CN113285340A - Device and method for generating intermediate infrared wide-spectrum femtosecond laser - Google Patents
Device and method for generating intermediate infrared wide-spectrum femtosecond laser Download PDFInfo
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
- H01S3/1022—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/131—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
- H01S3/1312—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping
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Abstract
The invention discloses a device and a method for generating a mid-infrared wide-spectrum femtosecond laser, wherein the device comprises: the frequency multiplier is used for taking the received and shaped femtosecond laser beam as fundamental frequency light to generate frequency doubling light, and the light beam containing the fundamental frequency light and the frequency doubling light passes through the wave plate to rotate the polarization direction of the fundamental frequency light to be the same as the polarization direction of the frequency doubling light; the delay device is used for receiving the polarization-aligned collinear fundamental frequency light and frequency doubling light, and adjusting the delay of the fundamental frequency light and the delay of the frequency doubling light to ensure that the fundamental frequency light and the frequency doubling light are overlapped in time; the focusing mirror is used for receiving the collinear output light beam after the combination of the fundamental frequency light and the frequency doubling light and focusing the collinear output light beam into the gas chamber; a gas chamber for generating a mid-infrared wide-spectrum femtosecond laser; and the collimating lens is used for collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light and outputting the parallel light. The invention solves the problem of light beam stability caused by gas disturbance and the problem of corrosion of ozone to optical devices.
Description
Technical Field
The invention relates to the field of laser, in particular to a device and a method for generating intermediate infrared wide-spectrum femtosecond laser.
Background
The wavelength range of the mid-infrared band is between 2 and 20 mu m, the molecular spectroscopy fingerprint region is a molecular spectroscopy fingerprint region, and the information such as the molecular species, the structure and the like can be analyzed by representing the absorption of molecules in the mid-infrared band, so that the molecular spectroscopy fingerprint region has important application in a plurality of fields such as basic research, national defense and military industry, medical treatment and health, industrial environment and the like. The femtosecond intermediate infrared light source combines the time resolution characteristic of femtosecond laser, and is widely applied to ultrafast time resolution dynamics measurement by combining with visible and ultraviolet femtosecond laser to analyze the vibration energy transfer process of substance molecules. At present, the mainstream generation method of the mid-infrared femtosecond laser spectrum comprises a method of combining optical parametric amplification with difference frequency and a method of gas plasma multi-wavelength nonlinear transformation. The former is limited by the crystal phase matching angle, the laser frequency range is concentrated, and the laser energy density in unit frequency is higher. The latter has a lower energy density in the infrared band but produces a spectral range that covers almost the entire mid-infrared band. In infrared femtosecond time-resolved spectroscopy measurement, infrared light generated by a gas plasma multi-wavelength nonlinear transformation method has a flatter spectral curve, and higher data collection efficiency can be realized by combining the infrared spectrometer with the infrared spectrometer. Meanwhile, the realization principle and the system structure of the gas plasma multi-wavelength nonlinear transformation technology are simpler than those of the gas plasma multi-wavelength nonlinear transformation technology, the requirements on the beam quality of a laser light source are relatively low, and the gas plasma multi-wavelength nonlinear transformation technology has good application potential.
A broadband mid-infrared femtosecond laser generating device based on gas plasma multi-wavelength nonlinear transformation mainly comprises the following principles: firstly, the fundamental frequency femtosecond laser is frequency-doubled, the polarization direction of the fundamental frequency femtosecond laser is adjusted to be the same as that of the fundamental frequency light, and then the fundamental frequency light and the frequency-doubled light are adjusted to be overlapped in space and time and focused in gas to generate plasma. And carrying out nonlinear frequency conversion on the two beams of light in the plasma, further generating mid-infrared femtosecond laser, and finally collimating and outputting.
When the femtosecond laser is focused in a gas, the energy density at the focal position is extremely high, and the gas is ionized into plasma and emits light and sound waves. The solution currently available is to directly place the focus in air, however, this solution has two serious problems: (1) because the generation process of infrared light is a complex nonlinear optical process, the intensity of the generated mid-infrared light and the gas state of the spectrum at the focusing point position are very sensitive, and the slight disturbance of air can cause the violent jitter of the output infrared light, the stability of the infrared light obtained by adopting the scheme is very poor; (2) the plasma in the air can generate ozone continuously, which can lead to rapid corrosion of the lens and the optical mechanical elements around the focal point in long-time continuous work. The existence of the two problems causes that the technology is difficult to be applied to infrared transient absorption spectroscopy measurement, and the instrumental and commercial development progress of the technology is hindered.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a device and a method for generating a mid-infrared wide-spectrum femtosecond laser, which solve the problems of beam stability and corrosion of ozone to an optical device caused by gas disturbance by using a specially designed gas chamber and placing a focus in the gas chamber.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a mid-infrared wide-spectrum femtosecond laser generation device comprises: the frequency multiplier, the retarder, the focusing mirror, the gas chamber and the collimating mirror are arranged along the light path;
the frequency multiplier is used for generating frequency-doubled light perpendicular to the polarization direction of the fundamental frequency light by taking the received femtosecond laser beam as the fundamental frequency light, and rotating the polarization direction of the fundamental frequency light by passing the light beam containing the fundamental frequency light and the frequency-doubled light through a wave plate to enable the polarization direction of the fundamental frequency light to be the same as the polarization direction of the frequency-doubled light;
the delayer is used for receiving the fundamental frequency light and the frequency doubling light which are polarization-aligned and collinear, and adjusting the delay of the fundamental frequency light and the frequency doubling light so that the fundamental frequency light and the frequency doubling light coincide in time;
the focusing mirror is used for receiving the collinear output light beam after the fundamental frequency light and the frequency doubling light are combined and focusing the output light beam into the gas chamber;
the gas chamber is used for generating plasma through internal focusing when the fundamental frequency light and the frequency doubling light coincide in space and time, and generating mid-infrared wide-spectrum femtosecond laser through nonlinear optical transformation;
and the collimating lens is used for collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light and outputting the parallel light.
Further, in the device for generating a mid-infrared wide-spectrum femtosecond laser, the wave plate is a dual-wavelength wave plate, the half-wave plate is used for fundamental-frequency light, and the full-wave plate is used for frequency-doubled light.
Further, the mid-infrared wide-spectrum femtosecond laser generating apparatus as described above, the retarder includes: a dichroic mirror, a frequency doubling light total reflection mirror and a fundamental frequency light total reflection mirror are arranged along the light path;
after the fundamental frequency light and the frequency doubling light which are polarized and aligned and collinear pass through the dichroic mirror, the frequency doubling light is reflected, reflected light is reflected by the frequency doubling light total reflecting mirror back to the dichroic mirror, meanwhile, the fundamental frequency light penetrates through the dichroic mirror and is reflected by the fundamental frequency light total reflecting mirror, the position of the fundamental frequency light total reflecting mirror is adjusted to enable the fundamental frequency light to be superposed and collinear with the frequency doubling light on the dichroic mirror, the position of the translation stage is adjusted back and forth to enable the fundamental frequency light to be superposed with the frequency doubling light in time, and when the fundamental frequency light and the frequency doubling light pass through the dichroic mirror again, collinear output light beams after the fundamental frequency light and the frequency doubling light are combined are obtained.
Further, the mid-infrared broad spectrum femtosecond laser generating apparatus as described above, the gas chamber comprising: the device comprises an incident window, a shell and an emergent window, wherein the incident window and the emergent window are respectively connected with the shell to form an airtight structure together, and inert gas is filled in the airtight structure.
Further, in the above mid-infrared wide-spectrum femtosecond laser generating apparatus, the incident window is made of optical glass that can transmit femtosecond fundamental frequency light and frequency doubling light, and the exit window is made of optical glass that can transmit infrared light;
and after the output light beams which are combined by the fundamental frequency light and the frequency doubling light and are collinear penetrate through the incidence window, the plasma is generated by focusing in the gas chamber, and the intermediate infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion and is output through the exit window.
The embodiment of the invention also provides a method for generating the intermediate infrared wide-spectrum femtosecond laser, which comprises the following steps:
s100, the frequency multiplier takes the received femtosecond laser beam as base frequency light to generate frequency doubling light vertical to the polarization direction of the base frequency light;
s200, enabling the light beam containing the fundamental frequency light and the frequency doubling light to pass through a wave plate, and rotating the polarization direction of the fundamental frequency light to be the same as that of the frequency doubling light;
s300, receiving the fundamental frequency light and the frequency doubling light which are aligned in polarization and collinear by a delayer, and adjusting the delay of the fundamental frequency light and the frequency doubling light to enable the fundamental frequency light and the frequency doubling light to coincide in time;
s400, a focusing mirror receives the collinear output light beam after the fundamental frequency light and the frequency doubling light are combined, and the output light beam is focused into the gas chamber;
s500, when the fundamental frequency light and the frequency doubling light are overlapped in space and time, the gas chamber is internally focused to generate plasma, and mid-infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion;
s600, collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light by using a collimating mirror and then outputting the parallel light.
Further, in the method for generating a mid-infrared wide-spectrum femtosecond laser, the wave plate is a dual-wavelength wave plate, the half-wave plate is used for fundamental-frequency light, and the full-wave plate is used for frequency-doubled light.
Further, the method for generating a mid-infrared wide-spectrum femtosecond laser as described above, the retarder includes: a dichroic mirror, a frequency doubling light total reflection mirror and a fundamental frequency light total reflection mirror are arranged along the light path; s400 includes:
after the fundamental frequency light and the frequency doubling light which are polarized and aligned and collinear pass through the dichroic mirror, the frequency doubling light is reflected, reflected light is reflected by the frequency doubling light total reflecting mirror back to the dichroic mirror, meanwhile, the fundamental frequency light penetrates through the dichroic mirror and is reflected by the fundamental frequency light total reflecting mirror, the position of the fundamental frequency light total reflecting mirror is adjusted to enable the fundamental frequency light to be superposed and collinear with the frequency doubling light on the dichroic mirror, the position of the translation stage is adjusted back and forth to enable the fundamental frequency light to be superposed with the frequency doubling light in time, and when the fundamental frequency light and the frequency doubling light pass through the dichroic mirror again, collinear output light beams after the fundamental frequency light and the frequency doubling light are combined are obtained.
Further, the method for generating a mid-infrared wide-spectrum femtosecond laser as described above, the gas chamber comprising: the device comprises an incident window, a shell and an emergent window, wherein the incident window and the emergent window are respectively connected with the shell to form an airtight structure together, and inert gas is filled in the airtight structure.
Further, in the method for generating a mid-infrared wide-spectrum femtosecond laser, the incident window is made of optical glass which can transmit femtosecond fundamental frequency light and frequency doubling light, and the exit window is made of optical glass which can transmit infrared light; s600 comprises the following steps:
and after the output light beams which are combined by the fundamental frequency light and the frequency doubling light and are collinear penetrate through the incidence window, the plasma is generated by focusing in the gas chamber, and the intermediate infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion and is output through the exit window.
The invention has the beneficial effects that: the invention uses the special design and the closed gas chamber filled with inert gas, and the light beam focus is arranged in the gas chamber, thereby greatly improving the stability of the output infrared light and simultaneously solving the problem of corrosion of optical elements caused by ozone generated by plasma.
Drawings
Fig. 1 is a schematic structural diagram of a mid-infrared wide-spectrum femtosecond laser generation device provided in an embodiment of the present invention;
fig. 2 is a schematic flow chart of a method for generating a mid-infrared wide-spectrum femtosecond laser according to an embodiment of the present invention.
In the drawings: 1-a beam shaper; 2-a frequency multiplier; 3-a wave plate; 4-a dichromatic mirror; 5-frequency doubling light total reflection mirror; 6-fundamental frequency light holophote; 7-a translation stage; 8-a focusing mirror; 9-a gas chamber; 10-a reflective collimating mirror; 11-output mirror.
Detailed Description
In order to make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be further described in detail with reference to the accompanying drawings.
An embodiment of the present invention provides a device for generating a mid-infrared wide-spectrum femtosecond laser, as shown in fig. 1, the device includes: and the beam shaper 1, the frequency multiplier 2, the retarder, the focusing mirror 8, the gas chamber 9 and the collimating mirror 10 are arranged along the light path. And the beam shaper 1 is used for shaping the femtosecond laser beam and transmitting the shaped femtosecond laser beam to the frequency multiplier 2. And the frequency multiplier 2 is used for generating frequency-doubled light perpendicular to the polarization direction of the base frequency light by taking the received shaped femtosecond laser beam as the base frequency light, and rotating the polarization direction of the base frequency light by passing the light beam containing the base frequency light and the frequency-doubled light through a wave plate to enable the polarization direction of the base frequency light to be the same as the polarization direction of the frequency-doubled light. And the delayer is used for receiving the polarization-aligned collinear fundamental frequency light and frequency doubling light, and adjusting the delay of the fundamental frequency light and the frequency doubling light so that the fundamental frequency light and the frequency doubling light are overlapped in time. The focusing mirror 8, which may be a reflective focusing mirror, is configured to receive the collinear output beam after combining the fundamental frequency light and the frequency doubled light, and focus the output beam into the gas chamber 9. And the gas chamber 9 is used for internally focusing to generate plasma when the fundamental frequency light and the frequency doubling light coincide in space and time, and generating the mid-infrared wide-spectrum femtosecond laser through nonlinear optical transformation. And the collimating mirror 10 is used for collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light and outputting the parallel light.
In the embodiment of the invention, after the input femtosecond laser beam passes through the beam shaper 1, the beam diameter is adjusted to a proper size, and the beam diameter is subject to the condition that the beam diameter can obtain high frequency doubling efficiency in the frequency multiplier 2, namely a frequency doubling crystal, and meanwhile, the correct numerical aperture is obtained at the focusing position.
In the embodiment of the invention, the wave plate 3 is a dual-wavelength wave plate, the fundamental frequency light is a half-wave plate, and the frequency doubling light is a full-wave plate, so that the polarization direction of the fundamental frequency light beam can be adjusted by the wave plate, and the polarization direction of the frequency doubling light beam is kept unchanged.
In an embodiment of the present invention, a delay device includes: a dichroic mirror, a frequency doubling light total reflection mirror and a fundamental frequency light total reflection mirror which are arranged along the light path. The base frequency light and the frequency doubling light which are aligned in polarization and collinear pass through the dichroic mirror, the frequency doubling light is reflected, the reflected light is reflected back to the dichroic mirror by the frequency doubling light total reflection mirror, meanwhile, the base frequency light penetrates through the dichroic mirror and is reflected by the base frequency light total reflection mirror, the position of the base frequency light total reflection mirror is adjusted to enable the base frequency light to be overlapped and collinear with the frequency doubling light on the dichroic mirror, the position of the translation stage is adjusted back and forth to enable the base frequency light to be overlapped with the frequency doubling light in time, and when the light passes through the dichroic mirror again, collinear output light beams after the base frequency light and the frequency doubling light are combined are obtained.
In an embodiment of the present invention, the gas chamber is a core component of the present invention, and includes: the plasma lamp comprises an incident window, a shell and an emergent window, wherein the incident window and the emergent window are respectively connected with the shell to jointly form an airtight structure, and inert gas is filled inside the airtight structure to achieve the purposes of stabilizing the plasma state and eliminating ozone, and finally improve the light beam stability and avoid the corrosion of optical elements. The laser comprises an incident window, an exit window, an incident window, an infrared light source, a shell and a laser, wherein the incident window is used for transmitting the infrared light, the exit window is made of optical glass capable of transmitting the femtosecond fundamental frequency light and the frequency doubling light, the incident window is made of the optical glass capable of transmitting the femtosecond fundamental frequency light and the frequency doubling light, the exit window is made of the optical glass capable of transmitting the infrared light, and the shell is made of stainless steel. In particular, the entrance window may be a quartz window, the exit window may be a calcium fluoride window, and the inert gas may be high purity argon.
As shown in fig. 1, the optical path transmission process of the above device is as follows: the femtosecond laser beam a is input as a femtosecond laser beam with the wavelength of 800nm, and the beam diameter is adjusted to a proper size after passing through the beam shaper 1, so that a beam b, namely the fundamental frequency light, is obtained. After passing through the BBO frequency multiplier 2, frequency-doubled light c with the wavelength of 400nm and collinear with the fundamental frequency light is generated, and the light beam is vertical to the polarization direction of the fundamental frequency light beam. The wave plate 3 is a dual-wavelength wave plate, the 800nm fundamental frequency light is a half-wave plate, the 400nm frequency doubling light is a full-wave plate, and the wave plate 3 is adjusted to enable the polarization direction of the 800nm fundamental frequency light to rotate and align with the polarization direction of the 400nm frequency doubling light, so that a light beam d is obtained. After two beams of polarized and aligned collinear light pass through the dichroic mirror 4, 400nm frequency-doubled light is reflected, and the reflection angle is slightly smaller than 90 degrees, namely a light beam e. The reflected light is reflected by the frequency doubling total reflection mirror 5 back to the dichroic mirror 4 at a position slightly deviated from the light splitting position of the dichroic mirror 4. Meanwhile, the 800nm fundamental frequency light passes through the dichroic mirror 4 and is reflected by the fundamental frequency light total reflection mirror 6, i.e., a light beam f. The fundamental frequency light total reflection mirror 6 is adjusted so that the reflected 800nm fundamental frequency light coincides with and collimates with 400nm frequency doubled light on the dichroic mirror 4. The position of the translation stage 7 is adjusted back and forth so that the 800nm fundamental light coincides in time with the 400nm octave light. When the two light beams pass through the dichroic mirror 4 again, the two light beams are recombined into a light beam g and are focused by the focusing mirror 8, the focused light beam h enters the gas chamber 9, and the focus is positioned inside the gas chamber 9.
The gas chamber is formed by integrally processing a quartz window sheet, a stainless steel shell and a calcium fluoride window sheet, and a high-purity argon gas is filled in an inner cavity. The dual-wavelength laser beam h reflected by the focusing mirror 8 passes through the quartz window, is focused in the gas chamber to form a plasma region, and is converted into a supercontinuum femtosecond laser i containing wide-spectrum infrared light through nonlinear optical conversion, and is output through the calcium fluoride window. The collimating mirror 10 collimates the light beam i, reflects the light beam i to the output mirror 11, and outputs the light beam j.
By adopting the device provided by the embodiment of the invention, the specially designed closed gas chamber filled with inert gas is used, and the light beam focus is arranged in the gas chamber, so that the stability of outputting infrared light is greatly improved, and the problem of corrosion of an optical element caused by ozone generated by plasma is solved.
The embodiment of the invention also provides a method for generating the intermediate infrared wide-spectrum femtosecond laser, as shown in fig. 2, which comprises the following steps:
s100, the frequency multiplier takes the received femtosecond laser beam as base frequency light to generate frequency doubling light vertical to the polarization direction of the base frequency light;
s200, enabling the light beam containing the fundamental frequency light and the frequency doubling light to pass through a wave plate, and rotating the polarization direction of the fundamental frequency light to enable the polarization direction of the fundamental frequency light to be the same as the polarization direction of the frequency doubling light;
s300, receiving the polarization-aligned collinear fundamental frequency light and frequency doubling light by a delayer, and adjusting the delay of the fundamental frequency light and the frequency doubling light to ensure that the fundamental frequency light and the frequency doubling light coincide in time;
s400, a focusing mirror receives collinear output light beams after the fundamental frequency light and the frequency doubling light are combined, and the output light beams are focused into a gas chamber;
s500, when the fundamental frequency light and the frequency doubling light coincide in space and time, the gas chamber is internally focused to generate plasma, and mid-infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion;
s600, collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light by using a collimating mirror and then outputting the parallel light.
By adopting the method of the embodiment of the invention, the specially designed closed gas chamber filled with inert gas is used, and the light beam focus is arranged in the gas chamber, so that the stability of the output infrared light is greatly improved, and the problem of corrosion of an optical element caused by ozone generated by plasma is solved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.
Claims (10)
1. A mid-infrared wide-spectrum femtosecond laser generation device is characterized by comprising: the frequency multiplier, the retarder, the focusing mirror, the gas chamber and the collimating mirror are arranged along the light path;
the frequency multiplier is used for generating frequency-doubled light perpendicular to the polarization direction of the fundamental frequency light by taking the received femtosecond laser beam as the fundamental frequency light, and rotating the polarization direction of the fundamental frequency light by passing the light beam containing the fundamental frequency light and the frequency-doubled light through a wave plate to enable the polarization direction of the fundamental frequency light to be the same as the polarization direction of the frequency-doubled light;
the delayer is used for receiving the fundamental frequency light and the frequency doubling light which are polarization-aligned and collinear, and adjusting the delay of the fundamental frequency light and the frequency doubling light so that the fundamental frequency light and the frequency doubling light coincide in time;
the focusing mirror is used for receiving the collinear output light beam after the fundamental frequency light and the frequency doubling light are combined and focusing the output light beam into the gas chamber;
the gas chamber is used for generating plasma through internal focusing when the fundamental frequency light and the frequency doubling light coincide in space and time, and generating mid-infrared wide-spectrum femtosecond laser through nonlinear optical transformation;
and the collimating lens is used for collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light and outputting the parallel light.
2. The mid-infrared wide-spectrum femtosecond laser generation device according to claim 1, wherein the wave plate is a dual-wavelength wave plate, a half-wave plate for fundamental-frequency light, and a full-wave plate for frequency-doubled light.
3. The mid-infrared wide-spectrum femtosecond laser generation apparatus according to claim 1, wherein the retarder includes: a dichroic mirror, a frequency doubling light total reflection mirror and a fundamental frequency light total reflection mirror are arranged along the light path;
after the fundamental frequency light and the frequency doubling light which are polarized and aligned and collinear pass through the dichroic mirror, the frequency doubling light is reflected, reflected light is reflected by the frequency doubling light total reflecting mirror back to the dichroic mirror, meanwhile, the fundamental frequency light penetrates through the dichroic mirror and is reflected by the fundamental frequency light total reflecting mirror, the position of the fundamental frequency light total reflecting mirror is adjusted to enable the fundamental frequency light to be superposed and collinear with the frequency doubling light on the dichroic mirror, the position of the translation stage is adjusted back and forth to enable the fundamental frequency light to be superposed with the frequency doubling light in time, and when the fundamental frequency light and the frequency doubling light pass through the dichroic mirror again, collinear output light beams after the fundamental frequency light and the frequency doubling light are combined are obtained.
4. The mid-infrared broad spectrum femtosecond laser generation apparatus as set forth in claim 1, wherein the gas chamber includes: the device comprises an incident window, a shell and an emergent window, wherein the incident window and the emergent window are respectively connected with the shell to form an airtight structure together, and inert gas is filled in the airtight structure.
5. The mid-infrared broad-spectrum femtosecond laser generation device according to claim 4, wherein the incident window is made of optical glass which can transmit femtosecond fundamental frequency light and frequency doubling light, and the exit window is made of optical glass which can transmit infrared light;
and after the output light beams which are combined by the fundamental frequency light and the frequency doubling light and are collinear penetrate through the incidence window, the plasma is generated by focusing in the gas chamber, and the intermediate infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion and is output through the exit window.
6. A method for generating a mid-infrared wide-spectrum femtosecond laser is characterized by comprising the following steps:
s100, the frequency multiplier takes the received femtosecond laser beam as base frequency light to generate frequency doubling light vertical to the polarization direction of the base frequency light;
s200, enabling the light beam containing the fundamental frequency light and the frequency doubling light to pass through a wave plate, and rotating the polarization direction of the fundamental frequency light to be the same as that of the frequency doubling light;
s300, receiving the fundamental frequency light and the frequency doubling light which are aligned in polarization and collinear by a delayer, and adjusting the delay of the fundamental frequency light and the frequency doubling light to enable the fundamental frequency light and the frequency doubling light to coincide in time;
s400, a focusing mirror receives the collinear output light beam after the fundamental frequency light and the frequency doubling light are combined, and the output light beam is focused into the gas chamber;
s500, when the fundamental frequency light and the frequency doubling light are overlapped in space and time, the gas chamber is internally focused to generate plasma, and mid-infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion;
s600, collimating the received mid-infrared wide-spectrum femtosecond laser into parallel light by using a collimating mirror and then outputting the parallel light.
7. The method as claimed in claim 6, wherein the wave plate is a dual wavelength wave plate, a half wave plate for fundamental frequency light, and a full wave plate for frequency doubled light.
8. The mid-infrared broad spectrum femtosecond laser generation method according to claim 6, wherein the retarder includes: a dichroic mirror, a frequency doubling light total reflection mirror and a fundamental frequency light total reflection mirror are arranged along the light path; s400 includes:
after the fundamental frequency light and the frequency doubling light which are polarized and aligned and collinear pass through the dichroic mirror, the frequency doubling light is reflected, reflected light is reflected by the frequency doubling light total reflecting mirror back to the dichroic mirror, meanwhile, the fundamental frequency light penetrates through the dichroic mirror and is reflected by the fundamental frequency light total reflecting mirror, the position of the fundamental frequency light total reflecting mirror is adjusted to enable the fundamental frequency light to be superposed and collinear with the frequency doubling light on the dichroic mirror, the position of the translation stage is adjusted back and forth to enable the fundamental frequency light to be superposed with the frequency doubling light in time, and when the fundamental frequency light and the frequency doubling light pass through the dichroic mirror again, collinear output light beams after the fundamental frequency light and the frequency doubling light are combined are obtained.
9. The mid-infrared broad spectrum femtosecond laser generation method according to claim 6, wherein the gas chamber includes: the device comprises an incident window, a shell and an emergent window, wherein the incident window and the emergent window are respectively connected with the shell to form an airtight structure together, and inert gas is filled in the airtight structure.
10. The method for generating a mid-infrared broad-spectrum femtosecond laser according to claim 9, wherein the incident window is made of optical glass transparent to femtosecond fundamental frequency light and frequency doubling light, and the exit window is made of optical glass transparent to infrared light; s600 comprises the following steps:
and after the output light beams which are combined by the fundamental frequency light and the frequency doubling light and are collinear penetrate through the incidence window, the plasma is generated by focusing in the gas chamber, and the intermediate infrared wide-spectrum femtosecond laser is generated through nonlinear optical conversion and is output through the exit window.
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