Femtosecond laser pulse compression device

Abstract

The utility model discloses a femtosecond laser pulse compression device. The femtosecond laser pulse compression device comprises an amplifier, a first half-wave plate, a compressor, a second half-wave plate, a plano-convex lens and a solid sheet group which are sequentially arranged along a light path, laser pulses output by the amplifier enter the compressor after the polarization state of the laser pulses is adjusted by the first half-wave plate, the compressor is used for pre-compensating negative dispersion, the laser pulses output by the compressor enter the plano-convex lens after the polarization state of the laser pulses is adjusted by the second half-wave plate, and the laser pulses are focused by the plano-convex lens, enter the solid sheet group, are compressed and then are output; wherein the laser pulse generates a self-phase modulation effect in the solid sheet group, and the pre-compensation negative dispersion can counteract the positive dispersion generated by the self-phase modulation effect. According to the technical scheme, a chirp mirror does not need to be arranged, the cost can be reduced, and system operation is stabilized.

Description

Technical Field

[0001] This application relates to the field of laser technology, and in particular to a femtosecond laser pulse compression device. Background Technology

[0002] Femtosecond lasers, characterized by ultrashort pulse widths and high peak power, are widely used in industrial manufacturing, scientific research, and biomedical fields. In the near-infrared band, the output pulse width of ytterbium-doped laser amplifiers typically ranges from hundreds of femtoseconds to several picoseconds. To obtain narrower pulses, the first step is spectral broadening. Currently, the most commonly used mechanism for spectral broadening is the self-phase modulation effect. When a high-peak-power pulsed light enters a nonlinear material, the ultrashort pulse undergoes self-phase modulation due to the optical Kerr effect, introducing spectral broadening. After spectral broadening, compensating for excess dispersion in the pulse using dispersive elements can compress the pulse width to near the transform limit.

[0003] However, nonlinear pulse compression techniques based on self-phase modulation heavily rely on chirped mirrors to compensate for dispersion. In the one-micron wavelength range, positive dispersion accumulates during the spectral broadening process of pulses through self-phase modulation, and positive dispersion also occurs during propagation within the material. Therefore, chirped mirrors are needed to provide negative dispersion compensation for the positive dispersion accumulated in the pulse, thereby achieving pulse compression. However, chirped mirrors are expensive and easily damaged, increasing costs and reducing the overall system stability. Utility Model Content

[0004] This application provides a femtosecond laser pulse compression device, which aims to solve the problem that existing technologies use chirped mirrors to compensate for the positive dispersion accumulated in self-phase modulation of pulses. However, chirped mirrors are expensive and easily damaged, which increases costs and reduces the stability of the entire system.

[0005] To achieve the above objectives, this application proposes a femtosecond laser pulse compression device. The femtosecond laser pulse compression device includes an amplifier, a first half-wave plate, a compressor, a second half-wave plate, a plano-convex lens, and a solid sheet assembly arranged sequentially along the optical path.

[0006] The laser pulse output from the amplifier is polarized by the first half-wave plate and then incident on the compressor. The compressor is used to pre-compensate for negative dispersion. The laser pulse output from the compressor is polarized by the second half-wave plate and then incident on the plano-convex lens. The plano-convex lens focuses the laser pulse onto the solid sheet assembly, compresses it, and then outputs it.

[0007] The laser pulse undergoes a self-phase modulation effect within the solid sheet group, and the pre-compensation negative dispersion cancels out the positive dispersion generated by the self-phase modulation effect.

[0008] In some embodiments, the compressor includes a first transmissive compression grating, a second transmissive compression grating, and a climbing mirror. A laser pulse is incident on the first transmissive compression grating, diffracted by the first transmissive compression grating, then incident on the second transmissive compression grating and diffracted by the climbing mirror. After being adjusted and reflected by the climbing mirror, the pulse is again incident on the second transmissive compression grating and diffracted by the first transmissive compression grating, and then output after being diffracted by the first transmissive compression grating.

[0009] In some embodiments, the solid sheet group includes a plurality of solid sheets arranged at Brewster angle intervals, and in the optical path, the solid sheet group adjacent to the plano-convex lens is arranged within a range of 3 to 10 cm behind the focal point of the plano-convex lens.

[0010] In some embodiments, the thickness of each solid sheet is 100 to 200 μm, and the distance between two adjacent solid sheets is 3 to 10 cm.

[0011] In some embodiments, a telescope group is further provided between the amplifier and the first half-wave plate, the telescope group including a concave lens and a convex lens arranged sequentially along the optical path;

[0012] The concave lens and the convex lens operate at wavelengths between 1000 and 1100 nm, and both have a transmittance greater than 99.9%.

[0013] In some embodiments, a plurality of reflectors arranged in the optical path are further included, wherein the plurality of reflectors include:

[0014] A first reflecting mirror is disposed between the telescope group and the first half-wave plate;

[0015] The second and third reflecting mirrors are sequentially disposed between the compressor and the second half-wave plate; and,

[0016] A fourth reflecting mirror is disposed between the second half-wave plate and the plano-convex lens;

[0017] The reflectivity of the first, second, third, and fourth reflectors is greater than 99.9%.

[0018] In some embodiments, the amplifier output pulse width is 100ps to 1ns, the output center wavelength is 1020 to 1050nm, and the output spectral width is 2 to 50nm.

[0019] In some embodiments, the operating wavelengths of the first half-wave plate and the second half-wave plate are between 1000 and 1100 nm, and the transmittance is greater than 99.9%.

[0020] In some embodiments, the plano-convex lens operates at a wavelength of 1000–1100 nm and has a transmittance greater than 99.9%.

[0021] This application proposes a femtosecond laser pulse compression device. The device includes an amplifier, a first half-wave plate, a compressor, a second half-wave plate, a plano-convex lens, and a solid-state thin-film assembly arranged sequentially along the optical path. The laser pulse output from the amplifier is polarized by the first half-wave plate and then incident on the compressor. The compressor pre-compensates for negative dispersion. The laser pulse output from the compressor is polarized by the second half-wave plate and then incident on the plano-convex lens. The plano-convex lens focuses the pulse onto the solid-state thin-film assembly, where it is compressed before being output. The laser pulse undergoes self-phase modulation within the solid-state thin-film assembly, and the pre-compensation for negative dispersion cancels out the positive dispersion generated by the self-phase modulation. This application aims to pre-compensate for negative dispersion in the amplified laser pulse by introducing a compressor, thereby canceling out the positive dispersion generated when the pulse passes through the solid-state thin-film assembly. Pulse compression is achieved based on the self-phase modulation effect of the laser pulse as it passes through the solid-state thin-film assembly. This eliminates the need for a chirped mirror, reducing costs and stabilizing system operation. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0023] Figure 1 This is a schematic diagram of the structure of a femtosecond laser pulse compression device according to an embodiment of this application. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0026] It should also be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or may have an intervening component present. When a component is referred to as "connected to" another component, it can be directly connected to the other component or may have an intervening component present.

[0027] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0028] See Figure 1 As shown, this application proposes a femtosecond laser pulse compression device. The femtosecond laser pulse compression device includes an amplifier 10, a first half-wave plate 20, a compressor 30, a second half-wave plate 40, a plano-convex lens 50, and a solid sheet group 60 arranged sequentially along the optical path.

[0029] Based on the configuration structure of the femtosecond laser pulse compression device provided in this application, a laser pulse compression process is as follows:

[0030] Amplifier 10 amplifies the energy of the input laser pulse, providing a sufficiently high energy level for the subsequent pulse compression process. Then, the first half-wave plate 20 adjusts the polarization state of the laser pulse output from amplifier 10 to ensure efficient passage through the subsequent compressor 30, which pre-compensates for negative dispersion. After passing through compressor 30, the second half-wave plate 40 again adjusts the polarization state of the laser pulse and directs it onto plano-convex lens 50. The plano-convex lens 50 focuses the compressed and polarization-adjusted laser pulse onto solid sheet group 60. Finally, the spectrum is broadened based on the nonlinear self-phase modulation effect of solid sheet group 60.

[0031] In this application, because the laser pulse is pre-compensated for negative dispersion by the compressor 30, when the laser pulse undergoes self-phase modulation effect within the solid sheet group 60, the positive dispersion generated by the self-phase modulation effect can be offset by the pre-compensated negative dispersion, thereby forming a narrower laser pulse.

[0032] Therefore, the laser pulse output after passing through the solid sheet group 60 in this application has an optimized width and higher peak power. Compared with traditional laser pulse compression schemes based on solid sheets, this application no longer requires additional chirped mirrors to compensate for the positive dispersion generated by the solid sheet, which reduces costs and stabilizes the operation of the laser pulse compression system.

[0033] Understandably, the laser pulse undergoes a stretcher before entering amplifier 10. The stretcher reduces the peak power of the laser pulse, preventing damage to the gain medium and other optical components in amplifier 10 during amplification. Positive dispersion is applied to the laser pulse within the stretcher. Therefore, after entering compressor 30, compressor 30 first compensates for the accumulated positive dispersion in the laser pulse, bringing the pulse width back to the transform limit, before pre-compensating for negative dispersion to further counteract the positive dispersion formed in the solid sheet assembly 60.

[0034] The amplifier 10 has an output pulse width of 100 ps to 1 ns, an output center wavelength of 1020 to 1050 nm, and an output spectral width of 2 to 50 nm. The first half-wave plate 20 and the second half-wave plate 40 operate at wavelengths of 1000 to 1100 nm with a transmittance greater than 99.9%. The plano-convex lens 50 operates at wavelengths of 1000 to 1100 nm with a transmittance greater than 99.9%. These parameters collectively define the optical performance of the amplifier 10, the first half-wave plate 20, the second half-wave plate 40, and the plano-convex lens 50, ensuring the efficient operation of the entire femtosecond laser pulse compression device. In practical applications, appropriate parameter combinations can be selected according to specific needs and scenarios to achieve the best laser pulse compression effect.

[0035] See Figure 1 As shown, in some embodiments, the compressor 30 includes a first transmissive compression grating 31, a second transmissive compression grating 32, and a climbing mirror 33. This compressor 30 is configured using a combination of dual transmissive compression gratings and a climbing mirror 33, which can precisely adjust the dispersion characteristics of the laser pulse and achieve pulse width compression.

[0036] Specifically, after the polarization state of the laser pulse is adjusted by the first half-wave plate 20, it is incident on the first transmission compression grating 31 at the grating blaze angle. After being diffracted by the first transmission compression grating, it is incident on the second transmission compression grating 32 and diffracted to the climbing mirror 33. The climbing mirror 33 adjusts the propagation path of the laser pulse. After the position is adjusted and reflected by the climbing mirror 33, it is incident again on the second transmission compression grating 32 and diffracted to the first transmission compression grating 31. After being diffracted by the first transmission compression grating 31, it is output.

[0037] The magnitude of the pre-compensated negative dispersion can be adjusted by regulating the vertical distance between the first transmissive compression grating 31 and the second transmissive compression grating 32. Specifically, when the vertical distance increases, the optical path difference increases, leading to more negative dispersion being introduced into the system; conversely, when the vertical distance decreases, the optical path difference decreases, and the negative dispersion effect is correspondingly weakened.

[0038] Furthermore, the parameters of the first transmissive compression grating 31 and the second transmissive compression grating 32 are set as follows: both the first transmissive compression grating 31 and the second transmissive compression grating 32 are blazed gratings. The grating line density is 1000–2000 l / mm, the grating operating wavelength is 1000–1100 nm, the grating length is 3–10 cm, and the height is 2–4 cm. These parameters are set to accommodate the precise control and processing of femtosecond lasers.

[0039] See Figure 1 As shown, in some embodiments, the solid sheet group 60 includes a plurality of solid sheets arranged at Brewster angle intervals, and the solid sheets in the solid sheet group 60 adjacent to the plano-convex lens 50 are arranged within a range of 3 to 10 cm behind the focal point of the plano-convex lens 50.

[0040] Brewster's angle is the angle of incidence at which the reflected light is fully polarized (i.e., the vibrational component perpendicular to the plane of incidence disappears completely) when light travels from one medium to another. When each solid sheet is positioned relative to the incident light or adjacent sheets at Brewster's angle, it helps to reduce unwanted reflected light, improve the transmission efficiency of the system, and achieve specific polarization state control.

[0041] Furthermore, the solid sheet adjacent to the plano-convex lens 50 in the solid sheet assembly 60 is arranged within a range of 3 to 10 cm behind the focal point of the plano-convex lens 50 to avoid damage to the solid sheet due to excessive peak power. For example, the solid sheet assembly 60 includes a first solid sheet 61, a second solid sheet 62, a third solid sheet 63, and a fourth solid sheet 64 arranged sequentially along the optical path; wherein the first solid sheet 61 is arranged within a range of 3 to 10 cm behind the focal point of the plano-convex lens 50.

[0042] The thickness of each solid sheet is between 100 and 200 μm. This thickness range is set to avoid material damage due to self-focusing while achieving sufficient spectral broadening. The distance between adjacent solid sheets is between 3 and 10 cm. This larger distance provides sufficient space to accommodate divergence while ensuring the beam still has sufficient intensity when it reaches the next sheet. Preferably, the solid sheets in this application are made of fused silica.

[0043] See Figure 1As shown, in some embodiments, the femtosecond laser pulse compression device further includes a telescope group 70 disposed between the amplifier 10 and the first half-wave plate 20. The telescope group 70 includes a concave lens 71 and a convex lens 72 arranged sequentially along the optical path. The working wavelengths of the concave lens 71 and the convex lens 72 are between 1000 and 1100 nm, and the transmittance is greater than 99.9%.

[0044] In this embodiment, the telescope assembly 70 is designed to expand and collimate the laser beam output from the amplifier 10, helping to ensure that the beam has appropriate size and divergence angle on subsequent optical elements. The concave lens 71 and the convex lens 72 both operate in the 1000–1100 nm range, a range that matches the operating wavelengths of other optical elements in the femtosecond laser pulse compression device, ensuring overall system compatibility and performance. High transmittance minimizes energy loss due to lens absorption.

[0045] See Figure 1 As shown, in some embodiments, the femtosecond laser pulse compression device further includes a plurality of mirrors for changing the optical path, including a first mirror 81, a second mirror 82, a third mirror 83, and a fourth mirror 84. The first mirror 81 is disposed between the telescope group 70 and the first half-wave plate 20; the second mirror 82 and the third mirror 83 are sequentially disposed between the compressor 30 and the second half-wave plate 40; and the fourth mirror 84 is disposed between the second half-wave plate 40 and the plano-convex lens 50; wherein the reflectivity of the first mirror 81, the second mirror 82, the third mirror 83, and the fourth mirror 84 is all greater than 99.9%.

[0046] In this embodiment, the high-reflectivity mirrors reduce energy attenuation caused by reflection losses. Furthermore, by strategically arranging the mirrors, the optical path can be flexibly altered, resulting in a more compact and efficient overall device structure. This enhances the stability and reliability of the entire femtosecond laser pulse compression device.

[0047] The above are only some or preferred embodiments of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. A femtosecond laser pulse compression device, characterized in that, It includes an amplifier, a first half-wave plate, a compressor, a second half-wave plate, a plano-convex lens, and a solid sheet assembly arranged sequentially along the optical path; The laser pulse output from the amplifier is polarized by the first half-wave plate and then incident on the compressor. The compressor is used to pre-compensate for negative dispersion. The laser pulse output from the compressor is polarized by the second half-wave plate and then incident on the plano-convex lens. The plano-convex lens focuses the laser pulse onto the solid sheet assembly, compresses it, and then outputs it. The laser pulse undergoes a self-phase modulation effect within the solid sheet group, and the pre-compensation negative dispersion cancels out the positive dispersion generated by the self-phase modulation effect.

2. The femtosecond laser pulse compression device according to claim 1, characterized in that, The compressor includes a first transmissive compression grating, a second transmissive compression grating, and a climbing mirror; The laser pulse is incident on the first transmissive compression grating, diffracted by the first transmissive compression grating, then incident on the second transmissive compression grating and diffracted to the climbing mirror. After the climbing mirror is adjusted and reflected, the pulse is incident on the second transmissive compression grating again and diffracted to the first transmissive compression grating, and then output after diffracting by the first transmissive compression grating.

3. The femtosecond laser pulse compression device according to claim 2, characterized in that, Both the first and second transmissive compression gratings are blazed gratings with a grating line density of 1000–2000 l / mm, a grating operating wavelength of 1000–1100 nm, a grating length of 3–10 cm, and a height of 2–4 cm.

4. The femtosecond laser pulse compression device according to claim 1, characterized in that, The solid sheet group includes multiple solid sheets arranged at Brewster angle intervals, and in the optical path, the solid sheet group adjacent to the plano-convex lens is arranged within a range of 3 to 10 cm behind the focal point of the plano-convex lens.

5. The femtosecond laser pulse compression device according to claim 4, characterized in that, The thickness of each solid sheet is 100-200 μm, and the distance between two adjacent solid sheets is 3-10 cm.

6. The femtosecond laser pulse compression device according to claim 1, characterized in that, It also includes a telescope group disposed between the amplifier and the first half-wave plate, the telescope group comprising a concave lens and a convex lens arranged sequentially along the optical path; The concave lens and the convex lens operate at wavelengths between 1000 and 1100 nm, and both have a transmittance greater than 99.9%.

7. The femtosecond laser pulse compression device according to claim 6, characterized in that, It also includes a plurality of reflectors arranged in the optical path, wherein the plurality of reflectors include: A first reflecting mirror is disposed between the telescope group and the first half-wave plate; The second and third reflecting mirrors are disposed between the compressor and the second half-wave plate; and, A fourth reflecting mirror is disposed between the second half-wave plate and the plano-convex lens; The reflectivity of the first, second, third, and fourth reflectors is greater than 99.9%.

8. The femtosecond laser pulse compression device according to claim 1, characterized in that, The amplifier outputs a pulse width of 100ps to 1ns, an output center wavelength of 1020 to 1050nm, and an output spectral width of 2 to 50nm.

9. The femtosecond laser pulse compression device according to claim 1, characterized in that, The first half-wave plate and the second half-wave plate operate at wavelengths of 1000–1100 nm and have a transmittance greater than 99.9%.

10. The femtosecond laser pulse compression device according to claim 1, characterized in that, The working wavelength of the plano-convex lens is 1000-1100nm, and the transmittance is greater than 99.9%.

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