CN216055667U

CN216055667U - L-waveband high-power ytterbium-doped fiber laser adopting bidirectional pump hybrid pumping

Info

Publication number: CN216055667U
Application number: CN202122711941.4U
Authority: CN
Inventors: 史伟; 许阳; 房强
Original assignee: Hfb Photonics Co ltd
Current assignee: Hfb Photonics Co ltd
Priority date: 2021-11-08
Filing date: 2021-11-08
Publication date: 2022-03-15
Anticipated expiration: 2031-11-08

Abstract

The utility model discloses an L-waveband high-power ytterbium-doped fiber laser adopting two-way pumping hybrid pumping, which comprises a seed source, wherein the output end of the seed source is connected with a fiber power amplifier, the fiber power amplifier comprises a forward pumping signal fiber laser beam combiner, a double-cladding ytterbium-doped fiber, a mode field adapter, a first cladding light filter, a triple-cladding ytterbium-doped fiber and a reverse pumping signal fiber laser beam combiner which are sequentially connected, the pumping end of the forward pumping signal fiber laser beam combiner is connected with a laser with the same pump, and the pumping end of the reverse pumping signal fiber laser beam combiner is connected with a semiconductor laser pumping source; the output end of the optical fiber power amplifier is connected with the second cladding light filter and the laser output head. Compared with a semiconductor pump double-cladding L-waveband ytterbium-doped fiber laser, the utility model effectively inhibits C-waveband Amplified Spontaneous Emission (ASE) which has the greatest influence on the laser, and realizes the high-power L-waveband ytterbium-doped fiber laser with the output power up to thousands of watts.

Description

L-waveband high-power ytterbium-doped fiber laser adopting bidirectional pump hybrid pumping

Technical Field

The utility model belongs to the technical field of optical fibers and lasers, and particularly relates to an L-waveband high-power ytterbium-doped optical fiber laser adopting bidirectional pump hybrid pumping.

Background

Generally speaking, the L-band of the emission spectrum of ytterbium ion is 1100-1200 nm. The high-power ytterbium-doped fiber laser with the working wavelength in the L-waveband has wide application in the fields of laser remote sensing, laser spectroscopy, guide star laser pumping, laser biology and the like, compared with C-waveband laser radiation of ytterbium ions, the main challenge facing the L-waveband ytterbium-doped fiber laser comes from C-waveband ASE, the generation and amplification of stray light can reduce the signal-to-noise ratio (SNR) of signal laser, and even parasitic oscillation is generated to cause laser path damage. However, since the emission cross section of photons in the C-band is much higher than that in the L-band in the ytterbium ion emission spectrum, higher gain is easily obtained in the ytterbium-doped fiber. Therefore, the suppression of C-band ASE and parasitic oscillation laser thereof is always the primary subject of the development of L-band ytterbium-doped fiber laser.

In recent years, a Yb-Raman mixed gain amplifier is proposed, the Stimulated Raman Scattering (SRS) effect in an optical fiber is utilized to obtain high gain of an L-waveband, the influence of ASE of a C-waveband is reduced, and at present, the L-waveband ytterbium-doped optical fiber laser adopting the structure realizes high power output of more than 2 kW. However, such an amplifier requires the injection of laser signals in the C-band and L-band into the system at the same time, and requires the access of a relatively long gain and energy transmission fiber to the amplifier in order to utilize the SRS effect more efficiently. This not only makes the system more complicated, but also makes the laser spectrum get bigger broadening in the amplification process, is unfavorable for the acquisition of narrow linewidth fiber laser.

The same band pumping technology is a new pumping technology applied to high power fiber lasers which is emerging in recent years. Compared with the traditional semiconductor laser pumping technology, the co-band pumping technology generally uses a fiber laser as a pumping source, the pumping laser wavelength is positioned in an S-waveband (typical wavelength is 1018nm) of ytterbium ion radiation, and because ytterbium ions still have a considerable absorption cross section in the waveband, laser in the S-waveband can be used as pumping light to pump ytterbium-doped fiber, and laser gain in a C-waveband or an L-waveband is provided. Compared with semiconductor pump laser (typical wavelength of 915nm, 940nm and 976nm), the same-band pump technology applied to the high-power optical fiber laser can enable the high-power optical fiber laser to have higher quantum efficiency and effectively inhibit mode instability (TMI) effect. In addition, the absorption cross section of the ytterbium-doped fiber in the same-band pumping wave band is smaller than that of the semiconductor pumping wave band, and the same-band pumping light can effectively inhibit reverse ASE when being used as forward pumping of the fiber laser, so that the same-band pumping scheme is also an ideal choice for the L-wave band ytterbium-doped fiber laser. However, since the absorption cross section of the ytterbium-doped fiber in the same-band pumping band is relatively small, the fiber laser using the same-band pump needs a longer gain fiber to ensure sufficient pump absorption compared with the semiconductor-pumped fiber laser system, so the SRS effect and the spectrum broadening effect are more obvious in the high-power ytterbium-doped fiber laser using the same-band pump, which is also an important problem to be solved in such systems.

SUMMERY OF THE UTILITY MODEL

In order to solve the problems, the utility model provides the L-waveband high-power ytterbium-doped fiber laser adopting the bidirectional pump hybrid pumping, which can effectively improve the SNR of the output laser, has reasonable design, overcomes the defects of the prior art and has good effect.

The L-waveband high-power ytterbium-doped fiber laser adopting bidirectional pumping hybrid pumping comprises a seed source, wherein the output end of the seed source is connected with a fiber power amplifier, the fiber power amplifier comprises a forward pumping signal fiber laser beam combiner, a double-cladding ytterbium-doped fiber, a mode field adapter, a first cladding light filter, a triple-cladding ytterbium-doped fiber and a reverse pumping signal fiber laser beam combiner which are sequentially connected along the laser output direction, the pumping end of the forward pumping signal fiber laser beam combiner is connected with a co-band pumping laser, and the pumping end of the reverse pumping signal fiber laser beam combiner is connected with a semiconductor laser pumping source; the output end of the optical fiber power amplifier is sequentially connected with the second cladding light filter and the laser output head.

Further, the forward pump signal fiber laser beam combiner couples the pump laser output by the pump laser with the same band into the double-cladding ytterbium-doped fiber; at the starting end of the three-cladding ytterbium-doped fiber, a first cladding light filter filters reverse pump light transmitted in a second outer cladding, and pump light output by a semiconductor laser pump source is coupled into the second inner cladding of the three-cladding ytterbium-doped fiber through a reverse pump signal fiber laser beam combiner; the laser output by the optical fiber power amplifier is output by the laser output head after the cladding light is filtered by the second cladding light filter.

Further, the laser adopts a MOPA structure or a single resonant cavity structure.

Further, when the laser adopts an MOPA structure, the seed source is an optical fiber laser, a solid laser or a semiconductor laser, the optical fiber power amplifier is of a single-stage structure or is formed by cascading multiple stages of amplifiers, and the seed laser output by the seed source is amplified to thousands of watts after passing through the single-stage or multiple-stage amplifiers.

Furthermore, when the laser adopts a single resonant cavity structure, a high-reflection fiber grating is welded between the double-clad ytterbium-doped fiber and the forward beam combiner, a partial-reflection fiber grating is welded between the triple-clad ytterbium-doped fiber and the backward beam combiner, and the high-reflection fiber grating and the partial-reflection fiber grating jointly form a laser resonant cavity. When the injected pumping laser reaches a certain intensity, the population inversion of the rare earth doped ions occurs in the ytterbium-doped fiber to generate stimulated radiation, and the amplification of the radiated light with a specific wavelength is realized after the frequency selection of the fiber grating, namely, the amplified laser is generated.

Furthermore, the central wavelength of the high-reflection fiber grating and the central wavelength of the partial-reflection fiber grating are the laser signal wavelength, the reflectivity of the high-reflection fiber grating is more than 99%, the reflectivity of the partial-reflection fiber grating is between 0 and 99%, and the reflection bandwidths of the high-reflection fiber grating and the partial-reflection fiber grating are both between 0 and 10 nm.

Furthermore, the working wavelength of the laser is more than 1100nm, and the laser is an L-waveband in an excited radiation spectrum of ytterbium ion (Yb3 +).

Furthermore, the gain fiber used by the laser is formed by cascading a section of double-clad ytterbium-doped fiber and a section of triple-clad ytterbium-doped fiber, wherein the diameters and NA of the fiber core and the first inner cladding of the triple-clad ytterbium-doped fiber are completely the same as the diameters and NA of the fiber core and the first inner cladding of the double-clad ytterbium-doped fiber.

Furthermore, the optical fiber power amplifier adopts a bidirectional pumping mode, the forward pumping source is a high-brightness optical fiber laser pumping source, the pumping wavelength is between 1000nm and 1100nm, the reverse pumping is a semiconductor laser pumping source, and the pumping wavelength is between 900nm and 1000 nm.

The utility model has the following beneficial technical effects:

(1) the utility model uses the same-band pump with the wavelength between 1000nm and 1100nm and the semiconductor pump with the wavelength between 900nm and 1000nm in a mixed way, and applies the two pump sources to the positive direction and the reverse direction of the laser respectively, and fully utilizes the advantages of high TMI threshold value and weak reverse ASE of the same-band pump, thereby avoiding the defect of low absorption coefficient; meanwhile, the advantage of high absorption coefficient of the semiconductor pump is exerted, the defects of strong ASE and low TMI threshold value are avoided, and the advantages and disadvantages of the two pumps are improved, so that the high-power L-waveband ytterbium-doped fiber laser with high SNR is realized;

(2) the structure of the utility model is simpler, and the L-waveband high-power ytterbium-doped fiber laser with high SNR can be obtained without simultaneously using two seed sources of C-waveband and L-waveband;

(3) the utility model only utilizes Yb3+ gain of the ytterbium-doped fiber, but does not utilize Raman gain in the ytterbium-doped fiber, so that the length of the fiber can be compressed to be shorter, thereby being beneficial to narrow linewidth laser output;

drawings

FIG. 1 is a schematic diagram of an MOPA configuration of an ytterbium-doped fiber laser of the present invention;

wherein, 1-seed source; 2-co-band pump laser; 3-forward pumping signal fiber laser beam combiner; 4-double-clad ytterbium-doped fiber; 5-mode field adapter; 6-first cladding light filter; 7-triple clad ytterbium-doped fiber; 8-a reverse pump signal fiber laser beam combiner; 9-semiconductor laser pumping source; 10-a second cladding light filter; 11-a laser output head;

FIG. 2 is a graph showing the results of comparative experiments when an MOPA structure is employed in the ytterbium-doped fiber laser of the present invention;

FIG. 2(a) is a graph showing the positive and negative ASE power curves outputted from the semiconductor-pumped double-clad L-band ytterbium-doped fiber laser; FIG. 2(b) is a graph showing the positive and negative ASE power curves of the output of the ytterbium-doped fiber laser;

FIG. 3 is a schematic diagram of a single-cavity configuration of an ytterbium-doped fiber laser in accordance with the present invention;

wherein, 12-high reflection fiber grating; 13-partially reflecting fiber grating;

Detailed Description

The technical solution of the present invention will be described in detail below with reference to the embodiments of the present invention.

The first embodiment is as follows:

as shown in fig. 1, the L-band high-power ytterbium-doped fiber laser adopting bidirectional pump hybrid pumping includes a seed source 1, an output end of the seed source 1 is connected to a fiber power amplifier, the laser adopts an MOPA structure, the fiber power amplifier includes a forward pump signal fiber laser combiner 3, a double-clad ytterbium-doped fiber 4, a mode field adapter 5, a first clad optical filter 6, a triple-clad ytterbium-doped fiber 7 and a reverse pump signal fiber laser combiner 8, which are sequentially connected along a laser output direction, a pump end of the forward pump signal fiber laser combiner 3 is connected to a pump laser 2 with the same band, and a pump end of the reverse pump signal fiber laser combiner 8 is connected to a semiconductor laser pump source 9; the output end of the optical fiber power amplifier is sequentially connected with a second cladding light filter 10 and a laser output head 11.

The wavelength of the seed source is 1120nm, the seed light injection power of the optical fiber power amplifier is 50W, the optical fiber power amplifier adopts 6-200W 1018nm high-brightness quasi-single mode fiber laser as the same-band pumping source in the forward direction, the output fiber specification is 20/130 μm, and the fiber core NA dimension is 0.08. The forward pump signal fiber laser beam combiner adopts a (6+1) multiplied by 1 beam combiner, an input signal fiber of the forward pump signal fiber laser beam combiner is 20/130 mu m, and a fiber core NA dimension is 0.065, and is used for coupling seed laser into a fiber power amplifier; the specification of the pump optical fiber is 20/130 μm, the pump optical fiber is matched with an output optical fiber of a same-band pump source with 1018nm, the output optical fiber is a 20/250 μm double-clad passive optical fiber, and the NA of the fiber core and the first inner cladding are 0.065 and 0.22 respectively. The size of the double-clad ytterbium-doped fiber is 20/250 μm, the length is 10m, the absorption coefficient near the wavelength of 976nm is about 3.3dB/m, the absorption coefficient near the wavelength of 1018 is about 0.2dB/m, the NA of the fiber core and the first inner cladding are respectively 0.065 and 0.22, and the fiber core and the first inner cladding are matched with the output fiber of the forward beam combiner. 20/250 μm double-clad ytterbium-doped fiber, and then directly welding a section of 10m long triple-clad ytterbium-doped fiber, wherein the specification is 20/250/400 μm, the NA of the fiber core and the first and second inner cladding is 0.065, 0.22 and 0.46 respectively, the pump absorption coefficient of the first inner cladding near 1018nm is about 0.2dB/m, and the pump absorption coefficient of the second inner cladding near 976nm is about 1.3 dB/m. And (3) stripping a coating layer of the three-clad ytterbium-doped fiber by about 5cm near a welding point of the three-clad ytterbium-doped fiber and the double-clad ytterbium-doped fiber, and performing frosting treatment to obtain the CLS for filtering 976nm pump light reversely transmitted in a second inner cladding of the three-clad ytterbium-doped fiber. The reverse beam combiner is a (6+1) multiplied by 1 beam combiner, and the input optical fiber of the reverse beam combiner is a passive optical fiber completely matched with the triple-clad ytterbium-doped optical fiber; the pump fiber specification is 200/220 μm, the core NA is 0.22, and the pump light output by 6 400W 976nm semiconductor lasers is coupled into the second inner cladding of the input fiber. The output fiber of the reverse beam combiner is 20/250 μm double-clad passive fiber, the core NA is 0.065, and the first inner cladding NA is 0.46, and is completely matched with the fiber used by the laser output head. The coating on the tail fiber of the output head is stripped by 5cm and subjected to frosting treatment to filter out the coating light.

Fig. 2(a) shows the results of comparative experimental calculations: adopting a 20m double-cladding 20/400 μm ytterbium-doped fiber and injecting 2400W 976nm reverse pump light, wherein when the output laser power reaches about 2000W, the output forward ASE power and the output reverse ASE power are about 77W and about 11W respectively; FIG. 2(b) is a calculation result based on an embodiment of the present invention: the fiber power amplifier simultaneously injects 1100W 1018nm forward pump light and 2000W 976nm reverse pump light, the output power can reach about 2000W, and the output forward ASE power and the output reverse ASE power are respectively about 18W and about 11W. Therefore, by adopting the scheme provided by the utility model, the forward ASE power is obviously inhibited.

Example two:

as shown in fig. 3, the L-band high-power ytterbium-doped fiber laser adopting bidirectional pump hybrid pumping includes a seed source 1, an output end of the seed source 1 is connected to a fiber power amplifier, the laser adopts a single resonant cavity structure, the amplifier includes a forward pump signal fiber laser combiner 3, a high-reflection fiber grating 12, a double-cladding ytterbium-doped fiber 4, a mode field adapter 5, a first cladding optical filter 6, a triple-cladding ytterbium-doped fiber 7, a partial reflection fiber grating 13 and a reverse pump signal fiber laser combiner 8, which are sequentially connected along a laser output direction, a pump end of the forward pump signal fiber laser combiner 3 is connected to a pump laser 2 with the same band, and a pump end of the reverse pump signal fiber laser combiner 8 is connected to a semiconductor laser pump source 9; the output end of the optical fiber power amplifier is sequentially connected with a second cladding light filter 10 and a laser output head 11, and a high-reflection fiber grating 12 and a partial-reflection fiber grating 13 jointly form a laser resonant cavity. When the injected pumping laser reaches a certain intensity, the population inversion of the rare earth doped ions occurs in the ytterbium-doped fiber to generate stimulated radiation, and the amplification of the radiated light with a specific wavelength is realized after the frequency selection of the fiber grating, namely, the amplified laser is generated.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.

Claims

1. The L-waveband high-power ytterbium-doped fiber laser adopting bidirectional pumping and hybrid pumping is characterized by comprising a seed source, wherein the output end of the seed source is connected with a fiber power amplifier, the fiber power amplifier comprises a forward pumping signal fiber laser beam combiner, a double-cladding ytterbium-doped fiber, a mode field adapter, a first cladding light filter, a three-cladding ytterbium-doped fiber and a reverse pumping signal fiber laser beam combiner, which are sequentially connected along the laser output direction, the pumping end of the forward pumping signal fiber laser beam combiner is connected with a pump laser with the same band, and the pumping end of the reverse pumping signal fiber laser beam combiner is connected with a semiconductor laser pumping source; and the output end of the optical fiber power amplifier is sequentially connected with the second cladding light filter and the laser output head.

2. The L-band high power ytterbium-doped fiber laser of claim 1, wherein the laser is of MOPA or single cavity construction.

3. The L-band high power ytterbium-doped fiber laser of claim 2, wherein the laser is of MOPA structure, the seed source is a fiber laser, a solid laser or a semiconductor laser, and the fiber power amplifier is of single-stage structure or is formed by cascading multiple stages of amplifiers.

4. The L-band high power ytterbium-doped fiber laser of claim 2, wherein the laser has a single-cavity structure, a high-reflectivity fiber grating is disposed between the double-clad ytterbium-doped fiber and the forward combiner, and a partially-reflective fiber grating is disposed between the triple-clad ytterbium-doped fiber and the backward combiner, and the high-reflectivity fiber grating and the partially-reflective fiber grating together form a laser cavity.

5. The L-band high-power ytterbium-doped fiber laser adopting bidirectional pump hybrid pumping as claimed in claim 4, wherein the center wavelength of the high-reflectivity fiber grating and the partial-reflectivity fiber grating is a laser signal wavelength, the reflectivity of the high-reflectivity fiber grating is greater than 99%, the reflectivity of the partial-reflectivity fiber grating is between 0 and 99%, and the reflection bandwidth of the high-reflectivity fiber grating and the reflection bandwidth of the partial-reflectivity fiber grating are both between 0 and 10 nm.

6. The L-band high power ytterbium-doped fiber laser of claim 1, wherein the laser has an operating wavelength >1100nm and is the L-band in the spectrum of the stimulated emission of ytterbium ions.

7. The L-band high power ytterbium-doped fiber laser of claim 1, wherein the gain fiber used in the laser is formed by cascading a section of double-clad ytterbium-doped fiber and a section of triple-clad ytterbium-doped fiber, wherein the diameters and NAs of the core and the first inner cladding of the triple-clad ytterbium-doped fiber are respectively the same as the diameters and NAs of the core and the first inner cladding of the double-clad ytterbium-doped fiber.

8. The L-band high power ytterbium-doped fiber laser of claim 1, wherein the fiber power amplifier is bi-directionally pumped, the forward pump source is a high brightness fiber laser pump source with a pump wavelength between 1000nm and 1100nm, the reverse pump is a semiconductor laser pump source with a pump wavelength between 900nm and 1000 nm.