Four-way femtosecond laser compressor and method

Abstract

According to the four-way femtosecond laser compressor and the method, light output through the compressor for the first time is injected into the compressor for multiple times, incident chirped pulses enter and exit for four times along the light path of the compressor, the incident chirped pulses pass through a transmission grating for eight times in total, and finally the incident chirped pulses are output through an output reflector to complete compression output; the number of times that a light beam passes through the grating is increased to 16, so that the dispersion amount of a compressor with the same grating caliber and grating spacing is increased by 4 times, and the chirped pulse amplifier with larger spreading amount or larger bandwidth is adapted; according to the femtosecond laser, the use frequency of the compression grating is expanded repeatedly, and a larger compression amount is obtained under the condition that the space between the compression grating is not changed, so that the larger broadening amount of the chirped pulse amplifier can be compatible, the problem of design limitation of the chirped pulse amplifier is solved, and the output monopulse energy of the femtosecond laser is improved.

Description

Technical Field

[0001] The present invention relates to a four-pass femtosecond laser compressor and a method thereof. Background Art

[0002] After a femtosecond laser is generated, it is usually connected to a laser amplifier to amplify the laser's power and energy. However, due to the high peak power of the amplified femtosecond laser pulse, it can easily damage the amplifier components. The current mainstream method to avoid laser amplification damage is to use chirped pulse amplification technology, which first broadens the femtosecond laser into a picosecond or nanosecond laser, then amplifies it, and finally compresses the picosecond or nanosecond laser into a femtosecond laser. Therefore, in high-energy laser amplification systems, the design of the compressor is crucial.

[0003] The dispersion compensation element commonly used in the compressor part of chirped pulse amplification technology is a transmission grating. Its advantages are high efficiency and compatibility with large energy. However, its disadvantage is that the greater the amount of dispersion that needs to be compensated, the larger the size of the grating required. Currently, the maximum length of mature transmission gratings is about 150mm, which limits the broadening amount and final output energy of the chirped pulse amplifier. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a four-pass femtosecond laser compressor and method, aiming to solve the problem that the compression amount of the compressor in the chirped pulse amplifier is limited by the grating size.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A four-pass femtosecond laser compressor, characterized by comprising: a transmission grating, a mirror assembly, a first mirror, a beam reducing mirror, an output mirror, and a second mirror;

[0007] In the first incident light path, the incident chirped pulse connects to area 1 of the transmission grating, area 1 of the transmission grating connects to the reflector group, the reflector group connects to area 2 of the transmission grating, and area 2 of the transmission grating connects to reflector 1;

[0008] In the first reflection light path, the reflector 1 is connected to the area 2 of the transmission grating, the area 2 of the transmission grating is connected to the reflector group, the reflector group is connected to the area 1 of the transmission grating, and the area 1 of the transmission grating is connected to the reflector 2;

[0009] In the second incident light path, reflector 2 is connected to area 1 of the transmission grating, area 1 of the transmission grating is connected to the reflector group, the reflector group is connected to area 2 of the transmission grating, and area 2 of the transmission grating is connected to reflector 1;

[0010] In the second reflection light path, the reflector 1 is connected to the area 2 of the transmission grating, the area 2 of the transmission grating is connected to the reflector group, the reflector group is connected to the area 1 of the transmission grating, and the area 1 of the transmission grating is connected to the beam reduction reflector;

[0011] In the third incident light path, the beam reduction mirror is connected to area 3 of the transmission grating, area 3 of the transmission grating is connected to the reflector group, the reflector group is connected to area 4 of the transmission grating, and area 4 of the transmission grating is connected to reflector 1;

[0012] In the third reflection light path, the reflector 1 is connected to the area 4 of the transmission grating, the area 4 of the transmission grating is connected to the reflector group, the reflector group is connected to the area 3 of the transmission grating, and the area 3 of the transmission grating is connected to the reflector 2;

[0013] In the fourth incident light path, reflector 2 is connected to area 3 of the transmission grating, area 3 of the transmission grating is connected to the reflector group, the reflector group is connected to area 4 of the transmission grating, and area 4 of the transmission grating is connected to reflector 1;

[0014] In the fourth reflection light path, reflector one is connected to area four of the transmission grating, area four of the transmission grating is connected to the reflector group, the reflector group is connected to area three of the transmission grating, area three of the transmission grating is connected to the output reflector, and the compressed output pulse is behind the output reflector.

[0015] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the incident chirped pulse is a chirped pulse with a central wavelength of 1030nm, 1064nm, and 1342nm, an output power of 0 to 1000W, and a pulse width of 100fs to 100ns.

[0016] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the transmission grating is a transmission grating having an operating wavelength in the 1030nm, 1064nm, and 1342nm bands and a grating line density of 1 / mm to 10000 / mm.

[0017] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the reflector group is two broadband reflectors arranged orthogonally, and the operating wavelength is the output wavelength of the infrared laser.

[0018] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the center distance between the two lenses of the reflector group is 1mm to 200mm, and the distance between the reflector group and the transmission grating is 0 to 2000mm.

[0019] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the first reflector is a broadband reflector, and the operating wavelength is the output wavelength of the infrared laser.

[0020] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the beam lowering mirror is two mirrors arranged orthogonally, which increase or decrease the height of the beam to 0 mm to 200 mm.

[0021] Furthermore, in the above-mentioned four-pass femtosecond laser compressor, the center distance between the two lenses of the beam reducing reflector is 1mm to 200mm, and the distance between the beam reducing reflector and the transmission grating is 0 to 200mm.

[0022] The four-pass femtosecond laser compression method of the present invention comprises the following steps: in the first incident light path, the incident chirped pulse is incident as parallel light. After passing through region 1 of the transmission grating, light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. The divergent light is reflected parallel to region 2 of the transmission grating by a reflector group. After passing through region 2 of the transmission grating, the divergent light is incident parallel to reflector 1. Reflector 1 reflects the light beam slightly deviating from the incident light. After passing through region 2 of the transmission grating, the light beam is contracted perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group reflects the contracted light parallel to region 1 of the transmission grating. The contracted light beam that has passed through region 1 of the transmission grating becomes parallel light, completing one compression step;

[0023] The output light after the first compression is incident on the second reflector, which reflects the light beam to the area 1 of the transmission grating, starting the second compression. After the light beam passes through the area 1 of the transmission grating, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. The divergent light is reflected parallel to the area 2 of the transmission grating by the reflector group. After passing through the area 2 of the transmission grating, the divergent light is incident parallel to the first reflector. The first reflector reflects the light beam slightly deviating from the incident light. After passing through the area 2 of the transmission grating, the light beam is contracted perpendicular to the grating lines on a macro scale due to diffraction. The reflector group reflects the contracted light parallel to the area 1 of the transmission grating. The contracted light beam that passes through the area 1 of the transmission grating becomes parallel light, completing the second compression.

[0024] The output light after the secondary compression is incident on the beam-reducing reflector. The beam-reducing reflector reduces the height of the beam and reflects the reduced beam to area three of the transmission grating at an angle parallel to the secondary compressed output light for a second compression. After the light beam passes through area three of the transmission grating, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. The divergent light is reflected parallel to area four of the transmission grating by the reflector group. After passing through area four of the transmission grating, the divergent light is incident parallel to reflector one. Reflector one reflects the light beam slightly away from the incident light. After passing through area four of the transmission grating, the light beam will be contracted perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group reflects the contracted light parallel to area three of the transmission grating. The contracted light beam that passes through area three of the transmission grating becomes parallel light, completing the third compression.

[0025] The output light after the three compressions is incident on the second reflector, which reflects the light beam to the third area of ​​the transmission grating for the second compression. After the light beam passes through the third area of ​​the transmission grating, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. The divergent light is reflected in parallel by the reflector group to the fourth area of ​​the transmission grating. After passing through the fourth area of ​​the transmission grating, the divergent light is incident on the first reflector in parallel. The first reflector reflects the light beam slightly deviating from the incident light. After passing through the fourth area of ​​the transmission grating, the light beam is contracted perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group reflects the contracted light in parallel back to the fourth area of ​​the transmission grating. The contracted light beam that passes through the fourth area of ​​the transmission grating becomes parallel light, completing the fourth compression.

[0026] The fourth compressed output beam is located directly below the incident chirped pulse beam, and the two are in opposite directions. They are reflected by the output reflector to become a compressed output pulse, completing the compression.

[0027] Compared with the prior art, the present invention has significant advantages and beneficial effects, which are specifically reflected in the following aspects:

[0028] The present invention injects the light outputted by the compressor for the first time into the compressor multiple times. The incident chirped pulse is incident and emitted four times along the optical path of the compressor, passes through the transmission grating eight times in total, and is finally outputted through the output reflector to complete the compressed output. This is repeated multiple times to extend the number of times the compression grating is used. A greater compression amount is obtained while the compressor grating spacing remains unchanged, thereby being compatible with a greater broadening amount of the chirped pulse amplifier. This solves the design limitations of the chirped pulse amplifier and increases the output single pulse energy of the femtosecond laser.

[0029] By increasing the number of times the light beam passes through the grating to 16, the dispersion of the compressor with the same grating aperture and grating spacing is quadrupled, thereby accommodating chirped pulse amplifiers with larger broadening or larger bandwidth.

[0030] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the specific embodiments of the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 : Schematic diagram of the structure of the four-pass femtosecond laser compressor of the present invention;

[0033] Figure 2 : Schematic diagram of the side-view partition of the transmission grating. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of the present invention, directional terms and order terms are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0036] In chirped pulse amplification, the stretching and compression of pulses must be matched. Conventional single-grating compressors, in which the beam passes through the grating four times, provide a fixed amount of compression dispersion when the grating spacing is fixed. The present invention increases the number of beam passes through the grating to 16, quadrupling the dispersion of the compressor with the same grating aperture and spacing. This allows for chirped pulse amplifiers with greater stretching or bandwidth.

[0037] like Figure 1 、 Figure 2 As shown, a four-pass femtosecond laser compressor includes a transmission grating 2, a reflector group 3, a reflector 1 4, a beam reducing reflector 5, an output reflector 6, and a reflector 2 8;

[0038] The transmission grating 2 includes region 1 21, region 22, region 3 23, and region 4 24. Region 1 21 is the position where the incident chirped pulse first enters the transmission grating. Region 2 22 is another position on the grating at the same horizontal height as region 1 21. The distance between region 22 and region 1 21 is 1 to 200 mm. Region 3 23 is another position on the grating at the same vertical height as region 1 21. The distance between region 3 23 and region 1 21 is 1 to 200 mm. Region 4 24 is a position on the grating at the same vertical height as region 22 and the same horizontal height as region 3 23.

[0039] In the first incident light path, the incident chirped pulse 1 connects to area 1 21 of the transmission grating 2, area 1 21 of the transmission grating 2 connects to the reflector group 3, the reflector group 3 connects to area 22 of the transmission grating 2, and area 22 of the transmission grating 2 connects to the reflector 1 4;

[0040] In the first reflection light path, the reflector 1 4 is connected to the area 2 22 of the transmission grating 2, the area 22 of the transmission grating 2 is connected to the reflector group 3, the reflector group 3 is connected to the area 1 21 of the transmission grating 2, and the area 1 21 of the transmission grating 2 is connected to the reflector 2 8;

[0041] In the second incident light path, the second reflector 8 is connected to the area 1 21 of the transmission grating 2, the area 1 21 of the transmission grating 2 is connected to the reflector group 3, the reflector group 3 is connected to the area 22 of the transmission grating 2, and the area 22 of the transmission grating 2 is connected to the reflector 1 4;

[0042] In the second reflection light path, the reflector 1 4 is connected to the area 2 22 of the transmission grating 2, the area 2 22 of the transmission grating 2 is connected to the reflector group 3, the reflector group 3 is connected to the area 1 21 of the transmission grating 2, and the area 1 21 of the transmission grating 2 is connected to the beam reducing reflector 5;

[0043] In the third incident light path, the light beam is reduced to reflector 5 and connected to area 3 23 of transmission grating 2, area 3 23 of transmission grating 2 is connected to reflector group 3, reflector group 3 is connected to area 4 24 of transmission grating 2, and area 4 24 of transmission grating 2 is connected to reflector 1 4;

[0044] In the third reflection light path, the reflector 1 4 is connected to the area 4 24 of the transmission grating 2, the area 4 24 of the transmission grating 2 is connected to the reflector group 3, the reflector group 3 is connected to the area 3 23 of the transmission grating 2, and the area 3 23 of the transmission grating 2 is connected to the reflector 2 8;

[0045] In the fourth incident light path, the second reflector 8 is connected to the third area 23 of the transmission grating 2, the third area 23 of the transmission grating 2 is connected to the reflector group 3, the reflector group 3 is connected to the fourth area 24 of the transmission grating 2, and the fourth area 24 of the transmission grating 2 is connected to the first reflector 4;

[0046] In the fourth reflection light path, the reflector 1 4 is connected to the area 4 24 of the transmission grating 2, the area 4 24 of the transmission grating 2 is connected to the reflector group 3, the reflector group 3 is connected to the area 3 23 of the transmission grating 2, and the area 3 23 of the transmission grating 2 is connected to the output reflector 6. After the output reflector 6 is the compressed output pulse 7.

[0047] Incident chirped pulse 1 is a chirped pulse with a central wavelength of 1030 nm, 1064 nm, and 1342 nm, an output power of 0 to 1000 W, and a pulse width of 100 fs to 100 ns. The incident chirped pulse is generated by a femtosecond seed source after passing through a fiber stretcher.

[0048] The transmission grating 2 is a transmission grating having an operating wavelength in the 1030 nm, 1064 nm, and 1342 nm bands and a grating line density of 1 / mm to 10000 / mm.

[0049] The reflector group 3 is composed of two orthogonally arranged broadband reflectors, whose operating wavelength is the output wavelength of the infrared laser. The center distance between the two lenses of the reflector group 3 is 1mm to 200mm, and the distance between the reflector group 3 and the transmission grating 2 is 0 to 2000mm.

[0050] Reflector 1 4 is a broadband reflector, and its working wavelength is the output wavelength of the infrared laser.

[0051] The beam-reducing reflectors 5 consist of two mirrors arranged orthogonally, increasing or decreasing the beam height by 0 mm to 200 mm. The center-to-center distance between the two lenses of the beam-reducing reflectors 5 is 1 mm to 200 mm, and the distance between the beam-reducing reflectors 5 and the transmission grating 2 is 0 to 200 mm. The beam-reducing reflectors 5 can be replaced with a reflector if the output performance allows.

[0052] In a four-pass femtosecond laser compression method, in the first incident optical path, the incident chirped pulse 1 is incident as parallel light. After passing through area 121 of the transmission grating 2, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. The divergent light is reflected parallel to area 22 of the transmission grating 2 by the reflector group 3. After passing through area 22 of the transmission grating 2, the divergent light is incident parallel to the reflector 14. The reflector 14 reflects the light beam slightly deviating from the incident light. After passing through area 22 of the transmission grating 2, the light beam is contracted perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group 3 reflects the contracted light parallel to area 21 of the transmission grating 2. The contracted light beam passing through area 21 of the transmission grating 2 becomes parallel light, completing one compression.

[0053] The output light after the first compression is incident on the second reflector 8, which reflects the light beam to the area 1 21 of the transmission grating 2, and the second compression begins. After the light beam passes through the area 1 21 of the transmission grating 2, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. The divergent light is reflected in parallel by the reflector group 3 to the area 2 22 of the transmission grating 2. The divergent light passes through the area 2 22 of the transmission grating 2 and is incident on the reflector 1 4 in a parallel manner. The reflector 1 4 reflects the light beam slightly deviating from the incident light. After passing through the area 2 22 of the transmission grating 2, the light beam is contracted perpendicular to the grating lines on a macro scale due to diffraction. The reflector group 3 reflects the contracted light in parallel back to the area 1 21 of the transmission grating 2. The contracted light beam that has passed through the area 1 21 of the transmission grating 2 becomes parallel light, completing the second compression.

[0054] The output light after the secondary compression is incident on the beam-lowering reflector 5. The beam-lowering reflector 5 reduces the height of the beam and reflects the lowered beam to the area 3 23 of the transmission grating 2 at an angle parallel to the secondary compressed output light, performing a second compression. After the light beam passes through the area 3 23 of the transmission grating 2, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. The divergent light is reflected parallel to the area 4 24 of the transmission grating 2 by the reflector group 3. After passing through the area 4 24 of the transmission grating 2, the divergent light is incident parallel to the reflector 1 4. The reflector 1 4 reflects the light beam slightly deviating from the incident light. After passing through the area 4 24 of the transmission grating 2, the light beam will be contracted macroscopically perpendicular to the grating lines due to diffraction. The reflector group 3 reflects the contracted light parallel to the area 3 23 of the transmission grating 2. The contracted light beam that has passed through the area 3 23 of the transmission grating 2 becomes parallel light, completing the third compression.

[0055] The output light after the three compressions is incident on the second reflector 8, which reflects the light beam to the third area 23 of the transmission grating 2 for a second compression. After the light beam passes through the third area 23 of the transmission grating 2, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. The reflector group 3 reflects the divergent light in parallel to the fourth area 24 of the transmission grating 2. After passing through the fourth area 24 of the transmission grating 2, the divergent light is incident on the first reflector 4 in parallel. The first reflector 4 reflects the light beam slightly deviating from the incident light. After passing through the fourth area 24 of the transmission grating 2, the light beam is macroscopically contracted perpendicular to the grating lines due to diffraction. The reflector group 3 reflects the contracted light in parallel back to the fourth area 24 of the transmission grating 2. The contracted light beam that passes through the fourth area 24 of the transmission grating 2 becomes parallel light, completing the fourth compression.

[0056] The fourth compressed output beam is located directly below the incident chirped pulse 1 beam, and the two are in opposite directions. It is reflected by the output reflector 6 to become the compressed output pulse 7, completing the compression.

[0057] Example

[0058] The incident chirped pulse 1 has a central wavelength of 1030 nm and a spectral width of 1.8 nm at 3 dB and 6 nm at 10 dB. Before amplification, the 196 fs pulse is stretched to 1.5 ns by a stretcher. Transmission grating 2 measures 100 mm × 30 mm × 6.35 mm, with a grating line density of 1739 / mm. The center-to-center spacing between the two lenses of beam-reducing mirror 5 is 15 mm, and the distance between beam-reducing mirror 5 and the transmission grating is 200 mm. The center-to-center spacing between the two lenses of reflector assembly 3 is 20 mm, and the grating pitch is 200 mm.The incident chirped pulse 1 is incident as parallel light. After passing through the transmission grating 2, the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. The divergent light is then reflected parallel to other positions of the transmission grating 2 by the reflector group 3. After passing through the transmission grating 2, the divergent light is incident parallel to the reflector 1 4. The reflector 1 4 reflects the light beam slightly deviating from the incident light. After passing through the transmission grating 2, the light beam is macroscopically contracted perpendicular to the grating lines due to diffraction. The reflector group 3 reflects the contracted light parallel to the transmission grating 2. The contracted light beam passing through the transmission grating 2 becomes parallel light and completes a compression. The light after the first compression is incident on the reflector 2 8. The reflector 2 8 reflects the light beam slightly deviating from the incident light to the transmission grating 2, starting the second After the second compression, the light beam passes through the transmission grating 2, and the diffraction angles of light with different frequency components are different in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. Then, the divergent light is reflected parallel to the transmission grating 2 by the reflector group 3. After passing through the transmission grating 2, the divergent light is incident parallel to the reflector 1 4. The reflector 1 4 reflects the light beam slightly deviating from the incident light. After passing through the transmission grating 2, the light beam is macroscopically contracted perpendicular to the grating lines due to diffraction. The reflector group 3 reflects the contracted light parallel to the transmission grating 2. The contracted light beam passing through the transmission grating 2 becomes parallel light and completes the second compression; the light after the second compression is incident on the beam lowering reflector 5. The beam lowering reflector 5 reduces the height of the light beam while reducing the angle of the light beam at a parallel angle to the output light of the second compression. The light beam after passing through the transmission grating 2 is reflected by the transmission grating 2, and the third compression begins. After the light beam passes through the transmission grating 2, the diffraction angles of light of different frequency components are different in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. Then, it passes through the reflector group 3 to reflect the divergent light in parallel to the transmission grating 2. After passing through the transmission grating 2, the divergent light is incident on the reflector 1 4 in parallel. The reflector 4 reflects the light beam slightly deviating from the incident light. After passing through the transmission grating 2, the light beam is macroscopically contracted perpendicular to the grating lines due to diffraction. The reflector group 3 reflects the contracted light in parallel back to the transmission grating 2. The contracted light beam after passing through the transmission grating 2 becomes parallel light and completes the third compression. The light after the third compression is incident on the reflector 2 8, and the reflector 2 8 reflects the light beam slightly deviating from the incident light to the transmission grating 2 , the fourth compression begins. After the light beam passes through the transmission grating 2, the diffraction angles of light with different frequency components are different in space, causing the light beam to diverge perpendicular to the grating lines on a macro scale. Then, it passes through the reflector group 3 and reflects the divergent light in parallel to the transmission grating 2. After passing through the transmission grating 2, the divergent light is incident on the reflector 1 4 in parallel. The reflector 1 4 reflects the light beam slightly deviating from the incident light. After passing through the transmission grating 2, the light beam is macroscopically contracted perpendicular to the grating lines due to diffraction. The reflector group 3 reflects the contracted light in parallel back to the transmission grating 2. The contracted light beam passing through the transmission grating 2 becomes parallel light and completes the fourth compression. The light beam output by the fourth compression is located directly below the incident chirped pulse 1 beam, and is reflected by the output reflector 6 to become the compressed output pulse 7, completing the compression.The narrowest compression pulse of the measured output is less than 500 fs, and the compression efficiency is 77%.

[0059] In summary, the present invention re-injects the light output by the compressor for the first time into the compressor, repeatedly, and expands the number of times the compression grating is used. This allows for a greater compression amount while keeping the compressor grating spacing unchanged, thereby being compatible with a larger broadening amount of the chirped pulse amplifier, solving the design limitations of the chirped pulse amplifier and increasing the single pulse energy output by the femtosecond laser.

[0060] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, improvements, and the like made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention. It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it need not be further defined or explained in subsequent figures.

[0061] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0062] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

Claims

1. Four-pass femtosecond laser compressor, characterized by: It comprises a transmission grating (2), a reflector group (3), a reflector 1 (4), a beam reducing reflector (5), an output reflector (6) and a reflector 2 (8); In the first incident light path, the incident chirped pulse (1) is connected to the first region (21) of the transmission grating (2), the first region (21) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the second region (22) of the transmission grating (2), and the second region (22) of the transmission grating (2) is connected to the first reflector (4); In the first reflection light path, the reflector 1 (4) is connected to the area 2 (22) of the transmission grating (2), the area 2 (22) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the area 1 (21) of the transmission grating (2), and the area 1 (21) of the transmission grating (2) is connected to the reflector 2 (8); In the second incident light path, the second reflector (8) is connected to the first area (21) of the transmission grating (2), the first area (21) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the second area (22) of the transmission grating (2), and the second area (22) of the transmission grating (2) is connected to the first reflector (4); In the second reflection light path, the reflector 1 (4) is connected to the area 2 (22) of the transmission grating (2), the area 2 (22) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the area 1 (21) of the transmission grating (2), and the area 1 (21) of the transmission grating (2) is connected to the light beam lowering reflector (5); In the third incident light path, the light beam is lowered to the reflector (5) and connected to the area three (23) of the transmission grating (2), the area three (23) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the area four (24) of the transmission grating (2), and the area four (24) of the transmission grating (2) is connected to the reflector one (4); In the third reflection light path, the reflector 1 (4) is connected to the area 4 (24) of the transmission grating (2), the area 4 (24) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the area 3 (23) of the transmission grating (2), and the area 3 (23) of the transmission grating (2) is connected to the reflector 2 (8); In the fourth incident light path, the second reflector (8) is connected to the third area (23) of the transmission grating (2), the third area (23) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the fourth area (24) of the transmission grating (2), and the fourth area (24) of the transmission grating (2) is connected to the first reflector (4); In the fourth reflection light path, the reflector 1 (4) is connected to the area 4 (24) of the transmission grating (2), the area 4 (24) of the transmission grating (2) is connected to the reflector group (3), the reflector group (3) is connected to the area 3 (23) of the transmission grating (2), and the area 3 (23) of the transmission grating (2) is connected to the output reflector (6).

2. The four-pass femtosecond laser compressor according to claim 1, characterized in that: The incident chirped pulse (1) is a chirped pulse with a central wavelength of 1030 nm, 1064 nm, and 1342 nm, an output power of 0 to 1000 W, and a pulse width of 100 fs to 100 ns.

3. The four-pass femtosecond laser compressor according to claim 1, characterized in that: The transmission grating (2) is a transmission grating with an operating wavelength in the 1030nm, 1064nm and 1342nm bands and a grating line density of 1 / mm to 10000 / mm.

4. The four-pass femtosecond laser compressor according to claim 1, characterized in that: The reflector group (3) is two broadband reflectors arranged orthogonally, and the operating wavelength is the output wavelength of the infrared laser.

5. The four-pass femtosecond laser compressor according to claim 1 or 4, characterized in that: The center distance between the two lenses of the reflector group (3) is 1 mm to 200 mm, and the distance between the reflector group (3) and the transmission grating (2) is 0 to 2000 mm.

6. The four-pass femtosecond laser compressor according to claim 1, characterized in that: Reflector 1 (4) is a broadband reflector, and its working wavelength is the output wavelength of the infrared laser.

7. The four-pass femtosecond laser compressor according to claim 1, characterized in that: The light beam lowering reflectors (5) are two reflectors arranged orthogonally, and increase or decrease the height of the light beam to 0 mm to 200 mm.

8. The four-pass femtosecond laser compressor according to claim 1 or 7, characterized in that: The center distance between the two lenses of the beam reducing reflector (5) is 1mm to 200mm, and the distance between the beam reducing reflector (5) and the transmission grating (2) is 0 to 200mm.

9. A four-pass femtosecond laser compression method, characterized in that: In the first incident light path, the incident chirped pulse (1) is incident as parallel light. After passing through the area one (21) of the transmission grating (2), the light of different frequency components has different diffraction angles in space, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. After passing through the reflector group (3), the divergent light is reflected parallel to the area two (22) of the transmission grating (2). After passing through the area two (22) of the transmission grating (2), the divergent light is incident parallel to the reflector one (4). The reflector one (4) reflects the light beam slightly deviating from the incident light. After passing through the area two (22) of the transmission grating (2), the light beam is contracted perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group (3) reflects the contracted light parallel to the area one (21) of the transmission grating (2). The contracted light beam passing through the area one (21) of the transmission grating (2) becomes parallel light, completing one compression. The output light after the first compression is incident on the second reflector (8), and the second reflector (8) reflects the light beam to the area one (21) of the transmission grating (2), and the second compression begins. After the light beam passes through the area one (21) of the transmission grating (2), the diffraction angles of light of different frequency components in space are different, causing the light beam to diverge perpendicular to the grating lines on a macroscopic scale. After passing through the reflector group (3), the divergent light is reflected parallel to the area two (22) of the transmission grating (2). After passing through the area two (22) of the transmission grating (2), the divergent light is incident parallel to the first reflector (4). The first reflector (4) reflects the light beam slightly deviating from the incident light. After passing through the area two (22) of the transmission grating (2), the light beam is contracted perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group (3) reflects the contracted light parallel to the area one (21) of the transmission grating (2). The contracted light beam passing through the area one (21) of the transmission grating (2) becomes parallel light, and the second compression is completed. The output light after secondary compression is incident on the beam reducing reflector (5). The beam reducing reflector (5) reduces the height of the beam and reflects the reduced beam to the third area (23) of the transmission grating (2) at an angle parallel to the secondary compressed output light for secondary compression. After the beam passes through the third area (23) of the transmission grating (2), the diffraction angles of light with different frequency components are different in space, causing the beam to diverge perpendicular to the grating lines on a macroscopic scale. The divergent light is reflected parallel to the transmission grating by the reflector group (3). The divergent light passes through the area four (24) of the transmission grating (2) and is incident on the reflector one (4) in parallel. The reflector one (4) reflects the light beam slightly deviating from the incident light. After the light beam passes through the area four (24) of the transmission grating (2), it will shrink perpendicular to the grating lines on a macroscopic scale due to diffraction. The reflector group (3) reflects the shrinking light in parallel back to the area three (23) of the transmission grating (2). The shrinking light beam passing through the area three (23) of the transmission grating (2) becomes parallel light, completing the third compression. The output light after the three compressions is incident on the second reflector (8), and the second reflector (8) reflects the light beam to the third area (23) of the transmission grating (2) for the second compression. After the light beam passes through the third area (23) of the transmission grating (2), the diffraction angles of light of different frequency components in space are different, causing the light beam to diverge perpendicular to the grating lines on a macroscopic level. After passing through the reflector group (3), the divergent light is reflected parallel to the fourth area (24) of the transmission grating (2). After passing through the fourth area (24) of the transmission grating (2), the divergent light is incident parallel to the first reflector (4). The first reflector (4) reflects the light beam slightly deviating from the incident light. After passing through the fourth area (24) of the transmission grating (2), the light beam is contracted perpendicular to the grating lines on a macroscopic level due to diffraction. The reflector group (3) reflects the contracted light parallel to the fourth area (24) of the transmission grating (2). The contracted light beam passing through the fourth area (24) of the transmission grating (2) becomes parallel light, completing the fourth compression. The fourth compressed output light beam is located directly below the incident chirped pulse (1) light beam, and the two light beams are in opposite directions. The light beam is reflected by the output reflector (6) and becomes a compressed output pulse (7).

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