Preparation method of metal material surface plasmon waveguide based on metal nanoparticles

Abstract

The invention provides a preparation method of a metal material surface plasmon waveguide based on metal nanoparticles. The method mainly comprises the following steps: firstly, distributing metal nanoparticles on the surface of a metal substrate, and then vertically irradiating the substrate by adopting an ultraviolet nanosecond laser beam, so as to generate a nanoscale stripe pattern with a specific period on the surface of a material. Different periodic nanostructures can be obtained on the surface of the material by regulating and controlling the distance, the angle and the number of the metal nanoparticles. Cubic, cylindrical and spherical metal nanoparticles are preferably selected as media, and the obtained periodic surface structure can be used for preparing a plasmon waveguide device.

Description

Technical Field

[0001] The present invention relates to a technology for preparing and regulating periodic structures on the surface of metal materials, and specifically to a method for preparing plasmon waveguides on the surface of metal materials based on metal nanoparticles. Background Art

[0002] The formation of existing laser-induced periodic surface structures (LIPSS) begins with randomly distributed rough particles or microscopic inhomogeneities on the material surface. These defective regions preferentially absorb laser energy, triggering local field enhancement, thereby inducing the generation of periodic striped structures. However, this spontaneous process exhibits significant randomness in the starting position, number distribution, and direction of the stripes, making it difficult to meet the requirements for precise design and high reproducibility of surface plasmon polariton (SPP) devices. Summary of the Invention

[0003] The present invention provides a method for preparing a metal material surface plasmon waveguide based on metal nanoparticles.

[0004] The technical solution for achieving the objectives of the present invention is: a method for preparing a plasmon waveguide on the surface of a metal material based on metal nanoparticles, in which metal nanoparticles are arranged on the surface of the metal material, and the spacing, angle and number of the metal nanoparticles are controlled. When a laser is vertically irradiated on a substrate material having metal nanoparticles, different periodic nanostructures are obtained on the surface of the material.

[0005] Preferably, the metal nanoparticles are in the shape of cubes, cylinders, or spheres.

[0006] Preferably, the side length of cubic metal nanoparticles ranges from 150nm to 250nm; the bottom diameter and height of cylindrical metal nanoparticles are equal and range from 150nm to 250nm; the diameter of spherical metal nanoparticles ranges from 150nm to 250nm.

[0007] Preferably, the metal nanoparticles are arranged along the polarization direction of the laser or perpendicular to the polarization direction of the laser.

[0008] Preferably, when the metal nanoparticles are arranged parallel to the polarization direction of the laser, the number of particles is 2; when the metal nanoparticles are arranged perpendicular to the polarization direction of the laser, the number of particles is 10-20.

[0009] Preferably, when two metal nanoparticles are arranged along the polarization direction of the laser, the spacing between the metal nanoparticles is 1000 nm plus an even multiple of the half wavelength of the SPP. By controlling the spacing of the metal nanoparticles, the number of stripes is changed, thereby achieving the regulation of the number of waveguide tooth structures.

[0010] Preferably, when multiple metal nanoparticles are arranged perpendicular to the polarization direction of the laser, the spacing between the metal nanoparticles is 50nm-175nm. By controlling the number of metal nanoparticles, the length of the stripes is changed to achieve regulation of the waveguide length.

[0011] Compared with the existing technology, the present invention has the following significant advantages: by pre-arranging metal nanoparticles in an orderly manner on the surface of a metal material, the metal nanoparticles are used to control the distribution pattern of laser energy on the material surface, thereby forming a spatial distribution of laser energy concentration areas on the material surface determined by the arrangement of the metal nanoparticles, thereby guiding the formation of LIPSS stripes in the laser energy concentration areas where the energy exceeds the material ablation threshold, and realizing a LIPSS stripe structure determined by the arrangement of the metal nanoparticles; because the random distribution characteristics of the starting position and length of the existing LIPSS stripes are overcome, the LIPSS stripe structure proposed by the present invention can be used to construct an SPP waveguide channel with a regular structure and precise tooth shape.

[0012] In addition, the metal nanoparticles that meet the requirements of the present invention can be prepared based on a standardized process or purchased directly from a commercial company. The metal nanoparticles obtained in this way have stable composition, high-precision geometric dimensions, and good repeatability.

[0013] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the arrangement of metal nanoparticles.

[0015] Figure 2 Energy distribution on the substrate surface when bimetallic nanoparticles are arranged along the polarization direction under laser irradiation.

[0016] Figure 3 Based on Figure 2 The prepared SPP waveguide structure.

[0017] Figure 4 Energy distribution on the substrate surface when multi-metal nanoparticles are arranged along the polarization direction under laser irradiation.

[0018] Figure 5 Based on Figure 4 The prepared SPP waveguide structure. DETAILED DESCRIPTION

[0019] A method for fabricating surface plasmon waveguides on metal materials based on metal nanoparticles. Metal nanoparticles are arranged on the surface of a metal material, and the spacing, angle, and number of the metal nanoparticles are controlled. When a laser is vertically irradiated onto the substrate material containing the metal nanoparticles, different periodic nanostructures can be obtained on the material surface. These structures can be used to fabricate SPP waveguides. The specific steps are:

[0020] Arrange metal nanoparticles on the surface of metal materials and regulate the spacing, angle and number of particles.

[0021] Furthermore, the metal nanoparticles are in the form of cubes, cylinders, or spheres.

[0022] Furthermore, the side length of the cubic metal nanoparticles is 150nm-250nm, the bottom diameter and height of the cylindrical metal nanoparticles are equal, which is 150nm-250nm, and the diameter of the spherical metal nanoparticles is 150nm-250nm.

[0023] Furthermore, the metal nanoparticles are arranged along the polarization direction of the laser and perpendicular to the polarization direction of the laser.

[0024] Furthermore, when the metal nanoparticles are arranged parallel to the polarization direction of the laser, the number of particles is 2; when the metal nanoparticles are arranged perpendicular to the polarization direction of the laser, the number of particles is 6-20.

[0025] For the SPP wavelength, its value is related to the dielectric constant of the material and the calculation formula is:

[0026]

[0027] Where ε is the dielectric constant of the material, ε d is the dielectric constant of the environment, which is air, so ε d =1.

[0028] For the period of LIPSS, the wavelength of the surface plasmon corresponds to the period of LIPSS, and the calculation formula is as follows:

[0029]

[0030] Where Λ is the period of the LIPSS, λ is the incident laser wavelength, and θ is the laser incident angle. This indicates that when the laser is incident perpendicularly, the wavelength of the SPP is numerically equal to the period of the LIPSS. Specifically, when the incident laser wavelength is 355 nm and the material is iron, with a dielectric constant of ε = -1.7996 + 9.1233i, the LIPSS period is calculated to be 350 nm.

[0031] Furthermore, the electromagnetic field enhancement area on the surface of the material will etch the material to form LIPSS. When the two particles are arranged along the laser polarization direction, the multiple periodic etching stripes formed between the particles are distributed in a tooth-like manner, such as Figure 3 As shown in (a), the structure can be used as a tooth structure in a waveguide to achieve bandpass or bandstop filtering functions.

[0032] Furthermore, when multiple metal nanoparticles are arranged perpendicular to the laser polarization direction, the surrounding area forms a periodic stripe structure parallel to the particle arrangement direction, such as Figure 5 As shown in (a), this structure can be used as a transmission channel in a surface plasmon waveguide to realize the waveguide transmission function.

[0033] Furthermore, when two metal nanoparticles are arranged along the polarization direction of the laser, the spacing between them is 1000 nm plus an even multiple of the SPP half wavelength. By changing the particle spacing, the number of stripes between the metal nanoparticles on the substrate surface can be controlled.

[0034] Furthermore, when multiple metal nanoparticles are arranged perpendicular to the laser polarization direction, the spacing between them is 50nm-175nm. Changing the number of particles can achieve regulation of the substrate surface energy and thus control the length of the waveguide.

[0035] In a specific embodiment, the metal nanoparticles are arranged as follows Figure 1 As shown, Figure 1 (a) shows two cubic metal nanoparticles arranged along the laser polarization direction, with a spacing of 1000 nm plus an even multiple of the SPP half wavelength; Figure 1 (b) Multiple cylindrical metal nanoparticles are arranged perpendicular to the laser polarization direction, with a spacing of 50 nm to 175 nm. The red arrow indicates the laser polarization direction, c is the metal nanoparticle size, and s is the spacing between the metal nanoparticles.

[0036] When a 355nm wavelength linearly polarized laser is vertically irradiated on a metal surface where two cubic metal nanoparticles with a size c of 200nm are arranged, the following will appear on the surface of the material: Figure 2 When two cubic metal nanoparticles are arranged along the laser polarization direction and the particle spacing s is 1350nm, Figure 2 (a) is the electromagnetic field energy distribution on the surface of the substrate material. Two stripes are formed between the metal nanoparticles on the surface of the material. Figure 2 (b) is the electromagnetic field energy distribution at the substrate XOZ section (y = 0), and the shaded area is the position of the metal nanoparticles; when the particle spacing s is 1700nm, Figure 2 (c) is the electromagnetic field energy distribution on the surface of the substrate material. Three stripes are formed between the metal nanoparticles on the surface of the material. Figure 2 (d) is the electromagnetic field energy distribution at the substrate XOZ section (y=0).

[0037] Further, by Figure 2 (b) Figure 2 (d) The electromagnetic field energy distribution at the substrate XOZ cross section (y=0) shows that the energy in the middle region of the metal nanoparticles is significantly stronger than that in other regions, so stripe structures can be formed by ablation between particles on the material surface.

[0038] When a 355nm wavelength linearly polarized laser is vertically irradiated on a metal surface where multiple cylindrical metal nanoparticles with a size c of 200nm are arranged, the following phenomenon will appear on the surface of the material: Figure 2 The periodic energy distribution is shown. When the particle spacing s is 50nm, Figure 4 (a) shows the electromagnetic field energy distribution on the substrate surface when 10 cylindrical metal nanoparticles are arranged perpendicular to the laser polarization direction. Figure 4 (b) shows the electromagnetic field energy distribution on the substrate surface when 14 cylindrical metal nanoparticles are arranged perpendicular to the laser polarization direction. The waveguide length can be controlled by controlling the spacing between the metal nanoparticles.

[0039] Further, by Figure 4 (c) The electromagnetic field energy distribution at the XOZ cross section (y = 0) of the substrate shows that the energy of the first stripe around the metal nanoparticles on the material surface is significantly stronger than the energy of the other stripes, so a stripe can be formed by near-field ablation of the metal nanoparticles on the material surface.

[0040] Example 1:

[0041] The following describes the technical solution of the present invention in detail by taking the construction of a surface SPP waveguide structure based on iron nanocubes on an iron substrate as an example.

[0042] (1) Provide a single-side polished iron substrate with a size of 1 mm × 1 mm × 0.5 mm.

[0043] (2) Two cubic iron metal nanoparticles with a side length c of 200 nm are arranged on the surface of the iron substrate, along the polarization direction of the laser, and the particle spacing s is 1700 nm, as shown in FIG. Figure 1 As shown in (a).

[0044] (3) A linearly polarized laser with a wavelength of 355 nm is used to vertically irradiate the surface of the iron substrate on which the metal nanoparticles are arranged.

[0045] (4) After irradiation, the metal nanoparticles are removed and three stripe-shaped periodic etching structures are obtained on the surface of the iron substrate. Each stripe has a length of 400 nm, a width of 175 nm, and an etching depth of 70 nm. Figure 2 (c) shown.

[0046] (5) Two metal substrates with the aforementioned periodic striped structures are stacked up and down using a high-precision alignment device to align the stripe orientations and achieve nanometer-scale alignment. An air gap of equal spacing naturally forms between the two substrates, forming a periodically aligned SPP waveguide channel. By controlling the spacing of the metal nanoparticles, the number of stripes can be adjusted, thereby achieving controllable modulation of the number of waveguide tooth-like structures. In this embodiment, the air gap width w is 50 nm.

[0047] (6) The SPP waveguide structure formed is as follows Figure 3 (a) shows the parameters as follows: stripe width a is 175nm, stripe spacing b is 175nm, air channel width w is 50nm, etching depth d is 70nm, and the number of periodic stripes N is 3. Its transmission spectrum is shown in Figure 3 As shown in (b), the device exhibits a transmittance of about 65% in the wavelength range of 900nm to 1100nm.

[0048] Example 2

[0049] (1) Provide a single-side polished iron substrate with a size of 1 mm × 1 mm × 0.5 mm.

[0050] (2) Arrange 10 cylindrical iron metal nanoparticles with a size c of 200 nm on the surface of the iron substrate, arranged perpendicular to the laser polarization direction, with a particle spacing s of 50 nm. The arrangement model is as follows: Figure 1 (b) shown.

[0051] (3) A linearly polarized laser with a wavelength of 355 nm is used to vertically irradiate the surface of the iron substrate on which the metal nanoparticles are arranged.

[0052] (4) After the laser irradiation is completed, the metal nanoparticles are removed and an etched stripe structure is formed near the particles on the surface of the iron substrate with a length of 3 μm, a width of 175 nm, and a depth of 70 nm. Figure 4 As shown in (a).

[0053] (5) The etched stripe structure constitutes an SPP waveguide channel. By adjusting the number of metal nanoparticles, the length of the stripe structure can be further controlled to achieve adjustment of the waveguide length.

[0054] (6) The prepared SPP waveguide structure is as follows Figure 5 As shown in (a), its geometric parameters are: waveguide length is 3μm, width a is 175nm, and depth d is 70nm; the simulation results of its effective refractive index real part and propagation distance changing with wavelength are shown in Figure 5 (b) shown.

Claims

1. A method for preparing a metal material surface plasmon waveguide based on metal nanoparticles, characterized in that: Metal nanoparticles are arranged on the surface of the metal material, and the spacing, angle and number of the metal nanoparticles are regulated. When the laser is vertically irradiated on the base material with the metal nanoparticles, different periodic nanostructures are obtained on the surface of the material.

2. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 1, characterized in that: The metal nanoparticles are in the shape of a cube, a cylinder or a sphere.

3. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 2, characterized in that: The side length of cubic metal nanoparticles ranges from 150nm to 250nm; the bottom diameter and height of cylindrical metal nanoparticles are equal, ranging from 150nm to 250nm; the diameter of spherical metal nanoparticles ranges from 150nm to 250nm.

4. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 1, characterized in that: The metal nanoparticles are arranged along the polarization direction of the laser or perpendicular to the polarization direction of the laser.

5. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 4, characterized in that: When the metal nanoparticles are arranged parallel to the laser polarization direction, the number of particles is 2; when the metal nanoparticles are arranged perpendicular to the laser polarization direction, the number of particles is 10-20.

6. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 5, characterized in that: When two metal nanoparticles are arranged along the polarization direction of the laser, the spacing between the metal nanoparticles is 1000 nm plus an even multiple of the half wavelength of the SPP. By controlling the spacing of the metal nanoparticles, the number of stripes can be changed, thereby achieving the control of the number of waveguide tooth structures.

7. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 5, characterized in that: When multiple metal nanoparticles are arranged perpendicular to the laser polarization direction, the spacing between the metal nanoparticles is 50nm-175nm. By controlling the number of metal nanoparticles, the length of the stripes can be changed to achieve the control of the waveguide length.

8. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 1, characterized in that: The metal substrate and the metal nanoparticle materials are iron, copper, silver, gold, chromium or platinum.

9. The method for preparing a metal material surface plasmon waveguide based on metal nanoparticles according to claim 1, characterized in that: The incident laser wavelength is 300nm-2000nm.

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