Dual-channel optical filter based on three-rectangular-cavity edge coupling waveguide

Abstract

The utility model relates to a dual-channel optical filter based on a three-rectangular cavity edge coupling waveguide. The dual-channel optical filter comprises a silicon substrate, a sapphire layer, a graphene nano-strip waveguide, a first graphene rectangular resonant cavity, a second graphene rectangular resonant cavity and a third graphene rectangular resonant cavity, the sapphire layer is arranged above the silicon substrate; a graphene nano-strip waveguide, a first graphene rectangular resonant cavity, a second graphene rectangular resonant cavity and a third graphene rectangular resonant cavity are arranged on the upper surface of the sapphire layer; the first graphene rectangular resonant cavity and the third graphene rectangular resonant cavity are connected in series and arranged on one side of the graphene nano-strip waveguide, and the second graphene rectangular resonant cavity is arranged on the other side of the graphene nano-strip waveguide. According to the utility model, the problems of narrow bandwidth and poor filtering effect of an optical filter with a graphene structure are solved; the dual-channel optical filter which is small in size, wide in bandwidth, excellent in filtering effect, dynamically tunable and easy to integrate is realized in an infrared band.

Description

Technical Field

[0001] This utility model relates to the field of optical communication technology, and more specifically to a dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide. Background Technology

[0002] Optical filters enable wavelength division multiplexing, bandpass, or bandstop wavelength selection, making them crucial components in optical communication technology. With the development of large-scale integrated all-optical devices, the demand for small-size, dynamically tunable multi-channel optical filters in the infrared band is becoming increasingly apparent. Therefore, realizing dynamically tunable multi-channel optical filters with a new operating mechanism that is dynamically tunable, small-size, and easy to integrate is of paramount importance.

[0003] Surface plasmon polaritons (SPPs) are evanescent electromagnetic waves that propagate along the metal-dielectric interface and decay exponentially in the direction perpendicular to the metal surface. SPPs possess the ability to overcome the traditional optical diffraction limit and exhibit strong localized optical field enhancement characteristics, thus enabling the guidance and manipulation of light at the subwavelength level. SPP waves can serve as carriers of energy and information, and they hold significant application value in high-density integrated photonic circuits.

[0004] Currently, many SPP-based photonic devices have emerged, such as bandpass filters, bandstop filters, multiplexers (demultiplexers), Mach-Zehnder interferometers (MZI), optical switches, sensors, and logic gates. Due to the low loss and good out-of-band suppression characteristics of SPP bandpass or bandstop filters, and because SPP-based optical filters are crucial components in high-density integrated photonic circuits, many SPP optical filters with optical resonant cavity side-coupled waveguide structures have been developed. Therefore, realizing SPP optical filters with compact device size, multiple channels, wide bandwidth, dynamic tunability, and ease of integration is the future development trend.

[0005] Currently, SPP optical filters based on the plasmon-induced transparency (PIT) effect are attracting increasing attention. The PIT phenomenon is similar to the electromagnetically induced transparency (EIT) effect in atomic gases. However, compared to the EIT phenomenon in atomic gases, which is determined by the absorption characteristics of the material, the EIT-like phenomenon generated by the geometry of a resonant cavity coupled with a plasma waveguide system has greater application prospects due to its advantages such as room temperature operation, compatibility with chip integration, tunability of the transmission band, and controllable bandwidth. Because the PIT effect produces a transparency peak in the transmission spectrum, it is suitable for application in optical filters.

[0006] In recent years, graphene, a two-dimensional material consisting of a single carbon atom layer, has provided a novel and low-loss method for confining and controlling surface-mount filters (SPPs), and is therefore widely used in the design of SPP devices. Considering the unique properties of graphene, graphene-based micro- and nanostructures can generate very strong localized SPPs from the near-infrared region to the terahertz band. The PIT effect is generated in the graphene structure, and by changing the Fermi level of graphene, PIT effect optical filters can be dynamically tuned.

[0007] The shortcomings of existing technology are:

[0008] 1. Because traditional SPP waveguide systems produce a single PIT effect, they can only realize a single-channel optical filter, resulting in a single filtering channel.

[0009] 2. Traditional SPP optical filters are typically static and non-tunable, resulting in insufficient flexibility and difficulty in adapting to dynamic scenarios.

[0010] 3. Traditional MZI-based and fiber Bragg grating-based filters are large in size, which is not conducive to large-scale device integration. Furthermore, these filters have disadvantages such as narrow bandwidth and poor out-of-band suppression, which are not conducive to the application and development of optical filters in broadband high-speed optical communication networks. Utility Model Content

[0011] This invention addresses the aforementioned problems by providing a dual-channel optical filter based on a three-rectangular cavity-side coupled waveguide. Its purpose is to achieve excellent filtering performance; solve the problems of narrow bandwidth and poor filtering effect in graphene-structured optical filters; realize a small-size, wide-bandwidth, high-performance, dynamically tunable, and easily integrated dual-channel optical filter in the infrared band; and achieve an ultra-compact graphene optical filter, significantly reducing its size and solving the problem of difficulty in integrating graphene optical filters in on-chip plasmon optical paths.

[0012] To solve the above problems, the technical solution provided by this utility model is as follows:

[0013] A dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide comprises a silicon substrate, a sapphire layer, a graphene nanostrip waveguide, a first graphene rectangular resonant cavity, a second graphene rectangular resonant cavity, and a third graphene rectangular resonant cavity, wherein:

[0014] The sapphire layer is disposed above the silicon substrate; the upper surface of the sapphire layer is provided with the graphene nanostrip waveguide, the first graphene rectangular resonant cavity, the second graphene rectangular resonant cavity, and the third graphene rectangular resonant cavity; the first and third graphene rectangular resonant cavities are connected in series on one side of the graphene nanostrip waveguide, and the second graphene rectangular resonant cavity is disposed on the other side of the graphene nanostrip waveguide; the first and second graphene rectangular resonant cavities undergo destructive coupling and produce a single PIT effect; the second and third graphene rectangular resonant cavities undergo destructive coupling and produce a single PIT effect.

[0015] Preferably, the thickness of the silicon substrate is 300 nm; the thickness of the sapphire layer is 200 nm.

[0016] Preferably, the width of the graphene nanostrip waveguide is 10 nm.

[0017] Preferably, the length of the first graphene rectangular resonant cavity, the second graphene rectangular resonant cavity, and the third graphene rectangular resonant cavity is 140 nm, and the width is 20 nm.

[0018] Preferably, the coupling spacing between the first graphene rectangular resonant cavity, the second graphene rectangular resonant cavity, the third graphene rectangular resonant cavity and the graphene nanostrip waveguide is 15 nm.

[0019] Preferably, the distance between the center of the first graphene rectangular resonant cavity and the center of the third graphene rectangular resonant cavity along the front-back direction is 50 nm; the distance between the centers of the two second graphene rectangular resonant cavities along the front-back direction is 50 nm.

[0020] Preferably, the thickness of the single-layer graphene used in the optical filter is 0.2 nm; the distance between the dipole of the slow-light device exciting the SPPs and the center of the first graphene rectangular resonant cavity, the second graphene rectangular resonant cavity, and the third graphene rectangular resonant cavity is fixed at 150 nm; the spacing between the center of the first graphene rectangular resonant cavity, the second graphene rectangular resonant cavity, and the third graphene rectangular resonant cavity and the detector is 150 nm.

[0021] Preferably, the Fermi level of the graphene nanostrip waveguide is 0.40 eV; the Fermi level of the first graphene rectangular resonant cavity is 0.42 eV; the Fermi level of the second graphene rectangular resonant cavity is 0.43 eV; and the Fermi level of the third graphene rectangular resonant cavity is 0.44 eV.

[0022] Preferably, the size of the optical filter is less than 0.05. μ m 2 .

[0023] Compared with the prior art, this utility model has the following advantages:

[0024] Because this invention applies the double PIT effect generated by the three-graphene rectangular resonant cavity side-coupled nanostrip waveguide structure to an integrated dual-channel optical filter; the spectral bandwidths of the two transmission windows are 262 nm and 263 nm, respectively, and the maximum spectral bandwidth of the filter can reach 263 nm; the peak value of the transparent peak and the transmittance of the transmission depression have a very large contrast, thus achieving excellent filtering effect.

[0025] This invention solves the problems of narrow bandwidth and poor filtering effect of graphene structure optical filters; it realizes a small-size, wide-bandwidth, high-performance, dynamically tunable, and easy-to-integrate dual-channel optical filter in the infrared band.

[0026] The dual-channel optical filter based on a three-graphene rectangular resonant cavity side-coupled nanostrip waveguide of this invention has a size of less than 0.05 μm2, thereby realizing an ultra-compact graphene optical filter, greatly reducing the size of the graphene optical filter, and solving the problem of the difficulty in integrating graphene optical filters in on-chip plasmon optical paths. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the structure of a dual-channel optical filter based on a three-graphene rectangular resonant cavity side-coupled nanostrip waveguide, which is a specific embodiment of this utility model.

[0028] Figure 2 A schematic diagram of the system transmission spectrum of a dual-channel optical filter based on a three-graphene rectangular resonant cavity side-coupled nanostrip waveguide, which is a specific embodiment of this utility model;

[0029] Among them: 1. silicon substrate, 2. sapphire layer, 3. graphene nanostrip waveguide, 4. first graphene rectangular resonant cavity, 5. second graphene rectangular resonant cavity, 6. third graphene rectangular resonant cavity. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0031] This utility model application claims protection for a dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide, such as... Figure 1 As shown, it includes a silicon substrate 1, a sapphire layer 2, a graphene nanostrip waveguide 3, a first graphene rectangular resonant cavity 4, a second graphene rectangular resonant cavity 5, and a third graphene rectangular resonant cavity 6, wherein:

[0032] A sapphire layer 2 is disposed above a silicon substrate 1. A graphene nanostrip waveguide 3, a first graphene rectangular resonant cavity 4, a second graphene rectangular resonant cavity 5, and a third graphene rectangular resonant cavity 6 are disposed on the upper surface of the sapphire layer 2. The first graphene rectangular resonant cavity 4 and the third graphene rectangular resonant cavity 6 are connected in series on one side of the graphene nanostrip waveguide 3, and the second graphene rectangular resonant cavity 5 is disposed on the other side of the graphene nanostrip waveguide 3. The first graphene rectangular resonant cavity 4 and the second graphene rectangular resonant cavity 5 undergo destructive coupling interference, producing a single PIT effect. The second graphene rectangular resonant cavity 5 and the third graphene rectangular resonant cavity 6 also undergo destructive coupling interference, producing a single PIT effect.

[0033] It should be noted that in practical applications, SPPs on the graphene nanostrip waveguide 3 can be excited using gratings or prisms. This invention uses a dipole to excite surface plasmons of boundary mode at the front end of the graphene nanostrip waveguide 3 and sets a detector at the rear end of the graphene nanostrip waveguide 3.

[0034] It should be noted that the purpose of this invention is to realize a small-sized, multi-channel, wide-bandwidth, dynamically tunable, and easily integrated graphene-structured SPPs optical filter. This invention uses FDTD-solution software simulation to determine the structural parameters of a dual-channel optical filter based on a three-graphene rectangular resonant cavity side-coupled nanostrip waveguide.

[0035] In this specific embodiment, the thickness of the silicon substrate 1 is 300 nm; the thickness of the sapphire layer 2 is 200 nm. In the silicon-sapphire waveguide, light only causes a propagation loss as low as 1.9 dB / cm at a distance of 5.18 μm.

[0036] In this specific embodiment, the width of the graphene nanostrip waveguide 3 is 10 nm.

[0037] In this specific embodiment, the length of the first graphene rectangular resonant cavity 4, the second graphene rectangular resonant cavity 5, and the third graphene rectangular resonant cavity 6 are all 140 nm, and the width of each is 20 nm.

[0038] In this specific embodiment, the coupling distance between the first graphene rectangular resonant cavity 4, the second graphene rectangular resonant cavity 5, the third graphene rectangular resonant cavity 6 and the graphene nanostrip waveguide 3 is 15 nm.

[0039] In this specific embodiment, the distance between the center of the first graphene rectangular resonant cavity 4 and the center of the third graphene rectangular resonant cavity 6 along the front-back direction is 50 nm; the distance between the centers of the two second graphene rectangular resonant cavities 5 along the front-back direction is 50 nm.

[0040] In this specific embodiment, the thickness of the single-layer graphene used in the optical filter is 0.2 nm; the distance between the dipole of the slow-light device exciting the SPPs and the center of the first graphene rectangular resonant cavity 4, the second graphene rectangular resonant cavity 5, and the third graphene rectangular resonant cavity 6 is fixed at 150 nm; the spacing between the center of the first graphene rectangular resonant cavity 4, the second graphene rectangular resonant cavity 5, and the third graphene rectangular resonant cavity 6 and the detector is 150 nm. To avoid substrate loss in the mid-infrared band, the substrate material used in the structure is sapphire Al2O3, whose refractive index and loss factor k are approximately 1.60 and 0.0004, respectively, at a wavelength of 5.37 μm.

[0041] In this specific embodiment, the Fermi level of the graphene nanostrip waveguide 3 is 0.40 eV; the Fermi level of the first graphene rectangular resonant cavity 4 is 0.42 eV; the Fermi level of the second graphene rectangular resonant cavity 5 is 0.43 eV; and the Fermi level of the third graphene rectangular resonant cavity is 0.44 eV.

[0042] In this specific embodiment, the size of the optical filter is less than 0.05. μ m 2 It can realize ultra-compact graphene optical filters.

[0043] It should be noted that the first graphene rectangular resonant cavity 4, the second graphene rectangular resonant cavity 5, and the third graphene rectangular resonant cavity 6 are coupled with a nanostrip waveguide system to generate a double PIT effect.

[0044] In this specific embodiment, such as Figure 2 As shown, two significant PIT effect transmission windows are generated in the transmission spectrum. The center wavelengths of the two transparent peaks are 6029 nm and 6232 nm, and the peak values ​​are 0.74 and 0.70, respectively. The wavelengths of the three transmission depressions are 5850 nm, 6112 nm, and 6375 nm, and the transmittances of the three transmission depressions are 0.10, 0.08, and 0.08, respectively. The spectral bandwidth of the first and second transmission depressions in the transmission spectrum is 262 nm, and the spectral bandwidth of the second and third transmission depressions is 263 nm, meaning the maximum spectral bandwidth of the filter can reach 263 nm. Furthermore, the contrast between the peak value of the transparent peak and the transmittance of the transmission depressions is very large, thus achieving excellent filtering performance.

[0045] It should be noted that, in the infrared band, this invention discloses a dual-channel optical filter based on a three-graphene rectangular resonant cavity side-coupled nanostrip waveguide; and in the infrared band, a dual-channel optical filter based on the double PIT effect is realized. By changing the Fermi level of graphene, the PIT effect transmission spectrum can be dynamically tuned, realizing an ultra-compact and dynamically tunable graphene-structured multi-channel optical filter with a device size of less than 0.05 μm². This novel graphene-structured multi-channel optical filter has significant scientific research value and potential for future application in the field of photonic device integration, and will play a supporting role in the development of future all-optical communication networks and all-optical signal processing technologies.

[0046] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the present invention is in a state with fewer features than all of the disclosed individual embodiments. Therefore, the appended claims are hereby clearly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the present invention.

[0047] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use this invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the widest scope of the principles and novel features disclosed in this application.

[0048] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0049] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide, characterized in that: It comprises a silicon substrate (1), a sapphire layer (2), a graphene nanostrip waveguide (3), a first graphene rectangular resonant cavity (4), a second graphene rectangular resonant cavity (5), and a third graphene rectangular resonant cavity (6), wherein: The sapphire layer (2) is disposed above the silicon substrate (1); the upper surface of the sapphire layer (2) is provided with the graphene nanostrip waveguide (3), the first graphene rectangular resonant cavity (4), the second graphene rectangular resonant cavity (5), and the third graphene rectangular resonant cavity (6); the first graphene rectangular resonant cavity (4) and the third graphene rectangular resonant cavity (6) are connected in series on one side of the graphene nanostrip waveguide (3), and the second graphene rectangular resonant cavity (5) is disposed on the other side of the graphene nanostrip waveguide (3); the first graphene rectangular resonant cavity (4) and the second graphene rectangular resonant cavity (5) undergo coupling destructive interference and generate a single PIT effect; the second graphene rectangular resonant cavity (5) and the third graphene rectangular resonant cavity (6) undergo coupling destructive interference and generate a single PIT effect.

2. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 1, characterized in that: The thickness of the silicon substrate (1) is 300 nm; the thickness of the sapphire layer (2) is 200 nm.

3. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 2, characterized in that: The width of the graphene nanostrip waveguide (3) is 10 nm.

4. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 3, characterized in that: The first graphene rectangular resonant cavity (4), the second graphene rectangular resonant cavity (5), and the third graphene rectangular resonant cavity (6) all have a length of 140 nm and a width of 20 nm.

5. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 4, characterized in that: The coupling distance between the first graphene rectangular resonant cavity (4), the second graphene rectangular resonant cavity (5), the third graphene rectangular resonant cavity (6) and the graphene nanostrip waveguide (3) is 15 nm.

6. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 5, characterized in that: The distance between the center of the first graphene rectangular resonant cavity (4) and the center of the third graphene rectangular resonant cavity (6) along the front-back direction is 50 nm; the distance between the centers of the two second graphene rectangular resonant cavities (5) along the front-back direction is 50 nm.

7. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 6, characterized in that: The optical filter uses a single layer of graphene with a thickness of 0.2 nm; the distance between the dipole of the slow-light device exciting the SPPs and the center of the first graphene rectangular resonant cavity (4), the second graphene rectangular resonant cavity (5), and the third graphene rectangular resonant cavity (6) is fixed at 150 nm; the spacing between the center of the first graphene rectangular resonant cavity (4), the second graphene rectangular resonant cavity (5), and the third graphene rectangular resonant cavity (6) and the detector is 150 nm.

8. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 7, characterized in that: The Fermi level of the graphene nanostrip waveguide (3) is 0.40 eV; the Fermi level of the first graphene rectangular resonant cavity (4) is 0.42 eV; the Fermi level of the second graphene rectangular resonant cavity (5) is 0.43 eV; and the Fermi level of the third graphene rectangular resonant cavity is 0.44 eV.

9. The dual-channel optical filter based on a three-rectangular cavity side-coupled waveguide according to claim 8, characterized in that: The size of the optical filter is less than 0.

05. μ m 2 .

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