Femtosecond laser pulse time shaping system and method

Abstract

The invention discloses a femtosecond laser pulse time shaping system. The system comprises a laser, and a polarization assembly, a polarization beam splitter, a 1 / 4 wave plate and a first semi-transparent and semi-reflective mirror which are sequentially arranged along the laser direction of the laser, the polarization assembly is used for converting the initial femtosecond laser pulse generated by the laser into linearly polarized light; the polarization beam splitter is used for highly transmitting the linearly polarized light entering the polarization beam splitter and highly reflecting the linearly polarized light perpendicular to the vibration direction of the incident linearly polarized light; the polarization beam splitter, the 1 / 4 wave plate and the first half-transparent and half-reflecting mirror form a time shaping device which is used for performing time shaping on femtosecond laser; the initial femtosecond laser pulse is subjected to polarization modulation of the polarization assembly and time shaping processing of the time shaping device, and finally a double-pulse sequence is output. The time shaping system is easy to construct and has a high damage threshold value, high-power processing and light path limitation of the time shaping system can be solved, and the time shaping system has important significance in the field of femtosecond laser application.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to a femtosecond laser pulse time shaping system and method. Background Art

[0002] Femtosecond laser technology is a highly precise laser processing technology that uses ultrashort pulse lasers at the femtosecond level to process and shape materials. Compared with traditional laser processing technology, femtosecond lasers have unique characteristics, such as high peak power, ultrafast time scale, nonlinear optical effects, etc. These characteristics make femtosecond lasers show great potential in micro-nano processing, biomedical applications, optical device manufacturing and other fields. With the widespread application of laser pulses in various fields, the demand for pulse shaping technology is becoming more and more urgent.

[0003] Femtosecond laser pulse trains divide a single laser pulse into several sub-pulses with shapes similar to the source pulse, and the delay and energy ratio between the sub-pulses can be adjusted arbitrarily. Since the delay between sub-pulses is in the order of fs-ps, which is less than the electron-lattice coupling time, it can be re-excited before the electron recombination, thereby regulating the local instantaneous electronic dynamics of the material, achieving the regulation of the instantaneous local characteristics of the material, and then regulating the time window of laser absorption, greatly improving the processing efficiency and processing accuracy of femtosecond lasers. At present, there are many ways to form femtosecond laser pulse trains. These include the use of commercial 4f systems, birefringent crystals, and pulse train generation systems based on Michelson interferometers. However, these time shaping systems all have some limitations. For example, the 4f system contains a liquid crystal spatial light modulator. Due to the limited phase adjustment range of the liquid crystal element, it is impossible to generate a pulse sequence with a large pulse delay. At the same time, the damage threshold of the liquid crystal element is low, which limits its use under high-power conditions. Birefringent crystals are highly dependent on the polarization state. The polarizations of the sub-pulses usually generated are perpendicular to each other and difficult to adjust, and they are prone to dispersion effects. Therefore, they are usually suitable for special occasions. The pulse sequence generation system based on the Michelson interferometer has difficulty in adjusting the optical axis coincidence of the sub-pulses generated, and uses more optical elements and occupies a larger space, which is not conducive to industrialization. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a femtosecond laser pulse time shaping system and method.

[0005] The invention discloses a femtosecond laser pulse time shaping system, comprising: a laser and a polarization component, a polarization beam splitter, a quarter wave plate and a first semi-transparent semi-reflective mirror arranged in sequence along the laser direction of the laser;

[0006] The polarization component is used to convert the initial femtosecond laser pulse generated by the laser into linearly polarized light;

[0007] The polarization beam splitter is used to have high transmittance for linear polarized light incident to the polarization beam splitter and high reflection for linear polarized light perpendicular to the vibration direction of the incident linear polarized light;

[0008] The polarization beam splitter, the quarter wave plate and the first semi-transparent and semi-reflective mirror constitute a time shaping device for performing time shaping on the femtosecond laser;

[0009] The initial femtosecond laser pulse is subjected to polarization modulation by the polarization component and time shaping processing by the time shaping device, and finally outputs a double pulse sequence.

[0010] As a further improvement of the present invention, the polarization component includes a 1 / 2 wave plate and a polarization beam splitter prism which are sequentially arranged along the laser direction of the laser.

[0011] As a further improvement of the present invention, the polarization component includes a polarizer arranged along the laser direction of the laser.

[0012] As a further improvement of the present invention,

[0013] The time delay between the two pulses is Δt:

[0014] Δt=2×(ΔL1+d×n d +ΔL2) / c

[0015] Where ΔL1 is the distance between the 1 / 4 wave plate and the polarization beam splitter, d is the thickness of the 1 / 4 wave plate, and n is d is the refractive index of the quarter wave plate material, ΔL2 is the distance between the first semi-transparent and semi-reflective mirror and the quarter wave plate, and c is the speed of light;

[0016] The energy ratio between the double pulses is 1:R, where R is the reflectivity of the first semi-transparent and semi-reflective mirror.

[0017] As a further improvement of the present invention, it also includes: an external threaded sleeve and an internal threaded sleeve that are threadedly connected;

[0018] The polarization beam splitter and the quarter wave plate are fixedly installed in the internal threaded sleeve by a retaining ring, and the first semi-transparent and semi-reflective mirror is fixed in the external threaded sleeve. The pulse spacing is adjusted by rotating the external threaded sleeve and / or the internal threaded sleeve to change the interval between the first semi-transparent and semi-reflective mirror and the quarter wave plate.

[0019] The present invention also discloses a femtosecond laser pulse time shaping method based on the femtosecond laser pulse time shaping system, comprising:

[0020] Step 11, the initial femtosecond laser pulse generated by the laser becomes linearly polarized light after passing through a polarization component;

[0021] Step 12, after the linear polarized light passes through the polarization beam splitter, it is converted into right-handed circularly polarized light or left-handed circularly polarized light through a 1 / 4 wave plate, and then passes through a first semi-transparent and semi-reflective mirror to transmit a part as the first sub-pulse, and reflect a part to become left-handed circularly polarized light or right-handed circularly polarized light; the left-handed circularly polarized light or the right-handed circularly polarized light passes through a 1 / 4 wave plate to become linear polarized light with a vibration direction perpendicular to the vibration direction of the linear polarized light generated in step 11; then, after being reflected by the polarization beam splitter, it passes through a 1 / 4 wave plate and a first semi-transparent and semi-reflective mirror in sequence, and a part of it transmitted by the first semi-transparent and semi-reflective mirror is used as the second sub-pulse, thereby realizing the time shaping of the laser pulse;

[0022] Step 13: The right-handed circularly polarized light or the left-handed circularly polarized light reflected back by the first semi-transparent and semi-reflective mirror in step 12 is converted into linearly polarized light having the same vibration direction as the linearly polarized light generated in step 11 after passing through a quarter wave plate, and then passes through a polarizing beam splitter;

[0023] Step 14: After the above-mentioned femtosecond laser pulse time shaping, a double pulse sequence is obtained.

[0024] The present invention also discloses another femtosecond laser pulse time shaping system, comprising: cascading at least two of the above polarization components and time shaping devices;

[0025] When two time shaping devices are cascaded, if the pulse delays generated by the two systems are Δt1 and Δt2, the double pulse energy ratio is 1:R1 and 1:R2; if Δt1=Δt2=Δt, the number of sub-pulses in the pulse sequence output after cascading is 3, the time delay between the 3 sub-pulses is Δt, and the energy ratio is 1:R1+R2:R1R2; if Δt1≠Δt2, the number of sub-pulses in the pulse sequence output after cascading is 4, when Δt1<Δt2, the time delays between the sub-pulses are Δt1, Δt2-Δt1, Δt1 in sequence, and the energy ratio is 1:R1:R2:R1R2; when Δt1>Δt2, the time delays between the sub-pulses are Δt2, Δt1-Δt2, Δt2 in sequence, and the energy ratio is 1:R2:R1:R1R2.

[0026] The present invention also discloses another femtosecond laser pulse time shaping system, comprising: a laser, N semi-transparent and semi-reflective mirrors, N reflecting mirrors and a focusing mirror; the initial femtosecond laser pulse generated by the laser is incident on the first semi-transparent and semi-reflective mirror, the transmitted light of the N semi-transparent and semi-reflective mirrors and the reflected light of the last reflecting mirror are incident on the focusing mirror, and the nth reflecting mirror reflects the reflected light of the nth semi-transparent and semi-reflective mirror onto the n+1th semi-transparent and semi-reflective mirror, where n is 1 to N-1, and N is equal to the number of pulses to be generated minus one.

[0027] The femtosecond laser pulse time shaping method includes:

[0028] The initial femtosecond laser pulse generated by the laser is incident on the first semi-transparent and semi-reflective mirror, and then, under the action of the reflective mirror, semi-transparent and semi-reflective mirror and focusing mirror, N+1 sub-pulses are obtained and emitted through the focusing mirror;

[0029] The energy attenuation ratio of N+1 sub-pulses is:

[0030] (1-R1):R1(1-R2):R1R2(1-R3):...:R1R2R3…(1-R N ):R1R2...R N ;

[0031] In the formula, the ratio of the reflectivity of N half-transparent and half-reflective mirrors is R i , i=1,2,3,…,N.

[0032] As a further improvement of the present invention, when N=3, the femtosecond laser pulse time shaping system includes: a laser, a second semi-transparent and semi-reflective mirror, a first reflector, a third semi-transparent and semi-reflective mirror, a second reflector, a fourth semi-transparent and semi-reflective mirror, a third reflector and a focusing mirror; the initial femtosecond laser pulse generated by the laser is incident on the second semi-transparent and semi-reflective mirror, the transmitted light of the second semi-transparent and semi-reflective mirror, the third semi-transparent and semi-reflective mirror, the fourth semi-transparent and semi-reflective mirror and the reflected light of the third reflector are incident on the focusing mirror, the first reflector reflects the reflected light of the second semi-transparent and semi-reflective mirror onto the third semi-transparent and semi-reflective mirror, and the second reflector reflects the reflected light of the third semi-transparent and semi-reflective mirror onto the fourth semi-transparent and semi-reflective mirror, and the above system generates a total of 4 pulses.

[0033] The femtosecond laser pulse time shaping method includes:

[0034] Step 21, the laser pulse generated by the laser is transmitted through the second semi-transparent and semi-reflective mirror, and then transmitted through the focusing mirror as the first sub-pulse;

[0035] Step 22, a portion of the light reflected by the second semi-transparent and semi-reflective mirror is reflected by the first reflector to the third semi-transparent and semi-reflective mirror, and a portion of the light transmitted by the third semi-transparent and semi-reflective mirror is used as a second sub-pulse by passing through a focusing mirror;

[0036] Step 23, a portion reflected by the third semi-transparent and semi-reflective mirror is reflected by the second reflector to the fourth semi-transparent and semi-reflective mirror, and a portion transmitted by the fourth semi-transparent and semi-reflective mirror is used as the third sub-pulse through the focusing mirror;

[0037] Step 24: a portion of the light reflected by the fourth semi-transparent and semi-reflective mirror is reflected to the focusing mirror through the third reflecting mirror, and is used as the fourth sub-pulse through the focusing mirror;

[0038] The energy attenuation ratio between the four sub-pulses is:

[0039] (1-R1):R1(1-R2):R1R2(1-R3):R1R2R3;

[0040] Wherein, R1 is the reflectivity of the second semi-transparent and semi-reflective mirror, R2 is the reflectivity of the third semi-transparent and semi-reflective mirror, and R3 is the reflectivity of the fourth semi-transparent and semi-reflective mirror.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The femtosecond laser pulse time shaping system proposed by the present invention uses only a small number of optical components, occupies a small space, is easy to assemble and adjust, and forms modularization, which is conducive to industrialization;

[0043] 2. The tuning range of the sub-pulse interval and energy ratio in the pulse sequence is wide, and the entire system has a high damage threshold, thereby achieving precise control of high-power laser pulse sequences;

[0044] 3. The femtosecond laser pulse time shaping system proposed in the present invention is scalable and can generate a complex pulse sequence of multiple pulses in a cascade manner, which is of great significance to the application field of femtosecond lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a structural schematic diagram of the femtosecond laser pulse time shaping system disclosed in Example 1 of the present invention;

[0046] Figure 2 for Figure 1 Installation diagram of the time shaping device;

[0047] Figure 3 This is a schematic diagram of the cascade connection of a femtosecond laser pulse time shaping system disclosed in Example 2 of the present invention;

[0048] Figure 4 This is a schematic diagram of the femtosecond laser pulse time shaping method disclosed in Example 3 of the present invention.

[0049] In the figure:

[0050] 1. Laser; 2. 1 / 2 wave plate; 3. Polarization beam splitter; 4. Polarization beam splitter; 5. 1 / 4 wave plate; 6. First semi-transparent and semi-reflective mirror; 7. Internally threaded sleeve; 8. Externally threaded sleeve; 9. Second semi-transparent and semi-reflective mirror; 10. First reflective mirror; 11. Third semi-transparent and semi-reflective mirror; 12. Second reflective mirror; 13. Fourth semi-transparent and semi-reflective mirror; 14. Third reflective mirror; 15. Focusing mirror; 16. First time shaping device; 17. Polarizer; 18. Second time shaping device. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0053] Embodiment 1:

[0054] like Figure 1 As shown, the present invention provides a femtosecond laser pulse time shaping system, comprising: a laser 1 and a 1 / 2 wave plate 2, a polarization beam splitter prism 3, a polarization beam splitter 4, a 1 / 4 wave plate 5 and a first semi-transparent and semi-reflective mirror 6 arranged in sequence along the laser direction of the laser 1, the polarization beam splitter 4, the 1 / 4 wave plate 5 and the first semi-transparent and semi-reflective mirror 6 constitute a time shaping device for time shaping of the femtosecond laser; wherein,

[0055] The 1 / 2 wave plate 2 and the polarization beam splitter 3 are used to convert the initial femtosecond laser pulse generated by the laser 1 into reflected S light and transmitted P light. The reflected S light or the transmitted P light is incident on the polarization beam splitter 4. The polarization beam splitter 4 can be adjusted by rotation to achieve: when the transmitted P light is incident on the polarization beam splitter 4, the polarization beam splitter 4 has high transmittance to the transmitted P light and high reflection to the reflected S light; when the reflected S light is incident on the polarization beam splitter 4, the polarization beam splitter 4 has high transmittance to the reflected S light and high reflection to the transmitted P light. The initial femtosecond laser pulse is subjected to polarization modulation by the 1 / 2 wave plate 2 and the polarization beam splitter 3 and time shaping by the time shaping device, and finally outputs a double pulse sequence.

[0056] The time delay between the two pulses is Δt:

[0057] Δt=2×(ΔL1+d×n d +ΔL2) / c

[0058] Wherein, ΔL1 is the distance between the 1 / 4 wave plate 5 and the polarization beam splitter 4, d is the thickness of the 1 / 4 wave plate 5, and n is d is the refractive index of the material of the quarter wave plate 5, ΔL2 is the distance between the first semi-transparent and semi-reflective mirror 6 and the quarter wave plate 5, and c is the speed of light;

[0059] The energy ratio between the double pulses is 1:R, where R is the reflectivity of the first semi-transparent and semi-reflective mirror 6 .

[0060] To facilitate the installation and adjustment of the time shaping device, place it in Figure 2The whole is composed of an externally threaded sleeve 8 and an internally threaded sleeve 7 which are screwed together. The polarization beam splitter 4 and the 1 / 4 wave plate 5 are fixedly installed in the left internally threaded sleeve 7 through a retaining ring. The first semi-transparent and semi-reflective mirror 6 is fixed in the externally threaded sleeve 8. The interval between the first semi-transparent and semi-reflective mirror 6 and the 1 / 4 wave plate 5 is changed by rotating the externally threaded sleeve 8 and / or the internally threaded sleeve 7 to adjust the pulse spacing.

[0061] The present invention provides a femtosecond laser pulse time shaping method based on the above-mentioned femtosecond laser pulse time shaping system, comprising:

[0062] S111, the initial femtosecond laser pulse generated by the laser is divided into a reflected S polarized light and a transmitted P polarized light after passing through the 1 / 2 wave plate 2 and the polarization beam splitter prism 3;

[0063] S112, after the transmitted P polarized light passes through the polarization beam splitter 4, it is converted into right circularly polarized light through the 1 / 4 wave plate 5, and then passes through the first semi-transparent and semi-reflective mirror 6 to transmit a part as the first sub-pulse, and reflects a part to become left circularly polarized light; the left circularly polarized light passes through the 1 / 4 wave plate 5 to become S polarized light, and after the S polarized light is reflected by the polarization beam splitter 4, it passes through the 1 / 4 wave plate 5 and the first semi-transparent and semi-reflective mirror 6 in sequence, and a part of the light transmitted by the first semi-transparent and semi-reflective mirror 6 is used as the second sub-pulse, thereby realizing the time shaping of the laser pulse;

[0064] The right-handed circularly polarized light reflected back by the first semi-transparent and semi-reflective mirror 6 in S113 and S112 is converted into P-polarized light after passing through the quarter wave plate 5, and then passes through the polarization beam splitter 4;

[0065] S114, obtaining a double pulse sequence after the above-mentioned femtosecond laser pulse time shaping; wherein,

[0066] The time delay between the two pulses is Δt:

[0067] Δt=2×(ΔL1+d×n d +ΔL2) / c

[0068] Where ΔL1 is the distance between the 1 / 4 wave plate and the polarization beam splitter, d is the thickness of the 1 / 4 wave plate, and n is d is the refractive index of the quarter wave plate material, ΔL2 is the distance between the first semi-transparent and semi-reflective mirror and the quarter wave plate, and c is the speed of light;

[0069] The energy ratio between the double pulses is 1:R, where R is the reflectivity of the first semi-transparent and semi-reflective mirror 6 .

[0070] Alternatively, the present invention provides a femtosecond laser pulse time shaping method based on the above-mentioned femtosecond laser pulse time shaping system, comprising:

[0071] S121, the initial femtosecond laser pulse generated by the laser is divided into a beam of reflected S polarized light and a beam of transmitted P polarized light after passing through the 1 / 2 wave plate 2 and the polarization beam splitter prism 3;

[0072] S122, after the transmitted P polarized light passes through the polarization beam splitter 4, it is converted into right circularly polarized light through the 1 / 4 wave plate 5, and then passes through the first semi-transparent and semi-reflective mirror 6 to transmit a part as the first sub-pulse, and reflects a part to become left circularly polarized light; the left circularly polarized light passes through the 1 / 4 wave plate 5 to become S polarized light, and after the S polarized light is reflected by the polarization beam splitter 4, it passes through the 1 / 4 wave plate 5 and the first semi-transparent and semi-reflective mirror 6 in sequence, and a part of the light transmitted by the first semi-transparent and semi-reflective mirror 6 is used as the second sub-pulse, thereby realizing the time shaping of the laser pulse;

[0073] Or, after the reflected S polarized light is transmitted through the polarization beam splitter 4, it is converted into left-handed circularly polarized light through the 1 / 4 wave plate 5, and then after passing through the first semi-transparent and semi-reflective mirror 6, a part of it is transmitted as the first sub-pulse, and a part of it is reflected to become right-handed circularly polarized light; the right-handed circularly polarized light is converted into P polarized light through the 1 / 4 wave plate 5, and after the P polarized light is reflected through the polarization beam splitter 4, it passes through the 1 / 4 wave plate 5 and the first semi-transparent and semi-reflective mirror 6 in sequence, and a part of it is transmitted by the first semi-transparent and semi-reflective mirror 6 as the second sub-pulse, thereby realizing the time shaping of the laser pulse;

[0074] The right-handed circularly polarized light reflected back by the first semi-transparent and semi-reflective mirror 6 in S123 and S122 is converted into P-polarized light after passing through the quarter wave plate 5, and then passes through the polarization beam splitter 4;

[0075] Or, the left-handed circularly polarized light reflected back by the first semi-transparent and semi-reflective mirror 6 in S122 is converted into S-polarized light after passing through the quarter wave plate 5, and then passes through the polarization beam splitter 4;

[0076] S124, obtaining a double pulse sequence after the above-mentioned femtosecond laser pulse time shaping; wherein,

[0077] The time delay between the two pulses is Δt:

[0078] Δt=2×(ΔL1+d×n d +ΔL2) / c

[0079] Where ΔL1 is the distance between the 1 / 4 wave plate and the polarization beam splitter, d is the thickness of the 1 / 4 wave plate, and n is d is the refractive index of the quarter wave plate material, ΔL2 is the distance between the first semi-transparent and semi-reflective mirror and the quarter wave plate, and c is the speed of light;

[0080] The energy ratio between the double pulses is 1:R, where R is the reflectivity of the first semi-transparent and semi-reflective mirror 6 .

[0081] Embodiment 2:

[0082] like Figure 3 As shown, this embodiment includes a laser 1 and a 1 / 2 wave plate 2, a polarization beam splitter prism 3, a first time shaping device 16, a polarizer 17, and a second time shaping device 18, which are cascaded and arranged in sequence along the laser direction of the laser 1, and are used to perform time shaping on the femtosecond laser; wherein the 1 / 2 wave plate 2 and the polarization beam splitter prism 3 are used to convert the initial femtosecond laser pulse generated by the laser 1 into reflected S light and transmitted P light, and the reflected S light or the transmitted P light is incident on the first time shaping device 16 to output a double pulse sequence; the double pulse sequence is converted into linear polarized light after passing through the polarizer 17, and the linear polarized light is incident on the second time shaping device 18, and finally a 3-pulse or 4-pulse sequence is output.

[0083] The first time shaping device 16 and the second time shaping device 18 are as described in Example 1, and the pulse delays generated by them are Δt1 and Δt2 respectively, and the double pulse energy ratios are 1:R1 and 1:R2 respectively. If Δt1=Δt2=Δt, the number of sub-pulses in the pulse sequence output after cascading is 3, and the time delays between the 3 sub-pulses are all Δt, and the energy ratio is 1:R1+R2:R1R2; if Δt1≠Δt2, the number of sub-pulses in the pulse sequence output after cascading is 4, and when Δt1<Δt2, the time delays between the sub-pulses are Δt1, Δt2-Δt1, Δt1 in sequence, and the energy ratio is 1:R1:R2:R1R2; when Δt1>Δt2, the time delays between the sub-pulses are Δt2, Δt1-Δt2, Δt2 in sequence, and the energy ratio is 1:R2:R1:R1R2.

[0084] On this basis, it is also possible to choose to cascade N time shaping devices.

[0085] Alternatively, the present invention provides a femtosecond laser pulse time shaping method based on the above-mentioned femtosecond laser pulse time shaping system, comprising:

[0086] S131, the initial femtosecond laser pulse generated by the laser is divided into a beam of reflected S polarized light and a beam of transmitted P polarized light after passing through the 1 / 2 wave plate 2 and the polarization beam splitter prism 3;

[0087] S132, transmitting the P polarized light to be incident on the first time shaping device 16 to obtain time shaping of the laser pulse;

[0088] Or, the reflected S polarized light is incident on the first time shaping device 16 to obtain time shaping of the laser pulse;

[0089] S133, obtaining a double pulse sequence after the above-mentioned femtosecond laser pulse time shaping;

[0090] S134, the double pulse sequence is transformed into a linearly polarized double pulse after passing through a polarizer 17;

[0091] S135, the linearly polarized double pulse is incident on the second time shaping device 18 to obtain time shaping of the laser pulse;

[0092] S136, obtaining a multi-pulse sequence after the above-mentioned femtosecond laser pulse time shaping;

[0093] in,

[0094] The pulse delays generated by the first time shaping device 16 and the second time shaping device 18 are Δt1 and Δt2 respectively, and the double pulse energy ratios are 1:R1 and 1:R2 respectively. If Δt1=Δt2=Δt, the number of sub-pulses in the pulse sequence output after cascading is 3, and the time delays between the 3 sub-pulses are all Δt, and the energy ratio is 1:R1+R2:R1R2; if Δt1≠Δt2, the number of sub-pulses in the pulse sequence output after cascading is 4, and when Δt1<Δt2, the time delays between the sub-pulses are Δt1, Δt2-Δt1, Δt1 in sequence, and the energy ratio is 1:R1:R2:R1R2; when Δt1>Δt2, the time delays between the sub-pulses are Δt2, Δt1-Δt2, Δt2 in sequence, and the energy ratio is 1:R2:R1:R1R2.

[0095] On this basis, it is also possible to choose to cascade N time shaping devices.

[0096] Embodiment 3:

[0097] The invention provides a femtosecond laser pulse time shaping system, comprising: a laser, N semi-transparent and semi-reflective mirrors, N reflective mirrors and a focusing mirror; an initial femtosecond laser pulse generated by the laser is incident on the first semi-transparent and semi-reflective mirror, transmitted light of the N semi-transparent and semi-reflective mirrors and reflected light of the last reflective mirror are incident on the focusing mirror, and the nth reflective mirror reflects the reflected light of the nth semi-transparent and semi-reflective mirror onto the n+1th semi-transparent and semi-reflective mirror, where n is 1 to N-1, and N is equal to the number of pulses to be generated minus one.

[0098] The present invention provides a femtosecond laser pulse time shaping method based on the above-mentioned femtosecond laser pulse time shaping system, comprising:

[0099] The initial femtosecond laser pulse generated by the laser is incident on the first semi-transparent and semi-reflective mirror, and then under the action of the reflecting mirror, semi-transparent and semi-reflective mirror and focusing mirror, N+1 sub-pulses are obtained and emitted through the focusing mirror.

[0100] The energy attenuation ratio of N+1 sub-pulses is:

[0101] (1-R1):R1(1-R2):R1R2(1-R3):...:R1R2R3…(1-R N ):R1R2...R N ;

[0102] In the formula, the ratio of the reflectivity of the semi-transparent and semi-reflective mirrors is R i , i=1,2,3,…,N.

[0103] Specific:

[0104] like Figure 3 As shown, when N=3, the femtosecond laser pulse time shaping system includes: a laser, a second semi-transparent mirror 9, a first reflector 10, a third semi-transparent mirror 11, a second reflector 12, a fourth semi-transparent mirror 13, a third reflector 14 and a focusing mirror 15; the initial femtosecond laser pulse generated by the laser is incident on the second semi-transparent mirror 9, the transmitted light of the second semi-transparent mirror 9, the third semi-transparent mirror 11, the fourth semi-transparent mirror 13 and the reflected light of the third reflector 14 are incident on the focusing mirror 15, the first reflector 10 reflects the reflected light of the second semi-transparent mirror 9 onto the third semi-transparent mirror 11, the second reflector 12 reflects the reflected light of the third semi-transparent mirror 11 onto the fourth semi-transparent mirror 13, and the above system generates 4 pulses in total.

[0105] The shaping methods include:

[0106] S21, the laser pulse generated by the laser is transmitted through the second semi-transparent and semi-reflective mirror 9, and then transmitted through the focusing mirror 15 as the first sub-pulse;

[0107] S22, a portion reflected by the second semi-transparent mirror 9 is reflected by the first reflecting mirror 10 to the third semi-transparent mirror 11, and a portion transmitted by the third semi-transparent mirror 11 is transmitted by the focusing mirror 15 as a second sub-pulse;

[0108] S23, a portion reflected by the third semi-transparent mirror 11 is reflected by the second reflecting mirror 12 to the fourth semi-transparent mirror 13, and a portion transmitted by the fourth semi-transparent mirror 13 is passed through the focusing mirror 15 as a third sub-pulse;

[0109] S24, a portion reflected by the fourth semi-transparent mirror 13 is reflected by the third reflecting mirror 14 to the focusing mirror 15, and is used as the fourth sub-pulse by the focusing mirror 15;

[0110] The energy attenuation ratio between the four sub-pulses is:

[0111] (1-R1):R1(1-R2):R1R2(1-R3):R1R2R3;

[0112] Wherein, R1 is the reflectivity of the second semi-transparent and semi-reflective mirror, R2 is the reflectivity of the third semi-transparent and semi-reflective mirror, and R3 is the reflectivity of the fourth semi-transparent and semi-reflective mirror.

[0113] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A femtosecond laser pulse time shaping system, characterized in that: include: A laser and a polarization component, a polarization beam splitter, a quarter wave plate and a first semi-transparent and semi-reflective mirror arranged in sequence along the laser direction of the laser; The polarization component is used to convert the initial femtosecond laser pulse generated by the laser into linearly polarized light; The polarization beam splitter is used to have high transmittance for linear polarized light incident on the polarization beam splitter and high reflection for linear polarized light perpendicular to the vibration direction of the incident linear polarized light; The polarization beam splitter, the quarter wave plate and the first semi-transparent and semi-reflective mirror constitute a time shaping device for performing time shaping on the femtosecond laser; The initial femtosecond laser pulse undergoes polarization modulation by the polarization component and time shaping processing by the time shaping device, and finally outputs a double-pulse sequence.

2. The femtosecond laser pulse time shaping system according to claim 1, wherein: The polarization component includes a 1 / 2 wave plate and a polarization beam splitter prism sequentially arranged along the laser direction of the laser, or the polarization component includes a polarizer arranged along the laser direction of the laser.

3. The femtosecond laser pulse time shaping system according to claim 1, wherein: The time delay between the two pulses is Δt: Δt=2×(ΔL1+d×n d +ΔL2) / c Where ΔL1 is the distance between the 1 / 4 wave plate and the polarization beam splitter, d is the thickness of the 1 / 4 wave plate, and n is the distance between the 1 / 4 wave plate and the polarization beam splitter. d is the refractive index of the quarter-wave plate material, ΔL2 is the distance between the first semi-transparent and semi-reflective mirrors and the quarter-wave plate, and c is the speed of light; The energy ratio between the two pulses is 1:R, where R is the reflectivity of the first semi-transparent and semi-reflective mirror.

4. The femtosecond laser pulse time shaping system according to claim 1, wherein: Also includes: An externally threaded sleeve and an internally threaded sleeve that are screwed together; The polarization beam splitter and the quarter wave plate are fixedly installed in the internal threaded sleeve through a retaining ring, and the first semi-transparent and semi-reflective mirror is fixed in the external threaded sleeve. The pulse spacing is adjusted by rotating the external threaded sleeve and / or the internal threaded sleeve to change the interval between the first semi-transparent and semi-reflective mirror and the quarter wave plate.

5. A femtosecond laser pulse time shaping method based on the femtosecond laser pulse time shaping system according to any one of claims 1 to 4, characterized in that: include: Step 11: The initial femtosecond laser pulse generated by the laser becomes linearly polarized light after passing through a polarization component; Step 12: After the linearly polarized light passes through the polarization beam splitter, it is converted into right-handed circularly polarized light or left-handed circularly polarized light through a quarter-wave plate. Then, after passing through a first semi-transparent and semi-reflective mirror, a portion of the light is transmitted as a first sub-pulse, and a portion of the light is reflected to become left-handed circularly polarized light or right-handed circularly polarized light. The left-handed circularly polarized light or right-handed circularly polarized light is converted into linear polarized light with a vibration direction perpendicular to the vibration direction of the linear polarized light generated in step 11 through a quarter-wave plate. Then, after being reflected by the polarization beam splitter, the light passes through a quarter-wave plate and a first semi-transparent and semi-reflective mirror in sequence. A portion of the light transmitted by the first semi-transparent and semi-reflective mirror serves as a second sub-pulse, thereby achieving time shaping of the laser pulse. Step 13: The right-handed circularly polarized light or the left-handed circularly polarized light reflected back by the first semi-transparent and semi-reflective mirror in step 12 is converted into linearly polarized light having the same vibration direction as the linearly polarized light generated in step 11 after passing through a quarter-wave plate, and then passes through a polarizing beam splitter; Step 14: After the above-mentioned femtosecond laser pulse time shaping, a double pulse sequence is obtained.

6. A femtosecond laser pulse time shaping system, comprising: A laser and a cascade of at least two polarization components and a time shaping device according to any one of claims 1 to 4; When two time shaping devices are cascaded, if the pulse delays generated by the two time shaping devices are Δt1 and Δt2, the double-pulse energy ratios are 1:R1 and 1:R2; if Δt1=Δt2=Δt, then the number of sub-pulses in the pulse sequence output after cascading is 3, the time delay between the three sub-pulses is Δt, and the energy ratio is 1:R1+R2:R1R2; if Δt1≠Δt2, then the number of sub-pulses in the pulse sequence output after cascading is 4, when Δt1<Δt2, the time delays between the sub-pulses are Δt1, Δt2-Δt1, and Δt1 in sequence, and the energy ratio is 1:R1:R2:R1R2; when Δt1>Δt2, the time delays between the sub-pulses are Δt2, Δt1-Δt2, and Δt2 in sequence, and the energy ratio is 1:R2:R1:R1R2.

7. A femtosecond laser pulse time shaping system, characterized in that: include: A laser, N semi-transparent and semi-reflective mirrors, N reflective mirrors and a focusing mirror; the initial femtosecond laser pulse generated by the laser is incident on the first semi-transparent and semi-reflective mirror, the transmitted light of the N semi-transparent and semi-reflective mirrors and the reflected light of the last reflective mirror are incident on the focusing mirror, and the nth reflective mirror reflects the reflected light of the nth semi-transparent and semi-reflective mirror onto the n+1th semi-transparent and semi-reflective mirror, where n ranges from 1 to N-1, and N is equal to the number of pulses to be generated minus one.

8. The femtosecond laser pulse time shaping system according to claim 7, wherein: When N=3, the femtosecond laser pulse time shaping system includes: a laser, a second semi-transparent semi-reflective mirror, a first reflector, a third semi-transparent semi-reflective mirror, a second reflector, a fourth semi-transparent semi-reflective mirror, a third reflector and a focusing mirror; the initial femtosecond laser pulse generated by the laser is incident on the second semi-transparent semi-reflective mirror, the transmitted light of the second semi-transparent semi-reflective mirror, the third semi-transparent semi-reflective mirror, the fourth semi-transparent semi-reflective mirror and the reflected light of the third reflector are incident on the focusing mirror, the first reflector reflects the reflected light of the second semi-transparent semi-reflective mirror onto the third semi-transparent semi-reflective mirror, and the second reflector reflects the reflected light of the third semi-transparent semi-reflective mirror onto the fourth semi-transparent semi-reflective mirror. The above system generates a total of 4 pulses.

9. A femtosecond laser pulse time shaping method based on the femtosecond laser pulse time shaping system according to claim 7, characterized in that: include: The initial femtosecond laser pulse generated by the laser is incident on the first semi-transparent and semi-reflective mirror. Then, under the action of the reflective mirror, semi-transparent and semi-reflective mirror and focusing mirror, N+1 sub-pulses are emitted through the focusing mirror. The energy attenuation ratio of N+1 sub-pulses is: (1-R1):R1(1-R2):R1R2(1-R3):...:R1R2R3…(1-R N ):R1R2...R N ; In the formula, the ratio of the reflectivity of N half-transparent and half-reflective mirrors is R i , i=1,2,3,…,N.

10. A femtosecond laser pulse time shaping method based on the femtosecond laser pulse time shaping system according to claim 8, characterized in that: include: Step 21: The laser pulse generated by the laser is transmitted through the second semi-transparent and semi-reflective mirror and then transmitted through the focusing mirror as the first sub-pulse; Step 22: A portion of the light reflected by the second semi-transparent mirror is reflected by the first reflecting mirror to the third semi-transparent mirror, and a portion of the light transmitted by the third semi-transparent mirror is transmitted by the focusing mirror as the second sub-pulse; Step 23: A portion of the light reflected by the third semi-transparent mirror is reflected by the second reflecting mirror to the fourth semi-transparent mirror, and a portion of the light transmitted by the fourth semi-transparent mirror is transmitted by the focusing mirror as the third sub-pulse; Step 24: A portion of the light reflected by the fourth semi-transparent mirror is reflected by the third reflector to the focusing mirror, and is used as the fourth sub-pulse by the focusing mirror; The energy attenuation ratio between the four sub-pulses is: (1-R1):R1(1-R2):R1R2(1-R3):R1R2R3; Wherein, R1 is the reflectivity of the second semi-transparent and semi-reflective mirror, R2 is the reflectivity of the third semi-transparent and semi-reflective mirror, and R3 is the reflectivity of the fourth semi-transparent and semi-reflective mirror.

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