CN213690001U - Waveguide structure of circular ring-shaped resonant cavity with notch - Google Patents
Waveguide structure of circular ring-shaped resonant cavity with notch Download PDFInfo
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- CN213690001U CN213690001U CN202022265104.9U CN202022265104U CN213690001U CN 213690001 U CN213690001 U CN 213690001U CN 202022265104 U CN202022265104 U CN 202022265104U CN 213690001 U CN213690001 U CN 213690001U
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Abstract
The utility model relates to a waveguide structure of a circular ring-shaped resonant cavity with a notch, which comprises a substrate, a first waveguide, a second waveguide and a resonant cavity, wherein the first waveguide, the second waveguide and the resonant cavity are arranged inside the substrate; a second cavity with a second waveguide extending inward from the substrate side surface into the substrate; the resonant cavity is a circular cavity with a gap. The resonant cavity is designed into the annular cavity with the notch, so that small-area multi-channel Fano resonance is formed, the Fano resonance has the characteristics of sharpness and asymmetry, and each Fano resonance can output one function, so that the requirement of simultaneously processing data by multiple channels can be met, the parallel processing capacity and the integration level of an optical device are enhanced, and the working efficiency of an optical circuit is improved.
Description
Technical Field
The utility model relates to an optical device field, more specifically relates to a take waveguide structure of notched ring shape resonant cavity.
Background
Optical devices have been unable to implement highly integrated optical circuits due to the inherent diffraction limit of light. In recent years, surface plasmons (SPPs) generated by coupling light with a metal surface have been thought to provide researchers with a new integrated optical circuit because they can break through the diffraction limit and confine light in the sub-wavelength range. Metal-dielectric-metal (MIM) waveguide structures proposed based on SPPs attract attention and are widely used in the sub-wavelength range. Unlike lorentz resonance, Fano resonance, which arises from interference of the bright (continuous) and dark (separate) modes of the MIM waveguide structure, has an asymmetric, sharp line shape. This makes Fano resonance a huge potential for applications in many areas, such as filters, light sensors, optical switches, fast and slow light devices, etc.
Chinese patent document No. CN107976739A, published as 2018, 5.1, discloses a spectrum regulating device with resonant cavity waveguides, wherein a single/double rectangular waveguide is introduced into the resonant cavity to regulate the resonant mode of the resonant cavity, and multiple Fano resonance phenomena are realized by a bright-dark mode interference effect.
However, in the above technical solutions, the resonant cavity generates a large-area multi-channel Fano resonance, and the parallel processing capability and the integration level of the optical device are poor, so that the working efficiency requirements of some optical devices cannot be met in practical applications.
SUMMERY OF THE UTILITY MODEL
The utility model discloses an overcome the relatively poor problem of throughput and the integrated level of above-mentioned prior art well device, provide a take notched ring shape resonant cavity's waveguide structure, produce the small size multichannel and have the Fano resonance of sharp-pointed, asymmetric characteristics, reinforcing optical device's parallel throughput and integrated level.
In order to solve the technical problem, the utility model discloses a technical scheme is: a waveguide structure of a circular ring-shaped resonant cavity with a notch comprises a substrate, a first waveguide, a second waveguide and a resonant cavity, wherein the first waveguide, the second waveguide and the resonant cavity are arranged in the substrate; the second waveguide extends into a second cavity from the side surface of the substrate to the inside of the substrate, one ends of the first cavity and the second cavity, which are close to the side surface of the substrate, are both open and are respectively a first opening and a second opening, and the other ends of the first cavity and the second cavity are both closed ends and are respectively a first closed end and a second closed end; the resonant cavity is a circular cavity with a gap.
The light wave enters from the first opening of the first waveguide, after being transmitted to the first closed end along the surface of the first waveguide, the light is coupled into the resonant cavity and the second waveguide through the light guiding function of the substrate, the light is transmitted to the output end of the resonant cavity on the surface of the resonant cavity, then the light is coupled to the second closed end of the second waveguide through the function of the substrate, and the light is transmitted to the second opening of the second waveguide along the surface of the second waveguide. The light waves transmitted through the resonant cavity interfere with the light waves in the second waveguide. The substrate has the function of conducting light waves, and the position between the first waveguide and the resonant cavity and the position between the second waveguide and the resonant cavity are equivalent to the coupling parts, so that the light waves are transmitted among the first waveguide, the resonant cavity and the second waveguide.
Preferably, the first waveguide and the second waveguide are parallel to each other, and center lines of the first waveguide and the second waveguide are on the same straight line. The resonant cavity is located on one side of the first waveguide.
Preferably, the center of the resonant cavity is located on a perpendicular bisector between the first waveguide and the second waveguide. The energy in the first waveguide and the second waveguide is more easily coupled into the first resonant cavity, so that the energy loss can be reduced, and the transmission peak of the output spectrum is higher.
Preferably, the first opening and the second opening are located on two opposite sides of the substrate, respectively, i.e. the first waveguide and the second waveguide extend inwardly from the two opposite sides of the substrate. It is possible to analyze the input and output spectrogram characteristics obtained at the first waveguide and the second waveguide, respectively.
Preferably, the first waveguide and the second waveguide are both rectangular in cross section. The coupling area can be made uniform, and the influence of other factors can be reduced.
Preferably, the ends of the circular ring-shaped cavity are respectively a third closed end and a fourth closed end.
Preferably, the substrate is a silver substrate.
Preferably, a coupling resonant cavity is arranged at one side of the resonant cavity. Dark modes provided by the coupling resonant cavity interfere with bright modes provided by the circular ring resonant cavity, so that more Fano resonant peaks can be formed.
Compared with the prior art, the beneficial effects of the utility model are that: the resonant cavity is designed into a circular ring cavity with a notch, the symmetry of the whole waveguide system structure is damaged, optical paths on two sides are actually changed, when SPP enters the circular ring resonant cavity in a coupling mode, paths with different optical paths on the left side and the right side can be propagated to have different phases, the phase difference causes coherent interference of a bright mode and a dark mode, and therefore Fano resonance with small area and multiple channels is formed, the Fano resonance has the characteristics of being sharp and asymmetric, and each Fano resonance can output a function.
Drawings
Fig. 1 is a schematic structural diagram of a waveguide structure of a notched ring resonator according to the present invention.
Fig. 2 is a perspective view of a waveguide structure of a notched ring resonator according to the present invention;
fig. 3 is a schematic structural diagram of another embodiment of a waveguide structure of a notched ring resonator according to the present invention.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are the terms "upper", "lower", "left", "right", "long", "short", etc. indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore the terms describing the positional relationship in the drawings are only for illustrative purposes and are not to be construed as limiting the present patent, and those skilled in the art will understand the specific meaning of the terms according to their specific circumstances.
The technical solution of the present invention is further described in detail by the following specific embodiments in combination with the accompanying drawings:
example 1
Fig. 1-2 show an embodiment of a waveguide structure of a notched ring-shaped resonant cavity, which includes a substrate 1, and a first waveguide 2, a second waveguide 3, and a resonant cavity 4 disposed inside the substrate 1, where the first waveguide 2 is a first cavity extending from a side surface of the substrate 1 into the substrate 1; the second waveguide 3 extends from the side surface of the substrate 1 to the inside of the substrate 1, one ends of the first cavity and the second cavity close to the side surface of the substrate 1 are both open and are respectively a first opening 201 and a first opening 301, and the other ends are both closed ends and are respectively a first closed end 202 and a second closed end 302; the resonant cavity 4 is a circular ring-shaped cavity with a gap, and the tail ends of the circular ring-shaped cavity are respectively a third closed end 401 and a fourth closed end 402.
Wherein the first waveguide 2 and the second waveguide 3 are parallel to each other, and the central lines of the first waveguide 2 and the second waveguide 3 are on the same straight line. The first openings 201 and 301 are located at opposite sides of the substrate 1, respectively, i.e., the first waveguide 2 and the second waveguide 3 extend inward from the opposite sides of the substrate 1. The first waveguide 2 and the second waveguide 3 are both rectangular in cross section. The cavity 4 is located on one side of both waveguides.
Specifically, the substrate 1 is a silver substrate.
The working principle or working process of the embodiment is as follows: the light wave enters from the first opening 201 end of the first waveguide 2, after being transmitted to the first closed end 202 along the surface of the first waveguide 2, the light wave is coupled into the resonant cavity 4 and the second waveguide 3 through the substrate, the light propagates to the output end of the resonant cavity 4 on the surface of the resonant cavity 4, then the light wave is coupled to the second closed end 302 of the second waveguide 3 through the substrate, the light is transmitted to the 301 end of the second waveguide 3 along the surface of the second waveguide 3, and the light wave entering the second waveguide 3 from the resonant cavity 4 interferes with the light wave entering the second waveguide 3 from the first waveguide 2.
Wherein the resonant cavity 4 is a ring with a gap, the width of the first waveguide 2, the second waveguide 3 and the resonant cavity 4 is w, and the size is fixed in the following discussion. In fig. 1, g is a coupling distance between the first waveguide 2 or the second waveguide 3 and the resonant cavity 4. And its size is fixed in the following discussion. d is the distance between the first waveguide 2 and the second waveguide 3. And its size is fixed in the following discussion.
According to the standing wave theory derived from the dispersion formula, we can obtain the transmission wavelength of the window of the output spectrum as:
λm＝2neffL/(m-αp/2π) (1)
wherein n iseffFor the effective refractive index, L is the length of the cavity 4, m is the ordinal number of the mode, αpIs the phase shift caused by the SPP propagating in the cavity. From the equation (1), it can be seen that the width and refractive index of the resonator are constant, and the resonance is variedWith the increase of the length of the resonator, the transmission peak of the spectrum appears red-shifted, and the wavelength position of the resonance peak approximately follows 1:1/2:1/3. That is, for a larger size cavity, the higher order modes generated will be densely distributed in the short wavelength range and sparsely distributed in the long wavelength range. Therefore, by changing the magnitude of the parameter L in the formula (1), more resonance modes can occur in the wavelength ranges of the near infrared and infrared regions widely used for communication. In MIM waveguides, the Fano peak results from interference of the bright mode (continuum state) with the dark mode (discrete state). In this structure, the substrate between the first waveguide and the second waveguide is used to generate a dark mode, and the resonant cavity is used to generate a bright mode. Thus, the interference between the bright mode and the dark mode can generate Fano resonance.
Based on the design principle, the coupling distance g between the resonant cavity 4 and the waveguide is initially set to be 10nm, the widths ω of the first waveguide and the second waveguide are 50nm, the distance d between the first waveguide 2 and the second waveguide 3 is set to be 10nm, and the outer radius of the resonant cavity 4 is R1330nm, the angle θ between the initial position of the notch, i.e. the third closed end 401, and the y-axis1The angle range of the notch is 5 °, i.e. the included angle θ between the third closed end 401 and the fourth closed end 4022175. This structure is referred to as structure 1.
Verification by FDTD gave the following results: sharp Fano resonance peaks were formed around 735.6nm, 968.9nm, and 1441.7nm, and the peak transmittances were 0.6, 0.63, and 0.37, respectively. When n is changed to 1.01, the results are obtained: sharp Fano resonance peaks were formed around 741.7nm, 979.5nm, and 1455.8nm, and the peak transmittances were 0.6, 0.63, and 0.37, respectively, as shown in table 1. It can thus be seen that the three Fano peaks all appear red-shifted with approximately no change in peak transmission. In practical applications, the change in refractive index can be detected by detecting the wavelength change of light, and thus this phenomenon is used in applications such as photo-sensing, photo-detection, and the like. In addition, the group delay is also an important parameter for evaluating the Fano resonance characteristics.
TABLE 1 variation of the peak wavelength of the formants of Structure 1 corresponding to the variation of the refractive index
Fano resonance can cause phase jumps at the peaks or troughs, thus creating positive and negative delays. The phase response may be verified by FDTD. And group delay is represented by
Can be obtained. Where c is the speed of light, P is the phase response, and λ is the corresponding wavelength. The delay characteristics of structure 1 are shown in table 2. Corresponding to this characteristic, the structure 1 can be used in fast or slow light devices. In practical applications of integrated optical circuits, a multi-channel Fano peak structure is often required to achieve the requirement of multi-channel simultaneous output.
TABLE 2 time delay at peak and trough of structure 1 formant
Based on the above analysis, if it is desired to increase the number of Fano resonant channels in the 600-1800 nm wavelength range, the θ can be changed2And R1So that L in the transmission theory formula is varied, thereby increasing the number of Fano peaks generated by interference of the bright and dark modes. That is, the outer radius of the resonant cavity 4 can be set to R1500nm, the angle θ between the start of the notch, i.e. the third closed end 401, and the y-axis1The angle range of the notch is 5 °, i.e. the included angle θ between the third closed end 401 and the fourth closed end 402220 deg. is equal to. This structure may be designated as structure 2. Verification by FDTD produced 9 asymmetric Fano resonances in its output spectrum. The wavelength and transmittance are shown in table 3.
TABLE 3 Structure 2 wavelength and transmittance corresponding thereto
By varying the parameter θ of the cavity compared to the results of structure 12And R1Then, more multi-channel Fano resonances are realized. In order to better evaluate the performance of these Fano resonances in practical applications, the structure 2 was also studied for the wavelength change at which the peak is located when the refractive index changes and the time delay characteristics caused by the phase jump generated by the Fano resonances. Structure 2 change refractive index the wavelength change at which the structure corresponds to the peak of the transmission peak is shown in table 4.
TABLE 4 variation of the peak wavelength of the formant of Structure 2 corresponding to the variation of the refractive index
The delay characteristics of structure 2 are shown in table 5. The minimum value of negative delay generated at the trough is-0.285 ps, and the maximum positive delay generated at the peak is 0.147 ps.
TABLE 5 time delay at peak and trough of structure 2 formant
The structure 2 implements multiple-channel Fano resonance and is therefore useful in integrated optical circuits requiring multiple channel outputs. Corresponding to the red shift of the Fano resonance peak value when the refractive index is changed and the positive and negative time delays generated by the resonance peak and the resonance trough as shown in tables 4 and 5, the structure 2 can be widely applied to the fields of optical detectors, optical switches, fast light and slow light devices and the like.
The beneficial effects of this embodiment: the resonant cavity is designed into a circular ring cavity with a notch, the symmetry of the whole waveguide system structure is damaged, optical paths on two sides are actually changed, when SPP enters the circular ring resonant cavity in a coupling mode, paths with different optical paths on the left side and the right side can be propagated to have different phases, the phase difference causes coherent interference of a bright mode and a dark mode, and therefore Fano resonance with small area and multiple channels is formed, the Fano resonance has the characteristics of being sharp and asymmetric, and each Fano resonance can output a function.
Fano resonances are characterized by sharp, asymmetric features and are sensitive to refractive index changes. The Fano resonance has the sharp characteristic, so that the filtering of light waves with specific wavelengths can be realized, and the filtering effect is realized; by utilizing the characteristic that the Fano resonance in the utility model is sensitive to the change of the gas refractive index, the change of the gas refractive index can be detected, thereby being applicable to the fields of optical switches, sensors and the like; there is a time delay effect near the Fano resonance and thus can be used for slow light devices. Therefore, the optical device can be used in the fields of optical devices for multi-channel information processing and output, such as filters, sensors, optical switches, fast light and slow light devices and the like.
Example 2
As shown in fig. 3, another embodiment of a waveguide structure of a notched ring resonator is shown, and this embodiment differs from embodiment 1 in that a coupling resonator cavity 5 is provided on one side of a resonator cavity 4. The dark mode provided by the coupling resonant cavity 5 interferes with the bright mode provided by the ring resonator 4, so that more Fano resonant peaks can be formed.
The working principle or working process of the embodiment is as follows: the parameters of the coupled resonant cavity 5 are set as follows: l is1＝750nm、g115 nm. By means of the arrangement, new Fano resonant peaks with the transmission rates of 0.36, 0.36 and 0.23 can be formed at 109.8nm, 775nm and 1183.4nm, and 12 Fano resonant channels are formed. The wavelength and transmittance are shown in table 6:
TABLE 6 wavelengths and their corresponding transmissions
Only the Fano peak at 1147 is blue-shifted to 1113nm in the original Fano peak, and the wavelength of the rest Fano peaks is not changed greatly. The new Fano resonance is formed in that the new mode formed within the coupled resonant cavity 5 interferes with the mode originally formed in the resonant cavity 4.
The present embodiment has the following advantages compared to embodiment 1: the number of Fano resonant peaks is increased by changing the length parameter of the side coupling resonant cavity, adding a new coupling resonant cavity at the original structure to adjust the resonant mode, and increasing the effective length to increase the resonant mode sequence and enable the dark mode of the new coupling resonant cavity to interfere with the bright mode of the circular ring resonant cavity.
Other features, operating principles and advantageous effects of the present implementation are consistent with embodiment 1.
It is obvious that the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations to the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A waveguide structure of a circular ring-shaped resonant cavity with a notch comprises a substrate (1), and a first waveguide (2), a second waveguide (3) and a resonant cavity (4) which are arranged in the substrate (1), wherein the first waveguide (2) is a first cavity extending from the side surface of the substrate (1) to the substrate (1); the second waveguide (3) is a second cavity extending from the side surface of the substrate (1) to the inside of the substrate (1), one ends of the first cavity and the second cavity, which are close to the side surface of the substrate (1), are both open and are respectively a first opening (201) and a second opening (301), and the other ends are both closed ends and are respectively a first closed end (202) and a second closed end (302); the resonant cavity is characterized in that the resonant cavity (4) is a circular cavity with a gap.
2. A waveguide structure of a notched ring resonator cavity according to claim 1, characterized in that the first waveguide (2) and the second waveguide (3) are parallel to each other.
3. A waveguide structure of a notched ring resonator according to claim 2, characterized in that the center lines of the first waveguide (2) and the second waveguide (3) are on the same line.
4. A waveguide structure of a notched ring resonator according to claim 3, characterized in that the resonator (4) is located on one side of the first waveguide (2).
5. A waveguide structure of a notched ring resonator according to claim 4, characterized in that the center of the resonator (4) is located on the perpendicular bisector between the first waveguide (2) and the second waveguide (3).
6. A waveguide structure of a notched ring resonator according to claim 3, characterized in that the first opening (201) and the second opening (301) are located on two opposite sides of the substrate (1), respectively.
7. A waveguide structure of a notched ring resonator according to claim 3, characterized in that the cross-section of the first waveguide (2) and the second waveguide (3) is rectangular.
8. A waveguide structure with a notched ring resonator according to claim 1, characterized in that the ends of the ring cavity are respectively a third closed end (401) and a fourth closed end (402).
9. The waveguide structure of a notched ring resonator according to claim 1, characterized in that the substrate (1) is a silver substrate.
10. A waveguide structure of a notched ring resonator according to any of claims 1 to 9, characterized in that a coupling resonator cavity (5) is provided at one side of the resonator cavity (4).
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114171871A (en) * | 2021-11-16 | 2022-03-11 | 南京信息工程大学 | Non-contact adjustable negative group time delay circuit based on dielectric resonator and construction method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114171871A (en) * | 2021-11-16 | 2022-03-11 | 南京信息工程大学 | Non-contact adjustable negative group time delay circuit based on dielectric resonator and construction method |
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