CN110899957A

CN110899957A - Method for realizing information display and encryption based on femtosecond laser induced segmentation pattern

Info

Publication number: CN110899957A
Application number: CN201911179450.0A
Authority: CN
Inventors: 王文君; 孙小云; 梅雪松; 张祎霖; 崔健磊
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2019-11-27
Filing date: 2019-11-27
Publication date: 2020-03-24
Anticipated expiration: 2039-11-27
Also published as: CN110899957B

Abstract

A method for realizing information display and encryption based on femtosecond laser induced segmentation patterns comprises the steps of firstly, adopting a metal film with Ti and Au deposited on a glass substrate in sequence as a processing object; then, a light path is set up, a femtosecond laser is adjusted by a computer to output laser, the laser wavelength is 1030nm, the pulse width is 240fs, the repetition frequency is 1-200kHz, and the maximum single-pulse energy is 200 muJ; fixing the sample on a processing station of a scissor lift table, adjusting laser energy, scanning speed and scanning interval, equally dividing the pattern by 100 mu m, and respectively preparing laser-induced periodic surface structures LISSs with mutually vertical directions in the divided adjacent areas; according to the invention, the femtosecond laser is adopted to induce and divide adjacent areas of the pattern to prepare the LISSs with mutually vertical directions, so that the information display range is enlarged, and the information encryption is realized.

Description

Method for realizing information display and encryption based on femtosecond laser induced segmentation pattern

Technical Field

The invention belongs to the technical field of laser pattern manufacturing, and particularly relates to a method for realizing information display and encryption based on femtosecond laser induced segmentation patterns.

Background

Color is an important feature of natural objects, and the application of color in the field of information has attracted considerable attention in recent years. Physical color is the selective reflection and transmission of visible light through the microstructure of an object, also known as structural color. The physical color is not only not faded, but also very environment-friendly.

Metals are one of the most widely used materials for making structural colors due to their durability, toughness and flexibility, but only structural colors in reflective mode can be obtained on metal blocks, while structural colors in reflective and transmissive modes can be obtained on metal films. Compared with other metal coloring technologies such as anodic oxidation, electroplating, cold and hot enamel coating and powder coating, laser processing has the advantages of no contact force, high flexibility and the like. In addition, the interaction time between the femtosecond laser and the material is very short, so the femtosecond laser has an advantage of cold working.

Laser Induced Periodic Surface Structures (LIPSSs) are one of the most common methods of laser coloration, and LIPSSs can be considered as a diffraction grating that can act as a dispersive medium to produce different colors. The observation of the structural color depends on the incident angle of the light source and the azimuth angle of the moire, but when the incident angle of the light source is constant, the pattern display is related to the azimuth angle of the moire, so that the pattern can be observed only in a certain range, and the pattern display range is small.

Disclosure of Invention

In order to overcome the disadvantages of the prior art, the present invention provides a method for implementing information display and encryption based on femtosecond laser induced segmentation patterns, which expands the range of color pattern display and implements information encryption.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for realizing information display and encryption based on femtosecond laser induced segmentation patterns comprises the following steps:

1) adopting a metal film as a processing object, wherein 100nm Ti and 20nm Au are sequentially deposited on a glass substrate;

2) the method comprises the following steps of building a light path, enabling output light of a femtosecond laser 1 to sequentially pass through a half-wave plate 2, a Glan Taylor prism 3, a beam expander 4 and a small-hole diaphragm 5, and finally to be focused on a shear type lifting table 7 through a two-axis scanning galvanometer system 6, wherein the femtosecond laser 1 and the two-axis scanning galvanometer system 6 are connected with a computer;

3) adjusting the output laser of the femtosecond laser 1 by using a computer, wherein the laser wavelength is 1030nm, the pulse width is 240fs, the repetition frequency is 1-200kHz, and the maximum single pulse energy is 200 muJ;

4) fixing a sample on a processing station of a scissor type lifting table 7, adjusting laser energy and scanning speed to obtain the optimal basic parameters of the laser-induced periodic surface structure: the laser energy is 400-500mW, the scanning speed is 100-450mm/s, and the scanning interval is 5 μm; the pattern is divided equally by 100 μm and laser induced periodic surface structures LIPSSs are prepared in mutually perpendicular directions in the divided adjacent regions, respectively.

The color display range of the information is expanded when one beam of white light irradiates the laser-induced periodic surface structure LIPSS, and the information is encrypted when two beams of white light irradiate the laser-induced periodic surface structure LIPSS.

The invention has the beneficial effects that:

LIPSS with mutually perpendicular directions are respectively prepared by adopting the adjacent areas of the femtosecond laser induced segmentation pattern, so that the information display range is expanded, and the information encryption is realized. The generation direction of LIPSSs depends on the polarization direction of the laser light, so changing the polarization direction of the laser light results in different moire directions of different areas of the segmentation pattern. The observation of the structural color depends on the incident angle of the light source and the azimuth angle of the moire. When the light source incident angle is constant, the resulting pattern appears to be related to the moire direction angle: when the corrugation direction angle is 90 degrees, the LIPSSs have the strongest light splitting effect, and the pattern color display quality is the best; while LISSs has no light splitting effect when the moire orientation angle is 0 deg., no color is observed. The method of equally dividing the pattern and filling horizontal and vertical LIPSSs in the neighboring area does not affect the recognizability of the pattern and also doubles the color display range of the pattern. When two light sources irradiate the pattern at the same incident angle, the pattern and the substrate containing the pattern integrally present a color, thereby hiding the pattern and realizing the encryption of information.

Drawings

FIG. 1 is a schematic diagram of the optical path of the present invention.

FIG. 2 is a schematic diagram of pattern structure color measurement according to the present invention.

Fig. 3 is a graph showing the result of irradiating the division pattern with white light in the XZ plane in example 1.

Fig. 4 is a graph showing the result of irradiating a division pattern with white light in YZ plane according to example 2.

Fig. 5 is a graph showing the results of example 3 in which two white lights simultaneously irradiate a division pattern in the XZ plane and the YZ plane.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

Embodiment 1, a method for implementing information display and encryption based on femtosecond laser induced segmentation patterns, comprising the following steps:

1) 100nm Ti and 20nm Au are sequentially deposited on a glass substrate, and the area is 2 multiplied by 2cm²The metal film of (2) as a processing object;

2) building a light path, referring to fig. 1, outputting light of a femtosecond laser 1 sequentially passes through a half-wave plate 2, a Glan Taylor prism 3, a beam expander 4 and a small aperture diaphragm 5, and is finally focused on a shear type lifting platform 7 through a biaxial scanning galvanometer system 6, wherein the femtosecond laser 1 and the biaxial scanning galvanometer system 6 are connected with a computer;

4) fixing a sample on a processing station of a scissor type lifting table 7, adjusting laser energy and scanning speed to obtain the optimal basic parameters of the laser-induced periodic surface structure: the laser energy is 400mW, the scanning speed is 200mm/s, and the scanning distance is 5 mu m; the butterfly pattern was equally divided by 100 μm, and LIPSSs were prepared in mutually perpendicular directions in adjacent divided regions, respectively.

Referring to FIG. 2, the light source and the microscope are located on an XZ plane, the microscope is parallel to the Z axis, the included angle α between the light source and the Z axis ranges from 0 to 90 degrees, the LISSs sample is located on an XY plane, and the included angle theta between the LISSs and the X axis ranges from 0 to 180 degrees;

the white light irradiates the division pattern at different incident angles in the XZ plane and changes the color display range of the moire direction angle observation pattern.

The beneficial effect of this embodiment does: referring to fig. 3, the present embodiment shows a butterfly pattern due to the white light diffraction division pattern, and different colors of butterflies can be obtained by changing the incident angle of the white light, and as the incident angle is reduced from 55 ° to 30 °, the color of the pattern changes from red to blue; by changing the orientation angle of the corrugations, the pattern is displayed in color in a range of about 30 °.

Example 2, the direction of white light irradiation in example 1 was set in the YZ plane.

The beneficial effect of this embodiment does: referring to fig. 4, it can be seen that the pattern segmentation does not affect the identification of butterfly information, and as the incident angle of white light is reduced from 55 ° to 30 °, the color of the butterfly changes from red to blue. At this time, the corrugation direction angle is changed, and the pattern color display range is about 30 degrees; thus the range of butterfly display is about doubled when the sample is rotated 180 °.

Example 3, example 1 was set up such that two white lights simultaneously illuminate a divided pattern in the XZ plane and the YZ plane.

The beneficial effect of this embodiment does: referring to fig. 5, in this embodiment, when the incident angles of the two white lights are different, a butterfly pattern with a color different from that of the substrate can be obtained; when the incidence angles of the two beams of white light are the same (55 degrees), the butterfly and the substrate containing the butterfly integrally show a color, so that the butterfly pattern is hidden, and the information encryption is realized.

Claims

1. A method for realizing information display and encryption based on femtosecond laser induced segmentation patterns is characterized by comprising the following steps:

2) the method comprises the following steps of building a light path, enabling output light of a femtosecond laser (1) to sequentially pass through a half-wave plate (2), a Glan Taylor prism (3), a beam expander (4) and a small aperture diaphragm (5), and finally to be focused on a shear type lifting table (7) through a biaxial scanning galvanometer system (6), wherein the femtosecond laser (1) and the biaxial scanning galvanometer system (6) are connected with a computer;

3) a computer is utilized to adjust the femtosecond laser (1) to output laser, the laser wavelength is 1030nm, the pulse width is 240fs, the repetition frequency is 1-200kHz, and the maximum single pulse energy is 200 muJ;

4) fixing a sample on a processing station of a scissor type lifting table (7), adjusting laser energy and scanning speed to obtain the optimal basic parameters of the laser-induced periodic surface structure: the laser energy is 400-500mW, the scanning speed is 100-450mm/s, and the scanning interval is 5 μm; the pattern is divided equally by 100 μm and laser induced periodic surface structures LIPSSs are prepared in mutually perpendicular directions in the divided adjacent regions, respectively.

2. The method of claim 1, wherein the method comprises the steps of: the color display range of the information is expanded when one beam of white light irradiates the laser-induced periodic surface structure LIPSS, and the information is encrypted when two beams of white light irradiate the laser-induced periodic surface structure LIPSS.