Gradient doped perovskite / lithium niobate heterojunction on-chip laser and preparation method thereof

Abstract

The invention relates to the technical field of optoelectronic integrated devices, in particular to a gradient doped perovskite / lithium niobate heterojunction on-chip laser and a preparation method thereof. Comprising the following steps: ultrasonically cleaning a lithium niobate micro-disk chip, and blow-drying with high-purity nitrogen; argon plasma is introduced, and activating treatment is carried out for 5-15 minutes; preparing a precursor solution in which rare earth ions account for 10-15% of the total molar weight of metal cations in the perovskite; after magnetic stirring and filtering by a filter membrane, taking a small amount of precursor solution to drop on the surface of the treated lithium niobate micro-disk, and spin-coating to form a highly-doped interface anchoring layer; preparing a main precursor solution in which rare earth ions account for 2-5% of the total molar weight of metal cations in perovskite; when the highly-doped interface anchoring layer is not completely dried, a main precursor solution is dropwise added, spin coating is carried out according to preset spin coating parameters, and a main gain layer is obtained; and executing a two-stage annealing procedure, and cooling to room temperature. The system has the advantages that extra optical loss is not introduced in a non-laser area, and the system integration degree is higher.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic integrated device technology, and in particular to a gradient-doped perovskite / lithium niobate heterojunction on-chip laser and its fabrication method. Background Technology

[0002] Lithium niobate (LiNbO3, LN) crystals have become an ideal emerging platform for integrated photonics due to their wide optical transmission window, high refractive index, and excellent electro-optic and nonlinear optical coefficients. High-quality factor (Q-value) microcavities and waveguide devices based on lithium niobate thin films (LNOI) are developing rapidly. However, as an indirect bandgap semiconductor, LN has extremely low intrinsic luminous efficiency, which is a core bottleneck for realizing on-chip light sources on LN photonic chips.

[0003] Currently, there are two main technical routes to solve this bottleneck: (1) Rare earth ion doping: by doping Er in the LN lattice 3+ 、Nd 3+ Rare earth ions are used to give them luminescence capabilities. Although this method has achieved low threshold optically pumped lasers at the microwatt level, its laser efficiency and wavelength tunability are poor due to the inherent small emission cross-section of rare earth ions, intrinsic optical losses introduced by doping, and fixed emission wavelength. (2) III-V group semiconductor heterogeneous integration: InP and other direct bandgap semiconductor gain materials are integrated onto LN substrates through wafer bonding and other technologies. This method can achieve room temperature electrically pumped, milliwatt-level output lasers, but it faces challenges such as complex processes, high bonding interface losses, material thermal mismatch, and long-term reliability.

[0004] In summary, developing high-performance on-chip laser sources that are highly compatible with lithium niobate photonic platforms still faces significant challenges, and there is an urgent need to explore new gain media and integration solutions.

[0005] Metal halide perovskites, particularly quasi-two-dimensional perovskites (Ruddlesden-Popper phase), have emerged as a novel gain medium, exhibiting excellent optical gain properties, high fluorescence quantum yield, and good solution processability. Their unique "multiple quantum well" structure can generate an "energy funnel" effect, enabling rapid transfer of exciton energy from a wide bandgap (low n-value) layer to a narrow bandgap (high n-value) layer, thereby achieving efficient carrier accumulation and population inversion, and holds promise for obtaining extremely low lasing thresholds. However, current research has largely focused on the visible light band, with very few reports on achieving room-temperature continuous-wave lasing in the near-infrared band (especially the communication band).

[0006] Combining quasi-two-dimensional perovskite with a high-Q lithium niobate microcavity theoretically allows for the simultaneous utilization of the high gain of perovskite and the strong optical field confinement capability of lithium niobate microcavities, representing a highly promising technical approach for realizing low-threshold near-infrared on-chip lasers. However, this approach faces a critical integration challenge: the perovskite precursor solution exhibits poor wettability on the smooth, chemically inert surface of lithium niobate crystals, making uniform film formation difficult, and the heterojunction interface exhibits weak adhesion and poor stability. The core reason for this problem lies in the fact that lithium niobate, as an inorganic oxide, lacks strong chemical bonding with the organic-inorganic hybrid perovskite gain layer, relying solely on van der Waals forces for stabilization. This leads to warping, cracking, and even detachment of the film during subsequent processing or operation. Simultaneously, poor interfacial adhesion creates tiny air gaps, weakening optical coupling and introducing scattering losses, thereby reducing the Q value of the resonant cavity and increasing the lasing threshold, severely restricting the realization of high-performance lasers and their long-term operational reliability. Existing perovskite heterointegrated lasers, due to direct spin-coating, have further limited interface stability and environmental tolerance, hindering their practical application and requiring improved reliability. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a gradient-doped perovskite / lithium niobate heterojunction on-chip laser and its fabrication method.

[0008] The primary objective of this invention is to provide a method for fabricating a laser on a gradient-doped perovskite / lithium niobate heterojunction, specifically comprising the following steps: S1. Select the pre-processed lithium niobate micro disk chip, ultrasonically clean it for 8-15 minutes, and then blow the surface moisture with high-purity nitrogen; introduce argon plasma and perform activation treatment at 80-150 W power for 5-15 minutes. S2. Prepare a high rare earth doped precursor solution so that rare earth ions account for 10-15% of the total molar amount of metal cations in the perovskite; after magnetic stirring, filter through a 0.22μm filter membrane; take a small amount of precursor solution and drop it onto the surface of the treated lithium niobate microdisk, spin-coat at 1000-1500rpm for 25-40 seconds to form a high doped interface anchoring layer. S3. Prepare a main precursor solution with conventional rare earth doping concentration so that rare earth ions account for 2-5% of the total molar amount of metal cations in the perovskite; when the highly doped interface anchoring layer is not completely dry, add the main precursor solution dropwise and spin coat it with preset spin coating parameters to obtain the main gain layer. S4. After spin coating, immediately transfer to a hot plate filled with argon protective atmosphere and perform a two-stage annealing procedure: the first stage is set at 65~75℃ and held for 1~3 minutes; the temperature is then raised to 95~105℃ and held for 6~10 minutes; the temperature is then cooled to room temperature to obtain a laser on a gradient-doped perovskite / lithium niobate heterojunction.

[0009] Preferably, the specific method for ultrasonic cleaning in step S1 is as follows: using deionized water, acetone, and anhydrous ethanol in sequence, ultrasonically cleaning for 10 minutes each at a power of 80~150W; the purity of the high-purity nitrogen gas is ≥99.99%.

[0010] Preferably, the preparation method of the high rare earth doped precursor solution in step S2 is as follows: using perovskite material as the main system, the perovskite raw material is dissolved in a high boiling point mixed solvent according to a preset molar ratio, and then rare earth compounds are added so that the rare earth ions account for 10-15% of the total molar amount of metal cations in the perovskite.

[0011] Preferably, the perovskite material is selected from quasi-two-dimensional perovskite or three-dimensional perovskite; the perovskite raw material includes an organic cationic compound and a metal halide, wherein the organic cationic compound is selected from at least one of N-methylacetamide iodine, formamidinium iodine, butylammonium salt, and phenylethylammonium salt, and the metal halide is selected from at least one of lead iodide, lead bromide, and lead chloride; The high-boiling-point mixed solvent is a mixture of DMSO and GBL prepared at a volume ratio of 1:1.

[0012] Preferably, the rare earth ions are selected from Er 3+ 、Nd 3+ Yb 3+ or Tm 3+ At least one of the following; the rare earth compound is a chloride of the corresponding rare earth ion.

[0013] Preferably, the preparation method of the main precursor solution with conventional rare earth doping concentration is as follows: using perovskite material as the main system, the perovskite raw material is dissolved in DMF at a preset molar ratio, and then rare earth compounds are added so that the rare earth ions account for 2 to 5% of the total molar amount of metal cations in the perovskite; the perovskite raw material is the same as in step S2.

[0014] Preferably, the preset spin coating parameters in step S3 are: spin coating speed of 4000~5000 rpm and spin coating time of 30~60 seconds.

[0015] Preferably, the specific conditions for the two-stage annealing process in step S4 are: the first stage temperature is 70°C and the holding time is 2 minutes; the second stage temperature is 100°C and the holding time is 8 minutes.

[0016] Preferably, the thickness of the highly doped interface anchoring layer is 20~50 nm; the thickness of the main gain layer is 180~220 nm.

[0017] The second objective of this invention is to provide a gradient-doped perovskite / lithium niobate heterojunction on-chip laser, which is prepared using the aforementioned method for preparing a gradient-doped perovskite / lithium niobate heterojunction on-chip laser.

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) Significantly enhanced interfacial bonding and improved device reliability: This is due to the high concentration of Er at the interface. 3+ The "pinning" effect generated by doping enables a strong bond between the perovskite gain film and the LN microdisk substrate. This tight interface adhesion eliminates optical gaps, allowing the mode field of the LN microcavity to extend unimpeded into the gain layer, providing a reliable channel for laser oscillation.

[0019] (2) Simple and compatible process with high integration and applicability: This invention uses a low-temperature, all-solution process to prepare the gain layer, eliminating the need for high-temperature diffusion doping or wafer bonding processes, and has no destructive impact on existing LN photonic device manufacturing processes. The multi-step spin coating method is easy to operate, and the film thickness and doping gradient can be flexibly adjusted by changing the precursor solution ratio, exhibiting repeatability and scalability. The processing temperature as low as 100°C is compatible with CMOS processes, meaning that this solution can be implemented in the back-end packaging process without affecting the previously completed passive and active devices such as waveguides and modulators on the LN wafer. In the structure of this invention, the gain medium is limited to the microdisk resonant cavity region, while the remaining optical path parts retain the intrinsic LN material, thus ensuring low-loss operation of other devices on the chip. This has significant advantages over directly doping the entire LN wafer: it does not introduce additional optical loss in non-laser areas, resulting in higher system integration. Since no additional bonding wafers and collimation coupling structures are required, it is more conducive to mass production and integration with planar optical paths.

[0020] In summary, this invention demonstrates significant advantages in terms of manufacturing cost, process difficulty, and system integration, and is expected to accelerate the practical application of on-chip laser sources for LN. Attached Figure Description

[0021] Figure 1 These are SEM images of lithium niobate microdisks before and after the growth of perovskite films according to embodiments of the present invention; (a) lithium niobate microdisk before growth; (b) lithium niobate microdisk after growth; (c) a magnified view of a portion of the lithium niobate microdisk after growth.

[0022] Figure 2 The images show the XRD patterns of lithium niobate microdisks, perovskites, and gradient-doped perovskite / lithium niobate heterojunctions provided in embodiments of the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of a tapered optical fiber coupled to a lithium niobate microdisk according to an embodiment of the present invention.

[0024] Figure 4 This is an optical photograph of the successful coupling of a tapered optical fiber and a lithium niobate microdisk according to an embodiment of the present invention.

[0025] Figure 5This is an Er-doped solution provided according to an embodiment of the present invention. 3+ The photoluminescence spectrum of the perovskite thin film sample at 1550 nm. Detailed Implementation

[0026] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0027] 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 specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0028] The purpose of this invention is to overcome the shortcomings of the prior art and provide an innovative heterojunction laser structure and its fabrication method. Through a special doping structure design, the adhesion of the perovskite gain film to the resonant cavity surface of a lithium niobate (LN) microdisk is enhanced, avoiding film peeling and interfacial air gaps, and improving the interfacial bonding between the gain film and the LN substrate. This invention aims to solve the challenge of high-quality, high-strength heterojunction integration of perovskite gain media and lithium niobate microdisks through a combination of material and process innovation.

[0029] This invention provides a method for fabricating a laser on a gradient-doped perovskite / lithium niobate heterojunction. Through an innovative "time-controllable pulse spin-coating-diffusion annealing method," a quasi-two-dimensional perovskite gain film with a rare-earth ion concentration gradient is constructed on the surface of a lithium niobate microdisk. The method specifically includes the following steps: S1. Interface enhancement treatment of lithium niobate microdisk substrate: Select the processed lithium niobate microdisk chip, ultrasonically clean it for 8~15 minutes, and then blow the surface moisture with high-purity nitrogen; introduce argon plasma and perform activation treatment at 80~150 W power for 5~15 minutes. Specifically, use deionized water, acetone, and anhydrous ethanol in sequence for ultrasonic cleaning for 10 minutes each, with the ultrasonic power set to 100~150W during the process, to remove organic residues and micron-sized particulate contaminants from the surface; after cleaning, use 99.99% pure nitrogen to blow dry the surface moisture to avoid water stains. Argon plasma was introduced and activated for 10 minutes at 100 W power to introduce dangling bonds and improve surface hydrophilicity.

[0030] S2. Preparation of highly doped interface anchoring layer: Prepare a highly rare earth-doped precursor solution so that rare earth ions account for 10-15% of the total molar amount of metal cations in the perovskite; after magnetic stirring, filter through a 0.22 μm organic phase filter membrane; take a small amount of solution and drop it onto the surface of the treated lithium niobate microdisk, and spin-coat it at a low speed of 1000-1500 rpm for 25-40 seconds to form a highly doped interface anchoring layer; Specifically, the preparation method of the precursor solution with high rare earth doping is as follows: using perovskite material as the main system, the perovskite raw material is dissolved in a high-boiling-point mixed solvent at a preset molar ratio, and then rare earth compounds are added so that the rare earth ions account for 10-15% of the total molar amount of metal cations in the perovskite; Preferably, the perovskite material is selected from quasi-two-dimensional or three-dimensional perovskites; the perovskite material includes organic cationic compounds and metal halides; the organic cationic compound is selected from at least one of N-methylacetamide iodine, formamidinium iodine, butylammonium salt, and phenethylammonium salt; the metal halide is selected from at least one of lead iodide, lead bromide, and lead chloride; in some embodiments, (NMA)₂Fa n-1 Pb n I 3n+1 A quasi-two-dimensional perovskite master system; Rare earth ions are selected from Er 3+ 、Nd 3+ Yb 3+ or Tm 3+ At least one of the following; in some embodiments, the rare earth compound is erbium trichloride; The high-boiling-point mixed solvent includes DMSO and GBL; in some embodiments, the high-boiling-point mixed solvent is a mixture of DMSO and GBL prepared in a volume ratio of 1:1. The thickness of the highly doped interface anchoring layer is 20~50nm.

[0031] S3. Construction and fusion of the main gain layer gradient: Prepare a main precursor solution with a conventional rare earth doping concentration so that rare earth ions account for 2-5% of the total molar amount of metal cations in the perovskite; when the highly doped interface anchoring layer is not completely dry, add the main precursor solution dropwise and spin-coat with preset spin-coating parameters. Through solvent interdiffusion and shear force, a continuous vertical rare earth ion concentration gradient is formed from the interface to the film surface to obtain the main gain layer. Specifically, the highly doped interface anchoring layer is not completely dry within 5 to 15 seconds after spin coating. The main precursor solution uses a moderately volatile solvent as the main solvent. The perovskite main system is consistent with S2, and rare earth ions account for 2-5% of the total molar amount of metal cations in the perovskite. The preset spin coating parameters are: spin coating speed 4000~5000rpm, spin coating time 30~60 seconds; in some embodiments, the spin coating speed is 4500rpm and the spin coating time is 45 seconds.

[0032] S4. After spin coating, immediately transfer to a hot plate filled with argon protective atmosphere and perform a two-stage annealing procedure: the first stage is set at 65~75℃ and held for 1~3 minutes; the temperature is then raised to 95~105℃ and held for 6~10 minutes; after annealing, allow to cool naturally to room temperature to finally obtain a laser on a gradient-doped perovskite / lithium niobate heterojunction. In some embodiments, the first stage is set at 70°C and held for 2 minutes to slowly remove residual solvents (DMSO, GBL, DMF) from the film and induce initial crystallization of the perovskite, while retaining a small amount of ion mobility to optimize gradient uniformity. After the first stage annealing, without transferring the sample, the hot plate temperature is directly raised to 100°C for the second stage annealing, held for 8 minutes, to promote perovskite grain growth and film densification, ultimately locking the concentration gradient structure under temperature control below 120°C. After annealing, the film is naturally cooled to room temperature to obtain a dense and uniform gradient Er film with a thickness of approximately 200 nm. 3+ By doping quasi-two-dimensional perovskite gain films, a laser on a gradient-doped perovskite / lithium niobate heterojunction is finally obtained.

[0033] In some embodiments, the device packaging step is also included: after annealing and cooling, a PMMA protective coating is spin-coated onto the surface of the perovskite thin film or an ultrathin alumina protective layer is deposited by atomic layer deposition (ALD) technology to improve the environmental stability of the device.

[0034] Example 1 This embodiment provides a method for fabricating a laser on a gradient-doped perovskite / lithium niobate heterojunction, specifically including the following steps: S1. Lithium niobate microdisk substrate treatment: Select the pre-processed lithium niobate microdisk chip, and ultrasonically clean it for 10 minutes each with first-grade deionized water, analytical grade acetone, and anhydrous ethanol, with the ultrasonic power set at 120W during the process to remove surface organic residues and micron-sized particulate contamination; after cleaning, use 99.99% pure nitrogen to blow dry the surface moisture to avoid water stains. The lithium niobate microdisk chip was then placed in a plasma cleaner, and argon plasma was introduced. The power was set to 100W, and the surface was activated for 10 minutes to introduce dangling bonds and improve the surface hydrophilicity (the contact angle of the microdisk surface after activation is ≤30°).

[0035] S2. Preparation of highly doped interface anchoring layer: S21. Preparation of a high rare earth doped precursor solution: using (NMA)2Fa n-1 Pb n I 3n+1As a quasi-two-dimensional perovskite host system, N-methylacetamide iodine (NMAI), formamidinium iodine (FAI), and lead iodide (PbI2) were dissolved in a mixed solvent of dimethyl sulfoxide (DMSO) and γ-butyrolactone (GBL) in a molar ratio of 1.6:1.9:2; erbium trichloride (ErCl3) was added to make Er... 3+ Pb 2+ A high rare earth-doped precursor solution was obtained by using 12.5% ​​of the total molar amount. S22. Place the precursor solution on a magnetic stirrer and stir thoroughly to dissolve it. Then filter it through a 0.22 μm organic phase filter membrane to ensure film uniformity. Take a small amount of the precursor solution and drop it onto the surface of the activated lithium niobate microdisk chip. Spin-coat at 1200 rpm for 30 seconds to form a highly doped interface anchoring layer (rich in Er) with a thickness of about 30~35 nm. 3+ (Amorphous / nanocrystalline anchoring layer), which is semi-transparent and gels under the action of high-boiling-point solvents to retain some fluidity.

[0036] S3. Principal Gain Layer Gradient Construction and Fusion: S31. Preparation of a main precursor solution with conventional rare earth doping concentration: Dissolve N-methylacetamide iodine (NMAI), formamidinium iodine (FAI), and lead iodide (PbI2) in N,N-dimethylformamide (DMF) at a molar ratio of 1.6:1.9:2; add erbium trichloride (ErCl3) to make Er... 3+ Pb 2+ A main precursor solution with a conventional rare earth doping concentration was obtained by using 3.5% of the total molar amount. S32. Before the highly doped interface anchoring layer prepared in S2 is completely dry (within 10 seconds after spin coating), drop the precursor solution prepared in step S31 onto the highly doped interface anchoring layer, and immediately switch the spin coater to 4000 rpm for high-speed spin coating for 45 seconds; during spin coating, solvent interdiffusion occurs between the highly doped anchoring layer and the main precursor solution, Er 3+ Ions migrate towards the main gain layer under shear force, forming a continuous vertical concentration gradient from 12.5% ​​at the interface to 3.5% at the film surface, thus achieving functional stratification of "interface rich doping - bulk weak doping".

[0037] S4. Step-by-step low-temperature annealing: Immediately after spin coating, the sample was transferred to a hot plate filled with an argon protective atmosphere and subjected to a two-stage annealing procedure: The first stage was held at 70°C for 2 minutes to slowly remove residual solvents (DMSO, GBL, DMF) from the film and induce initial perovskite crystallization, while retaining a small amount of ion mobility to optimize gradient uniformity. After the first stage annealing, without transferring the sample, the hot plate temperature was directly raised to 100°C for the second stage annealing, held for 8 minutes, to promote perovskite grain growth (grain size reaching 200-300 nm) and film densification. Finally, the concentration gradient structure was locked under temperature control below 120°C. After annealing, the film was naturally cooled to room temperature, yielding a dense and uniform gradient Er film with a thickness of approximately 200 nm. 3+ A quasi-two-dimensional perovskite gain film was doped to obtain a gradient-doped perovskite / lithium niobate heterojunction on-chip laser. Through the above steps, low-temperature heterogeneous integration of gradient rare-earth-doped perovskite films was achieved on the surface of a lithium niobate microdisk resonator, balancing interface adhesion, optical gain, and integration compatibility, providing structural and material support for subsequent on-chip laser oscillation.

[0038] A systematic experimental characterization was performed on the laser samples fabricated on gradient-doped perovskite / lithium niobate heterojunction sheets, including measurements of material morphology and optical properties. The results are as follows: (1) Morphology and structure characterization: The morphological changes of LN microdisks before and after deposition of gain films were observed using scanning electron microscopy (SEM). Figure 1 (a) shows the morphology of the LN microdisk resonator before coating. It can be seen that the microdisk diameter is about 95 µm and the edge is smooth without obvious defects. Figure 1 Image (b) shows a top view of the microdisk after spin-coating a gradient-doped perovskite film. The gain layer is uniformly covered, and the circular outline of the edges remains clear, indicating that the film conforms well to the microdisk structure. Further cross-sectional SEM images show ( Figure 1 In the middle (c) image, the perovskite film is approximately 200 nm thick and adheres tightly to the surface of the LN microdisk, with a smooth and void-free interface. These results directly demonstrate the role of gradient doping in improving film adhesion. X-ray diffraction (XRD) analysis ( Figure 2 This indicates that the thin film exhibits characteristic diffraction peaks of a quasi-two-dimensional perovskite, and that the Er-doped film... 3+ It did not destroy the perovskite crystal structure, but it may have caused some peak intensity changes, suggesting Er 3+ It enters the crystal lattice or grain boundary.

[0039] (2) Construct a microscopic spectroscopy measurement system to test the luminescence behavior of the prepared samples. For example... Figure 3As shown, the pump uses a continuous-wave 532 nm laser, with near-field coupling achieved through a tapered optical fiber with a waist diameter of approximately 1 µm, injecting the light into the WGM mode of the LN microdisk. The coupling strength is controlled by adjusting the distance between the tapered fiber and the microdisk, and the pump power is gradually increased, with real-time monitoring of the microdisk's output spectrum and intensity changes. Figure 4 As shown, the tapered optical fiber emits near-infrared light after successful coupling with the microdisk. Comparative tests were conducted on undoped and Er-doped fibers. 3+ Room temperature photoluminescence (PL) spectra of perovskite thin film samples Figure 5 Under the same excitation intensity, a weak 1550 nm emission peak corresponding to Er was observed in the near-infrared PL spectrum of the doped sample. 3+ of 4 I 13 / 2 → 4 I 15 / 2 This phenomenon signifies an Er transition in the perovskite matrix. 3+ When stimulated, it can produce light emission in the telecommunications band, providing a possibility for the future development of 1550nm on-chip lasers.

[0040] Example 2 This embodiment provides a method for fabricating a laser on a gradient-doped perovskite / lithium niobate heterojunction, wherein: in step S21, the Er... 3+ Pb 2+ 10% of the total molar amount; Step S22 involves spin coating at 1500 rpm for 30 seconds to form a highly doped interface anchoring layer with a thickness of approximately 20-25 nm. In step S31, the main precursor solution with a conventional rare earth doping concentration is used to make Er... 3+ Pb 2+ 2% of the total molar amount; During spin coating in step S2, solvent interdiffusion occurs between the highly doped anchoring layer and the main precursor solution, Er 3+ Ions migrate toward the main gain layer under shear force, forming a continuous vertical concentration gradient from 10% at the interface to 2% at the film surface; The remaining operations are the same as in Example 1.

[0041] Example 3 This embodiment provides a method for fabricating a laser on a gradient-doped perovskite / lithium niobate heterojunction, wherein: in step S21, the Er... 3+ Pb 2+ 15% of the total molar amount; Step S22 involves spin coating at 1000 rpm for 30 seconds to form a highly doped interface anchoring layer with a thickness of approximately 45-50 nm. In step S31, the main precursor solution with a conventional rare earth doping concentration is used to make Er... 3+ Pb 2+ 2% of the total molar amount; During spin coating in step S2, solvent interdiffusion occurs between the highly doped anchoring layer and the main precursor solution, Er 3+ Ions migrate toward the main gain layer under shear force, forming a continuous vertical concentration gradient from 15% at the interface to 2% at the film surface; The remaining operations are the same as in Example 1.

[0042] Although the above embodiments use Er 3+ Doping, but the technical solution of this invention is also applicable to other rare earth ions, such as Nd. 3+ Yb 3+ or Tm 3+ These, among others, possess different energy level transitions, which can endow perovskite materials with luminescence capabilities at different wavelengths in the near-infrared range. For example, Nd... 3+ Doping may provide gain in the 900–1060 nm range, Tm 3+ Doping enables emission in both blue-green and near-infrared bands. The doping concentration can be adjusted as needed, but is generally controlled below 5% at cation sites to balance luminescence enhancement and crystal quality. When the doping concentration is too high, co-doping can be used for coordination (e.g., Er and Yb co-doping, utilizing Yb...). 3+ Sensitization Er 3+ This improves pump absorption efficiency.

[0043] Changes in perovskite material systems: Besides (NMA)2Fa n-1 Pb n I 3n+1 The method of this invention can be extended to other quasi-two-dimensional or three-dimensional perovskite materials. For example, replacing lead iodide with lead bromide or mixed halides can yield gain materials with tunable emission wavelengths from the visible to near-infrared range; organic spacer cations NMA can also be replaced with other long-chain or aromatic amines (e.g., BA-butylammonium, PEA-phenylethylamine, etc.) to change the number of layers and stability. Correspondingly, rare-earth doping can also be introduced into the precursors of these materials. Different perovskite materials may require adjustments to spin-coating and annealing conditions (e.g., temperature, time), but the overall preparation steps are similar. By selecting different material combinations, microcavity lasers in different wavelength bands from visible to near-infrared can be realized, further broadening the application scope of this invention.

[0044] Microcavity Structure Adjustment: This invention focuses on lithium niobate microdisk resonators, but similar effects can be achieved by integrating gain films onto other optical microcavities. For example, WGM microcavities such as lithium niobate microrings and microspheres can be used as gain coupling cavities. For planar integration, perovskite films can be deposited on lithium niobate waveguide resonators to form on-chip ring lasers. By optimizing the coating and coupling methods according to the microcavity type (e.g., adjusting the position of the tapered fiber), this invention can be applied to various heterogeneous integrated laser structures.

[0045] Process and Packaging Improvements: In the thin film fabrication process, for interface enhancement, in addition to plasma treatment, a nanometer-thick mesoporous SiO2 buffer layer can be sputtered onto the lithium niobate surface to improve mechanical adhesion and serve as a passivation layer. After device fabrication, a transparent protective coating (e.g., spin-coated PMMA or ALD-deposited ultrathin alumina layer) can be added to the perovskite thin film to prevent water and oxygen intrusion, thereby significantly improving the device's environmental stability. These alternative solutions can all be combined with the core ideas of this invention to achieve similar technical effects.

[0046] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0047] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for fabricating a gradient-doped perovskite / lithium niobate heterojunction on-chip laser, characterized in that: Specifically comprising the following steps: S1. Select a processed lithium niobate micro-disk chip, ultrasonic cleaning for 8-15 minutes, and then blow dry the surface moisture with high-purity nitrogen gas after cleaning; Pass argon plasma, and perform activation treatment at a power of 80-150 W for 5-15 minutes; S2. Prepare a high-rare earth doped precursor solution, so that the rare earth ions account for 10-15% of the total molar amount of metal cations in the perovskite; After magnetic stirring, filter through a 0.22 μm filter membrane; Take a small amount of the precursor solution and drop it on the surface of the treated lithium niobate micro-disk, and spin coat at a speed of 1000-1500 rpm for 25-40 seconds to form a high-doped interface anchoring layer; S3. Prepare a main precursor solution with a conventional rare earth doping concentration, so that the rare earth ions account for 2-5% of the total molar amount of metal cations in the perovskite; When the high-doped interface anchoring layer is not completely dried, add the main precursor solution dropwise and spin coat it with preset spin coating parameters to obtain a main gain layer; S4. After spin coating, immediately transfer to a hot plate filled with argon protective atmosphere, and perform a two-stage annealing program: the first stage is set at a temperature of 65-75℃, and the temperature is kept for 1-3 minutes; then the temperature is raised to 95-105℃, and the temperature is kept for 6-10 minutes; cool to room temperature to obtain a gradient-doped perovskite / lithium niobate heterojunction sheet laser.

2. The method of claim 1, wherein the method further comprises: depositing a first layer of a perovskite material on the substrate; depositing a second layer of a lithium niobate material on the first layer; and depositing a third layer of a perovskite material on the second layer. The specific method of ultrasonic cleaning in step S1 is: sequentially use deionized water, acetone, and anhydrous ethanol, and ultrasonic clean for 10 minutes at a power of 80-150 W; the purity of the high-purity nitrogen gas is ≥99.99%.

3. The method of claim 1, wherein the method further comprises: depositing a first layer of a perovskite material on the substrate; depositing a second layer of a lithium niobate material on the first layer; and depositing a third layer of a perovskite material on the second layer. The preparation method of the high-rare earth doped precursor solution in step S2 is: taking perovskite material as the main system, dissolving perovskite raw materials in a high-boiling point mixed solvent according to a preset molar ratio, and then adding rare earth compounds so that the rare earth ions account for 10-15% of the total molar amount of metal cations in the perovskite.

4. The method of claim 3, wherein the method further comprises: The perovskite material is selected from quasi-two-dimensional perovskite or three-dimensional perovskite; the perovskite raw materials include organic cation compounds and metal halides, the organic cation compounds are selected from at least one of N-methylacetamide iodine, formamidinium iodine, butylammonium salt, and phenethylammonium salt, and the metal halides are selected from at least one of lead iodide, lead bromide, and lead chloride; The high-boiling point mixed solvent is a mixed solvent prepared by mixing DMSO and GBL at a volume ratio of 1:

1.

5. The method of claim 3 or 4, wherein the method further comprises: said rare earth ions are selected from at least one of Er 3+ , Nd 3+ , Yb 3+ or Tm 3+ ; said rare earth compound is a chloride corresponding to the rare earth ion.

6. The method of claim 1, wherein the method further comprises: The preparation method of the main precursor solution with a conventional rare earth doping concentration is: taking perovskite material as the main system, dissolving perovskite raw materials in DMF according to a preset molar ratio, and then adding rare earth compounds so that the rare earth ions account for 2-5% of the total molar amount of metal cations in the perovskite; the perovskite raw materials are consistent with step S2.

7. The method of claim 1, wherein the method further comprises: depositing a first layer of a perovskite material on the substrate; depositing a second layer of a lithium niobate material on the first layer; and depositing a third layer of a perovskite material on the second layer. The preset spin coating parameters in step S3 are: spin coating speed of 4000-5000 rpm, and spin coating time of 30-60 seconds.

8. The method of claim 1, wherein the method further comprises: depositing a first layer of a perovskite material on the substrate; depositing a second layer of a lithium niobate material on the first layer; and depositing a third layer of a perovskite material on the second layer. The specific conditions of the two-stage annealing program in step S4 are: the first stage temperature is 70℃, and the temperature is kept for 2 minutes; the second stage temperature is 100℃, and the temperature is kept for 8 minutes.

9. The method of claim 1, wherein the method further comprises: depositing a first layer of a perovskite material on the substrate; depositing a second layer of a lithium niobate material on the first layer; and depositing a third layer of a perovskite material on the second layer. The thickness of the high-doped interface anchoring layer is 20-50 nm; the thickness of the main gain layer is 180-220 nm.

10. A graded-doped perovskite / lithium niobate heterojunction on-chip laser, characterized in that: The preparation method of the gradient-doped perovskite / lithium niobate heterojunction on-chip laser of claim 1 is adopted to prepare.

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