A surface plasmon waveguide and a preparation method thereof

Abstract

The present application discloses a surface plasmon waveguide and a preparation method thereof. The waveguide includes: a lower silver nanowire; an inner silica cladding covering the outside of the lower silver nanowire; a silicon cladding covering the outside of the inner silica cladding; an upper silver nanowire disposed above the silicon cladding, and there is a certain distance between the upper silver nanowire and the silicon cladding; an outer silica cladding commonly covering the outside of the silicon cladding and the upper silver nanowire. The waveguide of the present application simultaneously has a long transmission distance, a small effective mode area, and an ultra-high quality factor. Its effective mode area is 0.01, the transmission length can reach 600 μm, and the quality factor of the waveguide can be as high as 4000. In addition, the cross-sectional area of the waveguide is only 500 nm × 500 nm, which makes it possible to perform optical operations in the sub-wavelength range.

Description

Technical Field

[0001] This application relates to the technical field of optoelectronic devices, and particularly to a surface plasmon waveguide and a preparation method thereof. Background Art

[0002] With the rapid development of optoelectronic integrated systems, the performance requirements for optical devices are also getting higher and higher. As the core component of optoelectronic integrated systems, waveguides not only require a long transmission distance, but also a very small effective mode area to promote the integration and miniaturization of optoelectronic systems. In this case, designing sub-wavelength waveguides with excellent performance is a huge challenge.

[0003] Traditional waveguides have a long transmission distance, but poor optical confinement, which is not conducive to the design of small-sized devices. Surface plasmon polaritons (SPPs) have good confinement properties and can confine light within the sub-wavelength size range, which is conducive to the design of small-sized or even sub-wavelength optoelectronic devices. However, the transmission length of surface plasmon polaritons is small, which is not conducive to optoelectronic integration. By combining traditional waveguides with surface plasmon polaritons, hybrid waveguides with a long transmission distance and a small effective mode area can be designed. Currently, there are many types of SPPs hybrid waveguides, and their performance has also been greatly improved. However, with the rapid development of optoelectronic integrated systems, the requirements for waveguide performance are getting higher and higher, and new ways need to be found to obtain higher-performance long-range and highly confined waveguides. Although a large number of researchers have been engaged in research related to hybrid waveguides in recent years, and their mode area has been reduced a lot, the transmission length still remains at the level of dozens of micrometers, and the sizes of existing hybrid waveguides are generally large. Summary of the Invention

[0004] Embodiments of this application provide a surface plasmon waveguide and a preparation method thereof, which are used to solve the problems of short transmission length and large size of hybrid waveguides in the prior art.

[0005] On the one hand, embodiments of this application provide a surface plasmon waveguide, including:

[0006] Lower silver nanowires;

[0007] Inner silica cladding, covering the outside of the lower silver nanowires;

[0008] Silica cladding, covering the outside of the inner silica cladding;

[0009] Upper silver nanowires, arranged above the silica cladding, and there is a certain distance between the upper silver nanowires and the silica cladding;

[0010] Outer silica cladding, jointly covering the outside of the silica cladding and the upper silver nanowires.

[0011] On the other hand, an embodiment of the present application also provides a method for preparing a surface plasmon waveguide, including:

[0012] Preparing a semiconductor silicon nanotube;

[0013] Etching the semiconductor silicon nanotube and depositing a lower silver nanowire inside the etched semiconductor silicon nanotube;

[0014] Etching the semiconductor silicon nanotube again and depositing an inner silica cladding inside the semiconductor silicon nanotube after the second etching, wherein the inner silica cladding coats the outside of the lower silver nanowire, and the remaining part of the semiconductor silicon nanotube forms a silicon cladding;

[0015] Depositing a silica spacer layer with a certain thickness on the upper part of the silicon cladding;

[0016] Depositing an upper silver nanowire on the upper part of the silica spacer layer;

[0017] Preparing an outer silica cladding to coat the silicon cladding and the upper silver nanowire together.

[0018] A surface plasmon waveguide and a preparation method thereof in the present application have the following advantages:

[0019] It has both a long transmission distance and a small effective mode area, as well as an ultra-high quality factor. Its effective mode area is 0.01, the transmission length can reach 600 μm, and the quality factor of the waveguide can be as high as 4000. In addition, the cross-sectional area of the waveguide is only 500 nm × 500 nm, which makes it possible to perform optical operations in the sub-wavelength range. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a schematic cross-sectional structure diagram of a surface plasmon waveguide provided by an embodiment of the present application;

[0022] Figure 2 It is a schematic diagram of the simulated electric field of a surface plasmon waveguide provided by an embodiment of the present application.

[0023] Explanation of the reference numerals in the drawings: 100 - lower silver nanowire, 200 - inner silica cladding, 300 - silicon cladding, 400 - upper silver nanowire, 500 - outer silica cladding. Detailed implementation mode

[0024] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0025] Figure 1 It is a schematic structural diagram of a surface plasmon waveguide provided by an embodiment of the present application. An embodiment of the present application provides a surface plasmon waveguide, including:

[0026] Lower silver nanowire 100;

[0027] Inner silica cladding 200, covering the outside of the lower silver nanowire 100;

[0028] Silicon cladding 300, covering the outside of the inner silica cladding 200;

[0029] Upper silver nanowire 400, arranged above the silicon cladding 300, and there is a certain distance between the upper silver nanowire 400 and the silicon cladding 300;

[0030] Outer silica cladding 500, jointly covering the outside of the silicon cladding 300 and the upper silver nanowire 400.

[0031] Exemplarily, the lower silver nanowire 100 may adopt a cylindrical structure. Accordingly, the inner silica cladding 200 and the silicon cladding 300 also adopt a cylindrical structure, and the lower silver nanowire 100, the inner silica cladding 200 and the silicon cladding 300 are all coaxial, that is, the thickness of the inner silica cladding 200 outside the lower silver nanowire 100 remains the same, and the thickness of the silicon cladding 300 outside the inner silica cladding 200 also remains the same.

[0032] In the embodiment of the present application, the radius of the lower silver nanowire 100 is r Ag , the thickness of the inner silica cladding 200 is t SiO2 , the thickness of the silicon cladding 300 is t Si , the radius of the upper silver nanowire 400 is R Ag , the lower silver nanowire 100, the inner silica cladding 200 and the silicon cladding 300 form a hybrid waveguide, and the distance between the hybrid waveguide and the upper silver nanowire 400 is g.

[0033] The embodiment of the present application also provides a preparation method of a surface plasmon waveguide, and the method includes the following steps:

[0034] S100, prepare a semiconductor silicon nanotube.

[0035] Exemplarily, a metal cluster-catalyzed vapor-liquid-solid (VLS) growth mechanism method can be adopted to prepare semiconductor silicon nanotubes, and the outer diameter of the semiconductor silicon nanotubes is t SiO2 +t Si +r Ag , and its inner diameter is less than r Ag .

[0036] The hybrid waveguide in this application is fabricated based on a silicon-on-insulator (SOI) wafer, and the thickness of the buried oxide layer of the SOI wafer is generally 2 μm

[0037] S110, etch the semiconductor silicon nanotubes, and deposit the lower silver nanowire 100 inside the etched semiconductor silicon nanotubes

[0038] Exemplarily, when preparing the lower silver nanowire 100, the inner wall of the semiconductor silicon nanotubes can be etched first to make its inner diameter greater than or at least equal to the diameter r of the lower silver nanowire 100 Ag , and then the lower silver nanowire 100 is deposited inside the etched semiconductor silicon nanotubes by sputtering or focused ion beam (FIB) method, so that the radius of the lower silver nanowire 100 is r Ag .

[0039] S120, etch the semiconductor silicon nanotubes again, and deposit the inner silica cladding 200 inside the semiconductor silicon nanotubes after the second etching, wherein the inner silica cladding 200 covers the outside of the lower silver nanowire 100, and the remaining part of the semiconductor silicon nanotubes forms the silicon cladding 300

[0040] Exemplarily, after the deposition of the lower silver nanowire 100 is completed, a space with a thickness of t Si can be etched on the inner wall of the semiconductor silicon nanotubes, and then the silica cladding 200 with a thickness of t Si is deposited in the etched space by sputtering or focused ion beam (FIB) method again. Since the outer diameter of the semiconductor silicon nanotubes is t SiO2 +t Si +r Ag , after sequentially depositing the lower silver nanowire 100 with a radius of r Ag and the silica cladding 200 with a thickness of t Si , the remaining thickness is t Si , so the thickness of the silicon cladding 300 is t Si .

[0041] S130, deposit a silica spacer layer with a certain thickness on the upper part of the silicon cladding 300

[0042] Exemplarily, the thickness of the silica spacer is g.

[0043] S140, deposit the upper silver nanowires 400 on the upper part of the silica spacer.

[0044] Exemplarily, the upper silver nanowires 400 can be deposited on the upper part of the silica spacer by means of ion beam etching and sputtering.

[0045] S150, prepare the outer silica cladding 500, and the outer silica cladding 500 co - coats the silicon cladding 300 and the upper silver nanowires 400.

[0046] Exemplarily, the outer silica cladding 500 can be prepared by using plasma - enhanced chemical vapor deposition (PECVD) technology.

[0047] Experimental simulation shows

[0048] Set the device size to R Ag = 30 nm, g = 5 nm, t Si = 35 nm, r Ag = 25 nm, t SiO2 = 5 nm, and the incident wavelength is 1550 nm. As can be seen from Figure 2, due to the double coupling of the surface plasmon mode and the silicon waveguide mode, the electric field is mainly concentrated in the silica spacer region between the upper silver nanowires 400 and the silicon cladding 300, and the electric field distribution in other regions of this structure is extremely weak. Therefore, it can be concluded that the localization of this waveguide is very good. By inserting calculation formulas in the software, the values of the transmission length, effective mode area, and quality factor of the waveguide obtained from the electric field distribution results are 600 μm, 0.001, and 4000 respectively.

[0049] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0050] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these changes and modifications.

Claims

1. A surface plasmon waveguide, characterized in that, Comprising: Lower silver nanowire (100); Inner silica cladding (200), coated outside the lower silver nanowire (100); Silicon cladding (300), coated outside the inner silica cladding (200); Upper silver nanowire (400), disposed above the silicon cladding (300), and there is a certain distance between the upper silver nanowire (400) and the silicon cladding (300); Outer silica cladding (500), commonly coated outside the silicon cladding (300) and the upper silver nanowire (400).

2. A preparation method of a surface plasmon waveguide, characterized in that Including the following steps: Preparing a semiconductor silicon nanotube; Etching the semiconductor silicon nanotube and depositing a lower silver nanowire (100) inside the etched semiconductor silicon nanotube; Etching the semiconductor silicon nanotube again and depositing an inner silica cladding (200) inside the semiconductor silicon nanotube after the second etching, wherein the inner silica cladding (200) is coated outside the lower silver nanowire (100), and the remaining part of the semiconductor silicon nanotube forms a silicon cladding (300); Depositing a silica spacer layer with a certain thickness on the upper part of the silicon cladding (300); Depositing an upper silver nanowire (400) on the upper part of the silica spacer layer; Preparing an outer silica cladding (500), and coating the silicon cladding (300) and the upper silver nanowire (400) together with the outer silica cladding (500).

3. The preparation method of a surface plasmon waveguide according to claim 2, characterized in that, The semiconductor silicon nanotube is prepared by a metal cluster catalyzed vapor-liquid-solid growth mechanism method.

4. The preparation method of a surface plasmon waveguide according to claim 2, characterized in that The lower silver nanowire (100) is deposited inside the etched semiconductor silicon nanotube by sputtering or focused ion beam method.

5. The preparation method of a surface plasmon waveguide according to claim 2, characterized in that, The upper silver nanowire (400) is deposited on the upper part of the silica spacer layer by ion beam etching and sputtering method.

6. The preparation method of a surface plasmon waveguide according to claim 2, characterized in that, The outer silica cladding (500) is prepared by plasma enhanced chemical vapor deposition technology.

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