overcome the scattering effect, and the modulation function of the two-dimensional holographic grating is represented as:

[0016] (Formula three);

[0017] where represents the modulation depth, represents the spatial carrier frequency, , , n represents the topological charge of the vortex, and a represents the focal coefficient, , represents the wavelength, represents the polar radius in the polar coordinate system, represents the initial phase, and represent the phase distribution carried by the left-handed and right-handed circularly polarized bases, and the phase distribution of the focal scattering vector vortex light field of the target is added to the modulation wavefront phase in the spatial light modulator 2, so that a high-resolution focal scattering vector vortex light beam with a spatially varying polarization state can be generated behind the scattering medium (4), and by changing the focal coefficient a and the topological charge n, a high-resolution focal scattering vector vortex light field of the target focal scattering and vortex intensity is obtained.

[0018] Further, a high-resolution scattering vector vortex light field is generated behind the scattering medium (4), and the vectorial focusing effect is improved by nearly 10 times compared with the traditional lens focusing.

[0019] Further, by adding the angular phase The high-resolution focal scattering vector vortex light field with the change of the angular polarization state can be generated behind the scattering medium (4), and the modulation function of the spatial light modulator (2) is represented by the following formula four:

[0020] (Formula four)

[0021] wherein, , n represents the vortex topological charge, and m represents the angular topological charge.

[0022] Further, the scattering medium (4) is the isotropic ground glass with 220 grit.

[0023] Beneficial effects:

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The high-resolution focal scattering vector vortex light field can be generated behind the scattering medium, and the vector focusing effect is improved by nearly 10 times compared with the traditional lens focusing.

[0026] High flexibility, suitable for the field of generating high-resolution focal scattering vector vortex light field with arbitrary phase or polarization state behind the scattering medium, and stable structure;

[0027] The target focal scattering vector vortex light field can be generated by controlling the focal scattering and vortex phase, not only the vector optical transfer matrix can be quickly calculated, but also the target focal scattering vector vortex light field with high resolution can be generated behind the scattering medium, in addition, the high-resolution focal scattering vector vortex light field with the change of the angular polarization state can be generated by adding the angular phase, which has the characteristics of convenient operation, flexible control, high light field resolution, stable effect, etc. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a structure schematic view of a high-resolution focal scattering vector vortex light field generation system based on scattering focusing;

[0029] Figure 2 It is a schematic view of the focal scattering vector vortex light beams with different parameters generated by the system without passing through the scattering medium;

[0030] Figure 3 It is a schematic view of the high-resolution focal scattering vector vortex light beams with different parameters generated by the system after passing through the scattering medium;

[0031] Figure 4 It is a comparison diagram of the focusing effect of the focal scattering vector vortex light beams obtained by the traditional lens focusing and the high-resolution focal scattering vector vortex light beams generated by the system behind the scattering medium;

[0032] Figure 5 The schematic diagram of the light beam generated by the system after additional angular phase is attached in the caustic vector vortex light beam and passing through the scattering medium.

[0033] Reference signs:

[0034] 4f system 1, spatial light modulator 2, microscope objective 3, scattering medium 4, microscope objective 5, CMOS receiver 6. DETAILED DESCRIPTION

[0035] In order to better illustrate the content of the present application, the following will be described in conjunction with the drawings and examples:

[0036] As shown in Figures 1-5 , a high-resolution caustic vector vortex light field generation system based on scattering focusing includes a 4f system 1 generating a caustic vector vortex light field under the control of a control device, a microscope objective 3 converging the target, a scattering medium 4, a microscope objective 5 amplifying the target, a CMOS receiver 6 and a control device (such as Figure 1 the computer on the right side in ), wherein the 4f system contains a spatial light modulator 2 modulating the phase, the scattering medium 4 is preferably isotropic ground glass with 220 grit, the microscope objective converging the target, the microscope objective amplifying the target.

[0037] Further, as shown in Figure 1 , the 4f system specifically includes a spatial light modulator 2 modulating the phase and two Fourier lenses (not shown) integrated together, a double-hole filter (not shown), a double-coupling wave plate (not shown) and a Ronchi grating (not shown), the double-hole filter extracts the +1 order beams on the x-axis and y-axis of the spectral plane after the spatial light modulator 2 reflects, and makes the two beams pass through the different coupling surfaces of the double-coupling wave plate to convert into left-handed and right-handed circularly polarized light, and then the left-handed and right-handed circularly polarized light is superimposed in the same line by the Ronchi grating to generate a target vector light beam, and the input light field with different polarization and phase distribution depends on the hologram loaded on the SLM.

[0038] Further, different holographic phase patterns are loaded in the spatial light modulator 2 to achieve the effect of phase modulation on the input light field, and the generated caustic vector vortex light field is represented as follows:

[0039] (Formula 1)

[0040] Where A0 represents the amplitude, , n represents the vortex topological charge, a represents the caustic coefficient, , represents the wavelength, denotes the polar radius in the polar coordinate system, denotes the initial phase, , , and are the additional phases in the x and y directions loaded into the spatial light modulator 2, the focal caustic vector vortex light field is mainly determined by the focal caustic coefficient a and the vortex coefficient n, that is, by adjusting the focal caustic coefficient and the vortex coefficient and other parameters, the focal caustic vector vortex light field with the corresponding focal caustic intensity and target vortex phase can be obtained.

[0041] Further, the vector light field obtained by the coherent superposition of two orthogonal circularly polarized lights passing through the scattering medium 4 is expressed as the following formula two:

[0042] (Formula two)

[0043] Where m, n, p, q respectively represent the input plane (m, n) point and the output plane (p, q) point, the vector light beam is focused on the scattering medium 4 through the microscope objective 3, and then collected by the microscope objective 5 and transmitted to the CMOS receiver 6 in the form of speckle intensity diagram, taking each column of the Hadamard matrix as the input mode, the four-step phase shift method is used to measure the corresponding input mode calibration elements, so as to obtain all components of the vector transmission matrix (VTM) of the scattering medium 4.

[0044] Further, the conjugate operation is performed on the VTM as a whole, and the obtained modulation wavefront phase is loaded into the spatial light modulator 2 to overcome the scattering effect, and the modulation function of the two-dimensional holographic grating is expressed as the following formula three:

[0045] (Formula three)

[0046] Where represents the spatial carrier frequency, represents the modulation depth, and respectively represent the phase distribution carried by the left-handed and right-handed circularly polarized bases, and then the phase distribution of the target focal caustic vector vortex light field is added to the modulation wavefront phase in the spatial light modulator 2, so as to generate a high-resolution focal caustic vector vortex light beam with spatially varying polarization state behind the scattering medium 4, by changing the focal caustic coefficient a and the vortex topological charge n, a high-resolution focal caustic vector vortex light field with target focal caustic and vortex intensity can be obtained.

[0047] Further, a high-resolution focal caustic vector vortex light field is generated behind the scattering medium 4, and the vector focusing effect is improved by nearly 10 times compared with the traditional lens focusing.

[0048] Further, by adding the angular phase in the holographic phase diagram of the spatial light modulator 2 A high-resolution focal scattering vector vortex light field with an angular polarization state change can be generated behind the scattering medium 4, and the modulation function of the spatial light modulator 2 is expressed as the following formula four:

[0049] (Formula Four)

[0050] wherein , m is the angular topological charge.

[0051] Specifically, the light source is a laser source with a wavelength of 532 nm, and a high-resolution focal scattering vector vortex light field generation system based on scattering focusing can generate a target focal scattering vector vortex light field and calculate the vector optical transfer matrix, and then use the vector transfer matrix to generate a high-resolution focal scattering vector vortex light field behind the scattering medium 4.

[0052] Figure 2 The system generates focal scattering vector vortex beams with different vortex topological charges.

[0053] Figure 3 The system can generate high-resolution focal scattering vector vortex beams with different vortex topological charges behind the scattering medium 4.

[0054] Figure 4 The system generates high-resolution focal scattering vector vortex light fields behind the scattering medium 4, and the vector focusing effect is improved by nearly 10 times compared with the traditional lens focusing effect.

[0055] Figure 5 The system can generate high-resolution focal scattering vector vortex beams with different vortex topological charges behind the scattering medium 4.

[0056] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the technical solutions of the present application have been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part 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 the embodiments of the present application.

Claims

1. A high-resolution focal-converted vector vortex light field generation system based on scattering focusing, characterized in that: The system includes a laser generator, a 4f system (1) that generates a vector light field based on the superposition of two orthogonally circularly polarized beams, a microscope objective (3) for focusing the target, a scattering medium (4), a microscope objective (5) for magnifying the target, a CMOS receiver (6), and a control device. The 4f system (1) includes a spatial light modulator (2) for phase modulation, the microscope objective for focusing the energy of the incident light to penetrate the scattering medium (4), and the microscope objective for magnifying the target to collect the scattered signal after passing through the scattering medium (4). The 4f system (1) includes a spatial light modulator (2) for phase modulation, two Fourier lenses, a dual-aperture filter, and a double cemented carbide filter. The system consists of a waveplate and a Ronchi grating. A dual-aperture filter is used to extract the +1 order beams on the x-axis and y-axis of the spatial light modulator (2) after reflection. The two beams are then passed through a double cemented plate. Different cemented surfaces of the waveplate are converted into left-handed and right-handed circularly polarized light. The left-handed and right-handed circularly polarized light are then superimposed collinearly through a Ronchi grating to generate a target vector beam. The input light field with different polarization and phase distribution depends on the hologram loaded on the spatial light modulator (2). The generated caustic vector vortex optical field is shown in the following formula one by phase modulation based on 4f system (1): (Formula One); Where A0 represents the amplitude. , , , , where n represents the vortex topological charge number and a represents the caustic coefficient. , Indicates wavelength. Represents the polar radius in polar coordinates. Indicates the initial phase. and These are the additional phases loaded into the spatial light modulator (2) in the x and y directions, respectively. The caustic vector vortex light field is mainly composed of... and caustic phase term in With vortex phase term The determination is made by adjusting the parameters of the caustic coefficient 'a' and the vortex topological charge 'n' to obtain the caustic vector vortex light field with the corresponding caustic intensity and the phase of the target vortex.

2. A high-resolution focal-converted vector vortex light field generation system based on scattering focusing according to claim 1, characterized in that: The vector transmission matrix (VTM) of the vector optical field obtained by the coherent superposition of two orthogonal circularly polarized lights passing through the scattering medium (4) is shown in the following formula two: (Formula Two); Where m, n, p, q represent the input plane (m, n) point and the output plane (p, q) point respectively, the vector beam is focused on the scattering medium (4) through the microscope objective (3) converging on the target, then collected by the microscope objective (5) amplifying the target and transmitted to the CMOS receiver (6) in the form of speckle intensity diagram, taking each column of Hadamard matrix as input mode, the whole components of the vector transmission matrix (VTM) of the scattering medium (4) are obtained according to the four-step phase shift method and by measuring the corresponding input mode calibration elements.

3. A scattering focusing based high-resolution focal- vector vortex light field generation system according to claim 2, characterized in that: The modulation wavefront phase obtained by the conjugate operation of the whole vector transmission matrix (VTM) is loaded to the spatial light modulator (2) to overcome the scattering effect, and the modulation function of the spatial light modulator (2) is shown in the following formula three: (Formula Three); wherein denotes the modulation depth, denotes the spatial carrier frequency, , n denotes the topological charge of the vortex, a denotes the caustic coefficient, , denotes the wavelength, denotes the polar radius in the polar coordinate system, denotes the initial phase, and denotes the phase distribution carried by the left-handed and right-handed circularly polarized bases, and the phase distribution of the target caustic vector vortex light field is added to the modulation wavefront phase in the spatial light modulator 2, so that a high-resolution caustic vector vortex light beam with a spatially varying polarization state can be generated behind the scattering medium (4), and by changing the caustic coefficient a and the topological charge n, a high-resolution caustic vector vortex light field with target caustic and vortex intensity is obtained.

4. A scattering-focused based high-resolution focal- vector vortex light field generation system according to claim 3, characterized in that: By adding an angular phase in the holographic phase map of the spatial light modulator (2) A high-resolution focal vector vortex light field with an angular polarization state change can be generated behind the scattering medium (4), and the modulation function of the spatial light modulator (2) is represented as the following formula four: (Formula Four); wherein , , n represents a vortex topological charge number, and m represents an angular topological charge number.

5. The scattering-focused high-resolution focal- vector vortex light field generation system according to claim 1, wherein: The scattering medium (4) is isotropic ground glass with 220 grit.

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