A photonic crystal slow light waveguide with magnetically tunable operating frequency

Abstract

The present invention discloses a photonic crystal slow light waveguide with a magnetically adjustable operating frequency. The slow light waveguide comprises two photonic crystal dielectric column arrays of equal size, a parallel plate waveguide, an absorbing material, and a transmitting monopole antenna. The photonic crystal dielectric column arrays are a two-dimensional square lattice structure surrounded by absorbing material on all four sides. The photonic crystal dielectric column arrays and the absorbing material are both located between the parallel plate waveguides. The transmitting monopole antenna is located in the center region between the two photonic crystal dielectric column arrays. When an external magnetic field of equal magnitude and direction is applied, the electromagnetic waves generated by the transmitting monopole antenna can form a boundary state that propagates unidirectionally along the center region of the arrays. By adjusting the magnitude of the external magnetic field and the distance between the two photonic crystal dielectric column arrays, the operating frequency and transmission group velocity of the electromagnetic waves in the waveguide can be adjusted. The present invention has the advantages of controllable transmission speed, adjustable operating frequency, low optical loss, and a simple preparation process.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic devices, in particular to a photonic crystal slow light waveguide with magnetically adjustable operating frequency. Background Art

[0002] Since 1999, when Danish physicist LVHau and his team successfully reduced the propagation speed of a beam of waves to 17m / s, the study of slow light has attracted the attention of more and more scholars internationally, and a variety of methods for realizing slow light have been proposed. Some important progress has been made in the field of slow light research at home and abroad. In 2003, the Institute of Optics at the University of Rochester used the method of coherent layout oscillation to realize slow light at room temperature, making the study of slow light practical. In 2005, IBM announced that the waveguide prepared using photonic crystals can successfully reduce the speed of light to one-three hundredth of that in a vacuum. After the results were published in the journal Nature, they caused a strong response in the scientific community, indicating that the study of slow light has attracted the attention of more and more scholars internationally, and a variety of methods for realizing slow light have been proposed. Later, in 2007, Tsakmakidis used the negative polarity of left-handed materials to realize slow light. Taking advantage of this characteristic of displacement, a gradient one-dimensional dielectric slab waveguide was designed. Upon entering this waveguide, incident light slows down and eventually stops, with light of different frequencies stopping at different locations, creating a "trapped rainbow." This work received high praise after being published in Nature. Compared to other slow-light generation mechanisms, photonic crystal waveguides offer advantages, such as the ability to excite and generate slow light of arbitrary wavelengths at room temperature. Using photonic crystals to construct slow-wave systems has become a growing trend in recent years. Currently, research in the field of slow light is at a high level both domestically and internationally, but it also presents challenges and opportunities. On the one hand, deeper theoretical research is needed to explain the nature of slow light phenomena and the mechanisms of light-matter interactions. On the other hand, new materials and devices are also needed to meet the needs of diverse application scenarios. Future trends in slow-light research may include the following: first, exploring more slow-light materials and devices, such as graphene, two-dimensional materials, and novel photonic crystals; second, developing efficient and reliable fabrication techniques, such as controlled nucleation and growth, and interface engineering; and third, exploring new applications of slow light, such as photoelectric switches, all-optical computing, and novel sensors.

[0003] Slow light is a burgeoning research topic both domestically and internationally. Professor Li Zhiyuan of South China University of Technology constructed a slow-light waveguide using the quantum Hall effect of two identical magnetic photonic crystals. The strong coupling of the two opposite topological states significantly reduces the group velocity of electromagnetic wave propagation, allowing for the simulation of switchable slow-light capture and release. However, slow-light waveguides operate within the Bragg band gap, which can lead to the excitation of higher-order modes that are detrimental to optical and microwave devices. To address this issue, Hironobu et al. proposed a method for implementing a slow-light waveguide using valley photonic crystals, which exhibits strong robustness against backscattering and large-angle bending losses. Jonathan et al. proposed using coupling between the columns to control the properties of topological edge states, thereby generating slow light. However, the system structure is complex and difficult to implement. However, current slow-light research has not yet provided a reasonable solution to the problem of full-bandwidth operation of optical waveguides. This present invention addresses the current narrow bandwidth of slow-light waveguides by proposing a magnetically tunable operating frequency method to achieve broadband operation, significantly expanding the operating frequency range of slow-light waveguides. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a photonic crystal slow light waveguide with magnetically tunable operating frequency, which has the advantages of controllable transmission speed, adjustable operating frequency, low optical loss, and simple preparation process.

[0005] Technical solution: In order to achieve the above-mentioned purpose, the present invention adopts the following technical solution:

[0006] A photonic crystal slow light waveguide with magnetically adjustable operating frequency comprises two photonic crystal dielectric column arrays of the same size, a parallel plate waveguide, an absorbing material, and a transmitting monopole antenna. The photonic crystal dielectric column arrays are a two-dimensional square lattice structure surrounded by absorbing material on all four sides. The photonic crystal dielectric column arrays and the absorbing material are both located between the parallel plate waveguides. The transmitting monopole antenna is located in the central region between the two photonic crystal dielectric column arrays. When an external magnetic field of the same magnitude and direction is applied to the transmitting monopole antenna and the two photonic crystal dielectric column arrays, the electromagnetic waves generated by the transmitting monopole antenna can form a boundary state that propagates unidirectionally along the central region of the two photonic crystal dielectric column arrays. By adjusting the magnitude of the external magnetic field and the distance between the two photonic crystal dielectric column arrays, the operating frequency and transmission group velocity of the electromagnetic waves in the waveguide can be adjusted.

[0007] Furthermore, the photonic crystal dielectric column is made of ferrite cylindrical material.

[0008] Furthermore, the material of the photonic crystal dielectric column is yttrium iron garnet with a saturation magnetization intensity of 1884 Oe.

[0009] Furthermore, the operating frequency of the slow light waveguide is increased by increasing the magnitude of the external magnetic field.

[0010] Furthermore, by reducing the distance between the two photonic crystal medium column arrays, the group velocity of the electromagnetic wave transmitted in the slow light waveguide is reduced.

[0011] Furthermore, the distance between the two photonic crystal dielectric column arrays is less than or equal to the lattice constants of the two photonic crystal dielectric column arrays.

[0012] Furthermore, the group velocity of electromagnetic wave transmission in the propagation direction is much smaller than the speed of light, and the slow light factor that characterizes the strength of the slow light effect is greater than 100.

[0013] Furthermore, when there is impurity interference within the transmission channel of the waveguide, the waveguide still has the slow light effect.

[0014] Beneficial Effects: The present invention provides a photonic crystal slow-light waveguide with magnetically tunable operating frequency. This microwave transmission line is based on magnetic field modulation, and its transmission characteristics can be altered by adjusting the magnetic field. Its main operating principle is to introduce a magnetic field into the transmission line. By adjusting the magnitude of the external magnetic field and the distance between two photonic crystal dielectric pillar arrays, the operating frequency and transmission group velocity of the electromagnetic waves in the waveguide can be adjusted. Each of the two photonic crystal dielectric pillar arrays supports a chiral boundary state that propagates in opposite directions. As the two photonic crystal dielectric pillar arrays gradually approach each other, strong coupling causes energy to circulate. When the distance is appropriate, the electromagnetic waves are localized in the central region, forming slow light. The photonic crystal band gap studied in this invention is a magnetic band gap, so its band gap frequency range is sensitive to applied magnetic fields. This differs from previous slow-light waveguide systems, which often operate within the traditional topological band gap frequency range. The magnetic frequency tunability of the magnetic band gap lays the foundation for the present invention to achieve a broadband slow-light waveguide. Compared with existing technologies, the present invention achieves adjustable photon transmission speed and frequency by modulating the magneto-optical effect in the photonic crystal through a magnetic field. This magnetically tunable slow light waveguide has advantages such as controllable transmission speed, adjustable operating frequency, low optical loss, and simple fabrication process, and has broad application prospects. For example, it can be used in optical communications, optical storage, quantum computing, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 3D model structure diagram of an embodiment of the present invention.

[0016] Figure 2 Schematic diagram of a two-dimensional embodiment of the present invention.

[0017] Figure 3 1 and 2 are energy band diagrams in the embodiments of the present invention and energy band diagrams measured experimentally.

[0018] Figure 41 and 2 are energy band diagrams when the external magnetic fields are 500 Oe, 600 Oe, and 700 Oe, respectively, in the embodiment of the present invention.

[0019] Figure 5 It is a two-dimensional schematic diagram and electric field distribution diagram when there are defects in the embodiment of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. After reading this invention, modifications to various equivalent forms of the present invention made by those skilled in the art fall within the scope defined by the appended claims.

[0021] The present invention discloses a photonic crystal slow light waveguide with a magnetically adjustable operating frequency. The waveguide comprises an array of photonic crystal dielectric pillars 1, a parallel plate waveguide 2, an absorbing material 3, an open transmitting monopole antenna 4, and a receiving monopole antenna 6. (The receiving monopole antenna is used for experimental detection in this embodiment and can be placed anywhere along the same line; it is not required for actual use.) The array of photonic crystal dielectric pillars is composed of two photonic crystal subarrays with a two-dimensional square lattice structure separated by a spacing d. The absorbing material 3 surrounds the four sides of the photonic crystal array. The ferromagnetic material array and the absorbing material are both located between the parallel plate waveguides 2.

[0022] This slow light waveguide is based on a two-dimensional square lattice ferrite array structure, with the ferrite array arranged at equal intervals along the x- and y-axes. By adjusting the frequency, the electromagnetic waves emitted by the transmitting monopole antenna can form a localized boundary state that propagates unidirectionally along an ideal conductor. Specifically, at a specific frequency, the electromagnetic waves generated by the monopole antenna 4 under the action of an external magnetic field can form a boundary state that propagates unidirectionally along the central region of the two photonic crystal subarrays. The receiving monopole antenna 5 detects the phase of the electric field along the electromagnetic wave transmission path, and the group velocity is determined by the phase difference after phase cancellation and the distance difference between the transmitting monopole antenna and the receiving monopole antenna. Frequency magnetic tunability is achieved by varying the field strength of the external magnetic field.

[0023] In a specific example of the present invention, the photonic crystal dielectric column array is composed of periodically arranged ferrite cylinders (yttrium iron garnet (YIG) with a saturation magnetization of 1884Oe) with a relative dielectric constant of 15.26. The radius of the ferrite cylinder is 2mm, the height is h=10mm, and the lattice constant of the array is 8mm. The quasi-two-dimensional structure composed of a square lattice is placed in a parallel plate waveguide 2 composed of two upper and lower metal aluminum plates with a thickness of D1, where D1 is 1mm to 2mm. The ferrite column lattice is surrounded by an absorbing material with a thickness of D, where D is 10mm to 20mm. The transmitting end monopole antenna 4, which remains in the open state, has a length of 10mm and is fixed in the center area between the two photonic crystal dielectric column arrays. When the external magnetic field strength is 500Oe, it can generate a boundary state with a very slow group velocity that is transmitted unidirectionally along the PEC at a frequency of about 4.04GHz. And when the external magnetic field increases, the frequency will increase, laying the foundation for achieving magnetic adjustability of the operating frequency.

[0024] In the specific example of the present invention, simulation and experiments show that when the receiving end monopole antenna is located at point a and point b with a spacing Δx of 16 mm, the phase of the electromagnetic wave at the corresponding position is detected and the difference is obtained. according to The calculated group velocity of slow light is 2.86557*10 6 m / s, and the corresponding slow light factor is equal to 104.69, thus realizing the function of slow light waveguide.

[0025] Figure 2 The distance between the two photonic crystal medium column arrays is represented by the distance d. By adjusting the size of the distance d, the group velocity of the slow light can be adjusted. In theory, the smaller the distance d, the smaller the group velocity of the electromagnetic wave transmitted in the slow light waveguide.

[0026] Figure 3 Characterize the process of measuring the slow light of the slow light waveguide. In order to accurately measure the group velocity of the electromagnetic wave supported by the slow light waveguide, we select two points on the right side of the transmitting monopole antenna at a distance of 3a and 5a (a represents the lattice constant) to place the receiving monopole antenna to detect the phase of the electromagnetic wave and calculate the phase difference. Using the phase difference, we can finally find that the group velocity of slow light is equal to 2.86557*10 6 m / s, and the corresponding slow-light factor is 104.69, which is competitive compared to the slow-light waveguides currently on the market.

[0027] In order to study the relationship between the operating frequency of the slow light waveguide and the magnitude of the external magnetic field, Figure 4 The distance between the upper and lower photonic crystal subarrays is fixed at d = a (a represents the lattice constant). Figure 4(a) is the energy band diagram when the external magnetic field is equal to 500Oe. Figure 4 (b) is the energy band diagram when the external magnetic field is equal to 600Oe. Figure 4 (c) shows the energy band diagram when the external magnetic field is 700 Oe. When the external magnetic field increases, the frequency increases, laying the foundation for achieving magnetic tunability of the operating frequency.

[0028] In this embodiment, defects are simulated by introducing a dielectric column with a dielectric constant equal to 8 on the path of slow light transmission. Figure 5 A defect is present horizontally to the left of monopole antenna 4, simulated by a dielectric pillar 6 with a dielectric constant of 8. The field diagram shows that the electric field distribution of the slow light waveguide remains unchanged due to the introduction of the defect, demonstrating the slow light waveguide's excellent immunity to defects.

[0029] In summary, the photonic crystal slow light waveguide with magnetically tunable operating frequency disclosed in the embodiment of the present invention has the advantages of being immune to defects, simple structure, large slow light factor, and magnetically tunable operating frequency, which solves the shortcomings of traditional photonic crystal slow light waveguide with magnetically tunable operating frequency, such as being sensitive to defects and having a narrow operating bandwidth.

Claims

1. A photonic crystal slow light waveguide with magnetically tunable operating frequency, characterized in that: The invention comprises two photonic crystal dielectric column arrays of the same size, a parallel plate waveguide, an absorbing material, and a transmitting monopole antenna; the photonic crystal dielectric column array is a two-dimensional square lattice structure surrounded by absorbing material on all four sides; the photonic crystal dielectric column array and the absorbing material are both located between the parallel plate waveguide; the transmitting monopole antenna is located in the central area between the two photonic crystal dielectric column arrays; when an external magnetic field of the same magnitude and direction is applied to the transmitting monopole antenna and the two photonic crystal dielectric column arrays, the electromagnetic waves generated by the transmitting monopole antenna can form a boundary state that is unidirectionally transmitted along the central area of ​​the two photonic crystal dielectric column arrays. By adjusting the magnitude of the external magnetic field and the distance between the two photonic crystal dielectric column arrays, the operating frequency and transmission group velocity of the electromagnetic waves in the waveguide can be adjusted.

2. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: The photonic crystal dielectric column is made of ferrite cylindrical material.

3. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: The material of the photonic crystal dielectric column is yttrium iron garnet with a saturation magnetization intensity of 1884Oe.

4. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: The operating frequency of the slow light waveguide can be increased by increasing the magnitude of the external magnetic field.

5. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: By reducing the distance between two photonic crystal medium column arrays, the group velocity of electromagnetic waves transmitted in the slow light waveguide is reduced.

6. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: The distance between the two photonic crystal dielectric column arrays is less than or equal to the lattice constants of the two photonic crystal dielectric column arrays.

7. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: The group velocity of electromagnetic wave transmission in the propagation direction is much smaller than the speed of light, and the slow light factor that characterizes the strength of the slow light effect is greater than 100.

8. The photonic crystal slow light waveguide with magnetically tunable operating frequency according to claim 1, characterized in that: When there is impurity interference within the waveguide's transmission channel, the waveguide still has the slow light effect.

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