TM-pass polarization filter based on air slot auxiliary mixed plasmon waveguide

Abstract

The invention discloses a TM-pass polarization filter based on an air slot auxiliary mixed plasmon waveguide, and belongs to the technical field of photon integrated circuits. Comprising a substrate, a supporting layer, a high-refractive-index waveguide region, a spacing layer and a metal layer, the high-refractive-index waveguide area is arranged in the middle of the upper surface of the substrate, and the supporting layers are oppositely arranged on the two sides of the upper surface of the substrate; the spacing layer and the metal layer are sequentially arranged at the top of the supporting layer and are supported above the high-refractive-index waveguide region through the supporting layer; the high-refractive-index waveguide region comprises an input silicon waveguide, a first mode conversion region, an air slot auxiliary mixed plasmon waveguide, a second mode conversion region and an output silicon waveguide which are connected in sequence and are consistent in width and height; a rectangular air slot is formed in the middle of the air slot auxiliary mixed plasmon waveguide in a penetrating manner, and trapezoidal air slots are formed in the middle of the first mode conversion region and the middle of the second mode conversion region in a penetrating manner. According to the TM-pass polarizer, high-performance integration of the TM-pass polarizer in an ultra-compact size is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of photonic integrated circuits, and in particular relates to a TM-pass polarization filter based on an air slot-assisted hybrid plasmon waveguide. Background Art

[0002] Silicon-based photonic integrated circuits (PICs) have become a core platform in the field of optical communications and sensing due to their high refractive index contrast, CMOS process compatibility, and submicron integration capabilities. However, the inherent geometric birefringence effect of silicon waveguides leads to significant polarization sensitivity, which needs to be compensated by polarization diversity technology.

[0003] The existing polarizers generally have the following problems: 1. The traditional solution requires a length of tens to hundreds of microns, and the silicon-based shallow etched waveguide requires a longer waveguide length to effectively attenuate non-target polarization modes. Invention patent CN110095840A discloses a silicon-based shallow etched waveguide polarizer and its preparation method. The device length reaches 46μm, and the extinction ratio can be maintained above 15.24dB. The spectral bandwidth is very narrow, only 26nm. 2. Graphene-based polarizers face some uncertainties in experiments, such as the shape, size, number of layers and purity of graphene. Invention patent CN110133799A discloses a graphene-based waveguide integrated polarization light coupler and its manufacturing method. The patent reaches a length of 150μm, which is not conducive to the demand for high integration. 3. Polarizers based on subwavelength gratings can place unwanted modes in a radiation state or Bragg reflection zone by periodically arranging patterns, but this structure often sacrifices device length. Invention patent CN101738679A discloses a Bragg grating filter based on a slot waveguide, the size of which is about 100 μm. The above solution lacks compactness and it is difficult to control the size below 20 μm, and there is also a problem of high loss. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a TM-pass polarization filter based on an air slot assisted hybrid plasmon waveguide, which realizes high-performance integration of a TM-pass polarizer in an ultra-compact size and solves the problems of large size, high loss and limited bandwidth of the polarizer.

[0005] The present invention provides the following technical solutions: Provided is a TM-pass polarization filter based on an air slot-assisted hybrid plasmon waveguide, comprising a substrate, a support layer, a high-refractive-index waveguide region, a spacer layer and a metal layer; the high-refractive-index waveguide region is arranged at the middle position of the upper surface of the substrate, and the support layers are relatively arranged on both sides of the upper surface of the substrate, and the height is greater than the high-refractive-index waveguide region; the spacer layer and the metal layer are sequentially arranged on the top of the support layer from bottom to top, and are supported above the high-refractive-index waveguide region by the support layer; the air between the high-refractive-index waveguide region and the metal layer serves as a low-refractive-index layer; the high-refractive-index waveguide region comprises an input silicon waveguide, a first mode conversion region, an air slot-assisted hybrid plasmon waveguide, a second mode conversion region and an output silicon waveguide, which are sequentially connected and have the same width and height; a rectangular air slot is penetrated in the middle of the air slot-assisted hybrid plasmon waveguide, and a trapezoidal air slot is penetrated in the middle of both the first mode conversion region and the second mode conversion region, and the width of the rectangular air slot is consistent with the longest width of the trapezoidal air slot.

[0006] As an optional technical solution of the present invention, the input silicon waveguide and the output silicon waveguide have the same size.

[0007] As an optional technical solution of the present invention, the length of the substrate is equal to the sum of the lengths of the input silicon waveguide, the first mode conversion region, the air slot assisted hybrid plasmon waveguide, the second mode conversion region and the output silicon waveguide.

[0008] As an optional technical solution of the present invention, the material of the support layer is ZnO, and the material of the substrate is SiO 2 The material of the high refractive index waveguide area is Si, and the material of the spacer layer is Si 3 N 4 , the material of the metal layer is Ag.

[0009] As an optional technical solution of the present invention, the length of the air slot assisted hybrid plasmon waveguide is set to 3 μm-20 μm, and the height is set to 380 nm-420 nm.

[0010] As an optional technical solution of the present invention, the height of the metal layer is set to 80nm~150nm, and the height of the spacer layer is set to 10nm~20nm.

[0011] As an optional technical solution of the present invention, the height of the low refractive index layer is 30nm~80nm.

[0012] As an optional technical solution of the present invention, the width of the trapezoidal air grooves is set to 50nm~200nm.

[0013] As an optional technical solution of the present invention, the air slot assisted hybrid plasmon waveguide includes two silicon cores of the same size, and the silicon cores are arranged on two sides of a rectangular air slot opposite to each other.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a TM-pass polarization filter based on an air slot-assisted hybrid plasmon waveguide, which enhances the selective suppression of TE / TM modes by introducing a rectangular air slot, combines a first mode conversion region and a second mode conversion region to reduce loss, thereby achieving high-performance integration in an ultra-compact size and solving the problems of large polarizer size, high loss and limited bandwidth; at the same time, the length of the air slot-assisted hybrid plasmon waveguide can be flexibly selected to meet different application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is an xyz three-dimensional schematic diagram of a TM-pass polarization filter based on an air slot-assisted hybrid plasmon waveguide in an embodiment of the present invention; Figure 2 is an xy cross-sectional schematic diagram of a TM-pass polarization filter based on an air slot-assisted hybrid plasmon waveguide in an embodiment of the present invention; Figure 3 is a schematic xz cross-sectional view of a TM-pass polarization filter based on an air slot-assisted hybrid plasmon waveguide in an embodiment of the present invention; Figure 4 Schematic diagram of the xy cross-sectional field distribution of the air slot assisted hybrid plasmon waveguide when the incident wavelength λ=1550nm in an embodiment of the present invention; Figure 5 is L in the embodiment of the present invention c1 = Schematic diagram of the change of polarizer performance in the range of 0nm~4000nm; Figure 6 is L in the embodiment of the present invention c2 = Schematic diagram of the change of polarizer performance in the range of 0nm~4000nm; Figure 7 is L in the embodiment of the present invention n = Schematic diagram of the change of polarizer performance in the range of 0μm ~20μm; Figure 8 It is a schematic diagram of the spectral response characteristics of the polarizer in the λ=1400nm~1800nm ​​band in an embodiment of the present invention.

[0016] Marked in the figure are: 1, substrate, 2, support layer, 3, high refractive index waveguide region, 4, spacer layer, 5, metal layer, 301, input silicon waveguide, 302, first mode conversion region, 303, air slot assisted hybrid plasmon waveguide, 304, second mode conversion region, 305, output silicon waveguide. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0018] Example 1 This embodiment provides a TM pass polarization filter based on an air slot assisted hybrid plasmon waveguide. Figure 1-Figure 3 As shown, it includes a substrate 1, a support layer 2, a high refractive index waveguide region 3, a spacer layer 4 and a metal layer 5.

[0019] The high refractive index waveguide region 3 is arranged in the middle position of the upper surface of the substrate 1, and the support layer 2 is relatively arranged on both sides of the upper surface of the substrate 1, and the height is greater than the high refractive index waveguide region 3; the spacer layer 4 and the metal layer 5 are arranged on the top of the support layer 2 from bottom to top, and are supported above the high refractive index waveguide region by the support layer 2; the air between the high refractive index waveguide region 3 and the metal layer 5 serves as a low refractive index layer in a localized TM mode, and the refractive index is 1.

[0020] The high refractive index waveguide region 3 includes an input silicon waveguide 301, a first mode conversion region 302, an air slot assisted hybrid plasmon waveguide 303, a second mode conversion region 304 and an output silicon waveguide 305 which are connected in sequence and have the same width and height; a rectangular air slot is provided through the middle of the air slot assisted hybrid plasmon waveguide 303, and a trapezoidal air slot is provided through the middle of both the first mode conversion region 302 and the second mode conversion region 304, and the width of the rectangular air slot is consistent with the longest width of the trapezoidal air slot.

[0021] Furthermore, the first mode conversion region 302 , the air slot assisted hybrid plasmon waveguide 303 , and the second mode conversion region 304 are used as polarization zones.

[0022] Furthermore, the input silicon waveguide 301 and the output silicon waveguide 305 have the same size. In this embodiment, the width w of the input silicon waveguide 301 and the output silicon waveguide 305 is si The thickness is 400nm, the height is 400nm, and the length is 800nm.

[0023] Furthermore, the length of the substrate 1 is equal to the sum of the lengths of the input silicon waveguide 301, the first mode conversion region 302, the air slot assisted hybrid plasmon waveguide 303, the second mode conversion region 304 and the output silicon waveguide 305. In this embodiment, the substrate width is 2500nm, the substrate height is 1μm, and the substrate length is L in +L out +L n +L c1 +Lc2 .

[0024] Furthermore, the material of the support layer 2 is ZnO, and the material of the substrate 1 is SiO 2 The material of the high refractive index waveguide region 3 is Si, and other materials with higher refractive index can also be selected. The refractive index of Si is 3.455. The material of the spacer layer 4 is Si 3 N 4 , the material of the metal layer 5 is Ag.

[0025] Further, the length of the air slot assisted hybrid plasmon waveguide 303 is set to 3 μm~20 μm, the height is set to 380 nm~420 nm, the height is preferably 400 nm in this embodiment, and the width is set to 400 nm in this embodiment, and the length of the air slot assisted hybrid plasmon waveguide is flexibly selected to meet different application requirements. The air slot assisted hybrid plasmon waveguide 303 includes two silicon cores of the same size, which are relatively arranged on both sides of the rectangular air slot, and the width of the silicon core is 100 nm.

[0026] Furthermore, the height of the metal layer 5 is set to 80nm-150nm, preferably 100nm in this embodiment, and the height of the spacer layer 4 is set to 10nm-20nm, preferably 15nm in this embodiment.

[0027] Furthermore, the height of the low refractive index layer is 30 nm to 80 nm, and is preferably 50 nm in this embodiment.

[0028] Furthermore, the width of the trapezoidal air slots is set to 50 nm to 200 nm. 1 =50nm linearly increases to g 2 = 200 nm, the width of the trapezoidal air slot in the second mode conversion region 304 is g 2 =200nm linearly reduced to g 1 =50nm. The trapezoidal air slot is used for the input silicon waveguide 301 and the output silicon waveguide 305 to perform adiabatic mode conversion.

[0029] In this embodiment, the length L of the first mode conversion region 302 is c1 =0.8 μm, the length L of the second mode conversion region 304 c2 =2μm.

[0030] In this embodiment, the width of the rectangular air groove is g2=200 nm, and the height is 400 nm.

[0031] Example 2 Based on Example 1, this example uses the above filter to conduct experiments to verify the filter performance under various parameters.

[0032] (1) When the incident wavelength λ = 1550nm, the above filter is used to conduct experiments. The xy cross-sectional field distribution diagram of the air slot-assisted hybrid plasmon waveguide is shown in Figure 4 As shown, it can be seen from the figure that the TM hybrid plasmon mode is well confined in the low refractive index region, and the TE mode leaks into the substrate.

[0033] (2) Let the length of the first mode conversion region be L c1 Changing from 0nm to 4000nm while maintaining the air slot-assisted hybrid plasmon waveguide length L n The length of the second mode conversion region is 3 μm, and the length of the second mode conversion region is 0 nm. The extinction ratio (PER) of the polarizer and the insertion loss (IL TM ) and the transmittance of the TE mode (T TE ).like Figure 5 As shown, in L c1 = In the range of 0nm~4000nm, select L c1 =800nm ​​is optimal, which can achieve the best balance between insertion loss optimization and device compactness. At this time, the filter converts the light field distribution in a nearly adiabatic manner, thereby reducing IL TM .

[0034] (3) Let the length of the second mode conversion region be L c2 The length of the air slot-assisted hybrid plasmon waveguide is kept at 3 μm while the length of the first mode conversion region is changed within the range of 0 nm to 4000 nm. c1 =800nm, the extinction ratio (PER) of the polarizer and the insertion loss (IL TM ) and the transmittance of the TE mode (T TE ).like Figure 6 As shown, in L c2 =0nm~4000nm, although it can still be achieved by increasing L c2 To improve PER, but considering the integration of the device, L is selected c2 =2000nm is optimal.

[0035] (4) Let the length of the air slot-assisted hybrid plasmon waveguide be L n By changing the length of the first mode conversion region in the range of 0μm~20μm and keeping the length of the second mode conversion region at 800nm ​​and 2000nm, the extinction ratio (PER) and insertion loss (IL) of the polarizer are obtained. TM ) and the transmittance of the TE mode (TTE ).like Figure 7 As shown, in L n = 0μm~20μm, L n The increase in L can significantly improve PER by extending the TE mode leakage path, and L can be dynamically optimized according to the application scenario requirements. n .

[0036] (5) Maintaining the incident wavelength λ in the 1400-1800 nm band, the length L of the air slot-assisted hybrid plasmon waveguide is obtained. n The extinction ratio (PER) and insertion loss (IL) of the polarizer under TM ),like Figure 8 shown.

[0037] In summary, the total length of the polarization zone is 5.8 μm (L c1 =0.8μm, L n =3μm, L c2 =2μm), at λ=1550nm, the insertion loss is 0.286dB, the extinction ratio is 20.02dB, and the bandwidth is 110nm (IL TM <0.41dB, PER>18.9dB); total length of polarization zone 11.8μm (L c1 =0.8μm, L n =9μm, L c2 =2μm), at λ=1550nm, the extinction ratio is improved to 30.64dB, the insertion loss is maintained at 0.409dB, and the bandwidth is extended to 324nm (IL TM <1dB, PER>26dB); total length of polarization zone 17.8μm (L c1 =0.8μm, L n =15μm, L c2 =2μm), at λ=1550nm, the extinction ratio is improved to 40.6dB, the insertion loss is maintained at 0.49dB, and the bandwidth is 295nm (IL TM <1dB, PER>29dB). That is, by flexibly selecting L n It offers a wide range of selectivity for a variety of applications, combining compactness with broad spectral performance.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A TM pass polarization filter based on an air slot assisted hybrid plasmon waveguide, characterized in that: It comprises a substrate (1), a support layer (2), a high refractive index waveguide region (3), a spacer layer (4) and a metal layer (5); The high refractive index waveguide region (3) is arranged in the middle of the upper surface of the substrate (1); the support layer (2) is arranged on both sides of the upper surface of the substrate (1) and has a height greater than that of the high refractive index waveguide region (3); the spacer layer (4) and the metal layer (5) are arranged on the top of the support layer (2) in order from bottom to top, and are supported above the high refractive index waveguide region by the support layer (2); the air between the high refractive index waveguide region (3) and the metal layer (5) serves as a low refractive index layer; The high refractive index waveguide region (3) comprises an input silicon waveguide (301), a first mode conversion region (302), an air slot-assisted hybrid plasmon waveguide (303), a second mode conversion region (304), and an output silicon waveguide (305) which are connected in sequence and have the same width and height; a rectangular air slot is provided through the middle of the air slot-assisted hybrid plasmon waveguide (303); a trapezoidal air slot is provided through the middle of both the first mode conversion region (302) and the second mode conversion region (304); and the width of the rectangular air slot is consistent with the longest width of the trapezoidal air slot.

2. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The input silicon waveguide (301) and the output silicon waveguide (305) have the same size.

3. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The length of the substrate (1) is equal to the sum of the lengths of the input silicon waveguide (301), the first mode conversion region (302), the air slot assisted hybrid plasmon waveguide (303), the second mode conversion region (304) and the output silicon waveguide (305).

4. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The material of the support layer (2) is ZnO, the material of the substrate (1) is SiO2, the material of the high refractive index waveguide region (3) is Si, the material of the spacer layer (4) is Si3N4, and the material of the metal layer (5) is Ag.

5. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The length of the air slot-assisted hybrid plasmon waveguide (303) is set to 3 μm to 20 μm, and the height is set to 380 nm to 420 nm.

6. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The height of the metal layer (5) is set to 80 nm to 150 nm, and the height of the spacer layer (4) is set to 10 nm to 20 nm.

7. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The height of the low refractive index layer is 30nm~80nm.

8. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The width of the trapezoidal air slots is set to 50nm~200nm.

9. The TM pass polarization filter based on air slot assisted hybrid plasmon waveguide according to claim 1, characterized in that: The air slot assisted hybrid plasmon waveguide (303) comprises two silicon cores of the same size, and the silicon cores are arranged oppositely on two sides of a rectangular air slot.

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