CN110732789A

CN110732789A - heat-assisted femtosecond laser processing method

Info

Publication number: CN110732789A
Application number: CN201911008973.9A
Authority: CN
Inventors: 张帆; 赵于前; 段吉安
Original assignee: Central South Univ
Current assignee: Central South Univ
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-01-31

Abstract

The invention provides a method for processing heat-assisted femtosecond laser, which belongs to the technical field of optics, and the method utilizes a temperature control system to preheat a material, accurately controls the temperature of the material, and then enables the focused femtosecond laser to act on the preheated material, thereby efficiently processing a sample.

Description

heat-assisted femtosecond laser processing method

Technical Field

The invention belongs to the technical field of optics, and particularly relates to a method for efficiently processing a microporous structure on the surface of a material by femtosecond lasers.

Background

The focused high energy density laser beam femtosecond laser is utilized to achieve cold processing compared with the traditional long pulse laser, is widely applied to processing of various materials such as metals, semiconductors and insulators, the laser pulse is focused in a micro area through an objective lens to obtain extremely high power density, and the laser pulse shows a strong nonlinear phenomenon when acting with the materials, energy can be deposited in the focused area of the materials in an extremely short time through avalanche ionization and photoionization processes to generate local plasma expansion, so that the effective refractive index of the materials is changed, and the materials are modified or removed.

Disclosure of Invention

The invention aims to provide femtosecond laser manufacturing methods capable of efficiently processing a material surface micropore structure.

The method comprises the following specific steps.

1. The hot plate was fixed on a three-dimensional platform and then the sample was placed on the hot plate.

2. And controlling the temperature of the surface of the heating plate by using a temperature control system so as to control the temperature of the surface of the sample. Realize the preheating treatment of the sample.

3. The energy of the incident laser is adjusted by an attenuation sheet in a femtosecond laser processing system, and the pulse number of the incident laser is controlled by a light gate. And processing the microporous structure on the surface of the sample by fixing the laser energy and the pulse number.

4. The temperature control system is used for controlling the preheating environments with different temperatures, and the three-dimensional platform is matched to move, so that the efficient machining of the microporous structures with different depths is finally realized.

The invention realizes the preheating treatment of the processed material at different temperatures by using the temperature control system, has the characteristic of reducing the processing threshold of the material, ensures that phonons in the material vibrate violently by using the rise of the external temperature, is further favorable for capturing incident photons, intensifies the interaction between the laser and the material, deepens the depth of a surface micropore structure by steps under the condition of the same laser parameters, and promotes the high-efficiency processing of the femtosecond laser.

The basic principle of the present invention is as follows.

In addition, in the aspect, the energy of a crystal lattice phonon of the sample can be increased along with the increase of the external temperature, and the phenomenon that the internal phonon vibrates more severely is shown, so that the phonon which vibrates violently can capture more incident photons to realize the interaction between the phonon and the photons, so that the focused femtosecond laser can remove more materials to realize the processing of a deep hole structure.

The invention has the advantages that the incident laser energy required for processing the deep hole can be very small, the laser energy is effectively saved, and the invention has broad application prospect in a plurality of fields such as precision manufacturing, space flight instruments, biological medical treatment and the like.

Drawings

FIG. 1 is a schematic diagram of a thermally-assisted femtosecond laser processing system

Reference numbers in the figures: the device comprises a light source 1, a lens 2, a spectroscope 3, a Charge Coupled Device (CCD) 4, a dichroic mirror 5, an objective lens 6, an attenuation sheet 7, a diaphragm 8, a reflector 9, a shutter 10, a sample 11, a heating plate 12, a three-dimensional platform 13, a temperature controller 14 and a femtosecond laser 15.

FIG. 2 is a surface micropore structure profile of PMMA material under different heating temperature T conditions.

Detailed Description

The following describes an embodiment of the present invention by way of an example of femtosecond laser processing of the surface micro-porous structure of a PMMA sample.

1. Firstly, fixing a PMMA sample on a heating plate, and fixing the heating plate on a three-dimensional platform. And the heating plate is connected with a temperature control system, so that the accurate control of the heating temperature is realized.

2. A femtosecond laser processing system as shown in fig. 1 was constructed. The light source and the CCD are matched to observe the relative position of the laser processing focus and the surface of the sample, so that the processing of the PMMA surface microporous structure is realized.

3. The attenuation plate is used for adjusting the energy of the incident laser to 10 milliwatts, and the optical gate controls the pulse number of the incident laser of single processing to be 100. The femtosecond laser focusing uses a 10-fold objective lens.

4. The temperature setting range of the temperature control system is from room temperature (20 ℃ C.) to 80 ℃ C, and the preheating temperature is 20 ℃ apart each time.

5. And under each preheating temperature condition, processing the surface microporous structure of the single PMMA by femtosecond laser with the same preset parameters.

6. The outline of the PMMA surface microporous structure is shown in fig. 2. From the result graph, it can be seen that as the preheating temperature is changed to 20 ℃, 40 ℃, 60 ℃ and 80 ℃, the depth-to-strain of the micropores is 1.0 μm, 2.2 μm, 3.7 μm and 6.9 μm. The maximum change of the depth of the micro-hole reaches 6.9 times, and the fact that the depth of the micro-hole machined by the femtosecond laser can be effectively increased by a heat auxiliary mode is proved.

7. The processing effect of the method of the invention depends on the melting point of the material and the preheating temperature. The melting point of the PMMA material is 120 ℃, so that the PMMA material is closer to the melting point value when the preheating temperature is 80 ℃. Finally, the depth of the micro-hole processed by the femtosecond laser has a larger value.

In conclusion, the invention provides methods for processing the micropore structure on the surface of the material by femtosecond laser, and uses PMMA material as an example, and compares the depths of the micropore structure processed by the femtosecond laser under different preheating temperature conditions to verify the feasibility of the method.

Claims

The heat-assisted processing method based on the femtosecond laser is characterized by comprising the specific steps of fixing a temperature control system on a three-dimensional platform, preheating a material by using the temperature control system, fixing a sample on a heating platform, focusing the femtosecond laser through an objective lens, and processing the preheated sample, wherein the temperature control system can accurately control the preheating temperature of the sample, and the position of the three-dimensional platform is controlled through a program, so that a required structure is processed on the sample, the sample can be modified through preheating, phonon vibration in a modification area is intensified, photons can be captured more effectively, violent interaction between the laser and a substance is realized, and the depth of a micropore processed from the surface of the sample in a macroscopic view can be shown, and the depth of the micropore is gradually increased along with the increase of the preheating temperature.
2. The method of claim 1, wherein: the preheating temperature can be controlled by a temperature control system, the temperature is changed from room temperature to 300 ℃, and the precision can reach 0.1 ℃.
3. The method of claim 1, wherein: the sample material used is PMMA, but the method is not limited to PMMA only, and can also be applied to other sample materials with the melting point of less than 300 ℃.
4. The method of claim 1, wherein the femtosecond laser passes through a 10-fold objective lens to remove surface materials, but not limited to the objective lens, and the method further comprises using the lens focus and the femtosecond laser to directly irradiate the surface materials.
5. The method of claim 1, wherein: the sample surface is processed with a micropore structure, the depth of which is increased along with the increase of the preheating temperature, but the micropore structure is only limited to, and the groove structure is also included.
6. The method of claim 1, wherein: the set incident femtosecond laser energy was 10 mw, and the number of pulses was 100.