Method and device for preparing dynamic surface plasmon bottle array

Abstract

The invention relates to a method and a device for preparing a dynamic surface plasmon bottle array. The preparation method comprises the following steps: modulating a light beam into a Pearls Talbot light beam; and irradiating the Pearls-like Talbot beam to a slit-coupled exciter, so that the exciter excites the surface plasmon to obtain a surface plasmon bottle array. Compared with an existing surface plasmon bottle preparation method, the method has the advantages that a bottle array with multiple pore arrays can be generated, multiple particle swarms can be captured and controlled at the same time, and the method is suitable for high-throughput experiment scenes. According to the invention, the limitation of diffraction limit is broken through by using the surface plasmon effect, and smaller-scale particle capture and control capability is obtained compared with the traditional light bottle array technology. According to the invention, the structure and intensity arrangement of the surface plasmon bottle array can be dynamically regulated and controlled only by changing the parameters for modulating the Pearls-like Talbot beam, the physical structure of the grating coupler does not need to be changed, the regulation and control flexibility is high, and the cost is extremely low.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to a method and device for preparing a dynamic surface plasmon bottle array. Background Art

[0002] This section is intended to provide a background or context for the embodiments of the invention described herein. No description herein is admitted to be prior art by virtue of its inclusion in this section.

[0003] In 1986, the introduction of "optical tweezers", a light beam that can capture and manipulate particles, opened the door to capturing particles with light beams. Optical tweezers use the gradient force of light. Under different conditions, light will exert a thrust or suction on objects. By modulating the light, particles can be confined to the focal point of the light, thereby capturing and manipulating particles. However, optical tweezers have the limitation that they can only capture a single particle, which limits the use of optical tweezers. Subsequently, the "light bottle" structure that can capture and manipulate multiple particles at the same time was proposed. The "light bottle" structure is also based on the action of gradient forces. By imprisoning particles in a low potential energy area surrounded by a high potential energy area (i.e., the bottle body), it can achieve the simultaneous capture and manipulation of multiple particles. The "light bottle array" is a system composed of multiple light bottles that can capture and manipulate multiple particle groups at the same time. It is suitable for scenarios where multiple particles need to be manipulated simultaneously, such as high-throughput biological experiments and complex physical and chemical research.

[0004] Surface plasmon is an optical phenomenon that occurs at the interface between metal and dielectric. When light waves are incident on the metal surface, the free electrons on the metal surface oscillate collectively; the light waves couple with the free electrons on the metal surface to form a near-field electromagnetic wave that propagates along the metal surface; if the oscillation frequency of the free electrons is consistent with the frequency of the light waves, resonance will occur, causing the near-field electromagnetic wave formed by the coupling of the light waves and the free electrons to present a special electromagnetic mode in which the electromagnetic field is confined to a very small range on the metal surface and is enhanced. This phenomenon is called surface plasmon. Using the surface plasmon phenomenon, a strong localized electromagnetic field can be generated near the nanostructure on the metal surface to form a light potential well; multiple light potential wells are arranged in an array to obtain a light bottle array.

[0005] However, the existing method for generating optical bottle arrays based on the surface plasmon effect relies on a Bessel light source with a simple phase distribution and a mechanically adjusted grating coupling structure. It is not only unable to dynamically control the bottle array structure, but also unable to adjust the partial intensity distribution and self-bending propagation characteristics of the bottle array, and has low control flexibility. Summary of the invention

[0006] Based on this, the object of the present invention is to provide a method and device for preparing a dynamic surface plasmon bottle array, which has the advantage of being flexible and controllable.

[0007] The present invention provides a method for preparing a dynamic surface plasmon bottle array, which comprises the steps of: modulating a light beam into a Pierce-Talbot beam; irradiating the Pierce-Talbot beam onto a slit-coupled exciter, so that the exciter excites surface plasmons, and obtaining a surface plasmon bottle array.

[0008] Compared with the existing surface plasmon bottle preparation method, the present invention can produce a bottle array with multiple aperture arrays, which can capture and manipulate multiple particle groups at the same time, and is suitable for high-throughput experimental scenarios. The present invention uses the surface plasmon effect to break through the limitations of the diffraction limit and achieves smaller-scale particle capture and manipulation capabilities than traditional optical bottle array technology. The present invention only needs to change the parameters of the modulated Pierce-Talbot beam to dynamically control the structure and intensity arrangement of the surface plasmon bottle array, without changing the physical structure of the grating coupler. It has strong control flexibility and extremely low cost, and is highly cost-effective.

[0009] Furthermore, after the light beam is modulated into a Pierce-Talbot beam, the method further includes the step of: performing spatial filtering on the Pierce-Talbot beam to obtain a Pierce-Talbot beam having only phase information.

[0010] Furthermore, the formula for the initial field complex amplitude of the Pierce-Talbot beam is:

[0011]

[0012] In the formula, is the Pierce function, n is the number of superimposed Pierce plasmons, c n is the superposition coefficient, w0 is the beam width, b and p are distribution factors, δ is the displacement factor, and a0 is the Gaussian attenuation factor.

[0013] Furthermore, the Pierce function variant in the initial field complex amplitude formula of the Pierce-like Talbot beam is:

[0014]

[0015] Based on the same inventive concept, the present invention also provides a dynamic surface plasmon bottle array preparation device for executing the above-mentioned preparation method, which includes: a laser, a spatial light modulator and an exciter; the laser generates a light beam; the spatial light modulator modulates the light beam into a Pierce-Talbot beam; the exciter is a slit-coupled exciter, which excites surface plasmons after being irradiated by the Pierce-Talbot beam to obtain a surface plasmon bottle array.

[0016] Furthermore, the exciter is a silver layer etched with nano-slits.

[0017] Furthermore, it also includes a spatial filtering module, which performs spatial filtering on the Pierce-Talbot beam to obtain a Pierce-Talbot beam with only phase information, and then irradiates the Pierce-Talbot beam with only phase information to the exciter.

[0018] Furthermore, the spatial filtering module specifically includes: a first lens, an adjustable aperture and a second lens which are sequentially arranged on the optical path of a Pierce-like Talbot beam; the first lens and the second lens are Fourier lenses with the same focal length, and the focal lengths of the first lens and the second lens are denoted as f, and the distance between the first lens and the second lens is 2f; the adjustable aperture is arranged exactly in the middle of the first lens and the second lens; the adjustable aperture only allows the positive first-order diffraction fringes of the Pierce-like Talbot beam to pass through, thereby obtaining a Pierce-like Talbot beam having only phase information.

[0019] Furthermore, it also includes a beam expander and a beam splitter which are sequentially arranged on the optical path of the light beam generated by the laser; the beam expander expands and collimates the light beam generated by the laser; the beam splitter splits the expanded and collimated light beam into a first light beam and a second light beam, and allows the first light beam to irradiate the spatial light modulator.

[0020] Furthermore, it also includes a reflector arranged on the optical path of the Pierce-Talbot beam; the reflector changes the propagation direction of the Pierce-Talbot beam with only phase information so that it irradiates the exciter.

[0021] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a module of a dynamic surface plasmon bottle array preparation device of the present invention;

[0023] Figure 2 A schematic diagram of the optical path of the dynamic surface plasmon bottle array preparation device of the present invention;

[0024] Figure 3 A schematic diagram of the structure of an exciter of a dynamic surface plasmon bottle array preparation device of the present invention;

[0025] Figure 4 It is a schematic diagram of the process of preparing the dynamic surface plasmon bottle array of the present invention;

[0026] Figure 5 A propagation diagram of a surface plasmon bottle array with adjustable overall structural distribution generated by the present invention;

[0027] Figure 6 A propagation diagram of a surface plasmon bottle array with adjustable intensity distribution generated by the present invention;

[0028] Figure 7 The propagation diagram of the surface plasmon bottle array with self-bending characteristics generated by the present invention;

[0029] Figure 8 This is a propagation diagram of a surface plasmon bottle array obtained by simulating the finite-difference time-domain method in the present invention. DETAILED DESCRIPTION

[0030] The existing light bottle array control methods either control the parameters of the light source at the front end of the system or change the grating coupling structure on the metal film at the end of the system. These methods do not support dynamic control and are not flexible. The inventors consider that the spatial light modulator (SLM) can change the phase or amplitude of light to generate a complex light field distribution. If the light wave is phase modulated by the spatial light modulator before it enters the surface plasmon exciter, the parameters of the surface plasmon bottle array can be dynamically controlled by the spatial light modulator to finally excite. Based on the above concept, the present invention generates a one-dimensional Pierce-like Talbot beam by controlling the phase mask of the spatial light modulator, and sets a nano-slit on the silver layer, so that the Pierce-like Talbot beam diffracts and scatters at the nano-slit, and excites the surface plasmon bottle array on the surface of the silver layer. The present invention can dynamically control the structure and intensity distribution of the surface plasmon bottle array by changing the phase mask of the spatial light modulator, so that multiple particle groups are integrally manipulated through the surface plasmon bottle array, which is suitable for high-throughput experimental scenarios.

[0031] See also Figure 1-3 , Figure 1 is a schematic diagram of a module of a dynamic surface plasmon bottle array preparation device of the present invention, Figure 2 Schematic diagram of the optical path of the dynamic surface plasmon bottle array preparation device of the present invention, Figure 3 It is a schematic structural diagram of an exciter of a dynamic surface plasmon bottle array preparation device of the present invention.

[0032] The dynamic surface plasmon bottle array preparation device of the present invention comprises: a laser 10 , a beam expander 20 , a beam splitter 30 , a spatial light modulator 40 , a spatial filter module 50 , a reflector 60 and an exciter 70 .

[0033] The laser 10 generates a light beam. The beam expander 20 and the beam splitter 30 are sequentially arranged on the optical path of the light beam generated by the laser. The beam expander 20 expands and collimates the light beam generated by the laser to obtain a collimated light beam. The beam splitter 30 splits the collimated light beam into a first light beam and a second light beam; the first light beam is at right angles to the collimated light beam and is irradiated to the spatial light modulator 40 for further processing; the second light beam is in the same direction as the collimated light beam and is emitted into the air and is discarded.

[0034] The spatial light modulator 40 is disposed on the optical path of the first light beam, modulates the phase of the first light beam, converts the first light beam into a modulated light beam as a Pierce-Talbot beam, and irradiates the first light beam to the beam splitter 30. The beam splitter 30 splits the modulated light beam into a third light beam and a fourth light beam; the third light beam is at a right angle to the modulated light beam and is emitted into the air and discarded; the fourth light beam has the same direction as the modulated light beam and is irradiated to the spatial filter module 50 for further processing.

[0035] The spatial filter module 50 and the reflector 60 are sequentially arranged on the optical path of the fourth light beam. The spatial filter module 50 performs spatial filtering on the fourth light beam, allowing only the positive first-order diffraction stripes of the fourth light beam to pass through, thereby obtaining a filtered light beam as a Pierce-like Talbot beam with only phase information. The reflector 60 changes the propagation direction of the filtered light beam so that the filtered light beam is incident on the exciter 70. Figure 3 The exciter 70 includes a stacked quartz substrate 71 and a silver layer 72. A nano-slit 721 is etched on the silver layer 72. When the filtered light beam enters the exciter 70, the filtered light beam is irradiated on the silver layer 72 through the quartz substrate 71, diffracted and scattered on the nano-slit 721 of the silver layer 72, and interacts with free electrons on the surface of the silver layer 72, thereby exciting a surface plasmon bottle array on the silver layer 72.

[0036] Specifically, the spatial light modulator 40 is electrically connected to a computer 41. The computer 41 generates a phase mask image for generating a corresponding Pierce-like Talbot beam according to the initial field complex amplitude formula of the Pierce-like Talbot beam. After obtaining the phase mask image generated by the computer 41, the spatial light modulator 40 modulates the first light beam according to the phase mask image, thereby converting the first light beam into a modulated light beam as a Pierce-like Talbot beam. The initial field complex amplitude formula of the Pierce-like Talbot beam is:

[0037]

[0038] In the formula, is the Pierce function, n is the number of superimposed Pierce plasmons, c n is the superposition coefficient, w0 is the beam width, b and p are both distribution factors, δ is the displacement factor, and a0 is the Gaussian attenuation factor. The physical quantity factors (i.e., n, c n ,w0,b,p,δ,a0) affect the structural distribution and intensity distribution of the final generated surface plasmon bottle array, as well as the self-bending propagation characteristics of the surface plasmon bottle array. For example, the displacement factor affects the self-imaging period of the final generated surface plasmon bottle array. The larger the displacement factor, the larger the self-imaging period. The distribution factor affects the size and number of individual bottle structures in the surface plasmon bottle array, thereby controlling the overall structure of the surface plasmon bottle array. Those skilled in the art can determine the specific values ​​of the physical quantity factors in the above-mentioned initial field complex amplitude formula of the Pierce-Talbot beam as needed.

[0039] Furthermore, in order to make the finally generated surface plasmon bottle array have the self-bending propagation characteristics, in some embodiments, the Pierce function in the initial field complex amplitude formula of the Pierce-like Talbot beam can be transformed. At this time, the Pierce function in the initial field complex amplitude formula of the Pierce-like Talbot beam becomes:

[0040]

[0041] Specifically, the beam splitter 30 is a beam splitting cubic crystal, which can split the input beam into a sub-beam with unchanged direction (corresponding to the second beam and the fourth beam) and a sub-beam rotated 90° clockwise in the original direction (corresponding to the first beam and the third beam). Figure 2 For ease of display and understanding, the optical paths are separated and represented, and the actual optical paths overlap in a cross shape, that is, the incident light (i.e., the first light beam) and the outgoing light (i.e., the modulated light beam) of the spatial light modulator 40 overlap, and the outgoing light beams below the beam splitter 30 (i.e., the second light beam and the third light beam) also overlap.

[0042] Specifically, Figure 1As shown, the spatial filtering module 50 includes: a first lens 51, an adjustable aperture 52, and a second lens 53 which are sequentially arranged on the optical path of the fourth light beam. The first lens 51 and the second lens 53 are Fourier lenses with the same focal length. It is not a problem to note that the focal lengths of the first lens 51 and the second lens 53 are f, and the distance between the first lens 51 and the second lens 53 is 2f; the adjustable aperture 52 is arranged in the middle of the first lens 51 and the second lens 53, and the distance between the first lens 51 and the second lens 53 is f. The adjustable aperture 52 only allows the positive first-order diffraction fringes of the fourth light beam to pass through, thereby obtaining a filtered light beam which is a Pierce-like Talbot beam with only phase information.

[0043] Furthermore, the device also includes an observation module 80, which is used to observe the surface plasmon bottle array excited by the surface of the silver layer 72. The observation module 80 specifically includes: a tapered optical fiber 81, and a near-field scanning optical microscope 82 electrically connected to the tapered optical fiber 81. The tapered optical fiber 81 collects the near-field optical signal generated by the surface plasmon bottle array on the surface of the silver layer 72, and transmits the near-field optical signal to the near-field scanning optical microscope 82. The near-field scanning optical microscope 82 generates a high-resolution image of the surface plasmon bottle array based on the near-field optical signal, thereby assisting in studying the structure and characteristics of the surface plasmon bottle array.

[0044] See also Figure 4 , Figure 4 The figure is a flow chart of the method for preparing a dynamic surface plasmon bottle array of the present invention. Based on the dynamic surface plasmon bottle array preparation device of the present invention, the method for preparing a dynamic surface plasmon bottle array of the present invention comprises the following steps: S0, generating a light beam by a laser 10; S1, modulating the light beam into a Pierce-like Talbot beam by a spatial light modulator 40; S2, irradiating the Pierce-like Talbot beam onto a slit-coupled exciter 70, so that the exciter 70 excites surface plasmons, and obtaining a surface plasmon bottle array.

[0045] Specifically, step S0 includes: S01, making the laser 10 generate a light beam, and then expanding and collimating the light beam generated by the laser through the beam expander 20; S02, splitting the expanded and collimated light beam into a first light beam and a second light beam through the beam splitter 30, and making the first light beam irradiate the spatial light modulator 40.

[0046] Specifically, step S1 is as follows: according to the phase mask image generated by the computer 41, the first light beam is modulated by the spatial light modulator 40 to convert it into a Pierce-Talbot-like beam. The phase mask image is generated according to the following initial field complex amplitude formula of the Pierce-Talbot-like beam:

[0047]

[0048] In the formula, is the Pierce function, n is the number of superimposed Pierce plasmons, c n is the superposition coefficient, w0 is the beam width, b and p are distribution factors, δ is the displacement factor, and a0 is the Gaussian attenuation factor.

[0049] Furthermore, the Pierce function variant in the initial field complex amplitude formula of the Pierce-like Talbot beam is:

[0050]

[0051] Specifically, step S2 specifically includes: S21, spatially filtering the Pierce-like Talbot beam through the spatial filtering module 50 to obtain a Pierce-like Talbot beam with only phase information; S22, changing the propagation direction of the Pierce-like Talbot beam with only phase information through the reflector 60 so that it is irradiated onto the slit-coupled exciter 70, so that the exciter 70 excites the surface plasmon to obtain a surface plasmon bottle array.

[0052] See also Figure 5 , Figure 5 This is a propagation diagram of a surface plasmon bottle array with adjustable overall structural distribution generated by the present invention. Figure 5 The three pictures on the left are, from top to bottom, propagation diagrams of surface plasmon bottle arrays with displacement factors δ=6μm, 7μm, and 8nm, respectively. Figure 5 The three pictures on the right are the propagation diagrams of surface plasmon bottle arrays with distribution factors b = 0.9, 1.1 and 1.3 from top to bottom. Figure 5 It can be seen that adjusting the displacement factor δ can adjust the overall position distribution of the surface plasmon bottle array, and adjusting the distribution factor b can adjust the distribution density and arrangement shape of each bottle structure in the surface plasmon bottle array.

[0053] See also Figure 6 , Figure 6 Propagation diagram of the surface plasmon bottle array with adjustable intensity distribution generated by the present invention. Figure 6 The three pictures from left to right are the superposition coefficient c n = propagation diagram of surface plasmon bottle arrays of {…,1,1,2,1,1,…}, {2,1,1,…,1,1,2} and {1,…,2,2,2,2,2,…,1}. Figure 6 It can be seen that the superposition coefficient c n ={2,1,1,…,1,1,2}, the intensity on the left and right sides of the surface plasmon bottle array is higher, and the intensity in the middle is lower; the superposition coefficient c n={1,…,2,2,2,2,2,…,1}, the intensity on the left and right sides of the surface plasmon bottle array is lower, and the intensity in the middle is higher; the superposition coefficient c n ={…,1,1,2,1,1,…}, the intensity at the center of the surface plasmon bottle array is the highest. Therefore, the superposition coefficient c is adjusted n The spatial distribution of the intensity of the surface plasmon bottle array can be adjusted.

[0054] See also Figure 7 , Figure 7 The propagation diagram of the surface plasmon bottle array with self-bending characteristics generated by the present invention. The Pierce function variant in the initial field complex amplitude formula of some Pierce-like Talbot beams is In the embodiment of the present invention, the surface plasmon bottle array finally generated has a self-bending property, and its effect is as follows: Figure 7 shown.

[0055] See also Figure 8 , Figure 8 This is a propagation diagram of the surface plasmon bottle array obtained by simulating the finite difference time-domain method of the present invention. The effectiveness of the dynamic surface plasmon bottle array preparation device of the present invention in generating the surface plasmon bottle array has been verified by the finite difference time-domain (FDTD) method.

[0056] exist Figure 5-8 In the illustrated embodiment, the number of superimposed Pierce plasmons n=11, the Gaussian attenuation factor a0=1 / 250, and the distribution factor p=0; the wavelength of the light beam emitted by the laser is 632.8 nm, and the beam width is 800 nm.

[0057] The present invention has the following technical effects:

[0058] 1. Compared with the existing surface plasmon bottle preparation method, the present invention can produce a bottle array with multiple pore arrays, which can capture and manipulate multiple particle groups at the same time and is suitable for high-throughput experimental scenarios.

[0059] 2. The present invention utilizes the surface plasmon effect to break through the diffraction limit and achieves smaller-scale particle capture and manipulation capabilities than traditional light bottle array technology.

[0060] 3. The present invention can dynamically control the structure and intensity arrangement of the surface plasmon bottle array by only changing the phase mask image generated by the computer, without changing the physical structure of the grating coupler. It has strong control flexibility and extremely low cost, and has a high cost performance.

[0061] 4. The present invention modifies the Pierce formula in the initial field complex amplitude formula of the Pierce-like Talbot beam, so that the generated surface plasmon bottle array has a self-bending characteristic. This self-bending characteristic is practical in many application fields. For example, in the field of particle manipulation, the self-bending characteristic can improve the accuracy of capturing particles, and the capture efficiency of 50nm polystyrene particles is more than 5 times higher than that of traditional optical tweezers, and it can also achieve non-contact dynamic regulation of the particle movement path.

[0062] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A method for preparing a dynamic surface plasmon bottle array, characterized in that: Includes steps: Modulate the beam into a Pierce-Talbot beam; The Pierce-Talbot beam is irradiated onto a slit-coupled exciter, so that the exciter excites surface plasmons, thereby obtaining a surface plasmon bottle array.

2. The method for preparing a dynamic surface plasmon bottle array according to claim 1, characterized in that: After the light beam is modulated into a Pierce-Tyber beam, the following steps are also included: The Pierce-Talbot beam is spatially filtered to obtain a Pierce-Talbot beam with only phase information.

3. The method for preparing a dynamic surface plasmon bottle array according to claim 2, characterized in that: The formula for the initial field complex amplitude of the Pierce-Talbot beam is: In the formula, is the Pierce function, n is the number of superimposed Pierce plasmons, c n is the superposition coefficient, w0 is the beam width, b and p are distribution factors, δ is the displacement factor, and a0 is the Gaussian attenuation factor.

4. The method for preparing a dynamic surface plasmon bottle array according to claim 3, characterized in that: The Pierce function variant in the initial field complex amplitude formula of the Pierce-like Talbot beam is:

5. A dynamic surface plasmon bottle array preparation device for executing the preparation method of claim 1, characterized in that: include: Lasers, spatial light modulators, and exciters; The laser generates a light beam; The spatial light modulator modulates the light beam into a Pierce-Talbot-like beam; The exciter is a slit-coupled exciter, which excites surface plasmons after being irradiated by a Pierce-Talbot-like beam, thereby obtaining a surface plasmon bottle array.

6. The dynamic surface plasmon bottle array preparation device according to claim 5, characterized in that: The exciter is a silver layer etched with nano-slits.

7. The dynamic surface plasmon bottle array preparation device according to claim 6, characterized in that: It also includes a spatial filtering module, which performs spatial filtering on the Pierce-Talbot beam to obtain a Pierce-Talbot beam with only phase information, and then irradiates the Pierce-Talbot beam with only phase information to the exciter.

8. The dynamic surface plasmon bottle array preparation device according to claim 7, characterized in that: The spatial filtering module specifically comprises: a first lens, an adjustable aperture, and a second lens which are sequentially arranged on the optical path of the Pierce-Talbot-like beam; The first lens and the second lens are Fourier lenses with the same focal length. Let the focal lengths of the first lens and the second lens be f, and the distance between the first lens and the second lens is 2f; the adjustable aperture is set in the middle of the first lens and the second lens; The adjustable diaphragm only allows the positive first-order diffraction fringes of the Pierce-Talbot beam to pass through, thereby obtaining a Pierce-Talbot beam with only phase information.

9. The dynamic surface plasmon bottle array preparation device according to claim 8, characterized in that: Also included is a beam expander and a beam splitter sequentially disposed on the optical path of the light beam generated by the laser; The beam expander expands and collimates the light beam generated by the laser; The beam splitter splits the expanded and collimated light beam into a first light beam and a second light beam, and allows the first light beam to irradiate the spatial light modulator.

10. The dynamic surface plasmon bottle array preparation device according to claim 9, characterized in that: Also included is a reflector disposed on the optical path of the Pierce-Talbot-like beam; The reflector changes the propagation direction of the Pierce-Talbot-like light beam with only phase information so as to illuminate the exciter.

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