CN209929673U - Bidirectional pumping double-cladding optical fiber laser amplifier with SBS (styrene-butadiene-styrene) inhibiting function - Google Patents

Abstract

The utility model relates to an optical fiber laser field, for SBS threshold value in improving optical fiber laser MOPA, the lowering system complexity realizes efficient laser output, the utility model discloses, two-way pumping double-clad fiber laser amplifier with restrain SBS effect, include: the device comprises a laser seed source, an optical fiber isolator, a first optical fiber combiner, a first double-cladding active optical fiber, a cladding light stripper, a second double-cladding active optical fiber, a second optical fiber combiner, an optical fiber end cap and a pumping source; seed light enters the fiber core of the first double-cladding active optical fiber through the optical fiber isolator and then enters the fiber core of the second double-cladding active optical fiber through the cladding light stripper; the pump light emitted by the pump source is coupled into the cladding of the first active fiber and the cladding of the second active fiber in a positive and negative way through the pump ends of the first optical fiber beam combiner and the second optical fiber beam combiner respectively; the double-cladding active optical fiber absorbs the pump light, provides gain for the signal light and then outputs the signal light. The utility model discloses mainly be applied to laser instrument manufacturing and designing occasion.

Description

Bidirectionally Pumped Double-Clad Fiber Laser Amplifier with SBS Suppression

technical field

The utility model relates to the field of fiber laser, in particular to a bidirectional pumping double-clad fiber laser amplifier with the function of suppressing SBS.

Background technique

In order to obtain high-power, high-performance fiber laser output, a master oscillator power amplifier (MOPA) structure with double-clad active fiber as the gain medium is usually used. At present, the commonly used fiber amplifier pumping structures include forward pumping, reverse pumping and bidirectional pumping. Amplifiers with forward pumping structure have higher output optical signal-to-noise ratio but lower slope efficiency. The reverse pumping structure can achieve higher slope efficiency, and has a certain inhibitory effect on nonlinear effects, but there is a problem of strong stimulated spontaneous emission (ASE), and the output signal-to-noise ratio is low. Bidirectional pumping combines the advantages of the first two pumping structures, and has relatively high slope efficiency and signal-to-noise ratio. It is the best pumping structure for realizing high-power narrow-linewidth laser output. It has been used in single-clad fiber amplifiers. has been widely used. However, in the double-clad fiber laser amplifier, the pump light is coupled into the inner cladding of the active fiber through the fiber combiner for pumping. Residual pump light to avoid damage to subsequent devices. When the bidirectional pump structure is adopted, two cladding optical strippers are required to remove the forward and reverse residual pump light respectively, which inevitably increases the laser link loss and the complexity of the amplification system.

In addition, nonlinear effects in fibers, such as stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), etc., are one of the main factors limiting the power level of fiber lasers. Especially in high-power narrow-linewidth fiber laser amplifiers, due to the extremely narrow linewidth of the signal light, the SBS phenomenon is prone to occur, which affects the output slope efficiency and signal-to-noise ratio. In the existing technology, in order to suppress the SBS effect, it is necessary to add a temperature gradient or stress gradient to the double-clad gain fiber through external equipment, or use a high-priced large-mode field area double-clad active fiber for amplification. The cost is high, and the structure of the amplification system is complex.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the present utility model aims to propose a bidirectionally pumped double-clad fiber laser amplifier that suppresses the SBS effect, improves the SBS threshold in the fiber laser MOPA, reduces the system complexity, and realizes high-efficiency laser output, which is Therefore, the technical solution adopted by the present invention is a bidirectionally pumped double-clad fiber laser amplifier with the effect of suppressing SBS, including: a laser seed source, a fiber isolator, a first fiber combiner, a first double-clad active Optical fiber, cladding light stripper, second double-cladding active fiber, second fiber combiner, fiber end cap and pump source; the laser seed source emits signal light, and the seed light enters through the fiber isolator The core of the first double-clad active fiber enters the second double-clad active fiber core through the cladding optical stripper; the pump light emitted by the pump source passes through the The pumping ends of the first and second fiber combiners are coupled forward and reversely into the cladding of the first and second active fibers to realize bidirectional pumping; the double-clad active fibers absorb the pump light, The particle number inversion is formed to provide gain to the signal light; the signal light is amplified, and the amplified signal light is output through the signal end of the second fiber combiner and the fiber end cap.

The optical fibers at the input end and the output end of the cladding optical stripper are the matching fibers of the first and second double-clad active fibers, respectively, and are placed between the first and second double-clad active fibers, and are used for The residual pump light of forward and reverse transmission is stripped off, and the core diameter of the fiber at the input end is smaller than that of the fiber at the output end, so as to improve the reverse transmission loss of the Stokes light.

The first double-clad active fiber and the second double-clad active fiber can be erbium-ytterbium co-doped fibers or active fibers doped with activated ions of erbium, ytterbium, thulium, holmium or neodymium, corresponding to different wavelength of the signal light.

The laser seed source can be a fiber laser or a semiconductor laser, as long as its emission wavelength is within the gain spectrum of the first and second double-clad active fibers; the laser seed source can be continuous wave operation or It operates in modulation, Q-switched or mode-locked mode.

The features and beneficial effects of the present utility model are:

The residual pump light transmitted in the forward and reverse directions is simultaneously stripped by a single cladding optical stripper to realize bidirectional pumping of double-cladding active fibers. The input and output fiber core diameters of the cladding optical stripper are different, which can improve the Stokes optical transmission loss, increase the SBS threshold of the amplifier, and effectively suppress the SBS effect in the amplifier. The amplifier does not require other additional equipment, and has a simple and compact structure, which is helpful for realizing laser output with high power, high signal-to-noise ratio and narrow linewidth.

Description of drawings:

1 is a specific embodiment of a bidirectionally pumped double-clad fiber laser amplifier with the effect of suppressing SBS provided by the utility model, and FIG. 2 is a schematic structural diagram of a component cladding optical stripper 5 in the amplifier of the present utility model;

In the accompanying drawings, the list of components represented by each number is as follows:

1: Laser seed source; 2: Fiber isolator;

3: The first fiber combiner; 4: The first double-clad active fiber;

5: Cladding optical stripper; 6: Second double-clad active fiber;

7: Second fiber combiner; 8: Fiber end cap;

9: Pump source; 10: Input fiber of cladding light stripper 5

11: Output fiber of cladding light stripper 5; 12: High refractive index matching glue;

13; heat sink.

Detailed ways

A bidirectionally pumped double-clad fiber laser amplifier with the function of suppressing SBS, the fiber laser amplifier comprises: a laser seed source, a fiber isolator, a first fiber combiner, a first double-clad active fiber, a cladding Optical stripper, second double-clad active fiber, second fiber combiner, fiber end cap and pump source. The laser seed source emits signal light, and the seed light enters the core of the first double-clad active fiber through the fiber isolator, and then enters the second double-clad fiber through the cladding light stripper. source fiber core. The pump light emitted by the pump source is coupled into the cladding layers of the first and second active fibers through the pump ends of the first and second fiber combiners respectively, so as to realize bidirectional pumping. The double-clad active fiber absorbs the pump light, forms population inversion, and provides gain to the signal light. The signal light is amplified, and the amplified signal light is output through the signal end of the second fiber combiner and the fiber end cap.

The optical fibers at the input end and the output end of the cladding optical stripper are the matching fibers of the first and second double-clad active fibers, respectively, and are placed between the first and second double-clad active fibers, and are used for The residual forward and reverse propagating pump light is stripped. And the core diameter of the fiber at the input end is smaller than that of the fiber at the output end, which is used to improve the reverse transmission loss of the Stokes light.

During the amplification process, when Brillouin scattering occurs in the second double-cladding active fiber, only a small amount of reversely propagating Stokes light is coupled into the first double-cladding active fiber through the cladding light stripper. Avoid its high gain to form lasing, so that the SBS effect in the amplifier can be suppressed.

In order to make the objectives, technical solutions and advantages of the present utility model more clear, the embodiments of the present utility model will be further described in detail below with reference to the accompanying drawings.

The embodiment of the present utility model provides a bidirectionally pumped double-clad fiber laser amplifier with the function of suppressing SBS. The structure of the fiber laser amplifier is shown in FIG. 1. In the implementation of the present utility model, the positive and negative The residual pump light to be transmitted is simultaneously stripped to realize bidirectional pumping of double-clad active fibers. The fiber core diameters at the input and output ends of the cladding optical stripper are different, which can improve the Stokes light transmission loss and suppress the SBS effect in the amplifier. See the description below for details:

The fiber laser amplifier includes: a laser seed source 1, a fiber isolator 2, a first fiber combiner 3, a first double-clad active fiber 4, a cladding optical stripper 5, and a second double-clad active fiber 6. The second fiber combiner 7 , the fiber end cap 8 , and the pump source 9 . in,

The output wavelength of the laser seed source 1 is 1550nm, and the output fiber is 6/125 single-mode fiber; the fiber isolator 2 is a fiber coupling device, and the fiber core diameter is 6 μm; the first fiber combiner 3 is a (2+1)×1 fiber combination. bundler, the signal fiber is a 6/125 double-clad fiber, and the pump end fiber is a 105/125 multimode fiber; the first double-clad active fiber 4 is an erbium-ytterbium co-doped fiber, and the core and inner cladding diameters are 6μm and 125μm; the optical fiber 10 at the input end of the cladding optical stripper 5 is a 6/125 double-clad passive fiber, which is the matching fiber of the first double-clad active fiber 4, and the fiber core diameter is 6 μm. The output fiber 12 is a 12/130 double-clad passive fiber, which is a matching fiber of the second double-clad active fiber 6, and the fiber core diameter is 12 μm. The bare fiber near the fusion point between the input optical fiber 10 and the output optical fiber 11 of the cladding optical stripper 5 is coated with a high refractive index glue 12, and the coating length is not less than 6 cm, and the fusion point is placed on the heat sink 13. The second double-clad active fiber 6 is an erbium-ytterbium co-doped fiber, the core and inner cladding diameters are 12 μm and 130 μm respectively; the second fiber combiner 7 is a (2+1)×1 fiber combiner, the signal fiber It is a 12/130 double-clad fiber, and the pump end fiber is a 105/125 multimode fiber. The output wavelength of the pump source 9 is 976 nm, and the coupling output fiber is a 105/125 multimode fiber.

The laser seed source 1 emits seed light, which enters the first double-clad active fiber 4 through the fiber isolator 2 . The pump light emitted by the pump source 9 forwardly pumps the first double-clad active fiber 4 through the first fiber combiner 3 . The amplified signal enters the second double-clad active fiber 6 through the cladding optical stripper 5 . The pump source 9 reversely pumps the second double-clad active fiber 6 through the second fiber combiner 7 to realize bidirectional pumping. The finally amplified signal is output through the signal end of the second fiber combiner 7 and the fiber end cap 8 .

During the amplification process, the cladding light stripper 5 simultaneously strips the residual pump light transmitted in the forward and reverse directions to realize bidirectional pumping. When Brillouin scattering occurs in the second double-clad active fiber 6, since the core diameter of the fiber 10 at the input end of the cladding light stripper 5 is smaller than the core diameter of the fiber 11 at the output end, there is only a small amount of reversely transmitted Stokes The light is coupled into the first double-clad active fiber 4 through the cladding optical stripper 5, so as to avoid the formation of lasing due to its high gain, so that the SBS effect in the amplifier can be suppressed.

The first double-clad active fiber 4 and the second double-clad active fiber 6 may be erbium-ytterbium co-doped fibers, or active ions doped with erbium, ytterbium, thulium, holmium, neodymium and other commonly used active ions. The optical fibers respectively correspond to different signal light wavelengths, which are not limited in the embodiment of the present invention.

The core diameter of the second double-clad active fiber 6 only needs to be larger than the core diameter of the first double-clad active fiber 4, which is not limited in the embodiment of the present invention.

Wherein, the laser seed source 1 can be a fiber laser, or a semiconductor laser or other laser, as long as its emission wavelength is located within the gain spectrum of the first and second double-clad active fibers 4 and 6, the utility model The novel embodiment does not limit this.

Wherein, the laser seed source 1 may operate in continuous wave operation, or may operate in other forms such as modulation, Q-switching, mode locking, etc., which is not limited in the embodiment of the present invention.

Among them, the pump source 9 can be a semiconductor laser, or other forms of lasers such as optical fibers, solids, etc., and its output wavelength can be 976 nm or 915 nm, and other wavelengths can also be used when using active fibers doped with other ions , as long as it corresponds to the absorption peak of the active fiber, which is not limited in the embodiment of the present invention.

To sum up, the embodiments of the present utility model provide a bidirectionally pumped double-clad fiber laser amplifier with the effect of suppressing SBS, and the bi-directional pumping of the double-clad fiber amplifier is realized by connecting gain fibers at both ends through a cladding optical stripper. ; The core diameter of the optical fiber at the input and output ends of the cladding optical stripper is different, which can improve the transmission loss of Stokes light and suppress the SBS effect in the fiber amplifier. The method does not need other devices, and has the advantages of simple structure, high signal-to-noise ratio and high output efficiency.

Those skilled in the art can understand that the accompanying drawing is only a schematic diagram of a preferred embodiment, and the above-mentioned serial numbers of the embodiments of the present invention are only for description, and do not represent the advantages and disadvantages of the embodiments.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection of the utility model.

Claims (4)

1. A bidirectional pumping double-clad fiber laser amplifier with SBS suppressing function is characterized by comprising: the device comprises a laser seed source, an optical fiber isolator, a first optical fiber combiner, a first double-cladding active optical fiber, a cladding light stripper, a second double-cladding active optical fiber, a second optical fiber combiner, an optical fiber end cap and a pumping source; the laser seed source emits signal light, and the seed light enters the fiber core of the first double-cladding active optical fiber through the optical fiber isolator and then enters the fiber core of the second double-cladding active optical fiber through the cladding light stripper; the pump light emitted by the pump source respectively enters the cladding of the first active fiber and the cladding of the second active fiber through the forward and backward coupling of the pump ends of the first fiber combiner and the second fiber combiner to realize bidirectional pumping; the double-clad active optical fiber absorbs the pump light to form population inversion, and gain is provided for the signal light; and amplifying the signal light, and outputting the amplified signal light through the signal end of the second optical fiber beam combiner and the optical fiber end cap.

2. The laser amplifier as claimed in claim 1, wherein the input and output fibers of the cladding light stripper are respectively matched fibers of the first and second double-clad active fibers, and are disposed between the first and second double-clad active fibers for stripping residual pump light transmitted in forward and reverse directions, and the core diameter of the input fiber is smaller than that of the output fiber for increasing the reverse transmission loss of stokes light.

3. The two-way pumped double-clad fiber laser amplifier according to claim 1, wherein the first double-clad active fiber and the second double-clad active fiber are erbium-ytterbium co-doped fibers or active fibers doped with active ions of erbium, ytterbium, thulium, holmium or neodymium, respectively corresponding to different wavelengths of signal light.

4. The two-way pumped double-clad fiber laser amplifier with SBS suppressing function as claimed in claim 1, wherein the laser seed source is a fiber laser or a semiconductor laser, only if its emission wavelength is within the gain spectrum of the first and second double-clad active fibers; the laser seed source is operated in continuous wave mode or in modulation, Q-switching or mode-locking mode.

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