A rare earth doped optical imaging film and a method of making the same

Abstract

This invention discloses a rare-earth-doped optical imaging film and its preparation method. The method specifically includes: providing an optical glass substrate and pre-treating its surface; sputtering a base layer onto the surface of the optical glass substrate; depositing a rare-earth-doped layer onto the surface of the base layer; etching micro / nano structures onto the surface of the doped layer; using the micro / nano structures to enhance the luminescence efficiency of the doped layer; depositing a hydrophobic layer onto the surfaces of the doped layer and the micro / nano structures; and annealing the optical glass substrate forming the base layer, doped layer, and hydrophobic layer to obtain the rare-earth-doped optical imaging film. Through optimized design of the base layer, doped layer, and micro / nano structures, the optical imaging film exhibits higher luminescence efficiency, lower light loss, and maintains stable optical properties during long-term use. Therefore, this invention solves the technical problem of the imbalance between high refractive index and low absorption loss in existing optical imaging films.

Description

Technical Field

[0001] This invention relates to the field of optical imaging film preparation, and more particularly to an optical imaging film doped with rare earth elements and its preparation method. Background Technology

[0002] Optical imaging films are functional thin films used in optical imaging systems. They are typically coated onto a substrate material (such as glass, plastic, or a flexible substrate) to achieve specific optical functions. Their core role is to optimize the propagation properties of light, including refraction, reflection, absorption, and scattering, thereby improving the performance of the imaging system. Optical imaging films are widely used in photography, display technology, medical imaging, augmented reality (AR), and virtual reality (VR) fields.

[0003] In existing technologies, to achieve efficient light coupling and extraction, traditional optical imaging films are typically fabricated using high-refractive-index materials. However, this fabrication method often results in an imbalance between the high refractive index and low absorption loss of the optical imaging film, thus reducing light utilization. Summary of the Invention

[0004] The purpose of this invention is to provide an optical imaging film doped with rare earth elements and its preparation method, which solves the technical problem of the imbalance between high refractive index and low absorption loss in existing optical imaging films.

[0005] To achieve this objective, the present invention adopts the following technical solution: According to a first aspect, the present invention discloses a method for preparing an optical imaging film doped with rare earth elements, comprising: Step S1: Provide an optical glass substrate and pre-treat the surface of the optical glass substrate to improve the surface adhesion of the optical glass substrate; Step S2: A substrate layer is sputtered onto the surface of the optical glass substrate; the substrate layer is made of silicon oxide or silicon nitride material; Step S3: Deposit a doped layer containing rare earth elements on the surface of the substrate layer; the rare earth elements are neodymium, erbium, or ytterbium. Step S4: Etching micro / nano structures onto the surface of the doped layer; the micro / nano structures are used to enhance the luminescence efficiency of the doped layer. Step S5: A hydrophobic layer is deposited on the surface of the doped layer and the micro / nano structure; Step S6: Anneal the optical glass substrate forming the base layer, the doped layer and the hydrophobic layer to obtain an optical imaging film doped with rare earth elements.

[0006] Optionally, step S1 includes: Step S11: Provide an optical glass substrate, wherein the optical glass substrate is made of silicate glass, borosilicate glass or phosphate glass; Step S12: The optical glass substrate is ultrasonically cleaned sequentially with deionized water, acetone and anhydrous ethanol, with each ultrasonic cleaning lasting 5 to 10 minutes. Step S13: The optical glass substrate after ultrasonic cleaning is subjected to ion beam bombardment treatment; the ion beam is low-energy argon ions or argon fluoride ions, and the bombardment energy range is 50~200eV.

[0007] Optionally, after step S11, the method further includes: Step S14: A coupling layer is coated on the surface of the optical glass substrate that has been treated with ion beam bombardment; the coupling layer is composed of aminosilane or fluorosilane molecules; Step S15: Place the optical glass substrate coated with the coupling layer in a vacuum drying oven and dry it at a temperature of 150-250°C for 10-30 minutes.

[0008] Optionally, step S2 includes: Step S21: On the surface of the pretreated optical glass substrate, a base layer is deposited using pulsed laser sputtering technology; Step S22: During the sputtering deposition process, the oxygen / nitrogen flow rate ratio is dynamically adjusted in the reaction chamber to form a substrate layer with a gradient refractive index; wherein, the initial oxygen / nitrogen flow rate ratio ranges from 1:1 to 5:1. Step S23: After the substrate layer deposition is completed, the optical glass substrate is subjected to plasma annealing treatment; the plasma annealing treatment uses argon or oxygen plasma and is treated with 300-600W radio frequency power for 5-15 minutes.

[0009] Optionally, the doped layer includes a transition layer and a functional layer, and step S3 specifically includes: Step S31: Deposit a transition layer on the surface of the substrate layer, the transition layer being made of magnesium fluoride or titanium dioxide material; Step S32: Deposit a functional layer doped with rare earth elements on the surface of the transition layer. The functional layer is made of yttrium oxide, aluminum oxide or lanthanum fluoride as matrix material and doped with neodymium ions, erbium ions or ytterbium ions. Step S33: During the sputtering process, the rare earth elements in the functional layer are gradient-distributed by dynamically adjusting the oxygen / nitrogen atmosphere flow ratio.

[0010] Optionally, step S32 specifically includes: Step S321: Deposit a functional layer doped with rare earth elements on the surface of the transition layer using a pulsed laser deposition method; Step S322: When depositing the functional layer, a co-doping rule is adopted; wherein, the co-doping rule is: for erbium-doped functional layers, ytterbium ions are introduced as sensitizing ions; for neodymium-doped functional layers, lanthanum ions or cerium ions are introduced. Step S323: After the functional layer is deposited, low-energy ions are used for auxiliary treatment to improve the luminescence efficiency of the functional layer.

[0011] Optionally, step S4 includes: Step S41: Electron beam etching is used to etch micro / nano structures on the surface of the doped layer; the depth of the micro / nano structures ranges from 20 nm to 200 nm. Step S42: After the micro / nano structure is formed, the surface of the micro / nano structure is subjected to plasma-assisted modification treatment using O2 or CF4 plasma.

[0012] Optionally, after step S42, the method further includes: Step S43: A transparent dielectric layer is deposited on the surface of the doped layer using atomic layer deposition technology. The refractive index of the transparent dielectric layer is between 1.3 and 1.8.

[0013] Optionally, in step S5, the hydrophobic layer is composed of fluoride, polytetrafluoroethylene or fluorosilane molecules, with a thickness ranging from 1 to 5 nm, and the deposition temperature is controlled at 100-150°C.

[0014] According to a second aspect, the present invention discloses an optical imaging film doped with rare earth elements, which is prepared by the preparation method of the optical imaging film doped with rare earth elements in the first aspect, comprising: an optical glass substrate, wherein a base layer is sputtered on the optical glass substrate, and a doped layer doped with rare earth elements is deposited on the base layer. The surface of the doped layer is etched with micro- and nano-structures, and a hydrophobic layer is deposited on the surface of the doped layer and the micro- and nano-structures.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an optical imaging film doped with rare earth elements and its preparation method. Pre-treatment of the optical glass substrate effectively removes surface contaminants and oxide layers, enhancing surface adhesion and improving film stability. The substrate layer optimizes stress distribution, preventing cracks or internal defects during subsequent film deposition and improving film structure integrity. Depositing a rare earth-doped layer on the substrate surface optimizes luminescence efficiency; the design of this doped layer ensures high luminescence intensity while suppressing light absorption loss within an appropriate wavelength range. The micro / nano structure not only enhances the luminescence efficiency of the doped layer but also reduces total internal reflection through light scattering and refraction, avoiding losses caused by light reflection from traditional optical films. The hydrophobic layer design effectively reduces contact between the optical imaging film surface and moisture or other contaminants, further reducing absorption loss. Annealing improves film density and uniformity, activates the optical properties of rare earth ions in the doped layer, and further reduces light scattering and absorption loss. Therefore, this invention solves the technical problem of the imbalance between high refractive index and low absorption loss in existing optical imaging films. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0018] Figure 1 This is a schematic flowchart of a method for preparing an optical imaging film doped with rare earth elements, as disclosed in Embodiment 1 of the present invention. Detailed Implementation

[0019] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1: This invention provides a method for preparing an optical imaging film doped with rare earth elements, such as... Figure 1 As shown, it includes: Step S1: Provide an optical glass substrate and pre-treat the surface of the optical glass substrate to improve the surface adhesion of the optical glass substrate; in this embodiment, the pre-treatment includes ultrasonic cleaning, ion beam bombardment, coating and drying. Step S2: A substrate layer is sputtered onto the surface of an optical glass substrate; the substrate layer is made of silicon oxide or silicon nitride material. Step S3: Deposit a doped layer containing rare earth elements on the surface of the substrate layer; the rare earth elements are neodymium, erbium, or ytterbium. Step S4: Etch micro / nano structures on the surface of the doped layer; the micro / nano structures are used to improve the luminescence efficiency of the doped layer. Step S5: A hydrophobic layer is deposited on the surface of the doped layer and the micro / nano structure. In this embodiment, the hydrophobic layer is composed of fluoride, polytetrafluoroethylene or fluorosilane molecules, with a thickness ranging from 1 to 5 nm, and the deposition temperature is controlled at 100-150°C. To ensure the uniformity and stability of the film, chemical vapor deposition is used for deposition. Chemical vapor deposition is a common technique in the field and will not be described in detail here. Step S6: Anneal the optical glass substrate forming the base layer, doped layer and hydrophobic layer to obtain an optical imaging film doped with rare earth elements.

[0023] It should be noted that the method for preparing a rare-earth-doped optical imaging film provided by this invention effectively removes surface contaminants and oxide layers by pre-treating the optical glass substrate, enhancing the surface adhesion of the optical glass substrate and improving the stability of the film layer. The substrate layer optimizes stress distribution, preventing cracks or internal defects in subsequent film deposition and improving the integrity of the film structure. Depositing a rare-earth-doped layer on the substrate surface optimizes luminous efficiency; the design of this doped layer ensures high luminous intensity while suppressing light absorption loss within an appropriate wavelength range. The micro / nano structure not only enhances the luminous efficiency of the doped layer but also reduces total internal reflection through light scattering and refraction, avoiding losses caused by light reflection from the surface of traditional optical films. The hydrophobic layer design effectively reduces contact between the optical imaging film surface and moisture or other contaminants, further reducing absorption loss. Annealing treatment helps improve the density and uniformity of the film layer, activates the optical properties of rare-earth ions in the doped layer, and further reduces light scattering and absorption loss. Therefore, this invention solves the technical problem of the imbalance between high refractive index and low absorption loss in existing optical imaging films.

[0024] In an optional embodiment, step S1 includes: Step S11: Provide an optical glass substrate, which is made of silicate glass, borosilicate glass or phosphate glass; Step S12 involves sequentially ultrasonically cleaning the optical glass substrate with deionized water, acetone, and anhydrous ethanol, with each ultrasonic cleaning session lasting 5-10 minutes. In this embodiment, the optical glass substrate undergoes multi-stage ultrasonic cleaning using an ultrasonic cleaning device. Cleaning with deionized water removes surface dust, dissolved contaminants, and some organic matter from the optical glass substrate. Cleaning with acetone effectively dissolves organic grease, fingerprints, and other contaminants on the surface of the optical glass substrate. Cleaning with anhydrous ethanol further removes organic residues and accelerates the drying of the optical glass substrate surface, preventing moisture residue from remaining on the surface. The ultrasonic cleaning device operates at a frequency range of 40-80 kHz to ensure effective removal of microparticles and organic contaminants from the optical glass substrate surface, while avoiding damage to the optical glass substrate due to ultrasonic cavitation. Ultrasonic cleaning equipment is a well-known technology in the art, and its working principle will not be elaborated here.

[0025] Step S13: The ultrasonically cleaned optical glass substrate is subjected to ion beam bombardment treatment; the ion beam is low-energy argon ions or argon fluoride ions, and the bombardment energy range is 50~200 eV. In this embodiment, the ion beam bombardment treatment uses low-energy ion beam bombardment equipment, such as a linear accelerator or electron bombardment ion source commonly used in the art; the ion beam bombards the surface of the optical glass substrate at a near-vertical angle to avoid excessive tilting that could lead to uneven ion bombardment or inconsistent glass surface morphology; Specifically, the ion current density of the low-energy ion beam bombardment equipment is controlled at 1×10⁻⁶. 6 ~1×10 8 The ion beam bombardment treatment was performed under high vacuum conditions, with the vacuum level maintained at 10 ions / cm². -5 ~10 -7 Between the turbinates, oxygen or moisture in the air can be prevented from interfering with the ion bombardment process. The temperature during the bombardment process is usually maintained at room temperature or slightly higher (20℃~100℃). Excessively high temperatures can cause thermal stress or morphological changes in the optical glass substrate.

[0026] It should be noted that step S1 of this invention combines ultrasonic cleaning and ion beam bombardment to achieve a highly clean optical glass substrate with good adhesion, thus providing excellent basic conditions for subsequent film deposition. This step effectively improves the stability, transmittance, and imaging quality of the optical imaging film, making it more widely applicable in high-precision optical imaging systems.

[0027] It should also be noted that ion beam bombardment creates appropriate nanoscale roughness on the surface of the optical glass substrate, enhancing its chemical activity. This increased surface energy contributes to the adhesion of subsequent film layers, preventing peeling or cracking, which is particularly important for doped or substrate layers requiring high adhesion. The micro- and nanoscale surface structures formed during bombardment provide a larger contact area for subsequent film deposition, improving the bonding between the film and the optical glass substrate and enhancing the film's mechanical stability. Low-energy ion beam bombardment helps remove minute surface defects and inhomogeneities, optimizes the glass surface structure, reduces stress or cracks that may occur during film deposition, and improves the stability and durability of the final optical imaging film.

[0028] In an optional embodiment, after step S11, the method further includes: Step S14: A coupling layer is coated on the surface of the optical glass substrate after ion beam bombardment. The coupling layer is composed of aminosilane or fluorosilane molecules. In this embodiment, the aminosilane can be 3-aminopropyltriethoxysilane. Aminosilane is suitable for scenarios requiring enhanced inorganic-organic interface bonding, and can form stable Si-O-Si bonds to improve film adhesion. The amino groups (-NH2) of aminosilane can chemically react with rare earth ions or other active groups in subsequent doped layers to enhance interlayer bonding. The fluorosilane can be 1H,1H,2H,2H-perfluorooctyltriethoxysilane. Fluorosilane coupling layers are suitable for optical imaging films requiring waterproof, fingerprint-resistant, and low surface energy properties.

[0029] Specifically, the coupling layer is prepared using spin coating equipment commonly used in the field. The spin coating equipment sprays the coupling agent onto the surface of an optical glass substrate that has been treated with ion beam bombardment. The spin coating equipment rotates at 1000~5000 rpm and the spin coating time is 10~60 seconds, which can form a uniform coupling layer.

[0030] Step S15: The optical glass substrate coated with the coupling layer is placed in a vacuum drying oven and dried at a temperature of 150-250°C for 10-30 minutes. In this embodiment, this drying step is performed in a high vacuum environment (10... -3 ~10 -6 The curing process is carried out under a controlled temperature (Torrent) to avoid interference from oxidation in the air that could affect the curing of the coupling layer. A drying temperature of 150-180℃ is suitable for aminosilane coupling layers, with a drying time of 20-30 minutes, which promotes the formation of chemical bonds between the amino group and the optical glass substrate surface. A drying temperature of 200-250℃ is suitable for fluorosilane coupling layers, with a drying time of 10-20 minutes, which enhances their hydrophobic properties and accelerates curing under high-temperature conditions.

[0031] It should be noted that, through the addition of the coupling layer, the alkoxy groups (-OR) at the ends of the coupling agent molecules fully react with the hydroxyl groups (-OH) on the glass surface to form a stable Si-O-Si cross-linked structure, thus improving the stability of the coupling layer. The drying process removes residual solvent from the coupling layer, preventing bubbles or defects during subsequent film deposition and improving the uniformity and optical transparency of the optical film. After drying, the coupling layer is more stable and less susceptible to environmental factors such as humidity and temperature, thereby improving the durability and stability of the film during long-term use.

[0032] In an optional embodiment, step S2 includes: Step S21: A base layer is deposited on the surface of the pretreated optical glass substrate using pulsed laser sputtering technology. In this embodiment, pulsed laser sputtering technology uses the high energy of a laser pulse to sputter silicon oxide or silicon nitride, and the sputtered particles and atoms are uniformly deposited on the surface of the optical glass substrate to form a base layer. The laser power of the laser pulse is 500~1500mJ / pulse, the pulse frequency is 1~10Hz, and argon (Ar) is used as the sputtering gas.

[0033] Step S22: During the sputtering deposition process, the oxygen / nitrogen flow rate ratio is dynamically adjusted within the reaction chamber to form a substrate layer with a gradient refractive index. The initial oxygen / nitrogen flow rate ratio is set to a range of 1:1 to 5:1 based on the material properties and refractive index gradient of the substrate layer. In this embodiment, the reaction chamber pressure is typically controlled at 10... -5 ~10 -3 Within the range of Torr, a smooth gradient change in the refractive index of the substrate can be achieved by adjusting the oxygen / nitrogen flow ratio. This gradient refractive index characteristic can effectively reduce light reflection loss and improve the transmittance of the film. When the oxygen flow rate is high, the deposition of oxides (such as silicon oxide) is enhanced, resulting in a relatively high refractive index. When the nitrogen flow rate is high, the deposited nitrides (such as silicon nitride) have a lower refractive index.

[0034] Step S23: After the substrate layer deposition is completed, the optical glass substrate is subjected to plasma annealing. The plasma annealing process uses argon or oxygen plasma and is performed at a radio frequency power of 300-600W for 5-15 minutes. In this embodiment, argon plasma is used to improve the uniformity and density of the film layer, while oxygen plasma can further promote the oxidation of the film layer and enhance its optical properties.

[0035] It should be noted that treating the deposited substrate layer with argon or oxygen plasma improves the crystallinity of the film, reduces internal defects, and enhances the adhesion between the film and the optical glass substrate. During annealing, the high-energy particles of the plasma interact with the film surface, altering the surface structure and chemical properties, further improving the film's density and stability. Plasma annealing effectively reduces amorphous regions in the film, improves the crystal structure, and reduces stress, contributing to the long-term stability of the optical film under high humidity and high temperature environments. Through gradient refractive index design and plasma annealing, the optical performance of the film can be significantly improved, light scattering reduced, imaging quality enhanced, and the film exhibiting higher transmittance and luminous efficiency in various optical applications.

[0036] Specifically, step S22 includes: Step S221: In the initial stage of basal layer deposition (0-30%), the initial oxygen to nitrogen flow ratio is set to 3:1. In step S222, during the middle stage of substrate deposition (30-70%), the oxygen flow rate is gradually reduced while the nitrogen flow rate is increased. In this embodiment, the oxygen to nitrogen flow rate ratio is adjusted from 3:1 to 2:1 or 1.5:1, so that the composition of the substrate gradually changes to nitrides (such as silicon nitride). At this time, the refractive index of the film gradually decreases to form a transition region of refractive index.

[0037] In step S223, during the later stage of basal layer deposition (70-100%), the nitrogen flow rate is further adjusted to make the oxygen to nitrogen flow rate ratio 1:1.

[0038] It should be noted that during the entire deposition process of the substrate layer, the change in the gas flow rate ratio can be controlled by linear or segmented changes, that is, the ratio of oxygen to nitrogen is gradually adjusted after each stage. Within the adjustment cycle, it can be optimized according to the deposition rate, and the gas flow rate ratio is adjusted every 5 to 15 minutes to ensure a smooth change in the refractive index of the substrate layer.

[0039] In an optional embodiment, the doped layer includes a transition layer and a functional layer, and step S3 specifically includes: Step S31: A transition layer is deposited on the surface of the substrate layer. The transition layer is made of magnesium fluoride or titanium dioxide. In this embodiment, the thickness of the transition layer is generally between 10 and 50 nm, and the specific thickness will be optimized according to the requirements of the doped layer and the overall optical performance requirements of the film. In order to obtain a uniform and dense film in a short time, the transition layer is deposited by pulsed laser sputtering (PLD).

[0040] Specifically, the pulsed laser power is 500-1000 mJ / pulse, and argon is used as the main gas in the sputtering atmosphere to ensure uniform deposition of the transition layer; the sputtering pressure is 10... -5 ~10 -4 Torr is used to ensure a balance between film quality and deposition rate.

[0041] Step S32: Deposit a functional layer doped with rare earth elements on the surface of the transition layer. The functional layer is made of yttrium oxide, aluminum oxide or lanthanum fluoride as matrix material and doped with neodymium ions, erbium ions or ytterbium ions. Step S33: During the sputtering process, the rare earth elements in the functional layer are gradient-distributed by dynamically adjusting the oxygen / nitrogen atmosphere flow ratio.

[0042] It should be noted that the deposition of the transition layer helps improve the interfacial bonding between the substrate layer and the functional layer, avoiding stress or film delamination problems caused by interfacial mismatch between different materials. The transition layer can effectively buffer the difference in thermal expansion between the substrate layer and the functional layer, reduce film stress, and improve the mechanical stability of the optical film. The deposition of the transition layer makes the deposition surface of the functional layer on the optical substrate smoother, reduces surface defects and roughness, and improves the uniformity and optical performance of the functional layer. By selecting a suitable transition layer material (such as magnesium fluoride or titanium dioxide), the transmittance and refractive index of the optical film can be improved, and the optical properties of the optical imaging film can be optimized, especially in the visible and near-infrared spectral range.

[0043] In an optional embodiment, step S32 specifically includes: Step S321: A rare-earth-doped functional layer is deposited on the surface of the transition layer using pulsed laser deposition. In this embodiment, the power of the pulsed laser is 300-600 mJ / pulse to ensure sufficient evaporation and effective deposition of the rare-earth elements and matrix material. The laser frequency is set to 1-10 Hz, suitable for higher deposition rates while ensuring the uniformity of the functional layer. Argon is used as the main sputtering gas to assist in promoting material evaporation and making the deposition process more uniform.

[0044] Step S322: During the deposition of the functional layer, a co-doping rule is adopted. This rule is as follows: for erbium-doped functional layers, ytterbium ions are introduced as sensitizing ions; for neodymium-doped functional layers, lanthanum or cerium ions are introduced. In this embodiment, ytterbium ions, as sensitizing ions, can absorb excitation light and transfer its energy to erbium ions, thereby improving the luminescence efficiency of erbium ions, especially in the 1.5µm band, which is widely used in fields such as optical fiber communication. Ytterbium ions, through their strong absorption characteristics, can effectively transfer energy to erbium ions, significantly improving the fluorescence emission intensity of erbium ions in this band. For neodymium-doped functional layers, the introduction of lanthanum or cerium ions can enhance the luminescence efficiency of neodymium ions. This optimizes the luminescence characteristics, especially in the near-infrared band, making it suitable for applications such as lasers and optical sensors.

[0045] Step S323: After the functional layer is deposited, low-energy ions are used for auxiliary processing to improve the luminescence efficiency of the functional layer. In this embodiment, the low-energy ions are argon ions or helium ions with an energy range of 50-300 eV, and the processing time is 5-15 minutes. However, excessively long processing times for low-energy ions can easily damage the film structure.

[0046] It should be noted that the co-doping rule enables the sensitized ions to effectively transfer energy to the main dopant ions (such as erbium and neodymium), reducing non-radiative transition losses and improving overall luminous efficiency. Low-energy ion treatment helps reduce defects in the film, improves the density and uniformity of the functional layer, thereby enhancing the optical stability of the functional layer and improving its reliability and performance in long-term use.

[0047] Specifically, step S33 includes: In step S331, during the initial stage of functional layer deposition (0-30%), the oxygen to nitrogen flow ratio is set to 3:1 or 4:1. In this embodiment, the oxygen flow rate is high and the nitrogen flow rate is relatively low in the initial stage to ensure the formation of the matrix structure of the functional layer and to provide a basis for subsequent atmosphere adjustment.

[0048] In step S332, during the intermediate stage of functional layer deposition (30-70%), the oxygen to nitrogen flow rate ratio is adjusted to 2:1 or 1.5:1. In this embodiment, during this stage, due to the change in the oxygen to nitrogen flow rate ratio, a gradient refractive index structure gradually forms from the surface to the interior of the film. A higher nitrogen flow rate can promote the gradient distribution of rare earth elements, ensuring uniform excitation and luminescence characteristics of rare earth ions in the film. This structure can optimize the optical performance of the functional layer, reduce light reflection loss, and improve the transmittance and imaging quality of the functional layer.

[0049] In step S333, during the later stage of functional layer deposition (70-100%), the oxygen to nitrogen flow rate ratio is adjusted to 1:1. In this embodiment, by reducing the oxygen flow rate and increasing the nitrogen flow rate, the optical loss of the film is significantly reduced; the luminescence efficiency of rare earth elements is improved, thereby optimizing the optical performance of the functional layer, especially for applications in high-power lasers or high-sensitivity optical sensors.

[0050] It should be noted that the adjustment of the oxygen to nitrogen flow rate ratio is divided into three stages: In the initial stage, a high oxygen flow rate is maintained to ensure the deposition of the oxide matrix; in the middle stage, the oxygen flow rate is gradually reduced while the nitrogen flow rate is increased to optimize the gradient refractive index structure; in the later stage, a high nitrogen flow rate ratio is used to ensure the distribution of rare earth elements in the doped layer and reduce light absorption loss. The flow rate ratio change time in each stage is typically 5–15 minutes, and can be flexibly adjusted according to the functional layer deposition rate and the desired optical properties. During longer deposition processes, the gas flow rate ratio can be gradually transitioned to achieve the ideal optical properties of the film.

[0051] In an optional embodiment, step S4 includes: Step S41: Electron beam etching technology is used to etch micro-nano structures on the surface of the doped layer; the depth range of the micro-nano structures is 20nm to 200nm; in this embodiment, an electron beam etching device is used to etch the micro-nano structures in a vacuum environment, the micro-nano structures are periodically or randomly distributed, and the power of the electron beam is 1~10kV.

[0052] Step S42: After the micro / nano structure is formed, the surface of the micro / nano structure is subjected to plasma-assisted modification treatment using O2 or CF4 plasma. In this embodiment, a low-power plasma source of 100~300W is used, and the treatment time is 5~15 minutes to avoid over-treatment that could damage the film. Plasma modification is usually performed in a low-temperature environment (room temperature~150℃) to ensure that the optical properties of the doped layer are not affected.

[0053] It should be noted that micro- and nanostructures can increase light absorption in the film layer through the local enhancement effect, thereby improving the luminous efficiency of the doped layer. Micro- and nanostructures can focus and scatter light, optimizing the optical properties of the doped layer, and have significant effects, especially in applications such as laser gain and fiber optic sensors.

[0054] In an optional embodiment, after step S42, the method further includes: Step S43: A transparent dielectric layer is deposited on the surface of the doped layer using atomic layer deposition (ALD). The refractive index of the transparent dielectric layer is between 1.3 and 1.8. In this embodiment, the transparent dielectric layer is made of transparent materials such as silicon dioxide, silicon nitride, or alumina. Silicon nitride has good transparency in the ultraviolet and near-infrared bands, but low transmittance in the visible light range. Alumina has high transparency in the ultraviolet and visible light bands and high resistance to ultraviolet radiation. Silicon dioxide is commonly used in optical coatings and optical lenses. Silicon nitride is suitable for high-performance optical applications, especially those requiring high temperature resistance and scratch resistance. Alumina is suitable for optical devices requiring high strength and heat resistance. Furthermore, ALD is a well-known technique in the art and will not be described in detail here. The deposition temperature is 100℃~250℃, and the deposition temperature can be optimized according to the selected material and the characteristics of the desired thin film.

[0055] It should be noted that by controlling the refractive index of the transparent dielectric layer, the optical properties of the doped layer can be optimized, reducing reflection and light loss. The deposition of the transparent dielectric layer not only helps to improve the optical performance of the film, but also enhances the chemical stability and environmental resistance of the film, preventing the film from being affected by moisture, oxidation, or contamination during long-term use.

[0056] In practice, the annealing process in step S6 is carried out in an inert atmosphere (such as nitrogen or argon) or oxygen-controlled environment to avoid unnecessary chemical reactions or oxidative degradation of the film at high temperatures. For silicon oxide substrates, the annealing temperature is 600℃~800℃, which helps eliminate stress introduced during film deposition and improves film density. For silicon nitride substrates, the annealing temperature is 400℃~700℃, which promotes the bonding of nitrogen atoms in the film with the optical glass substrate, improving the film's durability and heat resistance. The annealing time is generally controlled between 30 and 120 minutes to ensure sufficient diffusion and rearrangement of atoms within the film, achieving stable physical and optical properties. In specific applications, annealing can also be performed in a vacuum environment to further reduce defects and adsorbed moisture in the film and improve optical uniformity.

[0057] To ensure uniform heating of the film and prevent cracks or peeling of the optical imaging film due to thermal shock, the annealing process in step S6 adopts a slow heating method with a heating rate of 5℃ / min to 10℃ / min. After annealing, the film is slowly cooled to room temperature with a cooling rate of 3℃ / min to 5℃ / min. This slow cooling step can avoid thermal stress concentration caused by rapid cooling, thereby improving the mechanical stability of the film.

[0058] Example 2: This invention provides an optical imaging film doped with rare earth elements, which is prepared using the preparation method of the optical imaging film doped with rare earth elements in Example 1, specifically including: an optical glass substrate, a base layer sputtered on the optical glass substrate, and a doped layer doped with rare earth elements deposited on the base layer. Among them, micro- and nano-structures are etched on the surface of the doped layer, and a hydrophobic layer is deposited on the surface of the doped layer and the micro- and nano-structures.

[0059] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an optical imaging film doped with rare earth elements, characterized in that, include: Step S1: Provide an optical glass substrate and pre-treat the surface of the optical glass substrate to improve the surface adhesion of the optical glass substrate; Step S2: A base layer is sputtered onto the surface of the optical glass substrate; Step S3: Deposit a doped layer containing rare earth elements on the surface of the substrate layer; the rare earth elements are neodymium, erbium, or ytterbium. Step S4: Etching micro / nano structures onto the surface of the doped layer; the micro / nano structures are used to enhance the luminescence efficiency of the doped layer. Step S5: A hydrophobic layer is deposited on the surface of the doped layer and the micro / nano structure; Step S6: Anneal the optical glass substrate forming the base layer, the doped layer and the hydrophobic layer to obtain an optical imaging film doped with rare earth elements. Step S2 includes: Step S21: On the surface of the pretreated optical glass substrate, silicon oxide or silicon nitride is sputtered by pulsed laser sputtering technology, and the sputtered particles and atoms are uniformly deposited on the surface of the optical glass substrate. Step S22: During the sputtering deposition process, the oxygen / nitrogen flow rate ratio is dynamically adjusted in the reaction chamber to form a substrate layer with a gradient refractive index; wherein, the initial oxygen / nitrogen flow rate ratio ranges from 1:1 to 5:

1. Step S23: After the substrate layer deposition is completed, the optical glass substrate is subjected to plasma annealing treatment; the plasma annealing treatment uses argon or oxygen plasma and is treated with 300-600W radio frequency power for 5-15 minutes.

2. The method for preparing a rare-earth-doped optical imaging film according to claim 1, characterized in that, Step S1 includes: Step S11: Provide an optical glass substrate, wherein the optical glass substrate is made of silicate glass, borosilicate glass or phosphate glass; Step S12: The optical glass substrate is ultrasonically cleaned sequentially with deionized water, acetone and anhydrous ethanol, with each ultrasonic cleaning lasting 5 to 10 minutes. Step S13: The optical glass substrate after ultrasonic cleaning is subjected to ion beam bombardment treatment; the ion beam is low-energy argon ions or argon fluoride ions, and the bombardment energy range is 50~200eV.

3. The method for preparing an optical imaging film doped with rare earth elements according to claim 2, characterized in that, Following step S13, the method further includes: Step S14: A coupling layer is coated on the surface of the optical glass substrate that has been treated with ion beam bombardment; the coupling layer is composed of aminosilane or fluorosilane molecules; Step S15: Place the optical glass substrate coated with the coupling layer in a vacuum drying oven and dry it at a temperature of 150-250°C for 10-30 minutes.

4. The method for preparing a rare-earth-doped optical imaging film according to claim 1, characterized in that, The doped layer includes a transition layer and a functional layer, and step S3 specifically includes: Step S31: Deposit a transition layer on the surface of the substrate layer, the transition layer being made of magnesium fluoride or titanium dioxide material; Step S32: Deposit a functional layer doped with rare earth elements on the surface of the transition layer. The functional layer is made of yttrium oxide, aluminum oxide or lanthanum fluoride as matrix material and doped with neodymium ions, erbium ions or ytterbium ions. Step S33: During the sputtering process, the rare earth elements in the functional layer are gradient-distributed by dynamically adjusting the oxygen / nitrogen atmosphere flow ratio.

5. The method for preparing an optical imaging film doped with rare earth elements according to claim 4, characterized in that, Step S32 specifically includes: Step S321: Deposit a functional layer doped with rare earth elements on the surface of the transition layer; Step S322: When depositing the functional layer, a co-doping rule is adopted; wherein, the co-doping rule is: for erbium-doped functional layers, ytterbium ions are introduced as sensitizing ions; for neodymium-doped functional layers, lanthanum ions or cerium ions are introduced. Step S323: After the functional layer is deposited, low-energy ions are used for auxiliary treatment to improve the luminescence efficiency of the functional layer.

6. The method for preparing a rare-earth-doped optical imaging film according to claim 1, characterized in that, Step S4 includes: Step S41: Electron beam etching is used to etch micro / nano structures on the surface of the doped layer; the depth of the micro / nano structures ranges from 20 nm to 200 nm. Step S42: After the micro / nano structure is formed, the surface of the micro / nano structure is subjected to plasma-assisted modification treatment using O2 or CF4 plasma.

7. The method for preparing a rare-earth-doped optical imaging film according to claim 6, characterized in that, Following step S42, the method further includes: Step S43: A transparent dielectric layer is deposited on the surface of the doped layer using atomic layer deposition technology. The refractive index of the transparent dielectric layer is between 1.3 and 1.

8.

8. The method for preparing an optical imaging film doped with rare earth elements according to any one of claims 1-7, characterized in that, In step S5, the hydrophobic layer is composed of polytetrafluoroethylene or fluorosilane molecules, with a thickness ranging from 1 to 5 nm, and the deposition temperature is controlled at 100-150°C.

9. A rare-earth-doped optical imaging film, prepared using the method for preparing a rare-earth-doped optical imaging film as described in any one of claims 1 to 8, characterized in that, include: An optical glass substrate, wherein a base layer is sputtered on the optical glass substrate, and a doped layer doped with rare earth elements is deposited on the base layer; The surface of the doped layer is etched with micro- and nano-structures, and a hydrophobic layer is deposited on the surface of the doped layer and the micro- and nano-structures.

Images