CN220628475U - Chirped pulse amplifying device based on spectrum modulation - Google Patents

Abstract

The application provides a chirped pulse amplification device based on spectrum modulation, which comprises a seed source, a widening component, a spectrum modulation mechanism, a power amplification module and a pulse compression module; the stretching assembly is arranged on an emergent light path of the seed source and is used for stretching the passing laser pulse and outputting a stretching pulse; the spectrum modulation mechanism comprises a first gain optical fiber optical path and a second gain optical fiber optical path, the beam splitting of the widening component is connected with the first gain optical fiber optical path and the second gain optical fiber optical path, the first gain optical fiber optical path and the second gain optical fiber optical path are coupled and connected to the power amplification module, the beam splitting of the widening pulse enters the first gain optical fiber optical path and the second gain optical fiber optical path, the widening pulse is coupled and phase interference to form a modulation pulse and is output to the power amplification module, and the spectrum of the modulation pulse is in a middle depression shape and two side bulge shape. The chirped pulse amplifying device based on spectrum modulation can output high-power and narrow-pulse-width femtosecond laser, and the whole structure is simpler and more compact.

Description

Chirped pulse amplifying device based on spectrum modulation

Technical Field

The application belongs to the technical field of lasers, and particularly relates to a chirped pulse amplification device based on spectrum modulation.

Background

In order to obtain a high-power narrow femtosecond laser, the stretched pulse needs to be amplified multiple times by using a high-gain optical fiber, and the stretched laser needs to be compressed to a near diffraction limit pulse width by using a compressor. However, when the pulse laser beam is amplified by the high-gain optical fiber, the laser pulse is affected by the spectrum narrowing due to the non-uniformity of the spectrum gain curve related to the rare earth doped gain medium material in the optical fiber, so that the compressed pulse is difficult to reach the fourier transform limit narrow pulse width.

The self-phase modulation effect in the ultra-short pulse amplification process can be used for widening the pulse spectrum, and the method can effectively overcome the influence of spectrum narrowing caused by gain narrowing on the compressed output narrow pulse width. However, in order to cause the laser to produce a spectral broadening induced by phase modulation, the pulse width must be precompressed below hundred femtoseconds and the energy lifted to the nJ level by pre-amplification before amplification, which places stringent requirements on the design of the laser system and increases complexity.

The shaping of the pulse beam by adopting the spectrum modulation method is a very convenient and effective method for inhibiting the spectrum narrowing effect caused by gain narrowing, and is very suitable for being applied to a high-power and narrow-pulse width femtosecond pulse laser system.

The current spectrum modulation means mostly adopts free space component matching, corresponding physical parameters are required to be designed, and the difficulty of accurate adjustment is high, so that the complexity of the system is improved, and the compactness of a laser system is reduced.

Disclosure of Invention

The embodiment of the application provides a chirp pulse amplifying device based on spectrum modulation, which can output high-power and narrow-pulse-width femtosecond laser and has simpler and more compact overall structure.

The technical scheme adopted by the embodiment of the application is as follows: the chirped pulse amplifying device based on spectrum modulation comprises a seed source, a widening component, a spectrum modulation mechanism, a power amplifying module and a pulse compression module;

the seed source is used for generating laser pulses;

the stretching assembly is arranged on an emergent light path of the seed source and is used for forming a space light path, stretching the passing laser pulse and outputting a stretching pulse;

the spectrum modulation mechanism comprises a first gain optical fiber optical path and a second gain optical fiber optical path, the widening component beam-splitting is connected with the input end of the first gain optical fiber optical path and the input end of the second gain optical fiber optical path, the output end of the first gain optical fiber optical path and the output end of the second gain optical fiber optical path are coupled and connected to the power amplification module, the widening pulse beam-splitting enters the first gain optical fiber optical path and the second gain optical fiber optical path, after phase delay and gain, the widening pulse beam-splitting is coupled and phase interference forms modulation pulse and outputs the modulation pulse to the power amplification module, and the spectrum of the modulation pulse is in a middle depression shape and two side bulge shape;

the power amplification module is used for carrying out power amplification and energy extraction on the modulation pulse and outputting a high-energy pulse;

the pulse compression module is connected with the power amplification module and is used for compressing and outputting the high-energy pulse.

Further, the spectrum modulation mechanism further comprises a first coupler and a second coupler, wherein the first coupler is connected with the stretching assembly, and the second coupler is connected with the power amplification module;

the first gain optical fiber path comprises a first passive optical fiber and a first gain amplification component, one end of the first passive optical fiber is connected with the first coupler, the other end of the first passive optical fiber is connected with the first gain amplification component, and the first gain amplification component is connected with the second coupler;

the second gain optical fiber path comprises a second passive optical fiber and a second gain amplification component, one end of the second passive optical fiber is connected with the first coupler, the other end of the second passive optical fiber is connected with the second gain amplification component, the second gain amplification component is connected with the second coupler, and the lengths of the second passive optical fiber and the first passive optical fiber are unequal.

Further, the spectrum modulation mechanism comprises an isolator, a third coupler, a third passive optical fiber, a fourth passive optical fiber and a third gain amplification component, wherein the lengths of the third passive optical fiber and the fourth passive optical fiber are unequal;

the isolator is provided with a first interface, a second interface and a third interface, the first interface is connected with the widening component, the second interface is connected with the third coupler, and the third interface is connected with the power amplification module; the isolator is provided with a first state and a second state, the first interface is communicated with the second interface in the first state, and the third interface is disconnected with the first interface and the second interface; in the second state, the second interface is communicated with the third interface, and the first interface is disconnected with the second interface and the third interface;

the third coupler is connected with one end of the third gain amplifying assembly through the third passive optical fiber, and the third coupler is connected with the other end of the third gain amplifying assembly through the fourth passive optical fiber to form a loop, so that the first gain optical fiber optical path and the second gain optical fiber optical path with opposite directions are formed.

Further, the third gain amplification assembly comprises a third active optical fiber, a third pump source and a third wavelength division multiplexer, the third passive optical fiber, the active optical fiber, the wavelength division multiplexer and the fourth passive optical fiber are sequentially connected, and the third pump source is connected with the third wavelength division multiplexer.

Further, the isolator is a circulator.

Further, the stretching assembly comprises a height-adjusting lens group, a stretcher, a tele lens, a first reflecting mirror and a second reflecting mirror;

the height-adjusting mirror group, the stretcher, the tele lens and the first reflecting mirror are sequentially arranged, the second reflecting mirror is arranged between the height-adjusting mirror group and the stretcher, a preset height difference is arranged between the second reflecting mirror and the height-adjusting mirror group, the height-adjusting mirror group is provided with a gap, the height-adjusting mirror group can be used for reflecting the passing laser pulse after adjusting the height, and the stretcher is used for stretching the incident laser pulse;

after the laser pulse passes through the gap of the height-adjusting mirror group along the space light path, repeating the reflection between the height-adjusting mirror group and the first reflecting mirror for a plurality of times, enabling the laser pulse to pass through the stretcher and the tele lens in sequence for a plurality of times in the forward direction and pass through the tele lens and the stretcher in sequence for a plurality of times in the reverse direction, and finally enabling the laser pulse to be transmitted to the second reflecting mirror from the stretcher, and outputting the stretched pulse to the power amplifying module after being reflected by the second reflecting mirror;

wherein the laser pulse passes through the center of the tele lens without passing through the center of the tele lens.

Further, the stretching assembly further comprises a multidimensional adjusting frame, and the stretcher is arranged on the multidimensional adjusting frame so as to adjust the included angle and the relative position of the laser pulse input by the seed source and the stretcher.

Further, the power amplification module comprises an optical fiber pre-amplifier and an optical fiber main amplifier, wherein one end of the optical fiber pre-amplifier is connected with the spectrum modulation mechanism, the other end of the optical fiber pre-amplifier is connected with one end of the optical fiber main amplifier, and the other end of the optical fiber main amplifier is connected with the pulse compression device;

the high-energy pulse comprises a first high-energy pulse and a second high-energy pulse, the optical fiber pre-amplifier is used for carrying out power amplification and energy extraction on the broadening pulse and outputting the first high-energy pulse, and the optical fiber main amplifier is used for carrying out power amplification and energy extraction on the first high-energy pulse and outputting the second high-energy pulse.

Further, the optical fiber pre-amplifier is a cascaded single-cladding polarization-maintaining active optical fiber amplifier.

Further, the optical fiber main amplifier is a cascaded double-clad large-mode-area optical fiber amplifier.

The chirp pulse amplification device based on spectrum modulation has the beneficial effects that: the chirped pulse amplifying device based on spectrum modulation is provided with the stretching assembly and the spectrum modulation mechanism, laser pulses sent by the seed source are stretched by the stretching assembly and then input into the spectrum modulation mechanism, the spectrum modulation mechanism is used for splitting and inputting the stretched pulses into the first gain optical fiber path and the second gain optical fiber path, phase delay and gain are generated in the two optical paths, and the coupling interference is modulated pulses and output. Because the spectrum modulation mechanism of the embodiment of the application adopts two different gain fiber optical paths to couple pulse gain, phase interference is generated to modulate pulse spectrum, and the whole structure is simpler and more compact.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required for the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic connection diagram of a chirped pulse amplifying device based on spectrum modulation according to an embodiment of the present application;

FIG. 2 is a schematic structural diagram of a stretching assembly according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a first path of a stretching assembly provided in an embodiment of the present application;

FIG. 4 is a schematic diagram of one embodiment of a spectrum modulation mechanism provided in an embodiment of the present application;

FIG. 5 is a schematic diagram of another embodiment of a spectrum modulation mechanism according to the embodiments of the present application;

fig. 6 is a schematic diagram before and after spectrum modulation according to an embodiment of the present application.

Wherein, each reference sign in the figure:

10. a seed source;

20. a stretching assembly; 21. height-adjusting lens group; 22. a stretcher; 23. a tele lens; 24. a first mirror; 25. a second mirror; 26. a multidimensional adjusting frame;

30. a spectrum modulation mechanism; 31. a first gain fiber optic path; 311. a first passive optical fiber; 312. a first gain amplifying component; 3121. a first active optical fiber; 3122. a first pump source; 3123. a first wavelength division multiplexer; 32. a second gain fiber optic path; 321. a second passive optical fiber; 322. a second gain amplifying component; 3221. a second active optical fiber; 3222. a second pump source; 3223. a second wavelength division multiplexer; 33. a first coupler; 34. a second coupler; 35. an isolator; 351. a first interface; 352. a second interface; 353. a third interface; 36. a third coupler; 37. a third passive optical fiber; 38. a fourth passive optical fiber; 39. a third gain amplifying component; 391. a third active optical fiber; 392. a third pump source; 393. a third wavelength division multiplexer;

40. a power amplification module; 41. an optical fiber pre-amplifier; 411. a first high energy pulse; 42. an optical fiber main amplifier; 421. a second high energy pulse;

50. and a pulse compression module.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the present application and simplify description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and therefore should not be construed as limiting the present application.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

Referring to fig. 1, a chirped pulse amplifying device based on spectral modulation according to an embodiment of the present application will now be described. The chirped pulse amplification apparatus based on spectral modulation provided in the embodiments of the present application may include a seed source 10, a stretching assembly 20, a spectral modulation mechanism 30, a power amplification module 40, and a pulse compression module 50.

Wherein the seed source 10 is used to generate laser pulses. Seed source 10 may be a fiber mode-locked seed source, an NPR mode-locked seed source, a SESAM mode-locked seed source, a figure 8 cavity mode-locked seed source, or the like. The optical fiber mode-locked oscillator of a large group can be purchased, a pulse beam with a wide spectral bandwidth and a middle wavelength of 1030nm can be output, and the pulse beam is driven by a PCB circuit driving module, so that the regulation and control are convenient;

referring to fig. 1 and 2, a stretching assembly 20 is disposed on an optical path of the seed source 10, and the stretching assembly 20 is configured to form a spatial optical path, stretch the passing laser pulse, and output a stretched pulse. The stretching assembly 20 stretches the laser pulses to a pulse width. The laser pulses generated by the seed source 10 may enter the spatial light path formed by the stretching assembly 20 and introduce a positive dispersion into the laser pulses during propagation for stretching.

Referring to fig. 2, 4 and 5, the spectrum modulation mechanism 30 may include a first gain fiber optical path 31 and a second gain fiber optical path 32, the widening component 20 is connected to the input end of the first gain fiber optical path 31 and the input end of the second gain fiber optical path 32 in a beam splitting manner, the output end of the first gain fiber optical path 31 and the output end of the second gain fiber optical path 32 are coupled to the power amplification module 40, the widened pulse is split into the first gain fiber optical path 31 and the second gain fiber optical path 32, and after phase delay and gain, the widened pulse is coupled and phase interfered to form a modulated pulse and output to the power amplification module 40, and the spectrum of the modulated pulse is in a middle depression and two side protrusions.

The beam splitting connection of the stretching assembly 20 to the input end of the first gain optical fiber path 31 and the input end of the second gain optical fiber path 32 may be specifically that the stretching assembly 20 is connected to the input end of the first gain optical fiber path 31 and the input end of the second gain optical fiber path 32 through a beam splitter or an optical fiber coupler at the same time, and as long as the stretching assembly can split the stretching pulse into two beams of pulses, the two beams of pulses are respectively input into the connection modes of different gain optical fiber paths, the beam splitting connection may be called.

The spectrum modulation mechanism 30 has two gain fiber optical paths, when the stretched pulse output by the stretching component 20 reaches the spectrum modulation mechanism 30, the stretched pulse can be split into two beams of laser, and the two beams of laser are respectively input into the first gain fiber optical path 31 and the second gain fiber optical path 32, are respectively coupled and interfered after being subjected to phase delay and gain, and the two beams of laser have different phases after the first gain fiber optical path 31 and the second gain fiber optical path 32 obtain phase delay, so that the spectrum of the modulated pulse output after interference is modulated, and the spectrum of the pulse output after modulation is in a middle depression and two side humps, referring to fig. 6, namely a saddle-shaped spectrum. The time domain spectrum of the laser pulse is modulated into a saddle shape, so that the influence of gain narrowing on a pulse beam in the subsequent amplifying process is reduced, the spectrum narrowing is restrained, the gain bandwidth is expanded, the system keeps wider spectrum pulse output, and the nonlinear effect in the system is reduced.

Wherein the first gain fiber optical path 31 and the second gain fiber optical path 32 may have different lengths of passive fibers, and different phase delays are formed after the laser beam is split into the different lengths of passive fibers.

Referring to fig. 1, the outputted modulated pulse then enters a power amplification module 40, and the power amplification module 40 is used for power amplifying and energy extracting the modulated pulse and outputting a high-energy pulse. The stretched, modulated laser pulses are subjected to high efficiency, high energy extraction by a power amplification module, and then dispersion compensated compressed output by a pulse compression module 50. The pulse compression module 50 is connected to the power amplification module 40, and the pulse compression module 50 is used for compressing and outputting high-energy pulses.

The chirped pulse amplifying device based on spectrum modulation in this embodiment is provided with the stretching component 20 and the spectrum modulation mechanism 30, after the laser pulse sent by the seed source 10 is stretched by the stretching component 20, the laser pulse is input into the spectrum modulation mechanism 30, the stretched pulse is split by the spectrum modulation mechanism 30 and input into the first gain optical fiber path 31 and the second gain optical fiber path 32, after the two optical paths are respectively gain-enhanced, the coupling interference is modulated pulse and output, because the spectrum of the modulated pulse is middle-depressed and two sides are humped, the spectrum narrowing effect of the pulse caused by gain narrowing in the subsequent amplifying process of the power amplifying module 40 can be effectively inhibited, the spectrum width of the output pulse is widened, the pulse is amplified by the power amplifying module 40, and the pulse is compressed to be shorter by the pulse compressing module 50, and the high-power femtosecond narrow pulse laser is output. Because the spectrum modulation mechanism 30 in the embodiment of the application adopts two different gain fiber optical paths to couple pulse gain, phase interference is generated to modulate the pulse spectrum, and the whole structure is simpler and more compact.

The structure of the spectrum modulation mechanism 30 may be: referring to fig. 4, the spectral modulation mechanism 30 may further include a first coupler 33 and a second coupler 34, the first coupler 33 being coupled to the stretching assembly 20, the second coupler 34 being coupled to the power amplification module 40.

The first coupler 33 is capable of splitting the stretched pulse output from the stretching assembly 20 into two beams to be input into the first gain fiber optical path 31 and the second gain fiber optical path 32, respectively.

The second coupler 34 can couple the phase-delayed and gain pulses output from the first gain fiber optical path 31 and the second gain fiber optical path 32 to interfere the two laser beams to generate the spectral modulation.

Referring to fig. 4, the first gain fiber optical path 31 may include a first passive fiber 311 and a first gain amplifying component 312, where one end of the first passive fiber 311 is connected to the first coupler 33, and the other end is connected to the first gain amplifying component 312, and the first gain amplifying component 312 is connected to the second coupler 34. The first laser light split by the first coupler 33 is input from the first passive optical fiber 311 to the first gain amplifying element 312, and then input to the second coupler 34. The first laser beam is phase-delayed while passing through the first passive optical fiber 311, and gain-amplified while passing through the first gain amplifying element 312, thereby increasing power.

Referring to fig. 4, the second gain fiber optical path 32 may include a second passive fiber 321 and a second gain amplification component 322, where one end of the second passive fiber 321 is connected to the first coupler 33, the other end is connected to the second gain amplification component 322, the second gain amplification component 322 is connected to the second coupler 34, and the lengths of the second passive fiber 321 and the first passive fiber 311 are unequal. The second laser light split by the first coupler 33 is input from the second passive optical fiber 322 to the second gain amplification block 322, and then input to the second coupler 34. The second laser beam is phase-delayed while passing through the second passive optical fiber 321, and gain-amplified while passing through the second gain amplification block 322, thereby increasing power.

Since the lengths of the second passive optical fiber 321 and the first passive optical fiber 311 are different, the phase delay of the two laser beams after passing through the passive optical fibers with different lengths is different, so that interference occurs when the second coupler 34 is coupled, the light output after interference is modulated, and the spectrum of the pulse output after modulation is in a shape of middle depression and two sides bulge, namely a saddle-shaped spectrum. The optical path modulation of the optical fiber is simpler, and only the length of the passive optical fiber needs to be controlled.

Referring to fig. 4, the first gain amplifying assembly 312 may include a first active optical fiber 3121, a first pump source 3122, and a first wavelength division multiplexer 3123, the first coupler 33, the first passive optical fiber 311, the first active optical fiber 3121, the first wavelength division multiplexer 3123, and the second coupler 34 being sequentially connected, the first pump source 3122 being coupled with the wavelength division multiplexer. The split first beam is amplified by the gain of the first passive optical fiber 311 and the first active optical fiber 3121 and pumped by the first pump source 3122 coupled by the first wavelength division multiplexer 3123. Wherein, the first pump 3122 pumps the light beam in the first gain optical fiber path 31 to realize the population inversion in the first gain optical fiber path 31; the first wavelength division multiplexer 3123 couples the pump light and the signal light into the first active optical fiber 3121 for power amplification, and the difference in length between the first passive optical fiber 311 and the second passive optical fiber 321 can increase the phase delay of the light beam propagation process.

Referring to fig. 4, the second gain amplification assembly 322 may include a second active optical fiber 3221, a second pump source 3222, and a second wavelength division multiplexer 3223, the first coupler 33, the second passive optical fiber 321, the second active optical fiber 3221, the second wavelength division multiplexer 3223, and the second coupler 34 are sequentially connected, and the second pump source 3222 is coupled to the wavelength division multiplexer. The separated second beam of light is amplified by the gain of the second passive optical fiber 321 and the second active optical fiber 3221, and pumped by the second pump source 3222 coupled through the second wavelength division multiplexer 3223. The second pump 3222 pumps the light beam in the second gain fiber optical path 32 to realize the population inversion in the second gain fiber optical path 32; the second wavelength division multiplexer 3223 couples the pump light and the signal light into the active optical fiber for power amplification, and the difference in length between the first passive optical fiber 311 and the second passive optical fiber 321 can increase the phase delay of the light beam propagation process.

Wherein the first coupler 33 and the second coupler 34 may be 50:50 fiber optic couplers.

Alternatively, the structure of the spectrum modulation mechanism 30 may be: referring to fig. 5, the spectral modulation mechanism 30 may include an isolator 35, a third coupler 36, a third passive optical fiber 37, a fourth passive optical fiber 38, and a third gain amplification assembly 39, the third passive optical fiber 37 and the fourth passive optical fiber 38 being unequal in length.

Referring to fig. 5, the isolator 35 is provided with a first interface 351, a second interface 352 and a third interface 353, the first interface 351 is connected to the stretching assembly 20, the second interface 352 is connected to the third coupler 36, and the third interface 353 is connected to the power amplifying module 40; the isolator 35 has a first state in which the first interface 351 is connected to the second interface 352 and a second state in which the third interface 353 is disconnected from the first and second interfaces 351, 352; in the second state, the second interface 352 is connected to the third interface 353, and the first interface 351 is disconnected from the second and third interfaces 352 and 353. Through the switching of the first state and the second state, different interfaces can be connected and disconnected, so that different lights which are isolated, and mutual interference is avoided. For example, in the first state, laser light may enter from the first interface 351, exit from the second interface 352, and not be output to the third interface 353. In the second state, laser light may enter from the second interface 352 so that the third interface 353 exits without being output to the first interface 351. Wherein the isolator 35 may be a circulator.

The third coupler 36 is connected to one end of the third gain amplifying element 39 through the third passive optical fiber 37, and the third coupler 36 is connected to the other end of the third gain amplifying element 39 through the fourth passive optical fiber 38 to form a loop, thereby forming the first gain optical fiber path 31 and the second gain optical fiber path 32 which are opposite in direction.

I.e. an optical circuit is formed in which two different directions are a first gain fiber optical path 31 and a second gain fiber optical path 32, respectively.

Referring to fig. 5, the stretched pulse enters the isolator 35 from the first interface 351, and is input to the third coupler 36 from the second interface 352. The third coupler 36 couples the two laser beams separated by the spread pulse. The first gain fiber path 31 is: the first laser beam is input from the third passive optical fiber 37, passes through the third gain amplification block 39, and returns from the fourth passive optical fiber 38 to the third coupler 36. The second gain fiber path 32 is: the second laser beam is input from the fourth passive optical fiber 38, passes through the third gain amplification block 39, and returns from the third passive optical fiber 37 to the third coupler 36.

The directions of the two laser beams are opposite, and a ring loop is formed. However, since the lengths of the third passive optical fiber 37 and the fourth passive optical fiber 38 are different, the phases of the two laser beams before passing through the third gain amplification group are different, and finally the phases of the two laser beams returning to the third coupler 36 are still different, interference occurs due to the different phases after coupling, and the optical beams are modulated, so as to form modulation pulses.

By adopting the optical fiber loop, the third coupler 36, the third passive optical fiber 37, the fourth passive optical fiber 38, and the third gain amplification module 39 can be reused, and the equipment cost can be reduced.

The spectrum modulation mechanism 30 can be used as a method of modulating the spectrum of the saturated absorber throughout the spectrum modulation process. The spectral notch at the central wavelength can be realized by adjusting the pump light power, the optical fiber gain and length, the effective nonlinear coefficient of the optical fiber and the coupling ratio of the coupler in the spectral modulation mechanism 30, adjusting the transmissivity and reflectivity of the pulse light beam reversely output to the optical fiber system by the coupler, and after the pulse light beam interacts with the Gaussian pulse light beam, the overall spectrum can be modulated into a saddle shape.

Wherein the third coupler 36 may be a 50:50 fiber optic coupler.

Referring to fig. 5, the third gain amplification assembly 39 may include a third active optical fiber 391, a third pump source 392, and a third wavelength division multiplexer 393, with the third passive optical fiber 37, the active optical fiber, the wavelength division multiplexer, and the fourth passive optical fiber 38 being connected in sequence, the third pump source 392 being connected to the third wavelength division multiplexer 393. Since one end of the third passive optical fiber 37 and one end of the fourth passive optical fiber 38 are connected to the third coupler 36, a loop is formed. The third pump source 392 pumps the light beams passing through in two directions, so as to realize the inversion of the particle number in the optical fiber path; the third wavelength division multiplexer 393 couples the pump light and the signal light into the third active optical fiber 391 for power amplification, and the length difference between the third passive optical fiber 37 and the fourth passive optical fiber 38 can increase the phase delay of the light beam propagation process.

Referring to fig. 2 and 3, the stretcher assembly 20 may include a set of height adjustment mirrors 21, a stretcher 22, a tele lens 23, a first mirror 24, and a second mirror 25.

The height-adjusting mirror group 21, the stretcher 22, the tele lens 23 and the first reflecting mirror 24 are sequentially arranged, the second reflecting mirror 25 is arranged between the height-adjusting mirror group 21 and the stretcher 22, a preset height difference is arranged between the second reflecting mirror 25 and the height-adjusting mirror group 21, the height-adjusting mirror group 21 is provided with a gap for laser to pass through, the height-adjusting mirror group 21 can adjust the height of incident laser pulses and then reflect the laser pulses, and the stretcher 22 is used for stretching the incident laser pulses.

The height-adjusting mirror set 21 is also called a climbing mirror, and can reflect an incident light beam back after changing the height, and is usually two reflecting mirrors arranged at 90 degrees, and a gap is reserved between the two reflecting mirrors for the light beam to pass through. I.e. the laser light may pass through the height-adjusting mirror group 21 from the gap or the laser light may be irradiated onto the reflecting mirror plate of the height-adjusting mirror group 21 to be reflected after being changed in height.

For stretcher 22, laser pulse stretching is performed as light passes forward through stretcher 22, and laser pulse stretching is performed as light passes backward through stretcher 22. The stretcher 22 may be a Ma Dingna-z stretcher 22, an ohexa stretcher 22, a fiber bragg grating, a prism pair, a volume grating (VBG), or the like, and the stretcher 20 introduces a dispersion amount into the system. It should be noted that, using different dispersive elements as the stretcher 22 of the system may generate different dispersion chirp effects on the laser pulse, and when in use, it is necessary to calculate each parameter such as the size of the stretcher 22 needed by each device to inversely calculate the dispersion amount introduced into the system, so as to match the overall dispersion amount of the system, which may include the final compression device.

Referring to fig. 2 and 3, after the laser pulse passes through the gap of the height-adjusting mirror group 21 along the spatial light path, the laser pulse is repeatedly reflected between the height-adjusting mirror group 21 and the first reflecting mirror 24, the laser pulse passes through the stretcher 22 and the tele lens 23 in turn in a forward direction, passes through the tele lens 23 and the stretcher 22 in turn in a reverse direction, and finally is reflected by the stretcher 22 to the second reflecting mirror 25 and is output to the power amplifying module 40 via the second reflecting mirror 25.

That is, in the spatial light path, the input laser pulse first passes through the gap of the height-adjusting mirror group 21, then sequentially passes through the stretcher 22 and the tele lens 23, reaches the first reflecting mirror 24 and is reflected, then reversely sequentially passes through the tele lens 23 and the stretcher 22, reaches the height-adjusting mirror group 21, climbs up at the height-adjusting mirror group 21 and is reflected again. The previous path is repeated, namely sequentially passes through the stretcher 22 and the tele lens 23, reaches the first reflecting mirror 24 and is reflected, then reversely sequentially passes through the tele lens 23 and the stretcher 22, reaches the height adjusting mirror group 21, climbs up at the height adjusting mirror group 21 and is reflected again. Such a number of cycles. Until the laser pulse is emitted from the stretcher 22 to the second mirror 25, the laser pulse is reflected by the second mirror 25 and the stretched pulse is output to the power amplification module 40. Wherein the laser pulse does not pass through the center of the tele lens 23 as it passes through the tele lens 23.

That is, when the laser pulse propagates along the spatial light path, it is first incident on the stretcher 22 (forward incident), and diffracts, and since the refractive indexes of the light beams with different frequencies passing through the stretcher 22 are different, the diffraction angles are different, so that the pulse beam spreads in the spatial time domain to form a stripe-shaped light spot (i.e., the laser pulse passes through the stretcher 22 forward). The strip-shaped light spot continuously passes through the bifocal lens 23 and is micro-focused into a parallel light beam to be irradiated on a reflecting mirror (from divergence to parallelism), then is reflected by the reflecting mirror and reversely passes through the bifocal lens 23 to be gathered, and is incident on the stretcher 22, and at the moment, reversely enters the stretcher 22, and the light beam is stretched into a punctiform light spot. Since the light beam does not pass through the center of the tele lens 23 when passing through the tele lens 23 twice, the light beam entering the tele lens 23 for the first time and the light beam reversely emitted from the tele lens 23 for the second time have a height difference, so that the punctiform light spots deviate from the gap of the height-adjusting lens group 21 after being emitted from the stretcher 22, and the light beam strikes the reflecting lens of the height-adjusting lens group 21 to obtain climbing and reflection.

Referring to fig. 2 and 3, the light beam reflected by the height-adjusting mirror group 21 is continuously widened by the stretcher 22, micro-focused by the tele lens 23, reflected by the reflecting mirror, micro-gathered by the tele lens 23, and formed again into a height difference, continuously incident on the stretcher 22, stretched, and re-hit on the height-adjusting mirror group 21. The above paths are repeated until the light beam crosses the preset height difference between the second reflecting mirror 25 and the height-adjusting mirror group 21 in height due to the accumulation of the plurality of height differences, the laser pulse coming out of the stretcher 22 irradiates on the second reflecting mirror 25, is reflected by the second reflecting mirror 25, and is output and introduced with chromatic dispersion, namely, the stretched punctiform facula. The number of repetitions of the first path 26 may be controlled by setting the size of the height-adjusting mirror group 21, the size of the stretcher 22, and the size of the preset height, and may specifically be 1, 2, 3, 4, 5, or even more times.

I.e., through multiple cycles of the spatial light path, the laser pulses are stretched multiple times by a single stretcher 22 and then output.

Referring to fig. 2, the stretcher assembly 20 may further include a multi-dimensional adjustment frame 26, and the stretcher 22 is disposed on the multi-dimensional adjustment frame 26 to adjust the angle and relative position of the laser pulses input by the seed source 10 and the stretcher 22. The multi-dimensional adjustment frame 26 is capable of multi-directional, multi-angle adjustment of the stretcher 22 to change the angle of incidence and the relative positional relationship of the laser pulses with the stretcher 22. In the whole stretching process, the pulse beam passes through the stretcher 22 for multiple times, the positive second-order dispersion quantity and the negative third-order dispersion quantity are introduced into the system, and the numerical value of the dispersion quantity is related to the cavity type of the whole stretcher assembly 20, the stretcher 22 constant and the distance between the lenses and the stretcher 22. The whole system needs to calculate the size of each-order dispersion quantity of the system precisely, design reasonable parameters, control the included angle and the relative position of the incident pulse and the grating precisely by adjusting the multidimensional adjusting frame 26, realize more precise control of dispersion such as group delay, introduce a large amount of chirp dispersion quantity into the pulse to widen the signal light pulse, reduce peak power in the pulse amplifying process, and flexibly compensate each-order dispersion quantity generated by nonlinear effect in the amplifying system and other dispersion quantity introduced in the system by changing corresponding configuration, and realize diffraction limit ultrashort femtosecond pulse output by matching with a post dispersion compensation device of the system. The multi-dimensional adjusting frame 26 may be a multi-dimensional adjusting frame 26 which is conventional in the market, for example, a four-dimensional adjusting frame or a five-dimensional adjusting frame.

Referring to fig. 1, the power amplification module 40 may include an optical fiber preamplifier 41 and an optical fiber main amplifier 42, one end of the optical fiber preamplifier 41 is connected to the spectrum modulation mechanism 30, the other end of the optical fiber preamplifier 41 is connected to one end of the optical fiber main amplifier 42, and the other end of the optical fiber main amplifier 42 is connected to the pulse compression device.

Referring to fig. 1, the high energy pulses may include a first high energy pulse 411 and a second high energy pulse 421, the optical fiber pre-amplifier 41 for power amplifying and energy extracting the stretched pulses and outputting the first high energy pulse 411, and the optical fiber main amplifier 42 for power amplifying and energy extracting the first high energy pulse 411 and outputting the second high energy pulse 421.

After the spectrum modulation by the spectrum modulation mechanism 30, the pulse light of the saddle-shaped spectrum is coupled to the next-stage optical fiber pre-amplifier 41 through the isolator 35 to perform preliminary extraction of energy, the pulse signal is amplified to the order of hundred milliwatts, the repetition frequency of the pulse is reduced by using the acousto-optic modulator to be modulated to be hundred kHz finally, and then the pulse light is pre-amplified for the second time to be tens of milliwatts, so that the first high-energy pulse 411 is obtained. The first high energy pulse 411 is input to the next stage fiber main amplifier 42 for the next energy extraction. The optical fiber pre-amplifier 41 may be a cascaded single-clad polarization-maintaining active optical fiber amplifier, and performs small-signal amplification on the pulse beam after the spread modulation so as to select the pulse to a low repetition frequency.

After further energy extraction of the signal light using the optical fiber main amplifier 42, a high-power nanosecond pulse laser, i.e., a second high-energy pulse 421, can be output. Because the pulse modulated by the spectrum modulation mechanism 30 is a saddle-shaped spectrum, the problem of narrowing of the pulse spectrum caused by gain narrowing in the optical fiber amplifying process is effectively suppressed, that is, the spectrum of the second high-energy pulse 421 subjected to main amplification remains relatively wide, and a very narrow near-fourier transform limit pulse can be theoretically obtained according to the definition of the time-bandwidth product. The main fiber amplifier 42 may be a cascaded double-clad large-mode-area fiber amplifier, and further extracts energy from the pre-selected pulse. The main amplifying gain fiber may be replaced by a photonic crystal fiber PCF or a tapered fiber, etc.

The pulse compression module 50 is a pulse compression device formed by a right-angle prism pair and a single-face grating, and can introduce a proper negative dispersion quantity into a pulse beam, compensate a positive dispersion quantity introduced by a stretching device and finally output a femtosecond pulse with an ultra-short pulse width.

The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.

Claims (10)

1. The chirped pulse amplifying device based on spectrum modulation is characterized by comprising a seed source, a widening component, a spectrum modulation mechanism, a power amplifying module and a pulse compression module;

the seed source is used for generating laser pulses;

the stretching assembly is arranged on an emergent light path of the seed source and is used for forming a space light path, stretching the passing laser pulse and outputting a stretching pulse;

the spectrum modulation mechanism comprises a first gain optical fiber optical path and a second gain optical fiber optical path, the widening component beam-splitting is connected with the input end of the first gain optical fiber optical path and the input end of the second gain optical fiber optical path, the output end of the first gain optical fiber optical path and the output end of the second gain optical fiber optical path are coupled and connected to the power amplification module, the widening pulse beam-splitting enters the first gain optical fiber optical path and the second gain optical fiber optical path, after phase delay and gain, the widening pulse beam-splitting is coupled and phase interference forms modulation pulse and outputs the modulation pulse to the power amplification module, and the spectrum of the modulation pulse is in a middle depression shape and two side bulge shape;

the power amplification module is used for carrying out power amplification and energy extraction on the modulation pulse and outputting a high-energy pulse;

the pulse compression module is connected with the power amplification module and is used for compressing and outputting the high-energy pulse.

2. The spectrally modulated chirped pulse amplification apparatus of claim 1 wherein the spectrally modulated mechanism further comprises a first coupler and a second coupler, the first coupler being coupled to the stretching assembly and the second coupler being coupled to the power amplification module;

the first gain optical fiber path comprises a first passive optical fiber and a first gain amplification component, one end of the first passive optical fiber is connected with the first coupler, the other end of the first passive optical fiber is connected with the first gain amplification component, and the first gain amplification component is connected with the second coupler;

the second gain optical fiber path comprises a second passive optical fiber and a second gain amplification component, one end of the second passive optical fiber is connected with the first coupler, the other end of the second passive optical fiber is connected with the second gain amplification component, the second gain amplification component is connected with the second coupler, and the lengths of the second passive optical fiber and the first passive optical fiber are unequal.

3. The spectrally modulated chirped pulse amplification apparatus of claim 1 wherein the spectrally modulating mechanism comprises an isolator, a third coupler, a third passive optical fiber, a fourth passive optical fiber, and a third gain amplification assembly, the third passive optical fiber and the fourth passive optical fiber being unequal in length;

the isolator is provided with a first interface, a second interface and a third interface, the first interface is connected with the widening component, the second interface is connected with the third coupler, and the third interface is connected with the power amplification module; the isolator is provided with a first state and a second state, the first interface is communicated with the second interface in the first state, and the third interface is disconnected with the first interface and the second interface; in the second state, the second interface is communicated with the third interface, and the first interface is disconnected with the second interface and the third interface;

the third coupler is connected with one end of the third gain amplifying assembly through the third passive optical fiber, and the third coupler is connected with the other end of the third gain amplifying assembly through the fourth passive optical fiber to form a loop, so that the first gain optical fiber optical path and the second gain optical fiber optical path with opposite directions are formed.

4. The spectrally modulated chirped pulse amplification apparatus of claim 3 wherein the third gain amplification assembly comprises a third active optical fiber, a third pump source, and a third wavelength division multiplexer, the third passive optical fiber, the active optical fiber, the wavelength division multiplexer, and the fourth passive optical fiber being sequentially connected, the third pump source being connected to the third wavelength division multiplexer.

5. A chirped pulse amplification apparatus based on spectral modulation according to claim 3 wherein the isolator is a circulator.

6. The spectrally modulated chirped pulse amplification apparatus of any of claims 1 to 5 wherein the stretching assembly comprises a set of up mirrors, a stretcher, a tele lens, a first mirror, and a second mirror;

the height-adjusting mirror group, the stretcher, the tele lens and the first reflecting mirror are sequentially arranged, the second reflecting mirror is arranged between the height-adjusting mirror group and the stretcher, a preset height difference is arranged between the second reflecting mirror and the height-adjusting mirror group, the height-adjusting mirror group is provided with a gap, the height-adjusting mirror group can be used for reflecting incident laser pulses after adjusting the heights, and the stretcher is used for stretching the incident laser pulses;

after the laser pulse passes through the gap of the height-adjusting mirror group along the space light path, repeating the reflection between the height-adjusting mirror group and the first reflecting mirror for a plurality of times, enabling the laser pulse to pass through the stretcher and the tele lens in sequence for a plurality of times in the forward direction and pass through the tele lens and the stretcher in sequence for a plurality of times in the reverse direction, and finally enabling the laser pulse to be transmitted to the second reflecting mirror from the stretcher, and outputting the stretched pulse to the power amplifying module after being reflected by the second reflecting mirror;

wherein the laser pulse passes through the center of the tele lens without passing through the center of the tele lens.

7. The spectrally modulated chirped pulse amplification apparatus of claim 6 wherein the stretcher assembly further comprises a multi-dimensional adjustment frame, the stretcher being positioned on the multi-dimensional adjustment frame to adjust an included angle and a relative position of the laser pulses input by the seed source and the stretcher.

8. The spectrally modulated chirped pulse amplification apparatus according to any one of claims 1 to 5, wherein the power amplification module comprises an optical fiber preamplifier and an optical fiber main amplifier, one end of the optical fiber preamplifier being connected to the spectral modulation mechanism, the other end of the optical fiber preamplifier being connected to one end of the optical fiber main amplifier, the other end of the optical fiber main amplifier being connected to the pulse compression device;

the high-energy pulse comprises a first high-energy pulse and a second high-energy pulse, the optical fiber pre-amplifier is used for carrying out power amplification and energy extraction on the broadening pulse and outputting the first high-energy pulse, and the optical fiber main amplifier is used for carrying out power amplification and energy extraction on the first high-energy pulse and outputting the second high-energy pulse.

9. The spectrally modulated chirped pulse amplification apparatus of claim 8 wherein the optical fiber pre-amplifier is a cascaded single-clad polarization maintaining active optical fiber amplifier.

10. The spectrally modulated chirped pulse amplification apparatus of claim 8 wherein the fiber main amplifier is a cascaded double-clad large-mode-area fiber amplifier.