An optical filter having comb-filtering characteristics and a method of manufacture

Abstract

This invention discloses an optical filter with comb-like filtering characteristics and its fabrication method, belonging to the field of optical technology. The method is carried out in the following apparatus: the apparatus includes a phase mask and a volume grating substrate. The volume grating substrate is photothermal refractive glass with Cr strips coated on its surface. The phase mask and the volume grating substrate are positioned using a cross alignment system, with the side of the volume grating substrate coated with Cr strips facing the phase mask. The method includes: passing a beam of light output from an ultraviolet light source sequentially through a beam expander and a collimator, and then perpendicularly incident on the phase mask. The interference fringes formed by the phase mask illuminate the volume grating substrate. The blocked area forms a filtering region, and the unblocked area forms a grating region. Finally, a thermosetting treatment is performed to obtain an optical filter with comb-like filtering characteristics. Using this method, a high-precision optical filter with comb-like filtering characteristics, controllable center wavelength, bandwidth, and filtering effect can be fabricated.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, specifically relating to an optical filter with comb-like filtering characteristics and its fabrication method. Background Technology

[0002] Optical filters are core components in wavelength division multiplexing systems, spectral analysis, sensing, and laser technologies. Depending on the application requirements, optical filters need to possess diverse spectral response characteristics.

[0003] However, traditional optical filters have the following technical problems: (1) Traditional optical filters have relatively simple functions. When faced with application scenarios that require composite filtering characteristics, they can only be achieved through cascading, which makes the system complex and increases insertion loss and product cost. For example, short-pass filters are limited by the physical limits of film materials and multilayer interference, and their bandwidth is usually greater than 0.5nm, and a single device can only have one bandwidth.

[0004] (2) The design and iteration costs of traditional filters are high and the design flexibility is poor. For example, if an optical frequency comb is to maintain phase locking between the comb teeth, the entire system must strictly meet the equal mode spacing condition. Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an optical filter with comb-like filtering characteristics and a method for its fabrication, aiming to solve the problem that the filtering wavelength, spacing, bandwidth and filtering effect are difficult to control precisely during the manufacturing process of existing optical filters with comb-like filtering structures.

[0006] The technical solution of the present invention is as follows: A first aspect of the present invention provides a method for fabricating an optical filter having comb-like filtering characteristics, wherein the method is carried out in the following apparatus; The device includes an ultraviolet light source, a beam expander, a collimating lens, a phase mask, and a volume grating substrate (PTR substrate) arranged sequentially along the optical path. The volume grating substrate is photothermal refractive glass, and the surface of the volume grating substrate is coated with Cr strips. The phase mask and the volume grating substrate are positioned by a cross alignment mark system, and the side of the volume grating substrate coated with Cr strips faces the phase mask. The method includes the following steps: The beam output from the ultraviolet light source is sequentially passed through a beam expander and a collimator before being incident perpendicularly onto the phase mask. The phase mask splits the light beam and generates interference, forming periodic interference fringes; The interference fringes illuminate the surface of the bulk grating substrate. The blocked area forms a filter forming area, and the unblocked area forms a grating forming area. Finally, after thermosetting, an optical filter with comb-like filtering characteristics is obtained.

[0007] Optionally, in the method for fabricating the optical filter with comb-like filtering characteristics, a Cr strip is deposited on a PTR substrate using a photolithography-lift-off process.

[0008] Optionally, the method for fabricating the optical filter with comb-like filtering characteristics, wherein the step of depositing the Cr baffle onto the PTR substrate using a lift-off process specifically includes: Spin-coating photoresist onto a bulk grating substrate; A 375nm ultraviolet light source is used for exposure and development to remove the photoresist in the patterned area where Cr strips need to be deposited, exposing the bulk grating substrate. Cr is deposited on the entire volume grating substrate; The photoresist was dissolved in a solvent to obtain Cr strips deposited on the bulk grating substrate.

[0009] Optionally, in the method for preparing the optical filter with comb-like filtering characteristics, the type, center wavelength, bandwidth, and spacing uniformity of the optical filter are adjusted by controlling the number, position, width, and spacing of the Cr baffles.

[0010] Optionally, in the method for preparing the optical filter with comb-like filtering characteristics, the wavelength of the light beam output by the ultraviolet light source is 300-335nm.

[0011] Optionally, in the method for fabricating the optical filter with comb-like filtering characteristics, cross marks are made on the phase mask and the volume grating substrate respectively to achieve the positioning of the phase mask and the volume grating substrate.

[0012] Optionally, in the method for preparing the optical filter with comb-like filtering characteristics, the thermosetting process involves: first nucleation treatment at 400-450℃ for 1-2 hours, followed by crystallization treatment at 470-550℃ for 1-2 hours.

[0013] Optionally, in the method for fabricating the optical filter with comb-like filtering characteristics, the bulk grating substrate is positioned... center wavelength The position of the volume grating substrate grating period Effective refractive index of bulk grating substrate Decide: .

[0014] Optionally, in the method for fabricating the optical filter with comb-like filtering characteristics, the filtering bandwidth is... Determined by the width of the Cr baffle. :

[0015] in, The chirp coefficients are the chirp coefficients of the linear chirped phase mask template; The effective refractive index of the bulk grating substrate.

[0016] In a second aspect, the present invention provides an optical filter having comb-like filtering characteristics, wherein the filter is prepared by the method for preparing an optical filter having comb-like filtering characteristics as described in the present invention.

[0017] Beneficial Effects: This invention provides a method for fabricating an optical filter with comb-like filtering characteristics. The method is carried out in the following apparatus: the apparatus includes an ultraviolet light source, a beam expander, a collimating lens, a phase mask, and a volume grating substrate arranged sequentially along the optical path; wherein, the volume grating substrate is photothermal refractive glass, and the surface of the volume grating substrate is coated with Cr strips; the phase mask and the volume grating substrate are positioned by a cross alignment mark system; the method includes the following steps: the light beam output from the ultraviolet light source is sequentially passed through the beam expander and collimating lens, and then perpendicularly incident on the phase mask; the phase mask splits the light beam and generates interference, forming interference fringes; the interference fringes irradiate the surface of the volume grating substrate, the blocked area forms a filtering formation area, and the unblocked area forms a grating formation area; finally, after thermosetting, an optical filter with comb-like filtering characteristics is obtained. This invention involves depositing Cr baffles onto a substrate and using an exposure process that blocks interference fringes with the Cr baffles. A cross alignment marking system is then used to achieve precise positioning of the phase mask and the substrate, thereby completing the fabrication of a high-precision optical filter with comb-like filtering characteristics, where the center wavelength, bandwidth, and filtering effect are all controllable.

[0018] The method of the present invention also has the following technical advantages: (1) The design has high flexibility and low design iteration cost; (2) Good repeatability in batch manufacturing; (3) High design precision; ultra-narrow bandwidth filtering can be achieved simply by adjusting the width of the Cr baffle. (4) It is an all-solid-state passive device with a simple structure and no need to cascade multiple independent devices. Multiple ultra-narrow bandwidth filters or complex systems with both narrowband and wideband filters can be implemented on the same device at the same time, and the bandwidth of each wavelength can be designed completely independently, which greatly reduces the insertion loss. Attached Figure Description Figure 1 This is a schematic diagram of the device structure for preparing an optical filter with comb-like filtering characteristics according to the present invention; wherein, 1 is an ultraviolet light source, 2 is a beam expander, 3 is a collimating lens, 4 is a phase mask, and 5 is a volume grating substrate.

[0019] Figure 2 This is a schematic diagram of a phase mask and a PTR substrate containing crosshairs; where 4 is the phase mask; 6 is a crosshair, engraved on the phase mask and PTR substrate to mark the diffraction spectrum boundary and the position of the filtering wavelength; 7 is the coating surface of the phase mask, through which the light beam forms interference fringes; and 5 is the PTR substrate.

[0020] Figure 3 A schematic diagram of a PTR substrate after Cr strips have been deposited on it; where 5 is the PTR substrate; 8 is the Cr strip deposited on the surface of the PTR substrate, the position and width of which determine the actual filtering wavelength and bandwidth.

[0021] Figure 4 This is a schematic diagram of the diffraction spectrum. Detailed Implementation

[0022] This invention provides an optical filter with comb-like filtering characteristics and its fabrication method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] To address the problem of difficulty in precisely controlling the filtering wavelength, spacing, bandwidth, and filtering effect during the manufacturing process of existing comb-shaped optical filters, this invention provides an optical filter and its fabrication method that achieves high precision, high repeatability, and suitability for mass production by blocking interference fringes.

[0024] Specifically, an embodiment of the present invention provides a method for fabricating an optical filter with comb-like filtering characteristics, wherein the method is performed in the following apparatus; like Figure 1 As shown, the device includes an ultraviolet light source 1, a beam expander 2, a collimating lens 3, a phase mask 4, and a volume grating substrate 5 arranged sequentially along the optical path direction; Among them, such as Figure 2-3 As shown, the volume grating substrate (i.e., PTR substrate) 5 is photothermal refractive glass, and the surface of the volume grating substrate 5 is coated with Cr (chromium) baffles 8. The phase mask 4 and the volume grating substrate 5 are positioned by a cross alignment mark system, and the side of the volume grating substrate 5 coated with Cr baffles 8 faces the phase mask 4. 7 is the coating surface of the phase mask, and the light beam forms interference fringes through this surface. The method includes the following steps: The beam output from the ultraviolet light source is sequentially passed through a beam expander and a collimator before being incident perpendicularly onto the phase mask. The phase mask splits the light beam and generates interference, forming interference fringes; The interference fringes illuminate the surface of the bulk grating substrate. The blocked area forms a filter forming area, and the unblocked area forms a grating forming area. Finally, after thermosetting, an optical filter with comb-like filtering characteristics is obtained.

[0025] This embodiment employs a lift-off process to deposit Cr baffles onto a PTR substrate. By using the Cr baffles to block interference fringes during exposure, and utilizing a cross-shaped alignment system, precise positioning of the phase mask and the PTR substrate is achieved. This allows for the fabrication of a high-precision optical filter with comb-like filtering characteristics, where the center wavelength, bandwidth, and filtering effect are all controllable. This design eliminates the need for cascading multiple filters, enabling independent multi-wavelength filtering on a single device, significantly reducing insertion loss. Furthermore, this design offers high flexibility, low iteration costs, good repeatability in mass production, and high design precision; ultra-narrow bandwidth filtering can be achieved simply by adjusting the width of the Cr baffles.

[0026] In this embodiment, Cr has strong adhesion to the PTR substrate and is easy to obtain a fine structure with steep sidewalls.

[0027] In this embodiment, the PTR substrate generates refractive index modulation after ultraviolet exposure. The area blocked by the Cr strip maintains a uniform refractive index due to the lack of exposure, forming a filter formation area. The unblocked area forms a periodic grating structure, and the two together constitute a comb-shaped filter spectrum.

[0028] The apparatus used to prepare an optical filter with comb-like filtering characteristics in this embodiment will now be described in detail.

[0029] The core structure of the device in this embodiment includes the following parts: Photosensitive substrate: A PTR substrate coated with Cr baffles. The light information actually written onto the substrate is divided into a grating formation region (the unblocked area where interference fringes can pass through normally, forming a Bragg grating on the substrate) and a filter formation region (the area covered by opaque baffles, where interference fringes are blocked, forming gaps without a grating). The number, position, width, and spacing of the Cr baffles are designed to precisely control four filtering characteristics: the type of filter (bandpass / comb), the center wavelength of the filter, the bandwidth of the filter, and the uniformity of the filter spacing (equal / non-uniform spacing). For example, three Cr baffles can correspond to three filtering wavelengths (e.g., 1028, 1030, 1032 nm), with the spacing precisely controlled by the position of the Cr baffles. A 0.1 nm filter bandwidth corresponds to a 0.63 mm width, and a 0.2 nm filter bandwidth corresponds to a 1.26 mm width.

[0030] In other words, the number, position, and width of the Cr baffles can be adjusted according to the actual required number, position, and bandwidth of the filtering wavelengths. Only Cr baffle masks that meet the parameter requirements need to be fabricated, without the need to re-customize the entire phase mask. When changing the filtering parameters, only the settings of the corresponding Cr baffles need to be adjusted to complete the solution iteration, which greatly reduces the cost and cycle of design adjustment and can flexibly adapt to the comb filtering requirements in different scenarios.

[0031] Phase mask: Located in front of the PTR substrate coated with Cr baffles, used to generate interference fringes; the side of the phase mask facing the PTR substrate has a coated surface, through which the light beam forms interference fringes; the phase mask can be a linear chirped phase mask, etc.

[0032] Cross alignment mark system: such as Figure 2 As shown, cross marks (such as those made on the phase mask 4 and the PTR substrate 5 coated with Cr stripes) are made respectively. Figure 2 The crosshair 6 in the middle is used to achieve precise positioning of the phase mask template and the Cr stop bar.

[0033] Specifically, crosshairs are used to mark the diffraction spectrum boundary and the position of the filtering wavelength. The crosshairs marking the position of the filtering wavelength correspond one-to-one with the Cr bars. The diffraction spectrum boundary helps to confirm whether the positioning is reasonable, and it corresponds to the left and right boundary positions of the bulk grating substrate.

[0034] Ultraviolet light source: The wavelength of the output beam is 300-335nm, such as 325nm.

[0035] Compared to the solution of customizing a whole special phase mask, this embodiment only requires designing Cr baffles on the PTR substrate that matches the existing phase mask as needed. This allows for flexible adjustment of the final output filtering parameters. Whether adjusting the filtering center wavelength, changing the filtering bandwidth, or adjusting the wavelength interval, it is not necessary to re-fabricate the entire phase mask. Only the design parameters of the Cr baffles need to be modified, which greatly shortens the parameter adjustment cycle and significantly reduces the cost of design iteration. It can quickly respond to the personalized parameter requirements of comb filtering for different application scenarios.

[0036] The principle of preparing the optical filter with comb filtering characteristics in this embodiment will be introduced below.

[0037] For an ideal linearly chirped phase mask, its period along the length The change can be represented as:

[0038] Phase mask start end The cycle; Chirp coefficient , indicating each The periodic change in length; : Position coordinates along the length of the phase mask template.

[0039] When ultraviolet light shines perpendicularly onto the location At that time, according to the grating equation (first-order diffraction), the diffraction angle of the ±1st order light emitted from that position is... satisfy:

[0040] The ultraviolet light wavelength is selected as 325nm. When the ultraviolet light wavelength remains constant, the diffraction angle is... along with It decreases as it increases.

[0041] +1 level light and When first-order light interferes behind a phase mask, the resulting interference fringes are periodic. It is half the period of the phase mask. A PTR substrate coated with Cr baffles is placed behind the phase mask and will precisely replicate the period of this interference fringe at the PTR substrate position. The written grating period This is equivalent to the period of the interference fringes:

[0042] This location writes the center wavelength of the substrate. The Bragg condition is satisfied by the grating period at that position. and effective refractive index Decide:

[0043] Right now

[0044] In summary, the filtered wavelength and filtering bandwidth can be calculated by examining the position of the fringes blocked by the Cr baffle on the phase mask. This depends on the width of the Cr retaining strip. :

[0045] in, The chirp coefficients are the chirp coefficients of the linear chirped phase mask template; The effective refractive index of the bulk grating substrate.

[0046] The fabrication method of the optical filter with comb filtering characteristics in this embodiment will be described in detail below.

[0047] Calculate the specific position of the Cr barrier according to the design scheme, and use a 375nm light source to deposit the Cr barrier onto the surface of the PTR substrate using a lift-off process; of course, it is not limited to a 375nm light source, any ultraviolet etching light source that does not react with the PTR substrate can be used. Exposure is performed using a 300-335nm (e.g., 325nm) light source to write the information onto the PTR substrate; An optical filter with comb-like filtering characteristics was prepared by thermosetting a PTR substrate.

[0048] In this embodiment, the entire preparation process only requires adjusting the position and width parameters of the Cr baffle according to the target filtering requirements. There is no need to redesign the entire phase mask template. After adjusting the parameters, the preparation of the new sample can be completed quickly. There is no need to repeatedly open molds and customize new mask templates, which greatly reduces the cost of design and adjustment. At the same time, it can flexibly adapt to the comb filtering requirements in different scenarios.

[0049] In one embodiment, the step of depositing the Cr barrier onto the surface of the PTR substrate using a 375nm light source and a lift-off process specifically includes: Photoresist coating: Spin-coating photoresist onto the PTR substrate; Photolithography: Using a 375nm ultraviolet light source for exposure and development, the photoresist in the patterned area where the chromium strip needs to be plated is removed, exposing the PTR substrate; Coating: Cr is deposited on the entire PTR glass substrate; Stripping: The photoresist is dissolved in a solvent, and the metal on top of it is stripped off, leaving only the Cr strips directly deposited on the PTR substrate.

[0050] This step-by-step processing allows for precise control of the position and size of the Cr baffle. During the processing, only the graphic parameters on the photomask need to be modified according to the position, spacing, and width requirements of the target comb filter channel to quickly obtain the required Cr baffle structure. There is no need to customize a completely new phase mask, which simplifies the parameter adjustment process, effectively reduces the cost of design adjustment, and can flexibly adapt to the comb filter requirements in different scenarios.

[0051] In one embodiment, the thermosetting process involves: first, nucleation treatment at 400-450℃ (e.g., 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, etc.) for 1-2 hours (e.g., 1 hour, 1.5 hours, 2 hours, etc.), followed by crystallization treatment at 470-550℃ (e.g., 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, etc.) for 1-2 hours (e.g., 1 hour, 1.5 hours, 2 hours, etc.).

[0052] By using segmented temperature-controlled thermosetting process, photosensitive materials can be stably formed with a uniform and dense crystal structure, ensuring the stability of light filtering characteristics. If the target filtering parameters are adjusted, only the graphic parameters need to be adjusted in the Cr strip preparation stage. The thermosetting process does not need to be modified as a whole, further reducing the cost of parameter adjustment and adapting to diverse design needs.

[0053] This invention provides an optical filter with comb-like filtering characteristics, which is prepared using the method described in this invention.

[0054] In this embodiment, the optical filter is an all-solid-state passive device with a simple structure, eliminating the need for cascading multiple independent devices. Multiple ultra-narrow bandwidth filters, or complex systems where narrowband and wideband filtering coexist, can be implemented simultaneously on a single device. Furthermore, the bandwidth of each wavelength can be designed completely independently, significantly reducing insertion loss. In addition, the optical filter design in this embodiment offers high flexibility and low design iteration costs; it boasts good repeatability in mass production; and it achieves high design precision, as ultra-narrow bandwidth filtering can be achieved simply by adjusting the width of the Cr stop bar.

[0055] The present invention will now be described in detail through specific embodiments.

[0056] In the following Examples 1-3, the chirp of the phase mask is 0.535 nm / cm, the center period of the phase mask is 691.77 nm, the length of the phase mask is 65 mm, and the effective refractive index of the PTR substrate is 1.488. Example 1: Single blocking strip - Filter wavelength selected is 1030nm, bandwidth designed to be 0.1nm.

[0057] Based on the 0.1nm bandwidth design requirement, according to the formula... The width of the Cr baffle should be 0.63mm. Based on the design requirements for a 1030nm filter wavelength, and according to the filter wavelength formula... The calculated period of the phase mask is 692.2043 nm, and the distance from the starting point (short period end) of the phase mask is approximately 36.57 mm. Its diffraction pattern is as follows: Figure 3 As shown.

[0058] Example 2: Three shielding strips - filter wavelengths of 1028, 1030, and 1032 nm are selected, and the bandwidth is designed to be 0.1 nm.

[0059] According to the design requirement of 0.1nm bandwidth, the width of the Cr strip is 0.63mm. The distances from the starting point of the phase mask (short period end) to the corresponding positions are approximately 24mm, 36.57mm, and 49.1mm respectively, depending on the design requirements of the filtering wavelength.

[0060] Example 3: Five shielding strips - the filter wavelengths are selected as 1026, 1027, 1028, 1032, and 1034 nm, and the bandwidth is designed as 0.1, 0.1, 0.1, 0.2, and 0.2 nm.

[0061] According to the bandwidth design requirements, the widths of the Cr baffles are 0.63, 0.63, 0.63, 1.26, and 1.26 mm respectively. The corresponding distances from the starting point of the phase mask (short period end) are approximately 11.44 mm, 17.72 mm, 24 mm, 49.1 mm, and 61.68 mm respectively, according to the design requirements of the filtering wavelength. As can be seen from the above, the entire design process only requires changing the width and placement of the shielding strip to adjust the filtering bandwidth and center wavelength. There is no need to re-prepare the phase mask template; only the design parameters of the Cr shielding strip need to be modified. This greatly shortens the parameter adjustment cycle and significantly reduces the cost of design iteration. It can quickly respond to the personalized parameter requirements of comb filtering for different application scenarios.

[0062] In summary, this invention provides an optical filter with comb-like filtering characteristics and its fabrication method. The method is carried out in the following apparatus: the apparatus includes an ultraviolet light source, a beam expander, a collimating lens, a phase mask, and a volume grating substrate arranged sequentially along the optical path; wherein, the volume grating substrate is photothermal refractive glass, and the surface of the volume grating substrate is coated with Cr strips; the phase mask and the volume grating substrate are positioned by a cross alignment mark system; the method includes the following steps: the light beam output from the ultraviolet light source is sequentially passed through the beam expander and collimating lens, and then perpendicularly incident on the phase mask; the phase mask splits the light beam and generates interference, forming interference fringes; the interference fringes irradiate the surface of the volume grating substrate, the blocked area forms a filtering formation area, and the unblocked area forms a grating formation area; finally, the filter with comb-like filtering characteristics is obtained by thermosetting. This invention involves depositing Cr baffles onto a substrate and using an exposure process that blocks interference fringes with the Cr baffles. A cross alignment marking system is then used to achieve precise positioning of the phase mask and the substrate, thereby completing the fabrication of a high-precision optical filter with comb-like filtering characteristics, where the center wavelength, bandwidth, and filtering effect are all controllable.

[0063] Compared to traditional custom phase mask solutions, this invention allows for flexible adjustment of the final output filtering parameters by designing Cr baffles on the PTR substrate that matches the existing phase mask as needed. Whether adjusting the filter center wavelength, changing the filter bandwidth, or adjusting the wavelength interval, it is not necessary to re-fabricate the entire phase mask. Only the design parameters of the Cr baffles need to be modified, which greatly shortens the parameter adjustment cycle and significantly reduces the cost of design iteration. It can quickly respond to the personalized parameter requirements of comb filtering in different application scenarios.

[0064] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for fabricating an optical filter with comb-like filtering characteristics, characterized in that, The method is performed in the following apparatus; The device includes an ultraviolet light source, a beam expander, a collimating lens, a phase mask, and a volume grating substrate arranged sequentially along the optical path. The volume grating substrate is photothermal refractive glass, and the surface of the volume grating substrate is coated with Cr strips. The phase mask and the volume grating substrate are positioned by a cross alignment mark system, and the side of the volume grating substrate coated with Cr strips faces the phase mask. The method includes the following steps: The beam output from the ultraviolet light source is sequentially passed through a beam expander and a collimator before being incident perpendicularly onto the phase mask. The phase mask splits the light beam and generates interference, forming interference fringes; The interference fringes illuminate the surface of the bulk grating substrate. The blocked area forms a filter forming area, and the unblocked area forms a grating forming area. Finally, after thermosetting, an optical filter with comb-like filtering characteristics is obtained.

2. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, The Cr strips were deposited onto the bulk grating substrate using a photolithography-lift process.

3. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 2, characterized in that, The step of depositing Cr baffles onto the bulk grating substrate using a photolithography-lifting process specifically includes: Spin-coating photoresist onto a bulk grating substrate; Using an ultraviolet light source with a wavelength ≥345nm for exposure and development, the photoresist in the patterned area to be plated with Cr strips is removed, exposing the bulk grating substrate. Cr is deposited on the entire volume grating substrate; The photoresist was dissolved in a solvent to obtain Cr strips deposited on the bulk grating substrate.

4. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, By controlling the number, position, width, and spacing of the Cr baffles, the type, center wavelength, bandwidth, and spacing uniformity of the optical filter can be adjusted.

5. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, The wavelength of the light beam output by the ultraviolet light source is 300-335nm.

6. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, Cross marks are made on the phase mask and the volume grating substrate respectively to achieve the positioning of the phase mask and the volume grating substrate.

7. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, The thermosetting process involves first nucleating at 400-450℃ for 1-2 hours, and then crystallizing at 470-550℃ for 1-2 hours.

8. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, At the bulk grating substrate location center wavelength The position of the volume grating substrate grating period Effective refractive index of bulk grating substrate Decide: 。 9. The method for fabricating an optical filter with comb-like filtering characteristics according to claim 1, characterized in that, Filter bandwidth Determined by the width of the Cr baffle. : in, The chirp coefficients are the chirp coefficients of the linear chirped phase mask template; The effective refractive index of the bulk grating substrate.

10. An optical filter with comb-like filtering characteristics, characterized in that, The optical filter with comb-like filtering characteristics as described in any one of claims 1-9 is prepared using the preparation method of the optical filter with comb-like filtering characteristics.

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