A nonlinear transmission matrix measurement device and method

Abstract

The application relates to the field of nonlinear optics and discloses a nonlinear transmission matrix measuring device and method, which comprise a first laser, a first half-wave plate, a first convex lens, a second convex lens, a first reflector, a second laser, a second half-wave plate, a third convex lens, a fourth convex lens, a spatial light modulator, a second reflector, a first dichroic mirror, a second dichroic mirror, an objective lens, a second-order nonlinear scattering medium, a third reflector, a filter, a fifth convex lens and a CCD camera. The application generalizes the traditional transmission matrix method from linear optics to the field of nonlinear optics, realizes accurate solving and measuring of a transmission matrix between a fundamental frequency light field incident into a scattering medium and an emitted nonlinear scattering light field, and realizes arbitrary regulation and control of nonlinear harmonics through the nonlinear transmission matrix. Compared with a feedback algorithm, the nonlinear transmission matrix method can reduce time consumption and realize quick switching of different regulation and control requirements.

Description

Technical Field

[0001] This invention relates to the field of nonlinear optics, and more particularly to a nonlinear transfer matrix measurement device and method. Background Technology

[0002] When light encounters a complex medium with a non-uniform refractive index during propagation, photons interact with particles in the medium, causing distortions in the light's temporal, spatial, polarization, and spectral properties. Furthermore, the light's propagation direction deviates, and it propagates randomly in various directions, resulting in light scattering. Such complex media are called scattering media, which are highly detrimental to optical imaging and optical information transmission. Therefore, researching how to overcome the scattering effects of scattering media to achieve optical imaging through them is of great significance.

[0003] Currently, there are two main methods for overcoming light scattering. One is the feedback wavefront shaping method, which requires iterative optimization based on the feedback signal from the target point. However, this method requires a large amount of data and iterations, consuming significant computational power and time. The other method is the optical transfer matrix method. The transformation relationship between the incident and emitted light in the scattering medium can be characterized by the transfer matrix of the scattering medium. The information contained in the transfer matrix allows for arbitrary manipulation of the emitted light from the scattering medium and reconstruction of arbitrary images. Furthermore, the transfer matrix method can significantly reduce the computation time for wavefront optimization.

[0004] However, current transfer matrix methods are primarily used to describe linear scattering processes, while nonlinear signals are also extremely important, currently widely applied in fields such as biosensing, nonlinear imaging, and optical communication. Extending the transfer matrix method to the realm of nonlinear optics can provide a novel approach for studying the physical properties and mechanisms of nonlinear scattering media. Furthermore, similar to linear transfer matrices, the information contained in nonlinear transfer matrices allows for arbitrary manipulation of nonlinear signals generated in the medium, which is of paramount importance for future nonlinear imaging and quantum information processing in complex environments.

[0005] Therefore, those skilled in the art are dedicated to developing a measuring device capable of accurately measuring the nonlinear transmission matrix of a nonlinear scattering medium. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to realize the accurate solution and measurement of the transmission matrix between the fundamental frequency light field incident on the scattering medium and the outgoing nonlinear scattered light field.

[0007] To achieve the above objectives, the present invention provides a measuring device for a nonlinear optical transfer matrix of a scattering medium, comprising: a nonlinear optical transfer matrix measuring device, characterized in that it includes: a first laser 1, a first half-wave plate 2, a first convex lens 3, a second convex lens 4, a first reflecting mirror 5, a second laser 6, a second half-wave plate 7, a third convex lens 8, a fourth convex lens 9, a spatial light modulator 10, a second reflecting mirror 11, a first dichroic mirror 12, a second dichroic mirror 13, an objective lens 14, a second-order nonlinear scattering medium 15, a third reflecting mirror 16, a filter 17, a fifth convex lens 18, and a CCD camera 19.

[0008] In a preferred embodiment of the present invention, the first laser 1 outputs a first linearly polarized laser beam, the polarization direction of the first linearly polarized laser beam is adjusted by a first half-wave plate 2, and the beam waist radius of the first linearly polarized laser beam is enlarged by a beam expanding system composed of a first convex lens 3 and a second convex lens 4; simultaneously, the second laser 6 outputs a second linearly polarized laser beam, the polarization direction of the second linearly polarized laser beam is adjusted by a second half-wave plate 7, and the beam waist radius of the second linearly polarized laser beam is enlarged by a beam expanding system composed of a third convex lens 8 and a fourth convex lens 9; subsequently, the second linearly polarized laser beam is incident on the spatial light modulator 10. The light beam, modulated by the spatial light modulator 10, is reflected by the second mirror 11, then combined with the first linearly polarized laser beam after passing through the first dichroic mirror 12. The combined laser beam then passes through the second dichroic mirror 13 and is focused onto the second-order nonlinear scattering medium 15 by the objective lens 14. The sum-frequency light signal generated by the second-order nonlinear scattering medium 15 is collected by the objective lens 14, reflected by the second dichroic mirror 13 and the third mirror 16, filtered by the filter 17 to remove the fundamental frequency light, and then focused onto the CCD camera 19 by the fifth convex lens 18. The CCD camera 19 records the sum-frequency light intensity distribution under different Hadamard arrays.

[0009] Preferably, the output beams of the first laser 1 and the second laser 2 are fundamental mode narrow linewidth energy-stable lasers.

[0010] Preferably, the spatial light modulator 10 is an amplitude-type or phase-type spatial light modulator.

[0011] Preferably, the second-order nonlinear scattering medium 15 is a scattering medium with second-order nonlinear effects, including but not limited to lithium niobate powder, potassium dihydrogen phosphate powder, and barium metaborate powder.

[0012] Preferably, the filter 17 is a short-pass filter used to filter out fundamental frequency light.

[0013] Preferably, the second dichroic mirror 13 transmits fundamental frequency light and reflects sum frequency light.

[0014] Preferably, the CCD camera 19 is responsive to nonlinear signals.

[0015] The present invention also provides a method for measuring a nonlinear optical transfer matrix, utilizing the aforementioned nonlinear optical transfer matrix measuring device, the method comprising the following steps:

[0016] The first linearly polarized laser beam emitted from the first laser 1 is not modulated. The second linearly polarized laser beam emitted from the second laser 6 is incident on the spatial light modulator 10 and split into two parts: modulation light and reference light. The modulation light is the light field that coincides with the phase diagram of the spatial light modulation and is divided into N incident channels. The remaining unmodulated light field in the periphery serves as the reference light. The output sum-frequency light signal is divided into M output channels. The sum-frequency light field of the m-th output channel... With the first linearly polarized laser beam E in (ω1) and the second linearly polarized laser beam of the nth incident channel The relationship between them is:

[0017]

[0018] in: K represents the nonlinear transfer matrix connecting the nth input channel and the mth output channel. NL Element;

[0019] For the sum-frequency optical field of the m-th output channel, the optical field intensity It can be represented as:

[0020]

[0021] Where α represents the phase shift constant applied by the spatial light modulator to all incident second linearly polarized laser beams, α takes values ​​of 0, π / 2, π, and 3π / 2, Re() represents taking the real part of the parameter within parentheses, and s m Indicates the first linearly polarized laser beam and the second linearly polarized laser beam. The reference portion generates the sum-frequency optical field in the m-th output channel in a nonlinear scattering medium. s m Hermitian conjugate. Further, the following relation can be obtained:

[0022]

[0023] Using the above equation, combined with a second linearly polarized laser beam E modulated by different basis vectors... in (ω2) and the corresponding output light field I out The nonlinear transfer matrix K of the scattering medium can be solved using (ω1+ω2). NL .

[0024] Preferably, according to the digital phase conjugate formula It can realize nonlinear signal wavefront modulation to verify the accuracy of the measured nonlinear transmission matrix.

[0025] The beneficial effects of this invention are:

[0026] This invention extends the traditional transfer matrix method from linear optics to the field of nonlinear optics, enabling the precise solution and measurement of the transfer matrix between the fundamental light field incident on the scattering medium and the outgoing nonlinear scattered light field. The nonlinear transfer matrix allows for arbitrary manipulation of nonlinear harmonics. Compared to feedback algorithms, the nonlinear transfer matrix method reduces time consumption and enables rapid switching between different manipulation requirements. It has significant application value in future nonlinear imaging and quantum information processing in complex environments.

[0027] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an optical path device for measuring a nonlinear transmission matrix according to an embodiment of the present invention;

[0029] Figure 2 These are different sum-frequency light intensity distribution diagrams generated when different hadamards are loaded according to embodiments of the present invention;

[0030] Figure 3 This is an amplitude and phase distribution diagram of the measured values ​​of the nonlinear transmission matrix according to an embodiment of the present invention;

[0031] Figure 4 The embodiments of the present invention are experimental results of focusing nonlinear scattered light using nonlinear transmission matrix measurements, showing the output light field diagrams of focusing achieved and unfocused light. Detailed Implementation

[0032] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0033] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0034] refer to Figures 1-4 In a preferred embodiment of the present invention, such as Figure 1As shown, a measurement device for a nonlinear optical transfer matrix of a scattering medium includes: a first laser 1, a first half-wave plate 2, a first convex lens 3, a second convex lens 4, a first reflector 5, a second laser 6, a second half-wave plate 7, a third convex lens 8, a fourth convex lens 9, a spatial light modulator 10, a second reflector 11, a first dichroic mirror 12, a second dichroic mirror 13, an objective lens 14, a second-order nonlinear scattering medium 15, a third reflector 16, a filter 17, a fifth convex lens 18, and a CCD camera 19. A first linearly polarized laser beam with a wavelength of 780nm is output from the first laser 1. The polarization direction of the first linearly polarized laser beam is adjusted by the first half-wave plate 2, and then the beam waist radius of the laser beam is enlarged by a beam expanding system composed of the first convex lens 3 and the second convex lens 4. Simultaneously, a second linearly polarized laser beam with a wavelength of 1064nm is output from the second laser 2. The polarization direction of the second linearly polarized laser beam is adjusted by the second half-wave plate 7, and then the beam waist radius of the second linearly polarized laser beam is enlarged by a beam expanding system composed of the third convex lens 8 and the fourth convex lens 9. Subsequently, the 1064nm second linearly polarized laser beam is incident on the liquid crystal spatial light modulator 10. The 40×40 pixels on the spatial light modulator 10 are merged into one superpixel, containing a total of 16×16 superpixels, and using different... The Hadamardi beam modulates the second linearly polarized beam. The modulated 1064nm second linearly polarized beam is reflected by the second mirror 11 and then combined with the 780nm first linearly polarized laser beam by the first dichroic mirror 12. The combined laser beam then passes through the second dichroic mirror 13 and is focused by the objective lens 14 onto the second-order scattering medium 15 of lithium niobate powder. The sum-frequency light signal generated by the second-order scattering medium 15 is collected by the objective lens 14, reflected by the second dichroic mirror 13 and the third mirror 16, and then filtered by the filter 17 to remove the fundamental frequency light. Finally, it is focused by the fifth convex lens 18 onto the CCD camera 19 to record the sum-frequency light intensity distribution under different Hadamardi beams. The 3×3 pixels of the CCD camera 19 are merged into one superpixel, and a total of 16×16 superpixels are included. Figure 2 Different hadamards and their corresponding sum-frequency intensity distributions are shown.

[0035] In another preferred embodiment of the present invention, a method for measuring a nonlinear transfer matrix is ​​also provided as follows:

[0036] The incident second linearly polarized laser beam with an incident wavelength of 1064 nm is split into a reference beam and a modulation beam. The modulation beam is the light field that coincides with the phase diagram on the spatial light modulation 10, and is divided into N = 256 incident channels. The remaining unmodulated peripheral light field serves as the reference beam. The output sum-frequency light signal with a wavelength of 450 nm is divided into M = 256 output channels. The sum-frequency light field of the m-th output channel... With the 780nm first linearly polarized laser beam E in(ω1) and the 1064nm second linearly polarized laser beam from the nth incident channel The relationship between them is:

[0037]

[0038] in, K represents the nonlinear transfer matrix connecting the nth input channel and the mth output channel. NL Element.

[0039] For the sum-frequency optical field of the m-th output channel, its optical field intensity The calculation expression is:

[0040]

[0041] Where α represents the phase shift constant applied by the spatial light modulator 10 to all incident 1064nm second linearly polarized laser beams, Re() represents taking the real part of the parameter in parentheses, and s m This represents the sum-frequency optical field generated by the m-th output channel of the reference portions of the first and second linearly polarized laser beams in the nonlinear scattering medium. s m The Hermitian conjugate. The sum-frequency signal intensity of the m-th output channel when α takes the values ​​of 0, π / 2, π, and 3π / 2. and They are respectively:

[0042]

[0043] By combining the above four formulas, we can further obtain the following formula:

[0044]

[0045] Using the above equation, combined with the input second linearly polarized laser beam E modulated by different basis vectors... in (ω2) and the corresponding output light field I out The nonlinear transfer matrix K of the scattering medium can be solved using (ω1+ω2). NL The calculated transmission matrix K NL Given a complex matrix, its elements Let be a complex number connecting the nth input channel and the mth output channel. The measured amplitude and phase distributions of the nonlinear transfer matrix are as follows: Figure 3 As shown. By utilizing the measured nonlinear transmission matrix combined with the digital phase conjugation method, the target nonlinear output field E can be manipulated to control the output nonlinear optical signal. target The expression for the optical field of the incident 1064nm second linearly polarized laser beam corresponding to (ω1+ω2) is:

[0046]

[0047] In the formula, For K NL The transpose and conjugate of .

[0048] The nonlinear sum-frequency optical field output by the nonlinear scattering medium without modulation, such as Figure 4 As shown in (a), the nonlinear scattering signal is focused after modulation using a nonlinear transfer matrix combined with the digital phase conjugation method. Figure 4 As shown in (b).

[0049] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A nonlinear optical transfer matrix measurement device, characterized in that, include: First laser (1), first half-wave plate (2), first convex lens (3), second convex lens (4), first mirror (5), second laser (6), second half-wave plate (7), third convex lens (8), fourth convex lens (9), spatial light modulator (10), second mirror (11), first dichroic mirror (12), second dichroic mirror (13), objective lens (14), second-order nonlinear scattering medium (15), third mirror (16), filter (17), fifth convex lens (18), and CCD camera (19); The first laser (1) outputs a first linearly polarized laser beam. The polarization direction of the first linearly polarized laser beam is adjusted by a first half-wave plate (2), and then the beam waist radius of the first linearly polarized laser beam is enlarged by a beam expanding system composed of a first convex lens (3) and a second convex lens (4). At the same time, the second laser (6) outputs a second linearly polarized laser beam. The polarization direction of the second linearly polarized laser beam is adjusted by a second half-wave plate (7), and then the beam waist radius of the second linearly polarized laser beam is enlarged by a beam expanding system composed of a third convex lens (8) and a fourth convex lens (9). Subsequently, the second linearly polarized laser beam is incident on a spatial light modulator (10) and is controlled by the spatial light modulator (10). 10) After modulation, the light is reflected by the second mirror (11), and then combined with the first linearly polarized laser beam after passing through the first dichroic mirror (12). The combined laser beam then passes through the second dichroic mirror (13), and the objective lens (14) focuses the combined laser beam onto the second-order nonlinear scattering medium (15). The sum-frequency light signal generated by the second-order nonlinear scattering medium (15) is collected by the objective lens (14), and after being reflected by the second dichroic mirror (13) and the third mirror (16), the fundamental frequency light is filtered out by the filter (17), and then focused onto the CCD camera (19) by the fifth convex lens (18). The CCD camera (19) records the sum-frequency light intensity distribution under different Hadamard bases.

2. The nonlinear optical transfer matrix measurement device as described in claim 1, characterized in that, The output beams of the first laser (1) and the second laser (6) are fundamental mode narrow linewidth energy-stable lasers.

3. The nonlinear optical transfer matrix measurement device as described in claim 1, characterized in that, The spatial light modulator (10) is an amplitude-type or phase-type spatial light modulator.

4. The nonlinear optical transfer matrix measurement device as described in claim 1, characterized in that, The second-order nonlinear scattering medium (15) is a scattering medium with second-order nonlinear effects, including lithium niobate powder, potassium dihydrogen phosphate powder and barium metaborate powder.

5. The nonlinear optical transfer matrix measurement device as described in claim 1, characterized in that, The filter (17) is a short-pass filter used to filter out fundamental frequency light.

6. The nonlinear optical transfer matrix measurement device as described in claim 1, characterized in that, The second dichroic mirror (13) transmits fundamental frequency light and reflects sum frequency light.

7. The nonlinear optical transfer matrix measurement device as described in claim 1, characterized in that, The CCD camera (19) is responsive to nonlinear signals.

8. A method for measuring a nonlinear optical transfer matrix, characterized in that, The method, using the nonlinear optical transfer matrix measurement device as described in claim 1, includes the following steps: The first linearly polarized laser beam emitted from the first laser (1) is not modulated. The second linearly polarized laser beam emitted from the second laser (6) is incident on the spatial light modulator (10) and is divided into two parts: modulation light and reference light. The modulation light is the light field that coincides with the phase diagram of the spatial light modulation and is divided into N incident channels. The remaining unmodulated light fields are the reference light. The output sum-frequency light signal is divided into M output channels, and the frequency of the m-th output channel is... sum frequency light field With frequency First linearly polarized laser beam The frequency of the nth incident channel is The second linearly polarized laser beam The relationship between them is: in: K represents the nonlinear transfer matrix connecting the nth input channel and the mth output channel. NL Element; For the sum-frequency optical field of the m-th output channel, the optical field intensity It can be represented as: Where α represents the phase shift constant applied by the spatial light modulator to all incident second linearly polarized laser beams, and α takes values ​​of 0, π / 2, π, and 3π / 2, respectively. Re() denotes taking the real part of the parameter within the parentheses. Indicates the first linearly polarized laser beam and the second linearly polarized laser beam. The reference portion generates the sum-frequency optical field in the m-th output channel in a nonlinear scattering medium. express The Hermitian conjugate can be further expressed by the following relationship: Using the above formula, a second linearly polarized laser beam modulated by different basis vectors is obtained. and the corresponding output light field The nonlinear transfer matrix of the scattering medium can be solved. K NL .

9. The nonlinear optical transfer matrix measurement method as described in claim 8, characterized in that, According to the digital phase conjugate formula This allows for the manipulation of nonlinear signal wavefronts to verify the accuracy of the measured nonlinear transmission matrix. for The transpose and conjugate of , Indicates frequency as The target nonlinear output field is manipulated.

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