阅读说明：本技术 一种产生160nm飞秒真空紫外激光脉冲的装置 (Device for generating 160nm femtosecond vacuum ultraviolet laser pulse ) 是由 魏洁 金兵 张嵩 张冰 龙金友 于 2021-07-19 设计创作，主要内容包括：本发明公开了一种产生160nm飞秒真空紫外激光脉冲的装置包括飞秒激光系统,飞秒激光光路系统,光丝成丝及四波混频产生系统,以及160nm激光脉冲检测及优化系统,本发明依靠现有的钛宝石飞秒激光系统将激光波段从800nm扩展到真空紫外波段,实现了160nm真空紫外波段飞秒光的输出,以及提供了一种能检测该波长的存在并将该波长的能量优化到最强的方法,最终测得其单脉冲能量为69nJ/pulse。(The invention discloses a device for generating 160nm femtosecond vacuum ultraviolet laser pulse, which comprises a femtosecond laser system, a femtosecond laser optical path system, a filament filamentation and four-wave mixing generation system and a 160nm laser pulse detection and optimization system, wherein the invention expands a laser wave band from 800nm to a vacuum ultraviolet wave band by depending on the existing titanium gem femtosecond laser system, thereby realizing the output of 160nm vacuum ultraviolet wave band femtosecond light, providing a method capable of detecting the existence of the wavelength and optimizing the energy of the wavelength to be the strongest, and finally measuring the single pulse energy to be 69 nJ/pulse.)

1. An apparatus for generating 160nm femtosecond vacuum ultraviolet laser pulses, comprising a femtosecond laser system (1),

light with the wavelength of 800nm output from the femtosecond laser system (1) is divided into transmitted light and reflected light through the beam splitting plate (2a), the reflected light is firstly reflected by the first reflecting mirror (2b), the light reflected by the first reflecting mirror (2b) is expanded by the telescope system after passing through the half wave plate (2c), and the expanded light is respectively reflected by the second reflecting mirror (2f) and the third reflecting mirror (2g) and then is collected by the first focusing lens (2 h); the transmitted light is frequency-doubled into light with the wavelength of 400nm through a BBO frequency doubling crystal (2j), the light with the wavelength of 400nm sequentially passes through a fourth reflector (2k), a fifth reflector (2l), a sixth reflector (2m), a seventh reflector (2n) and an eighth reflector (2o) to be reflected and then focused by a second focusing lens (2p), the light with the wavelength of 800nm focused by the first focusing lens (2h) and the light with the wavelength of 400nm focused by the second focusing lens (2p) are combined through a beam combining sheet (2i),

the light combined by the beam combining sheet (2i) enters a filamentation and four-wave mixing generation gas pool (3e) through a Brewster window mirror (3a) and then generates a four-wave mixing effect in the filamentation and four-wave mixing generation gas pool (3e) to generate new light with the wavelengths of 200nm, 266nm and 160nm, and the light with the wavelengths of 800nm, 400nm, 200nm, 266nm and 160nm transmits CaF₂The window sheet is split by the triple prism (4b) after being incident to the vacuum cavity (4c),

the light that is split by prism (4b) shines on scribbling slice (4d) of sodium salicylate, and thin slice (4d) are close to optic fibre (4e) one end, and spectrum appearance (4f) are connected to optic fibre (4e) other end, and spectrum appearance (4f) link to each other with computer (4g) through USB data line (4 h).

2. An apparatus for generating 160nm femtosecond vacuum ultraviolet laser pulses as set forth in claim 1, wherein the telescope system includes a plano-concave lens (2d) and a plano-convex lens (2 e).

3. The apparatus for generating 160nm femtosecond vacuum ultraviolet laser pulses as set forth in claim 1, further comprising a five-way type vacuum chamber, wherein the brewster window mirror (3a) is disposed at one port of the five-way type vacuum chamber, the light inlet end of the filamentation and four-wave mixing generation gas cell (3e), the high purity argon gas bottle (3d), the vacuum gauge (3c), and the mechanical pump (3b) are respectively connected to the remaining four ports of the five-way type vacuum chamber, and the combined light is incident into the light inlet end of the filamentation and four-wave mixing generation gas cell (3e) through the five-way type vacuum chamber after passing through the brewster window mirror (3 a).

4. The apparatus as claimed in claim 1, wherein the filamentation and four-wave mixing gas generating cell (3e) is filled with argon gas.

5. An apparatus for generating 160nm femtosecond vacuum ultraviolet laser pulses as set forth in claim 1, wherein the triangular prism (4b) is MgF₂And (3) material quality.

6. The device for generating 160nm femtosecond vacuum ultraviolet laser pulses as set forth in claim 1, wherein the head wave positions of 800nm light and 400nm light in the combined light of the beam combining sheet (2i) are the same, and the 800nm light and the 400nm light in the combined light of the beam combining sheet (2i) are coaxial.

Technical Field

The invention relates to the technical field of ultrafast light sources, in particular to a device for generating 160nm femtosecond vacuum ultraviolet laser pulses.

Background

Vacuum ultraviolet light as the name implies needs to propagate in vacuum and be absorbed in air, while femtosecond vacuum ultraviolet laser pulses have a femtosecond pulse width (10)^-15Seconds) and a wavelength in the vacuum ultraviolet band, are widely used in spectroscopy, as well as in microelectronics and material processing.

Currently, the femtosecond vacuum ultraviolet laser is mainly generated by a free electron laser, a higher harmonic wave, four-wave mixing of an optical filament, and the like. The free electron laser uses high-energy electrons as working substances, the electrons pass through a periodic magnetic field, and kinetic energy is transferred to an external field by the electrons in the interaction process of the electrons and the external field, so that the intensity of the external field is increased. The pulse output by the method has the advantages of high energy, wide tuning range and the like, but the pulse output by the method is generally realized as a large scientific device, not only occupies a large area, but also has very high manufacturing cost, and is not suitable for being used in a common laboratory. The high-order harmonic wave of the strong field is realized based on a three-step model theory, atoms are ionized by an external field under the action of the strong field, and because an electric field is a periodic sine function, when the polarity of the electric field is changed, ionized electrons have certain probability to collide with a mother nucleus again, laser pulses can be radiated in the collision process, and energy is provided by the external field. The laser pulse obtained by the method has the advantages of good coherence, narrow pulse width, wide tunable range and the like, and is generally used for realizing extreme ultraviolet and attosecond (10)^-18Second) of the laser pulse, the output frequency is complex, it is difficult to obtain laser pulses with good monochromaticity, and the conversion efficiency of this method is low, usually 10^-6-10^-5That is, 1 watt of fundamental frequency light can only obtain 1-10 microwatts of vacuum ultraviolet laser pulse, and it is difficult to obtain laser with high single pulse energy.

In view of the above problems, the present invention provides an apparatus and a detection method for generating 160nm femtosecond vacuum ultraviolet laser pulses based on a four-wave mixing technique of an optical fiber. The basic principle is as follows: the titanium gem laser firstly outputs 800nm laser, then splits the 800nm laser and divides one pathThe frequency doubling of light is 400nm, then the two beams of light are respectively acted with argon in a collinear focusing mode, light threads are respectively formed at the moment (the essence of the light threads is a plasma channel formed when strong light interacts with substances), the two beams of light are identical in optical path and are overlapped in space by adjusting the optical path, and a series of four-wave mixing effects can occur at the moment, such as 2 omega +2 omega-omega → 3 omega, 3 omega +2 omega-omega → 4 omega, 4 omega +2 omega-omega → 5 omega, so that 160nm laser pulses are output. The femtosecond vacuum ultraviolet laser pulse obtained by the four-wave frequency mixing method of the optical fiber has stable optical power, good spot quality and high conversion efficiency which can reach 10^-4The pulse output of a single wavelength can be realized through a prism or a high-reflection mirror for reflecting a specific wavelength. Now, a set of table-type femtosecond vacuum ultraviolet laser light source is established in the laboratory, and molecular reaction kinetics are researched by combining a speed imaging device.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provide a device for generating 160nm femtosecond vacuum ultraviolet laser pulses.

The above object of the present invention is achieved by the following technical solutions:

a device for generating 160nm femtosecond vacuum ultraviolet laser pulse comprises a femtosecond laser system,

light with the wavelength of 800nm output from the femtosecond laser system is divided into transmitted light and reflected light through a beam splitting sheet, the reflected light is firstly reflected by a first reflecting mirror, the light reflected by the first reflecting mirror is subjected to beam expansion through a telescope system after passing through a half wave plate, and the expanded light is respectively collected by a first focusing lens after being reflected by a second reflecting mirror and a third reflecting mirror; the transmitted light is frequency-doubled into light with the wavelength of 400nm through a BBO frequency doubling crystal, the light with the wavelength of 400nm sequentially passes through a fourth reflector, a fifth reflector, a sixth reflector, a seventh reflector and an eighth reflector and then is focused by a second focusing lens, the light with the wavelength of 800nm focused by the first focusing lens and the light with the wavelength of 400nm focused by the second focusing lens are combined through a beam combining sheet,

the light combined by the beam combining sheet enters a filament forming and four-wave mixing generation gas pool through a Brewster window mirror and then is formedGenerating four-wave mixing effect in the silk and four-wave mixing generation gas pool to generate new light with wavelengths of 200nm, 266nm and 160nm, and transmitting light with wavelengths of 800nm, 400nm, 200nm, 266nm and 160nm through CaF₂The window sheet is split by the triple prism after being incident to the vacuum cavity,

the light after being split by the triple prism is irradiated on the thin sheet coated with the sodium salicylate, one end of the optical fiber is close to the thin sheet, the other end of the optical fiber is connected with the spectrometer, and the spectrometer is connected with the computer through a USB data line.

The telescope system as described above comprises a plano-concave lens and a plano-convex lens.

A device for generating 160nm femtosecond vacuum ultraviolet laser pulse further comprises a five-way vacuum cavity, a Brewster window mirror is arranged at one port of the five-way vacuum cavity, a light inlet end of a filamentation and four-wave mixing generation gas pool, a high-purity argon bottle, a vacuum gauge and a mechanical pump are respectively connected with the other four ports of the five-way vacuum cavity, and combined light penetrates through the Brewster window mirror and then enters the light inlet end of the filamentation and four-wave mixing generation gas pool through the five-way vacuum cavity.

The filamentation and four-wave mixing generation pool is filled with argon.

The prism is MgF₂And (3) material quality.

The first wave positions of the 800nm light and the 400nm light in the light combined by the beam combining sheet are the same, and the 800nm light and the 400nm light in the light combined by the beam combining sheet are coaxial.

Compared with the prior art, the invention has the following advantages:

the laser band is expanded from 800nm to a vacuum ultraviolet band by depending on the existing titanium gem femtosecond laser system, the output of 160nm vacuum ultraviolet band femtosecond light is realized, a method capable of detecting the existence of the wavelength and optimizing the energy of the wavelength to be the strongest is provided, and finally the single pulse energy is measured to be 69 nJ/pulse.

Drawings

FIG. 1 is a schematic diagram of the apparatus of the present invention;

FIG. 2(a) is a diagram of a light filament generated by four-wave mixing effect in the combined beam light;

FIG. 2(b) shows the fluorescence emitted by a 160nm laser impinging on sodium salicylate;

FIG. 3 is a fluorescence spectrum of a filament formed in argon;

FIG. 4 is a spectrum of 425nm fluorescence emitted by sodium salicylate excited by 160nm laser pulses.

In the figure: 1-femtosecond laser system; 2 a-beam splitter (55% reflection and 45% transmission); 2 b-first mirror (800nm high mirror); 2 f-second mirror (800nm high reflectance mirror); 2 g-third mirror (800nm high mirror); 2 c-half wave plate (800 nm); 2 d-plano-concave lens (focal length 500 mm); 2 e-plano-convex lens (focal length 1000 mm); 2j-BBO frequency doubling crystal (29.2 degree); 2 k-fourth mirror (400nm high mirror); 2 l-fifth mirror (400nm high mirror); 2 m-sixth mirror (400nm high mirror); 2 n-seventh mirror (400nm high mirror); 2 o-eighth mirror (400nm high mirror); 2 p-second focusing lens (focal length 1000 mm); 2 h-first focusing lens (focal length 1000 mm); 2 i-a beam combining sheet; 3 a-Brewster window mirror; 3 b-a mechanical pump; 3 c-vacuum gauge; 3 d-a high-purity argon bottle; 3 e-filamentation and four-wave mixing generation gas pool; 4 a-vacuum pump group (molecular pump + oil-free dry pump); 4 b-triple prism (material is MgF)₂) (ii) a 4 c-a vacuum chamber; 4 d-flakes (coated with sodium salicylate); 4 e-an optical fiber; 4 f-spectrometer; 4 g-computer; 4h-USB data line.

Detailed Description

The present invention will be described in further detail with reference to examples for the purpose of facilitating understanding and practice of the invention by those of ordinary skill in the art, and it is to be understood that the present invention has been described in the illustrative embodiments and is not to be construed as limited thereto.

As shown in FIG. 1, an apparatus for generating 160nm femtosecond vacuum ultraviolet laser pulses includes a femtosecond laser system 1, a femtosecond laser optical path system, a filament filamentation and four-wave mixing generation system, and a 160nm laser pulse detection and optimization system.

The femtosecond laser system 1 is a commercial titanium sapphire laser system, the central wavelength of output light is 800nm, the pulse width is 100fs, the repetition frequency is 1kHz, and the single-pulse energy is 4 mJ/pulse.

The femtosecond laser optical path system comprises a beam splitting plate 2a (55% reflectivity and 45% transmissivity), a first reflecting mirror 2b, a second reflecting mirror 2f, a third reflecting mirror 2g, a half-wave plate 2c of 800nm, a telescope system for expanding the diameter of a light spot by one time, a BBO frequency doubling crystal 2j, a fourth reflecting mirror 2k, a fifth reflecting mirror 2l, a sixth reflecting mirror 2m, a seventh reflecting mirror 2n, an eighth reflecting mirror 2o, a beam combining plate 2i, a first focusing lens 2h and a second focusing lens 2 p.

The first mirror 2b, the second mirror 2f, and the third mirror 2g are high mirrors having a wavelength of 800nm, the fifth mirror 2l, the sixth mirror 2m, the seventh mirror 2n, and the eighth mirror 2o are high mirrors having a wavelength of 400 nm.

The 800nm half-wave plate rotates the polarization direction of the laser light having a center wavelength of 800nm by 90 °.

The telescope system includes a plano-concave lens 2d and a plano-convex lens 2 e. A beam expanding type telescope system consisting of a plano-concave lens 2d and a plano-convex lens 2e is arranged on an 800nm light path, and aims to enable a Gaussian beam after expansion to have stronger focusing capacity and be easier to form a light wire, enable 160nm laser pulse generated by four-wave mixing to be stronger, and enable the light beam to be expanded and then be subjected to wire forming under the condition of poor wire forming effect.

The light with the wavelength of 800nm output from the femtosecond laser system 1 is reflected by the beam splitting plate 2a, 55% of energy is reflected to form reflected light, 45% of energy is transmitted to form transmitted light, the reflected light firstly passes through the first reflecting mirror 2b, then the polarization direction of the reflected light is rotated by 90 degrees through the half-wave plate 2c, then the diameter of a light spot is expanded by one time through the telescope system, and then the reflected light is collected by the first focusing lens 2h after being reflected by the second reflecting mirror 2f and the third reflecting mirror 2g respectively; the transmitted light firstly passes through a BBO frequency doubling crystal 2j, the frequency of light with the wavelength of 800nm is doubled into light with the wavelength of 400nm, then the light with the wavelength of 400nm is focused by a second focusing lens 2p after being reflected by a fourth reflector 2k, a fifth reflector 2l, a sixth reflector 2m, a seventh reflector 2n and an eighth reflector 2o in sequence, and finally the light with the wavelength of 800nm and the light with the wavelength of 400nm, which are focused by the first focusing lens 2h and the second focusing lens 2p, are combined by a beam combining sheet 2i to obtain combined light.

Filament filamentation and four-wave mixing generationThe system comprises a Brewster window mirror 3a, a mechanical pump 3b, a vacuum gauge 3c, a high-purity argon bottle 3d and a filamentation and four-wave mixing generation gas pool 3 e. Firstly, a filamentation and four-wave mixing generation gas pool 3e is vacuumized to be below 5Pa by a mechanical pump 3b, then argon gas is filled into the filamentation and four-wave mixing generation gas pool 3e through a high-purity argon gas bottle 3d, the air pressure is maintained at 80Torr, firstly, 800nm light focused by a first focusing lens 2h and 400nm light focused by a second focusing lens 2p are combined by a beam combining plate 2i, then the combined light enters the filamentation and four-wave mixing generation gas pool 3e through a Brewster window lens 3a, when the two beams of light combined by the beam combining plate 2i are overlapped in space and synchronized in time, namely, the first wave positions of the 800nm light and the 400nm light in the light combined by the beam combining plate 2i are the same, and the 800nm light and the 400nm light in the light combined by the beam combining plate 2i are coaxial, the light silk can be obviously increased, the brightness can be obviously improved, such as the bright silk shown in figure 2(a), FIG. 3 shows fluorescence spectra of filament formed in argon, and the combined light beam generates new three frequencies of light in filament forming and four-wave mixing generating gas pool 3e, in this embodiment, the new generated light with wavelengths of 200nm, 266nm and 160nm, respectively, and the 800nm, 400nm, 200nm, 266nm and 160nm light are spatially combined to form mixed frequency light, and the mixed frequency light is transmitted through CaF₂Since the light of the above-mentioned 5 frequencies spatially coincide with each other, the window sheet enters the triangular prism 4b, and the light of 160nm required for the light splitting by the triangular prism 4b needs to be extracted separately.

The laser pulse split by the triple prism 4b irradiates on the thin slice 4d coated with the sodium salicylate, one of which only exists in vacuum and disappears in the air, which proves that the wavelength is in the vacuum ultraviolet band, the spectrometer 4f reads that the fluorescence emitted by the laser pulse excited sodium salicylate is 425nm, and proves that the wavelength is 160 nm.

The brewster window mirror 3a is arranged at one port of the five-way vacuum cavity, the light inlet end of the filamentation and four-wave mixing generation gas pool 3e, the high-purity argon bottle 3d, the vacuum gauge 3c and the mechanical pump 3b are respectively connected with the other four ports of the five-way vacuum cavity, and combined light penetrates through the brewster window mirror 3a and then enters the light inlet end of the filamentation and four-wave mixing generation gas pool 3e through the five-way vacuum cavity.

The 160nm laser pulse detection and optimization system comprises a vacuum pump set 4a (a molecular pump and an oil-free dry pump), a prism 4b, a vacuum cavity 4c, a slice 4d, an optical fiber 4e, a high-sensitivity spectrometer 4f, a computer 4g and a USB data line 4 h. The slice 4d is coated with sodium salicylate, the vacuum cavity 4c and the light-emitting end of the filamentation and four-wave mixing generation gas box 3e pass through CaF₂The window is sealed and separated, wherein the vacuum degree of the vacuum cavity 4c is maintained below 5Pa, when four-wave mixing occurs, the light is irradiated on the thin sheet 4d coated with sodium salicylate after being split by the triple prism 4b, a bright spot is observed, as shown in figure 2(b), the bright spot exists in vacuum and disappears in the atmosphere, the wavelength is proved to be in the vacuum ultraviolet band, and in order to reduce the energy loss, the material of the triple prism 4b is MgF₂. The optical fiber 4e is close to the position where the light spot appears on the water sample sodium sheet 4d, the wavelength of the light spot is 425nm measured by a spectrometer 4f, as shown in fig. 4, the light with the wavelength of 160nm excites the fluorescence emitted by the sodium salicylate, the spectrometer 4f is connected with a computer 4g through a USB data line 4h, the measured spectrum data is displayed and stored in the computer 4g, the first reflector 2b, a half-wave plate 2c, a telescope system, a second reflector 2f, a third reflector 2g, a first focusing lens 2h, a BBO frequency doubling crystal 2j, a fourth reflector 2k, a fifth reflector 2l, a sixth reflector 2m, a seventh reflector 2n, an eighth reflector 2o and a second focusing lens 2p are adjusted, the first wave positions of the light with the wavelength of 800nm and the light with the wavelength of 400nm in the light combined by the beam combining plate 2i are adjusted to be the same, and the first wave positions of the light with the wavelength of 800nm and the light with the wavelength of 400nm in the light combined by the beam combining plate 2i are coaxial, the measured 425nm fluorescence can be optimized to the maximum and thus the 160nm laser pulse energy optimized to the maximum.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.