Two-dimensional photonic crystal auto-collimation Fabry-Perot comb filter

Abstract

The utility model provides a two-dimensional photonic crystal auto-collimation Fabry-Perot comb filter which is characterized in that a beam splitter formed by line defects, a partial reflection mirror and a total reflection mirror are arranged in a two-dimensional photonic crystal, and the type and the structure of the photonic crystal enable a light beam to be propagated in the crystal in an auto-collimation manner; the positions of the beam splitter, the partial reflection mirror and the total reflection mirror are set according to the principle of a Fabry-Perot comb filter, the included angle between the beam splitter and the X axis of the photonic crystal is 45 degrees, the beam splitter and the first total reflection mirror form a first reflection arm, and the beam splitter and the partial reflection mirror form a second reflection arm. And the second total reflection mirror is arranged behind the partial reflection mirror. The utility model has the advantages that the light beam is self-guided in the photonic crystal without a guided wave structure, the beam splitting mechanism is simple, the problem of waveguide coupling in a photonic crystal waveguide interferometer is avoided, the beam splitting ratio of the beam splitter is easy to control, the structural size is small, and the like.

Description

Technical Field

[0001] The utility model belongs to the technical fields of optoelectronics, optical communications and the like, and is specifically a two-dimensional photonic crystal self-collimating Fabry-Perot type comb filter. Background Art

[0002] The self-collimation effect is one of the peculiar dispersion phenomena in photonic crystals. The self-collimation effect enables narrow light beams in perfect photonic crystals to propagate in a collimated manner without a "physical" guiding boundary and without crosstalk.

[0003] The self-collimation effect has been studied in depth theoretically and has been confirmed experimentally. It comes from the unique dispersion properties of photonic crystals, that is, there are very flat isofrequency surfaces in the isofrequency diagram within a specific frequency range and a large angle range.

[0004] Since the propagation of light wave energy is always perpendicular to the equifrequency plane, the light waves in this frequency range will only propagate in the direction perpendicular to the equifrequency plane in the photonic crystal. In order to be able to be applied in practice, the existing technology provides a simple and effective self-collimating beam bending and splitting mechanism. By changing the hole (column) radius of the photonic crystal, controlling the change of the lattice constant, or realizing the function of total reflection through the photonic crystal-air interface structure, the self-collimating beam is totally reflected. For the splitting mechanism, the energy splitting ratio can be adjusted by changing the lattice constant of the photonic crystal or changing the radius of the air hole or dielectric column on the line defect. In addition to the self-collimating beam splitter, these reflection and splitting mechanisms can be easily used to design other optical devices.

[0005] The existing photonic crystal Fabry-Perot comb filter uses the photonic crystal line defect as a waveguide to guide the propagation of the light beam, and does not use the self-collimation effect to guide the propagation of the light beam.

[0006] Currently, the optical devices based on the self-collimation effect of two-dimensional photonic crystals include Michelson interferometer, Mach-Zehnder interferometer, notch filter, etc. Utility Model Content

[0007] Considering the application prospects of integrated photonic devices based on photonic crystal waveguide type Mach-Zehnder interferometer, light intensity detector, and optical switch, it has received great attention. Currently, the existing optical devices based on the self-collimation effect of two-dimensional photonic crystals include Michelson interferometer, Mach-Zehnder interferometer, notch filter, etc.

[0008] It is considered that the existing photonic crystal Fabry-Perot comb filter uses the photonic crystal line defect as a waveguide to guide the propagation of the light beam, and does not use the self-collimation effect to guide the propagation of the light beam.

[0009] Therefore, in order to further simplify and reduce the structure of the device and fill the gap in the existing design, the utility model proposes a two-dimensional photonic crystal self-collimating Fabry-Perot type comb filter.

[0010] The specific technical solution adopted by the utility model to solve its technical problems is:

[0011] A two-dimensional photonic crystal self-collimating Fabry-Perot comb filter, characterized in that: a beam splitter composed of linear defects, a partial reflector and a total reflector are arranged in the two-dimensional photonic crystal, and the type and structure of the photonic crystal enable the light beam to propagate in the crystal in a self-collimating manner; the positions of the beam splitter, the partial reflector and the total reflector are arranged according to the principle of the Fabry-Perot comb filter: including a beam splitter arranged at an angle of 45 degrees with the X-axis of the photonic crystal, the beam splitter and the first total reflector form a first reflective arm, and the beam splitter and the partial reflector form a second reflective arm, and the second total reflector is arranged behind the partial reflector.

[0012] Furthermore, the two-dimensional photonic crystal adopts a hole-shaped or columnar lattice structure and is arranged in an oblique tetragonal pattern. The radius of the dielectric hole or dielectric column is 0.33a, where a is the lattice constant; the axis of the dielectric hole or dielectric column is along the z-axis direction, the diagonal of the square lattice is along the x-axis direction, and the other perpendicular diagonal is along the y-axis direction.

[0013] Furthermore, the line defect corresponding to the beam splitter is: a row of air holes or dielectric columns whose radius or refractive index is different from that of the photonic crystal body.

[0014] Furthermore, the line defect corresponding to the partial reflector is: two rows or columns of line defects with lattice constants different from those of the photonic crystal body arranged in a direction with an angle of 90 degrees with the X-axis of the photonic crystal, so as to realize the function of partial reflection.

[0015] Furthermore, the linear defect corresponding to the total reflection mirror is: two or more rows of air holes or dielectric columns with lattice constants different from the photonic crystal body arranged in a direction with an angle of 90 degrees or 0 degrees with the X-axis of the photonic crystal to fully reflect the incident light.

[0016] Furthermore, the dielectric constant of the two-dimensional photonic crystal is 12, and the refractive index n=3.46, corresponding to a self-collimation frequency range of 0.168c / a to 0.188c / a, where c is the speed of light in a vacuum.

[0017] Furthermore, the beam splitter is a linear defect introduced in the direction (10), with a radius r∈[0.435a, 0.507a], and the collimated beam is split into two beams I when passing through the beam splitter. T and I R , I T Propagate along the original direction, I RPropagates in the vertical direction; the lattice constant of the total reflection mirror corresponding to the line defect is 2a.

[0018] Furthermore, the ratio of the reflectivity Rs and the transmittance Ts of the beam splitter is 1:1, and the length is Width Square air hole arrangement structure.

[0019] Furthermore, the difference between the two arm lengths of the Fabry-Perot comb filter satisfies l1-l2=0.5d, wherein l1 and l2 are the arm lengths of the first reflection arm and the second reflection arm respectively, and d is the distance between the partial reflection mirror and the second total reflection mirror.

[0020] Furthermore, the arm length of the first reflective arm is The length of the second reflector arm is The width of the beam entrance is

[0021] Compared with the prior art, the utility model and its preferred solution realize self-guiding of light beams in photonic crystals without the need for waveguide structures, and the beam splitting mechanism is simple, and the waveguide coupling problem existing in photonic crystal waveguide interferometers is avoided. In addition, the beam splitting ratio of the beam splitter is easy to control, and the structure is small in size. Its application prospects have the advantages of simple structure, easy implementation, low price, small device size, etc., and it has market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0023] Figure 1 A schematic diagram of the photonic crystal structure used in the embodiment of the utility model;

[0024] Figure 2 The first energy band isofrequency diagram of the TE mode in the wave vector space corresponding to the photonic crystal used in the embodiment of the utility model; wherein the bold line range is the self-collimation mode, and the lower right illustration is: the hole-shaped photonic crystal structure;

[0025] Figure 3 This is a schematic diagram of the structure of a hole-shaped photonic crystal beam splitter according to an embodiment of the utility model;

[0026] Figure 4 This is a relationship diagram between the reflectivity Rs, transmittance Ts and the corresponding radius of the beam splitter in the embodiment of the utility model;

[0027] Figure 5 This is a structural diagram of a TE photonic crystal partial reflector according to an embodiment of the utility model;

[0028] Figure 6 The relationship between the reflectivity R, transmittance T and radius of the first energy band partial reflector of the TE mode in the embodiment of the utility model;

[0029] Figure 7 This is a transient electric field distribution diagram of the total reflection mirror of the utility model embodiment when working;

[0030] Figure 8 This is a structural diagram of a two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to an embodiment of the utility model, wherein the line portion represents the self-collimating waveguide route;

[0031] Fig. 9 This is the transmission spectrum of the I1 port of the first energy band Fabry-Perot comb filter of the two-dimensional air hole photonic crystal TE polarization mode in the embodiment of the utility model;

[0032] Fig.10 The figures are respectively transient electric field distribution diagrams of the stop band and pass band when the preferred filter of the embodiment of the utility model is working. DETAILED DESCRIPTION

[0033] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail as follows:

[0034] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] like Figure 1-Figure 10 As shown, the basic design of the two-dimensional photonic crystal self-collimating Fabry-Perot type comb filter provided by the embodiment of the utility model is:

[0037] A beam splitter, a partial reflector and a total reflector formed by linear defects are arranged in a two-dimensional photonic crystal, and the type and structure of the photonic crystal enable the light beam to propagate in a self-collimating manner in the crystal.

[0038] Among them, as shown in the introduction of the background technology part of the present invention, the self-collimation effect is a special dispersion phenomenon in photonic crystals, which is common knowledge. However, the current existing technology has not utilized it to improve the photonic crystal Fabry-Perot comb filter. The utility model utilizes this known property to provide a new filter structure.

[0039] As for how to specifically utilize the self-collimation effect to further explore and optimize the performance of the filter, it is a further preferred solution. Because it involves a method, it does not belong to the protection object of the structural design of the present utility model. The following content of this embodiment will introduce it so that those skilled in the art can better understand the further value of this structural solution, but the method part involved is not the protection object of the present utility model, which is hereby explained.

[0040] On this basis, the positions of the beam splitter, partial reflector and total reflector are set according to the principle of Fabry-Perot comb filter: including a beam splitter set at an angle of 45 degrees to the X-axis of the photonic crystal, the beam splitter and the first total reflector form a first reflective arm, and the beam splitter and the partial reflector form a second reflective arm, and the second total reflector is set behind the partial reflector.

[0041] The above basic design is further:

[0042] Introducing line defects as a beam splitter means: changing a row of air holes or dielectric columns, wherein the arrangement direction of the air holes or dielectric columns is a direction with an angle of 45 degrees with the X-axis, wherein the method of introducing line defects is a prior art known in the art, and this embodiment is provided as a reference for those skilled in the art, and the means of introducing line defects may be by changing the radius of the air holes or dielectric columns or by adding air channels, etc.

[0043] Changing the air holes or dielectric columns refers to changing the radius or refractive index of a row of air holes or dielectric columns to make them different from the main air holes or dielectric columns.

[0044] Introducing line defects as partial reflectors means that the construction method of the partial reflector is to achieve the function of partial reflection by adding two rows (columns) of line defects in a direction with an angle of 90 degrees to the X-axis or changing the lattice constants of these two rows (columns).

[0045] Introducing a line defect as a total reflector means changing the spacing between two or more rows of air holes or dielectric columns at an angle of 90 degrees or 0 degrees to the X-axis.

[0046] The sum of the splitting ratios of the beam splitters is 1.

[0047] Through the above design, the embodiment of the utility model obtains a photonic crystal self-collimating Fabry-Perot type comb filter, which includes a photonic crystal, a beam splitter, a partial reflector and a total reflector.

[0048] Among them, the beam splitter, partial reflector and total reflector are all linear defects in the photonic crystal and the light beam propagates in the crystal in a self-collimated manner.

[0049] The following is a further expansion and introduction of the specific solution of the utility model through a specific design example of a two-dimensional photonic crystal self-collimating Fabry-Perot type comb filter:

[0050] Select the material, determine the material refractive index, and choose the perfect two-dimensional photonic crystal, which is a type of hole-shaped lattice structure arranged in an oblique tetragonal pattern. The hole-shaped photonic crystal is formed by inserting a series of air holes in the photonic crystal. The dielectric constant is determined to be 12 (refractive index n = 3.46) and the medium hole radius is 0.33a, where a is the lattice constant. The photonic crystal structure is as follows Figure 1 As shown, the axis of the air hole is along the z-axis, the diagonal line of the square lattice (11 direction) is along the x-axis, and the other perpendicular diagonal line is along the y-axis. Of course, the photonic crystal can also be composed of dielectric columns, so the following air holes can also be dielectric columns.

[0051] As a preferred strategy, the plane wave expansion method can be used to calculate the isofrequency diagram of the structure to obtain an electromagnetic wave mode with self-collimation phenomenon: the plane wave expansion method is used to calculate the isofrequency diagram (first band) of the TE (electric field polarization) mode of the structure, such as Figure 2 As shown, the bold line on the equal frequency surface represents the frequency of 0.168c / a to 0.188c / a, which represents the electromagnetic wave mode with self-collimation effect. This equal frequency segment is a flat line segment within a large opening angle, and the energy flow direction of all the medium magnetic wave modes on this equal frequency segment is perpendicular to the equal frequency line when propagating in the photonic crystal. These modes corresponding to the frequencies in the range of 0.168c / a to 0.188c / a will propagate forward along this direction (direction 11). According to this characteristic, the light beam within this frequency range does not require a tunnel-type constraint mechanism in the photonic crystal and propagates forward in a self-collimated manner. The bold line in the figure represents the self-collimation frequency range of 0.168c / a to 0.188c / a of the structure, where c is the speed of light in a vacuum. Based on the above considerations, this embodiment sets the wavelength corresponding to the center frequency of the incident Gaussian light beam of 0.180c / a to 1.55μm.

[0052] Line defects are introduced into the photonic crystal as beam splitters, partial reflectors and total reflectors to form photonic crystal Fabry-Perot comb filters. Figure 1 , Figure 3 As shown: In the direction (10) (the angle with the x-axis is 45), a line defect is introduced, that is, the beam splitter is formed by enlarging the radius of the air holes of 25 perfect photonic crystals along the Γ-M direction (the number of air holes here is not necessarily 25, as long as it is slightly wider than the beam in the 45-degree direction) to form a radius r∈[0.435a, 0.507a]. When the self-collimated beam passes through the line defect, it is divided into two beams I T and I R , I T Propagate along the original direction, I RPropagate in the vertical direction. The line defect is a beam splitter. The reflectivity and transmittance of the beam splitter are numerically measured using the finite time-domain difference (FDTD) method. Different splitting ratios can be obtained by changing the radius of the air hole. In the direction with an angle of 90 degrees to the X-axis, the function of a partial reflector is realized by adding two rows (columns) of line defects or changing the lattice constants of these two rows (columns). In the direction with an angle of 90 degrees or 0 degrees to the X-axis, the position of the photon bandgap can be adjusted by changing the spacing of the lattice constants of two or more rows of air holes or dielectric columns. Here, the lattice constant is changed from a to 2a to realize the function of a total reflector.

[0053] The photonic crystal self-collimating filter is formed by placing a beam splitter, a partial reflector and a total reflector according to the arrangement of a Fabry-Perot type comb filter. In this specific embodiment, a beam splitter is selected, and its reflectivity Rs and transmittance Ts ratio is 1:1, such as Figure 8 As shown, the length is Width The square air hole arrangement structure has a perfect matching layer at the absorption boundary of 2.8a. In the figure, BS represents a beam splitter, which is composed of a row of 25 perfect photonic crystal air holes with enlarged radius in the (10) direction. M1 and M2 represent total reflectors, which have air hole lattice constants in the (11) direction changed from a to 2a, and their size is slightly wider than the beam. The distances from the total reflector and the partial reflector to the center of the beam splitter are not equal, and the difference in the length of the two arms must satisfy l1-l2=0.5d. In this embodiment, the length of the upward arm is The arm length to the right is here A Gaussian beam is injected into the left input port I0, and its width is The incident light beam enters the filter.

[0054] It can be seen that the structure of the photonic crystal self-collimating Fabry-Perot comb filter obtained by the above method includes a photonic crystal beam splitter, a partial reflector and a total reflector, and the beam splitter, partial reflector and total reflector are all linear defects arranged in the photonic crystal.

[0055] Furthermore, this embodiment uses the finite time-domain difference method to numerically analyze the working principle of the filter and provides its mathematical model to enable those skilled in the art to better understand the solution of this embodiment. Figure 8 As shown. A Gaussian beam is injected into the left input port I0, and its width is The light propagates through the beam splitter and is divided into two parts, one going upward and the other going right, with a ratio of 1:1. The light is transmitted through different transmission paths. The upward light beam is completely reflected back by the total reflection mirror and then passes through the beam splitter and is divided into two light beams going downward and left. The right light beam passes through the Fabry-Perot cavity and then returns to the beam splitter and is divided into two light beams going downward and left. The left and downward light beams interfere and superimpose to output. Since the output light beam at the left port overlaps with the incident light beam, only the transmission at the downward port is considered here. The asymmetric Fabry-Perot cavity can produce multi-beam interference and can adjust the phase difference produced by the two interference arms, so that this filter has the functions required for practical applications. Based on the principle of beam interference, the transmittance of the I1 port of the Fabry-Perot comb filter under lossless conditions is

[0056]

[0057] Where k = 2π / λ is the wave number, λ = c / f is the vacuum wavelength, f is the frequency, Δl = l1-l2 is the path length difference between the two arms (l1, l2), r is the reflectivity of the partial reflector M3, and θ = knd is the phase shift produced by the asymmetric Fabry-Perot cavity. Therefore, the parameter Δl = l1-l2 = 0.5d is set.

[0058] Among the structural parameters of the Fabry-Perot comb filter, the difference between the two arm lengths determines its periodic characteristics. The output filter shape of the Fabry-Perot comb filter is affected by the cavity length of the asymmetric Fabry-Perot cavity and one of the reflectors with a lower reflectivity. Adjusting the GT parameters can obtain a structure with excellent performance.

[0059] This result shows that under the condition of Δl = l1-l2 = 0.5d, the filter will have a flat passband and a wide stopband. For the filter of the utility model, since the splitting ratio of the beam splitter is easy to control, other parameters can also be used to design the filter. It can also be seen here that equation (1) is a mathematical model that describes the working principle of the traditional Fabry-Perot comb filter, and is also applicable to the filter of the utility model.

[0060] According to the parameters set above, the incident light source is a monochromatic Gaussian light source with a wavelength of 1.55 μm and a width of

[0061] The transmission curve spectrum of port I1 is obtained by calculating and analyzing the finite difference time domain algorithm, such as Fig. 9 shown. Figure 8 The thick red solid line in the middle depicts the propagation trajectory of the self-collimated beam of the designed Fabry-Perot comb filter. Fig. 9It means that there are nearly two cycles of transmission spectrum in the normalized self-collimation frequency range. Further analysis shows that the passband of the normalized frequency of the Fabry-Perot comb filter is 0.1731c / a~0.1766c / a, 0.1807c / a~0.1844c / a; the stopband is 0.1766c / a~0.1807c / a, 0.1844c / a~0.1879c / a. Assuming that the self-collimation frequency 0.180c / a corresponds to the central communication wavelength of 1550nm, it can be calculated that the passband wavelength range is 1580nm~1612nm, 1544nm~1512nm; the stopband wavelength range is 1580nm~1544nm, 1512nm~1476nm, covering the entire communication c-band.

[0062] Some typical frequency points are also selected to calculate the electromagnetic field distribution of its passband and stopband. Fig.10 It can be observed in each figure that when the frequency is 0.1753c / a and 0.1821c / a, the light beam can be well transmitted through the I1 port, while when the frequency is 0.1711c / a and 0.1885c / a, the light beam produces a destructive interference effect, so no transmitted light is generated at the I1 port. The designed two-dimensional columnar photonic crystal Fabry-Perot comb filter has the advantages of small size and easy realization, and is expected to be practically applied in optical communication integration.

[0063] The present invention is not limited to the above-mentioned specific embodiments. Any improvements that are obvious to those skilled in the art fall within the scope of the present invention. For example, the air hole can be a dielectric column. The air hole used as a beam splitter only needs to be different from other air holes. The difference can be that the air hole radius or refractive index is different from other air holes.

[0064] The above is only the preferred embodiment of the utility model, and does not limit the utility model in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the utility model without departing from the technical solution of the utility model still belongs to the protection scope of the technical solution of the utility model.

[0065] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of two-dimensional photonic crystal self-collimating Fabry-Perot comb filters under the inspiration of this patent. All equivalent changes and modifications made within the scope of the patent application of this utility model should be covered by this patent.

Claims

1. A two-dimensional photonic crystal self-collimating Fabry-Perot comb filter, characterized in that: A beam splitter, a partial reflector and a total reflector formed by line defects are arranged in a two-dimensional photonic crystal, and the type and structure of the photonic crystal enable the light beam to propagate in a self-collimated manner in the crystal; the positions of the beam splitter, the partial reflector and the total reflector are arranged according to the principle of a Fabry-Perot comb filter: including a beam splitter arranged at an angle of 45 degrees to the X-axis of the photonic crystal, the beam splitter and the first total reflector form a first reflective arm, and the beam splitter and the partial reflector form a second reflective arm, and the second total reflector is arranged behind the partial reflector.

2. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 1, characterized in that: The two-dimensional photonic crystal adopts a hole-shaped or columnar lattice structure and is arranged in an oblique tetragonal pattern. The radius of the medium hole or medium column is 0.33 a , a is the lattice constant; the axis of the dielectric hole or dielectric column is along the z-axis, the diagonal of the square lattice is along the x-axis, and the other perpendicular diagonal is along the y-axis.

3. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 1, characterized in that: The line defect corresponding to the beam splitter is: a row of air holes or dielectric columns whose radius or refractive index is different from that of the photonic crystal body.

4. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 1, characterized in that: The line defect corresponding to the partial reflector is: two rows or columns of line defects with lattice constants different from those of the photonic crystal body arranged in a direction with an angle of 90 degrees with the X-axis of the photonic crystal, so as to realize the function of partial reflection.

5. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 1, characterized in that: The line defect corresponding to the total reflection mirror is: two or more rows of air holes or dielectric columns with lattice constants different from the photonic crystal body arranged in a direction with an angle of 90 degrees or 0 degrees with the X-axis of the photonic crystal, so as to fully reflect the incident light.

6. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 2, characterized in that: The dielectric constant of the two-dimensional photonic crystal is 12, the refractive index n=3.46, and the corresponding self-collimation frequency range is 0.168 c / a ~0.188 c / a , c is the speed of light in a vacuum.

7. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 6, characterized in that: The beam splitter is a linear defect introduced in the (10) direction, with a radius r∈[0.435 a , 0.507 a ], the collimated beam is divided into two beams I when passing through the beam splitter T and I R , I T Propagate along the original direction, I R Propagates in the vertical direction; the lattice constant of the total reflection mirror corresponding to the line defect is 2 a .

8. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 7, characterized in that: The beam splitter has a reflectivity Rs and a transmittance Ts ratio of 1:1 and a length of 84 a , width is 64 a Square air hole arrangement structure.

9. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to any one of claims 1 to 8, characterized in that: The difference between the lengths of the two arms of the Fabry-Perot comb filter satisfies l 1- l 2=0.5 d ,in l 1 and l 2 are the arm lengths of the first reflection arm and the second reflection arm respectively, d is the distance between the partial reflector and the second total reflector.

10. The two-dimensional photonic crystal self-collimating Fabry-Perot comb filter according to claim 9, characterized in that: The length of the first reflector arm is l 1=29.5 a , the length of the second reflector arm is l 2=14 a , d =31 a , the width of the beam entrance is 6 a .

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