CN115799971A - Intermediate infrared high-energy femtosecond pulse fiber laser source with tunable wavelength and broadband - Google Patents

Abstract

The invention discloses a wavelength broadband tunable intermediate infrared high-energy femtosecond pulse fiber laser source, which comprises a laser pumping source, a laser pumping source tail fiber, a first lens, a dichroic mirror, a second lens, an active fiber and a third lens which are sequentially connected, wherein the dichroic mirror is connected with a seed laser source, and the active fiber is a double-cladding Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ An optical fiber; and adjusting the power of the laser pumping source, amplifying and frequency shifting the femtosecond pulse laser generated by the seed laser source in the active optical fiber, and obtaining the continuously tunable high-energy femtosecond pulse laser with the wave band of 3-5 mu m. The invention utilizes double-cladding Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ Optical fiber as gain medium with Er ³⁺ In (1) ⁴ F _9/2 → ⁴ I _9/2 Transition, dy ³⁺ In ⁶ H _13/2 → ⁶ H _15/2 Transition and ⁶ H _11/2 → ⁶ H _13/2 the transition realizes the radiation of three transition bands, realizes the full-band gain compensation, and finally obtains the continuously tunable high-energy femtosecond pulse laser with the wave band of 3-5 mu m.

Description

Intermediate infrared high-energy femtosecond pulse fiber laser source with tunable wavelength and broadband

Technical Field

The invention relates to the field of lasers, in particular to a mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband.

Background

The mid-infrared band of 3-5 μm is an important wavelength interval, which not only is a low-loss transmission window of the atmosphere, but also covers absorption peaks of a plurality of molecules and chemical bonds, so that the mid-infrared laser source positioned in the wavelength interval has important application value in the fields of gas detection, polymer processing, infrared countermeasure, atmospheric communication and the like. In recent years, with the continuous improvement of the infrared fiber drawing process and the pumping technology, the mid-infrared fiber laser technology has been developed dramatically, and especially the femtosecond pulse with narrow time domain width and high peak power has received much attention. Mode locking is the most common technical means for generating femtosecond pulses, but is limited by the bandwidth of a rare earth gain medium, the working wavelength of the pulse is fixed or can be tuned only in a narrow range, the widest tuning range of the existing intermediate infrared femtosecond mode locking fiber laser is only 55nm, which greatly limits the application of the laser, therefore, the intermediate infrared femtosecond fiber laser source with tunable wavelength and broadband becomes a research hotspot, wherein the femtosecond fiber laser source based on the fiber Raman soliton self-frequency shift effect has been widely concerned about due to the simple structure and the flexible wavelength regulation and control capability.

In 2016, a research team at Connell university, USA, using 2 μm femtosecond pulses as excitation, inF ₃ The passive optical fiber is used as a nonlinear medium, the generation of femtosecond pulse with continuously tunable wavelength of 2-4.3 μm is realized, however, the pulse energy is only at the level of several nJ due to the lack of gain compensation in the pulse frequency shift process; in the same year, the research team at Laval university of Canada utilized 2.8 μm femtosecond pulses as seeds in combination with Er-doped ³⁺ ZrF ₄ Optical fiber amplification and frequency shift, and realizationThe femtosecond pulse with tunable wavelength of 2.8-3.6 μm is output, and the pulse energy reaches 37nJ; recently, they have optimized Er doping on the basis of the prior art ³⁺ ZrF ₄ The length of optical fiber is welded with a section of passive InF at the rear ₃ The femtosecond pulse wavelength is expanded to 4.8 μm by the optical fiber, however, due to the lack of long wave gain, the long wave pulse energy is lower (several nJ), and the wavelength is further limited to be expanded, so that the full coverage of 3 μm-5 μm cannot be realized.

Disclosure of Invention

The invention aims to overcome the problem that the femtosecond pulse laser in the prior art cannot realize full coverage of 3-5 mu m, and provides a wavelength-broadband tunable intermediate infrared high-energy femtosecond pulse fiber laser source.

The purpose of the invention is realized by the following technical scheme:

mainly provide a wavelength broadband tunable intermediate infrared high energy femtosecond pulse fiber laser source, including laser pumping source, laser pumping source tail optical fiber, first lens, dichroscope, second lens, active optical fiber and the third lens that connect gradually, wherein, be connected with seed laser source on the dichroscope, active optical fiber is double-clad Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ An optical fiber;

and adjusting the power of the laser pumping source, amplifying and frequency shifting the femtosecond pulse laser generated by the seed laser source in the active optical fiber, and obtaining the continuously tunable high-energy femtosecond pulse laser with the wave band of 3-5 mu m.

In one example, a wavelength broadband tunable mid-infrared high-energy femtosecond pulsed fiber laser source is used for generating red laser with the wavelength of 645nm to 655 nm.

In one example, a wavelength broadband tunable mid-infrared high-energy femtosecond pulsed fiber laser source for generating femtosecond pulsed laser light with a wavelength of 3 μm.

In one example, the first lens and the third lens are collimating lenses.

In one example, the second lens is used for coupling pump light output by a laser pump source tail fiber into an inner cladding layer of an active optical fiber and coupling laser generated by a seed laser source into a fiber core of the active optical fiber.

In one example, a wavelength broadband tunable mid-infrared high-energy femtosecond pulse fiber laser source, the femtosecond pulse laser generated by the seed laser source is amplified and frequency shifted in the active fiber, and the method comprises the following steps:

through Er in active fiber ³⁺ Generating a first radiation band passing Dy in the active fiber ³⁺ A second radiation band and a third radiation band are generated.

In one example, a wavelength broadband tunable mid-infrared high-energy femtosecond pulse fiber laser source passes Er in an active fiber ³⁺ Generating a first radiation band, comprising:

⁴ F _9/2 → ⁴ I _9/2 the transition realizes laser amplification in the wavelength range of 3.2-3.9 microns.

In one example, a mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband passes Dy in an active fiber ³⁺ Generating a second radiation band, comprising:

Dy ³⁺ in ⁶ H _13/2 → ⁶ H _15/2 The transition realizes laser amplification in the wavelength range of 3-3.4 μm.

In one example, a mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband passes Dy in an active fiber ³⁺ Generating a third radiation band comprising:

⁶ H _11/2 → ⁶ H _13/2 the transition realizes laser amplification in the wavelength range of 4-5 microns.

In one example, a wavelength broadband tunable mid-infrared high-energy femtosecond pulse fiber laser source, the laser pump source pigtail is a multimode fiber.

It should be further noted that the technical features corresponding to the above options can be combined with each other or replaced to form a new technical solution without conflict.

Compared with the prior art, the invention has the beneficial effects that:

(1) The active optical fiber of the invention is double-clad Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ Optical fiber using double-clad Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ Optical fiber as gain medium with Er ³⁺ In ⁴ F _9/2 → ⁴ I _9/2 Transition, dy ³⁺ In ⁶ H _13/2 → ⁶ H _15/2 Transition and ⁶ H _11/2 → ⁶ H _13/2 the transition realizes the radiation of three transition bands, realizes the gain compensation of the whole band, finally obtains the continuously tunable high-energy femtosecond pulse laser with the wave band of 3-5 mu m, and gives consideration to the wavelength broadband tuning and the high-energy operation.

(2) Double-clad Er used in the invention ³⁺ 、Dy ³⁺ Co-doped InF ₃ The optical fiber can not only provide broadband gain within the range of 3-5 μm, solve the problem of too low pulse energy caused by the lack of long wave gain of the tunable femtosecond optical fiber laser source, but also provide a proper transmission medium for the wavelength frequency shift of the femtosecond pulse.

Drawings

Fig. 1 is a schematic structural diagram of a mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband according to an embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating energy level transition according to an embodiment of the present invention;

fig. 3 is a schematic view of a radiation band shown in an embodiment of the present invention.

In the figure: 1. a laser pump source; 2. a laser pumping source pigtail; 3. inputting pump light; 4. a first lens; 5. a dichroic mirror; 6. a seed laser source; 7. a second lens; 8. an active optical fiber; 9. a third lens; 10. outputting laser; 11. ⁴ I _15/2 an energy level; 12. ⁴ I _13/2 an energy level; 13. ⁴ I _11/2 an energy level; 14. ⁴ I _9/2 an energy level; 15. ⁴ F _9/2 an energy level; 16. first, theAn up transition; 17. a first lower transition; 18. a second lower transition; 19. a first energy transfer process; 20. a second energy transfer process; 21. ⁶ H _15/2 an energy level; 22. ⁶ H _13/2 an energy level; 23. ⁶ H _11/2 an energy level; 24. ⁶ H _9/2, ⁶ F _11/2 an energy level; 25. ⁶ H _7/2, ⁶ F _9/2 an energy level; 26. a third lower transition; 27. a fourth lower transition; 28. a fifth lower transition; 29 sixth lower transition.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like are directions or positional relationships described based on the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in a specific case to those of ordinary skill in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1, in an exemplary embodiment, the present invention provides a wavelength-broadband-tunable intermediate infrared high-energy femtosecond pulse fiber laser source, including a laser pump source 1, a laser pump source tail fiber 2, a first lens 4, a dichroic mirror 5, a second lens 7, an active fiber 8, a third lens 9, and a laser output 10, which are connected in sequence, wherein the dichroic mirror 5 is connected with a seed laser source 6, and the active fiber 8 is a double-clad Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ An optical fiber;

and adjusting the power of the laser pumping source 1, amplifying and frequency shifting the femtosecond pulse laser generated by the seed laser source 6 in the active optical fiber 8, and obtaining the continuously tunable high-energy femtosecond pulse laser with the wave band of 3-5 microns.

Specifically, the laser pump source 1 is used for generating red laser with the wavelength of 645nm to 655nm as pump light; the laser pumping source tail fiber 2 is a multimode fiber and is used for outputting red laser with the wavelength of 645nm to 655nm, the red laser with the wavelength of 645nm to 655nm is output to the first lens 4 through the pumping light input 3, the first lens 4 is used for collimating and outputting pumping light, and the dichroic mirror 5 is highly transparent to the red laser with the wavelength of 645nm to 655 nm;

further, the seed laser source 6 is configured to generate femtosecond pulse laser with a wavelength of 3 μm, the dichroic mirror 5 is configured to highly reflect the femtosecond pulse laser with the wavelength of 3 μm, and combine the pump laser and the femtosecond pulse laser, and then the second lens 7 focuses and couples the pump laser and the femtosecond pulse laser generated by the seed laser source 6 into the inner cladding and the core of the active optical fiber 8, specifically, couples the pump light output by the laser pump source pigtail 2 into the inner cladding of the active optical fiber 8, and couples the laser generated by the seed laser source 6 into the core of the active optical fiber 8.

Wherein the active optical fiber 8 is double-clad Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ Optical fiber for amplifying femtosecond pulse laser with wavelength of 3 μm and using arcThe sub-self-frequency shift effect shifts to longer wavelengths; the femtosecond pulse laser generated in the core of the active optical fiber 8 is collimated by a third lens 9 and then output through a laser output 10.

Further, with the increase of the power of the laser pumping source 1, the seed laser undergoes amplification and frequency shift in the active fiber 8, and finally the femtosecond pulse laser with the tunable wavelength of 3-5 μm is generated.

In one example, the femtosecond pulse laser generated by the seed laser source is amplified and frequency shifted in the active fiber, and comprises:

through Er in active fiber ³⁺ Generating a first radiation band passing Dy in the active fiber ³⁺ A second radiation band and a third radiation band are generated.

In particular, as shown in figure 2, ⁴ I _15/2 energy level 11 is Er in active optical fiber 8 ³⁺ The ions are in a first energy level of, ⁴ I _13/2 energy level 12 being Er in the active fiber 8 ³⁺ A second energy level of the ion; ⁴ I _11/2 energy level 13 being Er in active optical fiber ³⁺ A third energy level of the ion; ⁴ I _9/2 energy level 14 being Er in active fiber ³⁺ A fourth energy level of the ion; ⁴ F _9/2 energy level 15 is Er in active optical fiber ³⁺ A fifth energy level of the ion; the first upper transition 16 is at ⁴ I _15/2 Energy level 11 and ⁴ F _9/2 the energy level between the energy levels 15 is generated, ⁴ I _15/2 ion-absorbing pump light at energy level 11 transitions to ⁴ F _9/2 At an energy level 15, wherein red laser with the wavelength of 645 nm-655 nm is selected as pump light and corresponds to a strong absorption region of a first upper transition 16;

further, the first lower transition 17 is at ⁴ F _9/2 Energy level 15 and ⁴ I _9/2 between the energy levels 14, a second lower transition 18 is generated ⁴ I _9/2 Energy level 14 and ⁴ I _11/2 the energy level between the energy levels 13 is generated, ⁴ I _9/2 the ions at the energy level 14 transition to by means of multiphoton relaxation ⁴ I _11/2 At an energy level of 13; the first energy transfer process 19 occurs ⁴ I _11/2 Energy level 13 and ⁶ H _7/2, ⁶ F _9/2 between energy levels 25 such that ⁴ I _11/2 Ions at energy level 13 rapidly transition back ⁴ I _15/2 Energy level 11 at the same time ⁶ H _15/2 Ion absorption at energy level 21 ⁴ I _11/2 Energy level 13 ion transition released energy transition to ⁶ H _7/2 , ⁶ F _9/2 An energy level 25; the second energy transfer process 20 occurs at ⁴ I _13/2 Energy levels 12 and ⁶ H _11/2 between energy levels 23 such that ⁴ I _13/2 Ions at energy level 12 rapidly transition back to ⁴ I _15/2 Energy level 11 at the same time ⁶ H _15/2 Ion absorption at energy level 21 ⁴ I _13/2 Energy transition to energy level 12 ion transition release ⁶ H _11/2 An energy level 23; wherein, ⁶ H _15/2 the energy level 21 is Dy in the active optical fiber 8 ³⁺ The ions have a first energy level at which, ⁶ H _13/2 energy level 22 being Dy in active fiber 8 ³⁺ The ions are in the second energy level of the ion, ⁶ H _11/2 energy level 23 being Dy in active fiber 8 ³⁺ A third energy level of the ion; ⁶ H _9/2 , ⁶ F _11/2 energy level 24 being Dy in active fiber 8 ³⁺ A fourth energy level of the ion; ⁶ H _7/2 , ⁶ F _9/2 energy level 25 being Dy in active fiber 8 ³⁺ Ion fifth energy level, third lower transition 26 at ⁶ H _7/2 , ⁶ F _9/2 Energy level 25 and ⁶ H _9/2 , ⁶ F _11/2 resulting between the energy levels 24 of the light beam, ⁶ H _7/2 , ⁶ F _9/2 the ions at energy level 25 transition to by means of multiphoton relaxation ⁶ H _9/2 , ⁶ F _11/2 At an energy level 24; the fourth lower transition 27 is at ⁶ H _9/2 , ⁶ F _11/2 Energy level 24 and ⁶ H _11/2 which is generated between the energy levels 23 of the, ⁶ H _9/2 , ⁶ F _11/2 the ions at the energy level 24 transition to by means of multiphoton relaxation ⁶ H _11/2 At an energy level 23; the fifth lower transition 28 is at ⁶ H _11/2 Energy level 23 and ⁶ H _13/2 between energy levels 22, and a sixth lower transition 29 at ⁶ H _13/2 Energy level 22 and ⁶ H _15/2 between the energy levels 21. Wherein, ⁶ H _9/2 , ⁶ F _11/2 energy level 24 and ⁶ H _7/2 , ⁶ F _9/2 the energy level 25 is a combination of two energy levels, and represents that the two energy levels are closely spaced, and can be regarded as one energy level process.

Furthermore, the red laser with the wavelength of 645nm to 655nm is used for transmitting the light in the active optical fiber 8 ⁴ I _15/2 Ion pumping at energy level 11 to ⁴ F _9/2 At energy level 15, realize ⁴ F _9/2 Energy level 15 and lower energy level ⁴ I _9/2 The population inversion between the energy levels 14, ⁴ F _9/2 ions at energy level 15 are rapidly transferred to via a first lower transition 17 ⁴ I _9/2 At the energy level 14, the first lower transition 17 amplifies laser light with a wavelength of 3.2 μm to 3.9 μm by means of stimulated radiation. Followed by ⁴ I _9/2 Ions at energy level 14 are rapidly transferred to via a second lower transition 18 ⁴ I _11/2 At energy level 13.

Immediately after that, the user can either put the paper on his/her head, ⁶ H _15/2 partial ion absorption at energy level 21 ⁴ I _11/2 Ion transition back at energy level 13 ⁴ I _15/2 The energy released at the energy level 11 then transits to ⁶ H _7/2 , ⁶ F _9/2 At energy level 25, the first energy transfer process 19 is completed; ⁶ H _15/2 partial ion absorption at energy level 21 ⁴ I _13/2 Ion transition back to energy level 12 ⁴ I _15/2 The energy released at the energy level 11 then transitions to ⁶ H _11/2 At energy level 23, the second energy transfer process 20 is completed. After the completion of the two energy transfer processes, ⁶ H _7/2 , ⁶ F _9/2 the ion of energy level 25 is rapidly transferred to via a third lower transition 26 ⁶ H _9/2 , ⁶ F _11/2 The energy level of the light beam 24 is, ⁶ H _9/2 , ⁶ F _11/2 the ion at energy level 24 is rapidly transferred to via a fourth lower transition 27 ⁶ H _11/2 Energy level 23, realization ⁶ H _11/2 Energy level 23 and lower energy level ⁶ H _13/2 The population inversion between the energy levels 22, ⁶ H _11/2 the ion at energy level 23 is rapidly transferred to via a fifth lower transition 28 ⁶ H _13/2 And the energy level 22 is used for amplifying laser with the wavelength of 4-5 mu m by means of stimulated radiation. At the same time as this is done, ⁶ H _13/2 energy level 22 and lower energy level ⁶ H _15/2 A population inversion is formed between the energy levels 21, ⁶ H _13/2 the ion at energy level 22 is rapidly transferred to via a sixth lower transition 29 ⁶ H _15/2 And the energy level 21 is amplified by means of stimulated radiation to generate laser with the wavelength of 3-3.4 microns.

When the seed laser source 6 enters the active fiber 8, the signal light with 3 μm wavelength will shift to the long wavelength direction under the effect of the self-frequency shift of Raman soliton, and when the wavelength shifts to and with ⁶ H _13/2 Energy level 22 and ⁶ H _15/2 energy level 21, ⁴ F _9/2 Energy level 15 and ⁴ I _9/2 energy level 14 and ⁶ H _11/2 energy level 23 and ⁶ H _13/2 when the energy level 22 transits the wavelength, the energy is effectively amplified to realize energy promotion, and finally, the high-energy femtosecond pulse laser with tunable wavelength of 3-5 microns can be output by controlling the power of the laser pumping source 1.

Further, as shown in FIG. 3, the first lower transition 17, the fifth lower transition 28 and the sixth lower transition 29 each generate three radiation bands, wherein the first lower transition 17 passes Er in the active fiber ³⁺ A first band of radiation is generated and, ⁴ F _9/2 → ⁴ I _9/2 the laser with the transition of 3.2-3.9 μm provides amplification gain; sixth down-transition 29 passes Dy in active fiber ³⁺ Generating a second radiation band, dy ³⁺ In ⁶ H _13/2 → ⁶ H _15/2 The laser with the transition of 3-3.4 microns provides amplification gain. The fifth lower transition 28 passes Dy in the active fiber ³⁺ A third radiation band is generated which is, ⁶ H _11/2 → ⁶ H _13/2 the transition is from 4 μm to 5 μm of laser light to provide amplification gain.

The invention utilizes the red light laser diode pumping double-cladding Er with the wavelength of 645 nm-655 nm ³⁺ 、Dy ³⁺ Co-doped InF ₃ Optical fiber, simultaneous excitation of Er ³⁺ And Dy ³⁺ In ⁴ F _9/2 → ⁴ I _9/2 ， ⁶ H _11/2 → ⁶ H _13/2 And ⁶ H _13/2 → ⁶ H _15/2 the three transition zones radiate, and the gain bandwidth is greatly expanded. Meanwhile, double cladding Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ The optical fiber not only can provide broadband gain within the range of 3-5 mu m, but also utilizes the red light laser diode pumping double-cladding Er with the wavelength of 645-655 nm ³⁺ /Dy ³⁺ Co-doped InF ₃ The optical fiber is used as a femtosecond pulse wavelength frequency shift and broadband amplification medium, and provides a proper transmission medium for the wavelength frequency shift of the femtosecond pulse.

Furthermore, the first lens and the third lens are both collimating lenses, and the tail fiber of the laser pumping source is a multimode fiber.

The above detailed description is for the purpose of describing the invention in detail, and it should not be construed that the detailed description is limited to the description, and it will be apparent to those skilled in the art that various modifications and substitutions can be made without departing from the spirit of the invention.

Claims (10)

1. The laser comprises a laser pumping source, a laser pumping source tail fiber, a first lens, a dichroic mirror, a second lens, an active fiber and a third lens which are sequentially connected, wherein the dichroic mirror is connected with a seed laser source, and the active fiber is a double-cladding Er ³⁺ 、Dy ³⁺ Co-doped InF ₃ An optical fiber;

and adjusting the power of the laser pumping source, amplifying and frequency shifting the femtosecond pulse laser generated by the seed laser source in the active optical fiber, and obtaining the continuously tunable high-energy femtosecond pulse laser with the wave band of 3-5 mu m.

2. The source of claim 1, wherein the pump source is configured to generate red laser light with a wavelength of 645nm to 655 nm.

3. The source of claim 1, wherein the seed laser source is configured to generate femtosecond pulsed laser with a wavelength of 3 μm.

4. The source of claim 1, wherein the first and third lenses are collimating lenses.

5. The source of claim 1, wherein the second lens is configured to couple pump light output from a laser pump source pigtail into an inner cladding of the active fiber, and couple laser light generated by a seed laser source into a core of the active fiber.

6. The mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband according to claim 1, wherein the femtosecond pulse laser generated by the seed laser source is amplified and frequency-shifted in the active fiber, and the frequency shift comprises:

through Er in active fiber ³⁺ Generating a first radiation band passing Dy in the active fiber ³⁺ A second radiation band and a third radiation band are generated.

7. The source of claim 6, wherein the Er in the pass-through active fiber is ³⁺ Generating a first radiation band, comprising:

⁴ F _9/2 → ⁴ I _9/2 the transition realizes laser amplification in the wavelength range of 3.2-3.9 microns.

8. The mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband according to claim 6, wherein Dy in the pass-through active fiber ³⁺ Generating a second radiation band, comprising:

Dy ³⁺ in ⁶ H _13/2 → ⁶ H _15/2 The transition realizes laser amplification in the wavelength range of 3-3.4 μm.

9. The mid-infrared high-energy femtosecond pulse fiber laser source with tunable wavelength broadband according to claim 6, wherein Dy in the active fiber passes through ³⁺ Generating a third radiation band comprising:

⁶ H _11/2 → ⁶ H _13/2 the transition realizes laser amplification in the wavelength range of 4-5 microns.

10. The source of claim 1, wherein the pump source pigtail is a multimode fiber.

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