CN115986536A - A method and laser for obtaining mid-infrared ultrashort pulse laser - Google Patents

Abstract

The embodiment of the application discloses a method for obtaining mid-infrared ultrashort pulse laser and a laser, wherein the laser comprises: the near-infrared ultra-short pulse fiber laser is used for outputting first ultra-short pulse laser; the first-stage optical fiber amplifier is used for processing the first ultrashort pulse laser and outputting second ultrashort pulse laser, wherein the power of the second ultrashort pulse laser is greater than that of the first ultrashort pulse laser; the high nonlinear fiber is used for processing the second ultrashort pulse laser and outputting a third ultrashort pulse laser; and the second-stage optical fiber amplifier is used for processing the third ultrashort pulse laser and outputting a fourth ultrashort pulse laser. The embodiment of the application can improve the output power of the intermediate infrared ultrashort pulse laser.

Description

A method and laser for obtaining mid-infrared ultrashort pulse laser

technical field

The present application relates to optical signal processing technology, which is applied in the laser field, and in particular to a method and a laser for obtaining mid-infrared ultrashort pulse laser.

Background technique

Mid-infrared ultrashort pulse laser is widely used in communication, remote sensing, molecular spectroscopy, supercontinuum light source, material processing, laser hand and biomedicine because its band is located in the atmospheric transmission window, thermal radiation energy concentration band and water molecule absorption band. field. At present, ultrafast oscillators or amplifiers in mid-infrared ultrashort pulse lasers often contain free-space optical components, and the instability of free-space optical components will affect the quality of the output mid-infrared ultrashort pulse laser, especially the mid-infrared ultrashort pulse laser. The power of ultrashort pulse laser.

Therefore, how to increase the output power of the mid-infrared ultrashort pulse laser is a technical problem to be solved urgently by those skilled in the art.

Contents of the invention

The embodiment of the present application discloses a method and a laser for obtaining mid-infrared ultrashort pulse laser, which are used to increase the output power of the mid-infrared ultrashort pulse laser.

In the first aspect, the embodiment of the present application provides a mid-infrared ultrashort pulse laser, the laser includes

A near-infrared ultrashort pulse fiber laser is used to output a first ultrashort pulse laser, wherein the central wavelength of the first ultrashort pulse laser is in the near-infrared band, that is, the first ultrashort pulse laser is used as a near-infrared seed light source;

The first-stage fiber amplifier is used to process the first ultrashort pulse laser and output the second ultrashort pulse laser, wherein the power of the second ultrashort pulse laser is greater than the power of the first ultrashort pulse laser, There is a first optical soliton in the second ultrashort pulse laser, the central wavelength of the first optical soliton is greater than the central wavelength of the first ultrashort pulse laser, and the central wavelength of the first optical soliton is in the near-infrared band , that is, the first-stage fiber amplifier amplifies the power of the first ultrashort pulse laser, and red-shifts the central wavelength of the first ultrashort pulse laser, and outputs the second ultrashort pulse laser;

A highly nonlinear optical fiber, used to process the second ultrashort pulse laser and output a third ultrashort pulse laser, wherein there is a second optical soliton in the third ultrashort pulse laser, and the second optical soliton The central wavelength of the first optical soliton is greater than the central wavelength of the first optical soliton, and the central wavelength of the second optical soliton is in the mid-infrared band, that is, the high nonlinear fiber further redshifts the central wavelength of the second ultrashort pulse laser, and outputs the third Ultrashort pulse laser;

The second-stage fiber amplifier is used to process the third ultrashort pulse laser and output a fourth ultrashort pulse laser, wherein the output power of the fourth ultrashort pulse laser is greater than that of the second ultrashort pulse laser and the power of the third ultrashort pulse laser, there is a third optical soliton in the fourth ultrashort pulse laser, and the central wavelength of the third optical soliton is greater than or equal to the central wavelength of the second optical soliton , the second-stage fiber amplifier does not include free-space optical elements, that is, the second-stage fiber amplifier amplifies the power of the third ultrashort pulse laser (in combination with actual needs, the center wavelength of the third ultrashort pulse laser can also be further red-shifted ), outputting the fourth ultrashort pulse laser.

That is to say, the above-mentioned mid-infrared ultrashort pulse laser performs a secondary wavelength redshift on the near-infrared seed light source through the first-stage fiber amplifier and the high nonlinear fiber respectively, and respectively passes through the first-stage fiber amplifier and the second-stage fiber amplifier The output power of the mid-infrared ultrashort pulse laser can be improved by performing secondary power amplification on the near-infrared seed light source.

It should be noted that the inventors have found in a large number of practices that the ultrafast oscillators or amplifiers in traditional mid-infrared lasers often contain free-space optical elements, and the instability of free-space optical elements will affect the output mid-infrared ultrashort The quality of the pulsed laser, while the second-stage fiber amplifier in this application does not contain free-space optical elements (such as commonly used lenses and dichroic mirrors), it can avoid the mid-infrared ultrashort pulse laser caused by the instability of the optical space device The power is reduced to ensure stable output of mid-infrared ultrashort pulse laser while increasing the power of mid-infrared ultrashort pulse laser.

Combining with the first aspect, in a possible implementation:

The first-stage optical fiber amplifier includes a first pump laser, a near-infrared beam combiner and a first rare-earth ion-doped silica fiber, wherein the first pump laser is used to generate the first pump light, and the near-infrared A beam combiner is used to couple the first ultrashort pulse laser and the first pump light to the first rare earth ion-doped silica fiber, and the first rare earth ion-doped silica fiber is used to The short pulse laser and the first pump light output the second ultrashort pulse laser;

And/or, the second-stage fiber amplifier includes a second pump laser, a mid-infrared beam combiner, and a rare-earth ion-doped fluoride fiber, wherein the second pump laser is used to generate a second pump light, so The center wavelength of the second pump light is greater than the center wavelength of the first pump light, and the mid-infrared beam combiner is used to couple the third ultrashort pulse laser and the second pump light to the A rare-earth ion-doped fluoride optical fiber, the rare-earth ion-doped fluoride optical fiber is used to output the fourth ultrashort pulse laser based on the third ultrashort pulse laser and the second pumping light source.

In the above-mentioned mid-infrared ultrashort pulse laser, the first-stage fiber amplifier couples the first pump light and the first ultrashort pulse laser through a near-infrared beam combiner, and then couples the coupled near-infrared laser through a rare-earth ion-doped quartz fiber. The Raman gain effect (that is, the Raman soliton self-frequency shift effect) can amplify the power of the first ultrashort pulse laser and red-shift the central wavelength, and output the second ultrashort pulse laser with optical solitons. The second-stage optical fiber amplifier couples the second pump light and the third ultrashort pulse laser through the mid-infrared beam combiner, and then passes through the Raman gain effect of the coupled mid-infrared laser through the rare earth ion fluoride fiber (ie, pulling Mann soliton self-frequency shift effect) can amplify the power of the third ultrashort pulse laser (in combination with actual needs, the central wavelength can be further red-shifted), and output the fourth ultrashort pulse laser with optical solitons.

It should be noted that the mid-infrared ultrashort pulse laser generated by the Raman soliton self-frequency shift effect has one optical soliton or multiple optical solitons with continuous spectrum, and the central wavelengths of multiple optical solitons are different.

In combination with the first aspect, or any of the above possible implementations of the first aspect, in another possible implementation:

The first pump laser and/or the second pump laser are used to adjust the power of the generated pump light, so as to control the central wavelength of the fourth ultrashort pulse laser.

The above-mentioned mid-infrared ultrashort pulse laser can adjust the central wavelength of the fourth ultrashort pulse laser by adjusting the power of the pump light, that is to say, the fourth ultrashort pulse laser is a wavelength-tunable mid-infrared ultrashort pulse laser.

Combining the first aspect, or any of the above-mentioned possible implementations of the first aspect, in another possible implementation:

The laser output end of the near-infrared ultrashort pulse fiber laser is connected to the laser input end of the first-stage fiber amplifier through a first polarization-independent isolator, wherein the first polarization-independent isolator is used to isolate the first-stage Reflected light generated by the fiber amplifier;

The laser output end of the first-stage fiber amplifier is connected to the laser input end of the high nonlinear optical fiber through the first stripper, the second polarization-independent isolator and the quartz fiber in sequence, wherein the second polarization-independent isolator is used for isolating the reflected light generated by the highly nonlinear fiber, the first stripper is used to filter out the first pump light in the second ultrashort pulse laser, and the silica fiber is used to reduce the Fiber loss produced when connecting the second polarization-independent isolator;

The laser output end of the highly nonlinear optical fiber is connected to the laser input end of the second-stage fiber amplifier;

The laser output end of the second-stage fiber amplifier is connected to a second power stripper, and the second stripper is used to filter out the second pump light in the fourth ultrashort pulse laser.

Considering that the reflected light generated by the first-stage fiber amplifier will affect the stability of the near-infrared ultrashort pulse fiber laser, the first polarization-independent isolator is set; considering that the absorption of the pump light in the first-stage fiber amplifier is difficult to reach 100 %, the second ultrashort pulse laser contains the unabsorbed first pump light, so the first stripper is set to filter the first pump light to prevent the temperature of subsequent optical fiber devices from being too high; The reflected light of the first-stage fiber amplifier will affect the stability of the first-stage fiber amplifier, so a second polarization-independent isolator is set; considering that the fiber of the first-stage fiber amplifier is different from the material of the high nonlinear fiber, a silica fiber is set to reduce the splicing loss ; Considering that the absorption of the pump light in the second-stage fiber amplifier is difficult to reach 100%, the fourth ultrashort pulse laser contains the second pump light that is not absorbed, so the second stripper is set to filter the second pump light Light is conducive to obtaining mid-infrared ultrashort pulse lasers that meet actual needs.

Therefore, the above-mentioned mid-infrared ultrashort pulse laser can stably increase the output power of the mid-infrared ultrashort pulse laser.

In combination with the first aspect, or any of the above-mentioned possible implementations of the first aspect, in yet another possible implementation, the mid-infrared beam combiner includes the light source output end of the highly nonlinear optical fiber and the The fusing interface of the light source input end of the rare earth ion-doped fluoride optical fiber, the fusing interface and the light source output end of the pumping optical fiber in the second pumping laser are fixed by a solidified material.

In combination with the first aspect, or any of the above-mentioned possible implementations of the first aspect, in another possible implementation, the near-infrared ultrashort pulse fiber laser includes a second rare earth ion-doped silica fiber, wherein the The second rare earth ion-doped quartz fiber is used to generate the first ultrashort pulse laser.

With reference to the first aspect, or any of the foregoing possible implementation manners of the first aspect, in yet another possible implementation manner, the highly nonlinear optical fiber includes a highly nonlinear fluoride optical fiber.

Compared with other highly nonlinear fibers, such as tellurate fibers and chalcogenide fibers, fluoride fibers have mature manufacturing technology and have a large nonlinear refractive index and anomalous dispersion, and the Raman soliton self-frequency shift effect is more obvious. Therefore, using The highly nonlinear fluoride fiber can increase the red shift range of the second ultrashort pulse laser wavelength, which is conducive to the subsequent output of mid-infrared ultrashort pulse laser that meets the actual wavelength requirements.

In the second aspect, the embodiment of the present application provides a method for obtaining mid-infrared ultrashort pulse laser, which is applied to a mid-infrared ultrashort pulse laser, and the laser includes a near-infrared ultrashort pulse fiber laser, a first-stage fiber amplifier, a high A nonlinear optical fiber and a second stage optical fiber amplifier, the method comprising:

Outputting a first ultrashort pulse laser through a near-infrared ultrashort pulse fiber laser, wherein the central wavelength of the first ultrashort pulse laser is in the near-infrared band;

The first ultrashort pulse laser is processed by the first-stage fiber amplifier, and the second ultrashort pulse laser is output, wherein the power of the second ultrashort pulse laser is greater than the power of the first ultrashort pulse laser, and the There is a first optical soliton in the second ultrashort pulse laser, the central wavelength of the first optical soliton is greater than the central wavelength of the first ultrashort pulse laser, and the central wavelength of the first optical soliton is in the near-infrared band;

The second ultrashort pulse laser is processed through a highly nonlinear optical fiber to output a third ultrashort pulse laser, wherein there is a second optical soliton in the third ultrashort pulse laser, and the center of the second optical soliton The wavelength is greater than the central wavelength of the first optical soliton, and the central wavelength of the second optical soliton is in the mid-infrared band;

The third ultrashort pulse laser is processed by a second-stage fiber amplifier to output a fourth ultrashort pulse laser, wherein the output power of the fourth ultrashort pulse laser is greater than the power of the second ultrashort pulse laser and the power of the third ultrashort pulse laser, there is a third optical soliton in the fourth ultrashort pulse laser, and the central wavelength of the third optical soliton is greater than or equal to the central wavelength of the second optical soliton, so The second-stage fiber amplifier described above does not contain free-space optics.

With reference to the second aspect, in a possible implementation manner, the first-stage fiber amplifier includes a first pump laser, a near-infrared beam combiner, and a first rare-earth ion-doped silica fiber; the first-stage fiber amplifier Process the first ultrashort pulse laser and output the second ultrashort pulse laser, including:

generating first pump light by the first pump laser;

coupling the first ultrashort pulse laser and the first pump light to the first rare earth ion-doped silica fiber through the near-infrared beam combiner;

outputting the second ultrashort pulse laser based on the first ultrashort pulse laser and the first pumping light through the first rare earth ion-doped silica fiber.

In combination with the second aspect, or any of the above-mentioned possible implementations of the second aspect, in another possible implementation, the second-stage fiber amplifier includes a second pump laser, a mid-infrared beam combiner, and a doped Rare earth ion fluoride optical fiber; the third ultrashort pulse laser is processed by the second-stage fiber amplifier, and the fourth ultrashort pulse laser is output, including:

generating a second pump light by the second pump laser, wherein the center wavelength of the second pump light is greater than the center wavelength of the first pump light;

coupling the third ultrashort pulse laser light and the second pump light to the rare earth ion-doped fluoride optical fiber through the mid-infrared beam combiner;

Outputting the fourth ultrashort pulse laser based on the third ultrashort pulse laser and the second pumping light source through the rare earth ion-doped fluoride fiber.

In combination with the second aspect, or any of the above possible implementation manners of the second aspect, in another possible implementation manner, the method further includes:

The first pump laser and/or the second pump laser are used to adjust the power of the generated pump light, so as to control the central wavelength of the fourth ultrashort pulse laser.

In combination with the second aspect, or any of the above-mentioned possible implementations of the second aspect, in another possible implementation:

The laser output end of the near-infrared ultrashort pulse fiber laser is connected to the laser input end of the first-stage fiber amplifier through a first polarization-independent isolator;

The laser output end of the first-stage fiber amplifier is sequentially connected to the laser input end of the high nonlinear optical fiber through the first stripper, the second polarization-independent isolator and the quartz fiber;

The laser output end of the highly nonlinear optical fiber is connected to the laser input end of the second-stage fiber amplifier;

The laser output end of the second-stage fiber amplifier is connected to a second power stripper.

In combination with the second aspect, or any of the above possible implementation manners of the second aspect, in another possible implementation manner, the method further includes:

isolating reflected light generated by the first-stage fiber amplifier through the first polarization-independent isolator;

The second polarization-independent isolator is used to isolate the reflected light generated by the highly nonlinear optical fiber;

filtering out the first pump light in the second ultrashort pulse laser through the first stripper;

connecting the second polarization-independent isolator and the highly nonlinear optical fiber through the silica optical fiber;

The second pumping light in the fourth ultrashort pulse laser is filtered out by the second stripper.

In combination with the second aspect, or any of the above-mentioned possible implementations of the second aspect, in another possible implementation, the mid-infrared beam combiner includes the light source output end of the highly nonlinear optical fiber and the The fusing interface of the light source input end of the rare earth ion-doped fluoride optical fiber, the fusing interface and the light source output end of the pumping optical fiber in the second pumping laser are fixed by a solidified material.

In combination with the second aspect, or any of the above-mentioned possible implementations of the second aspect, in yet another possible implementation, the near-infrared ultrashort pulse fiber laser includes a second rare earth ion-doped silica fiber, and the through The near-infrared ultrashort pulse fiber laser outputting the first ultrashort pulse laser includes outputting the first ultrashort pulse laser through the second rare earth ion-doped quartz fiber.

With reference to the second aspect, or any of the foregoing possible implementation manners of the second aspect, in yet another possible implementation manner, the highly nonlinear optical fiber includes a highly nonlinear fluoride optical fiber.

For the beneficial effects of the technical method provided in the second aspect of the present application, reference can be made to the beneficial effects of the mid-infrared ultrashort pulse laser provided in the first aspect, which will not be repeated here.

Description of drawings

The following will briefly introduce the drawings that need to be used in the description of the embodiments of the present application.

FIG. 1 is a schematic structural diagram of a mid-infrared ultrashort pulse laser 10 provided in an embodiment of the present application;

Fig. 2 is the spectrogram of a kind of second ultrashort pulse laser provided by the embodiment of the present application;

Fig. 3 is a spectrum diagram of a third ultrashort pulse laser provided by the embodiment of the present application;

FIG. 4 is a spectrum diagram of a fourth ultrashort pulse laser provided by an embodiment of the present application;

FIG. 5 is a schematic structural diagram of a mid-infrared ultrashort pulse laser 50 provided in an embodiment of the present application.

Detailed ways

For ease of understanding, some terms used in the embodiments of the present application will be explained first.

1. Ultrashort pulse: a light pulse whose duration is on the order of picoseconds (10 ^-12 seconds) or shorter.

2. Optical soliton: an optical pulse that does not change in time-domain waveform and spectrum when transmitted in an optical fiber.

3. Soliton self-frequency shift (SSFS) effect: when the ultrashort pulse is transmitted in the anomalous dispersion region in the fiber, due to Raman scattering, the high frequency component in the ultrashort pulse is used as pump light to transfer energy Given the low frequency component, the pulse spectrum as a whole moves to the long wavelength and transmits in the shape of the fundamental optical soliton.

The above explanations of technical terms can be applied to the following embodiments.

Embodiments of the present application will be described in detail below in conjunction with the accompanying drawings.

Please refer to Fig. 1. Fig. 1 is a schematic structural diagram of a mid-infrared ultrashort pulse laser 10 provided by an embodiment of the present application. The mid-infrared ultrashort pulse laser 10 includes a near-infrared ultrashort pulse fiber laser 101, a first-stage fiber amplifier 102, a highly nonlinear optical fiber 103 and a second-stage optical fiber amplifier 104. Wherein, the laser output end of the near-infrared ultrashort pulse fiber laser 101 is connected with the laser input end of the first-stage optical fiber amplifier 102, and the laser output end of the first-stage optical fiber amplifier 102 is connected with the laser input end of the high nonlinear optical fiber 103, high The laser output end of the nonlinear fiber 103 is connected to the laser input end of the second-stage fiber amplifier 104 . The connection method between each component is optical fiber fusion splicing.

The near-infrared ultrashort pulse fiber laser 101 is used to output the first ultrashort pulse laser, and its laser gain medium is the second rare earth ion-doped silica fiber. The center wavelength of the first ultrashort pulse laser is in the near-infrared band (0.75-2.5 μm), and it is used as a pulse seed light source.

Optionally, the central wavelength of the first ultrashort pulse laser may be 2 μm, or 1.5 μm, or other wavelengths set according to actual needs.

Optionally, the doped rare earth ions may be thulium ions (Tm ³⁺ ), ytterbium ions (Yb ³⁺ ), erbium ions (Er ³⁺ ) and praseodymium (Pr ^{3 +} ) ions. Optionally, when the central wavelength of the first ultrashort pulse laser is 2 μm, the near-infrared ultrashort pulse fiber laser 101 may be a 2 μm mode-locked Tm ^{3+ -doped} fiber laser.

The first-stage fiber amplifier 102 is used for amplifying the power of the first ultrashort pulse laser, and red-shifting the center wavelength of the first ultrashort pulse laser, and outputting the second ultrashort pulse laser. That is to say, the power of the second ultrashort pulse laser is greater than the power of the first ultrashort pulse laser, there is a first optical soliton in the second ultrashort pulse laser, and the central wavelength of the first optical soliton is greater than that of the first ultrashort pulse The central wavelength of the pulsed laser, and the central wavelength of the first optical soliton are in the near-infrared band. The laser gain fiber of the first-stage fiber amplifier 102 may be a first rare earth ion-doped silica fiber.

In an optional embodiment, the first-stage fiber amplifier 102 can process the first ultrashort pulse laser to output the second ultrashort pulse laser by utilizing the SSFS effect. Specifically, the first-stage fiber amplifier 102 includes a first pump laser, a near-infrared beam combiner, and a first rare-earth ion-doped silica fiber. The first pump laser is used to generate the first pump light, and the near-infrared beam combiner is used to couple the first ultrashort pulse laser and the first pump light to the first rare-earth ion-doped silica fiber, and the first rare-earth ion-doped silica fiber as a laser gain medium. When the coupling light of the first ultrashort pulse laser and the first pumping light is transmitted in the first rare earth ion-doped silica fiber, the first ultrashort pulse laser is used as the signal light, and the first pumping light is used as the pumping light, forming a forward direction pump structure. Therefore, in addition to the SSFS effect based on the fiber itself, the first ultrashort pulse laser can also be pumped by the first pump light (the first pump light needs to provide sufficient energy within the wavelength range of the first ultrashort pulse laser. Raman gain). This not only enables the transmission of the first ultrashort pulse laser in the form of optical solitons (also called Raman solitons), but also increases its power and redshifts its central wavelength on the basis of the original wavelength redshift, and outputs the second Ultrashort pulse laser.

For ease of understanding, an example is given below, please refer to FIG. 2 , which is a spectrum diagram of a second ultrashort pulse laser provided in an embodiment of the present application. Spectrum 201-spectrum 206 is the spectrum of the second ultrashort pulse laser under different first pump powers (ie, the power of the first pump light), and the first pump power corresponding to spectrum 201-spectrum 206 changes from low to high. It should be noted that the abscissa corresponding to the spectrum is used to reflect the wavelength of the optical signal (in nanometers, expressed in nm), and the ordinate corresponding to the spectrum is used to reflect the intensity of the optical signal (in decibels, expressed in dB). After testing, the power of the second ultrashort pulse laser corresponding to spectrum 201 is 186 milliwatts (hereinafter expressed in mW), the power of the second ultrashort pulse laser corresponding to spectrum 202 is 356 mW, and the power of the second ultrashort pulse laser corresponding to spectrum 203 The power of the laser is 406mW, the power of the second ultrashort pulse laser corresponding to spectrum 204 is 424mW, the power of the second ultrashort pulse laser corresponding to spectrum 205 is 486mW, and the power of the second ultrashort pulse laser corresponding to spectrum 206 is 738mW . That is, the greater the pumping power of the first pumping light, the greater the output power of the second ultrashort pulse laser.

The wavelength corresponding to the first intensity peak from right to left in the spectrum is taken as the center wavelength of the first optical soliton (that is, the optical soliton with the largest wavelength red shift), and the wavelength corresponding to the second intensity peak is taken as the second optical soliton center wavelength. Taking spectrum 204 as an example, the wavelength corresponding to the first intensity peak from right to left (the ordinate a corresponding to point A) (the abscissa b corresponding to point A) is 2249nm, and the second intensity peak (corresponding to point B is The wavelength corresponding to the ordinate c) (the abscissa d corresponding to point B) is 1950nm, that is, the central wavelength of the first optical soliton (ie the first optical soliton) in the second ultrashort pulse laser is 2249nm, and the second optical soliton The center wavelength is 1950nm. It is not difficult to see that the greater the pumping power of the first pumping light is, the central wavelength of the optical soliton will gradually increase (also called red shift), and the wavelength range of the spectrum will gradually become wider. Therefore, in actual operation, the pumping power of the first pumping light can be adjusted to obtain the second ultrashort pulse laser that meets the actual wavelength or power requirements.

It should be noted that, in the embodiment corresponding to Fig. 2, the central wavelength of the first ultrashort pulse laser can be 2 μm, its power can be 10 mW, and the first pump laser can be a 793nm semiconductor pump laser, that is, the first pump laser The central wavelength of light may be 793nm, and the first rare earth ion doped silica fiber may be a Tm ³⁺ doped silica fiber with a length of 6m.

It should be noted that the first pumping laser includes a first pumping optical fiber, and the first pumping optical fiber is a transmission medium of the first pumping light.

Due to the limitation of the transmission loss of the silica fiber, the redshift range of the soliton self-frequency shift in the near-infrared band is difficult to exceed 2.5 μm. Further, the highly nonlinear optical fiber 103 is used to further redshift the central wavelength of the second ultrashort pulse laser, and output a third ultrashort pulse laser, wherein there are second optical solitons in the third ultrashort pulse laser, and the second optical The central wavelength of the soliton is greater than that of the first optical soliton, and the central wavelength of the second optical soliton is in the mid-infrared band (2.5-25 μm). Optionally, the material of the highly nonlinear optical fiber 103 may be a tellurate optical fiber, a chalcogenide optical fiber, a fluoride optical fiber, and the like.

Compared with the silica fiber, the highly nonlinear optical fiber 103 has a larger nonlinear refractive index and anomalous dispersion. When the second ultrashort pulse laser is transmitted in the highly nonlinear optical fiber 103, its wavelength can be within the fiber gain range based on the SSFS effect. further redshifted. For ease of understanding, an example is given below. Please refer to FIG. 3 . FIG. 3 is a spectrum diagram of a third ultrashort pulse laser provided in an embodiment of the present application.

Spectrum 301-spectrum 305 is the spectrum of the third ultrashort pulse laser under different first pumping powers. The abscissa corresponding to the spectrum is used to reflect the wavelength of the optical signal (in nanometers, expressed in nm), and the vertical axis corresponding to the spectrum The coordinates are used to reflect the strength of the optical signal (in decibels, expressed in dB). The first pump power corresponding to spectrum 301 is 2930mW, the first pump power corresponding to spectrum 302 is 3480mW, the first pump power corresponding to spectrum 303 is 3780mW, and the first pump power corresponding to spectrum 304 is 3990mW. The power of the first pump power corresponding to the spectrum 305 is 4480mW.

The wavelength corresponding to the first intensity peak from right to left in the spectrum is taken as the center wavelength of the first optical soliton (that is, the optical soliton with the largest wavelength red shift), and the wavelength corresponding to the second intensity peak is taken as the second optical soliton center wavelength.

It can be analyzed from the spectrum 303-spectrum 303 that as the first pump power increases from 2930mW to 3780mW, the central wavelength of the first optical soliton (that is, the second optical soliton) in the third ultrashort pulse laser can be continuous from 2300nm Tune to 2800nm. That is, the highly nonlinear fiber 103 can gain optical solitons in the near-infrared band to optical solitons in the mid-infrared band. It can be analyzed from spectrum 304-spectrum 305 that with the further increase of the first pump power, the central wavelength of the first optical soliton in the third ultrashort pulse laser will become smaller instead, which may be the third ultrashort pulse laser The energy of the second soliton increases with the further increase of the first pump power, which affects the energy of the first soliton. Therefore, the gain effect of the highly nonlinear fiber 103 on the second ultrashort pulse laser is also affected by the first pumping power in the first-stage fiber amplifier 102 .

It should be noted that, in the embodiment corresponding to Fig. 3, the first pump laser may be a 793nm multimode semiconductor pump laser, that is, the central wavelength of the first pump light may be 793nm, and there may be The central wavelength is the first optical soliton of 2300nm, and the highly nonlinear fiber 103 may be a highly nonlinear fluoride fiber. The highly nonlinear fluoride optical fiber may be a fluoride optical fiber with a length of 5 m, a core diameter of 6.5 μm and a cladding diameter of 125 μm.

In addition, when the second ultrashort pulse laser is transmitted in the high nonlinear fiber 103, no additional pump energy is absorbed. Considering the transmission loss of the high nonlinear fiber 103, the third ultrashort pulse laser output by the high nonlinear fiber 103 Compared with the power of the second ultrashort pulse laser, there will be a certain loss. Based on this, in order to output high-power mid-infrared ultrashort pulse laser, the second-stage fiber amplifier 104 further processes the third ultrashort pulse laser.

The second-stage fiber amplifier 104 is used to amplify the power of the third ultrashort pulse laser (the central wavelength of the third ultrashort pulse laser can be further red-shifted according to actual needs), and output the fourth ultrashort pulse laser. Wherein, the output power of the fourth ultrashort pulse laser is greater than the power of the second ultrashort pulse laser and the power of the third ultrashort pulse laser, there is a third optical soliton in the fourth ultrashort pulse laser, and the third optical The central wavelength of the soliton is greater than or equal to the central wavelength of the second optical soliton, and the second-stage fiber amplifier 104 does not include free-space optical elements. The laser gain medium of the second-stage fiber amplifier 104 is a rare earth ion-doped fluoride fiber.

Optionally, the free-space optical element may be some free-space optical element for coupling signal light and pump light, such as a lens and a dichroic mirror.

In an optional embodiment, the second-stage fiber amplifier 104 can use the SSFS effect to process the third ultrashort pulse laser to output the fourth ultrashort pulse laser. Specifically, the second-stage fiber amplifier 104 includes a second pump Pu lasers, mid-infrared beam combiners, and rare earth ion-doped fluoride optical fibers. Specifically, the second pump laser is used to generate the second pump light, and the mid-infrared beam combiner is used to couple the second ultrashort pulse laser and the second pump light to the rare-earth ion-doped fluoride optical fiber, and the rare-earth ion-doped fluoride Optical fiber is used as laser gain medium. When the coupling light of the third ultrashort pulse laser and the second pumping light is transmitted in the rare earth ion fluoride fiber, the third ultrashort pulse laser is used as the signal light, and the second pumping light is used as the pumping light to form a forward pumping Pu structure. It should be noted that, compared with the first-stage fiber amplifier 102, the energy of the second pump light is greater than that of the first pump light, that is, the central wavelength of the second pump light is greater than that of the first pump light. Therefore, in addition to the SSFS effect based on the fiber itself, the third ultrashort pulse laser can also be pumped by the second pump light (the second pump light needs to provide sufficient pulling power within the wavelength range of the third short pulse laser. Mann gain). This not only allows the third ultrashort pulse laser to continue to transmit in the form of optical solitons (also called Raman solitons), but also increases its power. In addition, according to actual needs, the second-stage fiber amplifier 104 can further red-shift the center wavelength of the third ultrashort pulse laser to output the fourth ultrashort pulse laser.

For ease of understanding, an example is given below, please refer to FIG. 4 , which is a spectrum diagram of a fourth ultrashort pulse laser provided in an embodiment of the present application. Spectrum 401-spectrum 406 is the spectrum of the fourth ultrashort pulse laser under different second pump powers (that is, the power of the second pump light), and the second pump power corresponding to spectrum 401-spectrum 406 changes from low to high. It should be noted that the abscissa corresponding to the spectrum is used to reflect the wavelength of the optical signal (in nanometers, expressed in nm), and the ordinate corresponding to the spectrum is used to reflect the intensity of the optical signal (in decibels, expressed in dB). After testing, the power of the fourth ultrashort pulse laser corresponding to spectrum 401 is 7mW, the power of the second ultrashort pulse laser corresponding to spectrum 402 is 725mW, the power of the second ultrashort pulse laser corresponding to spectrum 403 is 1594mW, and the power of spectrum 404 The power of the corresponding second ultrashort pulse laser is 2356mW, the power of the second ultrashort pulse laser corresponding to spectrum 405 is 2867mW, and the power of the second ultrashort pulse laser corresponding to spectrum 406 is 3420mW. That is, the greater the pumping power of the second pumping light is, the greater the output power of the fourth ultrashort pulse laser is.

The wavelength corresponding to the first intensity peak from right to left in the spectrum is taken as the center wavelength of the first optical soliton (that is, the optical soliton with the largest wavelength red shift), and the wavelength corresponding to the second intensity peak is taken as the second optical soliton center wavelength.

Further, it can be analyzed from the spectrum 401-spectrum 403 that as the second pump power increases, the spectral profile corresponding to the first optical soliton (that is, the third optical soliton) in the fourth ultrashort pulse laser gradually becomes sharp Angular and narrow spectrum. This is a phenomenon caused by the gain-narrowing effect of the second-stage fiber amplifier 104 . From the spectrum 403-spectrum 406, it can be seen that with the further increase of the second pump power, the spectral profile corresponding to the first optical soliton becomes smoother and the spectrum becomes wider. For example, in spectrum 402, the 3dB bandwidth of the first optical soliton in the fourth ultrashort pulse laser is 11nm, while in spectrum 406, the 3dB bandwidth of the first optical soliton in the fourth ultrashort pulse laser is 242nm. That is to say, the fourth ultrashort pulse laser that meets the actual wavelength, power or bandwidth requirements can be obtained by adjusting the pumping power of the second pumping light.

In addition, the central wavelength of the third optical soliton in the fourth ultrashort pulse laser in the spectrum 402-spectrum 406 does not change significantly compared with the central wavelength of the second optical soliton in the third ultrashort pulse laser. However, in actual operation, the central wavelength of the third optical soliton can be further red-shifted by further increasing the second pump power based on the embodiment corresponding to FIG. 4 .

It should be noted that, in the embodiment corresponding to Fig. 4, the central wavelength of the first ultrashort pulse laser can be 2 μm, and its power can be 10 mW, and the second pump laser can be a 796nm semiconductor pump laser, that is, the second pump laser The central wavelength of light may be 796nm, and the second optical soliton with a central wavelength of 2800nm may exist in the third ultrashort pulse laser. The highly nonlinear fluoride fiber can be a fluoride fiber with a length of 5 m, a core diameter of 6.5 μm and a cladding diameter of 125 μm, and a rare earth ion-doped fluoride fiber can be a length of 5 m, a core diameter of 14 μm and a cladding Er ³⁺ doped fluoride optical fiber with a diameter of 250 μm. It can be seen that the power of the fourth ultrashort pulse laser output in the embodiment of the present application is much higher than the power of the first ultrashort pulse laser.

It should be noted that the second pumping laser includes a second pumping fiber, and the second pumping fiber is a transmission medium of the second pumping light.

Optionally, the mid-infrared beam combiner includes a fusion interface between the output end of the light source of the highly nonlinear optical fiber and the input end of the light source of the rare earth ion-doped fluoride optical fiber, and the fusion interface and the output end of the light source of the second pumping optical fiber are fixed by a curing material.

It should be noted that some related technologies commonly use free-space optical elements to couple signal light and pump light. However, the instability of these free-space optical elements will lead to great uncertainty in the pump coupling efficiency. Once the environment is overheated Or when mechanical vibration occurs, the coupling efficiency of the pump light will change drastically, thereby affecting the power of the subsequent output laser. However, the mid-infrared beam combiner in the embodiment of the present application does not contain free-space optical elements, and the coupling efficiency of the third ultrashort pulse laser and the second pump light can reach 90%, which is conducive to the stable operation of the second-stage fiber amplifier 104. Output high-power mid-infrared ultrashort pulse laser.

In an optional embodiment, considering that the reflected light generated by the first-stage fiber amplifier 102 will affect the stability of the near-infrared ultrashort pulse fiber laser 101, a first polarization-independent isolator can be set to isolate the first-stage optical fiber Amplifier 102 produces reflected light. That is to say, the laser output end of the near-infrared ultrashort pulse fiber laser 101 can be connected to the laser input end of the first-stage fiber amplifier 102 through the first polarization-independent isolator.

Considering that the absorption of pump light in the first-stage fiber amplifier is difficult to reach 100%, the second ultrashort pulse laser contains unabsorbed first pump light, and the first stripper can be set to filter out the first pump light, Prevent the temperature of subsequent optical fiber devices from being too high; considering that the reflected light produced by the highly nonlinear fiber 103 will affect the stability of the first-stage fiber amplifier 102, a second polarization-independent isolator can be set to isolate the reflection produced by the highly nonlinear fiber Light: Considering that the materials of the optical fiber in the first-stage optical fiber amplifier 102 and the highly nonlinear optical fiber 103 are different, a silica optical fiber can be set as a transition optical fiber to reduce splicing loss. That is to say, the laser output end of the first-stage fiber amplifier 102 can be connected to the laser input end of the highly nonlinear optical fiber 103 through the second polarization-independent isolator, the first stripper, and the silica fiber in sequence. The connection method is optical fiber fusion splicing. Optionally, the silica optical fiber may be a silica optical fiber with a length of 20 cm, a core diameter of 7.5 μm and a cladding diameter of 125 μm.

Considering that the absorption of the pump light in the second-stage fiber amplifier is difficult to reach 100%, the fourth ultrashort pulse laser contains the unabsorbed second pump light, and the second stripper can be set to filter the second pump light, It is beneficial to obtain a mid-infrared ultrashort pulse laser that meets actual needs, that is to say, the laser output end of the second-stage fiber amplifier 104 can be connected to a second power stripper.

The mid-infrared ultrashort pulse laser in the embodiment of the present application may also include some more specific components, which are easy to understand. The following is an example. Please refer to Figure 5. Figure 5 is a mid-infrared ultrashort pulse laser provided in the embodiment of the present application. Schematic diagram of the structure of the laser 50.

The mid-infrared ultrashort pulse laser 50 includes a near-infrared ultrashort pulse fiber laser 501, a first polarization-independent isolator 502, a first pump laser 503, a near-infrared beam combiner 504, a first rare earth ion-doped silica fiber 505, a first A stripper 506, a second polarization-independent isolator 507, a silica fiber 508, a highly nonlinear fiber 509, a second pump laser 510, a mid-infrared beam combiner 511, a rare earth ion-doped fluoride fiber 512, and a second stripper 513 . Among them, the connection mode between each component is optical fiber fusion splicing.

Specifically, the near-infrared ultrashort pulse fiber laser 501 is used to output the first ultrashort pulse laser as a seed light source. The first ultrashort pulse laser is input to the near-infrared beam combiner 504 through the first polarization-independent isolator 502; the first pump laser 503 is used to generate the first pump light and input it to the near-infrared beam combiner 504; the near-infrared combiner The beamer 504 is used to couple the first ultrashort pulse laser and the first pumping light to the first rare earth ion doped silica fiber 505; the first rare earth ion doped silica fiber 505 is used to couple the first ultrashort pulse laser light based on the first pumping light The power of the pulse laser is amplified and the central wavelength of the first ultrashort pulse laser is red-shifted, and the second ultrashort pulse laser is output; the first polarization-independent isolator 502 is used to isolate the first pump laser 503 and the near-infrared beam combiner 504 and/or the reflected light generated by the first rare earth ion-doped silica fiber 505. The second ultrashort pulse laser is sequentially input to the high nonlinear optical fiber 509 through the first stripper 506, the second polarization-independent isolator 507, and the quartz fiber 508; the first stripper 506 is used to filter out the The first pump light; the second polarization-independent isolator 507 is used to isolate the reflected light generated by the highly nonlinear optical fiber 509; the quartz optical fiber 508 is used to reduce the splice loss when the highly nonlinear optical fiber 509 is connected to the second polarization-independent isolator 507 . The high nonlinear fiber 509 is used to further redshift the central wavelength of the second ultrashort pulse laser, and output the third ultrashort pulse laser to the mid-infrared beam combiner 511; the second pump laser 510 is used to generate the second pump light And input it to the mid-infrared beam combiner 511; the mid-infrared beam combiner 511 is used to couple the third ultrashort pulse laser and the second pumping light to the rare earth ion-doped fluoride optical fiber 512. Rare-earth ion-doped fluoride fiber 512 is used to amplify the power of the third ultrashort pulse laser (in combination with actual needs, the center wavelength of the third ultrashort pulse laser can be further red-shifted), and output the fourth ultrashort pulse laser to the second The stripper 513; the second stripper 513 is used to filter out the second pump light in the fourth ultrashort pulse laser, and output a high-power mid-infrared ultrashort pulse laser that meets actual needs.

It should be noted that the near-infrared ultrashort pulse fiber laser 501 can be the near-infrared ultrashort pulse fiber laser 101 in FIG. The components 514 can be the first-stage fiber amplifier 102 in Fig. 1; the high nonlinear fiber 509 can be the high nonlinear fiber 103 in Fig. 1; the second pump laser 510, the mid-infrared beam combiner 511 and the rare earth doped Component 515 of ionic fluoride fiber 512 may be second stage fiber amplifier 104 in FIG. 1 . For the specific description of the above components, reference may be made to the relevant descriptions of the components in the embodiment corresponding to FIG. 1 , which will not be repeated here.

In summary, the mid-infrared ultrashort pulse laser in the embodiment of the present application can stably output high-power mid-infrared ultrashort pulse laser with tunable wavelength.

In addition, the mid-infrared ultrashort pulse laser in the embodiment of the present application can avoid the use of free-space optical elements to achieve pump coupling, and the components in the mid-infrared ultrashort pulse laser are connected by optical fiber fusion. Infrared ultrashort pulse laser is an all-fiber mid-infrared ultrashort pulse laser. Compared with traditional mid-infrared lasers, its structure is more compact and its cost is lower.

"Multiple" mentioned in the embodiments of this application refers to two or more, and "and/or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, A and/or B, which may represent : There are three cases of A alone, A and B at the same time, and B alone, where A and B can be singular or plural. And, unless otherwise stated, the "first" mentioned in the embodiment of this application is only used for name identification, and is not used to limit the order, timing, priority or importance of multiple objects, such as the first ultrashort pulse Laser, the first fiber amplifier and the first optical soliton, etc. The same rule applies to "second," "third," and "fourth," etc.

The above is only a specific embodiment of the application, but the scope of protection of the application is not limited thereto. Any person familiar with the technical field can easily think of various equivalents within the scope of the technology disclosed in the application. Modifications or replacements, these modifications or replacements shall be covered within the scope of protection of this application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (10)

1. A mid-infrared ultrashort pulse laser, characterized in that the laser comprises: A near-infrared ultrashort pulse fiber laser, used to output a first ultrashort pulse laser, wherein the center wavelength of the first ultrashort pulse laser is in the near infrared band; The first-stage fiber amplifier is used to process the first ultrashort pulse laser and output the second ultrashort pulse laser, wherein the power of the second ultrashort pulse laser is greater than the power of the first ultrashort pulse laser, There is a first optical soliton in the second ultrashort pulse laser, the central wavelength of the first optical soliton is greater than the central wavelength of the first ultrashort pulse laser, and the central wavelength of the first optical soliton is in the near-infrared band ; A highly nonlinear optical fiber, used to process the second ultrashort pulse laser and output a third ultrashort pulse laser, wherein there is a second optical soliton in the third ultrashort pulse laser, and the second optical soliton The central wavelength of the first optical soliton is greater than the central wavelength of the first optical soliton, and the central wavelength of the second optical soliton is in the mid-infrared band; The second-stage fiber amplifier is used to process the third ultrashort pulse laser and output a fourth ultrashort pulse laser, wherein the output power of the fourth ultrashort pulse laser is greater than that of the second ultrashort pulse laser and the power of the third ultrashort pulse laser, there is a third optical soliton in the fourth ultrashort pulse laser, and the central wavelength of the third optical soliton is greater than or equal to the central wavelength of the second optical soliton , the second-stage fiber amplifier does not contain free-space optical elements. 2. The laser according to claim 1, characterized in that: The first-stage optical fiber amplifier includes a first pump laser, a near-infrared beam combiner and a first rare-earth ion-doped silica fiber, wherein the first pump laser is used to generate the first pump light, and the near-infrared A beam combiner is used to couple the first ultrashort pulse laser and the first pump light to the first rare earth ion-doped silica fiber, and the first rare earth ion-doped silica fiber is used to The short pulse laser and the first pump light output the second ultrashort pulse laser; And/or, the second-stage fiber amplifier includes a second pump laser, a mid-infrared beam combiner, and a rare-earth ion-doped fluoride fiber, wherein the second pump laser is used to generate a second pump light, so The center wavelength of the second pump light is greater than the center wavelength of the first pump light, and the mid-infrared beam combiner is used to couple the third ultrashort pulse laser and the second pump light to the A rare-earth ion-doped fluoride optical fiber, the rare-earth ion-doped fluoride optical fiber is used to output the fourth ultrashort pulse laser based on the third ultrashort pulse laser and the second pumping light source. 3. The laser according to claim 2, characterized in that: The first pump laser and/or the second pump laser are used to adjust the power of the generated pump light, so as to control the central wavelength of the fourth ultrashort pulse laser. 4. The laser according to claim 2 or 3, characterized in that: The laser output end of the near-infrared ultrashort pulse fiber laser is connected to the laser input end of the first-stage fiber amplifier through a first polarization-independent isolator, wherein the first polarization-independent isolator is used to isolate the first-stage Reflected light generated by the fiber amplifier; The laser output end of the first-stage fiber amplifier is connected to the laser input end of the high nonlinear optical fiber through the first stripper, the second polarization-independent isolator and the quartz fiber in sequence, wherein the second polarization-independent isolator is used for isolating the reflected light generated by the highly nonlinear fiber, the first stripper is used to filter out the first pump light in the second ultrashort pulse laser, and the silica fiber is used to reduce the Fiber loss produced when connecting the second polarization-independent isolator; The laser output end of the highly nonlinear optical fiber is connected to the laser input end of the second-stage fiber amplifier; The laser output end of the second-stage fiber amplifier is connected to a second power stripper, and the second stripper is used to filter out the second pump light in the fourth ultrashort pulse laser. 5. The laser according to claim 2 or 3, wherein the mid-infrared beam combiner comprises a fusion interface between the light source output end of the highly nonlinear optical fiber and the light source input end of the rare earth ion-doped fluoride optical fiber , the fusion interface and the light source output end of the pumping fiber in the second pumping laser are fixed by a curing material. 6. The laser according to any one of claims 1-3, characterized in that: The near-infrared ultrashort pulse fiber laser includes a second rare earth ion-doped silica fiber, wherein the second rare earth ion doped silica fiber is used to generate the first ultrashort pulse laser. 7. The laser according to any one of claims 1-3, characterized in that: The highly nonlinear fiber includes a highly nonlinear fluoride fiber. 8. A method for obtaining mid-infrared ultra-short pulse laser, characterized in that it is applied to mid-infrared ultra-short pulse laser, and said laser includes near-infrared ultra-short pulse fiber laser, first-stage optical fiber amplifier, highly nonlinear optical fiber and A second-stage optical fiber amplifier, the method comprising: Outputting a first ultrashort pulse laser through a near-infrared ultrashort pulse fiber laser, wherein the central wavelength of the first ultrashort pulse laser is in the near-infrared band; The first ultrashort pulse laser is processed by the first-stage fiber amplifier, and the second ultrashort pulse laser is output, wherein the power of the second ultrashort pulse laser is greater than the power of the first ultrashort pulse laser, and the There is a first optical soliton in the second ultrashort pulse laser, the central wavelength of the first optical soliton is greater than the central wavelength of the first ultrashort pulse laser, and the central wavelength of the first optical soliton is in the near-infrared band; The second ultrashort pulse laser is processed through a highly nonlinear optical fiber to output a third ultrashort pulse laser, wherein there is a second optical soliton in the third ultrashort pulse laser, and the center of the second optical soliton The wavelength is greater than the central wavelength of the first optical soliton, and the central wavelength of the second optical soliton is in the mid-infrared band; The third ultrashort pulse laser is processed by a second-stage fiber amplifier to output a fourth ultrashort pulse laser, wherein the output power of the fourth ultrashort pulse laser is greater than the power of the second ultrashort pulse laser and the power of the third ultrashort pulse laser, there is a third optical soliton in the fourth ultrashort pulse laser, and the central wavelength of the third optical soliton is greater than or equal to the central wavelength of the second optical soliton, so The second-stage fiber amplifier described above does not contain free-space optics. 9. method according to claim 8, is characterized in that, described first stage optical fiber amplifier comprises the first pump laser, near-infrared beam combiner and the first rare earth ion doped silica fiber; The amplifier processes the first ultrashort pulse laser and outputs the second ultrashort pulse laser, including: generating first pump light by the first pump laser; coupling the first ultrashort pulse laser and the first pump light to the first rare earth ion-doped silica fiber through the near-infrared beam combiner; outputting the second ultrashort pulse laser based on the first ultrashort pulse laser and the first pumping light through the first rare earth ion-doped silica fiber. 10. The method according to claim 8 or 9, wherein the second-stage fiber amplifier comprises a second pump laser, a mid-infrared beam combiner, and a rare-earth ion-doped fluoride optical fiber; The fiber amplifier processes the third ultrashort pulse laser and outputs the fourth ultrashort pulse laser, including: generating a second pump light by the second pump laser, wherein the center wavelength of the second pump light is greater than the center wavelength of the first pump light; coupling the third ultrashort pulse laser light and the second pump light to the rare earth ion-doped fluoride optical fiber through the mid-infrared beam combiner; Outputting the fourth ultrashort pulse laser based on the third ultrashort pulse laser and the second pumping light source through the rare earth ion-doped fluoride fiber.

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