Preparation method of nonlinear optical lens based on plasmon structure

Abstract

According to the method for enhancing the nonlinear effect based on the plasmon structure nonlinear optical lens, a single-layer two-dimensional material is transferred on a designed circular grating, then radial light is guided into a built experimental light path, and the effect of the prepared nonlinear lens is judged according to CCD imaging and spectral information. The main experimental method is as follows: plating a layer of gold film on an etched silicon wafer, obtaining the nonlinear lens formed by the circular grating through ultraviolet photoresist, an atomic layer deposition (ALD) system and a mechanical transfer method, and judging the effect of preparing the nonlinear lens according to the result of CCD imaging and spectral information.

Description

Technical Field

[0001] The present invention relates to the technical field of optical lenses, and in particular to a method for preparing and testing a nonlinear optical lens based on a plasmon structure. Background Art

[0002] In modern optical technology, optical lenses, as core components, are widely used in microscopic imaging, optical communications, sensing and other fields. However, traditional optical lenses face problems such as diffraction limit, volume and weight, and it is difficult to meet the needs of high resolution, dynamic zoom, ultra-thin design and beam shaping. The existing traditional Gaussian beam is easy to generate and control, has good beam quality and simple beam shaping. It can be shaped by optical elements such as lenses, gratings, and spatial light modulators to meet different application requirements. However, the focusing of Gaussian beams is limited by the diffraction limit, which means that sub-wavelength focusing cannot be achieved; in nonlinear media, the nonlinear effect of Gaussian beams is not as significant as that of radially polarized beams. At present, the existing designs all use Gaussian beams and plasmon nanostructures to achieve nonlinear characteristics, which are relatively mature and help promote the development of nanoscale nonlinear nanophotonic applications.

[0003] Through the above analysis, the problems and defects of the prior art are: in the prior art, few people use the characteristics of radially polarized light to achieve tighter beam focusing to excite the nonlinear characteristics of hybrid plasmon nanostructures. Summary of the invention

[0004] The present invention provides a research method for a nonlinear optical lens based on a plasmon structure under radial polarized light conditions, so as to solve the problem in the prior art of achieving tighter light beam focusing to excite the nonlinear characteristics of a plasmon nanostructure.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A method for preparing a nonlinear optical lens based on a plasmon structure comprises the following steps:

[0007] S1: Preparation of circular grating samples;

[0008] S2: Transfer the single layer WSe2 onto the circular grating prepared in step 1 to form a nonlinear lens.

[0009] Furthermore, step S1 is specifically as follows:

[0010] First, a circular grating template is etched on a substrate by a focused ion beam (FIB); second, a precious metal film with a thickness of b is deposited on the etched circular grating template at a certain deposition rate A by thermal evaporation, and then a transparent glass sheet is gently adhered to the fresh precious metal film surface with ultraviolet curing glue (norland optical glue 61); after that, the glass sheet and the precious metal film are peeled off from the silicon wafer at the same time with a blade to obtain an ultra-smooth precious metal film; because the precious metal film was previously bonded to the silicon wafer, it has a similar flatness to the silicon wafer. Next, an aluminum oxide film of a certain thickness is deposited on the surface of the precious metal film using atomic layer deposition (ALD) technology to obtain a circular grating sample.

[0011] Furthermore, the substrate is one of glass, iron plate, steel plate, aluminum plate, silicon wafer, SiO2 wafer, and the substrate size is 100-1000mm 2 .

[0012] Furthermore, the etching period is 400nm-800nm, and the etching thickness is 50-80nm.

[0013] Furthermore, the noble metal is one of Au, Ag, and Al, the deposition rate A is 0.3-0.8 A / s, and the thickness b is 150-250 nm.

[0014] Furthermore, step S2 is specifically as follows:

[0015] First, the torn two-dimensional material was transferred to a SiO2 / Si substrate; then a polystyrene solution with a concentration of 0.17 g / ml was spin-coated on the single-layer WSe2 material at a certain rate. Next, a drop of deionized water was dropped on one edge of the SiO2 / Si substrate to peel the composite material off the SiO2 / Si substrate.

[0016] Secondly, a transfer table (prcbemini) was used for alignment transfer. The circular grating sample prepared by S1 was fixed on the transfer table, and under the observation of a microscope, the polystyrene in the above composite material was aligned and transferred to the sample of the circular gold grating. The two-dimensional material covered the center of the circular grating to obtain the sample. Finally, the above sample was immersed in an etching solution to dissolve the polystyrene film and obtain a nonlinear lens.

[0017] Furthermore, the two-dimensional material may be one of WSe2, MoSe2, WS2, MoSe2, graphene, and BN, and the two-dimensional material is a single layer.

[0018] Furthermore, in step 1, the thickness of the aluminum oxide film is 3nm-5nm.

[0019] Furthermore, the polystyrene solution is prepared by dissolving polystyrene with a molecular weight of 260,000 in a toluene solution, wherein the concentration of the polystyrene is 0.1 g / ml-0.2 g / ml, and the spin coating rate is 1000-3000 rpm / min.

[0020] Furthermore, the etching solution is a dichloromethane or chloroform solution.

[0021] A system for performing experimental tests using a vortex beam, the experimental system comprising a 100x objective lens, a nonlinear lens being placed below the 100x objective lens; a first beam splitter, a second beam splitter and a third beam splitter being sequentially arranged above the 100x objective lens, a WPV10L-780 vortex plate, a polarizing plate, a second lens, a first lens and a 780nm laser being horizontally arranged in sequence on the left side of the first beam splitter; a first slit, a first bandpass filter, a third lens and a spectrometer being horizontally arranged in sequence on the left side of the second beam splitter; a fourth lens, a second bandpass filter, a second slit, a fifth lens, a sixth lens and a first CCD camera being horizontally arranged in sequence on the right side of the third beam splitter, and a second CCD camera being arranged above the third beam splitter.

[0022] Furthermore, by changing the focal length of the lens combination, the diameter of the light spot formed by the incident light beam is 5-15um, thereby achieving the control of the light spot size.

[0023] The advantages of the present invention are:

[0024] 1. By using glass sheets, silicon wafers, SiO2, etc. as substrates, an ultra-smooth gold film with a circular grating can be obtained, which has the advantages of high sensitivity, anti-interference ability, size and weight of the circular grating; by depositing an aluminum oxide film on the surface of the precious metal film, the transmittance and optical performance of the optical lens can be improved; the high polarization sensitivity characteristics of a single-layer two-dimensional material can be used to better perform high-resolution imaging.

[0025] 2. This invention combines radial beams and plasmon structures to achieve efficient nonlinear optical effects at lower light intensities, thereby designing nonlinear optical devices with superior performance and compact structure, and improving the feasibility of their practical applications. This invention is based on the research method of hybrid plasmon structure nonlinear optical lenses under radial polarized light conditions, which is easy to operate and can be used for qualitative and quantitative analysis based on the results of CCD imaging and spectral information.

[0026] 3. The introduction of radial beams and plasmon structures can further improve the performance of optical lenses, such as enhancing focusing ability, improving imaging resolution, and achieving multifunctional integration. Plasmon structures combine the advantages of metal nanostructures and dielectric materials, and can significantly improve the performance of optical lenses. Radial beams have unique focusing characteristics, which can form extremely small focal points and extremely high electric field strengths after focusing, further improving the efficiency of light-matter interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process of preparing a nonlinear optical lens.

[0028] Figure 2 It is a schematic diagram of the cross-sectional structure of a nonlinear lens.

[0029] Figure 3 It is a schematic diagram of the system structure for experimental testing using vortex beams. DETAILED DESCRIPTION

[0030] The implementation of the present invention is described in detail below, and examples of the implementation are shown in the accompanying drawings to further describe the present invention, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0031] Example 1

[0032] A method for preparing a nonlinear optical lens based on a plasmon structure comprises the following steps:

[0033] S1: Preparation of circular gold grating samples;

[0034] First, a circular grating template with a period of 700nm and a thickness of 70nm was etched on a silicon wafer by a focused ion beam (FIB); secondly, a 200nm gold film was deposited on the etched circular grating template at a rate of 0.5A / s by thermal evaporation (model: jsd-400), and then a transparent glass sheet was gently adhered to the fresh gold film surface with ultraviolet curing glue (norland optical glue 61); after that, the glass sheet and the gold film were peeled off from the silicon wafer at the same time with a blade to obtain an ultra-smooth gold film; because the gold film was previously bonded to the silicon wafer, it has a similar flatness to the silicon wafer. Next, an aluminum oxide film with a thickness of 5nm was deposited on the gold film surface using atomic layer deposition (ALD) technology to improve the transmittance and optical performance of the optical lens, thereby obtaining a circular gold grating sample.

[0035] S2: Transferring a single layer of WSe2 onto the gold grating sample prepared in step 1 to form a nonlinear lens;

[0036] First, the torn single-layer WSe2 material was transferred to the SiO2 / Si substrate; then a PS solution (polystyrene solution) with a concentration of 0.17 g / ml was spin-coated on the single-layer WSe2 material at a rate of 3000 rpm / min. Next, a drop of deionized water was dripped on one edge of the SiO2 / Si substrate. Under the action of deionized water, the adhesion of the PS / WSe2 film to the SiO2 / Si was reduced, and the WSe2-PS material was peeled off from the SiO2 / Si substrate. At this point, a PS with a single-layer WSe2 material loaded on the lower surface was obtained.

[0037] Secondly, a transfer table (prcbe mini) was used for alignment transfer. The circular gold grating sample was fixed on the transfer table, and the PS alignment was transferred to the circular gold grating sample under the observation of a microscope. A single layer of WSe2 material was covered on the center of the circular gold grating sample to obtain a PS-WSe2-Au sample. Finally, the PS-WSe2-Au sample was immersed in a dichloromethane solution to dissolve the PS film and obtain a nonlinear lens.

[0038] Example 2

[0039] A system for performing experimental tests using a vortex beam, the experimental system comprising a 100x objective lens 18, a nonlinear lens 17 being placed below the 100x objective lens 18; a first beam splitter 6, a second beam splitter 7 and a third beam splitter 11 being arranged in sequence above the nonlinear lens 17, a WPV10L-780 vortex plate 5, a polarizing plate 4, a second lens 3, a first lens 2 and a 780nm laser 1 being arranged in sequence horizontally on the left side of the first beam splitter 6; a first slit 8, a first bandpass filter 9, a third lens 10 and a spectrometer 19 being arranged in sequence horizontally on the left side of the second beam splitter 7; a fourth lens 12, a second bandpass filter 13, a second slit 14, a fifth lens 15, a sixth lens 16 and a first CCD camera 21 being arranged in sequence horizontally on the right side of the third beam splitter 11, and a second CCD camera 20 being arranged above the third beam splitter 11.

[0040] The 780nm laser 1 emits an incident light beam, which is collimated and expanded by the lens combination of the first lens 1 and the second lens 2, and the spot size can be controlled by changing the focal length of the lens combination. The diameter of the light spot obtained by the above modulation is 10um. The expanded laser passes through the polarizer 4 and the WPV10L-780 vortex plate 5 (the expanded laser must pass through the center of the WPV10L-780 vortex plate 5), and the polarization type is adjusted by adjusting the fast axis angle of the polarizer 4 and the WPV10L-780 vortex plate 5. When the fast axis directions of the polarizer 4 and the WPV10L-780 vortex plate 5 are parallel, the output is radial polarized light; when the fast axis directions of the polarizer 4 and the WPV10L-780 vortex plate 5 are perpendicular, the output is angular polarized light; in this embodiment, the fast axis directions of the polarizer 4 and the WPV10L-780 vortex plate 5 are set to be parallel.

[0041] The light emitted by the 780nm laser 1 passes through the first lens 2, the second lens 3, the polarizer 4, the WPV10L-780 vortex plate 5, and the first beam splitter 6 in sequence. The reflected light passing through the beam splitter 6 is incident on the nonlinear lens 17 through the nonlinear lens. The reflected light of the sample passes through the first beam splitter 6, the second beam splitter 7 and the third beam splitter 11 in sequence on the optical path. One path of the outgoing light from the second beam splitter 7 passes through the first slit 8, the first bandpass filter 9, and the third lens 10 in sequence and is incident on the spectrometer 19 to collect the spectral information of the sample; the other path of the outgoing light passes through the third beam splitter 11 on the optical path, and one path of the outgoing light from the third beam splitter 11 passes through the fourth lens 12, the second bandpass filter 13, the second slit 14, the fifth lens 15, and the sixth lens 16 in sequence and is incident on the first CCD camera 21 to collect Fourier imaging. The other path of light enters the second CCD camera 20 to collect imaging of the base frequency and the doubled frequency.

Claims

1. A method for preparing a nonlinear optical lens based on a plasmon structure, characterized in that: The steps include: S1: Preparation of circular grating samples; S2: Transfer the single layer WSe2 to the circular grating sample prepared in step 1 to form a nonlinear lens.

2. A system for experimental testing using a vortex beam, characterized in that: The experimental system comprises a 100x objective lens (18), a nonlinear lens (17) is placed below the 100x objective lens (18); a first beam splitter (6), a second beam splitter (7) and a third beam splitter (11) are arranged in sequence above the 100x objective lens (18); a WPV10L-780 vortex plate (5), a polarizing plate (4), a second lens (3), a first lens (2) and a 780nm laser (1) are arranged in sequence on the left side of the first beam splitter (6); a first slit (8), a first bandpass filter (9), a third lens (10) and a spectrometer (19) are arranged in sequence on the left side of the second beam splitter (7); a fourth lens (12), a second bandpass filter (13), a second slit (14), a fifth lens (15), a sixth lens (16) and a first CCD camera (21) are arranged in sequence on the right side of the third beam splitter (11); and a second CCD camera (20) is arranged above the third beam splitter (11).

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