Femtosecond laser pulse width control device

Abstract

The utility model discloses a femtosecond laser pulse width control device, comprising a light source module comprising a light source, a stretcher, an amplifier and a beam expanding collimation assembly which are successively arranged along a light path; the compression module is used for adjusting the pulse width and comprises a first reflecting mirror, a compressor and a second reflecting mirror, the compressor is used for compressing the pulse into a transformation limit pulse and comprises a first grating, a second grating, a climbing mirror and an adjusting mechanism, the first grating is located between the first reflecting mirror and the second reflecting mirror, and the second grating is located between the first reflecting mirror and the second reflecting mirror; the adjusting mechanism is used for adjusting the distance between the first grating and the second grating; the detection module comprises a polarization beam splitter, a frequency doubling crystal, a dichroic mirror and a power meter, and the power meter is used for detecting the power of the frequency doubling light; and the feedback control module is used for feeding back the power of the frequency doubling light and controlling the compression module. According to the utility model, the detection structure can be simplified, the equipment cost is reduced, and packaging in a standard industrial laser is easy to realize.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, specifically to a femtosecond laser pulse width control device. Background Technology

[0002] Femtosecond lasers are widely used in industrial processing, medical fields and other fields, and the pulse width stability of femtosecond lasers is of great importance in many aspects.

[0003] In the industrial field, a stable pulse width helps maintain the consistency of laser-material interaction, ensuring that the amount of material removed and the processing effect are stable with each pulse, avoiding over- or under-processing caused by pulse width fluctuations. As a result, processing time and costs can be reduced, and processing efficiency can be improved.

[0004] In the medical field, a stable pulse width ensures the uniform distribution of laser energy within the target area, reducing surgical risks and improving surgical safety and success rates.

[0005] Currently, high-power femtosecond lasers all employ a chirped pulse amplification structure, which involves pulse broadening and pulse amplification to prevent damage to optical components due to excessively high peak power during the amplification process.

[0006] The detection of femtosecond laser pulse width is usually accomplished by an autocorrelator. However, autocorrelators are complex in structure, expensive, and difficult to implement in standard industrial lasers. Utility Model Content

[0007] To overcome the shortcomings of the existing technology, this utility model provides a femtosecond laser pulse width control device, which can simplify the detection structure, reduce equipment costs, and is easy to package into a standard industrial laser.

[0008] The technical solution adopted by this utility model to solve its technical problem is:

[0009] A femtosecond laser pulse width control device, comprising:

[0010] The light source module includes a light source, a stretcher, an amplifier, and a beam expander and collimator arranged sequentially along the optical path;

[0011] A compression module for adjusting pulse width includes a first reflector, a compressor, and a second reflector. The compressor is used to compress the pulse into a transform-limited pulse.

[0012] The detection module includes a polarizing beam splitter, a frequency doubling crystal, a dichroic mirror, and a power meter, wherein the power meter is used to detect the power of the frequency-doubled light;

[0013] The feedback control module is used to provide feedback on the power of the frequency-doubled light and control the compression module.

[0014] As a further improvement to the above technical solution, the beam expanding and collimating assembly includes a first plano-concave lens and a first plano-convex lens arranged sequentially along the optical path.

[0015] As a further improvement to the above technical solution, the compressor includes a first grating, a second grating, a climbing mirror, and an adjustment mechanism. The first grating is located between the first reflector and the second reflector, and the adjustment mechanism is used to adjust the distance between the first grating and the second grating.

[0016] As a further improvement to the above technical solution, the adjustment mechanism includes an electric displacement stage, the second grating and the climbing mirror are disposed on the electric displacement stage, and the electric displacement stage is used to drive the second grating and the climbing mirror to translate together.

[0017] As a further improvement to the above technical solution, the first grating and the second grating have the same parameters, the number of lines of the first grating and the second grating is 1600 lines / mm, the center wavelength is 1030nm, and the single-pass loss is less than 2%.

[0018] As a further improvement to the above technical solution, the climbing mirror includes two third reflecting mirrors.

[0019] As a further improvement to the above technical solution, the detection module also includes a second plano-convex lens, which is located between the polarizing beam splitter and the frequency doubling crystal. The second plano-convex lens is used to focus the detection light onto the frequency doubling crystal.

[0020] As a further improvement to the above technical solution, a first half-wave plate is provided between the second reflector and the polarizing beam splitter.

[0021] As a further improvement to the above technical solution, a second half-wave plate is provided between the polarizing beam splitter and the second plano-convex lens.

[0022] As a further improvement to the above technical solution, a baffle is provided on one side of the dichroic mirror, which is used to block and absorb the fundamental frequency light after the dichroic mirror has high transmission.

[0023] The beneficial effects of this invention are as follows: This invention provides a femtosecond laser pulse width control device. By setting up a light source module, a compression module, a detection module, and a feedback control module, the light beam enters the compressor, which is responsible for providing negative dispersion for the pulse, compressing the pulse into a transform-limited pulse. The compressed pulse is reflected by a second mirror to a polarizing beam splitter. Part of the light is transmitted through the polarizing beam splitter as detection light. The detection light enters a frequency doubling crystal, which converts the fundamental frequency light into frequency-doubled light, and then enters a dichroic mirror. The dichroic mirror has high reflectivity for the wavelength of the frequency-doubled light, and the reflected green light enters a power meter for detection. The detected data is then transmitted to the feedback control module. In the module, when the pulse energy and average power remain constant, the pulse width of the femtosecond laser is inversely proportional to the peak power. During the frequency doubling process, the conversion efficiency is related to the peak power density. If the spot size remains constant, it is directly related to the peak power or the pulse width. Therefore, the pulse width can be indirectly determined by detecting the power of the green light after the femtosecond laser frequency doubling. When the power of the frequency-doubled light changes, the feedback control module controls the adjustment mechanism in the compression module to adjust the spacing between the first and second gratings, thereby achieving automatic adjustment of the pulse width. This simplifies the detection structure, reduces equipment costs, and makes it easy to package in a standard industrial laser. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 This is a schematic diagram of the optical path of a femtosecond laser pulse width control device according to an example of this utility model.

[0026] Reference numerals: 1-Light source, 2-Stretcher, 3-Amplifier, 4-Beam expander and collimator assembly, 401-First plano-concave lens, 402-First plano-convex lens, 5-First reflector, 6-Compressor, 601-First grating, 602-Second grating, 603-Climbing mirror, 604-Adjustment mechanism, 7-Second reflector, 8-Polarizing beam splitter, 9-Frequency doubling crystal, 10-Dichroic mirror, 11-Power meter, 12-Feedback control module, 13-Second plano-convex lens, 14-First half-wave plate, 15-Second half-wave plate, 16-Baffle. Detailed Implementation

[0027] The following will clearly and completely describe the concept, specific structure, and technical effects of this utility model in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are all within the scope of protection of this utility model. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this utility model can be combined interactively without contradicting each other.

[0028] Reference Figure 1 This utility model provides a femtosecond laser pulse width control device, which includes a light source module, a compression module, a detection module and a feedback control module 12.

[0029] Functionally, the light source module is used to emit pulses, the compression module is used to adjust the pulse width, the detection module is used to detect the power of the frequency-doubled light, and the feedback control module 12 is used to provide feedback on the power of the frequency-doubled light and control the compression module.

[0030] Structurally, the light source module includes a light source 1, a stretcher 2, an amplifier 3, and a beam expander and collimator 4 arranged sequentially along the optical path. The compression module includes a first reflector 5, a compressor 6, and a second reflector 7. The compressor 6 is used to compress the pulse into a transform-limited pulse. The detection module includes a polarizing beam splitter 8, a frequency doubling crystal 9, a dichroic mirror 10, and a power meter 11. The power meter 11 is used to detect the power of the frequency doubling light.

[0031] Specifically, the laser emitted from light source 1 is broadened by stretcher 2, then amplified by amplifier 3. The amplified beam is further expanded and collimated by beam expander and collimator 4, then reflected by first reflector 5. The reflected beam enters compressor 6, which provides negative dispersion to compress the pulse into a transform-limited pulse. The compressed pulse is reflected by second reflector 7 to polarizing beam splitter 8. Part of the light transmitted through polarizing beam splitter 8 is used as detection light, and the reflected light is used as output light. The detection light enters frequency doubling crystal 9, which converts the fundamental frequency light into frequency-doubled light, and then enters dichroic mirror 10. Dichroic mirror 10 has high transmittance for the fundamental frequency wavelength and high reflectivity for the frequency-doubled wavelength. The reflected green light enters power meter 11 for detection, and the detected data is transmitted to feedback control module 12. It should be noted that when the pulse energy and average power remain constant, the pulse width of the femtosecond laser is inversely proportional to the peak power; that is, the narrower the pulse width, the higher the peak power. During frequency doubling, the conversion efficiency is related to the peak power density. If the spot size remains unchanged, it is directly related to the peak power or pulse width. Therefore, the pulse width can be indirectly determined by detecting the power of the green light after the femtosecond laser frequency doubling. When the power of the frequency-doubled light changes, the feedback control module 12 controls the compression module to adjust the pulse width, thereby simplifying the detection structure, reducing equipment costs, and making it easy to package in a standard industrial laser.

[0032] Furthermore, the beam expanding and collimating assembly 4 includes a first plano-concave lens 401 and a first plano-convex lens 402 arranged sequentially along the optical path. The first plano-concave lens 401 can diverge the incident light rays to expand the beam and reduce the beam density. The first plano-convex lens 402 collimates the diverged beam, effectively optimizing the beam divergence angle and improving collimation. Through the combination of the first plano-concave lens 401 and the first plano-convex lens 402, the laser beam can be expanded to avoid damage to subsequent components.

[0033] In some preferred embodiments, the compressor 6 includes a first grating 601, a second grating 602, a climbing mirror 603, and an adjustment mechanism 604. The first grating 601 is located between the first reflector 5 and the second reflector 7, and the adjustment mechanism 604 is used to adjust the spacing between the first grating 601 and the second grating 602.

[0034] Understandably, the beam, after expansion and collimation, is reflected by the first reflecting mirror 5 onto the first grating 601. The first grating 601 performs the first diffraction on the incident light, specifically causing spatial dispersion of the incident light, with different wavelength components diffracting at different angles. The dispersed beam then passes sequentially through the second grating 602 and the ascending mirror 603. The second grating 602 performs a second diffraction on the dispersed beam, forming a long, parallel beam. The ascending mirror 603 can change the propagation direction of the beam, causing the optical path to be reversed, thus reducing the size of the device. The reversed beam passes through the second grating 602 again at a specific angle. The second grating 602 performs reverse diffraction on the reversed beam, initiating spectral reconstruction. The reconstructed beam enters the first grating 601, causing different wavelength components to be spatially superimposed, achieving pulse compression. The compressed beam is output through the second reflecting mirror 7. By adjusting the distance between the first grating 601 and the second grating 602 using the adjustment mechanism 604, the total dispersion can be controlled, thereby adjusting the pulse width.

[0035] Furthermore, the adjustment mechanism 604 includes an electric displacement stage, on which the second grating 602 and the climbing mirror 603 are mounted. The electric displacement stage is used to drive the second grating 602 and the climbing mirror 603 to translate together, so that the relative positions of the second grating 602 and the climbing mirror 603 are fixed, ensuring that the beam maintains parallel incident conditions during diffraction on both sides. By setting the electric displacement stage, the displacement accuracy of the second grating 602 can be improved, thereby enabling precise adjustment of the pulse width.

[0036] Furthermore, the parameters of the first grating 601 and the second grating 602 are the same, the line count of the first grating 601 and the second grating 602 is 1600 lines / mm, the center wavelength is 1030nm, and the single-pass loss is less than 2%.

[0037] Furthermore, the climbing mirror 603 includes two third mirrors, the center wavelength of which is 1030nm and the tilt angle of which is 45°.

[0038] In some preferred embodiments, the detection module further includes a second plano-convex lens 13, which is located between the polarizing beam splitter 8 and the frequency doubling crystal 9. The second plano-convex lens 13 is used to focus the detection light onto the frequency doubling crystal 9.

[0039] Understandably, the second plano-convex lens 13 focuses the detection light output from the polarizing beam splitter 8, reducing the spot diameter and significantly increasing the power density at the frequency doubling crystal 9. This significantly improves the conversion efficiency of the frequency doubling crystal 9, thereby enhancing the detection accuracy.

[0040] Furthermore, by adjusting the distance between the second plano-convex lens 13 and the frequency doubling crystal 9, the incident angle and beam divergence angle can be adjusted to ensure uniform energy distribution in the light-receiving area of ​​the frequency doubling crystal 9.

[0041] In some preferred embodiments, a first half-wave plate 14 is disposed between the second reflecting mirror 7 and the polarizing beam splitter 8, and a second half-wave plate 15 is disposed between the polarizing beam splitter 8 and the second plano-convex lens 13. The first half-wave plate 14 is used to adjust the polarization direction of the compressed pulse, and the second half-wave plate 15 is used to adjust the polarization direction of the detection light so that it is optimally aligned with the phase matching condition of the frequency doubling crystal 9, thereby further improving the conversion efficiency of the crystal.

[0042] Furthermore, a baffle 16 is provided on one side of the dichroic mirror 10. The baffle 16 is used to block and absorb the fundamental frequency light after the dichroic mirror 10 has high transmission.

[0043] The above is a detailed description of the preferred embodiments of the present utility model. However, the present utility model is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A device for controlling the pulse width of a femtosecond laser, characterized by, include: The light source module includes a light source (1), a beam stretcher (2), an amplifier (3), and a beam expander and collimator (4) arranged sequentially along the optical path; A compression module for adjusting pulse width includes a first reflector (5), a compressor (6), and a second reflector (7), wherein the compressor (6) is used to compress the pulse into a transform-limited pulse; The detection module includes a polarizing beam splitter (8), a frequency doubling crystal (9), a dichroic mirror (10), and a power meter (11), wherein the power meter (11) is used to detect the power of the frequency doubling light; Feedback control module (12) is used to provide feedback on the power of the frequency-doubled light and control the compression module.

2. The apparatus of claim 1, wherein the pulse width control device is a femtosecond laser. The beam expanding and collimating assembly (4) includes a first plano-concave lens (401) and a first plano-convex lens (402) arranged sequentially along the optical path.

3. The apparatus of claim 1, wherein the pulse width control device is a femtosecond laser. The compressor (6) includes a first grating (601), a second grating (602), a climbing mirror (603), and an adjustment mechanism (604). The first grating (601) is located between the first reflector (5) and the second reflector (7). The adjustment mechanism (604) is used to adjust the distance between the first grating (601) and the second grating (602).

4. The apparatus of claim 3, wherein the pulse width control device is a femtosecond laser. The adjustment mechanism (604) includes an electric displacement stage, on which the second grating (602) and the climbing mirror (603) are disposed. The electric displacement stage is used to drive the second grating (602) and the climbing mirror (603) to translate together.

5. The apparatus of claim 3, wherein the pulse width control device is a femtosecond laser. The first grating (601) and the second grating (602) have the same parameters. The first grating (601) and the second grating (602) have a line count of 1600 lines / mm, a center wavelength of 1030nm, and a single pass loss of less than 2%.

6. The apparatus of claim 3, wherein the pulse width control device is a femtosecond laser. The climbing mirror (603) includes two third reflecting mirrors.

7. The apparatus of claim 1, wherein the pulse width control device is a femtosecond laser. The detection module also includes a second plano-convex lens (13), which is located between the polarizing beam splitter (8) and the frequency doubling crystal (9). The second plano-convex lens (13) is used to focus the detection light onto the frequency doubling crystal (9).

8. The apparatus of claim 1, wherein the pulse width control device is a femtosecond laser. A first half-wave plate (14) is disposed between the second reflector (7) and the polarizing beam splitter (8).

9. The apparatus of claim 7, wherein the pulse width control device is a femtosecond laser. A second half-wave plate (15) is disposed between the polarizing beam splitter (8) and the second plano-convex lens (13).

10. The apparatus of claim 1, wherein the pulse width control device is a femtosecond laser. A baffle (16) is provided on one side of the dichroic mirror (10), and the baffle (16) is used to block and absorb the fundamental frequency light after the dichroic mirror (10) has high transmission.

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