Fast light waveguide device based on photonic crystal material heterostructure

Abstract

The application discloses a fast light waveguide device based on a photonic crystal material heterostructure, which comprises a core layer and a cladding layer arranged symmetrically on the upper and lower sides of the core layer; the core layer comprises a plurality of regularly arranged first photonic crystals; the cladding layer comprises a plurality of regularly arranged second photonic crystals; the first photonic crystal comprises a silicon substrate and a ring-shaped air column; the second photonic crystal comprises a silicon substrate and a circular air column; the first photonic crystal and the second photonic crystal are both left-handed materials and have negative refractive indexes when the incident wave frequency is within the range of 1.9322E14 Hz to 1.9328E14 Hz. The application utilizes the abnormal dispersion characteristics of the three-layer flat waveguide based on the left-handed material, and the waveguide propagation constant beta and the frequency f present a negative correlation relationship, and the function of generating fast light is realized within the frequency range of 1.9322E14 Hz to 1.9328E14 Hz. Since the waveguide width is in the nanometer level, the problems of waveguide miniaturization, high transmission bandwidth and low transmission loss in integrated optics are solved, and an excellent solution for future integrated optics is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated optics, in particular to a fast light waveguide device based on photonic crystal material heterostructure. BACKGROUND

[0002] Today's society is developing rapidly towards informationization, and information communication technology and application are quite extensive. Various electronic products appear in all aspects of our life, and the rapidly growing information is flooding in our life, which makes us put forward new requirements for the processing speed and storage capacity of information. At the same time, the integration method of higher efficiency, higher speed and miniaturization is constantly updated, and the chip size is constantly reduced. Since the establishment of semiconductor physics in the last century, electrons have become the main information carrier in integrated chips, but due to the existence of Coulomb effect between electrons, the improvement of integrated circuit performance will inevitably be contradictory to the reduction of its integration. At this time, the performance advantage of photon is highlighted, which can greatly improve the information transmission speed while reducing the loss and constantly improving the integration. The proposal of photonic crystal makes the advantage of photon more obvious. In recent years, with the rapid development of new micro-nano photonic devices, people's requirements for the performance and size of the devices are also higher and higher; controlling photons, designing and producing optical devices become possible, providing solutions for future all-optical communication, photonic computers, etc.

[0003] Photonic crystal is a new kind of artificial microstructure material, which has physical properties that natural materials do not have. The unique band gap and fast light effect provide the possibility for designing optical communication devices with higher integration and better performance. The physical property of negative refractive index can be used to prepare left-handed materials, and this property can be adjusted by frequency, which is widely used in optical waveguide, antenna system and electromagnetic cloaking device, etc. Photonic crystal fundamentally solves the problem of controlling light in micro-nano size optical devices, provides a new way to realize super-dense integrated devices, and makes photonic crystal waveguide, filter, modulator, beam splitter, etc. based on photonic crystal have wide application prospect.

[0004] As the most basic channel in integrated optics, the integration of waveguide has always been the core problem limiting the development of integrated optics. How to design micro-nano level integrated waveguide while ensuring certain transmission bandwidth and low transmission loss has always been the bottleneck of the development of integrated optics. Three-layer slab waveguide is composed of three layers of uniform medium, the medium layer in the middle is called core layer, and the medium layers on both sides of the core layer are called cladding layers. The dielectric constant of the core layer is larger than that of the cladding layers on both sides, so that the light beam can be concentrated in the core layer for transmission, thereby playing the role of waveguide. The waveguide structure with the core layer sandwiched between the two cladding layers has unique optical transmission characteristics. The traditional fast light waveguide has high transmission loss, low transmission bandwidth and cannot be integrated, and the process of obtaining fast light is also relatively complex, often requiring relatively complex manufacturing procedures. Even in integrated optics, there are problems of miniaturization, high transmission bandwidth and low transmission loss in waveguide. SUMMARY

[0005] The present application aims to overcome the deficiencies in the prior art, and provides a fast light waveguide device based on photonic crystal material heterostructure.

[0006] To achieve the above object, the technical scheme of the present application is as follows:

[0007] A fast light waveguide device based on photonic crystal material heterostructure, comprising a core layer and a cladding layer arranged symmetrically above and below the core layer, the core layer comprising a plurality of regularly arranged first photonic crystals, the cladding layer comprising a plurality of regularly arranged second photonic crystals, the first photonic crystal comprising a silicon substrate and a ring-shaped air column arranged on the silicon substrate, the second photonic crystal comprising a silicon substrate and a circular air column arranged on the silicon substrate, the first photonic crystal and the second photonic crystal both being left-handed materials and both having a negative refractive index when the incident wave frequency is in the range of 1.9322E14 Hz-1.9328E14 Hz.

[0008] As a preferred embodiment, the fast light waveguide device is a three-layer flat plate structure, and the core layer and the cladding layer are both hexagonal crystal structures and are tightly connected according to the lattice structure to form a heterostructure.

[0009] As a preferred embodiment, the first photonic crystal is arranged in a first periodicity to form the core layer with a first thickness, the second photonic crystal is arranged in a second periodicity to form the cladding layer with a second thickness, and the number of the first periodicity and the second periodicity is determined according to the scattering boundary condition.

[0010] As a preferred embodiment, the number of the first periodicity is 4, and the number of the second periodicity is 3.

[0011] As a preferred embodiment, the first photonic crystal and the second photonic crystal are both two-dimensional core-shell structures.

[0012] As a preferred embodiment, the lattice constant of the first photonic crystal is a=1.096 um, the inner circle radius of the ring-shaped air column is r1=0.14959 um, and the outer circle radius of the ring-shaped air column is r2=0.48485 um.

[0013] As a preferred embodiment, the lattice constant of the second photonic crystal is a=1.096 um, and the radius of the circular air column is r=0.4429 um.

[0014] As a preferred embodiment, the energy band of the first photonic crystal and the energy band of the second photonic crystal both have an accidental three-fold degenerate point at the Γ point.

[0015] As preferred, when the incident wave frequency of the fast light waveguide device is in the range of 1.9322E14 Hz-1.9328E14 Hz, fast light can be generated in the fast light waveguide device.

[0016] As preferred, when the incident wave is a modulated Gaussian pulse, and the carrier frequency information is 1.93224E14 Hz and 1.93230E14 Hz, the reverse propagation occurs in the fast light waveguide device.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] (1) The fast light waveguide device based on the photonic crystal material heterostructure of the present application utilizes the abnormal dispersion characteristics of the three-layer flat waveguide based on the left-handed material, which is characterized by the negative correlation between the waveguide propagation constant β and the frequency f, and realizes the function of generating fast light in the frequency range of 1.9322E14 Hz to 1.9328E14 Hz.

[0019] (2) The fast light waveguide device based on the photonic crystal material heterostructure of the present application can be constructed by silicon-based photonic crystal materials, has a heterostructure, and has the advantages of simplicity, easy processing, miniaturization, etc., and has a novel fast light waveguide structure.

[0020] (3) Compared with the conventional waveguide structure, the fast light waveguide device of the present application has the simplest structure, low transmission loss and high integration. By designing the core-shell photonic crystal material to construct the three-layer flat waveguide of the heterostructure, fast light can be generated in the frequency range of 1.9322E14 Hz to 1.9328E14 Hz. Since the waveguide width is in the nanometer level, the problems of waveguide miniaturization, high transmission bandwidth and low transmission loss in integrated optics are solved, providing an excellent solution for future integrated optics. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments and, together with the description, serve to explain the principles of the present application. Other embodiments and many of the intended advantages of the present application will be readily appreciated as the same becomes better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

[0022] Figure 1 is a structural schematic diagram of the fast light waveguide device based on the photonic crystal material heterostructure of the embodiments of the present application;

[0023] Figure 2Fig. 1 is a schematic diagram of the first photonic crystal primitive cell and the second photonic crystal primitive cell structure, the energy band and the electric field distribution of the fast light waveguide device based on the photonic crystal material heterostructure according to an embodiment of the present application;

[0024] Figure 3 Fig. 2 is a schematic diagram of the effective parameters of the first photonic crystal and the second photonic crystal of the fast light waveguide device based on the photonic crystal material heterostructure according to an embodiment of the present application; the lines with solid circle and solid square marks in Fig. (a) represent the relationship between the effective permeability and the frequency of the first photonic crystal and the second photonic crystal respectively, the lines with hollow circle and hollow square marks in Fig. (a) represent the relationship between the effective permittivity and the frequency of the first photonic crystal and the second photonic crystal respectively; the dashed line and the solid line in Fig. (b) represent the linear relationship between the effective refractive index and the frequency of the first photonic crystal and the second photonic crystal respectively; the shaded part in Fig. (b) is the working frequency range of the fast light waveguide;

[0025] Figure 4 Fig. 3 is a schematic diagram of the electric field distribution of the fast light waveguide device based on the photonic crystal material heterostructure according to an embodiment of the present application when the incident wave frequency is 1.9324E14 Hz;

[0026] Figure 5 Fig. 4 is a schematic diagram of the propagation constant and the normalized frequency of the fast light waveguide device based on the photonic crystal material heterostructure according to an embodiment of the present application; wherein Fig. (a) shows that the propagation constant β of the fast light waveguide presents a negative correlation with the frequency f, i.e. an abnormal dispersion relationship; Fig. (b) shows the negative group velocity calculated within the working frequency range of the fast light waveguide device;

[0027] Figure 6 Fig. 5 is a schematic diagram of the reverse propagation of the modulated Gaussian pulse in the fast light waveguide device according to an embodiment of the present application; wherein Fig. (a) is the envelope of the constructed modulated Gaussian pulse wave packet, the carrier of which can carry specific frequency information. The pulse is incident from the incident port, propagates in the waveguide for a period of time, and the pulse information is collected at the exit port. Fig. (b) is the relationship between the normalized electric field intensity and the time at the exit port, which also represents the relationship between the pulse waveform and the time collected at the exit port. The carrier frequency of the curve with hollow circle mark is 1.93224E14 Hz; the carrier frequency of the curve with solid circle mark is 1.93230E14 Hz. DETAILED DESCRIPTION

[0028] The present application will be further described below in conjunction with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related application, but not to limit the application. In addition, it should be noted that only the parts related to the application are shown in the drawings for the convenience of description.

[0029] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] refer to Figure 1 In an embodiment of the present invention, a fast optical waveguide device based on a heterostructure of photonic crystal materials is proposed, comprising a core layer 1 and a cladding layer 2 with a symmetrical structure arranged on the upper and lower sides of the core layer 1, the core layer 1 comprising a plurality of regularly arranged first photonic crystals 11, the cladding layer 2 comprising a plurality of regularly arranged second photonic crystals 21, the first photonic crystal 11 comprising a silicon substrate and an annular air column arranged on the silicon substrate, the second photonic crystal 21 comprising a silicon substrate and a circular air column arranged on the silicon substrate. When the frequency of the incident wave is in the range of 1.9322E14Hz-1.9328E14Hz, the first photonic crystal 11 and the second photonic crystal 21 are both left-handed materials and both have a negative refractive index and the same lattice constant. The fast optical waveguide device based on a heterostructure of photonic crystal materials in an embodiment of the present application is a three-layer flat plate structure, the core layer 1 and the cladding layer 2 both have a hexagonal crystal structure and are closely connected in strict accordance with the structure of the lattice to form a heterostructure. The first photonic crystals 11 are arranged in a first periodicity to form a core layer 1 of a first thickness, and the second photonic crystals 21 are arranged in a second periodicity to form a cladding layer 2 of a second thickness. The number of the first periodicity and the second periodicity are set according to the scattering boundary condition.

[0031] like Figure 2 The schematic diagram of the structure, energy band and electric field distribution of the first photonic crystal 11 unit cell and the second photonic crystal 21 unit cell shown in the embodiment of the present application is that the first photonic crystal 11 in the fast light waveguide device based on the heterostructure of photonic crystal material includes a ring-shaped air column and a silicon substrate, and the lattice constant is a=1.096um, the inner circle radius is r1=0.14959um, and the outer circle radius is r2=0.48485um. The second photonic crystal 21 in the fast light waveguide device based on the heterostructure of photonic crystal material in the embodiment of the present application includes a circular air column and a silicon substrate, and the lattice constant is a=1.096um, and the circle radius is r=0.4429um. The first photonic crystal and the second photonic crystal are both two-dimensional core-shell structures. As shown in FIG. Figure 3The effective parameter diagram of the first photonic crystal 11 and the second photonic crystal 21 is shown, the lines with solid circle and solid square marks in figure (a) represent the relationship between the effective permeability and frequency of the first photonic crystal 11 and the second photonic crystal 21 respectively, the lines with hollow circle and hollow square marks in figure (a) represent the relationship between the effective permittivity and frequency of the first photonic crystal 11 and the second photonic crystal 21 respectively; the dashed line and the solid line in figure (b) represent the linear relationship between the effective refractive index and frequency of the first photonic crystal 11 and the second photonic crystal 21 respectively, the shaded part in figure (b) is the working frequency range of the fast light waveguide device, in this working frequency range, the effective refractive index of the first photonic crystal 11 and the second photonic crystal 21 is negative, and the permittivity and permeability are negative at the same time, so the first photonic crystal 11 and the second photonic crystal 21 are left-handed materials.

[0032] As shown in Figure 4 The electric field distribution diagram of the fast light waveguide device based on the photonic crystal material heterostructure when the incident wave frequency is 1.9324E14 Hz is shown, which includes the core layer 1 composed of the periodically arranged first photonic crystal 11 and the cladding layer 2 composed of the periodically arranged second photonic crystal 21. In the embodiment of the present application, the number of the first periodic arrangement of the first photonic crystal 11 in the core layer 1 is M=4, and the number of the second periodic arrangement of the second photonic crystal 21 in the cladding layer 2 is N=3. In the embodiment of the present application, the waveguide is a heterostructure, the transverse length of the waveguide is 40*a microns, and the incident wave frequency is 1.9324E14 Hz.

[0033] The fast light waveguide device based on the photonic crystal material heterostructure of the embodiment of the present application is composed of the core layer 1 composed of 4 periodically arranged first photonic crystals 11 and the cladding layer 1 composed of 3 periodically arranged second photonic crystals 21. The calculation method of the effective permittivity and effective permeability of the photonic crystal is as follows:

[0034]

[0035]

[0036] In the formula, ε eff represents the effective permittivity of the photonic crystal; μ eff represents the effective permeability of the photonic crystal; k y represents the y component of the wave vector; ω represents the angular frequency; ε0 represents the vacuum permittivity; μ0 represents the vacuum permeability; E x represents the average value of the eigen electric field along the x axis direction; H z represents the average value of the eigen magnetic field along the z axis direction.

[0037] The dispersion equation of the TM mode propagating in the fast light waveguide device is where b is a normalized propagation constant, V is a normalized frequency, ε core and ε clad are the dielectric constants of the core layer and the cladding layer, ω is an angular frequency, m is a mode order, and m = 0. The relationship between the propagation constant β and the angular frequency ω is obtained from the above formula, and the negative group velocity can be obtained through the group velocity formula

[0038] When the incident wave frequency is 1.9324E14 Hz, the absolute value of the refractive index of the first photonic crystal 11 is greater than that of the second photonic crystal 21, so that the refractive index of the core layer of the three-layer flat waveguide is greater than that of the cladding layer, and the electromagnetic wave is well confined in the waveguide for transmission, thereby realizing the function of generating fast light. The existence of fast light is verified by modulating the reverse propagation of the Gaussian pulse in the waveguide.

[0039] The technical effects of the present application are further described below in combination with simulation experiments.

[0040] 1. Simulation conditions and contents:

[0041] The simulation frequency interval is set to 1.9322E14 Hz to 1.9328E14 Hz, and the above specific embodiments are simulated using the commercial simulation software COMSOL Multiphysics 5.5:

[0042] Simulation 1: The band and electric field of the first and second photonic crystal units in the embodiments of the present application are simulated by constructing the first and second photonic crystal unit cells, respectively, as shown in Figure 2

[0043] Simulation 2: The incident wave is set to a plane electromagnetic wave, and when the incident wave frequency is 1.9324E14 Hz, the electric field distribution of the fast light waveguide device based on the photonic crystal material heterostructure in the embodiments of the present application at the incident wave frequency of 1.9324E14 Hz is simulated, as shown in Figure 4

[0044] Simulation 3: The incident wave is set to a modulated Gaussian pulse, and when the carrier frequency information is 1.93224E14 Hz and 1.93230E14 Hz, the time-domain propagation simulation is performed, as shown in Figure 6 .

[0045] 2. Analysis of simulation measurement results:

[0046] Reference Figure 2 ​​​, shows that when the first photonic crystal 11 primitive cell is composed of a ring-shaped air column and a silicon substrate, the lattice constant is a = 1.096 um, the inner circle radius is r1 = 0.14959 um, and the outer circle radius is r2 = 0.48485 um, the energy band presented at the Γ point has an accidental three-fold degenerate point, i.e. the Dirac-like point p1. Similarly, the second photonic crystal 21 primitive cell is composed of a circular air column and a silicon substrate, the lattice constant is a = 1.096 um, and the circle radius is r = 0.4429 um, the energy band presented at the Γ point has an accidental three-fold degenerate point, i.e. the Dirac-like point p2.

[0047] Reference Figure 4 , shows the electric field distribution of the fast light waveguide device based on the photonic crystal material heterostructure at a working frequency of 1.9324E14 Hz. The simulation results show that in a wide frequency range of 1.9322E14 Hz to 1.9328E14 Hz, the fast light waveguide device based on the photonic crystal material heterostructure can better confine the light in the core layer for propagation, meeting the requirements of low loss and miniaturization of the waveguide.

[0048] Reference Figure 6 , shows that the modulated Gaussian pulses carrying different frequency information are respectively incident from the incident port, propagate in the waveguide for a period of time, and collect the pulse information after emission. When the carrier frequency information of the incident pulse is 1.93230E14 Hz, its pulse waveform appears before the incident pulse with a carrier frequency information of 1.93224E14 Hz (the front and back relationship of the positions of the two pulse wave peaks), which proves that the phenomenon of reverse propagation occurs in the fast light waveguide device based on the photonic crystal material heterostructure, which meets the properties of fast light. The simulation results show that the fast light waveguide device based on the photonic crystal material heterostructure can produce fast light in the frequency range of 1.9322E14 Hz to 1.9328E14 Hz.

[0049] The above describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

[0050] In the description of the application, it needs to be understood that the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. The word 'comprising' does not exclude the existence of elements or steps not listed in the claims. The word 'a' or 'an' in front of an element does not exclude the existence of multiple such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that the combination of these measures cannot be used to improve. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. A fast optical waveguide device based on a heterostructure of photonic crystal materials, characterized in that: The invention comprises a core layer and a symmetrical cladding layer arranged on the upper and lower sides of the core layer, wherein the core layer comprises a plurality of regularly arranged first photonic crystals, the cladding layer comprises a plurality of regularly arranged second photonic crystals, the first photonic crystal comprises a silicon substrate and an annular air column arranged on the silicon substrate, the second photonic crystal comprises a silicon substrate and a circular air column arranged on the silicon substrate, and when the incident wave frequency is 1.9322E14 Hz -1.9328E14 Hz Within the range, the first photonic crystal and the second photonic crystal are both left-handed materials and have a negative refractive index, the fast optical waveguide device is a three-layer flat plate structure, the core layer and the cladding are both hexagonal crystal structures and are closely connected in strict accordance with the structure of the lattice to form a heterostructure, the first photonic crystals are arranged in a first periodicity to form the core layer of a first thickness, and the second photonic crystals are arranged in a second periodicity to form the cladding of a second thickness, and the number of the first periodicity and the second periodicity are set according to the scattering boundary condition.

2. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 1, characterized in that: The number of the first periodic arrangements is 4, and the number of the second periodic arrangements is 3.

3. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 1, characterized in that: The first photonic crystal and the second photonic crystal are both two-dimensional core-shell structures.

4. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 1, characterized in that: The lattice constant of the first photonic crystal is a =1.096 um , the inner radius of the annular air column r 1 =0.14959 um , outer radius r 2 =0.48485 um .

5. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 1, characterized in that: The lattice constant of the second photonic crystal is a =1.096 um , the radius of the circular air column r =0.4429 um .

6. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 1, characterized in that: The energy bands of the first photonic crystal and the second photonic crystal both have an accidental triple degenerate point at the Γ point.

7. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 6, characterized in that: When the incident wave frequency of the fast optical waveguide device is 1.9322E14 Hz -1.9328E14 Hz Fast light is generated within the range.

8. The fast optical waveguide device based on the photonic crystal material heterostructure according to claim 1, characterized in that: When the incident wave is a modulated Gaussian pulse and the carrier frequency information is 1.93224E14 Hz and 1.93230E14 Hz , reverse propagation occurs in the fast optical waveguide device.

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