High-power and high-stability 1018nm fiber laser

Abstract

The utility model provides a high-power and high-stability 1018nm fiber laser. The high-power and high-stability 1018nm fiber laser comprises a pumping source, a pumping signal beam combiner, a high-reflection grating, an ytterbium-doped fiber, a low-reflection grating, a cladding light stripper and a fiber output head, the pumping source is used for providing pumping light for the optical fiber laser, the pumping signal beam combiner is used for injecting the pumping light into the ytterbium-doped optical fiber, the pumping signal beam combiner is further provided with a signal fiber, and the signal fiber is connected with the cladding light stripper and provided with a bevel cutting angle. The ytterbium-doped fiber laser adopts the ytterbium-doped fiber with the large cladding diameter, is favorable for realizing higher pumping power injection, and improves the upper limit of the output power of the laser. A forward pumping scheme is adopted, so that internal reflection in an optical fiber path is reduced, ASE is favorably suppressed, the stability of the laser is improved, and the structure of the laser is simpler. Appropriate high and low reflective gratings are used, which is beneficial to inhibiting ASE and improving the stability of the laser.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber lasers, and in particular to a high-power and high-stability 1018nm optical fiber laser. Background Art

[0002] Cascade pumping technology can achieve better beam quality while achieving high-power laser output, and 1018nm fiber laser is an important pump source for high-power cascade pumped laser systems. The single-fiber output power and stability of 1018nm lasers directly affect the cost and stability of high-power cascade pumped laser systems. Since the 1018nm band is located in the short-wave region of the ytterbium ion emission spectrum, the signal emission coefficient in this region is much smaller than that in the long-wave region, and ytterbium ions also have certain absorption in this region, so the 1018nm laser signal faces gain competition with amplified spontaneous emission (ASE) near 1035nm.

[0003] The current technical solution for 1018nm fiber laser oscillators generally uses a 976nm semiconductor laser as a pump source, and the gain medium is generally an ytterbium-doped fiber with a large core / cladding ratio. Use an N×1 pump combiner or a (N+1)×1 pump-signal combiner to inject the pump light into the ytterbium-doped fiber. A low-reflection grating and a high-reflection grating with a central wavelength of 1018nm are used as cavity mirrors, and the two gratings and the ytterbium-doped fiber together form a laser resonant cavity. The cladding light stripper (CPS) behind the low-reflection grating strips the light in the cladding to the outside of the fiber. The output end of the laser is connected to a quartz end cap (QBH), or the fiber is cut at an angle of 5 to 10 degrees for direct output.

[0004] The Chinese patent number is CN208986362U, and the name is "A 1018nm fiber laser". The laser adopts an extracavity forward pumping scheme, and the ytterbium-doped fiber used has a cladding diameter of 130μm. The central wavelength of the low-reflection grating and the high-reflection grating is 1018nm. However, the 130μm fiber pump injection power is limited and only supports a power output of hundreds of watts. In addition, the small core-to-clad ratio fiber is not conducive to ASE suppression, and the laser stability is poor.

[0005] In order to solve the problem of low laser output power and ASE suppression in patent number CN208986362U, Ping Yan et al. from Tsinghua University used a wavelength-locked 976nm pump source and adopted a bidirectional pumping scheme. The optical fiber used a ytterbium-doped fiber with a cladding diameter of 250μm and a high core-to-cladding ratio, which is helpful for ASE suppression. Finally, a single-fiber 1150W 1018nm laser output was achieved, with an optical efficiency of 79.5% and an ASE suppression ratio of about 40dB. Used as a pump source for cascade pump lasers, according to test experience, the ASE suppression ratio should be no less than 45dB to ensure its stability during high-power laser output. The experimental results of Tsinghua University showed an ASE suppression ratio of 40dB, and its stability still needs to be improved. Since the reverse signal pump combiner is inserted into the resonant cavity, the bidirectional pumping increases the internal reflection in the optical fiber path, which is not conducive to ASE suppression. Therefore, the ASE suppression capability of the bidirectional pumping scheme is not optimal. Furthermore, due to the use of a wavelength-locked 976nm pump source, the laser is expensive and not suitable for mass production. Utility Model Content

[0006] In view of this, the utility model provides a high-power and high-stability 1018nm fiber laser to solve the above problems.

[0007] In order to solve the above technical problems, the utility model provides a high-power and high-stability 1018nm fiber laser, including:

[0008] Pump source, pump signal combiner, high reflection grating, ytterbium-doped fiber, low reflection grating, cladding light stripper and fiber output head;

[0009] The pump source is used to provide pump light for the fiber laser, the pump signal combiner is used to inject the pump light into the ytterbium-doped fiber, the pump signal combiner is also provided with a signal fiber, the signal fiber is connected to the cladding light stripper, and is provided with a bevel angle.

[0010] As an option, the pump source is a high power 976mm pump source.

[0011] As an optional manner, the pump signal combiner is a (N+1)*1 pump signal combiner.

[0012] As an optional manner, the signal fiber connection cladding optical stripper has a bevel angle of 5-10°.

[0013] As an optional method, the optical fibers of the high-reflection grating and the low-reflection grating are passive optical fibers with the same specifications as the ytterbium-doped optical fibers.

[0014] As an optional method, the optical fiber output head is connected with a quartz end cap or is directly beveled, and the bevel angle is 5-10°.

[0015] As an option, the cladding diameter of the Ytterbium-doped fiber is 250 μm.

[0016] As an optional method, the central wavelength of the high-reflection grating is 1018nm, and the reflectivity is greater than 99%; the central wavelength of the low-reflection grating is 1018nm, and the reflectivity is 10-20%.

[0017] The beneficial effects of the utility model are:

[0018] The utility model adopts a large cladding diameter ytterbium-doped optical fiber, which is conducive to achieving greater pump power injection and improving the upper limit of the laser output power. The forward pumping scheme is adopted: reducing the internal reflection in the optical fiber path is conducive to suppressing ASE, improving the stability of the laser, and making the laser structure simpler. Using appropriate high and low reflection gratings is conducive to suppressing ASE and improving the stability of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure of a high-power and high-stability 1018nm fiber laser provided in an embodiment of the utility model;

[0020] Figure 2 Output power curve and optical efficiency curve of the 1018nm fiber laser provided in the embodiment of the utility model;

[0021] Figure 3 This is the output spectrum of the 1018nm fiber laser provided in the embodiment of the utility model.

[0022] Reference numerals and their corresponding relationships:

[0023] 1- pump source, 2- beam combiner, 3- high reflection grating, 4- ytterbium-doped fiber, 5- low reflection grating, 6- first cladding light stripper, 7- second cladding light stripper, 8- fiber output head, 9- signal fiber. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0025] See also Figure 1-Figure 3 The present embodiment provides a high-power and high-stability 1018nm fiber laser, including: a pump source, a pump signal combiner, a high-reflection grating, an ytterbium-doped fiber, a low-reflection grating, a cladding light stripper and a fiber output head; the pump source is used to provide pump light for the fiber laser, the pump signal combiner is used to inject the pump light into the ytterbium-doped fiber, the pump signal combiner is also provided with a signal fiber, the signal fiber is connected to the cladding light stripper, and is provided with a bevel angle.

[0026] Please refer again Figure 1In an optional manner, the 1018nm fiber laser of this embodiment is mainly composed of a high-power 976nm pump source 1, a (N+1)×1 pump signal combiner 2, a high-reflection grating 3, an ytterbium-doped fiber 4, a low-reflection grating 5, a first cladding light stripper 6, a second cladding light stripper 7 and a fiber output head 8. Among them, 9 is a signal fiber of the (N+1)×1 pump signal combiner 2.

[0027] In this embodiment, a high-power 976nm pump source 1 provides pump light for the system, and a (N+1)×1 pump signal combiner 2 is used to inject pump light into the ytterbium-doped optical fiber 4. The signal fiber 9 of the combiner is connected to the CPS 7 and cut at an angle of 5 to 10°. The optical fiber of the high-reflection grating 3 adopts a passive optical fiber with the same specifications as the ytterbium-doped optical fiber, with a central wavelength of 1018nm, a reflectivity greater than 99%, and a large side mode suppression ratio. The optical fiber of the low-reflection grating 5 adopts a passive optical fiber with the same specifications as the ytterbium-doped optical fiber, a central wavelength the same as the high-reflection grating 3, a reflectivity between 10% and 20%, and a large side mode suppression ratio. The active optical fiber cladding diameter is about 250μm. The cladding light stripper 6 (CPS) is used to strip off the signal light leaking into the cladding and the residual pump light not absorbed by the active optical fiber. The output end of the laser is connected to the quartz end cap 8 or the optical fiber is directly cut at an angle of 5 to 10°.

[0028] Through the above design, the working process of this embodiment is as follows:

[0029] The 976nm pump source 1 outputs pump light, which is injected into the double-clad passive fiber with the same specifications as the ytterbium-doped fiber through the beam combiner 2. The pump light enters the ytterbium-doped fiber 4 after passing through the high-reflection grating 3. After the ytterbium ions absorb the pump light, the population inversion occurs, and a wide-spectrum amplified spontaneous radiation with a wavelength range of 980nm to 1100nm is generated. After the longitudinal mode selection effect of the high-reflection grating 3 and the low-reflection grating 5, the gain of many longitudinal modes near 1018nm in the entire cavity is the largest, and the optical signals in other bands have a large loss, so a laser signal with a central wavelength of 1018nm is finally formed. Since there is a small amount of unabsorbed pump light in the system, a small amount of signal light will also leak into the cladding due to bending, so the cladding light stripper 6 after the low-reflection grating 5 strips the light in the cladding out of the fiber. The output end of the laser can be connected to a quartz end cap or the optical fiber can be directly beveled.

[0030] Since the 1018nm band is located in the short-wave region of the ytterbium ion emission spectrum, the signal emission coefficient in this region is much smaller than that in the long-wave region, and ytterbium ions also have certain absorption in this region. Therefore, even under the longitudinal mode selection conditions of two gratings with a central wavelength of 1018nm, the 1018nm laser signal still faces gain competition with ASE near 1035nm. In order to weaken the ASE gain, a grating with a higher side mode suppression ratio is used. While achieving a kilowatt-level 1018nm laser output, a high ASE suppression ratio is obtained, which improves the stability of the laser.

[0031] like Figure 2 As shown in the output power curve and optical efficiency curve of the 1018nm fiber laser of the present invention, when the pump power is 1600W, the laser output power is 1280W and the optical efficiency is 80%.

[0032] like Figure 3 As shown, the output spectrum of the 1018nm fiber laser of the present invention has a spectrum ASE suppression ratio of 47dB when the output power is 1280W.

[0033] Thus, this embodiment 1) improves output power and optical efficiency: uses ytterbium-doped optical fiber with a large cladding diameter to achieve higher pump power injection and increase the upper limit of output laser power. Ultimately, a single-fiber kilowatt-level (1280W) 1018nm laser output is achieved with an optical efficiency of 80%.

[0034] 2) Improve the stability of the laser: By adopting a forward pumping scheme, the internal reflection in the fiber path is reduced; using a grating with a high side mode suppression ratio, ASE is effectively suppressed. While outputting a single-fiber kilowatt-level 1018nm laser, the stability of the laser is improved, and the ASE suppression ratio is as high as 47dB.

[0035] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention. The protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A high-power and high-stability 1018nm fiber laser, characterized in that: include: A pump source (1), a pump signal combiner (2), a high-reflection grating (3), an ytterbium-doped optical fiber (4), a low-reflection grating (5), a cladding light stripper and an optical fiber output head (8); The pump source (1) is used to provide pump light for the fiber laser, the pump signal combiner (2) is used to inject the pump light into the ytterbium-doped fiber (4), and the pump signal combiner (2) is also provided with a signal fiber (9), the signal fiber (9) is connected to the cladding light stripper and is provided with a bevel angle.

2. A high-power and high-stability 1018nm fiber laser according to claim 1, characterized in that: The pump source (1) is a high-power 976 mm pump source (1).

3. A high-power and high-stability 1018nm fiber laser according to claim 1, characterized in that: The pump signal beam combiner (2) is a (N+1)*1 pump signal beam combiner (2).

4. The high-power and high-stability 1018nm fiber laser according to claim 1, characterized in that: The signal fiber (9) connected to the cladding light stripper has a bevel angle of 5-10°.

5. The high-power and high-stability 1018nm fiber laser according to claim 1, characterized in that: The optical fibers of the high-reflection grating (3) and the low-reflection grating (5) are both passive optical fibers with the same specifications as the ytterbium-doped optical fiber (4).

6. A high-power and high-stability 1018nm fiber laser according to claim 1, characterized in that: The optical fiber output head (8) is connected to a quartz end cap or is directly beveled, and the bevel angle is 5-10°.

7. The high-power and high-stability 1018nm fiber laser according to claim 1, characterized in that: The cladding diameter of the ytterbium-doped optical fiber (4) is 250 μm.

8. The high-power and high-stability 1018nm fiber laser according to claim 5, characterized in that: The central wavelength of the high-reflection grating (3) is 1018 nm, and the reflectivity is greater than 99%; the central wavelength of the low-reflection grating (5) is 1018 nm, and the reflectivity is 10-20%.

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