Electrically tunable nanobeam cavity optical filter

Abstract

This invention discloses an electrically tunable nanobeam cavity filter, which mainly solves the problems of large size, high loss, high power consumption, and slow modulation speed of existing tunable optical filters. It adopts a vertical structure composed of a substrate (1), a cladding (2), a waveguide (3), and an electrically modulated coupling region (4). The electrically modulated coupling region includes a resonant cavity (41), a top electrode (42), and a bottom electrode (43). The resonant cavity (41) includes a three-layer nanobeam cavity structure with nano-array vias of different sizes. The second nanobeam cavity uses hafnium zirconium oxide or aluminum scandium nitride materials. The cladding is divided into upper and lower layers, with the upper cladding material being silicon dioxide or air. The bottom electrode is located at both ends above the first nanobeam cavity layer, and the top electrode is located at both ends above the third nanobeam cavity layer. This invention significantly reduces the size and power consumption of the optical filter, accelerates the modulation speed, and improves the integration of the filter, making it suitable for on-chip optical interconnects and space optical communication.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic device technology, and specifically relates to a nanobeam cavity optical filter that can be used for wavelength selection, optical amplifier noise filtering, optical multiplexing, and optical demultiplexing. Background Technology

[0002] Driven by the market, wavelength division multiplexing (WDM) technology faces increasing demands for transmitted information due to the commercialization of optical fibers, requiring more channels to be accommodated in the C-band. Optical filters utilize optical methods and components to filter optical signals in optical fiber communication technology. High quality factors and small half-width at half-maximum (FWHM) of optical filters are essential to accommodate more channels in the C-band. Optical add-drop filters are crucial for WDM systems, significantly increasing the capacity of optical communication networks. For applications in integrated photonic circuits, in-plane compact devices are more ideal. Microring resonators utilizing phase-matching effects are widely used as compact channel-down filters. However, there is a trade-off between the size and quality factor of ring resonators, limiting their size to a few micrometers. Furthermore, ring resonant modes have a limited free spectral range (FSR), which can be overcome by cascading multiple rings, further increasing the device's footprint. Tunable filters commonly use microring and Mach-Zehnder (MZ) structures, but these structures suffer from high losses, large size, and difficulties in adjustment and control.

[0003] Ferroelectric materials have extremely wide applications in the electronics and information industry. For example, random access memory (RAM), ferroelectric tunnel junction memory (FMT), optoelectronic modulators, and piezoelectric transducers all require ferroelectric materials. Ferroelectric materials exhibit spontaneous polarization within a certain temperature range. Because the centers of positive and negative charges in the ferroelectric lattice do not coincide, an electric dipole moment can be generated even without an external electric field, and its spontaneous polarization can change direction under the influence of an external electric field. In 2020, the concept of ferroelectric doped Fe-ED was proposed, which involves polarizing a ferroelectric material through electrical excitation, and then using the residual polarization charge P on the ferroelectric surface... r Doping semiconductors alters the distribution of charge carriers within them. This method provides a low-power, non-volatile doping approach.

[0004] A photonic crystal is an artificial microstructure composed of periodically arranged dielectrics of different refractive indices. Introducing defects or disorder into a photonic crystal, thus disrupting its periodicity, will create a photonic crystal resonator. The photonic crystal nanobeam cavity (PCNC) is a typical one-dimensional photonic crystal resonator. PCNCs are small in size, relatively easy to fabricate, and also possess a high quality factor and small mode volume, making them widely used. Recently, due to their excellent characteristics—ultra-small size and convenient integration with bus waveguides—PCNCs have been widely used as optoelectronic modulators.

[0005] In 2019, the Institute of Semiconductors, Chinese Academy of Sciences, proposed a narrowband optical filter based on a microring resonator in patent application number 201910990989.8. The filter includes an optical waveguide and three microring structures. A broadband optical signal to be processed is input through the optical waveguide, and the microring structures filter the broadband optical signal in the input waveguide, achieving a narrow bandwidth and high roll-off rate, meeting the requirements of microwave photonic signal processing in the field of optical fiber communication. However, because this filter uses three microring structures, it occupies a large area, making integration difficult. Furthermore, since no modulation structure is used, the device cannot achieve tuning functionality.

[0006] In 2021, China University of Geosciences proposed an ultra-narrow bandwidth tunable optical filter based on a high-Q microring in patent application number 202111115068.0. It includes a silicon-based high-quality Q-factor microring structure, a Mach-Zehnder interferometer (MZI), and heating electrodes. By manipulating the heating electrodes, the filter bandwidth and center wavelength can be tunable while maintaining a high extinction ratio. This filter has a large footprint due to the use of both the microring and the Mach-Zehnder interferometer; furthermore, because the microring acts as a resonator using the phase-matching principle, periodic transmission peaks appear, affecting the filtering effect; and the tuning method used in this filter is thermal modulation, resulting in slow modulation speed and high power consumption.

[0007] The purpose of this invention is to address the shortcomings of the prior art by proposing a tunable nanobeam cavity filter. This filter uses ferroelectric doping as a tuning method and a nanobeam cavity structure as a resonant cavity. The resonant wavelength of the nanobeam cavity can be tuned by changing the carrier distribution within the nanobeam cavity. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing an electrically tunable nanobeam cavity filter to reduce the filter's size, loss, and power consumption, while improving sensitivity and modulation speed, thus facilitating integrated commercialization.

[0009] The technical solution of this invention is implemented as follows:

[0010] 1. An electrically tunable nanobeam cavity optical filter, comprising: a silicon substrate, a waveguide, a cladding, and an electrically modulated coupling region, characterized in that:

[0011] The cladding is configured as two layers, namely a lower cladding and an upper cladding, and the material of the upper cladding is silicon dioxide or air;

[0012] The electrical modulation coupling region is located on the upper part of the lower cladding and includes a resonant cavity, a bottom electrode, and a top electrode.

[0013] The resonant cavity comprises a three-layer structure from bottom to top: a first nanobeam cavity, a second nanobeam cavity, and a third nanobeam cavity. These three nanobeam cavities are provided with nano-array through holes of different sizes, and the second nanobeam cavity (412) is made of hafnium zirconium oxide or aluminum scandium nitrogen material.

[0014] The bottom electrode is located at both ends above the first layer of nanobeam cavity;

[0015] The top electrode is located at both ends above the third layer of nanobeam cavity.

[0016] Furthermore, the nanoarray via is divided into two regions: a Bragg reflection region and a tapered transformation region. The tapered transformation region can be a waveguide-gradient tapered structure.

[0017] Furthermore, the insulating dielectric material can be silicon dioxide (SiO2), aluminum oxide (Al2O3), aluminum nitride (AlN), or scandium-doped aluminum nitride (Al2O3). 1-x Sc x N,x<0.4), hafnium zirconium oxide (Hf 0.5 Zr 0.5 O2).

[0018] Furthermore, the waveguide comprises two components, an upper and an lower one. The lower waveguide is located on the upper part of the silicon substrate and is wrapped by the lower cladding layer. The upper waveguide is located on the upper part of the lower cladding layer, closely attached to the lower cladding layer, and is wrapped by the upper cladding layer.

[0019] Furthermore, the three-layer structure of the first nanobeam cavity, the second nanobeam cavity, and the third nanobeam cavity, as well as the upper surface of the third nanobeam cavity, is wrapped by an upper cladding layer, and the first nanobeam cavity is in close contact with the lower cladding layer.

[0020] Furthermore, the structure of the bottom electrode varies depending on the material of the upper cladding layer;

[0021] When the cladding material is silicon dioxide, the bottom electrode includes a bottom electrode conductive channel and a bottom electrode metal plating layer. The bottom electrode conductive channel is embedded in the cladding layer at both ends of the second and third nanobeam cavities and is in electrical contact with the first nanobeam cavity. The bottom electrode metal plating layer covers the upper part of the bottom electrode conductive channel.

[0022] When the cladding material is air, the bottom electrode consists only of a bottom electrode metal plating layer and is in electrical contact with the first layer of nanobeam cavity.

[0023] Furthermore, the structure of the top electrode varies depending on the material of the upper cladding layer;

[0024] When the cladding material is silicon dioxide, the top electrode includes a top electrode conductive channel and a top electrode metal plating layer. The top electrode conductive channel is embedded in the cladding layer at both ends of the upper surface of the third nanobeam cavity and is in electrical contact with the third nanobeam cavity. The top electrode metal plating layer covers the upper part of the top electrode conductive channel.

[0025] When the cladding material is air, the top electrode consists only of a top electrode metal plating and is in electrical contact with the third nanobeam cavity.

[0026] Furthermore, both the upper and lower waveguides are made of Si or SiN, with the width W1 ranging from 300nm to 2000nm and the height h ranging from 200nm to 1000nm.

[0027] Furthermore, the parameters of the first layer nanobeam cavity structure, the second layer nanobeam cavity structure, and the third layer nanobeam cavity structure are as follows:

[0028] The width W2 of all three is the same, and its value range is: 300nm≤W2≤2000nm;

[0029] The three materials have different thicknesses, and the total thickness t ranges from 200nm to 500nm.

[0030] The length of the second nanobeam cavity is L, the length of the first nanobeam cavity is 6 / 5L, and the length of the third nanobeam cavity is the same as that of the second nanobeam cavity, 10um≤L≤50um.

[0031] Furthermore, both the first and third nanobeam cavities are made of doped polycrystalline silicon, with the doping concentration N ranging from 10 to 10⁻⁶. 12 cm -3 ≤N≤10 20 cm -3 The doping type is p-type or n-type doping.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] First, because the present invention uses a three-layer nanobeam cavity as a resonant cavity, the device has the characteristics of high quality factor and small mode volume. Compared with the prior art, the device has a small footprint and high sensitivity.

[0034] Secondly, the second-layer nanobeam cavity of the present invention uses ferroelectric materials, which makes the device non-volatile, resulting in lower power consumption and faster modulation speed compared to existing devices.

[0035] Third, because the present invention adopts a vertical structure of waveguide and resonator, it saves more floor space than the existing planar structure, and the manufacturing process is compatible with CMOS process, which facilitates integration and commercialization. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the front view structure of the first embodiment of the nanobeam cavity filter of the present invention;

[0037] Figure 2 This is a side view of the first embodiment of the nanobeam cavity filter of the present invention;

[0038] Figure 3 This is a schematic diagram of the main structure of the second embodiment of the nanobeam cavity filter of the present invention;

[0039] Figure 4 This is a side view of the second embodiment of the nanobeam cavity filter of the present invention;

[0040] Figure 5 This is a side view of the third embodiment of the nanobeam cavity filter of the present invention;

[0041] Figure 6 These are schematic diagrams of the electrical modulation coupling region structures in the first and third embodiments of the present invention;

[0042] Figure 7 These are schematic diagrams of the bottom electrode structure of the first and third embodiments of the present invention;

[0043] Figure 8 These are schematic diagrams of the top electrode structure in the first and third embodiments of the present invention;

[0044] Figure 9 These are schematic diagrams of the resonant cavity structures of all embodiments of the present invention;

[0045] Figure 10 These are schematic diagrams of the nanobeam cavity structure in all embodiments of the present invention. Detailed Implementation

[0046] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] Example 1: An electrically tunable nanobeam cavity filter with a silicon dioxide cladding, a hafnium zirconium oxide ferroelectric material, and a single waveguide.

[0048] Reference Figure 1 and Figure 2The vertical structure used in this example includes a substrate 1, a waveguide 3, a cladding 2, a resonant cavity 41, a bottom electrode 43, and a top electrode 42. The resonant cavity comprises a three-layer structure from bottom to top: a first nanobeam cavity 411, a second nanobeam cavity 412, and a third nanobeam cavity 413.

[0049] Reference Figure 10 The three-layer nanobeam cavity 411, 412, 413 is provided with nano-array through holes 414 of different sizes, which are divided into two regions: Bragg reflection region and tapered transformation region. The tapered transformation region can be a tapered structure with waveguide gradient.

[0050] Cladding 2 includes an upper cladding 22 and a lower cladding 21, both made of silicon dioxide. The upper cladding 22 serves to confine the light within the waveguide, while the lower cladding serves to support and confine the light within the waveguide 2.

[0051] The lower cladding layer 21 is located on the upper part of the substrate 1, and the waveguide 3 is wrapped by the lower cladding layer 21. The first nano-beam cavity 411 is located on the upper part of the lower cladding layer, and its lower surface is in close contact with the lower cladding layer 21. The second nano-beam cavity 412 is located on the upper part of the first nano-beam cavity 411, and the third nano-beam cavity 413 is located on the upper part of the second nano-beam cavity 412. The three-layer structure of the first nano-beam cavity 411, the second nano-beam cavity 412, and the third nano-beam cavity 413, as well as the upper surface of the third nano-beam cavity 413, are all wrapped by the upper cladding layer 22. The bottom electrode 43 is located at both ends above the first nano-beam cavity 411, and the top electrode 42 is located at both ends above the third nano-beam cavity 413.

[0052] Reference Figure 6 The three nanobeam cavities have the same width W. The first nanobeam cavity 411 is longer than the second nanobeam cavity 412 and the third nanobeam cavity 413. The second nanobeam cavity 412 and the third nanobeam cavity 413 have the same length. The width W2 ranges from 300nm to 2000nm. The three cavities have different thicknesses, and the total thickness t ranges from 200nm to 500nm. The length of the second nanobeam cavity 412 is L, the length of the first nanobeam cavity 411 is 6 / 5L, and the length of the third nanobeam cavity 413 is the same as that of the second nanobeam cavity 412. The length of the first nanobeam cavity 411 and the third nanobeam cavity 413 is 10µm to 50µm. The material of the first nanobeam cavity 411 and the third nanobeam cavity 413 is doped polycrystalline silicon, and the doping concentration N ranges from 10 to 100µm. 12 cm -3 ≤N≤10 20 cm -3 The first nano-beam cavity 411 is p-type doped, and the third nano-beam cavity 413 is n-type doped. The second nano-beam cavity 412 uses hafnium zirconium oxide as the ferroelectric material.

[0053] Reference Figure 7The bottom electrode 43 includes a bottom electrode conductive channel 431 and a bottom electrode metal plating layer 432. The bottom electrode conductive channel 431 is embedded in the cladding at both ends of the second layer nanobeam cavity 412 and the third layer nanobeam cavity 413 and is in electrical contact with the first layer nanobeam cavity 411. The bottom electrode metal plating layer 432 covers the upper part of the bottom electrode conductive channel 431.

[0054] Reference Figure 8 The top electrode 42 includes a top electrode conductive channel 421 and a top electrode metal plating layer 422. The top electrode conductive channel 421 is embedded in the cladding at both ends of the upper surface of the third nanobeam cavity 413 and is in electrical contact with the third nanobeam cavity 413. The top electrode metal plating layer 422 covers the upper part of the top electrode conductive channel 421.

[0055] The waveguide 3 is made of silicon material, which satisfies the requirement that the refractive index of the waveguide is greater than that of silicon dioxide, so as to confine the light within the waveguide 3. The width W1 of the waveguide 3 is in the range of 300nm≤W1≤2000nm, and the height h is in the range of 200nm≤h≤1000nm.

[0056] The working principle of this filter example is as follows:

[0057] When light enters from one side of the waveguide 3 port, it is confined within the waveguide due to the lower refractive index of the cladding compared to the waveguide itself. Consequently, during propagation within waveguide 3, the resonant cavity 41 directly above waveguide 3 will have a fixed resonant wavelength without an applied voltage. When this resonant wavelength matches the wavelength of the light propagating in waveguide 3, the light in waveguide 3 will transiently couple into the resonant cavity 41 above waveguide 3 and remain there, causing a decrease in the waveguide's output spectrum at the resonant wavelength. Electrical tuning is then achieved by adjusting the voltage. A voltage is applied to the bottom electrode 43 and the top electrode 42 to generate an electric field inside the second nanobeam cavity 412. When the electric field strength exceeds the coercive field, polarization charges are generated on the surface of the second nanobeam cavity 412, which changes the carrier distribution on the surface of the first nanobeam cavity 411 and the second nanobeam cavity 412. This changes the refractive index at the interface between the second nanobeam cavity 412 and the first nanobeam cavity 411 and the third nanobeam cavity 413, causing a change in the resonant wavelength of the resonant cavity 41, thereby achieving electric tuning.

[0058] Example 2: An electrically tunable nanobeam cavity filter with an air cladding, aluminum scandium nitrogen ferroelectric material, and a single waveguide.

[0059] Reference Figure 3 and Figure 4 The vertical structure used in this example includes a substrate 1, a waveguide 3, a cladding 2, a resonant cavity 41, a bottom electrode 43, and a top electrode 42. The resonant cavity comprises a three-layer structure from bottom to top: a first nanobeam cavity 411, a second nanobeam cavity 412, and a third nanobeam cavity 413.

[0060] Reference Figure 10 The three-layer nanobeam cavity 411, 412, 413 is provided with nano-array through holes 414 of different sizes, which are divided into two regions: Bragg reflection region and tapered transformation region. The tapered transformation region can be a tapered structure with waveguide gradient.

[0061] The cladding includes an upper cladding 22 and a lower cladding 21. The upper cladding 22 is made of air and serves to confine the light within the waveguide. The lower cladding 21 is made of silicon dioxide and serves to support and confine the light within the waveguide 3.

[0062] The lower cladding layer 21 is located on the upper part of the substrate 1, and the waveguide 3 is wrapped by the lower cladding layer 21. The first nano-beam cavity 411 is located on the upper part of the lower cladding layer, and its lower surface is in close contact with the lower cladding layer 21. The second nano-beam cavity 412 is located on the upper part of the first nano-beam cavity 411, and the third nano-beam cavity 413 is located on the upper part of the second nano-beam cavity 412. The three-layer structure of the first nano-beam cavity 411, the second nano-beam cavity 412, and the third nano-beam cavity 413, as well as the upper surface of the third nano-beam cavity 413, are all wrapped by the upper cladding layer 22. The bottom electrode 43 is located at both ends above the first nano-beam cavity 411, and the top electrode 42 is located at both ends above the third nano-beam cavity 413.

[0063] The material parameters of the first layer nanobeam cavity 411 and the third layer nanobeam cavity 413 are the same as those in Example 1. The material of the second layer nanobeam cavity 412 is ferroelectric material aluminum scandium nitrogen, and its parameters are the same as those in Example 1.

[0064] Reference Figure 9 The bottom electrode 43 has only one layer and is in electrical contact with the first nanobeam cavity 411. The top electrode 42 also has only one layer and is in electrical contact with the third nanobeam cavity 413.

[0065] The material parameters of waveguide 3 are the same as those in Example 1.

[0066] The working principle of this second embodiment is the same as that of the first embodiment.

[0067] Example 3: An electrically tunable nanobeam cavity filter with a silicon dioxide cladding, hafnium zirconium oxide as the ferroelectric material, and two waveguides.

[0068] Reference Figure 5 This example uses a vertical structure, which includes a substrate 1, a cladding 2, a waveguide 3, and a modulation coupling region 4. Wherein:

[0069] The cladding 2 includes an upper cladding 22 and a lower cladding 21, both made of silicon dioxide. The upper cladding 22 serves to confine the light within the waveguide, while the lower cladding 21 serves to support and confine the light within the waveguide.

[0070] The waveguide 3 includes a lower waveguide 31 and an upper waveguide 32.

[0071] The modulation coupling region 4 includes a resonant cavity 41, a top electrode 42, and a bottom electrode 43. The resonant cavity includes a three-layer structure from bottom to top: a first nanobeam cavity 411, a second nanobeam cavity 412, and a third nanobeam cavity 413. The top electrode 42 includes a top electrode conductive channel 421 and a top electrode metal plating layer 422. The bottom electrode 43 includes a bottom electrode conductive channel 431 and a bottom electrode metal plating layer 432.

[0072] Reference Figure 10 The three-layer nanobeam cavity 411, 412, 413 is provided with nano-array through holes 414 of different sizes, which are divided into two regions: Bragg reflection region and tapered transformation region. The tapered transformation region can be a tapered structure with waveguide gradient.

[0073] The lower cladding layer 21 is located on the upper part of the substrate 1. The lower waveguide 31 is wrapped by the lower cladding layer 21. The upper waveguide 32 is located on the upper part of the lower cladding layer 21. The lower surface of the upper waveguide 32 is in close contact with the lower cladding layer 21, and its periphery and upper surface are wrapped by the upper cladding layer 22. The first nano-beam cavity 411 is located on the upper part of the lower cladding layer 21, and its lower surface is in close contact with the lower cladding layer 21. The second nano-beam cavity 412 is located on the upper part of the first nano-beam cavity 411, and the third nano-beam cavity 413 is located on the upper part of the second nano-beam cavity 412. The periphery of the three-layer structure of the first nano-beam cavity 411, the second nano-beam cavity 412, and the third nano-beam cavity 413, as well as the upper surface of the third nano-beam cavity 413, are all wrapped by the upper cladding layer 22. The bottom electrode 43 is located at both ends of the first nanobeam cavity 411. The bottom electrode conductive channel 431 is embedded in the cladding at both ends of the second nanobeam cavity 412 and the third nanobeam cavity 413, and is in electrical contact with the first nanobeam cavity 411. The bottom electrode metal plating layer 432 covers the upper part of the bottom electrode conductive channel 431. The top electrode 42 is located at both ends of the third nanobeam cavity 413. The top electrode conductive channel 421 is embedded in the cladding at both ends of the upper surface of the third nanobeam cavity 413, and is in electrical contact with the third nanobeam cavity 413. The top electrode metal plating layer 422 covers the upper part of the top electrode conductive channel 421.

[0074] The upper waveguide 32 is located on the upper part of the lower cladding 21 and is in close contact with the lower cladding 21, and is wrapped by the upper cladding 22.

[0075] The material parameters of the three-layer nanobeam cavities 411, 412, and 413 are the same as those in Example 1.

[0076] Both the lower waveguide 31 and the upper waveguide 32 are made of silicon material, and their refractive index is greater than that of silicon dioxide, so as to confine the light within the lower waveguide 31 and the upper waveguide 32. The width W1 of the lower waveguide 31 and the upper waveguide 32 is in the range of 300nm≤W1≤2000nm, and the height h is in the range of 200nm≤h≤1000nm.

[0077] In this embodiment, the principle of resonant tunneling is used for filtering. Light is incident from one side of the lower waveguide 31 port. Because the refractive index of the lower cladding 21 is less than that of the lower waveguide 31, the light is confined in the lower waveguide 31. Therefore, during the transmission of light in the waveguide 31, the resonant cavity 41 directly above the waveguide 31 will have a fixed resonant wavelength when no voltage is applied. When it is the same as the wavelength of the light transmitted in the lower waveguide 31, the light in the lower waveguide 31 will be transiently coupled to the resonant cavity 41 above the lower waveguide 31. The light coupled into the resonant cavity 41 is transmitted into the lower waveguide 31 and the upper waveguide 32 in a gradually attenuated state. The light is transmitted along the two port directions of the waveguide. Since the resonant cavity 41 has two resonant states, it can cancel the light intensity at the input port of the lower waveguide 31. A certain wavelength of light is selected to enter the upper waveguide 32, thereby achieving the filtering effect. At this point, electrical tuning is achieved by adjusting the voltage, that is, applying voltage to the bottom electrode 43 and the top electrode 42 to generate an electric field inside the second layer nanobeam cavity 412. When the electric field strength exceeds the coercive field, polarization charge is generated on the surface of the second layer nanobeam cavity 412, which changes the carrier distribution on the surface of the first nanobeam cavity 411 and the second nanobeam cavity 412, thereby changing the refractive index at the interface between the second layer nanobeam cavity 412 and the first layer nanobeam cavity 411 and the third layer nanobeam cavity 413, causing the resonant wavelength of the resonant cavity 41 to change, thus achieving electrical tuning.

[0078] The above descriptions are merely three specific examples of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. An electrically tunable nanobeam cavity optical filter, comprising: A silicon substrate (1), a cladding layer (2), a waveguide (3), and an electrically modulated coupling region (4) are characterized by: The cladding is configured as two layers, namely a lower cladding (21) and an upper cladding (22), and the material of the upper cladding (22) is silicon dioxide or air; The electrical modulation coupling region (4) is located on the upper part of the lower cladding (21) and includes a resonant cavity (41), a bottom electrode (43) and a top electrode (42). The resonant cavity (41) comprises a three-layer structure from bottom to top: a first nanobeam cavity (411), a second nanobeam cavity (412), and a third nanobeam cavity (413). These three nanobeam cavities are provided with nano-array through holes (414) of different sizes, and the second nanobeam cavity (412) is made of ferroelectric material. The bottom electrode (43) is located at both ends above the first layer of nanobeam cavity (411); The top electrode (42) is located at both ends above the third layer of nanobeam cavity (413).

2. The filter according to claim 1, characterized in that: The nanoarray via (414) is divided into two regions: the Bragg reflection region and the tapered transformation region. The tapered transformation region can be a tapered structure with waveguide gradient.

3. The filter according to claim 1, characterized in that: The ferroelectric material includes scandium-doped aluminum nitride, Al 1- x Sc x N, x < 0.4, hafnium zirconium oxide, Hf 0.5 Zr 0.5 O2.

4. The filter according to claim 1, characterized in that: The waveguides are two in number, with the lower waveguide (31) located on the upper part of the silicon substrate (1) and wrapped by the lower cladding layer (21); the upper waveguide (32) is located on the upper part of the lower cladding layer (21) and is in close contact with the lower cladding layer (21) and wrapped by the upper cladding layer (22).

5. The filter according to claim 1, characterized in that: The three-layer structure of the first nanobeam cavity (411), the second nanobeam cavity (412), and the third nanobeam cavity (413) and the upper surface of the third nanobeam cavity (413) are wrapped by the upper cladding (22), and the lower surface of the first nanobeam cavity (411) is in close contact with the lower cladding (21).

6. The filter according to claim 1, characterized in that: The structure of the bottom electrode (43) varies depending on the material of the upper cladding (22); When the cladding (22) material is silicon dioxide, the bottom electrode (43) includes a bottom electrode conductive channel (431) and a bottom electrode metal plating layer (432). The bottom electrode conductive channel (431) is embedded in the cladding (22) at both ends of the second layer nanobeam cavity (412) and the third layer nanobeam cavity (413), and is in electrical contact with the first layer nanobeam cavity (411). The bottom electrode metal plating layer (432) covers the upper part of the bottom electrode conductive channel (431). When the cladding material is air, the bottom electrode (43) consists only of a bottom electrode metal plating layer and is in electrical contact with the first layer of nanobeam cavity (411).

7. The filter according to claim 1, characterized in that: The structure of the top electrode (42) varies depending on the material of the upper cladding (22); When the cladding material is silicon dioxide, the top electrode (42) includes a top electrode conductive channel (421) and a top electrode metal plating layer (422). The top electrode conductive channel (421) is embedded in the cladding layer (22) at both ends of the upper surface of the third nanobeam cavity (413) and is in electrical contact with the third nanobeam cavity (413). The top electrode metal plating layer (422) covers the upper part of the top electrode conductive channel (421). When the cladding material is air, the top electrode (42) consists only of the top electrode metal plating and is in electrical contact with the third nanobeam cavity (413).

8. The filter according to claim 1, characterized in that: The materials of the lower waveguide (31) and the upper waveguide (32) are both Si or SiN. The width W1 ranges from 300 nm to 2000 nm, and the height h ranges from 200 nm to 1000 nm.

9. The filter according to claim 1, characterized in that: The parameters of the first nanobeam cavity structure (411), the second nanobeam cavity structure (412), and the third nanobeam cavity structure (413) are as follows: The width W2 of all three is the same, and its value range is: 300 nm ≤ W2 ≤ 2000 nm; The three materials have different thicknesses, and the total thickness t ranges from 200 nm to 500 nm. The length of the second nanobeam cavity is L, the length of the first nanobeam cavity is 6 / 5L, and the length of the third nanobeam cavity is the same as that of the second nanobeam cavity, 10 μm≤L≤50 μm.

10. The filter according to claim 1, characterized in that: The material used in the first layer nanobeam cavity (411) and the third layer nanobeam cavity (413) is doped polysilicon, and the doping concentration N is in the range of 10 12 cm -3 ≤N≤10 20 cm -3 , and the doping type is p-type or n-type doping.

Images