An angle-insensitive laser power sensor based on porous columnar structure absorption layer and preparation method thereof

Abstract

The present invention relates to an angle-insensitive laser power probe based on a porous columnar structure absorption layer and a preparation method thereof. The laser power probe comprises a porous absorption layer, an aluminum substrate, an organic insulating layer, a thermocouple layer, a protective layer, and a lead. The porous absorption layer is located at the top, the aluminum substrate is located below the porous absorption layer, the organic insulating layer is located on the back of the aluminum substrate, the thermocouple layer is a planar circularly symmetrical structure deposited on the organic insulating layer, and the head and tail ends of the thermocouple layer are connected by the lead. The absorption layer of the laser probe adopted by the present invention adopts a porous columnar anti-reflection design, which reduces the reflection of the absorption layer to the laser, more effectively absorbs the laser energy, and enhances the signal-to-noise ratio. By optimizing the parameters of the porous columnar structure, the reflectivity is made insensitive to the incident angle. During detection, it is not necessary to always ensure that the laser is incident on the product, which will effectively improve the working efficiency of laser detection.

Description

Technical Field

[0001] The present invention relates to the technical field of high-power laser detection equipment, in particular to an angle-insensitive laser power probe based on a porous columnar structure absorption layer and a preparation method thereof. Background Art

[0002] High-power lasers have broad application prospects in laser pump sources, laser processing, and laser weapons, and have become crucial for national economic and national defense development. For example, they are widely used in laser cutting, laser cleaning, laser cladding, and laser welding, owing to their advantages of high heat output, minimal thermal deformation, small spot diameter, precise positioning, ease of operation, and pollution-free operation. In medical aesthetics, they can be used for laser surgery, laser dynamics therapy, and laser hair removal. In the military, they can be used in laser radar, laser guidance, and laser fuses. Stable laser power is fundamental to the application of high-power lasers in these areas, particularly in the medical and military fields. However, over extended processing times, laser power attenuation can lead to defective products or accidents. Therefore, ensuring that laser power meets requirements and maintains its stability becomes crucial, leading to the need for high-power laser monitoring and detection technologies.

[0003] The power sensor is the core of a laser power detector. The absorption layer of a power sensor is typically made of bulk semiconductor material, typically silicon or silicon carbide. When laser light strikes the interface, it reflects off the air-material interface, as semiconductor materials generally have high refractive indices (e.g., 3.42 for Si and 2.7 for SiC). The Fresnel equation shows that when infrared light is incident directly on the surface, the reflectivity of Si is 22%, while that of SiC is 29%. This means that nearly half of the energy of high-power laser light is reflected, significantly reducing the accuracy and signal-to-noise ratio of laser power detection. Furthermore, high-power laser emission can damage surrounding objects and even human vision. Therefore, it is crucial to prepare a laser absorption layer with low reflectivity.

[0004] Furthermore, currently commonly used high-power laser probes have a drawback: during testing, the laser beam must enter the probe as perpendicularly as possible to ensure repeatable and accurate calibration or measurement. The probe's absorption of the laser beam by the absorption layer is affected by the varying reflectivity of the laser beam incident at different angles. This is partly because the absorption layer is too flat, causing the reflectivity to vary with the angle of incidence. Furthermore, excessively high reflectivity exacerbates this effect, limiting the application scenarios of these high-power probes.

[0005] In view of the above technical problems, improvements need to be made. Summary of the Invention

[0006] In response to the defects and shortcomings of the above-mentioned existing systems, this paper proposes an angle-insensitive laser power sensor based on a porous columnar structure absorption layer and a preparation method thereof.

[0007] In order to achieve the above objectives, the technical solution adopted by the present invention is: an angle-insensitive laser power probe based on a porous columnar structure absorption layer, the laser power probe including a porous absorption layer, an aluminum substrate, an organic insulating layer, a thermocouple layer, a protective layer and a lead; the porous absorption layer is located at the top, the aluminum substrate is located below the porous absorption layer, the organic insulating layer is located on the back of the aluminum substrate, the thermocouple layer is a planar circularly symmetrical structure, deposited on the organic insulating layer, and the head and tail ends of the thermocouple layer are connected by the lead.

[0008] As a preferred solution of the present invention, the porous absorption layer is composed of high-temperature resistant, high thermal conductivity, and high absorption materials such as Si or SiC; the surface of the porous absorption layer is a porous columnar structure.

[0009] As a preferred solution of the present invention, the organic insulating layer is a polyimide layer with a thickness of 0.02-0.1 mm, high temperature resistance of 300° C., and a thermal expansion coefficient close to that of metal.

[0010] As a preferred solution of the present invention, the thermocouple layer is a thin film thermocouple with NiCr-NiSi or NiCr-NiCu as electrode material connected in a zigzag shape to form a flat circular shape.

[0011] A method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer comprises the following steps:

[0012] Step 1: Obtain the reflectivity of the Si and SiC porous columnar structure absorption layer through optical simulation, adjust the height, width, and porosity of the porous columnar structure, and optimize the structural parameters with the lowest reflectivity;

[0013] Step 2: Use silicon powder with a particle size of 10μm to 45μm, control the spraying time, and prepare a silicon coating with a desired thickness range on the aluminum substrate by plasma spraying.

[0014] Step 3: Based on the porous columnar structure obtained by simulation optimization, a porous columnar structure is prepared on the surface of the absorption layer using a chemical etching method.

[0015] Step 4: Prepare a polyimide organic insulating layer on the back of the aluminum substrate using a photosensitive polyimide coating adhesive.

[0016] Step 5: Using magnetron sputtering on the polyimide insulating coating, a NiCr-NiSi or NiCr-NiCu thin film thermopile is prepared with the help of a circular mask formed by a Z-shaped period.

[0017] Step 6: Use soldering to lead out electrical signal wires from the positive and negative terminals of the thermopile.

[0018] As a preferred embodiment of the present invention, in step 1, the structural model parameters are designed using CST software to simulate the reflectivity of the porous columnar structure absorption layer in the 300-1100 nm band; based on the dielectric constants of Si, SiC, and air, combined with parameters such as the shape, height, width, and spacing of the columns, the reflectivity at different angles is simulated. After optimization, the height of the columns is 0.6-10 μm, the width of the columns is 0.2-2 μm, and the spacing between the columns is 0.1-1 μm; the structural parameters are simulated and optimized using CST software to achieve optimal values.

[0019] As a preferred solution of the present invention, the preparation process of the Si and SiC absorption layers in step 2 is: sandblasting the front surface of the aluminum substrate, and using a plasma spraying method to prepare an absorption layer with a thickness of 80 μm to 200 μm.

[0020] As a preferred embodiment of the present invention, the surface preparation process of the porous columnar absorption layer in step 3 is as follows: the prepared coating substrate is ultrasonically cleaned with alcohol, dried with nitrogen, activated with ultraviolet light, and etched using ion-assisted etching according to the geometric parameters of the porous columnar absorption layer obtained by simulation, with the solution concentration controlled, the temperature at 40-80°C, and the time for 10-40 minutes to etch a porous columnar surface with a thickness of 0.6-10 μm.

[0021] As a preferred embodiment of the present invention, the polyimide organic insulating layer is prepared using a photosensitive polyimide coating glue in step 4. The preparation method is: clean the back of the aluminum substrate, take 50-250 μL of room temperature coating glue and drop it on the back of the aluminum substrate, spin coat it for 100-200 seconds by a low-speed and high-speed combination method, and then slowly bake it by a low-temperature and high-temperature combination method to obtain a flat polyimide insulating layer.

[0022] As a preferred embodiment of the present invention, in step 5, the method for preparing the thin film thermopile is: using DC sputtering or AC sputtering of a magnetron sputtering method on a circular polyimide film, using a Z-shaped mask to prepare a NiCr-NiSi or NiCr-NiCu thin film thermopile, with the high temperature end at the center of the circle and the low temperature end at the edge of the circle.

[0023] As a preferred solution of the present invention, in step 6, soldering is used to lead out the positive and negative electrodes of the thermopile with wires to avoid high resistance after connection.

[0024] The beneficial effects of the present invention are:

[0025] 1. The laser probe's absorption layer utilizes a porous columnar anti-reflection design, which reduces laser reflection, effectively absorbing laser energy and enhancing the signal-to-noise ratio. By optimizing the parameters of the porous columnar structure, the reflectivity is made insensitive to the angle of incidence. This eliminates the need to ensure that the laser is always incident on the product during detection, significantly improving laser detection efficiency.

[0026] 2. This invention uses an organic insulating film as the insulating layer, replacing the anodic aluminum oxide layer on the aluminum substrate. Compared to the anodic oxidation process, the organic spin coating process is simpler and uses less energy. Furthermore, the thermal expansion coefficient of the organic insulating film is closer to that of thermopile alloys NiCr, NiSi, and NiCu than that of aluminum oxide, effectively reducing stress during probe use and extending probe life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic structural diagram of the laser probe of the present invention;

[0028] Figure 2 Schematic diagram of an absorption layer having a porous columnar surface according to the present invention;

[0029] Figure 3 This is a scanning electron microscope image of the absorption layer having a porous columnar surface according to the present invention;

[0030] Figure 4 This is a reflectivity test chart of the laser probe of the present invention at different light incident angles;

[0031] Figure 5 This is a thermoelectric signal diagram of the laser probe of the present invention under different light incident angles of 10W laser.

[0032] Reference numerals in the figure: 1. porous absorption layer, 2. aluminum substrate, 3. organic insulation layer, 4. thermocouple layer, 5. protective layer. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0035] Example:

[0036] A method based on Figure 1 The angle-insensitive laser power sensor with a porous columnar structure absorption layer shown in the figure includes a porous absorption layer 1, an aluminum substrate 2, an organic insulating layer 3, a thermocouple layer 4, a protective layer 5 and a lead; the porous absorption layer 1 is located at the top, the aluminum substrate 2 is located below the porous absorption layer 1, the organic insulating layer 3 is located on the back of the aluminum substrate 2, the thermocouple layer 4 is a planar circularly symmetrical structure, deposited on the organic insulating layer 3, and the head and tail ends of the thermocouple layer 4 are connected by the lead.

[0037] A method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer comprises the following steps:

[0038] Step 1: Select Si as the absorption layer; simulate the reflectivity of the porous columnar structure absorption layer and adjust the structural parameters to reduce the reflectivity;

[0039] In step 1, in the CST software, as Figure 2 As shown, a frustum is selected as the columnar structure, and the reflectivity of the porous columnar structure absorption layer in the 300-1100nm band is simulated; according to the dielectric constants of Si and air, the height of the frustum column optimized for reflectivity is 10μm, the bottom diameter is 2μm, the top diameter is 1.4μm, the column spacing is 1μm, and an ideal absorption substrate is used.

[0040] Continue to optimize the simulation based on the structural parameters with lower reflectivity to obtain structural parameters with lower reflectivity and insensitive to the incident angle;

[0041] In step 2, the simulation continued using the resulting low-reflectivity structural parameters. After optimizing for angle-insensitivity, the frustum pillars had an 8μm height, a 2μm base diameter, a 1.8μm top diameter, and a 1.6μm pillar spacing. This was done using an ideal absorbing substrate. With these parameters, the absorber layer's reflectivity was insensitive to angle and relatively low.

[0042] Step 3: A Si heat-absorbing layer is prepared on an aluminum substrate by plasma spraying. Then, a porous columnar surface is prepared on the Si coating by ion-assisted etching based on the porous columnar structure parameters obtained by simulation optimization.

[0043] The treatment process in step 3 is: sandblasting is performed on the surface of the base aluminum plate, and then silicon powder with a particle size of 45μm is used to prepare a light-absorbing and heat-conducting silicon layer by plasma spraying. The working gas is Ar and H2, the power is 39.2KW, the spraying distance is 100mm, the powder feeding rate is 10g / min, and the spraying time is controlled to prepare a 140μm thick Si heat-absorbing layer.

[0044] In step 3, the prepared coating substrate is ultrasonically cleaned with alcohol, dried with nitrogen, and activated with ultraviolet light. The various parameters of the porous columnar surface obtained by simulating step 2) are used, and the porous columnar surface is etched on the Si absorption layer using the Cu ion-assisted etching method. The etching solution consists of 6 mol / L hydrofluoric acid; 2 mol / L hydrogen peroxide; 0.08 mol / L copper nitrate and deionized water; the reaction temperature is 60°C, the time is 20 minutes, and a porous columnar surface with a thickness of nearly 10 μm is etched. The copper ions are washed with deionized water to form a porous columnar surface. Figure 3 The absorbent layer surface is shown.

[0045] In step 4, a polyimide organic insulating layer is then prepared on the back of the aluminum substrate using a photosensitive polyimide coating adhesive.

[0046] In step 4, the polyimide organic insulating layer is prepared using a photosensitive polyimide coating adhesive. The preparation method is as follows: Remove the refrigerated photosensitive polyimide coating adhesive and allow it to stand at room temperature for 2 hours until it reaches room temperature. Ultrasonic clean the back of the aluminum substrate with acetone and ethanol for 5 minutes, then bake it on an 85°C hotplate for 30 minutes. Apply 100 μL of the coating adhesive to the aluminum substrate and spin it at a low speed of 600 rpm for 9 seconds, then at a high speed of 1200 rpm for 30 seconds to complete the spin coating. Place the spin-coated aluminum substrate on a hotplate and bake it at 80°C for 10 minutes, then at 120°C for 10 minutes, and then cool it to room temperature. Cut the insulating layer into a circle with a radius of 40 mm.

[0047] Step 5: Using a stainless steel mask, a thin film thermopile is prepared on the polyimide organic insulating layer by magnetron sputtering.

[0048] The process of step 5 is to prepare thin film thermocouples NiCr and NiCu by magnetron sputtering. Sputtering parameters: background vacuum degree 5×10 -4 Pa, Ar gas flow rate 100 sccm, working gas pressure 1 Pa, using a 70 W DC power supply to sputter NiCr and NiSi for 20 minutes each.

[0049] Step 6: Use soldering to connect the head and tail ends of the thin film thermocouple and lead out the electric heating signal line.

[0050] In this example, the porous columnar absorption layer made of Si material makes the optical properties insensitive to the incident angle. Figure 4 As shown in the figure, the reflectivity curves at different incident angles are measured in a spectrometer. It can be seen that in the range of 300-900nm, the reflectivity curves at different angles basically overlap. Because light absorption and heat transfer are not sensitive to the laser incident angle. Figure 5 As shown in the figure, at two wavelengths of 532 and 1064 nm and different laser incident angles, the measured thermoelectric signals do not change much within a range of 50°.

[0051] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is to be embodied in the widest possible manner consistent with the principles and novel features disclosed herein.

[0052] Although this document frequently uses the following terms: 1. porous absorbing layer, 2. aluminum substrate, 3. organic insulating layer, 4. thermocouple layer, 5. protective layer, etc., the use of other terms is not excluded. These terms are used solely to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations would be contrary to the spirit of the present invention.

Claims

1. An angle-insensitive laser power sensor based on a porous columnar structure absorption layer, characterized by: The laser power probe comprises a porous absorption layer (1), an aluminum substrate (2), an organic insulating layer (3), a thermocouple layer (4), a protective layer (5) and a lead; the porous absorption layer (1) is located on the top, the aluminum substrate (2) is located below the porous absorption layer (1), the organic insulating layer (3) is located on the back of the aluminum substrate (2), the thermocouple layer (4) is a planar circularly symmetrical structure, and is deposited on the organic insulating layer (3); the head and tail ends of the thermocouple layer (4) are connected by the lead; The surface of the porous absorption layer (1) is a porous columnar structure.

2. The angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 1, characterized in that: The porous absorption layer (1) is Si or SiC.

3. The angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 1, characterized in that: The organic insulating layer (3) is a polyimide layer with a thickness of 0.02-0.1 mm.

4. The angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 1, characterized in that: The thermocouple layer (4) is a thin film thermocouple with NiCr-NiSi or NiCr-NiCu as electrode material connected in a zigzag shape to form a flat circular shape.

5. A method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Obtain the reflectivity of the Si and SiC porous columnar structure absorption layer through optical simulation, adjust the height, width, and porosity of the porous columnar structure, and optimize the structural parameters with the lowest reflectivity; Step 2: using silicon powder with a particle size of 10 μm to 45 μm, controlling the spraying time, and preparing a silicon coating of the desired thickness range on the aluminum substrate (2) by plasma spraying; Step 3: Based on the porous columnar structure obtained by simulation optimization, a porous columnar structure is prepared on the surface of the absorption layer using a chemical etching method; Step 4: Prepare a polyimide organic insulating layer (3) on the back of the aluminum substrate using a photosensitive polyimide coating adhesive; Step 5: Using magnetron sputtering on the polyimide insulating coating, a NiCr-NiSi or NiCr-NiCu thin film thermopile is prepared using a circular mask surrounded by a zigzag period; Step 6: Use soldering to lead out electrical signal wires from the positive and negative terminals of the thermopile.

6. The method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 5, characterized in that: In step 1, the structural model parameters are designed using CST software to simulate the reflectivity of the porous columnar structure absorption layer in the 300-1100 nm band; based on the dielectric constants of Si, SiC, and air, combined with parameters such as the shape, height, width, and spacing of the columns, the reflectivity at different angles is simulated. After optimization, the height of the columns is 0.6-10 μm, the width of the columns is 0.2-2 μm, and the spacing between the columns is 0.1-1 μm; the structural parameters are simulated and optimized using CST software to achieve optimal values.

7. The method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 5, characterized in that: The preparation process of the Si and SiC absorption layers in step 2 is as follows: sandblasting the front surface of the aluminum substrate and using a plasma spraying method to prepare an absorption layer with a thickness of 80 μm to 200 μm.

8. The method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 5, characterized in that: The surface preparation process of the porous columnar absorption layer in step 3 is as follows: the prepared coating substrate is ultrasonically cleaned with alcohol, dried with nitrogen, activated with ultraviolet light, and etched using ion-assisted etching according to the geometric parameters of the porous columnar absorption layer obtained by simulation, with the solution concentration controlled, the temperature at 40-80°C, and the time for 10-40 minutes to etch a porous columnar surface with a thickness of 0.6-10 μm.

9. The method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 5, characterized in that: In step 4, the polyimide organic insulating layer is prepared using a photosensitive polyimide coating glue. The preparation method is as follows: clean the back of the aluminum substrate, take 50-250 μL of room temperature coating glue and drop it on the back of the aluminum substrate, spin coat it for 100-200 seconds by a low-speed and high-speed combination method, and then slowly bake it by a low-temperature and high-temperature combination method to obtain a flat polyimide insulating layer.

10. The method for preparing an angle-insensitive laser power sensor based on a porous columnar structure absorption layer according to claim 5, characterized in that: In step 5, the method for preparing the thin film thermopile is: using a magnetron sputtering method of DC sputtering or AC sputtering on a circular polyimide film, using a Z-shaped mask to prepare a NiCr-NiSi or NiCr-NiCu thin film thermopile, with the high temperature end at the center of the circle and the low temperature end at the edge of the circle.

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