CN117878712A - Device for generating strong white light laser without optical damage - Google Patents
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- 230000006378 damage Effects 0.000 title claims description 31
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- 239000013078 crystal Substances 0.000 claims abstract description 52
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000005086 pumping Methods 0.000 claims abstract description 24
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- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical group [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 10
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- 229910001751 gemstone Inorganic materials 0.000 claims abstract description 7
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Abstract
The invention relates to the technical field of strong laser nonlinear frequency conversion, in particular to a white light femtosecond laser nonlinear pole system which comprises a pumping light source, a third-order nonlinear stretcher and a second harmonic converter, wherein the pumping light source is titanium gemstone femtosecond pulse laser with the center wavelength of 800nm, the pulse width is 50fs, the repetition frequency is 1kHz, the single pulse energy is more than 4mJ, and the white light femtosecond laser nonlinear pole system has the characteristic of high peak power. The second harmonic converter is a 5% MgO doped chirped periodic polarized lithium niobate crystal, the periodic structure of the second harmonic converter is changed along the light propagation direction according to the rule of continuous chirping change, and the second harmonic converter has a plurality of inverted lattice vector bands with wide enough bandwidth and high effective nonlinear coefficient, can effectively compensate the phase mismatch amount in the second harmonic nonlinear frequency conversion process within a certain bandwidth range, and realizes ultra-wideband high-efficiency second harmonic generation.
Description
Technical Field
The invention relates to the technical field of strong laser nonlinear frequency conversion, in particular to a white light femtosecond laser nonlinear pole system.
Background
The powerful power for constructing ultra-wideband laser sources derives from a range of attractive applications such as large-scale biodynamic imaging, femtosecond chemistry, telecommunications, sensing, and ultrafast science. Many of these applications have strongly desired to develop a so-called "tri-high" supercontinuum white light laser with large pulse energy and high peak power, large spectral bandwidth and ultra-flat spectral profile. Optical supercontinuum generation is an indispensable technique for generating supercontinuum white light laser light sources. The most common method for realizing supercontinuum generation is to use the third-order optical nonlinear effect in amorphous materials, such as the self-phase modulation effect driven by high-peak power femtosecond pump pulse to generate supercontinuum, the corresponding power density should be very high, up to dozens of GW/cm < 2 >, so that significant third-order nonlinear interaction can be excited. One popular approach is to concentrate the pump laser pulse energy in a small spatial region, such as the core of a microstructured fiber, but this approach has drawbacks such as small modal area, low pulse energy (< < 1J), low brightness, poor spectral profile flatness. Another approach is to pump the bulk material with a high energy pump laser beam. However, bulk dispersion is difficult to achieve to the desired level, and thus the bandwidth of supercontinuum is far less extended than that of microstructured fiber. Recently, by means of ultra-wideband quasi-phase matching scheme, a feasible way for manufacturing high-performance super-continuous white light laser with higher energy (more than 100J per pulse), wider bandwidth and flatter spectral profile is explored by deeply designing second-order nonlinearity and third-order nonlinearity synergistic effect in a single chirped periodically poled lithium niobate nonlinear crystal or cascaded optical module. However, these techniques face unavoidable challenges in accommodating more powerful input pulses due to limitations such as optical damage and laser destruction of the bulk solid material.
One common method of increasing the pulse energy of a supercontinuum laser to extremely high levels without photodamage is to inject a high pulse energy femtosecond laser into a long path gas filled hollow core fiber. However, such devices suffer from limitations in terms of spectral bandwidth, spectral flatness, and balanced performance of pulse energy due to the low nonlinear coefficient of noble gases. Meanwhile, the inflatable hollow fiber has some technical problems including large occupied area, complex structure, poor long-term stability, complicated operation and calibration and the like. For these reasons, the natural choice appears to be to use a liquid such as water to produce ultra-wideband supercontinuum laser sources that are long-lived, highly stable and affordable. The liquid can bear high enough pulse energy, so that the common optical damage problem in the solid material is effectively eliminated. However, supercontinuum lasers produced in these liquid media still suffer from drawbacks such as a spectral intensity peak at the pump center wavelength that is much higher than the spectral intensity of the sideband wavelengths, which results in a very low overall output spectral flatness.
Disclosure of Invention
In order to solve the above problems, the present invention provides an apparatus for generating strong white light laser without optical damage, which includes a pump light source, a third-order nonlinear stretcher, and a second harmonic converter. The pumping light source is titanium precious stone femtosecond pulse laser with the center wavelength of 800nm, the pulse width is 50fs, the repetition frequency is 1kHz, the single pulse energy is more than 4mJ, and the high peak power is characterized; the third-order nonlinear stretcher adopts a liquid material-distilled water device, and can generate obvious self-phase modulation and stimulated Raman scattering effects under the action of strong laser, so that super-continuous laser with wide bandwidth and high flatness is generated, and meanwhile, the laser damage and destruction are effectively avoided; the second harmonic converter is a 5% MgO-doped chirped periodic polarized lithium niobate crystal, has a plurality of inverted lattice vector bands with wide bandwidth and high effective nonlinear coefficient, can effectively compensate the phase mismatch amount in the second harmonic nonlinear frequency conversion process within the bandwidth range of 0.7-1.2 mu m pump laser, and realizes the high-efficiency conversion of ultra-wideband second harmonic. Finally, under the drive of the nonlinear cascade device with the second-order nonlinear synergistic effect and the third-order nonlinear synergistic effect, the generation of strong white light laser with high pulse energy, high peak power, wide spectrum coverage and high flatness is realized. The device can bear high enough pulse energy, effectively eliminates the common optical damage problem in solid materials, opens up an effective way for creating a white light laser with long service life, high stability and low price, strong pulse energy, high spectral flatness and ultra wide bandwidth, and can be widely applied to various fields of basic science and high and new technology.
The technical scheme adopted by the invention is as follows: the device for generating strong white light laser without optical damage comprises a pumping light source, a third-order nonlinear stretcher and a second harmonic converter, wherein the pumping light source is titanium precious stone femtosecond pulse laser with the center wavelength of 800nm, the pulse width is 50fs, the repetition frequency is 1kHz, the single pulse energy is more than 4mJ, and the device has the characteristic of high peak power;
the third-order nonlinear stretcher adopts a distilled water device capable of effectively avoiding optical damage and laser damage to liquid materials, and pulses can generate third-order nonlinear self-phase modulation and stimulated Raman scattering effects in the distilled water device, so that third-order nonlinear super-continuous laser with remarkably stretched bandwidth and higher flatness is generated;
the second harmonic converter is a 5% MgO-doped chirped periodic polarized lithium niobate crystal, the periodic structure of the second harmonic converter is changed along the light propagation direction according to the rule of continuous chirping change, and the second harmonic converter has a plurality of inverted lattice vector bands with wide enough bandwidth and high effective nonlinear coefficient, can effectively compensate the phase mismatch amount of the second harmonic nonlinear frequency conversion process within a certain bandwidth range, and realizes ultra-wideband high-efficiency second harmonic generation.
The technical scheme is further improved, the third-order nonlinear stretcher is a distilled water device with a light transmission length of 40mm, the distilled water containing device is a fused quartz cuvette, each wall thickness of the cuvette is 1.5mm, the cuvette is placed on a translation table, the platform can be moved to change the spot size of an incident light beam at the center of the cuvette, and the effective modulation of the supercontinuum output range and the spectral flatness can be realized through effective adjustment of pump input energy and the spot diameter of the incident laser.
A further improvement to the above scheme is to use water as the third order nonlinear stretcher.
A further improvement of the scheme is that the second harmonic converter consists of a chirped periodically poled lithium niobate crystal doped with 5% MgO, and the periodic structure of the crystal is represented by the formula Λ (z) =Λ 0 /[1+(D g Λ 0 z/2π)]Wherein z represents the position coordinate in the z direction corresponding to a cell, the position coordinate being the coordinate at the start of the cell, the z direction being the light propagation direction, wherein Λ 0 Polarization period D required for frequency multiplication process corresponding to center wavelength of pumping laser light source g Indicating the degree of chirp.
The scheme is further improved in that the polarization period of the 5% MgO doped chirped periodically poled lithium niobate crystal is 12-14 mu m, the negative domain length is 4 mu m, the total length of the crystal is 20mm, and the thickness is 1mm.
The scheme is further improved in that the numerical combination of the polarization period, the chirp degree and the nonlinear crystal length of the 5% MgO doped chirped periodic polarization lithium niobate crystal enables the inverted lattice vector of the nonlinear laser crystal to be presented as a plurality of broadband inverted lattice vector bands distributed at different positions, has enough quasi-phase matching working bandwidth, and can realize high-efficiency conversion of the second harmonic wave covering the 0.7-1.2 mu m broadband pumping laser.
The scheme is further improved in that the pumping light source is a middle infrared femtosecond pulse laser with the central wavelength of 800nm (the output wavelength range of 10dB bandwidth is 776-832 nm), the repetition frequency is 1kHz, the flat single pulse energy is more than 4mJ and the pulse width is 50fs, and the pumping light source has the characteristics of short pulse width, high energy, good light spot quality and the like.
The scheme is further improved in that the third-order nonlinear stretcher adopts a liquid material-distilled water device capable of effectively avoiding optical damage and laser damage, and a clear way is provided for amplifying the pumping energy of the titanium sapphire femtosecond laser to 4 mJ. The pulses can undergo significant self-phase modulation and stimulated raman scattering effects in this device, producing a supercontinuum laser with significantly broader bandwidth and higher flatness. The bandwidth of the pump light source is expanded from the initial 776-832nm to the level of 478-913nm (10 dB broadband), so that more frequency components can participate in the frequency multiplication conversion process of the second harmonic converter.
The scheme is further improved that the distilled water liquid material in the three-stage nonlinear stretcher has a light transmission length of 40mm, and the distilled water containing device is a fused quartz cuvette with a size of 40mm multiplied by 30mm. Each wall thickness of the cuvette was 1.5mm and the upper surface was open. At the same time, the cuvette is placed on a translation stage that can be moved to change the spot size of the incident beam at the center of the cuvette. By effectively adjusting the pump input energy and the incident laser spot diameter, the effective modulation of the supercontinuum pump spectral output range and the spectral flatness can be realized.
A further improvement of the scheme is that the second harmonic converter consists of a chirped periodically poled lithium niobate crystal doped with 5% MgO, and the periodic structure of the crystal is represented by the formula Λ (z) =Λ 0 /[1+(D g Λ 0 z/2π)]Wherein z represents the position coordinate in the z direction corresponding to a cell, the position coordinate being the coordinate at the start of the cell, the z direction being the light propagation direction, wherein Λ 0 Polarization period D required for frequency multiplication process corresponding to center wavelength of pumping laser light source g Indicating the degree of chirp.
A further improvement of the scheme is that the polarization period of the 5% MgO doped chirped periodically poled lithium niobate crystal is 12-14 mu m, the negative domain length is 4 mu m of fixed length, the total length of the crystal is 20mm, and the thickness is 1mm.
The scheme is further improved in that the numerical combination of the polarization period, the chirp degree and the nonlinear crystal length of the 5% MgO doped chirped periodic polarization lithium niobate crystal design enables the inverted lattice vector of the nonlinear laser crystal to be presented as a plurality of broadband inverted lattice vector bands distributed at different positions, the enough quasi-phase matching working bandwidth is provided, and the high-efficiency conversion of the second harmonic wave covering the pumping laser range of 0.7-1.2 mu m can be realized.
The scheme is further improved into a device for generating strong white light laser without optical damage, the whole nonlinear cascading device is a simple, stable and expandable nonlinear cascading module which is formed by water and self-developed chirped structure lithium niobate crystals and driven by titanium precious stone femtosecond laser with pulse energy of up to 4mJ, wherein the chirped structure lithium niobate crystals are immersed in distilled water with a light transmission length of 40mm.
The device for generating strong white light laser without optical damage is further improved by utilizing high-peak-power titanium gemstone femtosecond pump laser, a third-order nonlinear stretching device (water) with obvious spectrum stretching effect and a second-order nonlinear frequency conversion device (chirped periodic polarization lithium niobate crystal) supporting ultra-wideband second harmonic generation, realizing the third-order nonlinear self-phase modulation spectrum stretching process of the pump laser, the first-order and second-order stimulated Raman scattering effect of the water and the efficient second-order nonlinear frequency up-conversion process, and the synergy and the mutual winding effect of the three physical processes make important contribution to realizing ultra-wideband second harmonic generation, and finally realizing the generation of visible-near infrared band ultra-wideband and strong pulse white light laser with high spectrum flatness (10 dB bandwidth 413-907 nm) and large pulse energy (0.6 mJ per pulse).
The beneficial effects of the invention are as follows:
1. the scheme of the invention utilizes water as a third-order nonlinear spectrum broadening medium, provides a clear path for generating super-continuous laser under the high-energy pumping condition, and can effectively avoid the problems of common optical damage, laser damage and the like in solid materials. In addition, water also shows very outstanding first-order and second-order stimulated Raman scattering effect, and a considerable shoulder is generated in the short wavelength range of pure water and the lithium niobate crystal cascade module with the water-chirp structure, so that an economic and effective technical approach is provided for the generation of high-energy, high-stability and high-flatness third-order nonlinear supercontinuum laser.
2. The device of the invention utilizes a simple, steady and extensible nonlinear cascade structure composed of water and lithium niobate crystals with chirp structures which are independently developed, and can finally realize the generation of the high-flatness and strong-pulse white light laser with single pulse energy of 0.6mJ and 10dB bandwidth coverage of 413-907nm through the second-order and third-order nonlinear synergistic effects.
3. The three-order nonlinear stretcher has the advantages of easy acquisition, low price and no optical damage.
4. The nonlinear crystal has the advantages of controllable structure, easy preparation and flexible design.
5. The nonlinear cascade device has the advantages of simple optical path, easy tuning and wide adaptability.
6. The nonlinear cascading device is suitable for generating high-energy ultra-wideband high-pulse white light laser with long service life, high stability and low price, and has flat spectrum, and optical damage and laser damage can be effectively avoided.
Drawings
FIG. 1 is a diagram of an experimental apparatus for generating an optically clear intense white light laser according to one embodiment of the present invention;
FIG. 2 is a graph showing a supercontinuum profile generated at different laser incident energies using water as a third order nonlinear stretching medium in one embodiment of the present invention;
fig. 3 is a structural design diagram of a chirped periodically poled lithium niobate crystal according to an embodiment of the present invention:
(a) Microscopic images of the surface of a typical chirped periodically poled lithium niobate crystal sample;
(b) Is a high-power view of a chirped structure lithium niobate crystal;
(c) A prepared chirped structure lithium niobate crystal sample;
(d) The method is characterized by comprising the steps of designing a chirped structure lithium niobate crystal inverted lattice vector distribution diagram, wherein the ordinate is an effective nonlinear coefficient, and the abscissa is a numerical value of an inverted lattice vector;
fig. 4 is a spectrum distribution diagram of a high-flatness visible-near infrared band intense pulse white light laser without optical damage generated by a nonlinear cascade device of a water-chirped periodically poled lithium niobate crystal according to an embodiment of the present invention using the synergistic effect of second-order and third-order nonlinear effects.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
As shown in fig. 1 to 4, in one embodiment of the present invention, a nonlinear cascade apparatus for generating strong white light laser without optical damage is provided, which includes a pump light source, a third-order nonlinear stretcher, and a second harmonic converter. The pumping light source is a titanium gemstone femtosecond pulse laser system with the center wavelength of 800 nm; the third-order nonlinear stretcher is a liquid material-distilled water device capable of generating obvious third-order nonlinear effect under the action of strong laser, and generates obvious third-order self-phase modulation stretching effect and stimulated Raman scattering effect under the action of high-peak power pumping laser, and more uniform frequency components are started and stimulated to participate in the second-order nonlinear frequency conversion process of the next stage; the second harmonic converter is a chirp periodic polarization lithium niobate crystal doped with 5% MgO, has a plurality of broadband-adjustable inverted lattice vector bands with high effective nonlinear coefficients, can effectively compensate the phase mismatch amount in the second harmonic nonlinear frequency conversion process within the bandwidth range of 0.7-1.2 mu m pump laser, and realizes the generation of high-efficiency ultra-wideband second harmonic. Fig. 1 shows an experimental device diagram for generating a visible-near infrared band strong pulse white light laser with no optical damage and high flatness under the synergistic effect of three modules of a pump light source, a third-order nonlinear stretcher and a second harmonic converter in the embodiment. The input femtosecond laser system is a titanium sapphire chirped pulse amplification laser system, the center wavelength is 800nm, the pulse duration is 50fs, the repetition frequency is 1kHz, the maximum pulse energy can reach 4mJ, and the power of the laser pulse can be adjusted through an adjustable attenuator. The sample is a cascade water-chirped periodically poled lithium niobate crystal module, the chirped periodically poled lithium niobate crystal is immersed in distilled water, the distilled water is contained in a fused quartz cuvette, and the light transmission length is 40mm. Meanwhile, the cuvette is placed on a translation platform, and the size of an incident light beam at the center of the cuvette can be changed by the movable platform. In this embodiment, the first stage ultra wideband laser source is generated by focusing pump laser light through an f=100 mm lens into a distilled water device with a light transmission length of 40mm, and the spot focus is located 20mm behind the front wall of the cuvette filled with water. Then, the supercontinuum generated from water is used as a driving light source for the continuous broadband second harmonic range in the chirped periodic polarized lithium niobate crystal sample, further expands the spectrum short wave band, and finally generates bright, ultra-broadband and ultra-flat supercontinuum white light laser.
In the embodiment, water is used as a third-order nonlinear spectrum broadening medium instead of a common solid material, so that a clear way is provided for amplifying the pumping energy of the titanium sapphire femtosecond laser to 4mJ, and optical damage is effectively avoided. In addition, water also exhibits very pronounced first and second order stimulated raman scattering effects, producing considerable shoulders in the short wavelength range of the third order nonlinear supercontinuum. Fig. 2 shows supercontinuum output spectra of pure water produced at different input pulse energies in this example. The supercontinuum contains a range of visible near infrared bands at pump pulse energies of 1.75, 2, 3.5 and 4mJ, with 10dB bandwidths covering 633-890 nm, 510-903 nm, 487-905 nm and 478-913nm, respectively. The supercontinuum stretching amplitude is positively correlated with the power density of the pump pulse, so that a larger spectrum stretching effect is excited, and a supercontinuum which is an order of magnitude wider than the pump femtosecond laser is generated.
In this embodiment, the second harmonic converter adopts a chirped nonlinear lithium niobate crystal with a periodic structure exhibiting a chirped change along the light propagation direction, and from the practical requirement, a frequency multiplication process corresponding to a proper pumping light wavelength is selected to determine a required crystal polarization period Λ 0 Finding the appropriate chirp degree and sample length L. According to the formula Λ (z) =Λ 0 /[1+(D g Λ 0 z/2π)]To determine the length Λ (z) of each cell of the crystal in the z direction, wherein z is the starting position coordinate of the corresponding domain structure in the z direction, D g Is chirp degree. In this embodiment, the polarization period of the chirped nonlinear lithium niobate crystal is 12-14 μm, and the degree of chirping D g Is 5 μm -2 The crystal length was 20mm and the crystal thickness was 1mm. Fig. 3 (a) - (c) show schematic geometric diagrams of chirped lithium niobate crystals designed in this example for ultra-wideband second harmonic generation. In this embodiment, the inverted lattice vector distribution of the chirped nonlinear photonic crystal with the structure and parameters is 3 broadband inverted lattice vector bands, which are respectively located in the B1 band [0,1.08 ]]B2 tape [1.08,2.1 ]]B3 tape [2.1,3.14 ]]The units are all μm-1, and are shown in FIG. 3 (d). These haveThe inverted lattice vector band of high effective nonlinear coefficients can provide effective phase compensation for second harmonic nonlinear frequency conversion processes as wide as the 0.7-1.2 μm pump laser range.
Fig. 4 shows supercontinuum distribution diagrams generated by the water-chirped periodically poled lithium niobate crystal cascade module of this embodiment under different input pulse energy and incident spot diameter conditions, wherein in the case that the input pulse energy is 4mJ and the incident spot diameter of the front end of the chirped lithium niobate crystal is 1.5mm, an optimal white light output laser (as shown by the blue curve in fig. 4) covering the visible to near infrared band (10 dB bandwidth 413-907 nm) with single pulse energy reaching 0.6mJ can be generated. Obviously, the nonlinear cascade device successfully creates two necessary conditions for realizing the visible-near infrared band coverage strong pulse white light laser without optical damage by utilizing a third-order nonlinear widening technology and a second-order nonlinear frequency conversion: firstly, water is used as a third-order nonlinear stretching medium, which can bear high enough pulse energy, and the obvious third-order self-phase modulation stretching effect and stimulated Raman scattering effect of the water under the condition of strong pulse energy pumping laser create a supercontinuum laser source condition with high energy and higher flatness, excite and drive more uniform frequency components to participate in the second-order nonlinear frequency conversion process of the next stage, well solve the problem that the pumping laser input bandwidth is not wide enough in the supercontinuum laser generation technology, and well eliminate the common optical damage and laser damage problems in solid materials. And secondly, the specially designed chirped nonlinear lithium niobate crystal comprises a plurality of efficient and wide enough inverted lattice vector bands to compensate the phase mismatch problem of the interaction wave, so that the efficient conversion of the second harmonic of the broadband pumping laser range can be realized, and the problem of insufficient working bandwidth of quasi-phase matching is greatly solved. Finally, under the drive of the nonlinear cascade system with the second-order nonlinear synergistic effect and the third-order nonlinear synergistic effect, the generation of visible-near infrared strong pulse white light laser with long service life, high stability, low price, high pulse energy (0.6 mJ), high peak power, wide spectrum coverage and high flatness (10 dB bandwidth reaches 413-907 nm) can be finally realized.
The foregoing examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (6)
1. A device for generating a strong white light laser without optical damage, characterized by: the laser comprises a pumping light source, a third-order nonlinear stretcher and a second harmonic converter, wherein the pumping light source is titanium precious stone femtosecond pulse laser with the center wavelength of 800nm, the pulse width is 50fs, the repetition frequency is 1kHz, the single pulse energy is more than 4mJ, and the laser has the characteristic of high peak power;
the third-order nonlinear stretcher adopts a distilled water device capable of effectively avoiding optical damage and laser damage to liquid materials, and pulses can generate third-order nonlinear self-phase modulation and stimulated Raman scattering effects in the distilled water device, so that third-order nonlinear super-continuous laser with remarkably stretched bandwidth and higher flatness is generated;
the second harmonic converter is a 5% MgO doped chirped periodic polarized lithium niobate crystal, the periodic structure of the second harmonic converter is changed along the light propagation direction according to the rule of continuous chirping change, and the second harmonic converter has a plurality of inverted lattice vector bands with wide enough bandwidth and high effective nonlinear coefficient, can effectively compensate the phase mismatch amount of the second harmonic nonlinear frequency conversion process within a certain bandwidth range, and realizes ultra-wideband high-efficiency second harmonic generation.
2. The apparatus for generating optically clear intense white light laser light of claim 1 wherein: the third-order nonlinear stretcher is a distilled water device with a light transmission length of 40mm, the distilled water containing device is a fused quartz cuvette, each wall thickness of the cuvette is 1.5mm, the cuvette is placed on a translation table, the table can be moved to change the spot size of an incident light beam at the center of the cuvette, and the effective modulation of the supercontinuum output range and the spectral flatness can be realized through effective adjustment of the pump input energy and the incident laser spot diameter.
3. The apparatus for generating optically clear intense white light laser of claim 2 wherein: water is used as a third order nonlinear stretcher.
4. The apparatus for generating optically clear intense white light laser light of claim 1 wherein: the second harmonic converter consists of a chirped periodically poled lithium niobate crystal doped with 5% MgO, and the periodic structure of the crystal is represented by the formula Λ (z) =Λ 0 /[1+(D g Λ 0 z/2π)]Wherein z represents the position coordinate in the z direction corresponding to a cell, the position coordinate being the coordinate at the start of the cell, the z direction being the light propagation direction, wherein Λ 0 Polarization period D required for frequency multiplication process corresponding to center wavelength of pumping laser light source g Indicating the degree of chirp.
5. The apparatus for generating optically clear intense white light laser of claim 4 wherein: the polarization period of the 5% MgO doped chirped periodically polarized lithium niobate crystal is 12-14 mu m, the negative domain length is 4 mu m of fixed length, the total length of the crystal is 20mm, and the thickness is 1mm.
6. The apparatus for generating optically clear intense white light laser of claim 5 wherein: the combination of the polarization period, the chirp degree and the nonlinear crystal length of the 5% MgO doped chirped periodic polarization lithium niobate crystal enables the inverted lattice vector of the nonlinear laser crystal to be a plurality of broadband inverted lattice vector bands distributed at different positions, has enough quasi-phase matching working bandwidth, and can realize the high-efficiency conversion of the second harmonic wave covering the 0.7-1.2 mu m broadband pumping laser.
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