Fabrication method of fiber-type step-type laser flyer energy conversion element based on MEMS technology

Abstract

The present invention discloses a method for preparing a fiber-type step-type laser flyer energy converter based on MEMS technology, comprising the following steps: first, pre-treating the fiber end face, including polishing, cleaning, and drying; then, placing the fiber into a designed mold, sequentially subjecting the fiber end face to a single photolithography (coating, exposure, and development), magnetron sputtering, and degumming to prepare an ablation layer and a heat-insulating layer; then, sequentially subjecting the film obtained by the single photolithography to a secondary photolithography, magnetron sputtering, and degumming to prepare a flyer layer, thereby obtaining a fiber-type step-type laser flyer energy converter. The advantage of the step-type laser flyer energy converter prepared using MEMS technology is that the flyer film is directly plated on the fiber end face, resulting in good repeatability and low cost. In addition, by reducing the divergence of the laser at the output end of the fiber, the energy coupling efficiency of the energy converter at the end of the fiber is improved. Due to the step-type energy converter, the energy waste of the plasma caused by flyer shearing is effectively reduced, which is conducive to reducing the impact initiation threshold of the fiber-type laser flyer energy converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser explosive devices and relates to a method for preparing an optical fiber step-type laser flying plate energy conversion element based on a MEMS process. Background Art

[0002] Laser flyer impact initiation technology is an important initiation method for laser explosives. Its unique feature is that laser energy serves as the initial energy source, and high-speed flyer impacts trigger the detonation of an insensitive charge. This system offers advantages such as fully insensitive charges, high initiation precision, and high explosive power. This system utilizes optical fiber for energy transmission, isolating the energetic material from the electrical system. This system is insensitive to interference from static discharge and electromagnetic radiation, making it adaptable to complex electromagnetic environments and a key development direction for future safe initiation technology. Currently, domestic flyer transducers and optical fibers still utilize a separate design. However, this design leads to low energy coupling coefficients between the flyer transducer and the fiber end, slow flyer velocity, and poor reliability, significantly hindering efforts to improve flyer transduction efficiency and reduce the laser flyer initiation threshold. There have been reports of thin film deposition on optical fiber end faces, but these methods primarily rely on thin-film coating without steps. The energy waste caused by shearing the flyers also reduces transducer coupling efficiency. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and propose a method for preparing an optical fiber step-type laser flying plate energy conversion element based on MEMS technology.

[0004] The technical solutions of the present invention are as follows:

[0005] Step 1: Fiber cleaning: Use an ultrasonic instrument to clean the fiber end face with distilled water and organic solvent in sequence, and then dry it for later use.

[0006] Step 2: Place the optical fiber into the mold.

[0007] Step 3: Prepare the ablation layer and thermal insulation layer: photolithography pattern on the end face of the optical fiber, magnetron sputtering, and debonding.

[0008] Step 4: Prepare the flying sheet layer: second photolithography patterning, magnetron sputtering, and desmearing.

[0009] A short quartz optical fiber is selected as the coating substrate, and the structure adopts an ablation layer-thermal insulation layer-impact layer. The specific shape is a step type, in which the ablation layer is Al, the thermal insulation layer is Al2O3, and the flying sheet layer (impact layer) is Al.

[0010] By using the highly mature photolithography process and magnetron sputtering technology in MEMS technology, the stepped laser flying sheet film is directly plated on the end face of the optical fiber pigtail to form a flying sheet energy conversion element.

[0011] Using a short quartz fiber as the coating substrate effectively utilizes the energy transmitted by the fiber. Under the same conditions of injected laser energy, the laser energy attenuation caused by passing through other media is reduced. The laser light emitted from the fiber output end diverges, with the outer low-energy ring region exhibiting a diffuse pattern. The spot area 2 mm from the fiber output end is approximately 2.5 times larger than the spot area 0 mm from the fiber output end. The fiber-type laser flyer transducer effectively prevents laser divergence and energy density loss by directly coating the transducer at the fiber output end.

[0012] The laser flyer transducer is fabricated into a stepped shape to reduce energy loss caused by shearing of the flyer in the acceleration chamber. Traditional laser flyer transducers, whether single-layer or composite, are disc-shaped with a constant diameter. When the laser plasma drives the flyer, both the insulation layer and the impact layer cause a certain degree of energy loss during the shearing process in the acceleration chamber. Designing the flyer layer to be a circle smaller than the diameter of the acceleration chamber reduces the required shear film thickness, improves energy utilization efficiency, and increases the flyer speed.

[0013] The present invention has the significant advantages of:

[0014] 1. Utilizing the photolithography processing technology and magnetron sputtering process in MEMS technology, this method has good repeatability and low cost;

[0015] 2. The thickness of the metal film required to be sheared by the stepped laser flyer energy conversion element is relatively thin, which can reduce the energy loss caused by shearing the flyer when the plasma drives the flyer to a certain extent, and is conducive to lowering the impact initiation threshold of the fiber laser flyer;

[0016] 3. The laser is emitted from the output end of the optical fiber in a divergent shape, the spot area increases, and the laser energy density decreases. Plating the energy conversion element directly on the flyer can effectively reduce the divergence of the laser energy, maintain the high energy density of the laser, and increase the overall movement speed of the flyer;

[0017] 4. Directly using optical fiber as the substrate eliminates the interference and attenuation caused by the laser passing through other media, and increases the energy of the laser acting on the flyer transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart for preparing a stepped laser flying-plate energy conversion element.

[0019] Figure 2 Schematic diagram of the stepped laser flying plate energy conversion element.

[0020] Figure 3 These are the flying piece test results of 0.8mm core diameter optical fiber, 65mJ laser energy fiber-type laser flying piece transducer and separate laser flying piece transducer.

[0021] Figure 4These are the flying piece test results of 1.0mm core diameter optical fiber, 65mJ laser energy fiber-type laser flying piece transducer and separate laser flying piece transducer.

[0022] Figure 5 The figure shows the energy loss test results of laser passing through K9 glass under different injection laser energy conditions. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

[0024] A method for preparing a fiber-type step-type laser flyer energy conversion element based on MEMS technology includes the following specific steps:

[0025] 1) Fiber cleaning: Use an ultrasonic instrument to clean the fiber end face with distilled water and then an organic solvent. After cleaning, remove the substrate with tweezers and dry it for later use.

[0026] 2) Place the optical fiber into the designed mold.

[0027] 3) Apply glue evenly on the end face of the optical fiber. After applying glue, place the optical fiber in an oven for drying. Use a mask larger than the diameter of the optical fiber core as the plate-making pattern and expose the optical fiber end face coated with photoresist for 15-30 seconds.

[0028] 4) The exposed optical fiber end face obtained in 3) is placed in a positive photoresist developer for development until the photoresist in the exposed area is dissolved to form a clear photoresist pattern, and the developed optical fiber is dried.

[0029] 5) The developed optical fiber is subjected to magnetron sputtering coating to prepare an ablation layer (Al) and a thermal insulation layer (Al2O3).

[0030] 6) Develop the photoresist and use an organic solvent to remove the photoresist and excess film on the surface to form a thin film pattern.

[0031] 7) Apply glue evenly on the second film (insulation layer). After applying glue, place the optical fiber in an oven for drying. Use a mask that is smaller than the diameter of the accelerating chamber that matches it as the plate-making pattern, and expose the optical fiber end face coated with photoresist for 15-30 seconds.

[0032] 8) The exposed optical fiber obtained in 7) is placed in a positive photoresist developer for development until the photoresist in the exposed area is dissolved to form a clear photoresist pattern, and the developed optical fiber is dried.

[0033] 9) The developed optical fiber is subjected to magnetron sputtering to prepare a flyer layer (Al).

[0034] 10) Develop the photoresist and remove the photoresist and excess film on the surface with an organic solvent to obtain the final product.

[0035] Traditional split-type laser flyer transducers use a K9 glass substrate as the coating substrate, with the laser flyer transducer plated on the substrate surface. Laser energy is transmitted through the optical fiber and then acts on the transducer through the K9 glass substrate.

[0036] Figure 5 This test measures the energy loss rate of laser light passing through K9 glass under varying laser energy conditions. Since the split laser flyer transducer uses a K9 glass substrate, the laser energy attenuates by approximately 11.9% to 21.8% as it passes through the glass substrate. However, since the fiber-type laser flyer transducer does not pass through the K9 glass substrate, the energy at the fiber output is the energy coupled into the transducer, effectively reducing laser energy attenuation during transmission.

[0037] Figure 3-4 The flying sheet velocities of the fiber-type laser flying sheet energy converter and the split-type laser flying sheet energy converter at a laser energy of 65mJ were compared under the transmission conditions of 0.8mm and 1.0mm core diameter optical fibers, respectively.

[0038] The average speed of the fiber-type laser flyer transducer with a 0.8mm core diameter fiber was 1648m / s, while the average speed of the split laser flyer transducer was 1474m / s. The average speed of the fiber-type laser flyer transducer with a 1.0mm core diameter fiber was 1735m / s, while the average speed of the split laser flyer transducer was 872m / s. Comparison revealed that the flyer speed of the fiber-type laser flyer transducer was higher than that of the split laser flyer transducer, regardless of whether the 1.0mm or 0.8mm core diameter fiber was used for energy transmission, reaching a maximum speed of 2485m / s.

Claims

1. A method for preparing a fiber-type step-type laser flyer energy conversion element based on MEMS technology, characterized in that: The method comprises the following steps: First, pre-process the optical fiber end face: polish, clean, and dry; Then put the optical fiber into the mold and perform photolithography on the end face of the optical fiber in sequence: coating, exposure, and development. Perform magnetron sputtering and debonding to prepare ablation layer and thermal insulation layer; The film produced by the primary photolithography is subjected to secondary photolithography, magnetron sputtering and desmearing in sequence to prepare a flying sheet layer, thereby obtaining a fiber-type step-type laser flying sheet transducer. A short quartz optical fiber is used as the coating substrate; the structure is an ablation layer-insulation layer-impact layer, where the ablation layer is Al, the insulation layer is Al2O3, and the flyer layer is Al; the shape is a step-type, where the flyer layer diameter is smaller than the ablation layer and the insulation layer diameter and matches the acceleration chamber diameter; the core diameter of the optical fiber is 0.8mm and 1.0mm.

2. The method for preparing a fiber-type step-type laser flyer energy conversion element based on MEMS technology according to claim 1, characterized in that: The specific steps of pre-treatment of the optical fiber end face are: using an ultrasonic instrument to ultrasonically clean the optical fiber end face with distilled water and organic solvent in sequence, and after cleaning, use tweezers to remove the substrate and dry it for later use.

3. The method for preparing a fiber-type step-type laser flyer energy conversion element based on MEMS technology according to claim 1, characterized in that: The specific steps of a single photolithography are: evenly apply glue on the end face of the optical fiber, put the optical fiber into an oven for drying after applying glue, use a mask with a circle larger than the diameter of the optical fiber core as the plate pattern, and expose the optical fiber end face coated with photoresist for 15-30 seconds; The exposed optical fiber end face is placed in a positive photoresist developer for development until the photoresist in the exposed area is dissolved to form a clear photoresist pattern, and the developed optical fiber is dried.

4. The method for preparing a fiber-type step-type laser flyer energy conversion element based on MEMS technology according to claim 1, characterized in that: The specific steps of preparing the ablation layer and the thermal insulation layer are as follows: performing magnetron sputtering coating on the developed optical fiber to prepare the ablation layer and the thermal insulation layer, developing the photoresist, and using an organic solvent to remove the photoresist and the excess film on the surface to form a thin film. Graphics.

5. The method for preparing a fiber-type step-type laser flyer energy conversion element based on MEMS technology according to claim 1, characterized in that: The specific steps of preparing the flyer layer are as follows: put the exposed optical fiber into the positive photoresist developer Developing is performed until the photoresist in the exposed area is dissolved to form a clear photoresist pattern, and the developed optical fiber is dried; The developed optical fiber is subjected to magnetron sputtering to prepare a flyer layer.

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