A pulsed optical fiber amplifier

Abstract

A pulse fiber amplifier comprises a seed laser, a pump source, a beam combiner, an ytterbium-doped double-clad fiber, a cladding light filter and a QBH fiber, wherein the output fiber of the seed laser is fused with the signal fiber of the beam combiner, the output fiber of the pump source is fused with the pump fiber of the beam combiner, the output fiber of the beam combiner is fused with the ytterbium-doped double-clad fiber, the output end of the ytterbium-doped double-clad fiber is fused with the input fiber of the cladding light filter, and the output fiber of the cladding light filter is fused with the QBH fiber, wherein the gain process of the amplifier is that the pump wavelength is Yb 3+ The ions are pumped from the ground state of the 2F7 / 2 energy level to between the ground state and the first excited state of the 2F5 / 2 energy level, thereby achieving simultaneous suppression of the generation of forward amplified spontaneous emission and backward amplified spontaneous emission; thereby achieving simultaneous suppression of forward and backward transmitted ASE and SRS, which can be used to achieve higher energy pulsed laser output.

Description

Technical Field

[0001] The invention relates to the field of laser technology, in particular to a pulse optical fiber amplifier. Background Art

[0002] Fiber lasers have the advantages of high efficiency, high beam quality, and high compactness, and are widely used in modern high-tech industrial processing technology. Pulsed fiber lasers have the advantages of high peak power, high beam quality, and high stability, and are widely used in applications such as laser stripping, laser cleaning, and laser etching. Further improving the single pulse energy of pulsed lasers can improve the efficiency of laser processing. However, the main bottleneck factors faced in improving the single pulse energy are amplified spontaneous emission (ASE) and stimulated Raman scattering (SRS). Conventional methods for suppressing ASE and SRS of pulsed fiber lasers include using filters, backward pumping, and synchronous pumping. The filter structure is the most commonly used. Limited by the power it can withstand, the filter can only filter out the ASE and SRS generated by the preamplifier, but cannot filter out the ASE and SRS in the final amplifier stage, resulting in poor suppression effect; backward pumping is mainly limited by the backward pumping combiner, and it is difficult to achieve high-energy pulsed laser output of the all-fiber structure. Synchronous pumping requires tuning the delay of the pump laser pulse and the signal laser pulse, and its electronic control system is complex. Therefore, a method for suppressing ASE and SRS of pulsed fiber lasers with a simple and stable structure is needed. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a pulse optical fiber amplifier which can effectively suppress spontaneous radiation and stimulated Raman scattering effects.

[0004] The technical solution adopted by the present invention to solve the technical problem is:

[0005] A pulse fiber amplifier comprises a seed laser, a pump source, a beam combiner, an ytterbium-doped double-clad fiber, a cladding light filter and a QBH fiber, wherein the output fiber of the seed laser is fused with the signal fiber of the beam combiner, the output fiber of the pump source is fused with the pump fiber of the beam combiner, the output fiber of the beam combiner is fused with the ytterbium-doped double-clad fiber, the output end of the ytterbium-doped double-clad fiber is fused with the input fiber of the cladding light filter, and the output fiber of the cladding light filter is fused with the QBH fiber, wherein the gain process of the amplifier is that the pump wavelength is Yb 3 The + ions are pumped from the ground state of the 2F7 / 2 energy level to between the ground state and the first excited state of the 2F5 / 2 energy level, thereby achieving simultaneous suppression of the generation of forward amplified spontaneous radiation and backward amplified spontaneous radiation.

[0006] In one embodiment, the output pump light photon energy of the pump source is in the Yb 3+ between the ground state of the 2F7 / 2 energy level of the ion and the ground state and the first excited state of the 2F5 / 2 energy level.

[0007] In one embodiment, the pump source outputs a pump light wave number between 10526 and 10752 cm- 1 between.

[0008] In one embodiment, the seed laser is a nanosecond pulse laser, and the central wavelength of the seed laser output laser is 1064nm±5nm, the pulse width is 100ns-150ns, the repetition frequency is 10-30kHz, and the output power is 10-50W.

[0009] In one embodiment, the output optical fiber of the seed laser is a double-clad optical fiber, the core diameter of the output optical fiber of the seed laser is 20-50 μm, and the core numerical aperture NA=0.06-0.075.

[0010] In one embodiment, the output optical fiber of the pump source is a single-clad optical fiber, the core diameter of the output optical fiber of the pump source is 105-220 μm, and the core numerical aperture NA=0.12-0.22.

[0011] In one embodiment, the signal fiber of the combiner is a double-clad fiber, and the core diameter and core numerical aperture of the signal fiber of the combiner are equal to the core diameter and core numerical aperture of the seed laser output fiber.

[0012] In one embodiment, the pump fiber of the combiner is a single-clad fiber, and the core diameter and core numerical aperture of the pump fiber of the combiner are equal to the core diameter and core numerical aperture of the pump source output fiber.

[0013] In one embodiment, the output optical fiber of the combiner is a double-clad optical fiber, and the core diameter and core numerical aperture of the output optical fiber of the combiner are equal to the core diameter and core numerical aperture of the ytterbium-doped double-clad optical fiber.

[0014] In one embodiment, the core diameter of the ytterbium-doped double-clad optical fiber output fiber is greater than or equal to the core diameter of the seed laser output fiber, and the core diameter of the ytterbium-doped double-clad optical fiber output fiber is 30-300 μm.

[0015] In one embodiment, the core numerical aperture of the ytterbium-doped double-clad optical fiber output fiber is greater than or equal to the core numerical aperture of the seed laser, and the core numerical aperture of the ytterbium-doped double-clad optical fiber output fiber is 0.75-0.12.

[0016] In one embodiment, the input optical fiber and the output optical fiber of the cladding light filter and the QBH optical fiber are double-clad optical fibers; the core diameter and the core numerical aperture of the input optical fiber and the output optical fiber of the cladding light filter and the QBH optical fiber are equal to the core diameter and the core numerical aperture of the ytterbium-doped double-clad optical fiber.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention fuses the output fiber of the seed laser with the signal fiber of the beam combiner, fuses the output fiber of the pump source with the pump fiber of the beam combiner, fuses the output fiber of the beam combiner with the ytterbium-doped double-clad fiber, fuses the output end of the ytterbium-doped double-clad fiber with the input fiber of the cladding light filter, and fuses the output fiber of the cladding light filter with the QBH fiber, wherein the output pump light photon energy of the pump source is located at the Yb 3 + between the ground state of the 2F7 / 2 energy level of the ion and the ground state and the first excited state of the 2F5 / 2 energy level. Specifically, the pump source outputs a pump light wave number between 10526 and 10752 cm- 1 By utilizing the non-radiative transition between the ground state and the first excited state of the 2F5 / 2 energy level, the backward ASE generated by the ground state pumped to the 2F5 / 2 energy level and the forward ASE generated by the first excited state pumped to the 2F5 / 2 energy level are suppressed, and finally a higher energy pulsed laser output is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0020] Figure 2 This is a comparison diagram of the forward output spectra of the nanosecond pulse amplifier corresponding to Example 1 of the present invention when the first excited state is pumped to the 2F5 / 2 energy level and when the ground state is pumped to the 2F5 / 2 energy level;

[0021] Figure 3 This is a comparison diagram of the backward ASE power corresponding to the nanosecond pulse amplifier when the embodiment 1 of the present invention is pumped to the first excited state of the 2F5 / 2 energy level and when pumped to the ground state of the 2F5 / 2 energy level.

[0022] In the figure: 1. Seed laser; 2. Pump source; 3. Beam combiner; 4. Ytterbium-doped double-clad fiber; 5. Cladding light filter; 6. QBH output fiber. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] Example 1

[0025] like Figure 1As shown, this embodiment includes a seed laser 1, a pump source 2, a beam combiner 3, an ytterbium-doped double-clad fiber 4, a cladding light filter 5 and a QBH fiber 6, wherein the output fiber of the seed laser 1 is fused with the signal fiber of the beam combiner 3. In this embodiment, the seed laser 1 is a nanosecond pulse laser, and the central wavelength of the output laser of the seed laser 1 is 1064nm±5nm, the pulse width is 100ns, the repetition frequency is 10kHz, and the output power is 10W; and the output fiber of the seed laser 1 is a double-clad fiber, and the core diameter of the output fiber of the seed laser 1 is 30μm, and the core numerical aperture NA=0.06;

[0026] The output fiber of the pump source 2 is fused with the pump fiber of the combiner 3. In this embodiment, the output fiber of the pump source 2 is a single-clad fiber, the core diameter of the output fiber of the pump source 2 is 105 μm, the core numerical aperture NA=0.22, and the pump power is 70 W; the output pump light photon energy of the pump source 2 is located at Yb 3 + ion 2F7 / 2 energy level to 2F5 / 2 energy level between the ground state and the first excited state, specifically, the pump source 2 outputs the pump light wave number between 10526 and 10752 cm- 1 between;

[0027] The output fiber of the combiner 3 is fused with the ytterbium-doped double-clad fiber 4. In this embodiment, the combiner 3 is a (6+1)×1 forward pump signal combiner; the pulse seed light generated by the seed laser 1 and the pump light generated by the six pump sources 2 are coupled into the double-clad ytterbium-doped fiber 4;

[0028] The signal fiber of the combiner 3 is a double-clad fiber, and the core diameter and core numerical aperture of the signal fiber of the combiner 3 are equal to the core diameter and core value of the output fiber of the seed laser 1; the pump fiber of the combiner 3 is a single-clad fiber, and the core diameter and core numerical aperture of the pump fiber of the combiner 3 are equal to the core diameter and core value of the output fiber of the pump source 2; the output fiber of the combiner 3 is a double-clad fiber, and the core diameter and core numerical aperture of the output fiber of the combiner 3 are equal to the core diameter and core value of the ytterbium-doped double-clad fiber 4;

[0029] The output end of the ytterbium-doped double-clad optical fiber 4 is fused with the input optical fiber of the cladding light filter 5. In this embodiment, the core diameter of the output optical fiber of the ytterbium-doped double-clad optical fiber 4 is greater than or equal to the core diameter of the output optical fiber of the seed laser 1, and the core diameter of the output optical fiber of the ytterbium-doped double-clad optical fiber 4 is 100 μm; the core numerical aperture of the output optical fiber of the ytterbium-doped double-clad optical fiber 4 is greater than or equal to the core numerical aperture of the seed laser 1, and the core numerical aperture of the output optical fiber of the ytterbium-doped double-clad optical fiber 4 is 0.12;

[0030] The output optical fiber of the cladding light filter 5 is fused with the QBH optical fiber 6. In the present embodiment, the input optical fiber and the output optical fiber of the cladding light filter 5 and the QBH optical fiber 6 are all double-clad optical fibers; the core diameter and the core numerical aperture of the input optical fiber and the output optical fiber of the cladding light filter 5 and the QBH optical fiber 6 are equal to the core diameter and the core numerical aperture of the ytterbium-doped double-clad optical fiber 4.

[0031] The inventors further analyzed the causes of spontaneous radiation in traditional structure pulse fiber amplifiers, and conducted comparative experiments on pulse fiber amplifiers when pumped to the ground state of the 2F5 / 2 energy level and the first excited state of the 2F5 / 2 energy level.

[0032] like Figure 2 As shown, the forward output spectrum of the nanosecond pulse amplifier corresponding to this embodiment and the first excited state when pumped to the 2F5 / 2 energy level and the ground state when pumped to the 2F5 / 2 energy level is compared. It can be seen that when the first excited state is pumped to the 2F5 / 2 energy level, the pulse fiber amplifier produces strong ASE near 1030nm, while when pumped to the first excited state and the ground state of the 2F5 / 2 energy level, the pulse fiber amplifier has SRS noise near 1115nm. Only the output light of this embodiment has no ASE and SRS noise near 1030nm and 1115nm, and the output spectrum is pure.

[0033] like Figure 3 As shown, the backward ASE power corresponding to the nanosecond pulse amplifier of this embodiment when pumped to the first excited state of the 2F5 / 2 energy level and when pumped to the ground state of the 2F5 / 2 energy level, it can be seen that when pumped to the ground state of the 2F5 / 2 energy level, the backward ASE power of the pulse fiber amplifier increases rapidly when the output power reaches 250W, while the backward optical power of the structure of this embodiment is lower than the backward ASE power of the pulse fiber amplifier when pumped to the first excited state and the ground state of the 2F5 / 2 energy level.

[0034] Therefore, by adopting the structure of this embodiment, the non-radiative transition between the ground state and the first excited state of the 2F5 / 2 energy level is utilized to avoid the backward ASE generated by pumping to the ground state of the 2F5 / 2 energy level and the forward ASE generated by pumping to the first excited state of the 2F5 / 2 energy level, thereby achieving pure spectral output, which can be used to obtain higher energy pulsed laser output.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the technical solutions of the present invention have been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pulsed optical fiber amplifier, characterized in that: The invention comprises a seed laser (1), a pump source (2), a beam combiner (3), an ytterbium-doped double-clad optical fiber (4), a cladding light filter (5) and a QBH optical fiber (6), wherein the output optical fiber of the seed laser (1) is fused with the signal optical fiber of the beam combiner (3), the output optical fiber of the pump source (2) is fused with the pump optical fiber of the beam combiner (3), the output optical fiber of the beam combiner (3) is fused with the ytterbium-doped double-clad optical fiber (4), the output end of the ytterbium-doped double-clad optical fiber (4) is fused with the input optical fiber of the cladding light filter (5), and the output optical fiber of the cladding light filter (5) is fused with the QBH optical fiber (6); wherein the gain process of the amplifier is that the pump wavelength pumps the Yb3+ ions from the ground state of the 2F7 / 2 energy level to between the ground state of the 2F5 / 2 energy level and the first excited state, thereby realizing the simultaneous suppression of the generation of forward amplified spontaneous radiation and backward amplified spontaneous radiation; The photon energy of the pump light output by the pump source (2) is between the ground state of the 2F7 / 2 energy level of the Yb3+ ion and the ground state and the first excited state of the 2F5 / 2 energy level; the wave number of the pump light output by the pump source (2) is between 10526 and 10752 cm-1; the seed laser (1) is a nanosecond pulse laser, and the central wavelength of the laser output by the seed laser (1) is 1064 nm±5 nm, the pulse width is 100 ns to 150 ns, the repetition frequency is 10 to 30 kHz, and the output power is 10 to 50 W.

2. The pulse fiber amplifier according to claim 1, characterized in that: The output optical fiber of the seed laser (1) is a double-clad optical fiber, the core diameter of the output optical fiber of the seed laser (1) is 20 to 50 μm, and the core numerical aperture NA is 0.06 to 0.

075.

3. The pulse fiber amplifier according to claim 2, characterized in that: The output optical fiber of the pump source (2) is a single-clad optical fiber, the core diameter of the output optical fiber of the pump source (2) is 105-220 μm, and the core numerical aperture NA is 0.12-0.

22.

4. The pulse fiber amplifier according to claim 3, characterized in that: The signal optical fiber of the beam combiner (3) is a double-clad optical fiber, and the core diameter and core numerical aperture of the signal optical fiber of the beam combiner (3) are equal to the core diameter and core numerical aperture of the output optical fiber of the seed laser (1).

5. The pulse fiber amplifier according to claim 4, characterized in that: The pump fiber of the beam combiner (3) is a single-clad fiber, and the core diameter and core numerical aperture of the pump fiber of the beam combiner (3) are equal to the core diameter and core numerical aperture of the output fiber of the pump source (2); the output fiber of the beam combiner (3) is a double-clad fiber, and the core diameter and core numerical aperture of the output fiber of the beam combiner (3) are equal to the core diameter and core numerical aperture of the ytterbium-doped double-clad fiber (4).

6. The pulse fiber amplifier according to claim 5, characterized in that: The core diameter of the output fiber of the ytterbium-doped double-clad fiber (4) is greater than or equal to the core diameter of the output fiber of the seed laser (1), and the core diameter of the output fiber of the ytterbium-doped double-clad fiber (4) is 30 to 300 μm; the core numerical aperture of the output fiber of the ytterbium-doped double-clad fiber (4) is greater than or equal to the core numerical aperture of the seed laser (1), and the core numerical aperture of the output fiber of the ytterbium-doped double-clad fiber (4) is 0.75 to 0.

12.

7. The pulse fiber amplifier according to claim 6, characterized in that: The input optical fiber and the output optical fiber of the cladding light filter (5) and the QBH optical fiber (6) are all double-clad optical fibers; the core diameter and the core numerical aperture of the input optical fiber and the output optical fiber of the cladding light filter (5) and the QBH optical fiber (6) are equal to the core diameter and the core numerical aperture of the ytterbium-doped double-clad optical fiber (4).

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