An atomic-level composite film structure for modifying grating groove type and a preparation process thereof

Abstract

This invention discloses an atomic-level composite film structure for modifying grating grooves and its fabrication process, relating to the field of optical thin film technology. The atomic-level composite film structure for modifying grating grooves sequentially comprises a grating substrate, a refractive index matching layer, and a diffraction enhancement layer; wherein the surface of the grating substrate has a periodically distributed groove structure; the refractive index matching layer is a nanolayer stack composed of high-refractive-index sublayers and low-refractive-index sublayers or a single-component film layer; the diffraction enhancement layer is composed of a single high-refractive-index film. The atomic-level composite film structure for modifying grating grooves of this invention achieves surface modification and reliability improvement of deep-groove grating structures: through high-precision optical matching between the refractive index matching layer and the substrate material, etching defects are effectively repaired, the groove structure is modified, and diffraction performance is improved, significantly enhancing the long-term stability of the device.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to an atomic-level composite film structure with modified grating grooves and its preparation process. Background Technology

[0002] Gratings, as key high-dispersion diffractive optical elements, play an irreplaceable role in advanced optical systems such as spectral analysis, pulse compression, laser wavelength selection, and astronomical observation. An immersion grating is a high-performance diffractive optical element in which light is incident from within the grating substrate onto the grating surface. Compared to traditional gratings, immersion gratings achieve significantly improved optical performance with increased refractive index of the incident medium, resulting in higher resolution, a more compact structure, higher diffraction efficiency, and lower polarization effects, which is beneficial for the miniaturization of spectrometers.

[0003] High-performance immersion gratings typically require deep-groove grating structures. However, direct patterning etching struggles to create deep grooves within sub-micron periods, making precise control of the groove width impossible and easily leading to physical defects within the grating grooves, causing scattering enhancement issues. To obtain an ideal groove structure, thin-film deposition is generally required for precise modification of the groove structure. However, achieving high-quality surface modification on deep-groove structures is extremely challenging, requiring the simultaneous fulfillment of several stringent requirements: forming an optically ideal interface with the grating substrate material; possessing excellent structural conformability to achieve consistent coverage of the fine structures within the deep groove; and the film itself must exhibit high density, low surface roughness, low internal stress, and long-term stability to ensure reliable device performance in practical applications.

[0004] Traditional thin-film deposition methods struggle to quantitatively control the refractive index of the film, failing to achieve a match with the substrate's refractive index. This refractive index difference introduces more scattering interfaces during the modification of grooved structures. Furthermore, for deep-groove grating structures, traditional physical vapor deposition is prone to problems such as incomplete filling, porosity formation, stress-induced cracking, and cumulative surface roughness with increasing film thickness, making it difficult to achieve precise control and conformal modification of deep-groove structures. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an atomic-level composite film structure for modifying grating grooves and its fabrication process. This process can precisely modify the structure of deep groove gratings, reduce scattering from rough surfaces, and improve diffraction efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An atomic-level composite film structure for modifying grating grooves comprises, in sequence, a grating substrate, a refractive index matching layer, and a diffraction enhancement layer; wherein the surface of the grating substrate has a periodically distributed groove structure; the refractive index matching layer is a nanolayer stack composed of high refractive index sublayers and low refractive index sublayers or a single-component film layer; and the diffraction enhancement layer is composed of a single-layer high refractive index film.

[0008] Wherein, the equivalent refractive index n of the nanolayer is eff The thickness proportion f of the high-refractive-index sublayer satisfies the following relationship:

[0009] ;

[0010] Where, n eff n is the equivalent refractive index of the refractive index matching layer, f is the thickness percentage of the high refractive index sublayer, and n is the thickness percentage of the high refractive index sublayer. H n represents the refractive index value of the high-refractive-index sublayer. L This represents the refractive index value of the low-refractive-index sublayer.

[0011] The relative deviation between the equivalent refractive index of the refractive index matching layer and the refractive index of the grating substrate material is less than 5%; the periodic optical thickness of the nanolayer stack of the refractive index matching layer is less than one-tenth of the reference wavelength.

[0012] The diffraction enhancement layer contains multiple amorphous sublayers with a thickness of 0.2 to 4.0 nm that are uniformly embedded inside.

[0013] The modified grating groove-type atomic-level composite film structure further includes an environmental medium that fills the groove structure; the environmental medium is air or a highly reflective metal.

[0014] Wherein, when the light emission mode of the diffracted light required by the grating is transmission type, the ambient medium is air; when the light emission mode of the diffracted light required by the grating is reflection type, the ambient medium is a highly reflective metal; the highly reflective metal is gold, silver or aluminum.

[0015] When the environmental medium is a highly reflective metal, a metal film protective film is covered on the highly reflective metal, and the metal film protective film is a double-layer film of Al2O3 and SiO2.

[0016] The above-mentioned fabrication process of the modified grating groove atomic-level composite film structure includes the following steps:

[0017] S1: A rectangular groove with period d, depth h, and width d2 is etched on the grating substrate, and the cross section of the same batch of grating reference sheet is imaged by scanning electron microscopy. The precise structural parameters, including period d, depth h, and width d2, are determined using the electron microscope chart ruler.

[0018] S2: A thickness of [thickness value missing] is fabricated using plasma-assisted atomic layer deposition at a temperature of 60~150℃. The refractive index matching layer causes the groove width to change from d2 to d1; the refractive index matching layer is a single-component film layer or a nanolayer composed of a high-refractive-index sublayer and a low-refractive-index sublayer; the equivalent refractive index n of the nanolayer is... eff The thickness proportion f of the high-refractive-index sublayer satisfies the following relationship:

[0019] ; where n eff n is the equivalent refractive index of the refractive index matching layer, f is the thickness percentage of the high refractive index sublayer, and n is the thickness percentage of the high refractive index sublayer. H n represents the refractive index value of the high-refractive-index sublayer. L The refractive index value of the low-refractive-index sublayer;

[0020] S3: A diffraction enhancement layer of thickness t is fabricated using plasma-assisted atomic layer deposition.

[0021] When the diffracted light required for the grating is emitted by reflection, the fabrication process also includes the following steps:

[0022] S4: A high-reflectivity metal film is deposited using a room-temperature multi-angle directional evaporation method, and the high-reflectivity metal film fills the grooves on the grating surface.

[0023] The preparation process also includes a step of depositing a metal protective film, which is achieved by electron beam evaporation deposition of the metal protective film.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The atomic-level composite film structure of the modified grating groove of the present invention realizes the surface modification and reliability improvement of the deep groove grating structure: through the high-precision optical matching between the refractive index matching layer and the substrate material, the etching defects are effectively repaired, the groove structure is modified and the diffraction performance is improved, and the long-term stability of the device is significantly improved.

[0026] (2) The atomic-level composite film structure of the modified grating groove type of the present invention reduces scattering and improves diffraction efficiency: the diffraction enhancement layer suppresses the increase of roughness between grains and the surface by inserting amorphous sublayers, greatly reduces light scattering, and enhances the diffraction efficiency of the target band through film system optimization.

[0027] (3) The preparation process of the modified grating groove atomic-level composite film structure of the present invention realizes high-quality conformal deposition of high aspect ratio structure at low temperature: the low temperature plasma-assisted atomic layer deposition process can realize uniform, dense and low-stress film deposition on temperature sensitive substrate, ensuring the film-substrate bonding force and overall performance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the modified grating groove type atomic-level composite film structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure and operation of the 800 nm wavelength transmission immersion grating prepared in Example 1;

[0030] Figure 3 The simulated diffraction spectrum of the transmission immersion grating prepared in Example 1;

[0031] Figure 4 The spectrum of simulated diffraction performance of the immersion grating prepared for Comparative Example 1;

[0032] Figure 5 A schematic diagram of the structure and operation of the 2300 nm wavelength reflective diffraction immersion grating prepared in Example 2;

[0033] Figure 6 This is a design structural diagram of the reflective immersion grating in Example 2, wherein... Figure 6 (a) is a schematic diagram of the structure of a reflection immersion grating with a diffraction enhancement layer. Figure 6 (b) is a schematic diagram of the structure of a reflective immersion grating without a diffraction enhancement layer;

[0034] Figure 7 The simulated diffraction performance spectrum of the reflective immersion grating with a diffraction enhancement layer prepared in Example 2;

[0035] Figure 8 The simulated diffraction performance spectrum of the reflection immersion grating without diffraction enhancement layer prepared in Example 2;

[0036] Figure 9 The simulated diffraction spectrum of the transmission immersion grating prepared in Example 3.

[0037] The reference numerals in the attached figures are as follows: 1. Grating substrate; 2. Refractive index matching layer; 3. Diffraction enhancement layer; 4. Ambient medium; 5. Incident light; 6. -1st order transmitted diffracted light; 7. 0th order reflected diffracted light; 8. -1st order reflected diffracted light. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] See Figure 1The present invention provides an atomic-level composite film structure for modifying grating grooves, which sequentially includes a grating substrate 1, a refractive index matching layer 2, and a diffraction enhancement layer 3; wherein the surface of the grating substrate 1 has a periodically distributed groove structure; the refractive index matching layer 2 is a nano-stack composed of a high refractive index sublayer and a low refractive index sublayer or a single-component film layer; the diffraction enhancement layer 3 is composed of a single-layer high refractive index film.

[0040] The material of the grating substrate 1 is transparent to the working wavelength band and can be fused silica, optical glass, sapphire or polymer.

[0041] Specifically, the grating period of the grating substrate 1 is d, the groove width of the groove structure is d2, and the groove depth of the groove structure is h.

[0042] For etching grating substrate 1, especially high aspect ratio gratings, the actual groove width on the etched grating surface always deviates from the theoretical design to some extent, resulting in etching damage. Utilizing the replicability of atomic layer deposition to prepare a refractive index matching layer 2 can repair the grating structure to near the designed structure, reducing the groove width from d2 to d1 while maintaining the groove depth. That is, the thickness of the refractive index matching layer 2 is... .

[0043] The refractive index matching layer 2 can be made of a material whose relative deviation from the equivalent refractive index of the grating substrate 1 is less than 5%.

[0044] Preferably, this invention combines high and low refractive index sublayers of a specific thickness ratio in a nano-stacked manner (i.e., the thickness of the refractive index matching layer 2 is the sum of the thicknesses of the high and low refractive index sublayers), and precisely controls the overall equivalent refractive index based on the equivalent medium theory to achieve a high degree of matching with the refractive index of the grating substrate material. The design concept of this invention aims to repair etching defects and adjust the grating linewidth (groove width) to conform to the theoretical design structure by depositing the refractive index matching layer 2, thereby improving the diffraction performance and reliability of the grating and laying the foundation for subsequent optical diffraction enhancement.

[0045] Specifically, the equivalent refractive index n of the nanolayers eff The thickness proportion f of the high-refractive-index sublayer satisfies the following relationship:

[0046] ;

[0047] Where n eff Let f be the equivalent refractive index of the refractive index matching layer 2, f be the thickness percentage of the high refractive index sublayer, and n be the refractive index of the layer. H n represents the refractive index value of the high-refractive-index sublayer. L This represents the refractive index value of the low-refractive-index sublayer.

[0048] Specifically, the equivalent refractive index of the refractive index matching layer 2 can be obtained based on the refractive index of the grating substrate material, and the refractive index value n of the selected high refractive index sublayer can be used as the basis for this determination. H and the refractive index value n of the low refractive index sublayer L The thickness percentage f of the high refractive index sublayer can be calculated.

[0049] The relative deviation between the equivalent refractive index of the refractive index matching layer 2 and the refractive index of the grating substrate material is less than 5%.

[0050] Preferably, the periodic optical thickness of the nanolayer of the refractive index matching layer 2 is less than one-tenth of the reference wavelength.

[0051] To further enhance the diffraction efficiency of the grating, this invention deposits a diffraction enhancement layer 3 of thickness t on the surface of the processed and repaired grating structure. The diffraction enhancement layer 3 is composed of a high-refractive-index material, and its design optimization aims to improve the optical efficiency at the target wavelength and diffraction order by depositing a suitable high-refractive-index composite film. Since high-refractive-index materials (such as TiO2, HfO2, ZrO2, ZnO, and Nb2O5) typically exhibit high-temperature crystallization, atomically thin low-refractive-index amorphous sublayers (such as Al2O3 and SiO2) are periodically inserted into the high-refractive-index film. These inserted layers effectively suppress grain growth and roughness accumulation of the high-refractive-index material during deposition, thereby obtaining an ultra-smooth surface to reduce light scattering. Specifically, multiple amorphous sublayers with thicknesses of 0.2–4.0 nm are uniformly embedded within the diffraction enhancement layer 3. The thickness t of the diffraction enhancement layer 3 is optimized by grating design software based on the target diffraction efficiency.

[0052] Preferably, the modified grating groove-type atomic-level composite film structure further includes an environmental medium 4, which is air or a highly reflective metal.

[0053] Specifically, when the required diffracted light exits in a transmission manner, the ambient medium 4 is air; when the required diffracted light exits in a reflection manner, the ambient medium 4 is a highly reflective metal. That is, the transmitted diffracted light enters the ambient medium 4, and the reflected diffracted light enters the grating substrate 1.

[0054] Preferably, the highly reflective metal is gold, silver, or aluminum.

[0055] Furthermore, the thin film deposition in the fabrication process of this invention employs a low-temperature plasma-assisted atomic layer deposition (ALD) method, with a deposition temperature of 60-150°C. This method minimizes high-temperature damage to the grating and facilitates anti-fouling film application to non-coated surfaces. The highly reactive plasma ensures sufficient precursor reaction, and the plasma impact on the thin film surface increases the migration kinetic energy of surface atoms, ensuring dense film growth and helping to reduce internal stress and improve adhesion. This process is particularly suitable for conformally depositing uniform, low-stress composite films on high aspect ratio grooved surfaces, thereby improving the overall performance and reliability of the grating.

[0056] The plasma is oxygen, argon, or a mixture thereof.

[0057] Example 1:

[0058] To address the demands for miniaturization, high resolution, and high diffraction efficiency in high-performance spectrometers, this embodiment provides a transmission-type immersion grating structure, the structure of which is as follows: Figure 2 As shown, the transmissive immersion grating structure consists of a grating substrate 1, a refractive index matching layer 2, a diffraction enhancement layer 3, and an ambient medium 4. Its operation is as follows: incident light 5 enters from inside the grating substrate 1; -1st order transmissive diffracted light 6 exits into the ambient medium 4 (air); and 0th order reflected diffracted light 7 and -1st order reflected diffracted light 8 are absorbed by the light-absorbing coating built into the grating or spectrometer.

[0059] In this embodiment, the design wavelength is selected as 800 nm. The transmission immersion grating structure of this embodiment can be used as the core grating element of the 780 nm Raman spectrometer. The incident angle is 49° and the grating period is d=400 nm.

[0060] The fabrication process of the transmissive immersion grating structure in this embodiment is as follows:

[0061] (1) The grating substrate 1 is made of K9 glass (n=1.51). A rectangular groove with a depth h=860 nm and a width d2 greater than 320 nm is etched on it using a photoresist mask + ion beam etching process. The cross-section of the grating reference sheet with the same structure is imaged by scanning electron microscopy to determine the precise structural parameters: d=400 nm; h=860 nm; d2=325 nm.

[0062] (2) Based on the structural parameters determined in (1), an oxygen plasma-assisted atomic layer deposition process is used to fabricate a nano-stack of Al2O3 (n=1.66) and SiO2 (n=1.46) in a reaction chamber at 120℃ with a thickness ratio of 1:3, forming a refractive index matching layer 2 with the same refractive index as the substrate. The total thickness of the nano-stack is 2.5nm, which makes the groove width d1=320nm.

[0063] (3) Further oxygen plasma-assisted atomic layer deposition was used to fabricate the diffraction enhancement layer 3. The thickness of the diffraction enhancement layer 3 was t=80 nm. It consisted of a 14.5 nm TiO2 main layer with 5 periods and a 1.5 nm Al2O3 intercalation. The Al2O3 intercalation effectively suppressed the grain size increase of TiO2 and maintained the flatness and smoothness of the diffraction enhancement layer 3.

[0064] The diffraction efficiency of the immersion grating prepared in this embodiment is as follows: Figure 3 As shown, from Figure 3 It can be seen that the diffraction efficiency at a wavelength of 800 nm can reach about 85%.

[0065] Comparative Example 1:

[0066] Comparative Example 1 uses a grating structure without diffraction enhancement layer 3, and optimizes the structural parameters (h, d1) to achieve the highest diffraction efficiency at the design wavelength of 800 nm. The grating period and incident angle are the same as in Example 1.

[0067] The diffraction efficiency of the immersion grating obtained in Comparative Example 1 is as follows: Figure 4 As shown, from Figure 4 It can be seen that the diffraction efficiency at a wavelength of 800 nm is only about 40%.

[0068] A comparison of the diffraction effects in Example 1 and Comparative Example 1 shows that the immersion grating modified with the atomic-level composite film structure provided by this invention exhibits higher diffraction efficiency and less polarization separation. Because the immersion grating has a smaller grating period structure, it has higher spectral resolution compared to ordinary flat gratings.

[0069] Example 2:

[0070] In greenhouse gas monitoring, atmospheric methane content is an important monitoring target, and it is commonly quantified using absorption spectra around a wavelength of 2300 nm. This embodiment provides a structure for a high-resolution, high-diffraction-efficiency reflective immersion grating with a reference wavelength of 2300 nm.

[0071] The structure of the present invention is as follows Figure 5 As shown, the reflective immersion grating structure consists of a grating substrate 1, a refractive index matching layer 2, a diffraction enhancement layer 3, and an ambient medium 4. The ambient medium 4 is metallic silver, which suppresses transmitted diffracted light. Its working process is as follows: incident light 5 enters from inside the grating substrate 1; the -1st order reflected diffracted light 8 serves as the target diffracted light; the 0th order reflected diffracted light 7 is absorbed by the grating light-absorbing coating; and the transmitted diffracted light is absorbed by the silver film.

[0072] In this embodiment, the reflective immersion grating structure is designed with a wavelength of 2300 nm, an incident angle of 45°, and a grating period of d=1000 nm.

[0073] The design concept of the reflective immersion grating structure in this embodiment is as follows:

[0074] The grating substrate 1 is made of fused silica material (n=1.43), the refractive index matching layer 2 is made of SiO2 thin film (n=1.43), and the diffraction enhancement layer 3 is a composite film with Nb2O5 main layer and SiO2 intercalation (n=2.1).

[0075] The fabrication process of the reflective immersion grating structure in this embodiment is as follows:

[0076] (1) The grating substrate 1 is made of fused silica material (n=1.43). A rectangular groove with a depth of h=900 nm and a width d2 greater than 739 nm is etched on it using a photoresist mask + ion beam etching process. The cross-section of the grating reference sheet is imaged by scanning electron microscopy to determine the precise structural parameters: d=1000 nm; h=900 nm; d2=741 nm.

[0077] (2) Based on the structural parameters determined in (1), an oxygen plasma-assisted atomic layer deposition process is used to fabricate a SiO2 (n = 1.43) refractive index matching layer 2 in a reaction chamber at 150℃. The thickness of the refractive index matching layer 2 is 1nm, which makes the groove width change from d2 to d1 = 739 nm.

[0078] (3) Further, oxygen plasma-assisted atomic layer deposition was used to fabricate a diffraction enhancement layer 3 with a thickness of t=208 nm. An oxygen-argon mixed (1:5) plasma-assisted atomic layer deposition process was used to deposit a Nb2O5 main layer and a SiO2 intercalation layer in a reaction chamber at 150 °C, with a period thickness ratio of 8 nm:1 nm. The introduction of argon plasma and the higher reaction temperature helped to improve the density and deposition uniformity of Nb2O5.

[0079] (4) A silver film, i.e., an environmental medium 4, is deposited using a room temperature multi-angle directional evaporation method to fill the grooves on the grating surface.

[0080] (5) Next, protective films Al2O3 and SiO2 are deposited to finally complete the fabrication of the grating surface thin film.

[0081] Aiming for the highest reflection and diffraction efficiency at a wavelength of 2300 nm, the inventors optimized the grating structure using grating design software, comparing the optimized structure with and without the diffraction enhancement layer 3, and obtained the following results: Figure 6 The structural diagram shown is included. Figure 6 (a) in the image represents an immersion grating with a diffraction enhancement layer 3. Figure 6(b) shows an immersion grating without a diffraction enhancement layer. The difference between having and not having the diffraction enhancement layer 3 lies in the different groove widths used to fill the ambient medium 4. The main structural parameters of the grating with the diffraction enhancement layer 3 are: d1 = 739 nm, h = 900 nm, t = 208 nm; the main structural parameters of the grating without the diffraction enhancement layer 3 are: d1 = 110 nm, h = 900 nm, t = 0 nm. A comparison shows that the introduction of the diffraction enhancement layer 3 increases the groove width (d1-2t) for filling the silver film by approximately two times (from 110 nm to 323 nm), which is beneficial for the full filling of the silver film within the groove. The diffraction efficiencies of the gratings with and without the diffraction enhancement layer 3 are as follows: Figure 7 and Figure 8 As shown. From Figure 7 and Figure 8 It can be seen that, Figure 7 The difference in polarization diffraction efficiency is smaller (with a diffraction enhancement layer).

[0082] Example 3:

[0083] This embodiment provides a transmission immersion grating for industrial mass production, requiring high diffraction efficiency over a wide wavelength range and possessing the ability to optimize high diffraction efficiency bands at low cost. The specific design concept is as follows: First, UV photosensitive adhesive is directly coated onto prism glass, and the same grating basic structure is fabricated using UV curing nanoimprinting or photomask lithography. Then, plasma-assisted atomic layer deposition is used to modify the d1 and t parameters, forming a diffraction efficiency optimization for multiple wavelengths such as 450, 550, 650, and 750 nm, enabling mass production.

[0084] The basic structural parameters of the design include: the grating substrate 1 is glass and photosensitive adhesive with the same refractive index (n=1.56), the refractive index matching layer 2 is an Al2O3 and SiO2 nanolayer stack with a thickness ratio of 1:1, the diffraction enhancement layer 3 is a 4nm TiO2 main layer and a 0.4nm SiO2 intercalation stack (n=2.3), the grating period is 500 nm, and the grating groove depth h=1000 nm.

[0085] In a 60℃ reaction chamber, the following four grating structures are formed by coating modification of the grating structure:

[0086] (1) Structure 1@450 nm: d1=175 nm, t=0 nm, incident angle is 16.4°;

[0087] (2) Structure 2@550 nm: d1=185 nm, t=0 nm, incident angle is 20.0°;

[0088] (3) Structure 3@650 nm: d1=245 nm, t=10 nm, incident angle is 25.1°;

[0089] (4) Structure 4@750 nm: d1=382 nm, t=70 nm, incident angle is 30.4°.

[0090] Simulation analysis was performed on the above four grating structures to obtain their respective diffraction efficiency spectra at optimized incident angles, such as... Figure 9 As shown, the grating in this embodiment meets the requirements of wide band, high diffraction efficiency, tunable band, and low cost.

[0091] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. An atomic-level composite film structure with modified grating grooves, characterized in that, The modified grating groove-type atomic-level composite film structure sequentially includes a grating substrate, a refractive index matching layer, and a diffraction enhancement layer; wherein the surface of the grating substrate has a periodically distributed groove structure; the refractive index matching layer is a nano-stack composed of a high refractive index sublayer and a low refractive index sublayer or a single-component film layer; the diffraction enhancement layer is composed of a single-layer high refractive index film.

2. The atomic-level composite film structure with modified grating grooves according to claim 1, characterized in that, The equivalent refractive index n of the nanolayer eff The thickness proportion f of the high-refractive-index sublayer satisfies the following relationship: ； Where, n eff n is the equivalent refractive index of the refractive index matching layer, f is the thickness percentage of the high refractive index sublayer, and n is the thickness percentage of the high refractive index sublayer. H n represents the refractive index value of the high-refractive-index sublayer. L This represents the refractive index value of the low-refractive-index sublayer.

3. The atomic-level composite film structure with modified grating grooves according to claim 1, characterized in that, The relative deviation between the equivalent refractive index of the refractive index matching layer and the refractive index of the grating substrate material is less than 5%; the periodic optical thickness of the nanolayer stack of the refractive index matching layer is less than one-tenth of the reference wavelength.

4. The atomic-level composite film structure with modified grating grooves according to claim 1, characterized in that, The diffraction enhancement layer contains a plurality of amorphous sublayers with a thickness of 0.2 to 4.0 nm that are uniformly embedded inside.

5. The atomic-level composite film structure with modified grating grooves according to any one of claims 1 to 4, characterized in that, The modified grating groove-type atomic-level composite film structure also includes an environmental medium, which fills the groove structure; the environmental medium is air or a highly reflective metal.

6. The atomic-level composite film structure with modified grating grooves according to claim 5, characterized in that, When the required diffracted light exits in a transmission manner, the ambient medium is air; when the required diffracted light exits in a reflection manner, the ambient medium is a highly reflective metal; the highly reflective metal is gold, silver, or aluminum.

7. The atomic-level composite film structure with modified grating grooves according to claim 6, characterized in that, When the environmental medium is a highly reflective metal, a metal film protective film is covered on the highly reflective metal, and the metal film protective film is a double-layer film of Al2O3 and SiO2.

8. The fabrication process of the modified grating groove-type atomic-level composite film structure according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: A rectangular groove with period d, depth h, and width d2 is etched on the grating substrate, and the cross section of the same batch of grating reference sheet is imaged by scanning electron microscopy. The precise structural parameters, including period d, depth h, and width d2, are determined using the electron microscope chart ruler. S2: A thickness of [thickness value missing] is fabricated using plasma-assisted atomic layer deposition at a temperature of 60~150℃. The refractive index matching layer causes the groove width to change from d2 to d1; the refractive index matching layer is a single-component film layer or a nanolayer composed of a high-refractive-index sublayer and a low-refractive-index sublayer; the equivalent refractive index n of the nanolayer is... eff The thickness proportion f of the high-refractive-index sublayer satisfies the following relationship: ; where n eff n is the equivalent refractive index of the refractive index matching layer, f is the thickness percentage of the high refractive index sublayer, and n is the thickness percentage of the high refractive index sublayer. H n represents the refractive index value of the high-refractive-index sublayer. L The refractive index value of the low-refractive-index sublayer; S3: A diffraction enhancement layer of thickness t is fabricated using plasma-assisted atomic layer deposition.

9. The fabrication process of the modified grating groove-type atomic-level composite film structure according to claim 8, characterized in that, When the required diffracted light exits in a reflective manner, the fabrication process also includes the following steps: S4: A high-reflectivity metal film is deposited using a room-temperature multi-angle directional evaporation method, and the high-reflectivity metal film fills the grooves on the grating surface.

10. The fabrication process of the modified grating groove-type atomic-level composite film structure according to claim 8, characterized in that, The preparation process also includes a step of depositing a metal protective film, which is achieved by electron beam evaporation deposition of the metal protective film.

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