CN-121975524-A - Laser searching system based on rare earth-based light conversion material with core-shell structure

CN121975524ACN 121975524 ACN121975524 ACN 121975524ACN-121975524-A

Abstract

The application relates to the technical field of laser safety monitoring and defense, and discloses a laser searching system based on a rare earth-based light conversion material with a core-shell structure. The material comprises up-conversion nanocrystals with a core-shell structure, wherein the nanocrystals comprise a core layer which is a first fluoride material containing at least one or more rare earth ions and is used for absorbing light of a first wave band and up-converting. The middle shell layer coated on the outer side of the inner core layer is made of a second fluoride material containing rare earth ions. The outer shell layer coated on the outer side of the intermediate shell layer is made of a third fluoride material containing rare earth ions. The nanocrystalline material is configured to absorb low energy light of the first band of light and emit a second, higher energy band of light via an upconversion process. The application can convert invisible intrusion laser irradiation into the second wave band light which can be imaged and perform anomaly identification so as to realize high-sensitivity real-time detection and reliable early warning of the intrusion behavior of laser interception.

Inventors

WU JIANXUN
ZENG MIN
NI CHAO
YANG LIU
JIANG JIAN
LI JIANG
FU YIFEI
CAO LICHEN

Assignees

中国电力工程顾问集团华东电力设计院有限公司
湖北大学
莱伏特能源(上海)有限公司
星门建筑科技(上海)有限责任公司

Dates

Publication Date: 20260505
Application Date: 20260126

Claims (10)

1. The rare earth-based light conversion material is characterized by comprising up-conversion nanocrystals with a core-shell structure, wherein the nanocrystals comprise: The inner core layer is a first fluoride material containing at least one or more rare earth ions and is used for absorbing light of a first wave band and performing up-conversion; the middle shell layer is coated on the outer side of the inner core layer and is made of a second fluoride material containing rare earth ions; the outer shell layer is coated on the outer side of the middle shell layer and is made of a third fluoride material containing rare earth ions; the nanocrystalline material is configured to absorb low energy light of a first band of light and emit a second, higher energy band of light via an upconversion process.
2. The rare earth-based light conversion material according to claim 1, wherein the core layer is NaErF 4 :yb/Ce, and wherein the mole percentage of each rare earth ion in the core layer is 84-97.8 mol% of erbium ion (Er 3+ ), 0.2-1.0 mol% of cerium ion (Ce 3+ ), and 2-15 mol% of ytterbium ion (Yb 3+ ).
3. The rare earth-based light-converting material according to claim 2, wherein the method for producing the core layer comprises: a1. Dissolving the weighed rare earth chloride and sodium source in proportion in deionized water, adding a mixed solution of oleic acid and ethanol, and fully performing ultrasonic treatment until reactants are completely dissolved to form a rare earth-oleic acid complex; a2. dropwise adding NaF aqueous solution into the mixed solution obtained in the step a1, performing ultrasonic mixing, forming emulsion, and transferring to a high-pressure reaction kettle for reaction for 2h at 220 ℃; a3. after centrifugal washing, the mixture is dispersed in cyclohexane solvent to obtain kernel solution.
4. The rare earth-based light-converting material of claim 3, wherein the intermediate shell layer is NaYbF 4 and the outer shell layer is NaYF 4 , wherein B1. dissolving the weighed rare earth chloride and sodium source in proportion in deionized water, adding a mixed solution of oleic acid and ethanol, and fully performing ultrasonic treatment until reactants are completely dissolved to form a rare earth-oleic acid complex; b2. Adding the core solution into the rare earth-oleic acid complex obtained in the step b1, and performing ultrasonic dispersion to obtain a dispersion liquid; b3. dropwise adding NaF aqueous solution into the dispersion liquid obtained in the step b2, and carrying out ultrasonic mixing to form emulsion, and carrying out high-pressure reaction for 2h at 200 ℃; b4. And after centrifugal washing, dispersing in cyclohexane solvent to obtain core-shell solution with the intermediate layer coating the inner core.
5. The rare earth-based light-converting material of claim 4, wherein the cladding step of the outer shell layer comprises: c1. Dissolving the weighed rare earth chloride and sodium source in proportion in deionized water, adding a mixed solution of oleic acid and ethanol, and fully performing ultrasonic treatment until reactants are completely dissolved to form a rare earth-oleic acid complex; c2. Adding the core-shell solution obtained in b3 into the rare earth-oleic acid complex obtained in c1, and performing ultrasonic dispersion to obtain a dispersion; c3. Dropwise adding NaF aqueous solution into the dispersion liquid obtained in the step C2, and carrying out ultrasonic mixing to form emulsion, and carrying out high-pressure reaction for 2h at 180 ℃; c4. And after centrifugal washing, dispersing in cyclohexane solvent to obtain core-shell solution with shell coating the middle layer.
6. The preparation method of the functional layer is characterized by comprising the following steps: d1. Dispersing the nanocrystalline in the transparent polymer matrix, wherein the transparent polymer matrix is PMMA-silica sol coating liquid, the mass concentration of the nanocrystalline in the coating liquid is 10-50wt%, and uniformly dispersing the nanocrystalline through magnetic stirring and ultrasonic dispersion to form stable dispersion; d2. coating the dispersion liquid on the surface of a transparent substrate in a spin coating or blade coating mode, wherein the transparent substrate is glass or a flexible PET sheet; d3. Gradient heating and curing, namely performing gradient heating on the coated film; The obtained film can emit near infrared light with the wavelength of 980nm under 1550nm laser irradiation, the visible light transmittance is more than or equal to 80%, and the thickness is 50-600 mu m.
7. A laser eavesdropping defending system based on band conversion detection is characterized by comprising a band selective up-conversion detection composite structure, an optical detection module and a signal processing unit; the band-selective up-conversion detection composite structure comprises a first functional layer obtained by the preparation method of claim 6, wherein microstructure detection point units distributed in a regular array shape are arranged on the first functional layer, and the rare earth-based light conversion material of claim 5 is packaged in the microstructure detection point units; The optical detection module is arranged at one side or the peripheral position of the band selective up-conversion detection composite structure and is used for receiving the second band light generated by the microstructure detection point unit and forming a corresponding optical imaging signal; The signal processing unit is configured to perform feature extraction on the optical imaging signal to identify abnormal light emission of the microstructure detection point unit caused by light irradiation of the first wave band, thereby determining occurrence of a laser intrusion event and generating an alarm signal.
8. The system of claim 7, wherein the band-selective up-conversion detection composite structure comprises a cover protection layer, a functional layer, a transparent substrate and a protective shielding layer laminated in sequence; the protective cover is a transparent hard material configured to allow light to pass through and provide mechanical protection to the inside; the functional layer is covered on the transparent substrate, and the transparent substrate is configured to fix the cover protection layer and the protection shielding layer into a whole structure; the protective shielding layer is configured to reduce ambient stray light interference and enhance the exit directionality of the second band light toward the optical detection module.
9. The band-shift detection-based laser eavesdropping prevention system of claim 7, wherein said optical detection module comprises a CMOS or CCD camera and its front-end imaging enhancement optics including a field lens, focusing lens or beam expanding/shrinking optics to increase the collection efficiency and imaging signal-to-noise ratio of said second band light.
10. The laser eavesdropping defending method based on band conversion detection is characterized by comprising the following steps of: Providing a band-shift detection-based laser eavesdropping prevention system according to any one of claims 7-9; exposing the band-selective up-conversion detection composite structure to a monitored environment, and converting the light into second band light by the rare earth-based light conversion material encapsulated in the microstructure detection point unit when the microstructure detection point unit is irradiated with the first band light from the environment; Receiving the second wave band light emitted by the microstructure detection point unit through the optical detection module to generate a corresponding optical imaging signal; The signal processing unit performs feature extraction on the optical imaging signal to identify abnormal luminescence of the microstructure detection point unit caused by the light irradiation of the first wave band, so as to determine occurrence of a laser intrusion event and generate an alarm signal.

Description

Laser searching system based on rare earth-based light conversion material with core-shell structure Technical Field The application relates to the technical field of laser safety monitoring and defense, in particular to a laser searching system based on a rare earth-based light conversion material with a core-shell structure. Background In recent years, with the continuous development of laser eavesdropping and related active optical detection technologies, safety protection faces new challenges. High power infrared lasers, represented by 1550nm, are widely used in remote contactless eavesdropping, signal transmission and monitoring scenarios. The current mainstream protection technology mainly comprises: Physical isolation or optical film protection can only realize passive blocking, and real-time early warning and tracking of laser invasion are difficult to realize. The laser detection mainly depends on infrared detection devices such as InGaAs (indium gallium arsenide) focal plane arrays, but the detectors have the defects of high cost, low pixel density, high refrigeration requirement, large noise and the like, are not suitable for large-area and low-cost integration, and are easily interfered by environmental infrared stray light. The traditional rare earth up-conversion materials are mostly powder or block, cannot be coated on a transparent substrate in a large area and transparent and uniform manner to form a high-light-transmission film, and meanwhile visible light emission is not sufficiently inhibited, so that the detection position is easily exposed and the normal lighting function of the glass is affected. The prior art is difficult to meet the urgent requirements of real-time early warning of hidden, low-cost and large-area laser intrusion in the fields of military use, critical buildings, intelligent transportation and the like. Disclosure of Invention The application aims to provide a laser searching system based on a rare earth-based light conversion material with a core-shell structure, which can convert invisible invasion laser irradiation into second-band light capable of imaging and perform anomaly identification so as to realize high-sensitivity real-time detection and reliable early warning on laser eavesdropping invasion behaviors. The application discloses a rare earth-based light conversion material, which comprises up-conversion nanocrystals with a core-shell structure, wherein the nanocrystals comprise: The inner core layer is a first fluoride material containing at least one or more rare earth ions and is used for absorbing light of a first wave band and performing up-conversion; the middle shell layer is coated on the outer side of the inner core layer and is made of a second fluoride material containing rare earth ions; the outer shell layer is coated on the outer side of the middle shell layer and is made of a third fluoride material containing rare earth ions; the nanocrystalline material is configured to absorb low energy light of a first band of light and emit a second, higher energy band of light via an upconversion process. In a preferred example, the inner core layer is NaErF 4:Yb/Ce, wherein the mole percentage of each rare earth ion in the inner core layer is 84-97.8 mol% of erbium ion (Er 3+), 0.2-1.0 mol% of cerium ion (Ce 3+) and 2-15 mol% of ytterbium ion (Yb 3+). In a preferred embodiment, the method for preparing the core layer includes: a1. Dissolving the weighed rare earth chloride and sodium source in proportion in deionized water, adding a mixed solution of oleic acid and ethanol, and fully performing ultrasonic treatment until reactants are completely dissolved to form a rare earth-oleic acid complex; a2. dropwise adding NaF aqueous solution into the mixed solution obtained in the step a1, performing ultrasonic mixing, forming emulsion, and transferring to a high-pressure reaction kettle for reaction for 2h at 220 ℃; a3. after centrifugal washing, the mixture is dispersed in cyclohexane solvent to obtain kernel solution. In a preferred embodiment, the rare earth chloride is ErCl 3、YbCl3、CeCl3 and the sodium source is NaOH. In a preferred embodiment, the intermediate shell layer is NaYbF 4 and the outer shell layer is NaYF 4. In a preferred embodiment, in a1, the mole fraction of each rare earth ion in the rare earth chloride satisfies: 80-98 mol%, preferably 84-97.8 mol% of Er 3+; 0.1 to 2.0mol%, preferably 0.2 to 1.0mol% of Ce 3+; 1-20mol%, preferably 2-15mol% of Yb 3+; and the total mole fraction of the rare earth ions is 100mol%; the total concentration of the rare earth ions is 0.05-0.30 mol/L, preferably 0.10-0.20 mol/L; The molar ratio Na +:RE3+ of the sodium source to the rare earth ions is 1.0-3.0:1, preferably 1.5-2.5:1; the molar ratio OA of the oleic acid to the rare earth ions is RE 3+ of 4-12:1, preferably 6-10:1; the volume ratio of oleic acid to ethanol is 1 (1-5), preferably 1 (2-4). B1. dissolving the weighed rare earth chloride and sodium