阅读说明：本技术 基于同侧双微腔耦合结构的波导滤波器 (Waveguide filter based on same-side double-microcavity coupling structure ) 是由 牛军浩 王嘉洁 叶捷胜 骆薇羽 许川佩 朱爱军 于 2021-05-27 设计创作，主要内容包括：本发明涉及纳米光子学技术领域,具体公开了一种基于同侧双微腔耦合结构的波导滤波器,包括介质基底、金属薄膜、同心双半圆环波导谐振腔和直线波导腔,金属薄膜设置于介质基底的上端面,金属薄膜上设置有直线波导腔,以及位于直线波导腔上侧的同心双半圆环波导谐振腔。通过构造共心双半圆环结构,使输出波导同时受到两个波导谐振腔共振模式的影响。两个波导谐振腔腔之间由于反相振荡导致电磁波发生干涉相消而产生类电磁诱导透明现象实现双模式双通道带阻滤波功能,与圆环结构和相交圆环结构相比,其滤波性能有所提升,此结构在全光窄带带阻滤波器方面具有潜在的应用前景。(The invention relates to the technical field of nanophotonics, and particularly discloses a waveguide filter based on a homonymy double-microcavity coupling structure. By constructing a concentric double semicircular ring structure, the output waveguide is simultaneously influenced by the resonance modes of the two waveguide resonant cavities. The dual-mode dual-channel band-stop filtering function is realized by the electromagnetic wave interference cancellation generated by the opposite-phase oscillation between the two waveguide resonant cavities and the electromagnetic induction transparent phenomenon, compared with a circular ring structure and an intersected circular ring structure, the filtering performance of the dual-mode dual-channel band-stop filtering structure is improved, and the structure has potential application prospect in the aspect of an all-optical narrow-band-stop filter.)

1. A waveguide filter based on a same-side double-microcavity coupling structure is characterized in that,

the waveguide cavity comprises a medium substrate, a metal film, a concentric double-semicircular-ring waveguide resonant cavity and a linear waveguide cavity, wherein the metal film is arranged on the upper end surface of the medium substrate, the linear waveguide cavity and the concentric double-semicircular-ring waveguide resonant cavity are arranged on the upper side of the linear waveguide cavity and are arranged on the metal film.

2. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 1,

the medium substrate adopts SiO₂A substrate.

3. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 1,

the metal film is made of Ag.

4. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 1,

the concentric double semi-circular ring waveguide resonant cavities comprise a first semi-ring resonant cavity and a second semi-ring resonant cavity, and the first semi-ring resonant cavity and the second semi-ring resonant cavity are arranged up and down in a concentric mode.

5. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 1,

the width of the linear waveguide cavity is 50 nm.

6. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 5,

the length of the linear waveguide cavity is 1500 nm.

7. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 4,

the central radius of the first semi-ring resonant cavity is 120 nm.

8. The waveguide filter based on the ipsilateral double microcavity coupling structure of claim 4,

the central radius of the second half-ring resonant cavity is 245 nm.

Technical Field

The invention relates to the technical field of nanophotonics, in particular to a waveguide filter based on a same-side double-microcavity coupling structure.

Background

With the development of optical technology, future integrated optics put higher demands on integration density. Surface plasmons (SPPs) can control the propagation of optical signals on a nanometer scale due to a strong bonding effect with the interface of metal and medium, and show great application prospects in subwavelength optical devices and high-integration photonic circuits.

Today, there are many surface plasmon waveguide structures such as metal nanoparticle waveguide, metal thin film, metal-insulator-metal (MIM) plate, plasmon nanocluster, nanoslit, and hybrid bragg waveguide, but the above-listed surface plasmon waveguide structures have poor filtering performance.

Disclosure of Invention

The invention aims to provide a waveguide filter based on an ipsilateral double-microcavity coupling structure, and aims to improve the filtering performance.

In order to achieve the above object, the waveguide filter based on the homonymy double microcavity coupling structure adopted by the invention comprises a dielectric substrate, a metal film, a concentric double semicircular ring waveguide resonant cavity and a linear waveguide cavity, wherein the metal film is arranged on the upper end surface of the dielectric substrate, the linear waveguide cavity is arranged on the metal film, and the concentric double semicircular ring waveguide resonant cavity is positioned on the upper side of the linear waveguide cavity.

Wherein the medium substrate adopts SiO₂A substrate.

Wherein, the metal film is made of Ag.

The concentric double semi-circular ring waveguide resonant cavity comprises a first semi-circular resonant cavity and a second semi-circular resonant cavity, and the first semi-circular resonant cavity and the second semi-circular resonant cavity are arranged up and down in a concentric mode.

Wherein the width of the linear waveguide cavity is 50 nm.

Wherein the length of the linear waveguide cavity is 1500 nm.

Wherein, the central radius of the first semi-ring resonant cavity is 120 nm.

Wherein the central radius of the second half-ring resonant cavity is 245 nm.

The waveguide filter based on the homonymy double-microcavity coupling structure enables the output waveguide to be simultaneously influenced by the resonance modes of the two waveguide resonant cavities by constructing a concentric double-semicircular-ring structure. The dual-mode dual-channel band-stop filtering function is realized by the electromagnetic wave interference cancellation generated by the opposite-phase oscillation between the two waveguide resonant cavities and the electromagnetic induction transparent phenomenon, compared with a circular ring structure and an intersected circular ring structure, the filtering performance of the dual-mode dual-channel band-stop filtering structure is improved, and the structure has potential application prospect in the aspect of an all-optical narrow-band-stop filter.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a perspective view of a waveguide filter based on an ipsilateral double microcavity coupling structure according to the present invention.

Fig. 2 is a schematic structural diagram of a waveguide filter based on an ipsilateral double microcavity coupling structure according to the present invention.

FIG. 3 is a transmission line graph of a first half-ring resonator, a second half-ring resonator, and a concentric double half-ring waveguide resonator of the present invention.

Fig. 4 is a transmission line graph of four different coupling distances of the present invention.

Fig. 5 is a transmission spectrum diagram of the transmittance and the full width at half maximum of the modes 1 and 2 of the present invention with respect to the coupling distance g.

FIG. 6 is a graph of transmission spectra for values of increasing refractive index of the medium in steps of 0.02nm, with other parameter settings consistent with the present invention.

1-medium substrate, 2-metal film, 3-first semi-ring resonant cavity, 4-second semi-ring resonant cavity and 5-linear waveguide cavity.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

Referring to fig. 1 to 6, the present invention provides a waveguide filter based on a homonymy double microcavity coupling structure, including a dielectric substrate 1, a metal thin film 2, a concentric double semicircular waveguide resonant cavity and a linear waveguide cavity 5, where the metal thin film 2 is disposed on an upper end surface of the dielectric substrate 1, the metal thin film 2 is provided with the linear waveguide cavity 5, and the concentric double semicircular waveguide resonant cavity is located on an upper side of the linear waveguide cavity 5.

In this embodiment, the output waveguide is simultaneously affected by the two waveguide resonator resonance modes by constructing a concentric double semicircular ring structure. The dual-mode dual-channel band-stop filtering function is realized by the electromagnetic wave interference cancellation generated by the opposite-phase oscillation between the two waveguide resonant cavities and the electromagnetic induction transparent phenomenon, compared with a circular ring structure and an intersected circular ring structure, the filtering performance of the dual-mode dual-channel band-stop filtering structure is improved, and the structure has potential application prospect in the aspect of an all-optical narrow-band-stop filter.

Further, the dielectric substrate 1 adopts SiO₂A substrate.

The metal film 2 is made of Ag.

The concentric double semi-circular ring waveguide resonant cavity comprises a first semi-circular resonant cavity 3 and a second semi-circular resonant cavity 4, and the first semi-circular resonant cavity 3 and the second semi-circular resonant cavity 4 are arranged up and down in a concentric mode.

The width of the linear waveguide cavity 5 is 50 nm.

The length of the linear waveguide cavity 5 is 1500 nm.

The central radius of the first half-ring resonant cavity 3 is 120 nm.

The central radius of the second half-ring resonant cavity 4 is 245 nm.

And a boundary coupling mode is formed between the concentric double semicircular ring waveguide resonant cavity and the linear waveguide cavity 5.

The coupling distance between the concentric double semicircular ring waveguide resonant cavity and the linear waveguide cavity 5 is 20 nm.

The central radius of the first half-ring resonator 3 is equal to one half of the sum of the inner radius of the first half-ring resonator 3 and the outer radius of the first half-ring resonator 3.

The central radius of the second half-ring cavity 4 is equal to one half of the sum of the inner radius of the second half-ring cavity 4 and the outer radius of the second half-ring cavity 4.

In the present embodiment, the plasma concentric double semicircular ring waveguide filter based on the microcavity structure is provided on the dielectric substrate 1, and includes a metal thin film 2 and a concentric double semicircular ring waveguide resonator provided on the metal thin film 2.

When incident light enters the waveguide as TM wave, the SPPs are excited and then transmitted from left to right along the waveguide, and the dispersion relation when the SPPs are transmitted in the MIM waveguide structure is as follows:

in the formula, K_dAnd K_mCan be expressed as:

wherein k is₀2 pi λ is the wavevector of light in free space, and β represents the propagation constant of SPPs.

The dielectric constants of the dielectric material and the metal material filled in the structure are respectively represented by epsilon_dAnd ε_mAnd (4) showing.

ω represents the angular frequency of the incident light, so different propagation constants represent different mode distributions at different incident wavelengths.

The schematic structural diagram is shown in fig. 2, the first half-ring resonator 3 closer to the linear waveguide cavity 5 is represented by SR3, and the second half-ring resonator 4 located above SR3 is represented by SR 4. The white in the first half-ring resonant cavity 3 and the second half-ring resonant cavity 4 and the linear waveguide cavity 5 for transmitting SPPs represents the medium air, and the rest of the gray part represents the metal material silver. A boundary coupling mode is formed between the concentric double semicircular ring waveguide resonant cavity and the linear waveguide cavity 5. The initialization configuration parameters are set as follows: the width of the linear waveguide cavity 5 for transmitting SPPs is set as W1-50 nm, the length of the linear waveguide cavity 5 is set as D1500 nm, the inner radius of SR3 is R1, the outer radius is R2, and the central radius R1 is set as (R1+ R2)/2-120 nm; SR4 has an inner radius of R3, an outer radius of R4, and a center radius of R2 ═ R3+ R4)/2 ═ 245 nm. And the coupling distance g between the concentric double semicircular ring waveguide resonant cavity and the linear waveguide cavity 5 is 20 nm. The width and length of the linear waveguide cavity 5 for transmitting SPPs are consistent with the parameters of the previous section model. Incident light enters from the left side and is transmitted through the waveguide, the incident light and the semicircular ring are coupled, and if the electromagnetic wave does not meet the resonance condition, the electromagnetic wave is transmitted to the output port on the right side along the waveguide. The medium filled in the structure is still air, and the metal material is silver. In numerical simulation, the dielectric constant of metallic silver is still described by using Drude dispersion model. The dispersion relation for transmission of SPPs in a waveguide structure is described by equation (4-1). The wavelength scanning range is 800nm-1600 nm.

In fig. 3, the transmission line of SR3 is indicated by a first line, the transmission line of SR4 is indicated by a second line, and the transmission line of the overall structure is indicated by a third line. It can be observed that a narrow stop band appears in the transmission lines of both SR3 and SR 4. Therefore, the two resonant cavities have the function of coupling electromagnetic field energy to form standing waves, and further the function of stop band filtering in the waveguide structure is realized. For the transmission spectral lines of the double semi-rings of the whole structure, two narrow bands appear in the transmission spectral lines. The right transmission trough is represented by Mode 1(Mode1) and the left transmission trough is represented by Mode 2(Mode 2). Wherein the transmittance of mode1 is 0.13 and the full width at half maximum is 21 nm. The transmittance of mode2 reached 0.06 and the full width at half maximum was only 13 nm. Mode2 is located at a resonant wavelength equal to 986nm, consistent with the location of the transmission trough of SR 4. Mode1 is located at a resonant wavelength equal to 1230nm, consistent with the location of the transmission trough of SR 3. Meanwhile, in other wavelength ranges, a passband state is exhibited, and the maximum transmittance reaches 0.93. Therefore, the structure has good band-stop filtering function and can effectively select the wavelength.

As shown in fig. 4, the coupling distance g between the opposite semicircular ring and the waveguide is changed, and g is 10nm, 15nm, 20nm and 25 nm. As can be seen from the transmission lines in fig. four, in the case of four different coupling distances, the transmission lines are blue-shifted with the increase of the coupling distance, i.e. the resonant wavelengths corresponding to mode1 and mode2 are shifted to short wavelengths. The transmission line decreases from a peak to a trough becoming steeper as the coupling distance increases.

As shown in fig. 5(a) and 5(b), the transmittance and the full width at half maximum of the modes 1 and 2 are related to the coupling distance g. It is clear from the figure that the half widths of the two modes are narrowest with better wavelength selectivity at a coupling distance of 25 nm. But at the same time, the transmittance is also increased. For mode1, the transmittance remains below 0.2, but the transmittance of mode2 has risen above 0.2. This is because when the coupling distance increases, the coupling strength of the SPPs in the concentric double semicircular waveguide resonant cavity and the linear waveguide cavity 5 decreases, the energy that the concentric double semicircular waveguide resonant cavity can locally decrease, and the energy transmitted to the output port through the linear waveguide cavity 5 gradually increases. In these four cases, mode2 has a smaller full width at half maximum and a smaller transmittance than mode 1. When g is 10nm, the full width at half maximum is 43nm, and the transmittance of the trough is 0.01. When g is 25nm, the full width at half maximum is 8nm, and the transmittance is 0.15. It can be seen that the increase of the coupling distance is used to compress the bandwidth of the narrow-band-stop filter, which inevitably results in the increase of the transmittance. In order to obtain good filtering performance, two performance indexes must be balanced when selecting the structural parameters, so that a compromise effect is achieved.

With the other parameter settings kept consistent, the value of the medium refractive index was increased in steps of 0.02nm, with the corresponding transmission lines as shown in FIG. 6. It can be seen that as the refractive index n of the dielectric material in the structure gradually increases, the resonance wavelength shifts toward the long wavelength. The center wavelength of the narrow-band stop has a good linear relation with the refractive index of the medium. Tuning of the filter transfer characteristic can therefore be achieved using this phenomenon. When the refractive index was increased from 1 to 1.06, the resonance wavelength for mode1 changed from 1230nm to 1302nm, and the sensitivity was calculated to be 1200 nm/RIU. Therefore, the structure has a great application value in the aspect of refractive index sensing detection.

The result shows that the structure can also realize the dual-mode dual-channel band-stop filtering function, and the narrow-band central wavelengths of the dual-mode dual-channel band-stop filtering function are respectively 986nm and 1230 nm. The transmittance of the mode1 is 0.13, and the half width of the stop band is 21 nm; the transmittance of mode2 is 0.06 and the stop band full width at half maximum is only 13 nm. Compared with a circular ring structure and an intersected circular ring structure, the filtering performance of the filter is improved. The structure has potential application prospect in the aspect of all-optical narrow-band-stop filters.

By designing the filtering structure with the semicircular ring cavities on the same side, better filtering performance is obtained. The half-height widths of stop bands corresponding to the two modes of the structure are respectively 21nm and 13nm, and the transmittance is respectively 0.13 and 0.06. The result shows that the semicircular ring structure on the same side has higher quality factor and is more suitable for being used as a narrow-band-stop filter. Meanwhile, compared with a circular ring structure and a crossed circular ring structure, the narrow-band-stop filtering performance of the structure is improved to a certain extent.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.