Method for preparing dielectric crystal surface periodic structure at room temperature by combining femtosecond laser with ion implantation

Abstract

The invention discloses a method for preparing a dielectric crystal surface periodic structure at room temperature by combining femtosecond laser with ion implantation, and belongs to the technical field of integrated optics. The method comprises the following steps: bombarding the surface of a dielectric crystal by using metal ions to form an injection layer; and focusing femtosecond laser on the surface of the injection layer of the dielectric crystal, lowering the position of the dielectric crystal, and scribing on the surface of the injection layer by moving the position of the dielectric crystal to obtain a surface periodic structure. According to the method, the periodic structure on the surface of the dielectric crystal material is prepared at the room temperature, meanwhile, the method is easy to operate, and large-scale preparation, popularization and application of the periodic structure on the surface can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated optics, and in particular relates to a method for preparing a periodic structure on the surface of a dielectric crystal at room temperature by combining femtosecond laser with ion implantation. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] With the development of laser micro-nano processing technology, the size of optical devices is also constantly decreasing. Among them, the surface periodic structure prepared by femtosecond laser is a typical nanoscale optical structure. It serves as a springboard for the field of femtosecond laser subtractive manufacturing to move towards nanometer and even sub-nanometer level fine structures, and has derived a series of groundbreaking scientific research results, such as: optical FIB effect, laser permanent optical storage, etc. Generally, laser-induced periodic structures are commonly found on the surfaces of metals and semiconductor materials, but for dielectric crystal materials, due to their stable chemical and physical properties, it is relatively difficult to process the materials through a single "pure physical" method. For example, in lithium niobate crystals, the effect of regular periodic nanostructures can only be achieved when the external temperature reaches about 1000°C.

[0004] Therefore, there is an urgent need to propose a method for preparing periodic structures on the surface of dielectric crystal materials with simple operation and mild conditions. Summary of the invention

[0005] In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a periodic structure on the surface of a dielectric crystal at room temperature by combining femtosecond laser with ion implantation. The present invention provides a method for preparing a periodic nanostructure on the surface of a dielectric crystal at room temperature by combining ion implantation with femtosecond laser direct writing processing. The method can be applied to common ferroelectric crystal surfaces, is easy to process, has a simple process, a short time and a low cost, provides a new method for new micro-nano processing with femtosecond laser, and expands the scope of application of laser-induced periodic structures.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] The first aspect of the present invention provides a method for preparing a periodic structure on the surface of a dielectric crystal at room temperature by combining femtosecond laser with ion implantation, comprising:

[0008] The surface of the dielectric crystal is bombarded with metal ions to form an implantation layer;

[0009] The femtosecond laser is focused on the surface of the injection layer of the dielectric crystal, the position of the dielectric crystal is lowered, and lines are engraved on the surface of the injection layer by moving the position of the dielectric crystal to obtain a surface periodic structure.

[0010] Ion implantation has been widely recognized as an outstanding surface material modification method, which is applicable to more than 100 optical materials. The present invention uses ion implantation combined with femtosecond laser direct writing to prepare periodic structures on the surface of dielectric crystals at room temperature. During the ion implantation process, the charged metal ions entering the dielectric crystal gradually lose energy when interacting with the nuclei and electrons of the dielectric crystal material, and finally stop in the near-surface region to form an implantation layer. Therefore, the desired specific material property changes can be achieved in the ion irradiation area, such as the change of refractive index in waveguide manufacturing. The present invention can synthesize embedded metal nanoparticles in the near-surface region of the dielectric by carefully selecting the ion species and implantation parameters. These metal nanoparticles exhibit local surface plasmon resonance effects, which greatly improve the enhancement, modification and regulation of the inherent optical properties of the dielectric. Ion implantation simultaneously realizes the material integration of metal nanoparticles and dielectric crystals, and realizes the functional fusion of plasmon resonance effects and multiple optoelectronic properties in the near-surface volume, thereby forming a "metal nanoparticle + crystal" composite surface layer, which is expected to achieve multifunctional integrated applications. Obviously, compared with chemically synthesized metal nanoparticles, metal nanoparticles synthesized by ion implantation have significant environmental stability because they are wrapped by the dielectric matrix. The present invention adopts a method of combining ion implantation with femtosecond laser direct writing processing. Under the induction of femtosecond laser, the metal nanoparticles in the implantation layer are aggregated, and the free metal elements are aggregated into nanoparticles or aggregated into larger nanoparticles. By adjusting the energy of the laser, the preparation of a large-area laser-induced surface periodic structure can be achieved. At the same time, by adjusting the polarization direction of the laser, the direction of the periodic structure can be regulated, which provides a feasible solution for the preparation of large-scale surface periodic structures based on the surface of ferroelectric crystals, and has broad application prospects in the field of femtosecond laser subtractive micro-nano manufacturing.

[0011] In some embodiments of the present invention, the method further comprises the step of pre-treating the dielectric crystal, and after the pre-treatment, bombarding the surface of the dielectric crystal with metal ions;

[0012] Wherein, the pretreatment includes: cutting, polishing and cleaning the dielectric crystal.

[0013] In some embodiments of the present invention, the cutting is to cut the dielectric crystal into 1×1×0.2 cm 3 of crystal blocks.

[0014] In some embodiments of the present invention, the polishing is to polish two opposite side surfaces and one large surface of the cut dielectric crystal.

[0015] It should be noted that the term "large face" refers to the face with a larger area in a dielectric crystal, and the term "side face" refers to the face with a smaller area in a dielectric crystal. For example, a dielectric crystal is cut into 1×1×0.2cm 3 Square crystal blocks, 1×1cm 2 The large surface is 1×0.2cm 2 The side is the side.

[0016] It should be noted that the polishing can be performed using conventional polishing techniques.

[0017] In some embodiments of the present invention, the cleaning is to ultrasonically clean the polished dielectric crystal using acetone, alcohol and deionized water respectively.

[0018] In some embodiments of the present invention, the dielectric crystal is a lithium tantalate (LiTaO 3 ) crystal or a lithium niobate (LiNbO 3 ) crystal.

[0019] In some embodiments of the present invention, the metal ions are gold particles or silver ions.

[0020] In some embodiments of the present invention, the bombardment, the energy of the metal ions is 70-400 keV, the dose is 5×10 16 ions / cm 2 .

[0021] It should be noted that the present invention adopts the method of metal ion implantation to form a nanometer-scale implantation layer with metal elements or metal nanoparticles under the surface of the ferroelectric crystal. The metal elements are free in the implantation layer or small-sized metal nanoparticles are formed, which can effectively introduce the metal elements into the dielectric environment. The state of the metal elements in the implantation layer can be changed by adjusting the energy of the metal ions. The inventors have found that as the energy of the metal ions increases, the metal in the implantation layer gradually changes from free metal elements to metal nanoparticles. When the energy of the metal ions is ≥160keV, the metal in the implantation layer is a metal nanoparticle.

[0022] In some embodiments of the present invention, the injection layer is located below the surface of the bombarded dielectric crystal, and the thickness of the injection layer is 60-100 nm.

[0023] In some embodiments of the present invention, the pulse width of the femtosecond laser used for processing is 110 fs, the repetition frequency is 1 kHz, the central wavelength is 800 nm, and the scanning speed is 0.01-1 mm / s.

[0024] In some embodiments of the present invention, after the position of the dielectric crystal is lowered, the distance between the dielectric crystal and the focus of the femtosecond laser is 5-20 μm.

[0025] It should be noted that the femtosecond laser is focused on the surface of the injection layer of the dielectric crystal, and then the sample is lowered and defocused to obtain a larger surface periodic structure and a wider energy adjustment range. The energy is adjusted so that the area irradiated by the femtosecond laser appears as a white area and a gray area under the microscope, where the white area is mainly the metal element aggregation stage, and the gray area is the main stage of the surface periodic structure formation.

[0026] In some embodiments of the present invention, the optical microscope used to characterize the morphology of the processed area is a Zeiss optical microscope.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides a method for preparing a periodic structure on the surface of a dielectric crystal at room temperature by combining femtosecond laser with ion implantation. The present invention adopts the method of metal ion implantation to form a nanometer-scale implantation layer with metal elements or metal nanoparticles under the surface of a ferroelectric crystal. The metal elements are free in the implantation layer or small-sized metal nanoparticles are formed, which can effectively introduce the metal elements into a dielectric environment. Combined with femtosecond laser direct writing processing, under the induction of the femtosecond laser, the metal nanoparticles in the implantation layer are aggregated, and the free metal elements are aggregated into nanoparticles or aggregated into larger nanoparticles. When the femtosecond laser is irradiated on the nanoparticles, the laser will have a strong ionization effect on the particles, so that localized surface plasmon resonance is generated around the nanoparticles, and a huge internal electric field is generated around the nanoparticles. At the same time, free electrons are ionized to generate transmission-type surface plasmons, forming a surface periodic structure. By adjusting the energy of the laser, large-area (1×1cm 2 ) Preparation of laser-induced surface periodic structures. At the same time, adjusting the polarization direction of the laser can achieve the regulation of the direction of the periodic structure. The direction of the periodic structure is always perpendicular to the polarization direction of the laser, which provides a feasible solution for the preparation of large-scale surface periodic structures based on ferroelectric crystal surfaces and has broad application prospects in the field of femtosecond laser subtractive micro-nano manufacturing. This method realizes the preparation of periodic structures on the surface of dielectric crystal materials at room temperature. At the same time, this method is simple to operate and can achieve the preparation and promotion of large-scale surface periodic structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 This is a schematic diagram of metal ion implantation into a dielectric crystal to form an implantation layer and combining femtosecond laser to prepare a surface periodic structure in an embodiment of the present invention;

[0031] Figure 2This is a topography of the injection layer in Example 1 of the present invention;

[0032] Figure 3 This is a morphology image of nanoparticles in the surface periodic structure obtained in Example 1 of the present invention;

[0033] Figure 4 This is a morphology diagram of the surface periodic structure obtained in Example 1 of the present invention.

[0034] Among them, 1. metal ion beam, 2. metal element distribution or metal nanoparticles, 3. injection layer, 4. dielectric crystal, 5. femtosecond laser beam, 6. focusing objective lens, 7. dielectric crystal injected with metal elements, 8. stage, 9. six-axis translation stage. DETAILED DESCRIPTION

[0035] In view of the difficulty in preparing periodic structures on the surface of dielectric crystals, the present invention provides a method for preparing periodic structures on the surface of dielectric crystals at room temperature by combining femtosecond laser with ion implantation. Figure 1 As shown, the specific steps include:

[0036] (1) Cut the volume into 1×1×0.2cm 3 The dielectric crystal 4 is polished and cleaned;

[0037] (2) Using an ion accelerator to emit energy of 70-400 keV and a dose of 5×10 16 ions / cm 2 A gold or silver ion beam 1 bombards the polished surface of a dielectric crystal 4, forming an implantation layer 3 with a thickness of 60-100 nm below the directly bombarded polished surface, and forming a free metal element distribution or metal nanoparticles 2 in the implantation layer 3;

[0038] (3) placing a dielectric crystal 7 injected with metal elements to form the injection layer 2 on a stage 8, adjusting the dielectric crystal 7 injected with metal elements to a horizontal position by a six-axis translation stage 9, and then focusing a femtosecond laser beam 5 on the surface of the injection layer 3 through a focusing lens 6;

[0039] The femtosecond laser used for processing has a pulse width of 110fs, a repetition rate of 1kHz, a central wavelength of 800nm, and a scanning speed of 0.01-1mm / s;

[0040] (4) The six-axis translation stage 9 is adjusted so that the surface of the injection layer 3 is lowered to a distance of 5-20 μm from the focus of the femtosecond laser. Lines are engraved on the surface of the injection layer 3 by moving the six-axis translation stage, and a laser-induced surface periodic structure can be obtained inside the engraved lines.

[0041] The present invention provides a method for preparing a periodic structure on the surface of a dielectric crystal at room temperature by combining femtosecond laser with ion implantation. The present invention adopts the method of metal ion implantation to form a nanometer-scale implantation layer with metal elements or metal nanoparticles under the surface of a ferroelectric crystal. The metal elements are free in the implantation layer or metal nanoparticles with smaller sizes are formed, which can effectively introduce the metal elements into a dielectric environment. Combined with femtosecond laser direct writing processing, under the induction of femtosecond laser, the metal nanoparticles in the implantation layer are aggregated, and the free metal elements are aggregated into nanoparticles or aggregated into larger nanoparticles. By adjusting the energy of the laser, the preparation of a large-area laser-induced surface periodic structure can be achieved. At the same time, by adjusting the polarization direction of the laser, the direction of the periodic structure can be regulated, which provides a feasible solution for the preparation of large-scale surface periodic structures based on the surface of ferroelectric crystals, and has broad application prospects in the field of femtosecond laser subtractive micro-nano manufacturing. The method realizes the preparation of periodic structures on the surface of dielectric crystal materials at room temperature. At the same time, the method is simple to operate and can realize the preparation and promotion of large-scale surface periodic structures.

[0042] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0043] The following examples all adopt conventional polishing technology for polishing, and all adopt acetone, alcohol and deionized water to ultrasonically clean the polished dielectric crystal for 3 minutes in sequence.

[0044] Example 1

[0045] A method for preparing a periodic structure on the surface of a LiTaO3 crystal based on silver ion beam irradiation combined with femtosecond laser comprises the following steps:

[0046] (1) Cut the volume into 1×1×0.2cm 3 The LiTaO3 crystal 4 is polished and cleaned;

[0047] (2) Using an ion accelerator to emit energy of 70 keV and a dose of 5×10 16 ions / cm 2 Silver ions 1 bombard the polished surface of LiTaO3 crystal 4, forming an injection layer 3 below the directly bombarded polished surface, and forming a free silver element distribution 2 in the injection layer 3;

[0048] (3) placing a silver-injected LiTaO3 crystal 7 forming an injection layer 3 on a stage 8, adjusting the silver-injected LiTaO3 crystal 7 to a horizontal level by a six-axis translation stage 9, and then focusing a femtosecond laser beam 5 on the surface of the injection layer 3 through a focusing objective lens 6;

[0049] (4) The six-axis translation stage 3 is adjusted so that the surface of the injection layer 3 is lowered to a distance of 10 μm from the focus of the femtosecond laser. Lines are engraved on the surface of the injection layer 3 by moving the six-axis translation stage 9, and a laser-induced surface periodic structure can be obtained inside the engraved lines.

[0050] Figure 2 is the topography of the injection layer in this embodiment 1, Figure 2 It can be seen that an injection layer 3 is formed below the directly bombarded polished surface, and a free silver element distribution 2 is formed in the injection layer 3 . Figure 3 This is a morphology diagram of nanoparticles in the surface periodic structure obtained in Example 1. Figure 4 This is a morphology diagram of the surface periodic structure obtained in Example 1. It can be seen from the figure that the surface periodic structure is successfully constructed.

[0051] Example 2

[0052] A method for preparing a periodic structure on the surface of a LiNbO3 crystal based on gold ion beam irradiation combined with a femtosecond laser comprises the following steps:

[0053] (1) Cut the volume into 1×1×0.2cm 3 The LiNbO3 crystal 4 is polished and cleaned;

[0054] (2) Using an ion accelerator to emit energy of 70 keV and a dose of 5×10 16 ions / cm 2 Gold ions 1 bombard the polished surface of the LiNbO3 crystal, forming an injection layer 3 below the directly bombarded polished surface, and forming a free gold element distribution 2 in the injection layer 3;

[0055] (3) placing a gold-injected LiNbO3 crystal 7 forming an injection layer 3 on a stage 8, adjusting the gold-injected LiNbO3 crystal 7 to a horizontal position by a six-axis translation stage 9, and then focusing a femtosecond laser beam 5 on the surface of the injection layer 3 through a focusing lens 6;

[0056] (4) The six-axis translation stage 9 is adjusted so that the surface of the injection layer 3 is lowered to a distance of 10 μm from the focus of the femtosecond laser. Lines are engraved on the surface of the injection layer 3 by moving the six-axis translation stage 9, and a laser-induced surface periodic structure can be obtained inside the engraved lines.

[0057] Example 3

[0058] A method for preparing a periodic structure on the surface of a LiTaO3 crystal based on silver ion beam irradiation combined with femtosecond laser comprises the following steps:

[0059] (1) Cut the volume into 1×1×0.2cm 3 The LiTaO3 crystal 4 is polished and cleaned;

[0060] (2) The ion accelerator emits an energy of 160 keV and a dose of 5×10 16 ions / cm 2 Silver ions 1 bombard the polished surface of LiTaO3 crystal 4, forming an injection layer 3 below the directly bombarded polished surface, and forming a free silver element distribution 2 in the injection layer 3;

[0061] (3) placing a silver-injected LiTaO3 crystal 7 forming an injection layer 3 on a stage 8, adjusting the silver-injected LiTaO3 crystal 7 to a horizontal level by a six-axis translation stage 9, and then focusing a femtosecond laser beam 5 on the surface of the injection layer 3 through a focusing objective lens 6;

[0062] (4) The six-axis translation stage 3 is adjusted so that the surface of the injection layer 3 is lowered to a distance of 10 μm from the focus of the femtosecond laser. Lines are engraved on the surface of the injection layer 3 by moving the six-axis translation stage 9, and a laser-induced surface periodic structure can be obtained inside the engraved lines.

[0063] Example 4

[0064] A method for preparing a periodic structure on the surface of a LiTaO3 crystal based on silver ion beam irradiation combined with femtosecond laser comprises the following steps:

[0065] (1) Cut the volume into 1×1×0.2cm 3 The LiTaO3 crystal 4 is polished and cleaned;

[0066] (2) Using an ion accelerator to emit an energy of 200 keV and a dose of 5×10 16 ions / cm 2 Silver ions 1 bombard the polished surface of LiTaO3 crystal 4, forming an injection layer 3 below the directly bombarded polished surface, and forming a free silver element distribution 2 in the injection layer 3;

[0067] (3) placing a silver-injected LiTaO3 crystal 7 forming an injection layer 3 on a stage 8, adjusting the silver-injected LiTaO3 crystal 7 to a horizontal level by a six-axis translation stage 9, and then focusing a femtosecond laser beam 5 on the surface of the injection layer 3 through a focusing objective lens 6;

[0068] (4) The six-axis translation stage 3 is adjusted so that the surface of the injection layer 3 is lowered to a distance of 10 μm from the focus of the femtosecond laser. Lines are engraved on the surface of the injection layer 3 by moving the six-axis translation stage 9, and a laser-induced surface periodic structure can be obtained inside the engraved lines.

[0069] Example 5

[0070] A method for preparing a periodic structure on the surface of a LiTaO3 crystal based on silver ion beam irradiation combined with femtosecond laser comprises the following steps:

[0071] (1) Cut the volume into 1×1×0.2cm 3 The LiTaO3 crystal 4 is polished and cleaned;

[0072] (2) Using an ion accelerator to emit an energy of 400 keV and a dose of 5×10 16 ions / cm 2 Silver ions 1 bombard the polished surface of LiTaO3 crystal 4, forming an injection layer 3 below the directly bombarded polished surface, and forming a free silver element distribution 2 in the injection layer 3;

[0073] (3) placing a silver-injected LiTaO3 crystal 7 forming an injection layer 3 on a stage 8, adjusting the silver-injected LiTaO3 crystal 7 to a horizontal level by a six-axis translation stage 9, and then focusing a femtosecond laser beam 5 on the surface of the injection layer 3 through a focusing objective lens 6;

[0074] (4) The six-axis translation stage 3 is adjusted so that the surface of the injection layer 3 is lowered to a distance of 10 μm from the focus of the femtosecond laser. Lines are engraved on the surface of the injection layer 3 by moving the six-axis translation stage 9, and a laser-induced surface periodic structure can be obtained inside the engraved lines.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a periodic structure on the surface of a dielectric crystal by combining femtosecond laser with ion implantation at room temperature, characterized in that: include: The surface of the dielectric crystal is bombarded with metal ions to form an implantation layer; The femtosecond laser is focused on the surface of the injection layer of the dielectric crystal, the position of the dielectric crystal is lowered, and lines are engraved on the surface of the injection layer by moving the position of the dielectric crystal to obtain a surface periodic structure.

2. The method according to claim 1, characterized in that The method further comprises the step of pre-treating the dielectric crystal, and after the pre-treatment, bombarding the surface of the dielectric crystal with metal ions; Wherein, the pretreatment includes: cutting, polishing and cleaning the dielectric crystal; Preferably, the cutting is to cut the dielectric crystal into 1×1×0.2 cm 3 of crystal blocks.

3. The method according to claim 2, characterized in that The polishing is to polish two side surfaces and one large surface of the cut dielectric crystal.

4. The method according to claim 2, characterized in that The cleaning is to use acetone, alcohol and deionized water to ultrasonically clean the polished dielectric crystal.

5. The method according to claim 1, characterized in that The dielectric crystal is a lithium tantalate crystal or a lithium niobate crystal.

6. The method according to claim 1, characterized in that The metal ions are gold particles or silver ions.

7. The method according to claim 1, characterized in that The bombardment, the metal ion energy is 70-400keV, the dose is 5×10 16 ions / cm 2 .

8. The method according to claim 1, characterized in that The injection layer is located below the surface of the bombarded dielectric crystal, and the thickness of the injection layer is 60-100 nm.

9. The method according to claim 1, characterized in that The femtosecond laser used for processing has a pulse width of 110fs, a repetition frequency of 1kHz, a central wavelength of 800nm, and a scanning speed of 0.01-1mm / s.

10. The method according to claim 1, characterized in that After the position of the dielectric crystal is lowered, the distance between the dielectric crystal and the focus of the femtosecond laser is 5-20 μm.

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