CN106501898A - Metal nanoparticle-insulation composite material grating coupler - Google Patents

Abstract

The invention discloses a metal nanoparticle-insulator composite material grating coupler, a preparation method and an application thereof. The grating coupler is composed of a metal nanoparticle-insulator composite coupling grating and an insulator optical planar waveguide. The modified layer of nanoparticle-insulator composite material is a two-dimensional orthogonal rectangular diffraction grating prepared by electron beam lithography and reactive ion beam etching technology. Compared with the insulator grating coupler with the same structure, the invention has higher coupling efficiency, and there is no loss caused by free carrier absorption. In addition, the present invention is not sensitive to the polarization direction of light, and while realizing light coupling, light filtering, beam splitting and deflection can also be realized by means of formation of guided waves and diffraction distortion. The invention can be used in the fields of preparation of large-scale integrated optical circuits and the like.

Description

Metal Nanoparticle-Insulator Composite Grating Coupler

Technical field:

The invention belongs to the technical field of nanophotonics, and relates to the preparation technology of grating couplers in visible and/or near-infrared bands, in particular to a metal nanoparticle-insulator composite grating coupler working in visible and/or near-infrared bands. device and its preparation method.

Background technique:

Grating couplers play an important role in the construction of integrated optical devices and large-scale integrated optical circuits. Using grating couplers, optical signals in the visible and/or near-infrared bands can be effectively introduced into or extracted from optical planar waveguides, thereby realizing optical signal directional transmission and subsequent processing. A grating coupler is an integration of a coupling grating and a planar waveguide. According to the material on which the coupling grating is based, the existing grating couplers can be divided into two categories, namely insulator grating couplers and metal grating couplers. Compared with metal grating couplers, insulator grating couplers do not have the effect of free carrier absorption on coupling efficiency, and are also easier to integrate with insulator optical planar waveguides, so in applications based on visible and/or near-infrared bands , the insulator grating coupler dominates. The coupling efficiency of the insulator grating coupler depends on the diffraction efficiency of the coupling grating, and the diffraction efficiency of the coupling grating depends on the thickness, side shape, and refractive index contrast of the coupling grating (the ratio of the refractive index of the high refractive index area to the low refractive index area ) and duty cycle (also known as filling fraction, which is the ratio of the width of the high refractive index region to the grating constant), etc., for a coupling grating with a definite structure, the refractive index contrast is the key factor determining its diffraction efficiency, and generally In other words, a high refractive index contrast will result in a large diffraction efficiency. There are two methods for the integration of insulator-coupled gratings and insulator optical planar waveguides. One is to construct the required periodic structure on the surface of the substrate material, and then deposit the waveguide layer; The required periodic structure, and then deposit the upper cover layer as the substrate. These two methods have exactly the same effect. The formed grating coupler has high reliability because the coupling grating is buried in it. However, in the refraction In the rate-type planar waveguide structure, the refractive index of the waveguide material is larger than that of the substrate material and the cover material, and the commonly used insulator optical planar waveguide materials, such as SiO ₂ , Al ₂ O ₃ and PMMA (organic glass), etc., Their refractive indices are relatively small, limited by this, the grating coupler integrated by the above method will not have high coupling efficiency. So, how can we construct high-efficiency grating couplers on commonly used insulator optical planar waveguides? This has become a focus of recent research. In addition, there is another problem that needs attention, that is, in the previous research on the grating coupler, since the focus is on coupling, it is hoped to be able to use a higher Efficiency leads optical signals of a certain polarization direction into or out of the planar waveguide, so coupling gratings mostly adopt a one-dimensional structure rather than a two-dimensional structure. In fact, if a coupling grating with a two-dimensional structure, especially a rectangular coupling grating with a two-dimensional orthogonal structure, can make its ±1st-order diffraction meet the matching condition, its combination with an optical planar waveguide can also form an efficient grating coupling This two-dimensional grating coupler is not only insensitive to the polarization direction of light, but also can achieve light filtering, beam splitting and deflection by means of the formation of guided waves and diffraction distortion while realizing light coupling. This is of great significance for the construction of functional integrated optical devices and large-scale integrated optical circuits based on them.

Metal ion implantation is a mature and flexible method for surface modification of insulating materials. Implanting low-energy, high-dose metal ions (especially Drude metal ions) into the insulator can form metal nanoparticles with a certain depth distribution in the near-surface region of the insulator, in other words, it can form a layer with a certain thickness. The modified layer of metal nanoparticles-insulator composite material, the thickness of the modified layer and the average size and volume fraction of metal nanoparticles can be regulated by changing the implantation energy and dose of metal ions. It is worth noting that within a certain dose range, the metal nanoparticle-insulator composite modified layer formed by metal ion implantation is still insulating, but its optical properties are significantly better than that of the unmodified insulator. different. There is a resonant absorption wavelength λ _SPR related to the metal nanoparticle surface plasmon in the modified layer of metal nanoparticles-insulator composite material. When the wavelength of the incident light is equal to λ _SPR , the incident light will be strongly absorbed, and when the wavelength of the incident light is When it is greater than λ _SPR : First, the real part of the effective refractive index of the modified layer of the composite material (abbreviated as the refractive index without causing confusion) is larger than the refractive index of the insulator. The volume fraction of the particles is related to the wavelength of the incident light. The larger the volume fraction of the metal nanoparticles, the closer the wavelength of the incident light is to λ _SPR , and the greater the difference between the refractive indices; secondly, the effective refraction of the modified layer of the composite material The imaginary part of the ratio (that is, the extinction coefficient) is very small in a considerable wavelength range and can basically be ignored; moreover, the surface plasmons of the metal nanoparticles scatter the incident light, which leads to the loss of the modified layer of the composite material. There is an additional increase in reflectivity, which can be seen as a result of an additional increase in the refractive index of the modified layer of the composite from the Fresnel reflection point of view. According to the above-mentioned optical properties exhibited by the modified layer of the composite material, we have reason to believe that based on the metal ion implantation modification of the insulator optical planar waveguide, through the reasonable design of the coupling grating structure (especially the grating constant), combined with It is possible to construct a new type of high-efficiency grating coupler with micro-nano processing technologies such as electron beam lithography and ion beam etching.

Recently, Stepanov et al. published a research result (Applied Physics A(2013) 111:261～264). They used the calibration grid made of Ni in the scanning electron microscope as the injection template, and the energy and dose were 40keV and 5× Cu ion implantation of 10 ¹⁶ cm ^-2 forms a so-called two-dimensional periodic plasmonic structure on the surface of SiO ₂ thin plate, which exhibits good diffraction characteristics for incident light with a wavelength of 632.8nm. It is worth noting that although the two-dimensional periodic plasmonic structure proposed by Stepanov et al. can be used as a diffraction grating, it cannot form a practical high-efficiency grating coupler together with the SiO ₂ planar waveguide. The main reason is that Its grating constant is too large. According to the scanning electron microscope observation results given in the literature, its grating constants on the rows and columns are 49 and 36 μm, respectively. For applications in the visible and/or near-infrared bands, such a large The grating constant makes the diffraction of small orders unable to meet the matching condition at all, so it is impossible to form a strong guided wave in the planar waveguide.

Invention content:

The invention aims to provide a metal nano particle-insulator composite material grating coupler working in visible and/or near-infrared bands, and a preparation method and application of the grating coupler.

The technical scheme that the present invention takes for realizing its purpose is as follows:

The metal nanoparticle-insulator composite grating coupler is composed of a metal nanoparticle-insulator composite coupling grating and an insulator optical planar waveguide. The metal nanoparticle-insulator composite coupling grating is a two-dimensional orthogonal rectangular diffraction grating with a thickness of It is 40-150nm, located in the modified layer formed by metal ion implantation on the surface of the insulator optical plane waveguide, and has no obvious interface with the insulator optical plane waveguide.

Preferably, the metal nanoparticles in the metal nanoparticle-insulator composite material coupling grating are one of the three metal nanoparticles of Ag, Cu and Au.

Preferably, the metal nanoparticle-insulator composite material coupling grating has the same grating constant and duty cycle on the row and column, and the grating constant is 1.05 to 1.5 of the surface plasmon resonance absorption wavelength of the metal nanoparticle in the insulator optical planar waveguide. The duty cycle is the ratio of the width of the metal nanoparticle-insulator composite material in the metal nanoparticle-insulator composite coupling grating to the grating constant, which is controlled between 30% and 50%.

Preferably, the insulator optical planar waveguide is a thin film or thin plate made of transparent solid insulating material in visible and/or near-infrared bands.

The preparation method of the metal nano particle-insulator composite material grating coupler comprises the following steps:

(1) Select or prepare an insulator optical planar waveguide with a certain thickness;

(2) Inject metal ions with a certain energy and dose into the insulator optical planar waveguide in a certain way, and form a metal nanoparticle-insulator composite material modification layer on the surface of the insulator optical planar waveguide;

(3) Using electron beam lithography technology, a photoresist mask layer with the required two-dimensional coupling grating structure information is prepared on the surface of the insulator optical planar waveguide implanted with metal ions;

(4) Relying on the metal nanoparticle-insulator composite material modification layer formed on the surface of the insulator optical planar waveguide, it is etched by reactive ion beam etching technology, and the etching depth is 40-150nm. After subsequent degumming treatment, the structure The desired two-dimensional metal nanoparticle-insulator composite coupling grating is obtained.

Preferably, the metal ion in step (2) is one of the three metal ions of Ag, Cu and Au.

Preferably, the metal ion implantation method in step (2) is either vertical implantation or oblique implantation.

Preferably, the implantation of the metal ions in step (2) is aimed at either a local area of the surface of the insulator optical planar waveguide, or an entire area of the surface of the insulator optical planar waveguide.

Preferably, the implantation energy and dose of metal ions in step (2) are respectively controlled between 40-100 keV and 5×10 ¹⁶ to 8×10 ¹⁶ cm ⁻² , and the actual application values are determined according to a predetermined strategy.

The predetermined strategy includes: when the thickness of the insulator optical planar waveguide is 200-750 nm, the implantation energy and dose of the selected metal ions should make the maximum implantation depth of the metal ions approach but not exceed 1/5 of the thickness of the insulator optical planar waveguide, That is, 40-150nm; when the thickness of the insulator optical planar waveguide is greater than 750nm, the implantation energy and dose of the selected metal ions should make the maximum implantation depth of the metal ions approach but not exceed 150nm.

Preferably, the reactive ion beam etching technique in step (4) includes a cooling liquid process.

Preferably, the etching depth in step (4) is greater than or equal to the maximum implantation depth of metal ions.

The metal nanoparticle-insulator composite material grating coupler can be applied in the preparation of optical couplers, filters, beam splitters and deflectors in visible and/or near-infrared bands.

The beneficial effects of the present invention are:

Compared with the traditional insulator grating coupler, the metal nanoparticle-insulator composite material grating coupler disclosed by the present invention has higher coupling efficiency, and there is no phenomenon caused by free carrier absorption in the metal grating coupler. loss. Taking the Ag nanoparticle-SiO ₂ composite material grating coupler mentioned in the embodiment as an example, when the wavelength of the incident light is 650nm, its coupling efficiency is at least 3 times higher than that of the SiO ₂ grating coupler with the same structure. In addition, compared with the traditional grating coupler composed of one-dimensional coupling grating, the metal nanoparticle-insulator composite material grating coupler disclosed in the present invention adopts a two-dimensional orthogonal structure coupling grating, so it not only It is not sensitive to the polarization direction, and can achieve optical filtering, beam splitting and deflection with the help of guided wave formation and diffraction distortion while achieving optical coupling, which is very important for building functional integrated optical devices and for them The basic large-scale integrated optical circuit is of great significance.

Description of drawings:

Fig. 1 is a schematic diagram of a partial structure of a metal nanoparticle-insulator composite material grating coupler.

Fig. 2 is a schematic diagram of the preparation process of the metal nanoparticle-insulator composite material grating coupler.

Figure 3a shows the depth distribution of Ag nanoparticles formed after Ag ions are implanted into SiO ₂ planar waveguide.

Figure 3b is the surface morphology of the Ag nanoparticle-SiO ₂ composite grating coupler.

Figure 4a is the depth distribution of Cu nanoparticles formed after Cu ions implanted into _SiO2 planar waveguide.

Figure 4b is the surface morphology of the Cu nanoparticle-SiO ₂ composite grating coupler.

Fig. 5 is the transmission spectrum of the Ag nanoparticle-SiO ₂ composite grating coupler and the Cu nanoparticle-SiO ₂ composite grating coupler.

Fig. 6 is a schematic diagram of formation and control of guided waves.

In the figure: 1-metal nanoparticle-insulator composite material coupling grating, 2-insulator optical planar waveguide, 3-metal nanoparticle, 4-metal nanoparticle-insulator composite material modified layer, 5-photoresist mask layer, The surface of 6- _SiO2 optical planar waveguide, 7-Ag nanoparticles, 8-Ag nanoparticles- _SiO2 composite modified layer, 9-Cu nanoparticles, 10-Cu nanoparticles- _SiO2 composite modified layer, 11-Ag nanoparticle-SiO ₂ composite material grating coupler transmission spectrum, 12-Cu nanoparticle-SiO ₂ composite material grating coupler transmission spectrum, 13-incident light, 14-propagation direction of guided wave.

detailed description:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. The description in this part is for demonstration and explanation, and should not be regarded as a limitation of the technical content disclosed in the present invention.

The structure of the metal nanoparticle-insulator composite grating coupler in the present invention is shown in FIG. 1 , which is composed of a metal nanoparticle-insulator composite coupling grating 1 and an insulator optical planar waveguide 2 . The metal nanoparticle-insulator composite material coupling grating 1 is a two-dimensional orthogonal rectangular diffraction grating with a thickness of 40-150nm, located on the surface of the insulator optical planar waveguide 2 and formed by implanting metal ions into the metal nanoparticle-insulator composite material modification. In the active layer 4, there is no obvious interface with the insulator optical planar waveguide 2. The metal nanoparticle 3 in the metal nanoparticle-insulator composite material coupling grating 1 is one of the three metal nanoparticles of Ag, Cu and Au. The metal nanoparticle-insulator composite material coupling grating 1 has the same grating constant and duty cycle on the row and column, and the grating constant is 1.05 to 1.5 times the absorption wavelength of the metal nanoparticle surface plasmon resonance in the insulator optical planar waveguide 2, accounting for The void ratio is the ratio of the width of the metal nanoparticle-insulator composite material coupling grating 1 to the constant of the grating, which is controlled between 30% and 50%. The insulator optical planar waveguide 2 is a thin film or thin plate made of transparent solid insulating material in visible and/or near-infrared bands.

The metal nanoparticle-insulator composite material grating coupler described in the present invention is prepared according to the steps shown in Figure 2:

(1) selecting or preparing an insulator optical planar waveguide 2 with a certain thickness;

(2) Metal ions with a certain energy and dosage are injected into the insulator optical planar waveguide 2 in a certain way, and metal nanoparticles 3 with a certain depth distribution are formed in the near surface area of the insulator optical planar waveguide 2, that is, a layer with A metal nanoparticle-insulator composite material modification layer 4 with a certain thickness;

(3) Using electron beam lithography technology, a photoresist mask layer 5 with required two-dimensional coupling grating structure information is prepared on the surface of the insulator optical planar waveguide 2 implanted with metal ions;

(4) Relying on the modified metal nanoparticle-insulator composite material modification layer 4 formed on the surface of the insulator optical planar waveguide 2, it is etched by reactive ion beam etching technology, and the etching depth is 40-150nm, after subsequent glue removal treatment , to construct the desired two-dimensional metal nanoparticle-insulator composite coupling grating 1 .

In the step (2), the metal ion is one of the three metal ions of Ag, Cu and Au, and the implantation energy and dose of the metal ion are respectively 40-100keV and 5×10 ¹⁶ ～8×10 ¹⁶ cm ^-2 , the injection method is either vertical injection or oblique injection, and the injection area is either a partial surface of the insulator optical planar waveguide 2 or the entire surface of the insulator optical planar waveguide 2 . The actual metal ion implantation energy and dose can be determined within a given range according to a predetermined strategy through the following process: ①Select the material of the insulator optical planar waveguide, the metal ion to be implanted and the implantation method of the metal ion; ②Select an implant Energy, using SRIM (Stopping and Range of Ions in Matter) software to calculate, determine the corresponding sputtering yield Y, projected range R _p and range divergence △ R _p ; ③ select an injection dose, combined with the obtained Y, R _p and △R _p , calculate the depth distribution function G(z) of implanted metal ions, thereby determine the maximum implantation depth of metal ions; ④ If the calculated maximum implantation depth of metal ions does not meet the predetermined strategy, you should re-select Inject energy and dose until calculated results match predetermined strategy.

The predetermined strategy includes: when the thickness of the insulator optical planar waveguide 2 is 200-750 nm, the implantation energy and dose of the selected metal ions should make the maximum implantation depth of the metal ions approach but not exceed 1/5 of the thickness of the insulator optical planar waveguide 2, That is, 40-150nm; when the thickness of the insulator optical planar waveguide 2 is greater than 750nm, the implantation energy and dosage of the selected metal ions should make the maximum implantation depth of the metal ions close to but not exceed 150nm.

The specific form of the depth distribution function G(z) of implanted metal ions is:

In the formula, z is the depth relative to the immediate surface of the insulator optical planar waveguide 2, N is the atomic density of the material used in the insulator optical planar waveguide 2, D is the implanted dose of metal ions, and erf() is an error function.

The reactive ion beam etching technique in the step (4) includes a cooling liquid process, and the etching depth is greater than or equal to the maximum implantation depth of metal ions.

According to the steps shown in Figure 2, Ag nanoparticles-SiO ₂ composite grating couplers and Cu nanoparticles-SiO ₂ composite grating couplers were actually prepared. The main preparation parameters and descriptions are as follows: The surface size of SiO ₂ planar waveguide is about 20×20mm ² , with a thickness of about 0.5mm; both Ag and Cu ions are implanted at an angle of 45°, aiming at the entire surface of the SiO ₂ planar waveguide; according to the operating conditions of the implanter, combined with a predetermined strategy, the Ag and Cu ions The implantation energy is set at 90 and 60keV respectively, and the implantation dose is set at 6×10 ¹⁶ cm ^-2 ; the coupling grating adopts a two-dimensional orthogonal rectangular structure with a surface size of about 4×4mm ² and a thickness of about 100nm. The grating constants of both are 600nm, and the duty cycle is 30%. The grating constant of 600nm is about 1.45 times of the surface plasmon resonance absorption wavelength (~414nm) of the Ag nanoparticles in _SiO2 and the surface plasmon of Cu nanoparticles in _SiO2 . The resonance absorption wavelength (~564nm) is 1.06 times; the atmosphere used in the etching process is CHF ₃ and Ar, and the etching depth is about 100nm, which is greater than the maximum implantation depth of Ag and Cu ions in the SiO ₂ planar waveguide.

Figure 3a shows the depth distribution of Ag nanoparticles formed after Ag ions are implanted into the _SiO2 planar waveguide. It can be seen from the figure that the Ag nanoparticles 7 are approximately spherical and are mainly distributed 5.5 below the surface 6 of the _SiO2 planar waveguide. ~83.0nm region, it can be seen that the thickness of Ag nanoparticle-SiO ₂ composite modified layer 8 is about 77.5nm. The Ag nanoparticles 7 are clearly divided into three layers, the Ag nanoparticles in the upper and lower layers are relatively small, and the Ag nanoparticles in the middle layer are relatively large. Statistical results show that the average diameter of the Ag nanoparticles 7 is about 3.7nm. Using this average diameter, according to the measurement results of the absorption spectrum and the corresponding fitting calculations, it can be known that the Ag nanoparticles 7 account for the composite modified layer 8 The volume fraction is about 24%. Using the dielectric function of Ag, the average diameter and volume fraction of Ag nanoparticles and the dielectric constant of _SiO2 , according to the MG theory, the refractive index (i.e. the real part of the effective refractive index) and For the extinction coefficient, the wavelength of the incident light is taken as 650nm, and the calculated refractive index and extinction coefficient are 1.82 and 0.05, respectively. Figure 3b shows the surface morphology of the Ag nanoparticle-SiO ₂ composite grating coupler. For this grating coupler, when the wavelength of the incident light is 650nm, the refractive index contrast of the coupling grating is about 1.82, while The refractive index contrast of the SiO ₂ coupled grating with the same structure is only about 1.46, according to the theoretical research on the grating coupler by Ghizoni et al. The additional modulation of the refractive index contrast caused by the scattering of light by surface plasmons can also estimate that the coupling efficiency of the grating coupler is about 318% higher than that of the _SiO2 grating coupler with the same structure. Further, if Properly increasing the implantation dose of Ag ions, or adopting appropriate methods to suppress the self-sputtering during Ag ion implantation, the coupling efficiency can be further improved.

As shown in Figure 4a, the Cu nanoparticles 9 formed after Cu ion implantation into the SiO ₂ planar waveguide are also roughly spherical, and are mainly distributed in the depth region of 5.2-62.5 nm below the surface 6 of the SiO ₂ planar waveguide. The thickness of the particle-SiO ₂ composite modified layer 10 is about 57.3 nm. Compared with the Ag nanoparticles 7 in Fig. 3a, the size change of Cu nanoparticles 9 with depth is not very drastic, but it can also be roughly divided into three layers, the Cu nanoparticles in the upper and lower layers are relatively small, and the Cu nanoparticles in the middle layer Nanoparticles are relatively large. The statistical results show that the average diameter of Cu nanoparticles 9 is about 3.2 nm, which is slightly smaller than that of Ag nanoparticles 7 in Fig. 3a. Figure 4b shows the surface morphology of the Cu nanoparticle-SiO ₂ composite grating coupler, which is basically consistent with the results shown in Figure 3b, reflecting that electron beam lithography and reactive ion beam etching techniques can provide sufficiently high machining accuracy. Since after Cu ions are implanted into _SiO2 planar waveguide, besides Cu nanoparticles 9, Cu2O and _CuO nanoclusters can also be formed, so it is difficult to give Cu The volume fraction of nanoparticles 9 in the composite material modified layer 10, so it is impossible to evaluate the coupling efficiency of the Cu nanoparticles-SiO ₂ composite grating coupler shown in Fig. 4b. However, compared with For the SiO ₂ grating coupler with the same structure, it can still be expected that there is a large improvement in the coupling efficiency.

Figure 5 shows the transmission spectra of Ag nanoparticles-SiO ₂ composite grating coupler and Cu nanoparticle-SiO ₂ composite grating coupler. It can be seen from the figure that there are two obvious transmittance reduction bands in the transmission spectrum 11 of the Ag nanoparticle-SiO ₂ composite grating coupler, one is located near the wavelength of 414nm, which is derived from the Ag nanoparticle 7 (see Fig. 3a) surface plasmon resonance absorption, the other is located between the wavelength range of 620-880nm, this transmittance reduction band also exists in the transmission spectrum 12 of the Cu nanoparticle-SiO ₂ composite grating coupler, but the transmittance The reduction is relatively small. A transmittance reduction band caused by the surface plasmon resonance absorption of Cu nanoparticles 9 (see Fig. 4a) can also be found on the transmission spectrum 12 of the Cu nanoparticles-SiO ₂ composite grating coupler, which is located near 564 nm. For the transmittance reduction bands appearing between 620-880nm in the two groups of spectra, their generation can be attributed to the formation of guided waves, as shown in Figure 6. When the incident light 13 is vertically irradiated on the surface of the grating coupler, the ±1st-order diffracted light is introduced into the SiO ₂ planar waveguide because it can meet the phase matching condition, and then forms 4 guided waves, and the propagation directions 14 of the guided waves are respectively the x-axis (corresponding to the row of the coupling grating) and the positive and negative directions of the y-axis (corresponding to the column of the coupling grating). Since the prepared grating coupler adopts a coupling grating with a two-dimensional orthogonal structure, the formation of the guided wave is not sensitive to the polarization direction of the incident light 13. In addition, since the phase matching condition is selective to the wavelength of the incident light 13, Therefore, not all wavelengths of incident light 13 can be coupled into the SiO ₂ planar waveguide, which means that, using the formation of guided waves, the prepared grating coupler can not only achieve beam splitting of incident light 13, but also has a broadband The filtering effect is about 34.7% of the relative bandwidth. It is worth noting that when the incident angle is changed, the propagation direction 14 of part of the guided wave will also change due to diffraction distortion. For example, the negative deflection of the incident light 13 in the xz plane around the z-axis and the x-axis will cause the y-axis The two guided waves above are deflected in the positive direction of the x-axis in the xy plane, that is to say, with the help of the formation of guided waves and diffraction distortion, the prepared grating coupler can also realize light deflection.

The present invention is based on the commonly used insulator optical planar waveguide, adopts technologies such as metal ion implantation, electron beam lithography and ion beam etching, and reasonably selects the type of metal ion and implantation conditions, and properly designs the structure of the coupling grating. A high-efficiency two-dimensional grating coupler based on metal nanoparticles-insulator composites is constructed, which works in the visible and/or near-infrared bands. It is not only insensitive to the polarization direction of light, but also can realize optical coupling. , with the help of guided wave formation and diffraction distortion, the filtering, beam splitting and deflection of light can also be realized.

Claims (8)

1. A metal nanoparticle-insulator composite grating coupler, characterized in that: it is composed of a metal nanoparticle-insulator composite coupling grating and an insulator optical planar waveguide, wherein the metal nanoparticle-insulator composite coupling grating is a Two-dimensional orthogonal rectangular diffraction grating, with a thickness of 40-150nm, located in the modified layer formed by implanting metal ions on the surface of the insulator optical planar waveguide, and has no interface with the insulator optical planar waveguide; the metal nanoparticle-insulator The metal nanoparticle in the composite material coupling grating is one of the three metal nanoparticles of Ag, Cu and Au. 2. The metal nanoparticle-insulator composite material grating coupler according to claim 1, characterized in that: the metal nanoparticle-insulator composite material coupling grating has the same grating constant and duty cycle in rows and columns, The grating constant is 1.05 to 1.5 times the absorption wavelength of the metal nanoparticle surface plasmon resonance in the insulator optical planar waveguide, and the duty cycle is the width of the metal nanoparticle-insulator composite material coupling grating in the metal nanoparticle-insulator composite material and the grating The constant ratio is controlled between 30% and 50%. 3 . The metal nanoparticle-insulator composite grating coupler according to claim 1 , wherein the insulator optical planar waveguide is a thin film or thin plate made of transparent solid insulating material in visible and/or near-infrared bands. 4 . 4. A method for preparing the metal nanoparticle-insulator composite grating coupler according to claim 1, characterized in that the steps are as follows: (1) Select or prepare an insulator optical planar waveguide; (2) Choose one of the three metal ions of Ag, Cu and Au to inject into the insulator optical planar waveguide, and form a metal nanoparticle-insulator composite modified layer on the surface of the insulator optical planar waveguide. The implantation energy of the metal ions and dose are 40~100keV and 5×10 ¹⁶ ～8×10 ¹⁶ cm ^-2 , respectively, and the actual application value is determined according to the predetermined strategy; (3) Using electron beam lithography technology, a photoresist mask layer with the required two-dimensional coupling grating structure information is prepared on the surface of the insulator optical planar waveguide implanted with metal ions; (4) Relying on the modified layer of metal nanoparticles-insulator composite material formed on the surface of the insulator optical planar waveguide, it is etched by reactive ion beam etching technology, and the etching depth is 40-150nm. The desired two-dimensional metal nanoparticle-insulator composite coupling grating. 5. The preparation method according to claim 4, characterized in that: the implantation of the metal ions in step (2) is aimed at a local area of the surface of the insulator optical planar waveguide, or at the entire area of the surface of the insulator optical planar waveguide , the implantation method is either vertical implantation or oblique implantation. 6. The preparation method according to claim 4, characterized in that: the predetermined strategy in step (2) includes: when the thickness of the insulator optical planar waveguide is 200-750 nm, the implantation energy and dose of the selected metal ions should be Make the maximum implantation depth of metal ions close to but not exceed 1/5 of the thickness of the insulator optical planar waveguide, that is, 40-150nm; when the thickness of the insulator optical planar waveguide is greater than 750nm, the implantation energy and dose of the selected metal ions should The maximum implantation depth is close to but not exceeding 150nm. 7. The preparation method according to claim 4, characterized in that: the reactive ion beam etching technique in step (4) includes a cooling liquid process, and the etching depth is greater than or equal to the maximum implantation depth of metal ions. 8. The metal nanoparticle-insulator composite grating coupler according to claim 1, characterized in that: the grating coupler is used to prepare optical couplers, filters, beam splitters and deflector.