Laser pulse protection cladding based on nonlinear optical effect

Abstract

This invention discloses a laser pulse protective cladding based on nonlinear optical effects. Along the laser transmission direction, it sequentially comprises a first homogeneous dielectric layer, a first nonlinear absorbing dielectric layer, and a second homogeneous dielectric layer, wherein the dielectric constant of the first nonlinear absorbing dielectric layer is greater than that of the first and second homogeneous dielectric layers; or, along the laser transmission direction, it sequentially comprises at least two stacked structural units, each stacked structural unit comprising a homogeneous dielectric layer and a nonlinear absorbing dielectric layer; or, along the laser transmission direction, it sequentially comprises a third homogeneous dielectric layer and at least two reflective structural units, each reflective structural unit comprising a homogeneous dielectric layer and a nonlinear absorbing dielectric layer. The embodiments of this invention can reduce the harm of high-intensity lasers to people or objects, providing a laser protection measure that can be widely applied in the field of laser application technology.

Description

Technical Field

[0001] This invention relates to the field of laser application technology, and in particular to a laser pulse protective cladding based on nonlinear optical effects. Background Technology

[0002] Lasers are widely used in industry, medicine, scientific research, and military fields due to their high-energy characteristics. However, the potential hazards they pose cannot be ignored. High-intensity lasers can easily damage the eyes and skin, and may burn through or destroy equipment pipes, wires, and sensing components, leading to equipment damage or mechanical accidents. Therefore, appropriate laser protection measures must be taken to ensure personal safety and equipment protection. Summary of the Invention

[0003] In view of this, in order to solve one of the above problems, the purpose of this invention is to provide a laser pulse protective cladding based on nonlinear optical effects, which can reduce the damage of high-intensity lasers to people or objects and provide a laser protection measure.

[0004] On one hand, embodiments of the present invention provide a laser pulse protective cladding based on nonlinear optical effects, comprising, in sequence along the laser transmission direction, a first uniform dielectric layer, a first nonlinear absorbing dielectric layer, and a second uniform dielectric layer; wherein, the dielectric constant of the first nonlinear absorbing dielectric layer is greater than the dielectric constant of the first uniform dielectric layer, and the dielectric constant of the first nonlinear absorbing dielectric layer is greater than the dielectric constant of the second uniform dielectric layer; the dielectric constant of the first nonlinear absorbing dielectric layer satisfies a preset nonlinear correlation requirement.

[0005] Optionally, the thickness of the first nonlinear absorption medium layer is determined according to the wavelength of the incident laser pulse.

[0006] Optionally, the laser pulse protective cladding further includes a first metal layer disposed between the first nonlinear absorption medium layer and the second uniform medium layer.

[0007] Optionally, the first metal layer is determined according to the wavelength of the incident laser pulse.

[0008] On the other hand, embodiments of the present invention provide a laser pulse protective cladding based on nonlinear optical effects, comprising at least two stacked structural units sequentially along the laser transmission direction. Each stacked structural unit includes a uniform dielectric layer and a nonlinear absorption dielectric layer, the thickness of which is determined according to the wavelength of the incident laser pulse.

[0009] On the other hand, embodiments of the present invention provide a laser pulse protective cladding based on nonlinear optical effects, which includes a third uniform dielectric layer and at least two reflective structural units in sequence along the laser transmission direction. Each reflective structural unit includes a uniform dielectric layer and a nonlinear absorbing dielectric layer, and the thickness, dielectric constant and / or nonlinear response parameters of the nonlinear absorbing dielectric layer in each reflective structural unit are different.

[0010] Optionally, each of the reflective structural units further includes a metal layer disposed after the nonlinear absorption medium layer along the laser transmission direction.

[0011] Optionally, the thickness of the metal layer ranges from 0.1 to 0.2 micrometers.

[0012] Optionally, the thickness of the reflective structural unit ranges from 0.2 to 1.5 micrometers.

[0013] Optionally, the thickness and dielectric constant of the uniform dielectric layer in the reflective structural unit are determined based on the nonlinear absorption dielectric layer.

[0014] The implementation of this invention provides the following beneficial effects: The laser pulse protective cladding based on nonlinear optical effects includes one or more layers of nonlinear absorbing medium. The nonlinear absorbing medium possesses unique optical properties; its optical response is not proportional to illuminance. As the light intensity varies, the refractive index, extinction coefficient, and other properties of the nonlinear absorbing medium change. The reflection phenomenon of laser light on the surface of a non-uniform medium material is particularly significant at the boundary between two media, with the reflection phenomenon at the boundary between the nonlinear absorbing medium layer and the uniform medium layer being particularly pronounced. Utilizing the optical principle that the reflectivity of the nonlinear absorbing medium layer increases with the laser pulse intensity, and the reflection at the boundary, high-intensity laser pulses are reflected, reducing the harm of high-intensity lasers to people or objects, thus providing a laser protection measure. Attached Figure Description

[0015] Figure 1 This is a transmission model of a laser pulse through two medium boundaries provided in an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of a laser pulse protective cladding based on nonlinear optical effects provided in an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of another laser pulse protective cladding structure based on nonlinear optical effects provided in an embodiment of the present invention;

[0018] Figure 4This is a schematic diagram of another laser pulse protective cladding structure based on nonlinear optical effects provided in an embodiment of the present invention;

[0019] Figure 5 This is a simulation effect diagram provided by an embodiment of the present invention;

[0020] Figure 6 This is a schematic diagram of another laser pulse protective cladding structure based on nonlinear optical effects provided in an embodiment of the present invention;

[0021] Figure 7 This is a schematic diagram of another laser pulse protective cladding structure based on nonlinear optical effects provided in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0023] The protective principle of laser pulse shielding is based on the reflection phenomenon of laser light on the surface of a non-uniform dielectric material. (See [reference needed]) Figure 1 Let M1 represent the incident laser pulse, M2 represent the propagating laser pulse, M3 represent the reflected laser pulse, ε1 represent the propagation medium, and ε2 represent the nonlinear absorbing medium. Reflection is particularly pronounced at the boundary between two media. Reflection of weaker laser pulses is governed by the well-known Fresnel law. When laser radiation is incident perpendicularly on the boundary between two media (where the second medium can absorb the laser radiation energy), the reflection coefficient can be written as follows.

[0024]

[0025] Where n is the relative refractive index of the second medium (e.g., fused silica), and K is the extinction coefficient of the second medium. This formula applies to low-intensity laser beams.

[0026] Nonlinear absorbing media possess unique optical properties; their optical response is not proportional to illuminance. With varying light intensity, the refractive index, extinction coefficient, and other properties of the nonlinear absorbing medium change. In this embodiment of the invention, a nonlinear absorbing medium is used as the second medium. If the intensity of the incident laser pulse increases with time I(t), the refractive index and extinction coefficient of the second medium change with time, n = n(I(t)), κ = κ(I(t)). Therefore, the reflection coefficient will change accordingly, R = R(I(t)). If the nonlinear absorption of the medium or its refractive index increases with the laser pulse power density, it can lead to an increase in the reflection coefficient at the boundary between the two media. This effect can limit the power density of the laser pulse passing through the boundary between the two regions. When the intensity of the incident pulse increases, the laser radiation will cause longitudinal inhomogeneity along its propagation direction in the medium. This inhomogeneity leads to the reflection of the laser radiation, reducing the radiation intensity transmitted through the medium, thereby achieving a laser protection effect.

[0027] See Figure 2 The arrow indicates the direction of laser pulse propagation. This embodiment of the invention provides a laser pulse protective cladding based on nonlinear optical effects, which sequentially includes a first uniform dielectric layer (with a dielectric constant of ε) along the laser propagation direction. 11 ), the first nonlinear absorbing dielectric layer (dielectric constant ε) 12 ) and the second uniform dielectric layer (with a dielectric constant of ε) 13 ); wherein, the dielectric constant of the first nonlinear absorbing dielectric layer is greater than the dielectric constant of the first uniform dielectric layer, and the dielectric constant of the first nonlinear absorbing dielectric layer is greater than the dielectric constant of the second uniform dielectric layer; the dielectric constant of the first nonlinear absorbing dielectric layer satisfies the preset nonlinear correlation requirements.

[0028] Specifically, in one particular embodiment, a single nonlinear absorbing dielectric layer can be used to protect the device. The first nonlinear absorbing dielectric layer is placed with a dielectric constant close to 1 (ε). 11 =ε 13 In a homogeneous medium with a dielectric constant ε ≈ 1), the dielectric constant is... 12 >ε 11 , ε 12 >ε 13 Simultaneously, the dielectric constant of the first nonlinear absorbing dielectric layer should satisfy the nonlinear correlation ε 12 +Δε 12 (I(t)), the material of the first nonlinear absorption medium layer includes fused silica, semiconductor, etc.

[0029] Optionally, the thickness of the first nonlinear absorption medium layer is determined according to the wavelength of the incident laser pulse.

[0030] To achieve maximum protection efficiency, the thickness h of the first nonlinear absorbing medium layer should be approximately equal to λ0 / 4, where λ0 is the wavelength of the incident laser pulse to be protected. It is important to note that laser pulses with intensity varying over time can alter the optical thickness of the nonlinear layer, disrupting optimal reflection conditions.

[0031] Optionally, see Figure 3 The laser pulse protective cladding further includes a first metal layer (S1), which is disposed between the first nonlinear absorption medium layer and the second uniform medium layer.

[0032] Optionally, the first metal layer (S1) is determined according to the wavelength of the incident laser pulse.

[0033] In one specific embodiment, a metal layer can be added to the surface of the protective layer to mitigate the problems caused by variations in optical thickness. The metal layer is located on the side of the protective layer closest to the protected device, and its thickness is h. m Approximately 2 / 3λ0. The addition of the metal layer increases the reflectivity at both interfaces. To avoid the laser energy melting the metal layer, a metal with a high melting point, such as tungsten, must be used.

[0034] Single-layer nonlinear protection structures are simple in structure and have good protection effect, but their disadvantage is that they can only protect against laser pulses in a specific wavelength range based on the thickness of the dielectric layer; at the same time, changes in the intensity of the laser pulse may change the optical thickness of the nonlinear layer, resulting in the failure to achieve the optimal conditions for reflection.

[0035] See Figure 4 This invention provides a laser pulse protective cladding based on nonlinear optical effects, comprising at least two stacked structural units along the laser transmission direction. Each stacked structural unit includes a uniform dielectric layer (ε1) and a nonlinear absorption dielectric layer (ε2). The thicknesses of the uniform dielectric layer (ε1) and the nonlinear absorption dielectric layer (ε2) are determined according to the wavelength of the incident laser pulse.

[0036] To protect equipment from the effects of laser pulses of different wavelengths, it is possible to... Figure 4 The multilayer structure shown is composed of two types of dielectric layer arrays with different optical properties, having dielectric constants ε1 and ε2, respectively. The thicknesses d1 and d2 of the two layers satisfy the following relationship:

[0037]

[0038] λ Str For the laser pulse frequency that this structure can effectively protect against, based on its wavelength variation, the following conditions must be met:

[0039]

[0040] c is the speed of light in a vacuum, v str To protect the frequency of the structure.

[0041] The reflectivity of laser energy is defined as the ratio of the carrier frequency of its propagating wave packet (or the wavelength of the light pulse) to the frequency of the structure (or the wavelength of the structure).

[0042]

[0043] In the formula, ω is the angular frequency of the incident light. str These are the angular frequencies of the protective structure and v, respectively, which represent the frequency of the incident light. str Here, λ0 represents the frequency of the protective structure, λs represents the wavelength of the incident light, and λ0 represents the wavelength of the incident light. tr These represent the wavelengths of the protective structure.

[0044] See Figure 5 , Figure 5 The simulation conditions for (a) are: d1 = 0.2; d2 = 0.6; ε1 = 5.29; ε2 = 1; N str =10 and λ str =1.06. Figure 5 The simulation conditions in (b) are: d1 = 0.6; d2 = 0.2; ε1 = 4; ε2 = 1; N str =10 and λ str =1.4 (thickness in micrometers). The relationship between the reflection coefficient and the incident pulse wavelength of the multilayer array structure, obtained through computer simulation, is derived from... Figure 5 It is known that the maximum reflectivity of laser energy within various laser pulse wavelength (frequency) ranges is close to 1; at the same time, the laser pulse wavelength (frequency) that can be reflected significantly is related to the thickness of the dielectric layer and the dielectric constant of the protective layer structure.

[0045] It should be noted that both types of dielectric layer array structures exhibit high reflectivity for laser pulses of specific frequencies. Furthermore, the frequency range of reflection can be altered by changing the thickness and dielectric constant of the dielectric layer, enabling highly efficient reflection of laser pulses across any frequency range. The multi-layer array structure makes the optimal reflection conditions less susceptible to disruption, resulting in more stable protection. The disadvantage is that, limited by the structure's own frequency, it is impossible to achieve high reflection of any light frequency simultaneously using a single structure. Additionally, from... Figure 5 The simulation results show that the frequency range can be easily shifted by changing the thickness and dielectric constant of the dielectric layer.

[0046] See Figure 6 This invention provides a laser pulse protective cladding based on nonlinear optical effects, comprising a third uniform dielectric layer (ε) sequentially along the laser transmission direction. 21The reflective structure includes at least two reflective structural units, each comprising a uniform dielectric layer and a nonlinear absorbing dielectric layer, wherein the thickness, dielectric constant, and / or nonlinear response parameters of the nonlinear absorbing dielectric layer in each reflective structural unit are different.

[0047] See Figure 6 The first reflective structural unit includes a nonlinear absorbing dielectric layer I2 and a nonlinear absorbing dielectric layer I4. The thickness, dielectric constant, and / or nonlinear response parameters of the nonlinear absorbing dielectric layer in each reflective structural unit are different. The dielectric constant of the uniform dielectric layer in each reflective structural unit may be equal or unequal (e.g., ε). 23 Therefore, nonlinear layers with different thicknesses, dielectric constants, and nonlinear response parameters can be combined into a disordered structure array to achieve high reflection of any light frequency over a wide range.

[0048] See Figure 7 Each of the aforementioned reflective structural units further includes a metal layer disposed after the nonlinear absorption medium layer along the laser transmission direction.

[0049] Optionally, the thickness of the metal layer ranges from 0.1 to 0.2 micrometers.

[0050] Figure 7 In the diagram, A1 represents the homogeneous dielectric layer of the first reflective structural unit, A2 represents the nonlinear absorbing dielectric layer of the first reflective structural unit, and S1 represents the metal layer of the first reflective structural unit. Adding a metal layer with a thickness of approximately 0.1–0.2 micrometers to each reflective structural unit enhances the reflectivity of the layered structure. Because of the use of nonlinear layers with different thicknesses, dielectric constants, and nonlinear response parameters, the structure's frequency range is broad, achieving high reflectivity for any light frequency over a wide range. Due to the faster cooling of the multilayer dielectric, this structure can also be used normally in vacuum and atmospheric environments.

[0051] Optionally, the thickness of the reflective structural unit ranges from 0.2 to 1.5 micrometers.

[0052] It should be noted that the number of layers in the multi-layer structure of the laser pulse protective cladding varies from 20 to 100, with each layer having a thickness of 0.2-1.5 micrometers and a total thickness of no more than 0.1-0.3 millimeters.

[0053] Optionally, the thickness and dielectric constant of the uniform dielectric layer in the reflective structural unit are determined based on the nonlinear absorption dielectric layer.

[0054] In the reflective structural unit, the thickness and dielectric constant of the homogeneous dielectric layer are determined based on the nonlinear absorbing dielectric layer. When the parameters of the nonlinear absorbing dielectric layer in the reflective structural unit are different, the parameters of the corresponding homogeneous dielectric layer are also different.

[0055] The implementation of this invention provides the following beneficial effects: The laser pulse protective cladding based on nonlinear optical effects includes one or more layers of nonlinear absorbing medium. The nonlinear absorbing medium possesses unique optical properties; its optical response is not proportional to illuminance. As the light intensity varies, the refractive index, extinction coefficient, and other properties of the nonlinear absorbing medium change. The reflection phenomenon of laser light on the surface of a non-uniform medium material is particularly significant at the boundary between two media, with the reflection phenomenon at the boundary between the nonlinear absorbing medium layer and the uniform medium layer being particularly pronounced. Utilizing the optical principle that the reflectivity of the nonlinear absorbing medium layer increases with the laser pulse intensity, and the reflection at the boundary, high-intensity laser pulses are reflected, reducing the harm of high-intensity lasers to people or objects, thus providing a laser protection measure.

[0056] The nonlinear layer in this invention embodiment can be manufactured using materials such as fused silica or semiconductors, while the metal reflection enhancement layer can be manufactured using high-melting-point metals such as tungsten. Therefore, this structure can be fabricated using methods such as spraying, vapor deposition, and 3D printing. The requirements for layer thickness precision are not high, nor are the requirements for the consistency of the material's optical properties; the structure is simple and inexpensive. To improve the laser energy reflectivity, several such structures can be used simultaneously in one direction to increase reflectivity.

[0057] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A laser pulse protective cladding based on nonlinear optical effects, characterized in that, The laser transmission direction includes, in sequence, a first uniform dielectric layer, a first nonlinear absorption dielectric layer, and a second uniform dielectric layer; wherein, the dielectric constant of the first nonlinear absorption dielectric layer is greater than that of the first uniform dielectric layer, and the dielectric constant of the first nonlinear absorption dielectric layer is greater than that of the second uniform dielectric layer; the nonlinear absorption or refractive index of the first nonlinear absorption dielectric layer increases with the increase of laser pulse power density, thereby increasing the reflectivity at the interface between the first nonlinear absorption dielectric layer and the uniform dielectric with the increase of laser pulse intensity.

2. The laser pulse protective cladding according to claim 1, characterized in that, The thickness of the first nonlinear absorption medium layer is determined according to the wavelength of the incident laser pulse.

3. The laser pulse protective cladding according to claim 1, characterized in that, The laser pulse protective cladding also includes a first metal layer, which is disposed between the first nonlinear absorption medium layer and the second uniform medium layer.

4. The laser pulse protective cladding according to claim 3, characterized in that, The thickness of the first metal layer is determined according to the wavelength of the incident laser pulse.

5. A laser pulse protective cladding based on nonlinear optical effects, characterized in that, The structure includes a third uniform dielectric layer and at least two reflective structural units along the laser transmission direction. Each reflective structural unit includes a uniform dielectric layer and a nonlinear absorption dielectric layer arranged sequentially along the laser transmission direction. The thickness, dielectric constant, and / or nonlinear response parameters of the nonlinear absorption dielectric layer in each reflective structural unit are different. Each reflective structural unit also includes a metal layer disposed after the nonlinear absorption dielectric layer along the laser transmission direction.

6. The laser pulse protective cladding according to claim 5, characterized in that, The thickness of the metal layer ranges from 0.1 to 0.2 micrometers.

7. The laser pulse protective cladding according to claim 5, characterized in that, The thickness of the reflective structural unit ranges from 0.2 to 1.5 micrometers.

8. The laser pulse protective cladding according to claim 5, characterized in that, The thickness and dielectric constant of the uniform dielectric layer in the reflective structural unit are determined based on the nonlinear absorption dielectric layer.

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