Method and system for preparing bilinear waveguide fork-shaped grating through femtosecond laser direct writing

Abstract

The invention provides a method and a system for preparing a bilinear waveguide fork-shaped grating through femtosecond laser direct writing. The method comprises the following steps: polishing and cleaning a cut crystal; enabling femtosecond laser to enter the inside from the large surface of the processed crystal to prepare a bilinear diffusion waveguide; and preparing a fork-shaped grating at the emergent end of the prepared bilinear diffused waveguide. The femtosecond laser is utilized to modify the inside of the crystal, the composite integrated device of the bilinear waveguide fork-shaped grating is prepared, the integrated device is simple in structure, small in size and low in cost, large-scale output of a vortex laser array can be achieved, and a new thought is provided for the invention of a vortex laser transmitter in the crystal. The method can be applied to most transparent materials, and has the advantages of easiness in processing, simple process, short time and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated optical devices, and in particular relates to a method and a system for preparing a double-line waveguide fork grating by direct writing with a femtosecond laser. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Femtosecond laser direct writing technology changes the properties of transparent dielectric crystals by controlling laser energy, scanning speed, repetition frequency and other conditions. Since its emergence, this technology has been widely used in many fields such as micro-nano special manufacturing, integrated optics, biomedicine, etc., and has broad application prospects.

[0004] Lasers are usually divided into four categories: gas lasers, solid-state lasers, semiconductor lasers, and dye lasers. The working medium of solid-state lasers is laser crystals. Common yttrium aluminum garnet crystals doped with trivalent neodymium ions can be used to generate near-infrared lasers with a central wavelength of 1064nm. In addition, Nd:YAP crystals are also ideal materials for near-infrared laser generation and have good application prospects.

[0005] In the spatial dimension of photons, the spatial configuration of the light field can be manipulated by the spatial distribution of phase, polarization and intensity. This special light field is called structured light. Vortex beams have extremely broad application prospects in particle manipulation, optical communications and super-resolution imaging. Therefore, vortex beams have received more and more attention, and there are more and more ways to generate vortex beams, such as fork gratings (FG), q-glass, spiral phase plates, spatial light modulators (SLM), etc. Fork gratings are one of the most effective ways to generate vortex beams due to their simple structure and manufacturing methods. With the trend of miniaturization of optical devices, reducing the size of fork gratings for application in integrated optical devices is an important topic. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a method and system for preparing a double-line waveguide fork grating by femtosecond laser direct writing. The present invention can prepare a micron-level double-line waveguide fork grating integrated device, which can be applied to most transparent materials and has the advantages of easy processing, simple process, short time and low cost.

[0007] According to some embodiments, the present invention adopts the following technical solutions:

[0008] A method for preparing a double-line waveguide fork grating by femtosecond laser direct writing comprises the following steps:

[0009] Polish and clean the cut crystals;

[0010] The femtosecond laser is incident from the large surface of the processed crystal into the interior to prepare a double-line diffuse waveguide;

[0011] A fork-shaped grating is prepared at the output end of the prepared double-line diffusion waveguide.

[0012] As an optional embodiment, the cut crystal is a square crystal block cut into a predetermined size.

[0013] As an optional implementation, the process of polishing the crystal is to polish two opposite side faces and one of the large faces of the cut crystal.

[0014] As an optional implementation, the process of cleaning the crystal is to ultrasonically clean the crystal with acetone, alcohol, and deionized water respectively.

[0015] As an optional embodiment, the crystal is a Tm:YAP crystal or a Nd:YAP crystal.

[0016] As an optional implementation, the dual-line diffusion waveguide is arranged axially symmetrically, and the diameter of the output end is larger than the diameter of the input end.

[0017] As an optional embodiment, when the femtosecond laser is incident from the large surface of the processed crystal to the inside, the laser scanning speed is 0.1-1 mm / s, the diameter of the incident end of the diffusion waveguide is 15-20 μm, and the diameter of the output end is 30-50 μm.

[0018] As an optional embodiment, the scanning speed of the process for preparing the fork-shaped grating is 0.02 mm / s, and the period of the fork-shaped grating is 3.9-4.5 μm.

[0019] As an optional implementation, the method further includes testing the waveguide performance of the prepared waveguide fork grating integrated device.

[0020] A system for preparing a double-line waveguide fork grating by femtosecond laser direct writing, comprising:

[0021] Polishing equipment, used to polish the cut crystals;

[0022] Cleaning equipment, used to clean the polished crystal;

[0023] The femtosecond laser direct writing device is used to inject the femtosecond laser into the inside of the processed crystal from the large surface, so as to prepare a double-line diffusion waveguide; and to prepare a fork grating at the output end of the prepared double-line diffusion waveguide.

[0024] As an optional embodiment, a cutting device is further included for cutting the crystal.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention adopts the method of femtosecond laser direct writing processing to prepare a diffused double-line waveguide inside the crystal, and amplifies it to match the fork grating of corresponding size on the basis of maintaining the laser mode, thereby ensuring the diffraction efficiency of the fork grating and outputting a vortex laser array at the same time. The output of a large-scale vortex laser array is realized with a simple composite structure.

[0027] 2. The present invention is applicable to various types of optical crystals. It utilizes a simple processing method to combine two simple integrated optical components, which provides the possibility for vortex laser array transmitters in integrated optics and greatly enriches the application possibilities of crystal materials.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. 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 The schematic diagram of the structure of a double-line waveguide fork grating prepared by femtosecond laser direct writing in one embodiment;

[0031] Among them: 1. Transparent dielectric crystal, 2. Double-line diffused waveguide, 3. Fork grating. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] In the absence of conflict, the embodiments in this application and the features in the embodiments may be combined with each other.

[0036] Example 1

[0037] A method for preparing a double-line waveguide fork grating by femtosecond laser comprises the following steps:

[0038] (1) Polishing and cleaning the cut crystals;

[0039] (2) Femtosecond laser is incident from the large surface of the sample into the interior to prepare a double-line diffuse waveguide;

[0040] (3) preparing a fork grating at the output end of the waveguide in the crystal processed in step (2);

[0041] (4) Testing the waveguide performance of the prepared waveguide fork grating integrated device using end-face coupling testing technology;

[0042] In this embodiment, in step (1), the crystal is cut into square crystal blocks of 1 cm×1 cm×0.2 cm.

[0043] In this embodiment, in step (1), the crystal polishing is to polish two opposite side surfaces and one large surface of the cut crystal.

[0044] Polishing is carried out using existing polishing technology.

[0045] In this embodiment, in step (1), the crystal is cleaned by ultrasonically cleaning the crystal with acetone, alcohol, and deionized water respectively.

[0046] In this embodiment, in step (1), the crystal is a Tm:YAP crystal or a Nd:YAP crystal.

[0047] In this embodiment, in step (2), the laser is focused inside the sample to carve two parallel lines as the straight waveguide part in the diffusion waveguide, and then two lines with a certain inclination angle are carved at the end of the straight waveguide, so that the distance between the ends of the lines is greater than the waveguide diameter of the straight waveguide. The scanning speed of the processing is 0.1-1mm / s, the diameter of the incident end of the diffusion waveguide is 15-20μm, and the diameter of the exit end is 30-50μm.

[0048] In this embodiment, in step (3), the processing scanning speed is 0.02 mm / s, and the period of the fork grating is 3.9-4.5 μm.

[0049] This embodiment uses femtosecond laser to modify the inside of the crystal to prepare a composite integrated device of a double-line waveguide fork grating. The integrated device has a simple structure, small size, and low cost. It can achieve the output of a large-scale vortex laser array, and provides a new idea for the invention of a vortex laser emitter in a crystal.

[0050] Example 2

[0051] A method for preparing a Nd:YAP crystal double-line waveguide fork grating based on femtosecond laser direct writing, comprising the following steps:

[0052] (1) polishing and cleaning the cut Nd:YAP crystal 1;

[0053] (2) The double-line waveguide 2 is prepared by femtosecond laser direct writing technology. The scanning speed during processing is 0.5 mm / s. The width of the incident end of the prepared double-line waveguide 2 is 20 μm, and the width of the output end is 50 μm. Figure 1 As shown;

[0054] (3) The fork-shaped grating 3 was prepared by femtosecond laser direct writing technology, the scanning speed during processing was 0.02 mm / s, and the prepared grating period was 4.5 μm;

[0055] (4) The light guiding and diffraction performance of the waveguide grating are tested using end-face coupling test technology.

[0056] Example 3

[0057] A method for preparing a Tm:YAP crystal double-line waveguide fork grating based on femtosecond laser direct writing, comprising the following steps:

[0058] (1) polishing and cleaning the cut Tm:YAP crystal 1;

[0059] (2) The double-line waveguide 2 is prepared by femtosecond laser direct writing technology. The scanning speed during processing is 0.5 mm / s. The width of the incident end of the prepared double-line waveguide 2 is 20 μm, and the width of the output end is 50 μm.

[0060] (3) The fork-shaped grating 3 was prepared by femtosecond laser direct writing technology, the scanning speed during processing was 0.02 mm / s, and the prepared grating period was 4.5 μm;

[0061] (4) The light guiding and diffraction performance of the waveguide grating are tested using end-face coupling test technology.

[0062] 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 by those skilled in the art within the spirit and principle of the present invention without creative labor shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a double-line waveguide fork grating by femtosecond laser direct writing, characterized in that: The following steps are involved: Polish and clean the cut crystals; The femtosecond laser is incident from the large surface of the processed crystal into the interior to prepare a double-line diffuse waveguide; A fork-shaped grating is prepared at the output end of the prepared double-line diffusion waveguide.

2. The method for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 1, characterized in that: The cut crystal is a square crystal block cut into a predetermined size; Or, the crystal is a Tm:YAP crystal or a Nd:YAP crystal.

3. The method for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 1, characterized in that: The process of polishing the crystal is to polish the two opposite side faces and one of the large faces of the cut crystal.

4. The method for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 1, characterized in that: The process of cleaning the crystal is to ultrasonically clean the crystal with acetone, alcohol and deionized water respectively.

5. The method for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 1, characterized in that: The double-line diffusion waveguide is arranged axially symmetrically, and the diameter of the output end is larger than the diameter of the input end.

6. A method for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 1 or 5, characterized in that: In the process of incident femtosecond laser from the large surface of the processed crystal to the inside, the laser scanning speed is 0.1-1mm / s, the diameter of the incident end of the diffusion waveguide is 15-20μm, and the diameter of the output end is 30-50μm.

7. The method for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 1, characterized in that: The scanning speed of the fork-shaped grating was 0.02 mm / s, and the period of the fork-shaped grating was 3.9-4.5 μm.

8. A method for preparing a dual-line waveguide fork grating by femtosecond laser direct writing according to any one of claims 1 to 7, characterized in that: It also includes testing the waveguide performance of the prepared waveguide fork grating integrated device.

9. A system for preparing a double-line waveguide fork grating by femtosecond laser direct writing, characterized in that: include: Polishing equipment, used to polish the cut crystals; Cleaning equipment, used to clean the polished crystal; The femtosecond laser direct writing device is used to inject the femtosecond laser into the inside of the processed crystal from the large surface, so as to prepare a double-line diffusion waveguide; and to prepare a fork grating at the output end of the prepared double-line diffusion waveguide.

10. A system for preparing a double-line waveguide fork grating by femtosecond laser direct writing as claimed in claim 9, characterized in that: Also included is a cutting device for cutting the crystal.

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