Photonic crystal filter and method of manufacturing the same, and spectral detection system and method

Abstract

A photonic crystal filter and its fabrication method, spectral detection system, and method are disclosed. The photonic crystal filter includes a photonic crystal section comprising multiple photonic crystal units. Each photonic crystal unit includes multiple through-holes arranged in an array. Each photonic crystal unit includes a central region and a peripheral region. The multiple through-holes include first through-holes in the central region and second through-holes in the peripheral region. The central region includes Na×Na first through-holes, where Na is a positive integer greater than or equal to 5. The number of second through-holes on each side of the peripheral region is Na×Nb, where Nb is a positive integer greater than or equal to 1. The minimum distance between two adjacent first through-holes is a first spacing Da, the minimum distance between two adjacent second through-holes is a second spacing Db, and the minimum distance between the first and second through-holes is a third spacing Dg, satisfying Na*Da+Nb*Db+Dg≤10μm. The spectral detection system has advantages such as high detection accuracy, small structural volume, and structural stability.

Description

Technical Field

[0001] The embodiments of this disclosure relate to a photonic crystal filter, a method for preparing the photonic crystal filter, a spectral detection system, and a spectral detection method. Background Technology

[0002] Spectroscopy is a crucial method for characterizing the spectral features of light, thus finding applications in agriculture, medicine, and communications. Miniature spectrometers, with their unique portability and on-site diagnostic capabilities, have emerged as a promising field, achieving significant advancements through the use of dispersive or narrowband optics and Fourier transform devices. In principle, photons can be spectrally distinguished by sufficiently different optical paths or lifetimes. However, due to the limited size restricting the ability to extend optical paths, and the difficulty of covering the entire desired spectrum with narrowband resonances, achieving optimal size, resolution, and range in miniature spectrometers requires complex trade-offs.

[0003] However, highly spectrally selective components, such as high quality factor (Q) optical resonators, are essential and highly advantageous for achieving high resolution. By arranging high-Q resonators in arrays, the detection range can be expanded while maintaining a compact size using state-of-the-art nanofabrication techniques. Therefore, various miniaturized resonators, such as nanowires, quantum dots, microring resonators, and plasmon surfaces, are used for parallel spectral detection. However, most resonant structures capable of generating high Q values ​​require symmetry, necessitating electron beam lithography (EBL) for fine-structure fabrication. When the resonant unit exceeds the EBL writing field size, mechanical errors and beam drift often occur, leading to performance degradation. Therefore, miniaturization of the device size is crucial. However, to achieve high resolution and a wide detection range, the resonator array must be large-scale, posing significant challenges to the connection, scanning, and calibration of components. Therefore, ultra-high Q microcavities capable of out-of-plane excitation may be a promising candidate, as they can avoid the planar coupling and time-scanning requirements of microring resonator arrays. Therefore, while improving spectral detection performance, designing a high-Q microcavity array that can generate a sufficient number of high-Q characteristic responses while keeping the unit volume as small as possible has become a challenging problem. Summary of the Invention

[0004] At least one embodiment of this disclosure provides a photonic crystal filter, a method for fabricating the photonic crystal filter, a spectral detection system, and a spectral detection method. The photonic crystal filter, through precise design of the photonic crystal portion, possesses narrowband filtering capability, thereby achieving efficient filtering of light at specific wavelengths. Furthermore, the filtering capability and the wavelength of the filterable light can be adjusted according to the precise design. When applied to a spectral detection system, this photonic crystal filter enables spectral detection and improves its accuracy. Moreover, the spectral detection system and method provided by the embodiments of this disclosure achieve advantages such as process robustness, high precision, adjustable precision, and smaller size through simple arraying, thus facilitating the further miniaturization of spectral detection systems.

[0005] At least one embodiment of this disclosure provides a photonic crystal filter, which includes: a photonic crystal section, wherein the photonic crystal section includes a plurality of photonic crystal units arranged in an array, each photonic crystal unit includes a plurality of through holes arranged in an array, each photonic crystal unit includes a central region and a peripheral region surrounding the central region, the plurality of through holes includes first through holes arranged in an array in the central region and second through holes arranged in an array in the peripheral region; the central region includes Na×Na first through holes, wherein Na is a positive integer greater than or equal to 5; the number of second through holes on each side of the peripheral region is Na×Nb, wherein Nb is a positive integer greater than or equal to 1; the minimum distance between two adjacent first through holes is a first spacing Da, the minimum distance between two adjacent second through holes is a second spacing Db, and the minimum distance between the first through hole and the second through hole is a third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm.

[0006] For example, in the photonic crystal filter provided in at least one embodiment of this disclosure, the minimum distance between two adjacent photonic crystal units is a fourth spacing Nag, and the fourth spacing Nag is greater than or equal to 5 micrometers and less than or equal to 10 micrometers.

[0007] For example, in the photonic crystal filter provided in at least one embodiment of this disclosure, a transition region is further included between the central region and the peripheral region. The vias also include third vias arranged in an array in the transition region. The minimum distance between any two adjacent third vias is a fifth spacing. The arrangement density of the first vias is greater than the arrangement density of the third vias, and the arrangement density of the third vias is greater than the arrangement density of the second vias. The first spacing is less than the fifth spacing, and the fifth spacing is less than the second spacing. Alternatively, the arrangement density of the first vias is less than the arrangement density of the third vias, and the arrangement density of the third vias is less than the arrangement density of the second vias. The first spacing is greater than the fifth spacing, and the fifth spacing is greater than the second spacing.

[0008] For example, in the photonic crystal filter provided in at least one embodiment of this disclosure, the first through-hole, the second through-hole, and the third through-hole have the same planar shape, the planar dimension of the first through-hole is smaller than the planar dimension of the second through-hole, and the planar dimension of the second through-hole is smaller than the planar dimension of the third through-hole.

[0009] For example, in the photonic crystal filter provided in at least one embodiment of this disclosure, the first through holes are arranged in a matrix, the overall outer contour shape of the matrix arrangement of the first through holes is a quadrilateral, the second through holes are disposed on the side of each side of the quadrilateral away from the center of the central region, and the second through holes surround the entire matrix arrangement of the first through holes.

[0010] For example, in the photonic crystal filter provided in at least one embodiment of this disclosure, the rectangular array formed by the first through-hole is a square array, and the planar shape of the central region is a square; the peripheral region includes four side regions and four corner regions, and the shapes of the four side regions and the four corner regions are all rectangular; the long side of each of the four side regions that is close to the central region is aligned with the four sides of the central region and has the same length; the four corner regions are located in the direction away from the center of the square at the four corners of the central region, and the two adjacent sides of each of the four corner regions are aligned with the short sides of the two adjacent side regions and have the same length.

[0011] For example, in the photonic crystal filter provided in at least one embodiment of this disclosure, the four side regions are all rectangular regions formed by Na×Nb second through holes, and the four corner regions are all square regions formed by Nb×Nb second through holes, where Na and Nb are both positive integers.

[0012] For example, at least one embodiment of the photonic crystal filter provided in this disclosure further includes an active layer and a first dielectric layer disposed between the active layer and the photonic crystal portion, wherein the active layer is configured to emit light and serve as an optical gain medium.

[0013] For example, at least one embodiment of the photonic crystal filter provided in this disclosure further includes a second dielectric layer disposed on the side of the photonic crystal portion away from the first dielectric layer, wherein each of the vias includes opposing first and second ends along the extension direction of its channel, the first end being connected to the first dielectric layer and the second end being connected to the second dielectric layer.

[0014] For example, at least one embodiment of the photonic crystal filter provided in this disclosure further includes: an n-type substrate; an n-type semiconductor heavily doped layer and an n-type semiconductor doped layer sequentially disposed on the n-type substrate; a p-type semiconductor doped layer and a p-type semiconductor heavily doped layer sequentially disposed on the side of the active layer away from the n-type substrate; a p-type electrode layer disposed on the side of the p-type semiconductor heavily doped layer away from the n-type substrate; and an n-type electrode layer disposed on the side of the n-type semiconductor heavily doped layer away from the n-type substrate and spaced apart from the n-type semiconductor doped layer; wherein the active layer is disposed on the side of the n-type semiconductor doped layer away from the n-type substrate; the p-type semiconductor heavily doped layer is configured as the second dielectric layer; and the p-type semiconductor doped layer is configured as the photonic crystal portion and the first dielectric layer.

[0015] For example, at least one embodiment of the photonic crystal filter provided in this disclosure further includes: an n-type substrate; an n-type semiconductor heavily doped layer and an n-type semiconductor doped layer sequentially disposed on the n-type substrate; a p-type semiconductor doped layer and a p-type semiconductor heavily doped layer sequentially disposed on the side of the active layer away from the n-type substrate; a p-type electrode layer disposed on the side of the p-type semiconductor heavily doped layer away from the n-type substrate; and an n-type electrode layer disposed on the side of the n-type semiconductor heavily doped layer away from the n-type substrate and spaced apart from the n-type semiconductor doped layer; wherein the active layer is disposed on the side of the n-type semiconductor doped layer away from the n-type substrate; the n-type semiconductor heavily doped layer is configured as the second dielectric layer; and the n-type semiconductor doped layer is configured as the photonic crystal portion and the first dielectric layer.

[0016] At least one embodiment of this disclosure also provides a method for fabricating a photonic crystal filter. The method includes: providing a substrate; forming a first type of semiconductor doped layer thin film on the substrate; applying a photoresist to the first type of semiconductor doped layer thin film and pre-curing it to form a photoresist layer; performing nanoimprinting on the photoresist layer using an imprinting template to transfer the pattern of the imprinting template to the photoresist layer, and curing it to form a photoresist layer pattern; using the photoresist layer pattern as a mask to perform a patterning process on the first type of semiconductor doped layer thin film to form a photonic crystal layer, and removing the photoresist layer pattern; wherein the photonic crystal layer includes a photonic crystal portion, and the photonic crystal portion includes a plurality of photonic crystal units arranged in an array, each photonic crystal unit... The photonic crystal unit includes a plurality of vias arranged in an array. Each photonic crystal unit includes a central region and a peripheral region surrounding the central region. The plurality of vias includes a first via arranged in the central region and a second via arranged in the peripheral region. The central region includes Na×Na first vias, where Na is a positive integer greater than or equal to 5. The number of second vias on each side of the peripheral region is Na×Nb, where Nb is a positive integer greater than or equal to 1. The minimum distance between two adjacent first vias is a first spacing Da, the minimum distance between two adjacent second vias is a second spacing Db, and the minimum distance between a first via and a second via is a third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm.

[0017] For example, at least one embodiment of the present disclosure provides a preparation method that further includes: forming an active layer thin film on the substrate; forming a first dielectric layer thin film between the active layer thin film and the photonic crystal layer; wherein the active layer thin film is configured to emit light and serve as an optical gain medium.

[0018] For example, the preparation method provided in at least one embodiment of this disclosure further includes forming a second dielectric layer film on the side of the photonic crystal layer away from the first dielectric layer film, wherein the material of the second dielectric layer film is a heavily doped material of a first type of semiconductor, and each of the vias includes opposing first ends and second ends along the extension direction of its channel, the first end being connected to the first dielectric layer film, and the second end being connected to the second dielectric layer film.

[0019] At least one embodiment of this disclosure also provides a spectral detection system, which includes: a semi-transparent mirror, an objective lens, an imaging structure, a 4f optical system, and a photonic crystal filter as described in any of the above embodiments.

[0020] At least one embodiment of this disclosure also provides a spectral detection method, which includes: forming a spectrum to be measured with different characteristics; and inputting the spectrum to be measured into the spectral detection system described in any of the preceding claims to distinguish the spectrum to be measured with different characteristics. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0022] Figure 1 A block diagram of a photonic crystal filter provided in at least one embodiment of the present disclosure;

[0023] Figure 2 This is a schematic diagram of a planar structure of a photonic crystal section provided in at least one embodiment of the present disclosure;

[0024] Figure 3 for Figure 2 A partially magnified structural diagram of the central region of the photonic crystal section;

[0025] Figure 4 A schematic diagram of a planar structure of another photonic crystal section provided in at least one embodiment of the present disclosure;

[0026] Figure 5 for Figure 4 An enlarged structural diagram of region B, defined by the dashed line in the diagram;

[0027] Figure 6 A schematic diagram of a planar structure of a photonic crystal section provided in at least one embodiment of the present disclosure;

[0028] Figure 7 for Figure 6 A magnified structural diagram of the region C defined by the dashed line;

[0029] Figure 8 A schematic diagram of a planar structure of a photonic crystal section provided in at least one embodiment of the present disclosure;

[0030] Figure 9 for Figure 8 A magnified structural diagram of the region D defined by the dashed line;

[0031] Figure 10 A schematic diagram of a planar structure of a photonic crystal section provided in at least one embodiment of the present disclosure;

[0032] Figure 11 A schematic diagram showing a planar structure of multiple photonic crystal arrays and an enlarged structure of a single photonic crystal, provided in at least one embodiment of this disclosure;

[0033] Figure 12 A schematic cross-sectional view of a photonic crystal filter provided in at least one embodiment of this disclosure;

[0034] Figure 13 A schematic cross-sectional view of another photonic crystal filter provided in at least one embodiment of this disclosure;

[0035] Figure 14 A flowchart illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of this disclosure;

[0036] Figures 15A-15E A process diagram illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of this disclosure;

[0037] Figure 16 A flowchart illustrating a method for fabricating another photonic crystal filter according to at least one embodiment of this disclosure;

[0038] Figures 17A-17H A process diagram illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of this disclosure;

[0039] Figure 18 A flowchart illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of this disclosure;

[0040] Figure 19A-19I A process diagram illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of this disclosure;

[0041] Figure 20 A block diagram of a spectral detection system provided in at least one embodiment of this disclosure;

[0042] Figure 21 The pattern of a photonic crystal microcavity array, as measured by a spectral testing system with a photonic crystal filter, is provided in at least one embodiment of this disclosure.

[0043] Figure 22 Loss curves for the training process of a demodulated spectral neural network provided in at least one embodiment of this disclosure;

[0044] Figure 23 Demodulation spectral performance characterization diagrams provided for at least one embodiment of this disclosure; and

[0045] Figure 24 Simulation performance diagram of the spectral detection system provided in at least one embodiment of this disclosure to avoid the write field splicing problem. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0047] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0048] Photonic crystal filters possess advantages such as high power, high reliability, long lifespan, small size, high quality factor, small divergence angle, narrow spectral linewidth, suitability for multi-wavelength single-mode operation, and low cost, and are used in various fields. For example, the inventors of this disclosure have noted that in the field of spectral detection, the photonic crystal unit included in a typical spectral detection system has regular shape units. The size of the photonic crystal unit can be smaller than the sub-write field size of commonly used electron beam exposure. Each regular shape unit has multiple frequency selection capabilities at different wavelengths. The frequency selection capability can be adjusted according to the required spectral recovery accuracy, and the wavelengths corresponding to the characteristic frequencies of adjacent units are uncorrelated, thereby effectively avoiding coupling between adjacent units due to similar wavelengths.

[0049] The inventors of this disclosure also noted that, based on the structure of a photonic crystal filter, a spectral detection system, and a spectral detection method, the pattern of the structure to be detected can be detected through an optical path based on a 4f optical system. Furthermore, rich patterns can be generated in a very small array unit volume, which represents the high Q resonance peaks of different characteristic wavelengths generated by the structure to be detected, thereby realizing the detection of the spectrum to be detected.

[0050] For example, Figure 1 A block diagram of a photonic crystal filter provided in at least one embodiment of this disclosure is shown below. Figure 1The photonic crystal filter 10 includes a photonic crystal section 100. The photonic crystal section 100 operates as follows: A bandgap structure is generated within the photonic crystal section 100 due to the periodic change in the refractive index of light. This bandgap structure controls the movement of light within the photonic crystal section; that is, low refractive index materials periodically appear at certain locations within the high refractive index material. The alternating arrangement of high and low refractive index materials to form a periodic structure generates a photonic crystal bandgap (similar to a band gap in semiconductors). Since the distance between the periodically arranged low refractive index sites is the same, the photonic crystal section with a certain distance only produces a bandgap effect for light waves of a certain frequency. In other words, only light of a certain frequency will be completely blocked from propagating within a photonic crystal with a certain periodic distance.

[0051] For example, Figure 2 This is a schematic diagram of a planar structure of a photonic crystal section provided in at least one embodiment of the present disclosure, as shown below. Figure 2 As shown, the photonic crystal section 100 includes a plurality of photonic crystal units arranged in an array, each photonic crystal unit including a plurality of through-holes 101 arranged in an array. Figure 2 In this example, we will use a circular planar shape for each through hole 101 as an example. Figure 2 In this embodiment, the diameter of each circle is equal, meaning that the planar dimensions of each through-hole 101 are equal. Of course, the embodiments of this disclosure are not limited to this. The planar shape of each through-hole 101 can also be elliptical, triangular, regular hexagonal, irregular shape, or a combination of multiple shapes. The embodiments of this disclosure do not limit this, as long as the through-holes 101 are arranged in an array and are easy to form using nanoimprinting.

[0052] It should be noted that when the planar shape of the through-hole 101 is circular, the imprinting template used in the nanoimprinting process can imprint a circular pattern; when the planar shape of the through-hole 101 is triangular, the imprinting template used in the nanoimprinting process can imprint a triangular pattern; when the planar shape of the through-hole 101 is elliptical, the imprinting template used in the nanoimprinting process can imprint an elliptical pattern; and when the planar shape of the through-hole 101 is regular hexagonal, the imprinting template used in the nanoimprinting process can imprint a regular hexagonal pattern. That is, depending on the planar shape of the formed through-hole 101, the shape of the pattern that the selected nanoimprinting template can imprint is different. For example, in the same photonic crystal section, some through-holes 101 and other through-holes 101 can also have different planar shapes or different planar dimensions. In the embodiments of this disclosure, it is only necessary to select a suitable nanoimprinting template according to the pattern of the through-hole to be formed. Moreover, there are many types of nanoimprinting templates, which can easily meet different pattern requirements. Nanoimprint stencils are less expensive, and the photonic crystal sections with through-holes of different planar shapes or sizes can be formed in a single imprint process, with other process conditions remaining unchanged. However, the commonly used electron beam lithography process requires a longer exposure time, which reduces work efficiency and increases production costs.

[0053] For example, Figure 2 The following explanation uses the example where each through-hole 101 is cylindrical in shape, with a circular planar shape and the same diameter. In one example, the dimensions of each through-hole 101 are equal or approximately equal along their respective extension directions. The following explanation primarily uses the example where the planar shape of the through-hole 101 is circular.

[0054] For example, in other examples, the through hole 101 can also be elliptical cylindrical, meaning that the planar shape of each through hole 101 is elliptical, and the major axis and minor axis of each ellipse are equal; the through hole 101 can also be triangular prism, meaning that the planar shape of each through hole 101 is triangular, and the three sides of any two triangles are respectively equal. Of course, in other embodiments, the through hole 101 can also have other shapes, and the embodiments disclosed herein are not limited in this regard.

[0055] For example, such as Figure 2 As shown, each photonic crystal unit includes a central region 102 and a peripheral region 103 surrounding the central region 102. For example, Figure 2The following description uses a rectangular planar shape for both the central region 102 and the peripheral region 103 as an example. The through-hole 101 in the peripheral region 103 only surrounds the four sides of the through-hole 101 located in the central region 102, and does not surround the corner regions. Of course, the embodiments disclosed herein are not limited in this respect. The central region 102 may also be surrounded at the corner regions. Alternatively, the overall shape of the peripheral region 103 may not be multiple rectangles, but may be an annular, square ring, elliptical, etc., as long as it can suppress the leakage of energy from the central region 102 of the photonic crystal to the peripheral region 103 or control the radiation of energy from the central region 102 of the photonic crystal to the peripheral region 103.

[0056] For example, the peripheral region 103 is used to regulate and suppress energy leakage from the central region 102 or to control the energy of the central region 102 to radiate to the peripheral region 103, so as to achieve the frequency selection capability of the photonic crystal unit.

[0057] For example, such as Figure 2 As shown, the plurality of through holes 101 include first through holes 101a arranged in an array in the central region 102 and second through holes 101b arranged in an array in the peripheral region 103. The relative arrangement density of the first through holes 101a and the relative arrangement density of the second through holes 101b are different. Figure 2 In the process, the relative arrangement density of the first through hole 101a is greater than that of the second through hole 101b.

[0058] For example, Figure 3 for Figure 2 An enlarged structural diagram of the region A defined by the dashed line in the diagram, as shown below. Figure 3 As shown, the first through-hole 101a is formed using nanoimprint lithography. The first through-holes 101a are arranged in a matrix, meaning they are arranged along the X-axis and Y-axis directions respectively. The plane defined by the X and Y axes is the plane containing the top surface of the first through-hole 101a. The direction perpendicular to the plane defined by the X and Y axes is the thickness direction of the photonic crystal filter, which is also the extension direction of the through-hole 101. The dashed-lined region A includes the first through-hole 101a and the second through-hole 101b, as shown... Figure 3 As shown, the minimum distance between any two adjacent first through holes 101a is the first spacing Da. It should be noted that the minimum distance between any two adjacent first through holes 101a refers to the smallest of the different dimensions along different directions that exists between them. Figure 3In the first direction X, the distance between two adjacent first through holes 101a is less than the distance between two adjacent first through holes 101a in the second direction Y. That is, the minimum distance between two adjacent first through holes 101a in the first direction X is Da.

[0059] For example, in Figure 3 In this context, the minimum distance between any two adjacent second through holes 101b is the second spacing Db. Similarly, the minimum distance between any two adjacent second through holes 101b refers to the smallest of the different dimensions along different directions that exists between any two adjacent second through holes 101b. Figure 3 In the second direction Y, the distance between two adjacent second through holes 101b is less than the distance between two adjacent second through holes 101b in the first direction X. That is, the minimum distance between two adjacent second through holes 101b in the second direction Y is Db. Figure 3 In the process, the relative arrangement density of the first through hole 101a is greater than that of the second through hole 101b, and the first spacing Da is less than the second spacing Db.

[0060] For example, in Figure 3 In the middle, the first through hole 101a and the one closest to the right in the left dashed box. Figure 3 In the right dashed box, the second through holes 101b in the column near the left are respectively arranged adjacently. The minimum distance between any adjacent first through holes 101a and second through holes 101b is the third spacing Dg. The third spacing Dg is greater than the first spacing Da and less than the second spacing Db. That is, along the direction from the outer region 103 to the central region 102, the minimum distance between adjacent first through holes 101a, the minimum distance between adjacent first through holes 101a and second through holes 101b, and the minimum distance between adjacent second through holes 101b gradually decrease.

[0061] It should be noted that, in Figure 3 In other variations, the spacing between adjacent first through holes 101a and the spacing between adjacent second through holes 101b can be gradually reduced along the direction from the outer region 103 to the center region 102 in the first direction X. This results in the distance between adjacent through holes 101 (including first through holes 101a and second through holes 101b) gradually decreasing along the direction from the outer region 103 to the center region 102 in the first direction X.

[0062] Specifically, in combination Figure 2 and Figure 3The central region 102 includes Na×Na first through holes 101a, where Na is a positive integer greater than or equal to 5; the number of second through holes 101b on each side of the outer region 103 is Na*Nb, where Nb is a positive integer greater than or equal to 1; the minimum distance between two adjacent first through holes 101a is the first spacing Da, the minimum distance between two adjacent second through holes 101b is the second spacing Db, and the minimum distance between the first and second through holes is the third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm, where, in the outer regions on the left and right sides, Nb is the number of columns of the second through holes 101b in the outer region 103; in the outer regions on the top and bottom sides, Nb is the number of rows of the second through holes 101b in the outer region 103. In the embodiments of this disclosure, the Na, Nb, first spacing Da, second spacing Db, and third spacing Dg in the central region of the photonic crystal prepared by nanoimprinting are fluctuating. Under the conditions defined by the above data, it is possible to prepare photonic crystals by nanoimprinting while ensuring high robustness and quality factor (Q value), thereby reducing production costs and improving production efficiency. It is suitable for large-scale production and can improve the accuracy and efficiency of spectral detection when applied to a spectral detection system.

[0063] For example, due to the intricate structure of the photonic crystal filter provided in the embodiments of this disclosure, even when Na, Da, Nb, Db, and Dg satisfy the aforementioned relationships, it is still necessary to finely design the structural parameters to achieve the desired optical properties. Specific geometric parameters (such as lattice constant and aperture) determine the position and width of the photonic bandgap, and these parameters can also be finely adjusted to satisfy certain relationships to form the desired resonant characteristics.

[0064] For example, by optimizing the aforementioned structural parameters, high-quality factor (Q-value) and narrow-linewidth resonant modes can be obtained. This is crucial for achieving efficient optical field confinement and low-loss transmission, improving the coherence of photonic crystal filters, reducing threshold power, and enhancing the overall performance of photonic crystal filters. Simultaneously, the precise design of photonic crystal filters ensures that the subsequently formed spectral detection system exhibits stable operating characteristics near the target wavelength, making the spectral detection system more reliable in practical applications.

[0065] The embodiments disclosed herein require meticulous design of multiple parameters, thus increasing the complexity of the design process. It necessitates considering and precisely controlling the interrelationships between multiple variables to ensure that the photonic bandgap and resonant wavelength fall within the target range. Typically, the structural design of through-holes in photonic crystal filters requires nanometer-level fabrication precision and involves multiple simulations and experimental iterations to verify the design's rationality. Furthermore, due to limitations in fabrication equipment and process conditions, error accumulation may occur in actual production, affecting the design accuracy of the photonic crystal filter. Therefore, the design of photonic crystal filters must not only meet theoretical requirements but also consider the feasibility of the fabrication process, further increasing the design difficulty and challenges.

[0066] For example, in one example, the number of photonic crystal units arranged in the array is 400, the first spacing Da ranges from 522nm to 540nm, the second spacing Db ranges from 552nm to 570nm, the third spacing Dg ranges from 532nm to 550nm, Na is 7, and Nb is 6.

[0067] For example, Figure 4 This is a schematic diagram of the planar structure of another photonic crystal section provided in at least one embodiment of the present disclosure, as shown below. Figure 4 As shown, the photonic crystal section 100 includes a central region 102 and a peripheral region 103 surrounding the central region 102. For example, Figure 4 This explanation also uses the example of rectangular planar shapes for both the central region 102 and the outer region 103. The through-hole 101 in the outer region 103 only surrounds the four sides of the through-hole 101 located in the central region 102, leaving the corner areas unsurrounded. Figure 4 In the process, multiple through holes 101 include a first through hole 101a arranged in an array in the central region 102 and a second through hole 101b arranged in an array in the peripheral region 103. The relative arrangement density of the first through hole 101a is less than the relative arrangement density of the second through hole 101b.

[0068] It should be noted that when the planar shape and planar dimensions of the first through hole 101a and the second through hole 101b are the same, the relative arrangement density of the first through hole 101a refers to the number of first through holes 101a per unit area, and the relative arrangement density of the second through hole 101b refers to the number of second through holes 101b per unit area. When the shapes or sizes of the first through hole 101a and the second through hole 101b are different, an equivalent conversion is performed based on the area of ​​the planes of the first through hole 101a and the second through hole 101b. For example, when the plane area of ​​one first through hole 101a is equivalent to the plane area of ​​two second through holes 101b, the relative arrangement density of the first through hole 101a refers to twice the number of first through holes 101a per unit area, and the relative arrangement density of the second through hole 101b refers to the number of second through holes 101b per unit area. Alternatively, when the plane area of ​​one first through hole 101a is equivalent to 0.5 of the plane area of ​​the second through hole 101b, the relative arrangement density of the first through hole 101a refers to the number of first through holes 101a per unit area, and the relative arrangement density of the second through hole 101b refers to twice the number of second through holes 101b per unit area. When the planar area of ​​one first through hole 101a is equivalent to the planar area of ​​n second through holes 101b, and n is greater than 1, the relative arrangement density of the first through hole 101a is n times the number of first through holes 101a per unit area, and the relative arrangement density of the second through holes 101b is the number of second through holes 101b per unit area; when n is greater than 0 and less than 1, when the planar area of ​​one first through hole 101a is equivalent to the planar area of ​​n second through holes 101b, the relative arrangement density of the first through hole 101a is the number of first through holes 101a per unit area, and the relative arrangement density of the second through holes 101b is 1 / n times the number of second through holes 101b per unit area.

[0069] For example, in one example, although Figure 2 and Figure 4 The relative arrangement densities of the first through hole 101a and the second through hole 101b are different. Figure 2 and Figure 4 The first through-hole 101a and the second through-hole 101b can also be completed in the same nanoimprinting process step without increasing production costs.

[0070] For example, Figure 5 for Figure 4 An enlarged structural diagram of the dashed-line defined region B, which includes a first through hole 101a and a second through hole 101b, as shown in the diagram. Figure 5As shown, the minimum distance between any two adjacent first through holes 101a is the first spacing Da. It should be noted that the minimum distance between any two adjacent first through holes 101a refers to the smallest of the different dimensions along different directions that exists between them. Figure 5 In the first direction X, the distance between two adjacent first through holes 101a is less than the distance between two adjacent first through holes 101a in the second direction Y. That is, the minimum distance between two adjacent first through holes 101a in the first direction X is Da.

[0071] For example, in Figure 5 In this context, the minimum distance between any two adjacent second through holes 101b is the second spacing Db. Similarly, the minimum distance between any two adjacent second through holes 101b refers to the smallest of the different dimensions along different directions that exists between any two adjacent second through holes 101b. Figure 5 In the second direction Y, the distance between two adjacent second through holes 101b is less than the distance between two adjacent second through holes 101b in the first direction X. That is, the minimum distance between two adjacent second through holes 101b in the second direction Y is Db, and in Figure 5 In the process, the relative arrangement density of the first through hole 101a is less than the relative arrangement density of the second through hole 101b, and the first spacing Da is greater than the second spacing Db.

[0072] For example, in Figure 5 In the middle, the second through hole 101b near the right side of the left dashed box and Figure 5 In the right dashed box, the first through holes 101a in the column near the left are respectively arranged adjacently. The minimum distance between any two adjacent first through holes 101a and second through holes 101b is the third spacing Dg, which is greater than the second spacing Db and less than the first spacing Da.

[0073] For example, in Figure 5 In this context, the first spacing Da is the spacing in the first direction X, the second spacing Db is the spacing in the second direction Y, and the third spacing Dg is a direction on the plane formed by the first direction X and the second direction Y that has a certain angle with both the first and second directions. This direction is determined based on the arrangement of adjacent first through holes 101a and second through holes 101b.

[0074] It should be noted that, in Figure 5In other variations, the spacing between adjacent first through holes 101a and adjacent second through holes 101b can gradually increase along the first direction X, from the outer region 103 to the central region 102. Except for the distance between adjacent first through holes 101a and second through holes 101b which is not along the direction from the outer region 103 to the central region 102, the spacing between other adjacent through holes 101 can be the spacing along the first direction X, from the outer region 103 to the central region 102. Figure 5 Without considering the adjacent first through hole 101a and second through hole 101b, the spacing between other adjacent through holes 101 can gradually increase along the direction from the outer region 103 to the central region 102.

[0075] For example, Figure 6 This is a schematic diagram of the planar structure of another photonic crystal section provided in at least one embodiment of the present disclosure, as shown below. Figure 6 As shown, the photonic crystal section 100 includes a central region 102, a peripheral region 103 surrounding the central region 102, and a transition region 104 between the central region 102 and the peripheral region 103. For example, Figure 6 The following description uses a rectangular planar shape for the central region 102, transition region 104, and peripheral region 103 as an example. The through hole 101 in the peripheral region 103 only surrounds the four side regions of the through hole located in the central region 102, and does not surround the corner regions. Of course, the embodiments of this disclosure are not limited in this respect, and the central region may also be surrounded at the corner regions.

[0076] For example, Figure 7 for Figure 6 An enlarged structural diagram of region C defined by the dashed line, combined with... Figure 6 and Figure 7 The through-hole 101 also includes third through-holes 101c arranged in an array in the transition region 104. The minimum distance between any two adjacent third through-holes 101c is the fifth spacing d5, the minimum distance between any two adjacent first through-holes 101a is the first spacing Da, and the minimum distance between any two adjacent second through-holes 101b is the second spacing Db. For example, in Figure 6 and Figure 7 In this configuration, the relative arrangement density of the first through hole 101a is greater than that of the second through hole 101b, the relative arrangement density of the third through hole 101c is greater than that of the second through hole 101b and less than that of the first through hole 101a, the first spacing Da is less than the fifth spacing d5, and the fifth spacing d5 is less than the second spacing Db.

[0077] For example, such as Figure 7As shown, the minimum distance between adjacent third through-holes 101c and first through-holes 101a is the sixth spacing d6, and the minimum distance between adjacent third through-holes 101c and second through-holes 101b is the seventh spacing d7. The sixth spacing d6 is less than the fifth spacing d5 and greater than the first spacing Da, and the seventh spacing d7 is greater than the fifth spacing d5 and less than the second spacing Db. This arrangement allows the outer region and the transition region to fully enclose the central region. The periodicity of the third through-hole 101c in the transition region, the periodicity of the second through-hole 101b in the outer region, and the periodicity of the first through-hole 101a in the central region 102 are all different. This allows the transition region to further block energy leakage or radiation in the two-dimensional photonic crystal microcavity, so as to more fully suppress energy leakage from the outer region or control energy radiation from the two-dimensional photonic crystal microcavity to the outer region. Moreover, this arrangement can also improve robustness.

[0078] For example, setting the distance between the third through holes 101c in the transition region to the above-mentioned size range can meet the application requirements of different scenarios.

[0079] For example, Figure 8 This is a schematic diagram of the planar structure of another photonic crystal section provided in at least one embodiment of the present disclosure, as shown below. Figure 8 As shown, the photonic crystal section 100 includes a central region 102, a peripheral region 103 surrounding the central region 102, and a transition region 104 between the central region 102 and the peripheral region 103. For example, Figure 8 The following description uses a rectangular planar shape for the central region 102, transition region 104, and peripheral region 103 as an example. The through hole 101 in the peripheral region 103 only surrounds the four side regions of the through hole located in the central region 102, and does not surround the corner regions. Of course, the embodiments of this disclosure are not limited in this respect, and the central region may also be surrounded at the corner regions.

[0080] For example, Figure 9 for Figure 8 An enlarged structural diagram of the region D defined by the dashed line, combined with... Figure 8 and Figure 9 As shown, the through-hole 101 also includes third through-holes 101c arranged in an array in the transition region 104. The minimum distance between any two adjacent third through-holes 101c is the fifth spacing d5, the minimum distance between any two adjacent first through-holes 101a is the first spacing Da, and the minimum distance between any two adjacent second through-holes 101b is the second spacing Db. For example, in Figure 8 and Figure 9In this configuration, the relative arrangement density of the first through hole 101a is less than the relative arrangement density of the second through hole 101b, the relative arrangement density of the third through hole 101c is less than the relative arrangement density of the second through hole 101b but greater than the relative arrangement density of the first through hole 101a, the first spacing Da is greater than the fifth spacing d5, and the fifth spacing d5 is greater than the second spacing Db.

[0081] For example, such as Figure 9 As shown, the minimum distance between adjacent third through hole 101c and first through hole 101a is the sixth spacing d6, and the minimum distance between adjacent third through hole 101c and second through hole 101b is the seventh spacing d7. The sixth spacing d6 is greater than the fifth spacing d5 and less than the first spacing Da, and the seventh spacing d7 is less than the fifth spacing d5 and greater than the second spacing Db.

[0082] For example, in Figure 9 In this context, the first spacing Da, the second spacing Db, the fifth spacing d5, and the seventh spacing d7 are all spacings in the first direction X. The sixth spacing d6 is a spacing in a direction that has a certain angle with both the first direction X and the second direction Y on the plane formed by the first direction X and the second direction Y. This direction is determined based on the arrangement of the adjacent third through hole 101c and the first through hole 101a.

[0083] For example, in Figure 6 , Figure 7 , Figure 8 and Figure 9 In the structure shown, the first through hole 101a, the second through hole 101b, and the third through hole 101c have the same planar shape and the same planar size. Figure 6 , Figure 7 , Figure 8 and Figure 9 The above description uses a cylindrical shape and a circular planar shape as an example. For through holes 101 of other shapes or sizes, the above spacings can be set according to the relevant descriptions above, and will not be repeated here.

[0084] For example, Figure 10 This is a schematic diagram of the planar structure of another photonic crystal section provided in at least one embodiment of the present disclosure, as shown below. Figure 10As shown, the first through holes 101a are arranged in a matrix, and the overall outer contour of the matrix arrangement of the first through holes 101a is quadrilateral. The second through holes 101b are respectively disposed on the side of each side of the quadrilateral away from the center of the central region 102, and the second through holes 101b surround the entire matrix arrangement of the first through holes 101a. Thus, the periphery of the matrix formed by the first through holes 101a is surrounded by the second through holes 101b. This can more effectively suppress the leakage of energy from the two-dimensional photonic crystal microcavity from the peripheral region 103 or control the radiation of energy from the two-dimensional photonic crystal microcavity to the peripheral region 103.

[0085] For example, such as Figure 10 As shown, the array formed by the first through hole 101a is a square array, and the planar shape of the central region 102 is a square; the outer region 103 includes four side regions 103a and four corner regions 103b, and the shapes of the four side regions 103a and the four corner regions 103b are all rectangular; the long side of each of the four side regions 103a that is close to the central region 102 is aligned with the four sides of the central region 102 and has the same length; the four corner regions 103b are located in the direction away from the center of the square at the four corners of the central region 102, and the two adjacent sides of each of the four corner regions 103b are aligned with the short sides of the two adjacent side regions 103a and have the same length.

[0086] For example, such as Figure 10 As shown, the four side regions 103a are rectangular regions formed by Na×Nb second through holes 101b, and the four corner regions 103b are rectangular regions formed by Nb×Nb second through holes 101b. Na and Nb are both positive integers, and Na is greater than Nb. For example, in Figure 10 In the figure, Na is 12 and Nb is 4. The central region 102 includes 12*12 first through holes 101a, the side region 103a includes 12*4 second through holes 101b, and the corner region 103b includes 4*4 second through holes 101b. Of course, the embodiments disclosed herein are not limited to this. Na and Nb can also be other values. Na can also be less than Nb, or Na can be equal to Nb.

[0087] It should be noted that the size of the first through-hole 101a in the central region 102, and the values ​​of the first spacing Da and Na between two adjacent first through-holes 101a, can all be changed. The size and number of the second through-holes 103b in the four side regions 103a and the four corner regions 103b, as well as the second spacing Db between adjacent second through-holes 103b, can all be adjusted. By adjusting the above-mentioned features in the side regions 103a and corner regions 103b, it is possible to suppress the leakage of energy from the microcavities included in the photonic crystal filter from the side regions 103a and corner regions 103b, or to control the radiation of energy from the microcavities included in the photonic crystal filter to the side regions 103a and corner regions 103b.

[0088] For example, in one example, by adjusting at least one of the following: the second spacing Db between adjacent second vias 103b in the side region 103a and the corner region 103b, the size of the second via 103b in the peripheral region, and the spacing between the side region 103a, the corner region 103b, and the central region 102, the bandgap of the microcavity included in the photonic crystal filter can be formed, thereby confining energy in the central region 102 and suppressing the leakage of side energy of the microcavity.

[0089] For example, in one example, by individually adjusting the size of the second through-hole 103b in the side region 103a and corner region 103b corresponding to any side direction and / or the distance between adjacent second through-holes 103b, the leakage of energy in the microcavity included in the photonic crystal filter can be controlled, thereby enabling the energy in the microcavity included in the photonic crystal filter to be radiated in any side direction.

[0090] For example, in one example, by individually adjusting the number of second through holes 103b in the side region 103a and corner region 103b corresponding to any direction on the side, such as removing some of the second through holes 103b, the leakage of energy in the microcavity included in the photonic crystal filter in that direction can be controlled, thereby enabling the energy of the microcavity included in the photonic crystal filter to be radiated in any direction on the side.

[0091] For example, the structural design of the photonic crystal section 100 in the embodiments of this disclosure can suppress energy radiation above and below the photonic crystal section 100 and side energy leakage, confining the energy within the microcavity included in the photonic crystal filter to improve the quality factor Q of the photonic crystal filter. Simultaneously, by disrupting some of the energy suppression conditions within the microcavity included in the photonic crystal filter, energy can be controlled to radiate in any direction, thereby achieving energy coupling between the microcavity included in the photonic crystal filter and the optical structure outside the microcavity.

[0092] For example, Figure 11This is a schematic diagram illustrating the planar structure of a plurality of photonic crystal arrays and the enlarged structure of a single photonic crystal unit provided in at least one embodiment of this disclosure, as shown below. Figure 11 As shown, the minimum distance between two adjacent photonic crystal units is the fourth spacing Nag, which is greater than or equal to 5 micrometers and less than or equal to 10 micrometers. Although in Figure 11 The illustration shows 16 photonic crystal units arranged in an array, but the embodiments of this disclosure are not limited to this; there may be more or fewer photonic crystal units arranged in an array. For example, in Figure 11 The enlarged structural schematic diagram of a single photonic crystal section also shows the first spacing Da, the second spacing Db, the third spacing Dg, as well as Na and Nb. Each photonic crystal section satisfies the aforementioned condition Na*Da+Nb*Db+Dg≤10μm. This allows the photonic crystal filter to improve the accuracy of spectral detection when used in a spectral detection system.

[0093] For example, Figure 12 This is a schematic cross-sectional view of a photonic crystal filter provided in at least one embodiment of the present disclosure, as shown below. Figure 12 As shown, the photonic crystal filter 10 further includes an active layer 105 and a first dielectric layer 106 disposed between the active layer 105 and the photonic crystal section 100. For example, the active layer 105 is configured to emit light and serve as an optical gain medium, and the material of the active layer 105 includes a fluorescent material.

[0094] For example, such as Figure 12 As shown, the photonic crystal filter 10 further includes a second dielectric layer 107 disposed on the side of the photonic crystal section 100 away from the first dielectric layer 106. Each through-hole 101 (including a first through-hole 101a and a second through-hole 101b) includes opposing first and second ends along its channel extension direction. The first end is connected to the first dielectric layer 106, and the second end is connected to the second dielectric layer 107. That is, the first dielectric layer 106 and the second dielectric layer 107 close the through-hole 101. The refractive index of the first dielectric layer 106 is n1, and the refractive index of the second dielectric layer 107 is n2. For example, the first dielectric layer 106 and the second dielectric layer 107 have hole transport or electron transport functions.

[0095] For example, such as Figure 12 As shown, the through-hole 101 is filled with a medium of refractive index n0, which can be a gas (e.g., air), solid, or liquid material. In one example, the medium filling the through-hole 101 can also be the same medium as the material of the photonic crystal section 100.

[0096] For example, in one example, the medium filling the via 101 may be at least one of silicon, germanium, germanium-silicon material, silicon compound, germanium compound, metal or group III-V material. The silicon compound includes at least one of silicon nitride, silicon dioxide, and silicon carbide. When the photonic crystal is double-layered or multi-layered, at least one layer is not penetrating.

[0097] The embodiments of this disclosure do not limit the relationship between the refractive index n0 of the medium filling the through hole 101, the refractive index n1 of the first dielectric layer 106, and the refractive index n2 of the second dielectric layer 107. In practical applications, the medium filling the through hole 101, the first dielectric layer 106, and the second dielectric layer 107 can be configured to have the same refractive index or different refractive indices as needed. The embodiments of this disclosure do not limit this.

[0098] For example, combining Figure 12 The refractive index n0 of the medium filling the through hole 101 is equal to 1, the refractive index n1 of the first dielectric layer 106 is equal to 1, the refractive index n2 of the second dielectric layer 107 is equal to 1, and the refractive index n2 of the photonic crystal section 100 is equal to 3.48.

[0099] For example, in embodiments of this disclosure, the filling rate and shape of the medium in the via 101 can be adjusted as needed. For instance, in one example, the lower half of the via 101 can be filled, or only one side of the via 101 can be filled, or the via 101 can be filled in any other filling manner. The materials of the first dielectric layer 106, the photonic crystal portion 100, and the second dielectric layer 107, as well as the material of the medium filling the via 101, can be materials with optical gain or without optical gain.

[0100] For example, such as Figure 12 As shown, the photonic crystal filter 10 further includes: an n-type substrate 201; an n-type semiconductor heavily doped layer 202 and an n-type semiconductor doped layer 203 sequentially disposed on the n-type substrate 201; a p-type semiconductor doped layer 204 and a p-type semiconductor heavily doped layer 205 sequentially disposed on the side of the active layer 105 away from the n-type substrate 201; a p-type electrode layer 206 disposed on the side of the p-type semiconductor heavily doped layer 205 away from the n-type substrate 201; and an n-type electrode layer 207 disposed on the side of the n-type semiconductor heavily doped layer 202 away from the n-type substrate 201 and spaced apart from the n-type semiconductor doped layer 203. The active layer 105 is disposed on the side of the n-type semiconductor doped layer 203 away from the n-type substrate 201. The p-type semiconductor heavily doped layer 205 is configured as the second dielectric layer 107, and the p-type semiconductor doped layer 204 is configured as the photonic crystal portion 100 and the first dielectric layer 106.

[0101] For example, in Figure 12In the structure shown, the photonic crystal section 100 and the first dielectric layer 106 are formed in the same process step and are integrally molded, both being formed of a p-type semiconductor doped layer 204. It should be noted that if a first dielectric layer 106 is not retained under the photonic crystal section 100 to prevent the p-type semiconductor doped layer 204 from being penetrated, the active layer 105 may be damaged during the formation of the photonic crystal section 100, thereby weakening the light emission and light gain performance of the active layer 105.

[0102] For example, the material of the n-type substrate 201 includes, but is not limited to, GaAs, InP, GaSb or GaN. Alternatively, the n-type substrate 201 may also be a substrate formed by bonding a layer structure of GaAs, InP, GaSb or GaN onto a Si substrate using a flip-chip bonding process.

[0103] For example, the structure of the active layer 105 includes: quantum well, quantum wire or quantum dot; the material of the active layer 105 includes, but is not limited to: GaAs, AlGaAs, InGaAs, InGaAsP, GaAsP, AlGaInAs or InGaN, and the active layer 105 can be used to provide optical gain, with the peak wavelength range of the gain spectrum covering the ultraviolet to far-infrared band.

[0104] For example, the material of the n-type electrode layer 207 includes metals such as Au, AuGe, AuGe / Au, AuGeNiAu, metal alloys, or transparent conductive materials such as indium tin oxide (ITO).

[0105] For example, the material of the p-type electrode layer 206 includes, but is not limited to, metals such as Au, Ti, Pt, and Cr, and metal alloys such as TiPtAu, AuZnAu, NiAg, or CrAu. For example, the p-type electrode layer 206 can be prepared using a stripping method, a wet etching method, or a dry etching method. For example, when using a dry etching method, the gas used is not limited to fluorocarbon gas, but is based on chlorine or hydroiodic acid gas. Furthermore, argon or xenon lamp inert gas needs to be mixed into the chlorine or hydroiodic acid gas, and the ratio of chlorine or hydroiodic acid gas to inert gas is approximately 2:1.

[0106] For example, a heavily doped p-type semiconductor layer 205 is formed on the photonic crystal section 100 by epitaxial growth or bonding.

[0107] For example, the materials for other layers of the photonic crystal filter 10 can be selected from conventional materials, and the embodiments of this disclosure do not limit this. The thickness of each layer of the photonic crystal filter 10 can be determined as needed according to conventional designs, and the embodiments of this disclosure do not limit this.

[0108] It should be noted that vias 101 can also be formed in the heavily doped p-type semiconductor layer 205 to serve as the photonic crystal section 100.

[0109] For example, Figure 12 The operation of the photonic crystal filter 10 shown includes: when a positive voltage is applied to the p-type electrode layer 206, holes are injected from the heavily doped p-type semiconductor layer 205 into the active layer 105, and electrons are injected from the heavily doped n-type semiconductor layer 202 into the active layer 105. When holes and electrons (charge carriers) are injected into the active layer 105, the charge carriers recombine to emit light. The wavelength of the emitted light is defined by the band gap of the semiconductor layers included in the active layer 105.

[0110] For example, a multilayer dielectric structure is formed by p-type semiconductor heavily doped layer 205, photonic crystal layer 204, and n-type semiconductor heavily doped layer 202. Light emitted from active layer 105 excites an optical mode in the dielectric layer. The evanescent portion of this light reaches photonic crystal section 100 and diffracts with the periodic structure of photonic crystal section 100. When the wavelength of the optical mode has a defined matching relationship with the periodicity of the photonic crystal in photonic crystal section 100, the layered structure and the photonic crystal generate a stable resonant mode, which becomes the laser lasing mode.

[0111] For example, Figure 13 This is a schematic cross-sectional view of another photonic crystal filter provided in at least one embodiment of the present disclosure, as shown below. Figure 13 As shown, the photonic crystal filter 10 further includes: an n-type substrate 201; an n-type semiconductor heavily doped layer 202 and an n-type semiconductor doped layer 203 sequentially disposed on the n-type substrate 201; a p-type semiconductor doped layer 204 and a p-type semiconductor heavily doped layer 205 sequentially disposed on the side of the active layer 105 away from the n-type substrate 201; a p-type electrode layer 206 disposed on the side of the p-type semiconductor heavily doped layer 205 away from the n-type substrate 201; and an n-type electrode layer 207 disposed on the side of the n-type semiconductor heavily doped layer 202 away from the n-type substrate 201 and spaced apart from the n-type semiconductor doped layer 203; the active layer 105 is disposed on the side of the n-type semiconductor doped layer 203 away from the n-type substrate 201; the n-type semiconductor heavily doped layer 202 is configured as the second dielectric layer 107; and the n-type semiconductor doped layer 203 is configured as the photonic crystal portion 100 and the first dielectric layer 106.

[0112] For example, in Figure 13In the structure shown, a first dielectric layer 106 needs to be specially provided between the photonic crystal section 100 and the active layer 105. This first dielectric layer 106 can also be formed of an n-type semiconductor doped material to prevent the material of the active layer 105 from filling the vias 101 in the photonic crystal section 100 during the process of forming the photonic crystal section 100 with vias 101 and then forming the active layer 105. In addition, if a first dielectric layer 106 is not specially provided between the n-type semiconductor doped layer 203 and the active layer 105, it will also be detrimental to the epitaxial growth of the active layer 105.

[0113] For example, Figure 13 The operation of the photonic crystal filter 10 shown includes: when a positive voltage is applied to the p-type electrode layer 206, holes are injected from the heavily doped p-type semiconductor layer 205 into the active layer 105, and electrons are injected from the heavily doped n-type semiconductor layer 202 into the active layer 105. When holes and electrons (charge carriers) are injected into the active layer 105, the charge carriers recombine to emit light. The wavelength of the emitted light is defined by the band gap of the semiconductor layers included in the active layer 105.

[0114] For example, a multilayer dielectric structure is formed by p-type semiconductor heavily doped layer 205, photonic crystal layer 204, and n-type semiconductor heavily doped layer 202. Light emitted from active layer 105 excites an optical mode in the dielectric layer. The evanescent portion of this light reaches photonic crystal section 100 and diffracts with the periodic structure of photonic crystal section 100. When the wavelength of the optical mode has a defined matching relationship with the periodicity of the photonic crystal in photonic crystal section 100, the layered structure and the photonic crystal generate a stable resonant mode, which becomes the laser lasing mode.

[0115] For example, Figure 13 The materials and thicknesses of the various layers in the photonic crystal filter 10 shown can be found in the above description. Figure 12 The relevant descriptions in the document will not be repeated here.

[0116] For example, in embodiments of this disclosure, Figure 12 and Figure 13 The photonic crystal filter 10 shown includes a single-mode photonic crystal filter and a multimode photonic crystal filter.

[0117] At least one embodiment of this disclosure also provides a method for fabricating a photonic crystal filter. The method includes: providing a substrate; forming a first type of semiconductor doped layer thin film on the substrate; applying a resist to the first type of semiconductor doped layer thin film and pre-curing it to form a resist layer; performing nanoimprinting on the resist layer using an imprinting template to transfer the pattern of the imprinting template to the resist layer, and curing it to form a resist layer pattern; performing a patterning process on the first type of semiconductor doped layer thin film using the resist layer pattern as a mask to form a photonic crystal layer, and removing the resist layer pattern; the photonic crystal layer includes a photonic crystal portion, the photonic crystal portion including a plurality of photonic crystal units arranged in an array, each photonic crystal unit including a plurality of vias arranged in an array, each photonic crystal unit including a central region and a peripheral region surrounding the central region, the plurality of vias including a plurality of vias arranged in an array in the central region. The photonic crystal layer consists of a first through-hole and second through-holes arranged in an array in the outer region; the central region includes Na×Na first through-holes, where Na is a positive integer greater than or equal to 5; the number of second through-holes on each side of the outer region is Na×Nb, where Nb is a positive integer greater than or equal to 1; the minimum distance between two adjacent first through-holes is the first spacing Da, the minimum distance between two adjacent second through-holes is the second spacing Db, and the minimum distance between the first and second through-holes is the third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm. The photonic crystal layer is prepared by nanoimprint technology, which can reduce production costs and improve production efficiency, and is suitable for large-scale production, thereby reducing production costs and ensuring robustness. In addition, the quality factor of the photonic crystal layer prepared by conventional electron beam exposure method is not significantly improved compared with the photonic crystal layer prepared by nanoimprint technology.

[0118] For example, Figure 14 A flowchart illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of this disclosure is shown below. Figure 14 As shown, the preparation method includes the following steps.

[0119] S11: Provides a substrate.

[0120] S12: Forming a first type of semiconductor doped thin film on a substrate.

[0121] S13: Apply a resist to the first type of semiconductor doped thin film and pre-cur it to form a resist layer.

[0122] S14: Nanoimprinting is performed on the resist layer using an imprinting template to transfer the pattern of the imprinting template to the resist layer, and then the resist layer is cured to form a resist layer pattern.

[0123] S15: Using the resist layer pattern as a mask, a patterning process is performed on a first type of semiconductor doped thin film to form a photonic crystal layer, and the resist layer pattern is removed. The photonic crystal layer includes a photonic crystal section, which includes multiple photonic crystal units arranged in an array. Each photonic crystal unit includes multiple vias arranged in an array. Each photonic crystal unit includes a central region and a peripheral region surrounding the central region. The multiple vias include first vias arranged in an array in the central region and second vias arranged in an array in the peripheral region. The central region includes Na×Na first vias, where Na is a positive integer greater than or equal to 5. The number of second vias on each edge of the peripheral region is Na×Nb, where Nb is a positive integer greater than or equal to 1. The minimum distance between two adjacent first vias is a first spacing Da, the minimum distance between two adjacent second vias is a second spacing Db, and the minimum distance between a first via and a second via is a third spacing Dg, satisfying Na*Da+Nb*Db+Dg≤10μm.

[0124] For example, Figures 15A-15E This is a process diagram illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of the present disclosure.

[0125] like Figure 15A As shown, a substrate 301 is provided. The substrate can be an n-type substrate. The material of the n-type substrate includes, but is not limited to, GaAs, InP, GaSb or GaN. Alternatively, the n-type substrate can also be a substrate formed by bonding a layer structure of GaAs, InP, GaSb or GaN onto a Si substrate using a flip-chip bonding process.

[0126] For example, processing the substrate 301 includes cleaning and surface treatment of the substrate 301 to ensure the flatness and cleanliness of the surface of the substrate 301.

[0127] For example, such as Figure 15B As shown, a first type of semiconductor doped layer thin film 302 is formed on a substrate 301. For example, the first type of semiconductor doped layer thin film 302 can be an n-type semiconductor doped layer thin film or a p-type semiconductor doped layer thin film. For example, the first type of semiconductor doped layer thin film 302 can be formed by epitaxial growth.

[0128] For example, a first type of semiconductor doped layer film 302 can be applied to the substrate 301 using equipment such as a spin coater or a coating machine. This allows the adhesive to be uniformly coated on the surface of the substrate and controls the thickness and uniformity of the first type of semiconductor doped layer film 302.

[0129] For example, such as Figure 15CAs shown, a photoresist is applied to the first type of semiconductor doped thin film 302 and pre-cured to form a photoresist layer 303. For example, a liquid photoresist can be applied to the first type of semiconductor doped thin film 302, and then pre-cured to make it in a non-free-flowing state, i.e., a semi-solid state, which ensures that the subsequent imprint stencil 304 can transfer its pattern onto the photoresist layer 303. For example, the method of pre-curing the photoresist includes ultraviolet light irradiation or temperature curing.

[0130] For example, such as Figure 15D As shown, an imprinting template 304 is used to nanoimprint the resist layer 303 to transfer the pattern of the imprinting template 304 to the resist layer 303, and then it is cured to form the resist layer pattern 305. That is, in Figure 15D The process of transferring the pattern of the imprint template 304 to the resist layer 303 is completed. For example, the portion of the resist layer pattern 305 that covers the first type of semiconductor doped film is the portion retained by the first type of semiconductor doped film, and the uncovered portion is the etched portion. For example, this nanoimprint technology includes ultraviolet nanoimprint technology or thermal nanoimprint technology. For example, the method of curing the resist layer 303 includes ultraviolet light irradiation or cooling curing.

[0131] For example, in one example, the technique for nanoimprinting the resist layer 303 is ultraviolet nanoimprinting, and the method for curing the resist layer 303 is ultraviolet light irradiation; in another example, the technique for nanoimprinting the resist layer 303 is thermal nanoimprinting, and the method for curing the resist layer 303 is cooling curing.

[0132] For example, such as Figure 15E As shown, a patterning process is performed on the first type of semiconductor doped thin film 302 using the resist layer pattern 305 as a mask to form a photonic crystal layer, and then the resist layer pattern 305 is removed. The planar structure of the photonic crystal portion 100 included in this photonic crystal layer can be found in the above description. Figure 2-11 This will not be elaborated upon here.

[0133] It should be noted that, in Figure 15E In one embodiment, a portion of the first type of semiconductor doped layer film 302 near the substrate 301 is retained as the first dielectric layer. In other embodiments, the first type of semiconductor doped layer film 302 may be etched through, and the portion of the first type of semiconductor doped layer film 302 near the substrate 301 may not be retained.

[0134] For example, it should also be noted that the first type of semiconductor doped layer thin film can be a first type of heavily doped semiconductor thin film.

[0135] For example, the patterning process includes steps such as exposure, development, etching, and resist stripping. Specifically, after performing proof effect correction (PEC) on the deposited film, the coated chip is placed in an electron beam lithography machine or photolithography machine, and then an electron beam is used to scan or pass through a mask onto the resist surface to form the desired pattern. The exposed photoresist is then chemically treated, causing it to dissolve or solidify in the developer, thereby forming the desired pattern. Etching and resist stripping involve using chemical or physical methods to completely remove the unexposed resist layer from the surface of the substrate, while protecting the resist layer in the exposed areas from damage, exposing the underlying substrate or the underlying photonic crystal structure. Finally, a suitable solvent or chemical solution is used to dissolve or remove the remaining photoresist to ensure the integrity and clarity of the photonic crystal layer structure.

[0136] For example, Figure 16 A flowchart illustrating a method for fabricating another photonic crystal filter according to at least one embodiment of this disclosure is shown below. Figure 16 As shown, the preparation method includes the following steps.

[0137] S21: Provide a substrate, on which a second type of heavily doped semiconductor thin film, a second type of semiconductor doped thin film, an active layer thin film and a first type of semiconductor doped thin film are sequentially formed.

[0138] S22: Apply a resist to the first type of semiconductor doped thin film and pre-cur it to form a resist layer.

[0139] S23: Nanoimprinting is performed on the resist layer using an imprinting template to transfer the pattern of the imprinting template to the resist layer, and then the resist layer is cured to form a resist layer pattern.

[0140] S24: Using the resist layer pattern as a mask, a patterning process is performed on the first type of semiconductor doped layer thin film to form a photonic crystal layer and a first dielectric layer thin film, and the resist layer pattern is removed. The first dielectric layer thin film is located on the side of the photonic crystal layer closest to the substrate. The photonic crystal layer includes a plurality of vias arranged in an array. The photonic crystal layer includes a photonic crystal portion, and the photonic crystal portion includes a plurality of photonic crystal units arranged in an array. Each photonic crystal unit includes a plurality of vias arranged in an array. Each photonic crystal unit includes a central region and a peripheral region surrounding the central region. The plurality of vias are included in the central region. The central region has a first through-hole array and a second through-hole array in the outer region. The central region includes Na×Na first through-holes, where Na is a positive integer greater than or equal to 5. The number of second through-holes on each side of the outer region is Na×Nb, where Nb is a positive integer greater than or equal to 1. The minimum distance between two adjacent first through-holes is the first spacing Da, the minimum distance between two adjacent second through-holes is the second spacing Db, and the minimum distance between the first and second through-holes is the third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm.

[0141] S25: A first type of semiconductor heavily doped thin film, a hard mask, and a photoresist layer are sequentially formed on the side of the photonic crystal layer away from the substrate.

[0142] S26: Pattern the photoresist layer to form a photoresist pattern covering a preset area, use the photoresist pattern as a mask to pattern the hard mask and remove the photoresist pattern to form a hard mask pattern.

[0143] S27: Using a hard mask pattern as a mask, a patterning process is performed on a first type of semiconductor heavily doped layer thin film, a photonic crystal layer, a first dielectric layer thin film, an active layer thin film, and a second type of semiconductor doped layer thin film to form a second dielectric layer, a photonic crystal layer, a first dielectric layer, an active layer, and a second type of semiconductor doped layer, respectively. There is a gap between the edge of the orthogonal projection of the second type of semiconductor doped layer on the substrate and the edge of the orthogonal projection of the second type of semiconductor heavily doped layer thin film on the substrate.

[0144] S28: Remove the hard mask pattern, form a p-type electrode layer on the side of the second dielectric layer away from the substrate, and form an n-type electrode layer in the gap on the side of the second type of semiconductor heavily doped layer film away from the substrate.

[0145] For example, Figures 17A-17H This is a process diagram illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of the present disclosure.

[0146] For example, such as Figure 17AAs shown, a substrate 301 is provided, on which a second type of semiconductor heavily doped layer thin film 306, a second type of semiconductor doped layer thin film 307, an active layer thin film 308 and a first type of semiconductor doped layer thin film 302 are sequentially formed.

[0147] For example, the first type of semiconductor doped layer film 302 is a p-type semiconductor doped layer film, the second type of semiconductor doped layer film 307 is an n-type semiconductor doped layer film, and the second type of heavily doped semiconductor layer film 306 is a heavily doped n-type semiconductor layer film. The heavily doped n-type semiconductor layer film 306, the n-type semiconductor doped layer film 307, the active layer film 308, and the p-type semiconductor doped layer film 302 are sequentially stacked on the substrate 301. For example, the p-type semiconductor doped layer film can be formed by epitaxial growth.

[0148] For example, the active layer formed by the active layer film 308 can emit light and can serve as an optical gain medium. The material of the active layer film 308 can be found in the relevant design described above, and will not be repeated here.

[0149] For example, such as Figure 17B As shown, a photoresist is applied to the first type of semiconductor doped layer film 302 and pre-cured to form a photoresist layer 303. Specifically, a photoresist is applied to the n-type semiconductor doped layer film 302 and pre-cured to form the photoresist layer 303. For example, a liquid photoresist can be applied to the n-type semiconductor doped layer film 302 and then pre-cured to make it non-free-flowing, i.e., semi-solid, ensuring that the imprint stencil 304 can transfer its pattern onto the photoresist layer 303. For example, methods for pre-curing the photoresist include ultraviolet light irradiation or temperature curing.

[0150] For example, such as Figure 17C As shown, an imprinting template 304 is used to perform nanoimprinting on the resist layer 303 to transfer the pattern of the imprinting template 304 to the resist layer 303, and then the resist layer is cured to form a resist layer pattern 305.

[0151] For example, the nanoimprinting technology includes ultraviolet nanoimprinting or thermal nanoimprinting.

[0152] For example, methods for curing the corrosion inhibitor layer 303 include ultraviolet light irradiation or cooling curing.

[0153] For example, in one example, the technique for nanoimprinting the resist layer 303 is ultraviolet nanoimprinting, and the method for curing the resist layer 303 is ultraviolet light irradiation; in another example, the technique for nanoimprinting the resist layer 303 is thermal nanoimprinting, and the method for curing the resist layer 303 is cooling curing.

[0154] For example, such as Figure 17D As shown, a patterning process is performed on a first type of semiconductor doped layer thin film 302 (p-type semiconductor doped layer thin film) using the resist layer pattern 305 as a mask to form a photonic crystal layer and a first dielectric layer thin film 309, and then the resist layer pattern 305 is removed. The first dielectric layer thin film 309 is located on the side of the photonic crystal layer closest to the substrate 301. The planar structure of the photonic crystal portion 100 included in the photonic crystal layer can be found in the above description. Figure 2-11 As shown, it will not be elaborated further here.

[0155] For example, photonic crystals fabricated using nanoimprint technology include holes of various shapes, hole arrays, nanogrooves of various shapes, and combinations of various nanostructures, which are not limited in the embodiments disclosed herein.

[0156] For example, during the process of forming a photonic crystal layer by patterning a p-type semiconductor doped layer thin film using the resist layer pattern 305 as a mask, a first dielectric layer thin film 309 is simultaneously formed on the side of the photonic crystal layer near the substrate 301, and the photonic crystal layer and the first dielectric layer thin film 309 are an integral structure. The first dielectric layer thin film 309 has a certain thickness and is also retained in the region corresponding to the via 101, that is, the first dielectric layer thin film 309 is a continuous single layer structure.

[0157] For example, such as Figure 17D As shown, the first dielectric layer film 309 is formed between the active layer film 308 and the photonic crystal portion 100. The presence of the first dielectric layer film 309 can prevent the first type of semiconductor doped layer film 302 from being etched through, thereby preventing any impact on the performance of the active layer film 308.

[0158] For example, the portion of the first type of semiconductor doped layer film 302 covered by the resist layer pattern 305 is the portion retained by the first type of semiconductor doped layer film, and the portion not covered is the portion etched away.

[0159] For example, such as Figure 17DAs shown, the second type of semiconductor doped layer film 307 and active layer film 308 are disposed on the same surface of the substrate 301 and stacked with the photonic crystal portion 100, and the active layer film 308 is sandwiched between the photonic crystal portion 100 and the second type of semiconductor doped layer film 306. The second type of heavily doped semiconductor layer film 306 is formed on the side of the second type of semiconductor doped layer film 307 away from the active layer film 308.

[0160] For example, such as Figure 17E As shown, a first type of semiconductor heavily doped layer thin film 310 (p-type semiconductor heavily doped layer thin film), a hard mask 311 and a photoresist layer 312 are sequentially formed on the side of the photonic crystal layer away from the substrate 301.

[0161] For example, the first type of semiconductor heavily doped layer thin film 310 can be formed on the surface of the photonic crystal layer by epitaxial growth. The hard mask 311 is made of silicon dioxide and can be formed by epitaxial growth or coating, and then a photoresist layer 312 is coated on the hard mask 311.

[0162] For example, such as Figure 17F As shown, the photoresist layer 312 is patterned to form a photoresist pattern 313 covering a preset area. The hard mask 311 is patterned using the photoresist pattern 313 as a mask and the photoresist pattern 313 is removed to form a hard mask pattern 314.

[0163] For example, the preset area is the mesa area of ​​the photonic crystal filter. The mesa area of ​​the photonic crystal filter can be defined by electron beam exposure and development. Then, the portion of the hard mask 311 other than the mesa area is etched away to form the hard mask pattern 314.

[0164] For example, such as Figure 17GAs shown, a patterning process is performed using a hard mask pattern 314 as a mask to form a first type of heavily doped semiconductor thin film 310 (second dielectric layer film), a photonic crystal layer, a first dielectric layer film 309, an active layer film 308, and a second type of semiconductor doped layer film 307 (n-type semiconductor doped layer film), respectively forming a second dielectric layer 107, a photonic crystal portion 100, a first dielectric layer 106, an active layer 105, and a second type of semiconductor doped layer 203 (n-type semiconductor doped layer 203). A gap exists between the edge of the orthogonal projection of the second type of semiconductor doped layer 203 (n-type semiconductor doped layer 203) onto the substrate 301 and the edge of the orthogonal projection of the second type of heavily doped semiconductor thin film 306 (n-type semiconductor doped layer film) onto the substrate 301. That is, the mesa of the photonic crystal filter is etched using the hard mask pattern 314 as a mask until the second type of heavily doped semiconductor thin film 306 is exposed, and then the hard mask pattern 314 is removed.

[0165] For example, such as Figure 17G As shown, the first type of heavily doped semiconductor thin film 310 can serve as a second dielectric layer thin film, which can be etched to form a second dielectric layer 107, combined with... Figure 12 Each via 101 includes a first end 1011 and a second end 1012 along the extension direction of its channel. The first end 1011 is connected to the first dielectric layer 106, and the second end 1012 is connected to the second dielectric layer 107.

[0166] For example, such as Figure 17H As shown, the hard mask pattern 314 is removed, a p-type electrode layer 316 is formed on the side of the second dielectric layer 107 away from the substrate 301, and an n-type electrode layer 317 is formed in the gap on the side of the second type of semiconductor heavily doped layer thin film 306 away from the substrate 301.

[0167] For example, the p-type electrode layer 316 can be formed by depositing p-type electrode material, and the n-type electrode layer 317 can be formed by depositing n-type electrode material. The embodiments disclosed herein are not limited in this respect, as long as the p-type electrode layer 316 and the n-type electrode layer 317 can be prepared.

[0168] For example, through Figures 17A-17H The structure of the formed photonic crystal filter can be seen above. Figure 12 The relevant descriptions in the document will not be repeated here.

[0169] It should be noted that the photonic crystal section can also be formed in the first type of semiconductor heavily doped layer film 310. In this case, the formation steps of the first type of semiconductor heavily doped layer film 310 and the first type of semiconductor doped layer film 302 need to be interchanged, while the other process steps remain unchanged.

[0170] For example, Figure 18 A flowchart illustrating a method for fabricating another photonic crystal filter according to at least one embodiment of this disclosure is shown below. Figure 18 As shown, the preparation method includes the following steps.

[0171] S31: Provide a substrate, on which a first type of heavily doped semiconductor thin film and a first type of semiconductor doped thin film are sequentially formed.

[0172] S32: Apply a resist to the first type of semiconductor doped thin film and pre-cur it to form a resist layer.

[0173] S33: Nanoimprinting is performed on the resist layer using an imprinting template to transfer the pattern of the imprinting template to the resist layer, and then the resist layer is cured to form a resist layer pattern.

[0174] S34: Using the resist layer pattern as a mask, a patterning process is performed on a first type of semiconductor doped layer thin film to form a photonic crystal layer, and the resist layer pattern is removed. The photonic crystal layer includes a photonic crystal section, which includes multiple photonic crystal units arranged in an array. Each photonic crystal unit includes multiple vias arranged in an array. Each photonic crystal unit includes a central region and a peripheral region surrounding the central region. The multiple vias include first vias arranged in an array in the central region and second vias arranged in an array in the peripheral region. The central region includes Na×Na first vias, where Na is a positive integer greater than or equal to 5. The number of second vias on each side of the peripheral region is Na×Nb, where Nb is a positive integer greater than or equal to 1. The minimum distance between two adjacent first vias is a first spacing Da, the minimum distance between two adjacent second vias is a second spacing Db, and the minimum distance between the first and second vias is a third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm.

[0175] S35: The first dielectric layer thin film is epitaxially grown on the photonic crystal layer.

[0176] S36: A second type of semiconductor doped layer film, a second type of heavily doped semiconductor layer film, a hard mask, and a photoresist layer are sequentially formed on the side of the first dielectric layer film away from the substrate.

[0177] S37: Pattern the photoresist layer to form a photoresist pattern covering a preset area, use the photoresist pattern as a mask to pattern the hard mask and remove the photoresist pattern to form a hard mask pattern.

[0178] S38: Using a hard mask pattern as a mask, a patterning process is performed on the second type of semiconductor heavily doped layer thin film, the second type of semiconductor doped layer thin film, the active layer thin film, the first dielectric layer thin film, and the photonic crystal layer to form the second type of semiconductor heavily doped layer, the second type of semiconductor doped layer, the active layer, the first dielectric layer, and the photonic crystal portion, respectively, and there is a gap between the edge of the orthogonal projection of the photonic crystal portion on the substrate and the edge of the orthogonal projection of the first type of semiconductor heavily doped layer thin film on the substrate.

[0179] S39: Remove the hard mask pattern, form a p-type electrode layer on the side of the second type of semiconductor heavily doped layer away from the substrate, and form an n-type electrode layer in the gap on the side of the first type of semiconductor heavily doped layer film away from the substrate.

[0180] For example, Figure 19A-19I This is a process diagram illustrating a method for fabricating a photonic crystal filter according to at least one embodiment of the present disclosure.

[0181] For example, such as Figure 19A As shown, a substrate 301 is provided, on which a first type of semiconductor heavily doped layer thin film 310 and a first type of semiconductor doped layer thin film 302 are sequentially formed.

[0182] For example, the first type of semiconductor doped layer film 302 is an n-type semiconductor doped layer film, and the first type of heavily doped semiconductor layer film 310 is also an n-type heavily doped semiconductor layer film. The n-type heavily doped semiconductor layer film and the n-type semiconductor doped layer film are sequentially stacked on the substrate 301. For example, the n-type heavily doped semiconductor layer film and the n-type semiconductor doped layer film can be formed by epitaxial growth. The second type of semiconductor doped layer film mentioned later is a p-type semiconductor doped layer.

[0183] For example, such as Figure 19BAs shown, a photoresist is applied to the first type of semiconductor doped layer film 302 and pre-cured to form a photoresist layer 303. Specifically, a photoresist is applied to the n-type semiconductor doped layer film 302 and pre-cured to form the photoresist layer 303. For example, a liquid photoresist can be applied to the n-type semiconductor doped layer film 302 and then pre-cured to make it non-free-flowing, i.e., semi-solid, ensuring that the imprint stencil 304 can transfer its pattern onto the photoresist layer 303. For example, methods for pre-curing the photoresist include ultraviolet light irradiation or temperature curing.

[0184] For example, such as Figure 19C As shown, an imprinting template 304 is used to perform nanoimprinting on the resist layer 303 to transfer the pattern of the imprinting template 304 to the resist layer 303, and then the resist layer is cured to form a resist layer pattern 305.

[0185] For example, the nanoimprinting technology includes ultraviolet nanoimprinting or thermal nanoimprinting.

[0186] For example, methods for curing the corrosion inhibitor layer 303 include ultraviolet light irradiation or cooling curing.

[0187] For example, in one example, the technique for nanoimprinting the resist layer 303 is ultraviolet nanoimprinting, and the method for curing the resist layer 303 is ultraviolet light irradiation; in another example, the technique for imprinting the resist layer 303 is thermal nanoimprinting, and the method for curing the resist layer 303 is cooling curing.

[0188] For example, such as Figure 19DAs shown, a patterning process is performed on a first type of semiconductor doped layer thin film 302 (n-type semiconductor doped layer thin film) using the resist layer pattern 305 as a mask to form a photonic crystal layer, and then the resist layer pattern 305 is removed. The photonic crystal layer includes multiple vias arranged in an array. The photonic crystal layer includes a photonic crystal section, which in turn includes multiple photonic crystal units arranged in an array. Each photonic crystal unit includes multiple vias arranged in an array. Each photonic crystal unit includes a central region and a peripheral region surrounding the central region. The multiple vias include first vias arranged in an array in the central region and second vias arranged in an array in the peripheral region. The central region includes Na×Na first vias, where Na is a positive integer greater than or equal to 5. The number of second vias on each side of the peripheral region is Na×Nb, where Nb is a positive integer greater than or equal to 1. The minimum distance between two adjacent first vias is a first spacing Da, the minimum distance between two adjacent second vias is a second spacing Db, and the minimum distance between a first via and a second via is a third spacing Dg, satisfying Na*Da+Nb*Db+Dg≤10μm.

[0189] For example, the portion of the first type of semiconductor doped layer film 302 covered by the resist layer pattern 305 is the portion retained by the first type of semiconductor doped layer film, and the portion not covered is the portion etched away.

[0190] For example, photonic crystals fabricated using nanoimprint technology include holes of various shapes, hole arrays, nanogrooves of various shapes, and combinations of various nanostructures, which are not limited in the embodiments disclosed herein.

[0191] For example, such as Figure 19E As shown, a first dielectric layer thin film 309 is epitaxially grown on the photonic crystal layer.

[0192] For example, the first dielectric layer thin film 309 is on the side of the photonic crystal layer away from the substrate 301.

[0193] For example, such as Figure 19F As shown, an active layer film 308, a second type of semiconductor doped layer film 307, a second type of semiconductor heavily doped layer film 306, a hard mask 311 and a photoresist layer 312 are sequentially formed on the side of the first dielectric layer film 309 away from the substrate 301.

[0194] For example, the second type of semiconductor doped layer thin film 307 can be formed on the surface of the first dielectric layer thin film 309 by epitaxial growth. The hard mask 311 is made of silicon dioxide and can be formed by epitaxial growth or coating, and then a photoresist layer 312 is coated on the hard mask 311.

[0195] For example, such as Figure 19G As shown, the photoresist layer 312 is patterned to form a photoresist pattern 313 covering a preset area. The hard mask 311 is patterned using the photoresist pattern 313 as a mask and the photoresist pattern 313 is removed to form a hard mask pattern 314.

[0196] For example, the preset area is the mesa area of ​​the photonic crystal filter. The mesa area of ​​the photonic crystal filter can be defined by electron beam exposure and development. Then, the portion of the hard mask 311 other than the mesa area is etched away to form the hard mask pattern 314.

[0197] For example, such as Figure 19H As shown, a patterning process is performed on the second type of heavily doped semiconductor thin film 306, the second type of heavily doped semiconductor thin film 307, the active layer thin film 308, the first dielectric layer thin film 309, and the photonic crystal layer using hard mask pattern 314 as a mask to form the second type of heavily doped semiconductor layer (p-type semiconductor heavily doped layer 205), the second type of semiconductor doped layer (p-type semiconductor doped layer 204), the active layer 105, the first dielectric layer 106, and the photonic crystal section 100, respectively. A gap exists between the edge of the orthogonal projection of the photonic crystal section 100 onto the substrate 301 and the edge of the orthogonal projection of the first type of heavily doped semiconductor thin film 310 (n-type semiconductor heavily doped layer thin film) onto the substrate 301. That is, the mesa of the photonic crystal filter is etched using hard mask pattern 314 as a mask until the first type of heavily doped semiconductor thin film 310 is exposed, and then the hard mask pattern 314 is removed.

[0198] For example, such as Figure 19H As shown, the active layer 105 can emit light and can also serve as an optical gain medium. The material of the active layer thin film 105 can be found in the relevant design described above, and will not be repeated here.

[0199] For example, such as Figure 19H As shown, the first type of heavily doped semiconductor thin film 310 can serve as a second dielectric layer thin film, which is the second dielectric layer, combined with Figure 13 Each via 101 includes a first end 1011 and a second end 1012 along its channel extension direction. The first end 1011 is connected to a first dielectric film 309 (which will be subsequently formed into a first dielectric layer), and the second end 1012 is connected to a second dielectric film 310 (which will be subsequently formed into a first dielectric layer).

[0200] For example, such as Figure 19IAs shown, the hard mask pattern 314 is removed, and a p-type electrode layer 316 is formed on the side of the second type of semiconductor heavily doped layer 205 away from the substrate 301, and an n-type electrode layer 317 is formed in the gap on the side of the first type of semiconductor heavily doped layer thin film 310 away from the substrate 301.

[0201] For example, the p-type electrode layer 316 can be formed by depositing p-type electrode material, and the n-type electrode layer 317 can be formed by depositing n-type electrode material. The embodiments disclosed herein are not limited in this respect, as long as the p-type electrode layer 316 and the n-type electrode layer 317 can be prepared.

[0202] For example, through Figure 19A-19I The structure of the formed photonic crystal filter can be seen above. Figure 13 The relevant descriptions in the document will not be repeated here.

[0203] It should be noted that the photonic crystal section can also be formed in the first type of semiconductor heavily doped layer film 310. In this case, the formation steps of the first type of semiconductor heavily doped layer film 310 and the first type of semiconductor doped layer film 302 need to be interchanged, while the other process steps remain unchanged.

[0204] For example, Figure 20 A block diagram of a spectral detection system provided in at least one embodiment of this disclosure, such as Figure 20 As shown, the spectral detection system 400 includes: a semi-transparent and semi-reflective mirror 401, an objective lens 402, an imaging structure 403, a 4f optical system 404, and a photonic crystal filter 10 in any of the above embodiments.

[0205] For example, the pattern of the structure under test can be detected through the optical path based on the 4f optical system 404. The rich patterns generated within the extremely small array unit volume represent the high-Q resonant peaks corresponding to different characteristic wavelengths produced by the structure under test. The method of spectral detection using this system can be performed through out-of-plane excitation, thus eliminating the need for coupling and modulation. Furthermore, the system has a simple structure, and higher spectral detection accuracy can be achieved through simple photonic crystal arraying, with adjustable accuracy. In addition, the smaller size of the spectral detection system facilitates further miniaturization of spectrometers.

[0206] For example, a 4f optical system refers to a system where, when two coherent polarized beams of light are input, they pass through special optical devices such as cosine gratings and exchange planes, causing the input light to produce a diffraction pattern on a screen. A precisely laterally moving cosine grating can continuously change the phase difference between the diffraction orders of the two beams, achieving the purpose of subtracting or adding the diffracted light intensities. This means it has two lenses with a focal length of f, separated by a distance of 2f, and an object distance of f, also separated by a distance of f. Therefore, it is a 4f optical system, and only optical systems with a distance greater than 4f can function as zoom systems.

[0207] For example, combining Figure 11 The planar structure of the photonic crystal filter is based on a 600nm SOI process platform and a measurement system integrating a 4f optical system and polarization filtering. The SOI pattern is first written field calibrated (PEC) using Beamer software. The write field size is selected as 500 μm * 500 μm, and the sub-write field size is selected as 10 μm * 10 μm. The write field calibration is achieved using Beamer software. The photonic crystal microcavity pattern is fabricated by electron beam lithography (EBL) and inductively coupled plasma etching (ICP), resulting in a size of approximately 10 μm × 10 μm.

[0208] For example, a multispectral light source is controlled by a host computer, and a pattern of appropriate size is presented on the imaging structure 403 through a 4f optical system. At the same time, the host computer synchronously captures and records the presented pattern and PD response. The magnification of the 4f optical system 404 is 0.5.

[0209] The embodiments of this disclosure solve the problem of a spectral detection system and a spectral detection method based on a photonic crystal filter. The spectral detection system includes a photonic crystal unit with regular shape units. Each regular shape unit has multiple frequency selection capabilities at different wavelengths. The frequency selection capability can be adjusted according to the required spectral recovery accuracy. Moreover, the wavelengths corresponding to the characteristic frequencies of adjacent units in the array unit are uncorrelated, thereby effectively avoiding coupling between adjacent units in the array unit due to similar wavelengths.

[0210] For example, a spectral detection method includes forming a spectrum to be measured with different characteristics, inputting the spectrum to be measured into a spectral detection system as described above, so as to distinguish the spectra to be measured with different characteristics, and the spectral detection method includes the following steps.

[0211] First, the light source illuminates the object, and the host computer generates a spectrum with different characteristics. After polarization filtering, the light passes through a semi-transparent and semi-reflective mirror. A portion of the light passes through the objective lens and illuminates the photonic crystal filter. The reflected light from the photonic crystal filter passes through the objective lens again and returns to the semi-transparent and semi-reflective mirror, allowing this portion of the light to enter the 4f optical system. The 4f optical system is designed with a magnification that matches the field of view and the imaging structure, and the imaging structure displays the near-field pattern generated by the light passing through the photonic crystal filter.

[0212] Second, the host computer modulates the broadband light source by controlling the waveform shaper, and records the pattern of the imaging structure under different spectra by measuring the test optical path. Combining the filtering characteristics of the photonic crystal filter, the recorded data is processed and analyzed by a neural network to obtain the spectral information of the light source under test.

[0213] Third, the neural network was trained by recording a large number of input unknown spectra and corresponding near-field patterns from the tests as input. A pre-trained EfficientNet-B0 model was used, combined with a custom loss function incorporating cosine similarity loss and mean squared error loss. Specific learning rate adjustment mechanisms and regularization were employed to prevent overfitting and improve training performance. The entire process included data preparation, model training, validation, and testing, and the loss curves during training were visualized.

[0214] For example, the photonic crystal filter provided in the embodiments of this disclosure can achieve the following technical effects when applied to a spectral detection system: the photonic crystal filter generates abundant high-Q resonances and corresponding rich near-field pattern features, has excellent frequency selection characteristics in a very small volume, and can be adapted to more application scenarios through out-of-plane coupling. In addition, spectral detection can be achieved without calibration through neural network training, and has good robustness to process errors in manufacturing, thus facilitating large-scale industrial production.

[0215] For example, Figure 21 The pattern of a photonic crystal microcavity array, measured by a spectral testing system with a photonic crystal filter, is provided in at least one embodiment of this disclosure. Figure 21In the spectral testing process shown, the input wavelength was 1550 nm and the linewidth was 10 pm. After considering inherent CMOS noise and ambient background noise, 2% Gaussian noise was added to 40% of the acquired images. These processed images were used as input to the neural network. The spectral reconstruction network is based on the EfficientNet-B0 architecture, with a grayscale image resolution of 1280×1024×1 as input. Initial features are extracted by sampling the image through an initial 3×3 convolutional layer. Subsequent networks use the MBConv module to optimize computational efficiency, progressively adjusting the number of channels and reducing the spatial resolution, and finally generating a 1280-dimensional vector through global average pooling. The fully connected layer outputs 1600 nodes, supporting spectral reconstruction tasks with a wavelength range of 80 nm and an accuracy of 0.05 nm. The neural network uses the Swish activation function and applies batch normalization and dropout (dropout rate of 30%) regularization after each convolutional neural network and fully connected layer to prevent overfitting. During training, the AdamW optimizer was used with an initial learning rate of 0.0001. Learning rate decay was applied as performance on the validation set plateaued. The loss function was a combination of MSE and cosine similarity, evaluated between the network output and a standard spectrum. The model was trained over 90 epochs, with performance monitored on the validation set and a final evaluation on the test set. Finally, the model weights and prediction results were saved. The entire process included data preparation, model training, validation, and testing, and the loss curves during training were visualized.

[0216] For example, Figure 22 The loss curve of the demodulation spectral neural network training process provided in at least one embodiment of this disclosure is shown in the figure. Figure 22 As can be seen from this, the loss value obtained during training is around 10. -3 The goodness of fit of the spectral solution is greater than 97%, and the difference is due to non-idealities caused by process errors, sensitivity of imaging structures, noise, etc.

[0217] For example, Figure 23 The demodulation spectral performance characterization diagram provided for at least one embodiment of this disclosure, such as Figure 23 As shown, when the input spectrum is a multi-peak spectrum, the spectral detection system and test results provided by the embodiments of this disclosure demonstrate spectral demodulation capability, exhibiting a bandwidth of 80 nm and a resolution of 0.25 nm in the reconstruction of multi-feature spectra with different characteristics, such as high and low amplitudes and multiple linewidths.

[0218] The spectral testing system for two-dimensional photonic crystal microcavity arrays designed using the above method can be applied to fields such as microcavity array sensors and microcavity detectors.

[0219] For example, in microcavity sensors, the photonic crystal filter provided in the embodiments of this disclosure has the characteristics of strong frequency selectivity and wide detection range, that is, it has the characteristic of high wavelength resolution as a microcavity sensor. Therefore, the influence of environmental factors such as temperature and humidity on the microcavity sensor can be measured by measuring the change of the pattern of the two-dimensional photonic crystal microcavity array, so as to prepare a sensor with high sensitivity.

[0220] For example, in a spectral imager, the photonic crystal filter provided in the embodiments of this disclosure has the characteristics of miniaturization and wide spectral detection range. That is, it can be used as a spectral imager with imaging and high wavelength resolution by tiling. Therefore, a spectral imager with spatial data can be prepared by measuring the set of multiple array patterns after tiling and using an imaging algorithm.

[0221] For example, Figure 24 Simulation performance diagrams of the spectral detection system provided in at least one embodiment of this disclosure to avoid the write field splicing problem are shown below. Figure 24 As shown, simulations were performed to compare the performance of structural units larger than and smaller than 10 μm x 10 μm (Na=7, Nb=8) when problems such as write field splicing, mechanical movement, field distortion, and edge effects exist in electron beam exposure. When an 80 nm offset occurs in the x or y direction beyond the 10 μm x 10 μm write field range, the microcavity Q-value decreases from 22 × 10⁻⁶. 4 Decreased to 8×10 4 However, the structure proposed in the embodiments of this disclosure (Na=6, Nb=7) does not exhibit this effect when write field offset occurs, and can maintain a Q value of 16×10. 4 The array units proposed in the embodiments of this disclosure, which are smaller than 10 micrometers * 10 micrometers, can effectively avoid the above-mentioned problems, thus enabling the spectral detection system to have high robustness.

[0222] The spectral detection system and method provided in the embodiments of this disclosure can detect the pattern of the structure to be detected through the optical path based on the 4f optical system. In addition, it can generate rich patterns in a very small array unit volume, which represents the high Q resonance peaks of different characteristic wavelengths generated by the structure to be detected, thereby realizing the detection of the spectrum to be detected.

[0223] The following points need to be explained:

[0224] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure. Other structures can be referred to the general design.

[0225] (2) For clarity, the thickness of layers or regions in the drawings used to describe embodiments of the present disclosure is enlarged or reduced, i.e., these drawings are not drawn to actual scale.

[0226] (3) Where there is no conflict, the embodiments of this disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

[0227] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. The scope of protection of this disclosure should be determined by the scope of protection of the claims.

Claims

1. A photonic crystal filter, comprising: The photonic crystal section, in which, The photonic crystal section includes multiple photonic crystal units arranged in an array, and each photonic crystal unit includes multiple through-holes arranged in an array. Each of the photonic crystal units includes a central region and a peripheral region surrounding the central region, and the plurality of vias includes a first via arranged in an array in the central region and a second via arranged in an array in the peripheral region; The central region includes Na×Na first through holes, where Na is a positive integer greater than or equal to 5; The number of second through holes on each side of the outer perimeter region is Na×Nb, where Nb is a positive integer greater than or equal to 1; The minimum distance between two adjacent first through holes is the first spacing Da, the minimum distance between two adjacent second through holes is the second spacing Db, and the minimum distance between the first through hole and the second through hole is the third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm; The minimum distance between two adjacent photonic crystal units is the fourth spacing Nag, and the fourth spacing Nag is greater than or equal to 5 micrometers and less than or equal to 10 micrometers.

2. The photonic crystal filter according to claim 1, wherein, The central region and the peripheral region are further divided into a transition region. The through-holes also include third through-holes arranged in an array in the transition region. The minimum distance between any two adjacent third through-holes is a fifth spacing. The arrangement density of the first through-holes is greater than the arrangement density of the third through-holes, and the arrangement density of the third through-holes is greater than the arrangement density of the second through-holes. The first spacing is less than the fifth spacing, and the fifth spacing is less than the second spacing. Alternatively, the arrangement density of the first through-holes is less than the arrangement density of the third through-holes, and the arrangement density of the third through-holes is less than the arrangement density of the second through-holes. The first spacing is greater than the fifth spacing, and the fifth spacing is greater than the second spacing.

3. The photonic crystal filter according to claim 2, wherein, The first through hole, the second through hole, and the third through hole have the same planar shape. The planar dimension of the first through hole is smaller than that of the second through hole, and the planar dimension of the second through hole is smaller than that of the third through hole.

4. The photonic crystal filter according to any one of claims 1 to 3, wherein, The first through holes are arranged in a matrix, and the overall outer contour of the matrix of the first through holes is quadrilateral. The second through holes are located on the side of each side of the quadrilateral away from the center of the central region, and the second through holes surround the entire matrix of the first through holes.

5. The photonic crystal filter according to claim 4, wherein, The rectangular array formed by the first through hole is a square array, and the planar shape of the central region is a square. The outer perimeter region includes four side regions and four corner regions, and the four side regions and the four corner regions are all rectangular in shape. The long side of each of the four side regions that is closest to the central region is aligned with the four sides of the central region and has the same length. The four corner regions are located at the four corners of the central region in directions away from the center of the square, and the two adjacent sides of each of the four corner regions are aligned with the shorter sides of the two adjacent side regions and are of equal length.

6. The photonic crystal filter according to claim 5, wherein, The four side regions are rectangular regions formed by Na×Nb second through holes, and the four corner regions are square regions formed by Nb×Nb second through holes, where Na and Nb are both positive integers.

7. The photonic crystal filter according to any one of claims 1 to 3, further comprising an active layer and a first dielectric layer disposed between the active layer and the photonic crystal portion, wherein, The active layer is configured to emit light and serve as an optical gain medium.

8. The photonic crystal filter according to claim 7, further comprising a second dielectric layer disposed on the side of the photonic crystal portion away from the first dielectric layer, wherein, Each of the vias includes a first end and a second end opposite each other along the extension direction of its channel, the first end being connected to the first dielectric layer and the second end being connected to the second dielectric layer.

9. The photonic crystal filter according to claim 8, further comprising: n-type substrate; An n-type semiconductor heavily doped layer and an n-type semiconductor doped layer are sequentially disposed on the n-type substrate; A p-type semiconductor doped layer and a p-type semiconductor heavily doped layer are sequentially disposed on the side of the active layer away from the n-type substrate; A p-type electrode layer disposed on the side of the heavily doped p-type semiconductor layer away from the n-type substrate; as well as An n-type electrode layer is disposed on the side of the heavily doped n-type semiconductor layer away from the n-type substrate and spaced apart from the n-type semiconductor doped layer; The active layer is disposed on the side of the n-type semiconductor doped layer away from the n-type substrate; The heavily doped p-type semiconductor layer is configured as the second dielectric layer; The p-type semiconductor doped layer is configured as the photonic crystal portion and the first dielectric layer.

10. The photonic crystal filter according to claim 8, further comprising: n-type substrate; An n-type semiconductor heavily doped layer and an n-type semiconductor doped layer are sequentially disposed on the n-type substrate; A p-type semiconductor doped layer and a p-type semiconductor heavily doped layer are sequentially disposed on the side of the active layer away from the n-type substrate; A p-type electrode layer disposed on the side of the heavily doped p-type semiconductor layer away from the n-type substrate, and An n-type electrode layer is disposed on the side of the heavily doped n-type semiconductor layer away from the n-type substrate and spaced apart from the n-type semiconductor doped layer; The active layer is disposed on the side of the n-type semiconductor doped layer away from the n-type substrate; The heavily doped n-type semiconductor layer is configured as the second dielectric layer; The n-type semiconductor doped layer is configured as the photonic crystal portion and the first dielectric layer.

11. A method for fabricating a photonic crystal filter, comprising: Provide substrates; A first type of semiconductor doped thin film is formed on the substrate. A etching inhibitor is applied to the semiconductor doped layer thin film of the first type and pre-cured to form an etching inhibitor layer; The resist layer is nanoimprinted using an imprint template to transfer the pattern of the imprint template to the resist layer, and then cured to form a resist layer pattern. Using the resist layer pattern as a mask, a patterning process is performed on the first type of semiconductor doped layer thin film to form a photonic crystal layer, and then the resist layer pattern is removed; wherein, The photonic crystal layer includes a photonic crystal section, which includes a plurality of photonic crystal units arranged in an array. Each photonic crystal unit includes a plurality of vias arranged in an array. Each photonic crystal unit includes a central region and a peripheral region surrounding the central region. The plurality of vias includes a first via arranged in an array in the central region and a second via arranged in an array in the peripheral region. The central region includes Na×Na first through holes, where Na is a positive integer greater than or equal to 5; The number of second through holes on each side of the outer perimeter region is Na×Nb, where Nb is a positive integer greater than or equal to 1; The minimum distance between two adjacent first through holes is the first spacing Da, the minimum distance between two adjacent second through holes is the second spacing Db, and the minimum distance between the first through hole and the second through hole is the third spacing Dg, and satisfies Na*Da+Nb*Db+Dg≤10μm; The minimum distance between two adjacent photonic crystal units is the fourth spacing Nag, and the fourth spacing Nag is greater than or equal to 5 micrometers and less than or equal to 10 micrometers.

12. The preparation method according to claim 11, further comprising: An active layer thin film is formed on the substrate. A first dielectric layer thin film is formed between the active layer thin film and the photonic crystal layer; wherein... The active layer thin film is configured to emit light and serve as an optical gain medium.

13. The preparation method according to claim 12, further comprising: A second dielectric layer film is formed on the side of the photonic crystal layer away from the first dielectric layer film, wherein the material of the second dielectric layer film is a heavily doped material of a first type of semiconductor, and each of the vias includes a first end and a second end opposite to each other along the extension direction of its channel, the first end being connected to the first dielectric layer film and the second end being connected to the second dielectric layer film.

14. A spectral detection system, comprising: A semi-transparent and semi-reflective mirror, an objective lens, an imaging structure, a 4f optical system, and a photonic crystal filter according to any one of claims 1 to 10.

15. A spectral detection method, comprising: Forming spectra with distinct characteristics; The spectrum to be measured is input into the spectral detection system of claim 14 to distinguish the spectra with different characteristics.

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