A visible light transparent nonlinear laser protection light window based on one-dimensional photonic crystal

Abstract

This invention discloses a visible light transparent nonlinear laser protection window based on a one-dimensional photonic crystal. The window is constructed by a nonlinear laser protection structure disposed on the surface of the transparent window. This nonlinear laser protection structure is a one-dimensional photonic crystal composed of three media: TiO2, SiO2, and LiNbO3. Let TiO2, SiO2, and LiNbO3 be A, B, and C, respectively. Then the structure of the photonic crystal is (AB). N C(BA) N Let N be the number of repetition periods of the AB medium pair, and let λ be the laser protection wavelength. The thicknesses of medium layers A, B, and C are λ / 4, λ / 4, and λ / 2, respectively. The thicknesses of individual medium layers A, B, and C suitable for 1064nm laser protection are 112.7nm, 180.9nm, and 240.7nm, respectively. This invention can be effectively used for 1064nm wavelength laser protection windows, achieving high transmittance for weak light and high attenuation rate for strong light, while simultaneously achieving high transparency in the visible light 400-780nm band.

Description

Technical Field

[0001] This invention relates to the field of photonic crystals and nonlinear laser protection, specifically to a visible light transparent one-dimensional photonic crystal laser protection window with nonlinear transmittance. It can be applied to nonlinear laser protection that requires high transmittance for weak 1064nm laser light and high attenuation rate for strong light light, while also requiring high transmittance in the 400-780nm visible light band. Background Technology

[0002] With the widespread application of laser technology in industry, scientific research, and medicine, the demand for laser protection is increasing. This is because intense laser irradiation can cause irreversible damage to the human eye and various optoelectronic devices. Therefore, it is necessary to restrict intense lasers, but for lower-power lasers, such as those used for signal detection, no restrictions are necessary. Taking the commonly used 1064nm laser as an example, it can harm personnel and equipment under intense light, but can also be used for optoelectronic detection and information transmission under weak light. Furthermore, in some aerospace and other fields, not only laser protection is required, but also high transmittance in the 400-780nm visible light band. Therefore, it is necessary to develop a visible-light-transparent laser protection structure that can flexibly adjust the transmittance under different light intensity conditions to achieve visible-light transparency.

[0003] Currently, nonlinear laser protection methods are mainly based on optical effects such as nonlinear absorption, scattering, and refraction. However, many challenges remain, requiring further research and innovation. Antisaturation absorption is a common nonlinear absorption mechanism used to limit laser intensity; however, its stability limits its application. Laser confinement based on nonlinear scattering principles has a low output amplitude but a high confinement threshold, making it difficult to simultaneously achieve high transmittance in weak light and high attenuation in strong light. Laser confinement based on nonlinear refraction principles has a low confinement threshold, but its structural complexity in practical applications is high. Therefore, there is a need to find more effective, stable, and controllable laser protection solutions to meet the needs of various application scenarios.

[0004] Patent 202010900828.8 discloses a laser protective coating and its preparation method. The laser protective coating comprises, from the inside out, a zinc-immersed layer, a Ni / n-Al2O3 electroplated layer, and a Ni / n-Al2O3 sprayed layer, and can resist lasers with a power of 1 kW / cm². 2 Laser 10s, 600W / cm 2 The laser irradiation lasts for 100 seconds. However, this patent does not have optical transmittance, and low-power lasers cannot pass through it.

[0005] Patent 202211523321.0 discloses a method for preparing an intelligent laser protective coating material. It uses a V₂O₅ ceramic target (99.90% purity) and heat-treats the prepared sample in a tube furnace with effectively controlled atmosphere and temperature to ultimately obtain a vanadium oxide laser protective film. While the vanadium oxide laser protective film prepared by this invention provides different levels of protection against lasers of varying intensities, it is opaque in the visible light band, and the method of controlling light transmittance through temperature is difficult to manage.

[0006] Patent 202211399039.6 provides a colored nanofilm structure with protective function. The film structure is MNM', which is an asymmetric structure. Here, M represents a metallic reflective material layer, N represents a dielectric-enhanced reflective structure, and M' represents a structural color saturation control material layer. While this invention can achieve protection against high-power lasers and allow visible light transmission, it cannot achieve transmission of low-power lasers.

[0007] Patent 202310481529.9 describes the preparation of laser protective glass using borosilicate, comprising the following components: SiO2 35-47%, Al2O3 1-3%, B2O3 9-13wt%, Na2O 7-10wt%, CaO 3-5wt%, ZnO 3-4wt%, ZrO2 0.5-1.5wt%, Er2O3 8-20wt%, and Sm2O3 9-16wt%. This patent does not possess good optical transmittance and cannot meet the requirements for low-power laser transmission.

[0008] Currently, patents 202210752787.1, 202310535255.7, 202110136570.3 and 202310419151.X concerning nonlinear laser protection only achieve protection against high-power lasers. However, none of these patents can simultaneously possess the functions of high transmittance in the visible light band and low-power laser transmittance.

[0009] In summary, existing technologies cannot simultaneously achieve high transmittance in the visible light band, low-power laser transmission, and high-power laser protection. To address these shortcomings, this invention designs a novel one-dimensional photonic crystal protection structure, utilizing TiO2 and SiO2 linear media and LiNbO3 nonlinear media as the periodic dielectric layer and defect layer of the photonic crystal, respectively. By designing the arrangement, thickness, and number of repetition periods of the TiO2, SiO2, and LiNbO3 dielectric layers, high attenuation of strong lasers and high transmittance of weak lasers are achieved, while simultaneously achieving high transmittance in the visible light band. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a nonlinear laser protection structure based on a one-dimensional photonic crystal that can achieve high attenuation of strong light and high transmission of weak light for 1064nm laser, while simultaneously achieving transparency in the visible light band.

[0011] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0012] A visible-light transparent nonlinear laser shielding window based on a one-dimensional photonic crystal is provided, comprising a nonlinear laser shielding structure disposed on the surface of the transparent window. The nonlinear laser shielding structure is characterized by being a one-dimensional photonic crystal composed of TiO2, SiO2, and LiNbO3 media arranged in a specific configuration. Let TiO2, SiO2, and LiNbO3 be A, B, and C, respectively, then the structural arrangement of the one-dimensional photonic crystal is (AB). N C(BA) N N is the number of repetition periods of the AB medium pair, the laser protection wavelength is 1064nm, and the optical thicknesses of the medium layers A, B, and C are 266nm, 266nm, and 532nm, respectively.

[0013] A visible-light transparent nonlinear laser protective window based on a one-dimensional photonic crystal is characterized by the following: at a 1064 nm laser wavelength, the refractive index of the dielectric TiO2 is 2.36 with an extinction coefficient of 0, the refractive index of the dielectric SiO2 is 1.47 with an extinction coefficient of 0, and the dielectric layer LiNbO3 is a defect layer with a linear refractive index of 2.21 and a nonlinear refractive index coefficient of 1.44 × 10⁻⁶. -11 cm 2 / W, with an extinction coefficient of 0, and actual thicknesses of the dielectric layers TiO2, SiO2, and LiNbO3 of 112.7 nm, 180.9 nm, and 240.7 nm, respectively.

[0014] In the embodiment, when the number of repetition cycles N=3, the energy density of the 1064nm laser is less than 15.02mJ / cm². 2 At that time, the nonlinear laser protection structure exhibited a transmittance of 96.18% for 1064nm laser light, with a laser protection threshold of 60.16mJ / cm². 2 When the laser energy density is greater than 117.28 mJ / cm² 2 At that time, the transmittance of its 1064nm laser was 9.23%. In the visible light 400-780nm band, the average transmittance was 76.72%.

[0015] In the embodiment, when the number of repetition cycles N=4, the energy density of the 1064nm laser is less than 9.58mJ / cm². 2 At that time, the nonlinear laser protection structure exhibited a transmittance of 93.19% for 1064nm laser light, with a laser protection threshold of 55.75mJ / cm².2 When the laser energy density is greater than 103.18 mJ / cm 2 At that time, the transmittance of its 1064nm laser was 6.07%. In the visible light 400-780nm band, the average transmittance was 77.44%.

[0016] In the embodiment, when the number of repetition cycles N = 5, the energy density of the 1064nm laser is less than 4.49mJ / cm². 2 At that time, the nonlinear laser protection structure exhibited a transmittance of 80.25% for 1064nm laser light, with a laser protection threshold of 52.69 mJ / cm². 2 When the laser energy density is greater than 96.31 mJ / cm 2 At that time, the transmittance of its 1064nm laser was 4.2%. In the visible light 400-780nm band, the average transmittance was 76.93%.

[0017] Compared with the prior art, the advantages of this invention are:

[0018] (1) The designed one-dimensional photonic crystal periodic protection structure can generate bandgap and passband structures, selectively blocking and allowing light of specific wavelengths to propagate, thus achieving effective laser protection and transparency in the visible light band.

[0019] (2) By utilizing the localized optical field characteristics of a one-dimensional photonic crystal, the electric field intensity at the defect layer LiNbO3 is enhanced, the nonlinear effect is improved, and thus the laser protection threshold is reduced.

[0020] (3) The one-dimensional photonic crystal periodic protection structure can be designed as needed to adapt to different wavelengths of lasers, which makes them suitable for protecting against various lasers of different wavelengths, including visible light, infrared light and ultraviolet light.

[0021] (4) The one-dimensional photonic crystal periodic protective structure is lightweight and thin, making it suitable for applications such as portable laser protection equipment and eye protection goggles. Compared with traditional laser protection materials, the structure of this invention is simpler in design, more stable in physical properties than liquid substances, and the structure of this invention is transparent to visible light.

[0022] In summary, this invention can be effectively used in 1064nm wavelength laser protection systems to achieve high transmittance for weak light and high attenuation rate for strong light, while simultaneously achieving transparency in the visible light band. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0024] Figure 1 This is a schematic diagram of a visible light transparent nonlinear laser protection window based on a one-dimensional photonic crystal.

[0025] Figure 2 This is the electric field distribution diagram when the repetition period N=3.

[0026] Figure 3 This is the electric field distribution diagram when the repetition period N=4.

[0027] Figure 4 This is the electric field distribution diagram when the repetition period N=5.

[0028] Figure 5 Broadband transmittance diagrams are shown for repetition periods N=3, N=4, and N=5.

[0029] Figure 6 The transmittance diagrams are shown near 1064 nm for repetition periods N=3, N=4, and N=5.

[0030] Figure 7 This is a graph showing the change in transmittance of light at a wavelength of 1064 nm as a function of incident light energy density. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. These described embodiments are merely a part of the embodiments of the present invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0032] This invention addresses laser protection systems at a wavelength of 1064 nm by designing a one-dimensional photonic crystal laser protection window with transparency and nonlinear transmittance in the visible light band. Medium A is selected as TiO2 (titanium dioxide) with a refractive index of 2.36 and an extinction coefficient of 0. Medium B is selected as SiO2 (silicon dioxide) with a refractive index of 1.47 and an extinction coefficient of 0. The defect layer C is selected as LiNbO3 (lithium niobate) with a linear refractive index of 2.21 and a nonlinear refractive index coefficient of 1.44 × 10⁻⁶. -11 cm 2 / W, with an extinction coefficient of 0. The thicknesses of dielectric layers A, B, and C are 112.7 nm, 180.9 nm, and 240.7 nm, respectively.

[0033] When the incident laser wavelength is 1064nm, at a low incident laser energy density, this wavelength is exactly located at the defect state position, resulting in high transmittance. When the incident laser energy density increases, the defect state position shifts, and the transmittance at 1064nm decreases, achieving the laser protection effect at a high incident laser energy density.

[0034] For the photonic crystal laser protection structure of the present invention, the electric field distribution of the structure was obtained through simulation using the finite-difference time-domain method. By changing the incident light energy density, the relationship between the photonic crystal transmittance and the incident light energy density was obtained. Figures 2 to 4 As shown, the defect mode field distribution of the structure of the present invention when N=3, N=4, and N=5 can be seen. When N=3, the electric field intensity is enhanced by 10.3 times in the photonic crystal defect layer; when N=4, the electric field intensity is enhanced by 25.9 times; and when N=5, the electric field intensity is enhanced by 53.7 times. The enhanced electric field is conducive to generating nonlinear effects.

[0035] Figure 5 and Figure 6 This is a transmittance-wavelength relationship diagram for the structure of this invention. In the visible light 400-780nm band, the average transmittance is 76.72% when the number of repetition cycles N=3; 77.44% when the number of repetition cycles N=4; and 76.93% when the number of repetition cycles N=5, achieving high transmittance in the visible light band. At a wavelength of 1064nm, the transmittance is 96.18% when the number of repetition cycles N=3; 93.19% when the number of repetition cycles N=4; and 80.25% when the number of repetition cycles N=5.

[0036] like Figure 7 As shown, the relationship between transmittance and incident light energy density is obtained by changing the incident laser energy density. It can be seen that when the number of repetition cycles N = 3, the transmittance is significantly lower than 15.02 mJ / cm². 2 The laser transmittance is 96.18%, and the laser protection threshold is 60.16 mJ / cm². 2 When the laser energy density is greater than 117.28 mJ / cm² 2 At that time, the laser transmittance was 9.23%. When the number of repetition cycles N = 4, the laser energy density was less than 9.58 mJ / cm². 2 At that time, the laser transmittance was 93.19%, and the laser protection threshold was 55.75 mJ / cm². 2 When the laser energy density is greater than 103.18 mJ / cm2 At that time, the laser transmittance was 6.07%. When the number of repetition cycles N = 5, the laser energy density was less than 4.49 mJ / cm². 2 At that time, the laser transmittance was 80.25%, and the laser protection threshold was 52.69 mJ / cm². 2 When the laser energy density is greater than 96.31 mJ / cm 2 At that time, the transmittance was 4.2%.

Claims

1. A visible light transparent nonlinear laser protection window based on a one-dimensional photonic crystal, comprising a nonlinear laser protection structure disposed on the surface of the transparent window, characterized in that: The nonlinear laser protection structure is composed of one-dimensional photonic crystal arranged by three mediums of TiO2, SiO2 and LiNbO3, and TiO2, SiO2 and LiNbO3 are respectively A, B and C, the structure arrangement of the one-dimensional photonic crystal is (AB) N C(BA) N , N is the repetition period number of AB medium pair, the laser protection wavelength is 1064nm, and the optical thickness of single medium layer A, B and C is respectively 266nm, 266nm and 532nm.

2. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window of claim 1, wherein: At 1064nm laser, the refractive index of medium TiO2 is 2.36, the extinction coefficient is 0, the refractive index of medium SiO2 is 1.47, the extinction coefficient is 0, the medium layer LiNbO3 is a defect layer, the linear refractive index is 2.21, the nonlinear refractive index coefficient is 1.44×10 -11 cm 2 / W, the extinction coefficient is 0, the actual thickness of a single medium layer TiO2, SiO2 and LiNbO3 is 112.7nm, 180.9nm and 240.7nm respectively.

3. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window of claim 1, wherein: When the number of repetition cycles N = 3, when the 1064nm laser energy density is less than 15.02mJ / cm 2 , the transmittance of the nonlinear laser protection structure to 1064nm laser is 96.18%, and the laser protection threshold is 60.16mJ / cm 2 When the laser energy density is greater than 117.28mJ / cm 2 , the transmittance of 1064nm laser is 9.23%.

4. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window of claim 1, wherein: When the number of repeating periods N is 3, the average transmittance in the visible light 400-780 nm band is 76.72%.

5. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window of claim 1, wherein: When the number of repetition cycles N = 4, when the 1064nm laser energy density is less than 9.58mJ / cm 2 , the transmittance of the nonlinear laser protection structure to 1064nm laser is 93.19%, and the laser protection threshold is 55.75mJ / cm 2 When the laser energy density is greater than 103.18mJ / cm 2 , the transmittance of 1064nm laser is 6.07%.

6. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window of claim 1, wherein: When the number of repeating periods N is 4, the average transmittance in the visible light 400-780 nm band is 77.44%.

7. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window according to claim 1, characterized in that: When the number of repetition cycles N = 5, when the 1064nm laser energy density is less than 4.49mJ / cm 2 , the transmittance of the nonlinear laser protection structure to 1064nm laser is 80.25%, and the laser protection threshold is 52.69mJ / cm 2 When the laser energy density is greater than 96.31mJ / cm 2 , the transmittance of 1064nm laser is 4.2%.

8. The one-dimensional photonic crystal based visible light transparent nonlinear laser protection window according to claim 1, characterized in that: When the number of repeating periods N is 5, the average transmittance in the visible light 400-780 nm band is 76.93%.

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