Four-port photonic crystal circulator

Abstract

The utility model discloses a four-port photonic crystal circulator, which comprises a photonic crystal main body, transmission waveguides and two ferrite magneto-optical media, and is characterized in that the transmission waveguides comprise a first waveguide, a second waveguide, a third waveguide, a fourth waveguide and a fifth waveguide which are distributed in the photonic crystal main body; one ends of the first waveguide, the second waveguide and the third waveguide are connected and intersected to form a first Y-shaped waveguide channel; the other end of the third waveguide is connected and intersected with one end of the fourth waveguide and one end of the fifth waveguide to form a second Y-shaped waveguide channel; the other ends of the first waveguide, the second waveguide, the fourth waveguide and the fifth waveguide are respectively provided with a port; one ferrite magneto-optical medium is arranged at the intersection of the first Y-shaped waveguide channel, and the other ferrite magneto-optical medium is arranged at the intersection of the second Y-shaped waveguide channel. The circulator has the advantages of high isolation, low loss and ultra wide band, is easy to integrate, can reduce the light intensity, avoids the nonlinear effect of an integrated light circuit in a light band, and has potential application prospects in a 5G communication system.

Description

Technical Field

[0001] The utility model relates to the technical field of circulators, in particular to a four-port photonic crystal circulator. Background Art

[0002] A circulator is a three-port, four-port or multi-port microwave ferrite device that realizes the unidirectional circulation of microwave signals. The circulator can be used to realize the duplexing, decoupling, protection and matching functions of microwave networks. In radar antenna feed systems, the typical application is to play the role of matching, circulation and duplexing in the transmitting-antenna-receiving system.

[0003] The existing three-port "windmill-type" two-dimensional magneto-photonic crystal introduces an array of air holes in bismuth iron garnet (BIG), and its 30dB isolation bandwidth at 1550nm is estimated to be 12.6GHz. However, the isolation and insertion loss of the circulator of this structure are not ideal, with low isolation and high insertion loss, and the performance still needs to be improved; in addition, the working bandwidth of this circulator is limited, and the working bandwidth of the photonic crystal circulator may be subject to certain restrictions, that is, efficient optical transmission and isolation can only be achieved within a specific frequency range, which may limit its use in certain broadband applications. Utility Model Content

[0004] The main purpose of the utility model is to provide a four-port photonic crystal circulator, aiming to solve the technical problems of large insertion loss, low isolation and limited working bandwidth of the current photonic crystal circulator.

[0005] To achieve the above object, the utility model proposes a four-port photonic crystal circulator, which comprises:

[0006] Photonic crystal body;

[0007] A transmission waveguide, comprising a first waveguide, a second waveguide, a third waveguide, a fourth waveguide and a fifth waveguide distributed in the photonic crystal body; one end of the first waveguide, the second waveguide and the third waveguide are connected and intersected to form a first Y-shaped waveguide channel; the other end of the third waveguide is connected and intersected with one end of the fourth waveguide and the fifth waveguide to form a second Y-shaped waveguide channel; the other ends of the first waveguide, the second waveguide, the fourth waveguide and the fifth waveguide respectively have ports;

[0008] Two ferrite magneto-optical media, one of which is arranged at the connection and intersection of the first waveguide, the second waveguide and the third waveguide, and the other is arranged at the connection and intersection of the third waveguide, the fourth waveguide and the fifth waveguide.

[0009] In some embodiments, the ferrite magneto-optical medium includes a first ferrite magneto-optical medium column and a second ferrite magneto-optical medium column which are arranged opposite to each other along the thickness direction of the photonic crystal body.

[0010] In some embodiments, the first ferrite magneto-optical dielectric column and the second ferrite magneto-optical dielectric column are selected from nickel-zinc ferrite columns; and / or, the first ferrite magneto-optical dielectric column and the second ferrite magneto-optical dielectric column are cylindrical.

[0011] In some embodiments, an impedance matcher is also included, and the ferrite magneto-optical medium is fixed at the intersection of the first Y-shaped waveguide channel and the intersection of the second Y-shaped waveguide channel through two impedance matchers respectively.

[0012] In some embodiments, the impedance matcher includes a first impedance matching plate and a second impedance matching plate that are spaced apart and arranged opposite to each other along the thickness direction of the photonic crystal body, and the ferrite magneto-optical medium is clamped and fixed between the first impedance matching plate and the second impedance matching plate.

[0013] In some embodiments, the first impedance matching plate and the second impedance matching plate are selected from any one of a metal plate and a metal oxide plate; and / or the first impedance matching plate and the second impedance matching plate are any one of a polygonal, circular, and elliptical shape.

[0014] In some embodiments, the adjacent waveguide angles among the first waveguide, the second waveguide and the third waveguide are 120°; the adjacent waveguide angles among the third waveguide, the fourth waveguide and the fifth waveguide are 120°.

[0015] In some embodiments, the photonic crystal body includes four photonic crystal arrays arranged at intervals.

[0016] In some embodiments, the photonic crystal array is composed of a plurality of dielectric columns arranged in an array; the dielectric columns are cylindrical or prismatic in shape, and / or the dielectric columns are selected from aluminum oxide ceramic columns, silicon oxide ceramic columns, and gallium arsenide ceramic columns.

[0017] In some embodiments, the radius of the dielectric column r=0.2857a, where a is the center distance between adjacent dielectric columns in the photonic crystal body.

[0018] The four-port photonic crystal circulator of the technical solution of the utility model comprises a photonic crystal body, a transmission waveguide and two ferrite magneto-optical media, wherein the transmission waveguide comprises a first waveguide, a second waveguide, a third waveguide, a fourth waveguide and a fifth waveguide distributed in the photonic crystal body, one end of the first waveguide, the second waveguide and the third waveguide are connected and intersected to form a first Y-shaped waveguide channel; the other end of the third waveguide is connected and intersected with one end of the fourth waveguide and the fifth waveguide to form a second Y-shaped waveguide channel, thereby forming a double Y-shaped transmission waveguide connected by the third waveguide; the other ends of the first waveguide, the second waveguide, the fourth waveguide and the fifth waveguide respectively have ports; one of the two ferrite magneto-optical media is arranged at the connection intersection of the first waveguide, the second waveguide and the third waveguide, that is, the intersection of the first Y-shaped waveguide channel, and the other is arranged at the connection intersection of the third waveguide, the fourth waveguide and the fifth waveguide, that is, the intersection of the second Y-shaped waveguide channel. The four-port photonic crystal circulator has a simple structure. By constructing a double Y-shaped transmission waveguide connected by a third waveguide, it has an ultra-wide photonic band gap (PBG) and high transmission efficiency, which can reduce the insertion loss of the four-port photonic crystal circulator; in addition, ferrite magneto-optical media are respectively arranged at the intersection of the first Y-shaped waveguide channel and the second Y-shaped waveguide channel in the transmission waveguide. Under the drive of an external DC magnetic field, the ferrite magneto-optical medium can not only act as a resonant cavity, but also provide the required Faraday rotation, thereby achieving high isolation. The circulator constructed by the above structure has high isolation, low loss and ultra-wideband, and is easy to integrate. It can not only reduce the light intensity and avoid the nonlinear effect of the integrated optical circuit in the optical band, but also because of its ultra-wideband characteristics, it provides possibilities for various cutting-edge applications with high speed and low latency in 5G millimeter wave communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a top view of a four-port photonic crystal circulator in an embodiment of the utility model after the upper shell is uncovered;

[0020] Figure 2 for Figure 1 The schematic diagram of the structure of the ferrite magneto-optical medium and the impedance matcher in the four-port photonic crystal circulator shown;

[0021] Figure 3 for Figure 2 A one-view structural diagram of the matching structure of the ferrite magneto-optical medium and the impedance matcher shown;

[0022] Figure 4 This is a simulation diagram of signal propagation of a four-port photonic crystal circulator under the action of a bias magnetic field (intensity H0 = 376.99 mT) in a performance test experiment;

[0023] Figure 5The graph is a graph showing the variation of external characteristic parameters (i.e., isolation and insertion loss) of port 1 of a four-port photonic crystal circulator as an input port with respect to frequency;

[0024] Figure 6 The graph is a graph showing the variation of external characteristic parameters (i.e., isolation and insertion loss) of the port 2 of the four-port photonic crystal circulator as the input port with respect to frequency;

[0025] Figure 7 The waveguide transmission efficiency of the four-port photonic crystal circulator varies with frequency when w = 2h = 8.64 mm;

[0026] Figure 8 The transmission efficiency variation curve of the transmission waveguide of the four-port photonic crystal circulator at different frequencies due to the size variation;

[0027] Fig. 9 Plots of the experimental setup and results for measuring the losses of a sub-miniature A-type (SMA) connector and a waveguide-to-coaxial converter, the reflection properties of a triangular lattice photonic crystal host, and the transmission efficiency of a photonic crystal transmission waveguide.

[0028] Description of Figure Numbers:

[0029] Label name Label name 10 Photonic crystal body 30 Ferrite magneto-optical media 11 Photonic Crystal Array 31 The first ferrite magneto-optical medium column 20 Transmission waveguide 32 Second ferrite magneto-optical medium column 21 First Waveguide 40 Impedance Matching Box 22 Second waveguide 41 The first impedance matching board 23 The third waveguide 42 Second impedance matching board 24 The fourth waveguide 50 case 25 Fifth Waveguide 51 Lower shell 26 port

[0030] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the scheme in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0032] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0033] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0034] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0035] The present invention provides a four-port photonic crystal circulator. Figures 1 to 3 The four-port photonic crystal circulator includes a photonic crystal body 10, a transmission waveguide 20 and two ferrite magneto-optical media 30, wherein the transmission waveguide 20 includes a first waveguide 21, a second waveguide 22, a third waveguide 23, a fourth waveguide 24 and a fifth waveguide 25 distributed in the photonic crystal body 10; one end of the first waveguide 21, the second waveguide 22 and the third waveguide 23 are connected and intersected to form a first Y-shaped waveguide channel; the other end of the third waveguide 23 is connected and intersected with the other ends of the fourth waveguide 24 and the fifth waveguide 25 to form a second Y-shaped waveguide channel; the other ends of the first waveguide 21, the second waveguide 22, the fourth waveguide 24 and the fifth waveguide 25 have ports respectively; one of the two ferrite magneto-optical media 30 is arranged at the connection intersection of the first waveguide 21, the second waveguide 22 and the third waveguide 23, and the other is arranged at the connection intersection of the third waveguide 23, the fourth waveguide 24 and the fifth waveguide 25.

[0036] In some embodiments, the four-port photonic crystal circulator is further configured with a housing 50, the housing 50 includes an upper shell layer (not shown in the figure) and a lower shell layer 51 which are arranged opposite to each other at intervals, and the photonic crystal body 10 is arranged between the upper shell layer and the lower shell layer 51. Of course, in some embodiments, the four-port photonic crystal circulator can be configured in combination with other device structures, and then the four-port photonic crystal circulator can be directly constructed on the device structure that cooperates with it, and the configuration of the housing of the four-port photonic crystal circulator itself is omitted.

[0037] The first waveguide 21, the second waveguide 22 and the third waveguide 23 in the transmission waveguide 20 are connected and intersected at one end to form a first Y-shaped waveguide channel; the other end of the third waveguide 23 is connected and intersected with one end of the fourth waveguide 24 and the fifth waveguide 25 to form a second Y-shaped waveguide channel, and thus the transmission waveguide 20 is a double Y-shaped structure connected by the third waveguide 23 and symmetrical relative to the center of the third waveguide 23. The double Y-shaped waveguide constructed by the third waveguide 23 has an ultra-wide photonic band gap and high transmission efficiency, which can be beneficial to the four-port photonic crystal circulator to achieve low insertion loss.

[0038] In some embodiments, the adjacent waveguide angles between the first waveguide 21, the second waveguide 22 and the third waveguide 23 in the transmission waveguide 20 are 120°, and the adjacent waveguide angles between the third waveguide 23, the fourth waveguide 24 and the fifth waveguide 25 are 120°. That is, the angles between the first waveguide 21 and the second waveguide 22 and the third waveguide 23 are 120°, and the angles between the second waveguide 22 and the third waveguide 23 are also 120°; the angles between the third waveguide 23 and the fourth waveguide 24 and the fifth waveguide 25 are 120°, and the angles between the fourth waveguide 24 and the fifth waveguide 25 are also 120°. Since the electromagnetic wave enters the waveguide from the port (i.e., the waveguide port), it will be deflected by 120° based on the Faraday rotation after passing through the ferrite magneto-optical medium 30. By setting the transmission waveguide 20 structure as above, the angles between adjacent waveguides are controlled to be 120°, which can effectively reduce reflection, improve transmission efficiency, and reduce insertion loss. Of course, in some embodiments, the adjacent waveguide angles between the first waveguide 21, the second waveguide 22 and the third waveguide 23 in the transmission waveguide 20 may be controlled not to be 120°, and / or the adjacent waveguide angles between the third waveguide 23, the fourth waveguide 24 and the fifth waveguide 25 may be controlled not to be 120°.

[0039] In addition, the other ends of the first waveguide 21, the second waveguide 22, the fourth waveguide 24 and the fifth waveguide 25 in the transmission waveguide 20 respectively have ports 26, i.e., waveguide ports. Each waveguide port is located on the four outer end faces of the photonic crystal body 10, and the waveguide port is generally located at the center of the outer end face.

[0040] In some embodiments, the photonic crystal body 10 includes four photonic crystal arrays 11 arranged at intervals. The photonic crystal array 11 can be designed to have a triangular lattice structure. Based on the transmission waveguide 20 being a double Y-shaped structure connected by a third waveguide 23, the photonic crystal body 10 includes two photonic crystal arrays 11 located on both sides of the third waveguide and arranged oppositely, and two photonic crystal arrays 11 located at both ends of the third waveguide and arranged oppositely. In some embodiments, the photonic crystal array 11 is composed of a plurality of dielectric columns arranged in an array, and the dielectric column can be any one of a cylindrical and a prismatic shape; and / or, the dielectric column is selected from any one of an aluminum oxide ceramic column, a silicon oxide ceramic column, and a gallium arsenide ceramic column. Among them, the dielectric column preferably adopts a cylindrical dielectric column to reduce insertion loss. The background medium of the photonic crystal array 11 can be air.

[0041] Of course, in some embodiments, the dielectric columns in the photonic crystal array 11 may also be air columns, and then the photonic crystal body 10 is composed of four air column arrays arranged at intervals in the dielectric material, and the dielectric material may be gallium nitride material or other materials. However, compared with using an air column array to construct the photonic crystal body 10, using an array of dielectric columns arranged at intervals to construct the photonic crystal body 10 has lower insertion loss and higher isolation.

[0042] In some embodiments, the radius of the dielectric column in the photonic crystal body 10 can be designed to be r=0.2857a, where a is the center distance between adjacent dielectric columns in the photonic crystal body 10. For example, the center distance between adjacent dielectric columns in the photonic crystal body 10 can be designed to be 3.5 mm, and the radius of the dielectric column is 1 mm.

[0043] Of the two ferrite magneto-optical media 30, one ferrite magneto-optical medium 30 is arranged at the connection intersection of the first waveguide 21, the second waveguide 22 and the third waveguide 23, that is, the intersection of the first Y-shaped waveguide channel, and the other ferrite magneto-optical medium 30 is arranged at the connection intersection of the third waveguide 23, the fourth waveguide 24 and the fifth waveguide 25, that is, the intersection of the second Y-shaped waveguide channel. By arranging the ferrite magneto-optical medium 30 at the Y-shaped intersection in the double Y-shaped transmission waveguide, under the drive of the external DC magnetic field, the ferrite magneto-optical medium 30 can not only act as a resonant cavity, but also provide the required Faraday rotation, thereby achieving high isolation. The two ferrite magneto-optical media 30 can be specifically arranged at the intersection center of the first Y-shaped waveguide channel and the intersection center of the second Y-shaped waveguide channel, respectively, to effectively improve the transmission efficiency and reduce the loss.

[0044] Reference Figure 2 and Figure 3 In some embodiments, the ferrite magneto-optical medium 30 may be designed to include a first ferrite magneto-optical medium column 31 and a second ferrite magneto-optical medium column 32 that are spaced and arranged relatively along the thickness direction of the photonic crystal body 10, so as to better form impedance matching and improve transmission efficiency. In addition, the first ferrite magneto-optical medium column 31 and the second ferrite magneto-optical medium column 32 may be selected from nickel-zinc ferrite columns; and / or, the first ferrite magneto-optical medium column 31 and the second ferrite magneto-optical medium column 32 may be cylindrical. Of course, in some embodiments, the ferrite magneto-optical medium 30 may also adopt a single ferrite magneto-optical medium column or a ferrite magneto-optical medium tube or a ferrite magneto-optical medium ball.

[0045] In some embodiments, the four-port photonic crystal circulator further includes an impedance matcher 40, and the ferrite magneto-optical medium 30 is fixed at the intersection of the first Y-shaped waveguide channel and the intersection of the second Y-shaped waveguide channel through the impedance matcher 40. That is, it specifically includes two impedance matchers 40, one of the two ferrite magneto-optical media 30 is fixed at the intersection of the first Y-shaped waveguide channel through an impedance matcher 40, and the other ferrite magneto-optical medium 30 is fixed at the intersection of the second Y-shaped waveguide channel through another impedance matcher 40. Specifically, the impedance matcher 40 can generally be fixed on the housing 50 corresponding to the intersection of the first Y-shaped waveguide channel and the intersection of the second Y-shaped waveguide channel, and the ferrite magneto-optical medium 30 is fixed on the impedance matcher 40 and configured at the intersection of the first Y-shaped waveguide channel and the intersection of the second Y-shaped waveguide channel. By setting the impedance matcher 40, signal reflection can be reduced, thereby reducing insertion loss and improving transmission efficiency.

[0046] Reference Figure 2 and Figure 3 In some embodiments, the impedance matcher 40 includes a first impedance matching plate 41 and a second impedance matching plate 42 which are arranged opposite to each other along the thickness direction of the photonic crystal body 10, and the ferrite magneto-optical medium 30 is sandwiched and fixed between the first impedance matching plate 41 and the second impedance matching plate 42. Specifically, the intersection of the first Y-shaped waveguide channel and the intersection of the second Y-shaped waveguide channel can be configured with the first impedance matching plate 41 and the second impedance matching plate 42, and the first impedance matching plate 41 and the second impedance matching plate 42 can be fixed to the upper shell layer and the lower shell layer 51 of the housing 50, respectively, and the ferrite magneto-optical medium 30 is fixed on the first impedance matching plate 41 and the second impedance matching plate 42 and is configured at the intersection of the Y-shaped waveguide channel, and then the ferrite magneto-optical medium 30 is sandwiched between the first impedance matching plate 41 and the second impedance matching plate 42. In some embodiments, the ferrite magneto-optical medium 30 includes a first ferrite magneto-optical medium column 31 and a second ferrite magneto-optical medium column 32 which are arranged relative to each other along the thickness direction of the photonic crystal body 10, and then the first ferrite magneto-optical medium column 31 can be fixed to the first impedance matching plate 41, and the second ferrite magneto-optical medium column 32 can be fixed to the second impedance matching plate 42. In order to minimize the interference with the transmission of electromagnetic waves, the first impedance matching plate 41 and the second impedance matching plate 42 can be arranged perpendicular to the thickness direction of the photonic crystal body 10. In some embodiments, the first impedance matching plate 41 and the second impedance matching plate 42 can be any one of a metal plate and a metal oxide plate; wherein the metal plate can be specifically an aluminum plate, a zinc plate, a nickel plate, an iron oxide plate, etc., preferably an aluminum plate, so as to reduce the cost, ensure good impedance matching, and improve the transmission efficiency. In addition, the first impedance matching plate 41 and the second impedance matching plate 42 can be any one of a circle, an ellipse, and a polygon, wherein the polygon can be a triangle, a quadrilateral, a hexagon, etc.

[0047] Performance test example

[0048] In order to examine the performance characteristics of the above four-port photonic crystal circulator, the inventor constructed a four-port photonic crystal circulator according to the above structure during the actual research process, and performed performance tests on the product four-port photonic crystal circulator. Some of the four-port photonic crystal circulators constructed by the inventor and some of the performance test experiments conducted are listed as follows:

[0049] Reference Figure 1 and Figure 2 The structure shown constructs a four-port photonic crystal circulator, which includes a housing 50 , a photonic crystal body 10 , a transmission waveguide 20 , two ferrite magneto-optical media 30 and two impedance matchers 40 .

[0050] The shell 50 specifically includes an upper shell layer and a lower shell layer 51 which are arranged opposite to each other at an interval; the photonic crystal body 10 is disposed between the upper shell layer and the lower shell layer 51 of the shell 50 .

[0051] The photonic crystal body 10 includes four photonic crystal arrays 11 arranged at intervals. The photonic crystal array is specifically composed of dielectric columns arranged in an array in an air background. The dielectric columns are cylindrical alumina ceramic columns. The center distance between adjacent dielectric columns in the photonic crystal body 10 is 3.5 mm, the radius of the dielectric column is 1 mm, and the dielectric constant of the dielectric column is 9.2.

[0052] The transmission waveguide 20 includes a first waveguide 21, a second waveguide 22, a third waveguide 23, a fourth waveguide 24 and a fifth waveguide 25 sandwiched between adjacent photonic crystal arrays 11; one end of the first waveguide 21, the second waveguide 22 and the third waveguide 23 are connected and intersected to form a first Y-shaped waveguide channel; the other end of the third waveguide 23 is connected and intersected with the other ends of the fourth waveguide 24 and the fifth waveguide 25 to form a first Y-shaped waveguide channel; the adjacent waveguide angles between the first waveguide 21, the second waveguide 22 and the third waveguide 23 are 120°, and the adjacent waveguide angles between the third waveguide 23, the fourth waveguide 24 and the fifth waveguide 25 are 120°; the other ends of the first waveguide 21, the second waveguide 22, the fourth waveguide 24 and the fifth waveguide 25 respectively have ports 26. Specifically, the port 26 corresponding to the second waveguide 22 can be used as Port 1, i.e., Port 1; the port 26 corresponding to the fourth waveguide 24 can be used as Port 2, i.e., Port 2; the port 26 corresponding to the fifth waveguide 25 can be used as Port 3, i.e., Port 3; the port 26 corresponding to the first waveguide 21 can be used as Port 4, i.e., Port 4. The ports are respectively located at the four peripheral end faces of the photonic crystal body 10, and the port is located at the center of the peripheral end face.

[0053] The two ferrite magneto-optical media 30 are respectively arranged at the intersection center of the first Y-shaped waveguide channel and the intersection center of the second Y-shaped waveguide channel, which include a first ferrite magneto-optical medium column 31 and a second ferrite magneto-optical medium column 32 arranged at intervals along the thickness direction of the photonic crystal body 10. The first ferrite magneto-optical medium column 31 and the second ferrite magneto-optical medium column 32 are both cylindrical nickel-zinc ferrite columns.

[0054] The impedance matcher 40 includes a first impedance matching plate 41 and a second impedance matching plate 42 which are arranged relative to each other along the thickness direction of the photonic crystal body 10. The first impedance matching plate 41 and the second impedance matching plate 42 are arranged perpendicular to the thickness direction of the photonic crystal body 10, and are respectively fixed to the upper shell layer and the lower shell layer 51 of the shell 50 corresponding to the intersection center of the Y-shaped waveguide channel (including the first Y-shaped waveguide channel and the second Y-shaped waveguide channel). The first impedance matching plate 41 and the second impedance matching plate 42 are both triangular aluminum plates; the first ferrite magneto-optical medium column 31 of the ferrite magneto-optical medium 30 is fixed on the first impedance matching plate 41, and the second ferrite magneto-optical medium column 32 is fixed on the second impedance matching plate 42. The first ferrite magneto-optical medium column 31 and the second ferrite magneto-optical medium column 32 are arranged at intervals along the thickness direction of the photonic crystal body 10.

[0055] The performance of the four-port photonic crystal circulator constructed above was tested.

[0056] The signal propagation of the above four-port photonic crystal circulator under the bias magnetic field (intensity H0 = 376.99 mT) is shown in Figure 4 As shown, Figure 4 (a) is a schematic diagram of the model structure of a four-port photonic crystal circulator; (b) is a simulation diagram of the electromagnetic field propagation from port 1 to port 2 in a four-port photonic crystal circulator; (c) is a simulation diagram of the electromagnetic field propagation from port 2 to port 3 in a four-port photonic crystal circulator. Figure 4 As shown in (b), under the bias magnetic field (intensity H0 = 376.99 mT), the propagation direction of the signal rotates 120° in the first ferrite magneto-optical medium area, and rotates 120° again in the second ferrite magneto-optical medium area, thereby realizing the function of the double Y-shaped photonic crystal circulator. The signal is stably transmitted from port 1 to port 2, and ports 3 and 4 are isolated. Figure 4 As shown in (c), the signal enters from port 2, rotates 120° in the second ferrite magneto-optical medium area, and is transmitted to port 3, while port 1 and port 4 are isolated.

[0057] Based on the Maxwell equation of the magnetic permeability tensor, the finite element method is used to calculate the function and transmission characteristics of the magneto-photonic crystal circulator. The calculation area includes about 1.06 million grid cells, and the grid cells are surrounded by scattering boundary conditions (SBC). When port 1 is used as the input port, the isolation and insertion loss calculation results of the designed circulator in the frequency range of 18 to 32 GHz are shown in Figure 2. Figure 5 When port 2 is used as the input port, the isolation and insertion loss calculation results of the designed circulator in the frequency range of 18 to 32 GHz are shown in Figure 6 shown.

[0058] exist Figure 5 In the experiment, when the frequency is 26.10GHz, the insertion loss of the magneto-photonic crystal circulator from port 1 to port 2 changes to S21, which is as low as 0.42dB. From port 3 to port 1, at 24.71GHz, the best isolation is 46.14dB, the circulator bandwidth covers 23.66~28.63GHz, and the isolation is less than 20dB. The best isolation from port 4 to port 1 is 48.60dB at 26.40GHz, and the circulator bandwidth is 24.40~27.28GHz.

[0059] exist Figure 6 In the figure, the isolation of the magneto-photonic crystal circulator from port 1 to port 2 reaches 74.86dB at 25.10GHz, and the isolation from port 4 to port 2 reaches 43.10dB at 24.80GHz. When the center frequency is 26.10GHz, the insertion loss of the circulator is as low as 0.38dB. It can be seen that the four-port photonic crystal circulator designed above has significantly high isolation and low loss.

[0060] In the field of 5G ultra-wideband, it is possible to reduce the light intensity in the optical band and avoid the nonlinear effects of integrated optical circuits that affect the transmission efficiency of light waves. Therefore, it is particularly important to design a high-transmission photonic crystal waveguide with an ultra-wide photonic bandgap to achieve low-loss ultra-wideband. The present application places two triangular aluminum plates at the Y-shaped intersection center of the double Y-shaped photonic crystal transmission waveguide, and uses an impedance matching widening method to form an impedance matching transformer. By combining the bandwidth widening technology of the waveguide circulator with the photonic crystal circulator, in numerical simulations, the relative bandwidth widening of the four-port photonic crystal circulator is 28.48%. By designing a high-transmission photonic crystal transmission waveguide with an ultra-wide photonic bandgap, an ultra-wideband photonic crystal circulator with low insertion loss is realized. As Figure 7As shown, the transmission efficiency of the photonic crystal transmission waveguide increases with the increase of its width w and height h. When w>6.9 mm, the transmission efficiency of electromagnetic waves in the range of 24 to 28 GHz is above -1dB (about 79.43%). When w is greater than 7.5 mm, the electromagnetic wave transmission efficiency of 26 GHz is higher than that of 24 GHz, 25 GHz and 28 GHz, but less than 27 GHz. When w>8.2 mm, the electromagnetic wave transmission efficiency of 26 GHz is higher than that of other frequency bands. The inventor has designed a photonic crystal transmission waveguide whose transmission efficiency varies with frequency. Figure 8 The simulation was performed as shown. Two diagrams of electromagnetic field distribution are inserted in the waveguide, namely the surface distribution and the volume distribution. The best transmission efficiency reaches 92.43% (-0.295dB) at the center frequency from 26.10GHz. From 21.60GHz to 31.90GHz, the transmission efficiency of the photonic crystal waveguide remains above -3dB with a relative bandwidth of about 38.50%. These data show that the designed photonic crystal waveguide has ultra-wideband and high transmission characteristics.

[0061] In order to verify the numerical results of the above triangular lattice photonic crystal body and photonic crystal transmission waveguide, experiments were carried out using an Agilent E8361C vector network analyzer in the frequency range of 18 to 32 GHz. Fig. 9 (a), (c), and (e) show the experimental setup for measuring the loss of subminiature A-type (SMA) connectors and waveguide-to-coaxial converters, the reflection characteristics of the triangular lattice photonic crystal body, and the transmission efficiency of the photonic crystal transmission waveguide. The photonic crystal body sample and the vector network analyzer are connected through two waveguide-to-coaxial converters and a pair of SMA connectors. The corresponding experimental results are shown in Fig. 9 (b), (d), (f). The experimental results show that when the center frequency is 26.10GHz, the measured η is 90.78% (-0.42dB); the bandwidth (η>-3dB) is about 7.84GHz, and the frequency range is from 23.39 to 31.23GHz, which is consistent with Figure 7 The results of numerical calculations in the paper match the results. Confirmatory experiments have shown that the designed photonic crystal transmission waveguide has an ultra-wide operating bandwidth (relative bandwidth of 28.71%) and a peak transmission efficiency of more than 90%. In summary, this low-loss and easy-to-integrate magneto-photonic crystal circulator scheme can not only reduce the nonlinear effects of optical band integrated optical circuits, but also has potential application prospects in 5G communication systems due to its ultra-wideband characteristics of 24 to 28 GHz.

[0062] The above description is only a partial or preferred embodiment of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A four-port photonic crystal circulator, characterized in that: include: Photonic crystal body; A transmission waveguide, comprising a first waveguide, a second waveguide, a third waveguide, a fourth waveguide and a fifth waveguide distributed in the photonic crystal body; one end of the first waveguide, the second waveguide and the third waveguide are connected and intersected to form a first Y-shaped waveguide channel; the other end of the third waveguide is connected and intersected with one end of the fourth waveguide and the fifth waveguide to form a second Y-shaped waveguide channel; the other ends of the first waveguide, the second waveguide, the fourth waveguide and the fifth waveguide respectively have ports; Two ferrite magneto-optical media, one of which is arranged at the intersection of the first Y-shaped waveguide channel, and the other is arranged at the intersection of the second Y-shaped waveguide channel.

2. The four-port photonic crystal circulator according to claim 1, characterized in that: The ferrite magneto-optical medium comprises a first ferrite magneto-optical medium column and a second ferrite magneto-optical medium column which are arranged opposite to each other along the thickness direction of the photonic crystal body.

3. The four-port photonic crystal circulator according to claim 2, characterized in that: The first ferrite magneto-optical medium column and the second ferrite magneto-optical medium column are selected from nickel-zinc ferrite columns; and / or the first ferrite magneto-optical medium column and the second ferrite magneto-optical medium column are cylindrical.

4. The four-port photonic crystal circulator according to claim 1, characterized in that: It also includes an impedance matcher, and the ferrite magneto-optical medium is respectively fixed at the intersection of the first Y-shaped waveguide channel and the intersection of the second Y-shaped waveguide channel through the impedance matcher.

5. The four-port photonic crystal circulator according to claim 4, characterized in that: The impedance matcher comprises a first impedance matching plate and a second impedance matching plate which are arranged opposite to each other along the thickness direction of the photonic crystal body, and the ferrite magneto-optical medium is sandwiched and fixed between the first impedance matching plate and the second impedance matching plate.

6. The four-port photonic crystal circulator according to claim 5, characterized in that: The first impedance matching plate and the second impedance matching plate are selected from any one of a metal plate and a metal oxide plate; and / or the first impedance matching plate and the second impedance matching plate are any one of a polygonal, circular, and elliptical shape.

7. The four-port photonic crystal circulator according to any one of claims 1 to 6, characterized in that: The adjacent waveguide angles among the first waveguide, the second waveguide and the third waveguide are 120°; the adjacent waveguide angles among the third waveguide, the fourth waveguide and the fifth waveguide are 120°.

8. The four-port photonic crystal circulator according to any one of claims 1 to 6, characterized in that: The photonic crystal body includes four photonic crystal arrays arranged at intervals.

9. The four-port photonic crystal circulator according to claim 8, characterized in that: The photonic crystal array is composed of a plurality of dielectric columns arranged in an array; the dielectric columns are in any one of cylindrical and prismatic shapes, and / or the dielectric columns are selected from any one of aluminum oxide ceramic columns, silicon oxide ceramic columns, and gallium arsenide ceramic columns.

10. The four-port photonic crystal circulator according to claim 9, characterized in that: The radius of the dielectric column is r=0.2857a, where a is the center distance between adjacent dielectric columns in the photonic crystal body.

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