CN113324666B - Femtosecond laser pulse carrier envelope phase offset frequency detection device and method - Google Patents
Femtosecond laser pulse carrier envelope phase offset frequency detection device and method Download PDFInfo
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- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J11/00—Measuring the characteristics of individual optical pulses or of optical pulse trains
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
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Abstract
The invention relates to an ultrashort pulse laser, in particular to a femtosecond laser pulse carrier envelope phase offset frequency detection device and a femtosecond laser pulse carrier envelope phase offset frequency detection method, which are used for solving the problems that in the conventional femtosecond laser pulse carrier envelope phase offset frequency detection, a laser system is complex and difficult to integrate due to the fact that a space optical path structure is complex and the conversion efficiency of a frequency doubling crystal is very sensitive to working temperature. The technical scheme adopted by the invention is as follows: a femtosecond laser pulse carrier envelope phase offset frequency detection device comprises an optical fiber amplifier, a compression optical fiber, a high nonlinear optical fiber, a frequency doubling device and a photoelectric detector which are sequentially connected by an optical fiber; the frequency doubling device comprises a packaging sleeve, a first optical fiber collimator, a frequency doubling crystal and a second optical fiber collimator which are sequentially arranged in the packaging sleeve; the invention also provides a femtosecond laser pulse carrier envelope phase offset frequency detection method.
Description
Technical Field
The invention relates to an ultrashort pulse laser, in particular to a femtosecond laser pulse carrier envelope phase offset frequency detection device and method.
Background
The femtosecond optical frequency comb based on the mode-locked ultrashort pulse laser has the advantages of low noise and stable power, and a periodic pulse signal generated by the femtosecond optical frequency comb has abundant and equally-spaced frequency components in a frequency domain, so that the femtosecond optical frequency comb can be applied to various precise measurement fields. The femtosecond optical frequency comb is utilized, so that the remote high-precision distance measurement can be realized, and the small satellite can be helped to realize the high-precision synchronous operation; high-precision frequency transmission can be realized, and the realization of a clock group 10 is facilitated -11 Clock synchronization of magnitude; meanwhile, the method can be used for generating radar signals with hundreds of GHz level; hazardous chemical gas detection, etc.
One of the reasons why the femtosecond optical frequency comb has high stability is because a nonlinear process inside the laser can be effectively controlled when its core (femtosecond laser) is operated. Thereby suppressing noise of its output signal. To control these nonlinear processes, changes are first detected, which are reflected in the carrier envelope phase offset (CEO) of the femtosecond laser pulses. The CEO variation of the femtosecond laser pulse is a phase variation, and the phase variation evolves a CEO frequency corresponding to the phase variation. Therefore, to control the nonlinear process in the femtosecond laser, the CEO frequency of the femtosecond laser pulse is controlled. Detecting CEO frequency signals requires the use of dispersion compensation techniques after the laser generates the supercontinuum laser such that signals of different frequencies within the supercontinuum laser overlap in time and space. Then, frequency doubling technology is utilized to enable the lower-frequency components in the supercontinuum to generate frequency-doubled signals (the frequency is doubled). The frequency multiplied signal and the original high frequency signal generate a beat frequency signal. The frequency of this beat signal corresponds to the carrier envelope phase offset. However, the existing detecting device has the following disadvantages when meeting the demand for miniaturization and light weight:
1) Due to the dispersion characteristic of the optical fiber, lasers with different frequencies in the supercontinuum laser are not overlapped in time. To detect the CEO signal, dispersion compensation is required for the optical signal after the laser generates the supercontinuum. The supercontinuum laser is collimated by a lens and then becomes space light, and then is divided into two beams of long-wave light and short-wave light by a light splitting device (such as a dichroic mirror or a light splitting prism). The two beams are transmitted in different optical paths for different distances to compensate dispersion. And then the two beams of light are combined into one beam of light through a light splitting device with the same parameters, and finally signals with different frequencies in the super-continuum spectrum are overlapped in time and space. This makes the spatial optical path structure complicated, and it is difficult to integrate the devices with a simple structure.
2) If the complicated optical path is required to work stably for a long time, it is necessary to provide a temperature control device for the whole optical path. Especially, the conversion efficiency of the frequency doubling crystal is very sensitive to the working temperature, so that the frequency doubling crystal has to have a temperature control function for long-time stable operation. The high power temperature control device complicates the laser system, and further makes the complicated optical path more difficult to integrate.
Disclosure of Invention
The invention provides a femtosecond laser pulse carrier envelope phase offset frequency detection device and a method, aiming at solving the problems that in the existing femtosecond laser pulse carrier envelope phase offset frequency detection, a laser system is complex and difficult to integrate due to the complex structure of a spatial light path and the very sensitive conversion efficiency of a frequency doubling crystal to the working temperature.
The technical scheme adopted by the invention is as follows:
a femtosecond laser pulse carrier envelope phase offset frequency detection device is characterized in that:
the device comprises an optical fiber amplifier, a compression optical fiber, a high nonlinear optical fiber, a frequency doubling device and a photoelectric detector which are sequentially connected by optical fibers;
the optical fiber amplifier is used for amplifying the received femtosecond laser pulse;
the compression optical fiber is used for compressing the amplified femtosecond laser pulse;
the high nonlinear optical fiber is used for broadening the received compressed femtosecond laser pulse into a super-continuum spectrum signal;
the frequency doubling device comprises a packaging sleeve, a first optical fiber collimator, a frequency doubling crystal and a second optical fiber collimator which are sequentially arranged in the packaging sleeve; the frequency doubling crystal is a periodically polarized magnesium oxide-doped lithium niobate crystal, and the frequency doubling device is used for sequentially focusing, frequency doubling and coupling supercontinuum signals;
the photoelectric detector is used for converting the coupled supercontinuum signal into an electric signal to be detected after focusing and frequency doubling.
Furthermore, an adaptive sleeve is arranged outside the frequency doubling crystal, the inner diameter of the adaptive sleeve is 0-0.2 mm larger than the diagonal of the input section of the frequency doubling crystal, the outer diameter of the adaptive sleeve is 0-0.2 mm smaller than the inner diameter of the packaging sleeve, and the length of the adaptive sleeve is matched with that of the frequency doubling crystal;
the shells of the first optical fiber collimator and the second optical fiber collimator are both cylindrical and have the same outer diameter as the adaptive sleeve;
the material of adaptation sleeve pipe is metal or quartzy or pottery, the material of encapsulation sleeve pipe is metal or quartzy or pottery.
Furthermore, the range of the polarization period of the lithium niobate crystal is 9-16 μm or 28-34 μm, and the range of the length of the lithium niobate crystal is 1-10 mm.
Furthermore, the first optical fiber collimator and the second optical fiber collimator are both composed of an optical fiber and a single-chip gradient refractive index lens, or composed of an optical fiber and one or a pair of aspheric mirrors; the Rayleigh distance value ranges of the first optical fiber collimator and the second optical fiber collimator are both 0.17-1.8 mm;
and the tail fibers of the first optical fiber collimator and the second optical fiber collimator both adopt polarization-maintaining transmission fibers, and the length of each polarization-maintaining transmission fiber is 1-35 mm and is used for adjusting the dispersion of internal transmission signals.
Furthermore, the optical fiber amplifier comprises a first pumping source, a second pumping source, a first wavelength division multiplexer, a first gain optical fiber, a second gain optical fiber and a second wavelength division multiplexer, wherein the first wavelength division multiplexer, the first gain optical fiber, the second gain optical fiber and the second wavelength division multiplexer are sequentially connected through optical fibers;
the pump light of the optical fiber amplifier is generated by a first pump source or a second pump source and is input into the first wavelength division multiplexer through a first polarization-maintaining single-mode optical fiber by the first pump source, or is input into the second wavelength division multiplexer through a second polarization-maintaining single-mode optical fiber by the second pump source;
the lengths of the first gain fiber and the second gain fiber are both 500-5000 mm, the dispersion near the working wavelength is-60-0 ps/km/nm, and the absorption is 5-1000 dB/m.
Further, the compressed optical fiber has a dispersion of 18ps/km/nm for reducing the width of the femtosecond laser pulse to not more than 200fs; the high nonlinear optical fiber adopts photonic crystal fiber or polarization maintaining high nonlinear optical fiber, and within the working range, the cut-off wavelength is less than 1600nm, and the dispersion value of at least one point on the dispersion curve of the high nonlinear optical fiber is not less than 0ps/km/nm; high altitude africaNonlinear coefficient of linear optical fiber not less than 5W -1 km -1 The length of the optical fiber is 100-1000 mm;
the photoelectric detector is an optical fiber coupled photoelectric detector, a photodiode material in the photoelectric detector is InGaAs or Si, and the response bandwidth of the photoelectric detector is not lower than 10MHz.
Furthermore, the output end of the second wavelength division multiplexer is connected with the compression optical fiber by adopting a common transmission optical fiber with the length of 1000-7000 mm, and is used for reducing the pulse width output by the optical fiber amplifier.
A femtosecond laser pulse carrier envelope phase offset frequency detection method is characterized by comprising the following steps:
1) The femtosecond laser pulse is guided into the optical fiber amplifier by the optical fiber to be amplified;
2) Compressing the pulse width of the amplified femtosecond laser pulse to below 200fs;
3) Broadening the compressed femtosecond laser pulse into a super-continuum spectrum signal by using a high-nonlinearity optical fiber;
4) Focusing the supercontinuum signal by using a first optical fiber collimator;
5) A frequency doubling crystal is utilized to enable a part of focused supercontinuum signals to generate frequency doubling signals;
6) And the other part of the focused supercontinuum signal and the frequency doubling signal are coupled into a second optical fiber collimator and guided into a photoelectric detector by an optical fiber, and the photoelectric detector converts the optical signal into an electric signal to be detected, so that the detection of the carrier envelope offset frequency of the femtosecond laser pulse is realized.
Further, the frequency doubling crystal in the step 4) is a periodically polarized magnesium oxide doped lithium niobate crystal, the polarization period range of the lithium niobate crystal is 9-16 μm or 28-34 μm, and the length selection range of the lithium niobate crystal is 1-10 mm.
Compared with the prior art, the invention has the following beneficial effects.
1. The femtosecond laser pulse carrier envelope phase offset frequency detection device simplifies a traditional device for measuring carrier envelope phase offset (CEO) by an interferometer into a linear structure and only comprises detection devices of three devices, namely a first optical fiber collimator, a frequency doubling crystal and a second optical fiber collimator; simultaneously all encapsulate the optical device of above three non-optic fibre in the encapsulation sleeve pipe, only need rationally coil the optic fibre in the detection device, just can go into the box with whole light path encapsulation, encapsulation degree of difficulty greatly reduced has realized detection device's integration.
2. The femtosecond laser pulse carrier envelope phase deviation frequency detection device adopts the structure that the frequency doubling crystal is packaged into the adapter sleeve, the coupling of input and output is realized by the optical fiber collimator, the temperature control of the frequency doubling crystal can be easily realized only by directly controlling the temperature of the whole adapter sleeve, and the temperature control power required by the adapter sleeve is only about 2W.
3. The femtosecond laser pulse carrier envelope phase shift frequency detection method adopted by the invention leads femtosecond laser pulse into an optical fiber amplifier from an optical fiber, compresses the pulse width of the femtosecond laser pulse to be less than 200fs in the optical fiber, widens a supercontinuum signal by using a high nonlinear optical fiber, realizes dispersion compensation by using an input tail fiber of a frequency doubling crystal coupled by the optical fiber, enables a part of supercontinuum signal to generate a frequency doubling signal in the frequency doubling crystal, finally leads the other part of supercontinuum signal and the frequency doubling signal into a photoelectric detector, realizes the detection of the carrier envelope shift frequency of the femtosecond laser pulse, connects all optical devices of the detection device by using optical fibers, realizes the full optical fiber of the optical path of a femtosecond laser pulse CEO signal detection device, has stable optical path, and can avoid maintenance by using a product manufactured by the structure.
Drawings
Fig. 1 is a structural diagram of a femtosecond laser pulse carrier envelope phase offset frequency detection device according to the present invention.
Fig. 2 is an exploded view of the first fiber collimator, frequency doubling crystal and second fiber collimator of the present invention before packaging.
Fig. 3 is a first structural diagram of the first optical fiber collimator, the frequency doubling crystal and the second optical fiber collimator after being packaged.
Fig. 4 is a second structural diagram of the first optical fiber collimator, the frequency doubling crystal and the second optical fiber collimator after being packaged.
In the figure:
100-a first wavelength division multiplexer, 101-a first gain fiber, 102-a second gain fiber, 103-a second wavelength division multiplexer, 104-a compression fiber, 105-a high nonlinear fiber, 106-a first fiber collimator, 107-a frequency doubling crystal, 108-a second fiber collimator, 109-a photodetector, 110-a packaging sleeve, 111-a first pump source, 112-a second pump source, 113-an adapter sleeve.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings, and it is obvious that the described embodiments do not limit the present invention.
As shown in fig. 1, fig. 2 and fig. 3, the femtosecond laser pulse carrier envelope phase offset frequency detection apparatus in this embodiment includes an optical fiber amplifier, a compression optical fiber 104, a high nonlinear optical fiber 105, a frequency doubling device and a photodetector 109, which are sequentially connected by an optical fiber;
the optical fiber amplifier is used for amplifying the received femtosecond laser pulse;
the compression optical fiber 104 is used for compressing the amplified femtosecond laser pulse;
the high nonlinear optical fiber 105 is used for broadening the received compressed femtosecond laser pulses into a super-continuum spectrum signal;
the frequency doubling device comprises a packaging sleeve 110, a first optical fiber collimator 106, a frequency doubling crystal 107 and a second optical fiber collimator 108 which are sequentially arranged in the packaging sleeve 110; the frequency doubling crystal 107 is a periodically polarized magnesium oxide-doped lithium niobate crystal, and the frequency doubling device is used for sequentially focusing, frequency doubling and coupling supercontinuum signals;
the photodetector 109 is used for converting the focused, frequency-doubled and coupled supercontinuum signal into an electric signal to be detected.
An adapter sleeve 113 is arranged outside the frequency doubling crystal 107, the inner diameter of the adapter sleeve 113 is 0.1mm larger than the diagonal of the input section of the frequency doubling crystal, the outer diameter of the adapter sleeve 113 is 0.1mm smaller than the inner diameter of the packaging sleeve 110, and the length of the adapter sleeve 113 is matched with that of the frequency doubling crystal 107;
the shells of the first optical fiber collimator 106 and the second optical fiber collimator 108 are both cylindrical and have the same outer diameter as the adapter sleeve 113;
the material of the adapting sleeve 113 is metal, quartz or ceramic, and the material of the packaging sleeve 110 is metal, quartz or ceramic;
the first gain fiber 101 and the second gain fiber 102 can be directly welded or connected through a common polarization maintaining transmission fiber; the first gain fiber 101 is an erbium-doped or ytterbium-doped polarization-maintaining fiber, and the second gain fiber 102 is an erbium-doped or ytterbium-doped polarization-maintaining fiber. In this example, the lengths of the first gain fiber 101 and the second gain fiber 102 were 1000mm and 2000mm, respectively, and the dispersion values were-27 ps/km/nm and the absorptions were 50dB/m, respectively. The output end of the second wavelength division multiplexer 103 is connected with the compression optical fiber 104 by adopting a 2500mm common transmission optical fiber, and is used for reducing the pulse width output by the optical fiber amplifier.
After the femtosecond laser pulse is input into the amplifier, the laser pulse is amplified after passing through a first wavelength division multiplexer 100, a first gain fiber 101, a second gain fiber 102 and a second wavelength division multiplexer 103 in sequence. The energy required by the amplifier is provided by the first pump source 111 or the second pump source 112. Which are coupled into the fiber amplifier by a first wavelength division multiplexer 100 and a second wavelength division multiplexer 103, respectively. The operating wavelength of the first pump source 111 and the second pump source 112 is 976nm.
The femtosecond laser pulse signal passes through the second wavelength division multiplexer 103 and enters the 4500mm compressed optical fiber 104, and the dispersion of the femtosecond laser pulse signal is 18ps/km/nm. After passing through the compression fiber 104, the femtosecond laser pulse has a width of 63fs.
A femtosecond laser pulse of 63fs enters the highly nonlinear optical fiber 105. The high nonlinear optical fiber 105 has a length of 870mm, belongs to a polarization-maintaining high nonlinear optical fiber, and has a cut-off wavelength of 1300nm in a working range. The dispersion value of the point on the dispersion curve of the high nonlinear optical fiber 105 is ranged from-1.5 to 2ps/km/nm and the nonlinear coefficient is 10.7W in the working range thereof -1 km -1 . The coverage range of the supercontinuum coverage generated by the device is 1010-2060 nm.
The generated supercontinuum enters a first fiber collimator 106 through a 4mm long fiber, and enters a frequency doubling crystal 107 with an adaptive sleeve 113 after focusing. After a part of the focused supercontinuum signal generates frequency multiplication in the frequency multiplication crystal 107, the frequency multiplication crystal and another part of the focused supercontinuum signal are coupled into the second optical collimator 108 together, and are led into the InGaAs photodetector 109 through the transmission optical fiber, and finally a CEO signal is output, wherein the response bandwidth of the InGaAs photodetector 109 is 2.4GHz.
The first optical fiber collimator 106 and the second optical fiber collimator 108 are both made of optical fibers and a single piece of gradient index lens; the rayleigh distance value ranges of the first optical fiber collimator 106 and the second optical fiber collimator 108 are both 0.17-1.8 mm, the pigtails of the first optical fiber collimator 106 and the second optical fiber collimator 108 both adopt polarization maintaining transmission fibers, the length of the polarization maintaining transmission fibers is 4mm, and the polarization maintaining transmission fibers are used for adjusting the dispersion of internal transmission signals; the frequency doubling crystal with the adapter sleeve 113 is a periodically polarized magnesium oxide-doped lithium niobate crystal, the polarization period range of the lithium niobate crystal is 9-16 μm or 28-34 μm, and the length selection range of the lithium niobate crystal is 1-10 mm. In this embodiment, the lithium niobate crystal may have a polarization period of 31 μm and a length of 8mm. For packaging convenience, the housings of the first and second fiber collimators 106 and 108 are cylindrical and have the same diameter of 2.78mm. The three devices can be packaged into a quartz packaging sleeve 110 with an inner diameter of 2.8mm by adding the adapter sleeve 113 with an outer diameter of 2.78mm to the lithium niobate crystal. The distance between the first optical fiber collimator 106 and the adapting sleeve 113 is 0.1-12 mm, and the distance between the adapting sleeve 113 and the second optical fiber collimator 108 is 0.1-12 mm; during manufacturing, the devices in the cannula are fixed by using epoxy resin or silicone adhesive.
In this example, the design parameters of the fiber collimator depend on the frequency doubling crystal. According to the length l =8mm of the frequency doubling crystal, the rayleigh distance of the light beam in the crystal can be calculated to be r = l/2.83/2=1.413mm. Thus, the beam waist radius of the light beam is known to be omega =(rλ/π) 1/2 And =30.3 μm, where pi is the circumferential ratio and λ is the wavelength, taking a value of 2.06 μm. The corresponding optical fiber collimator can be manufactured according to the calculation result.
The cross section of the through hole inside the package sleeve 110 in this embodiment is circular, and may also be rectangular.
In another embodiment, as shown in fig. 4, the package sleeve 110 may also adopt a half-cylinder sleeve structure, and the first fiber collimator 106, the frequency doubling crystal 107 and the second fiber collimator 108 are clamped.
In this embodiment, a femtosecond laser pulse carrier envelope phase offset frequency detection method includes the following steps:
1) First, femtosecond laser pulses are amplified in a polarization maintaining, positively dispersive fiber amplifier. After amplification, the pulse single pulse energy reaches more than 1 nJ.
2) The amplified femtosecond laser pulses reenter the negative dispersion compression fiber 104, so that the pulse width is 60fs.
3) The compressed femtosecond laser pulses enter the polarization-maintaining high nonlinear optical fiber 105 to generate a supercontinuum, and the spectral coverage range of the supercontinuum exceeds one octave.
4) The supercontinuum signal enters a first fiber collimator 106 and is focused into a frequency doubling crystal 107.
5) A frequency doubling crystal 107 is utilized to enable a part of focused supercontinuum signals to generate frequency doubling signals;
6) The other part of the focused supercontinuum signal and the frequency doubling signal are coupled into a second optical fiber collimator 108 together, and are guided into an InGaAs photodetector 109 through a transmission optical fiber, and finally a CEO signal is output.
The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A femtosecond laser pulse carrier envelope phase offset frequency detection device is characterized in that:
the device comprises an optical fiber amplifier, a compression optical fiber (104), a high nonlinear optical fiber (105), a frequency doubling device and a photoelectric detector (109) which are sequentially connected by optical fibers;
the optical fiber amplifier is used for amplifying the received femtosecond laser pulse;
the compression optical fiber (104) is used for compressing the amplified femtosecond laser pulse;
the high nonlinear optical fiber (105) is used for broadening the received compressed femtosecond laser pulses into a super-continuum signal;
the frequency doubling device comprises a packaging sleeve (110), a first optical fiber collimator (106), a frequency doubling crystal (107) and a second optical fiber collimator (108) which are sequentially arranged in the packaging sleeve (110); the frequency doubling crystal (107) is a periodically polarized magnesium oxide doped lithium niobate crystal; the frequency doubling device is used for sequentially focusing, generating frequency doubling and coupling the supercontinuum signals;
the photoelectric detector (109) is used for converting the focused, frequency-doubled and coupled supercontinuum signal into an electric signal to be detected.
2. The femtosecond laser pulse carrier envelope phase offset frequency probe device of claim 1, wherein: an adaptive sleeve (113) is arranged outside the frequency doubling crystal (107), the inner diameter of the adaptive sleeve (113) is 0-0.2 mm larger than the diagonal of the input section of the frequency doubling crystal, the outer diameter of the adaptive sleeve is 0-0.2 mm smaller than the inner diameter of the packaging sleeve (110), and the length of the adaptive sleeve (113) is matched with that of the frequency doubling crystal (107);
the shells of the first optical fiber collimator (106) and the second optical fiber collimator (108) are both cylindrical and have the same outer diameter as the adapter sleeve (113);
the material of the adaptation sleeve (113) is metal, quartz or ceramic, and the material of the packaging sleeve (110) is metal, quartz or ceramic.
3. The femtosecond laser pulse carrier envelope phase offset frequency probe device of claim 2, wherein: the range of the polarization period of the lithium niobate crystal is 9-16 μm or 28-34 μm, and the length of the lithium niobate crystal is 1-10 mm.
4. The femtosecond laser pulse carrier envelope phase offset frequency probe device according to any one of claims 1 to 3, wherein: the first optical fiber collimator (106) and the second optical fiber collimator (108) are both composed of an optical fiber and a gradient index lens, or composed of an optical fiber and one or a pair of aspherical mirrors; the Rayleigh distance value range of the first optical fiber collimator (106) and the second optical fiber collimator (108) is 0.17-1.8 mm;
and the tail fibers of the first optical fiber collimator (106) and the second optical fiber collimator (108) both adopt polarization-maintaining transmission fibers, and the length of each polarization-maintaining transmission fiber is 1-35 mm and is used for adjusting the dispersion of internal transmission signals.
5. The femtosecond laser pulse carrier envelope phase offset frequency probe device of claim 4, wherein: the optical fiber amplifier comprises a first pumping source (111), a second pumping source (112), a first wavelength division multiplexer (100), a first gain optical fiber (101), a second gain optical fiber (102) and a second wavelength division multiplexer (103), wherein the first wavelength division multiplexer, the first gain optical fiber, the second gain optical fiber and the second wavelength division multiplexer are sequentially connected through optical fibers;
the pump light of the optical fiber amplifier is generated by a first pump source (111) or a second pump source (112), and is input into the first wavelength division multiplexer (100) through a first polarization-maintaining single-mode optical fiber by the first pump source (111), or is input into the second wavelength division multiplexer (103) through a second polarization-maintaining single-mode optical fiber by the second pump source (112);
the lengths of the first gain optical fiber (101) and the second gain optical fiber (102) are both 500-5000 mm, the dispersion near the working wavelength is-60-0 ps/km/nm, and the absorption is 5-1000 dB/m.
6. The femtosecond laser pulse carrier envelope phase offset frequency probe device of claim 5, wherein: the compressed optical fiber (104) has a dispersion of 18ps/km/nm and is used for reducing the width of the femtosecond laser pulse to a value not higher than that of the dispersionGreater than 200fs; the high nonlinear optical fiber (105) adopts a photonic crystal fiber or a polarization-maintaining high nonlinear optical fiber, the cut-off wavelength of the high nonlinear optical fiber is less than 1600nm in the working range, and the dispersion value of at least one point on the dispersion curve of the high nonlinear optical fiber (105) is not less than 0ps/km/nm; the nonlinear coefficient of the highly nonlinear optical fiber (105) is not less than 5W -1 km -1 The length of the high nonlinear optical fiber (105) is 100-1000 mm;
the photoelectric detector (109) is an optical fiber coupled photoelectric detector, a material of a photodiode in the photoelectric detector (109) is InGaAs or Si, and a response bandwidth of the photoelectric detector is not lower than 10MHz.
7. The femtosecond laser pulse carrier envelope phase offset frequency probe device according to claim 5, wherein: the output end of the second wavelength division multiplexer (103) is connected with the compression optical fiber (104) by adopting a common transmission optical fiber with the thickness of 1000-7000 mm.
8. A femtosecond laser pulse carrier envelope phase offset frequency detection method, which is based on the femtosecond laser pulse carrier envelope phase offset frequency detection device of any one of claims 1 to 7, and comprises the following steps:
1) The femtosecond laser pulse is guided into the optical fiber amplifier by the optical fiber to be amplified;
2) Compressing the pulse width of the amplified femtosecond laser pulse to below 200fs;
3) Broadening the compressed femtosecond laser pulses into a supercontinuum signal by using a high-nonlinearity optical fiber (105);
4) Focusing the supercontinuum signal with a first fiber collimator (106);
5) A frequency doubling crystal (107) is used for enabling a part of the focused supercontinuum signal to generate a frequency doubling signal;
6) The other part of the focused supercontinuum signal and the frequency doubling signal are coupled into a second optical fiber collimator (108) together, and the optical fiber leads into a photoelectric detector (109), the photoelectric detector (109) converts the optical signal into an electric signal to be detected, and the detection of the carrier envelope offset frequency of the femtosecond laser pulse is realized.
9. The femtosecond laser pulse carrier envelope phase offset frequency detection method according to claim 8, wherein the frequency doubling crystal (107) in the step 4) is a periodically polarized magnesium oxide-doped lithium niobate crystal, the polarization period range of the lithium niobate crystal is 9-16 μm or 28-34 μm, and the length selection range of the lithium niobate crystal is 1-10 mm.
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