1018nm optical fiber laser oscillator

Abstract

A 1018nm optical fiber laser oscillator comprises a pumping source module, a high-reflectivity optical fiber grating, a gain optical fiber and a low-reflectivity optical fiber grating, and the gain optical fiber is an ytterbium-doped optical fiber; the high-reflectivity fiber bragg grating, the gain fiber and the low-reflectivity fiber bragg grating are sequentially connected to form an oscillation cavity, and the grating center wavelength of the high-reflectivity fiber bragg grating and the grating center wavelength of the low-reflectivity fiber bragg grating are 1018nm; the pumping source module outputs pumping light with the working wavelength of 915 nm, the pumping source module is connected with the high-reflectivity fiber bragg grating, the pumping light is coupled into the oscillation cavity, and more than one chirp inclined grating with high loss on ASE (Amplified Spontaneous Emission) at the wave band of 1030-1080 nm is inscribed in a fiber core of the ytterbium-doped fiber. According to the utility model, the laser can stably operate in a wider temperature range, effective suppression of amplified spontaneous radiation is realized, a 1018nm fiber laser oscillator can use a longer gain fiber, and it is ensured that the efficiency of the laser is not affected.

Description

Technical Field

[0001] The utility model belongs to the technical field of optical fiber lasers, in particular to a 1018nm optical fiber laser oscillator. Background Art

[0002] High-power ytterbium-doped fiber lasers have been widely used in industries such as industry and defense due to their compact structure, high brightness, and flexible transmission. Cascade pumping offers advantages such as high pump beam brightness, low quantum loss, low fiber thermal load, and a high threshold for mode instability. It is the primary technical solution for achieving high-quality, 10,000-watt fiber lasers.

[0003] Cascade pumping first uses an electrically driven semiconductor laser (LD) to pump an ytterbium-doped fiber to generate a 1018 nm fiber laser. Multiple 1018 nm fiber lasers are then used as pump lasers to secondary pump the ytterbium-doped fiber to achieve ultra-high-power laser output in the 1060-1100 nm band. As the pump source for this cascade-pumped fiber laser, a high-power, high-efficiency, and highly stable 1018 nm fiber oscillator is essential for achieving high-power cascade pumping. However, because 1018 nm is at the edge of the ytterbium ion gain spectrum, the generation of 1018 nm lasers faces gain competition from amplified spontaneous emission (ASE) in the 1030-1080 nm band, making parasitic oscillations highly likely to occur, seriously impacting the normal operation of the laser oscillator.

[0004] To suppress ASE and parasitic oscillation, the length of the ytterbium-doped fiber is typically shortened to reduce the gain in the 1030-1080 nm band, ensuring proper light output from the 1018 nm oscillator. Due to the shortened length of the ytterbium-doped fiber, to ensure adequate absorption of the pump light and laser efficiency, the 1018 nm oscillator primarily uses a 976 nm laser diode (LD), which has the highest ytterbium ion absorption coefficient, as a pump source to pump the ytterbium-doped fiber. However, the ytterbium ion absorption spectrum near 976 nm is steep, and the absorption coefficient varies significantly with wavelength. As the LD's operating wavelength varies with temperature (approximately 0.3 nm / °C), the drift in its center wavelength causes the pump light absorption coefficient of the ytterbium-doped fiber to drop rapidly, significantly impacting the output power stability and efficiency of the 1018 nm oscillator. Therefore, for 1018 nm fiber laser oscillators pumped by 976 nm LDs, maintaining output power stability requires strict control over the operating temperature range (typically 3-5°C). Even when using a wavelength-locked 976nm LD, its operating temperature range generally does not exceed 15°C, which greatly restricts the application of 1018nm ytterbium-doped fiber oscillators and high-power cascade-pumped fiber lasers in environments with large temperature changes.

[0005] To reduce the impact of LD wavelength drift on the stability of a 1018nm ytterbium-doped fiber oscillator, an LD with a wavelength near 915nm can be used as the pump source. Because the ytterbium ion absorption spectrum in the 900-950nm band is relatively flat and the absorption coefficient varies only slightly with wavelength, temperature-induced LD wavelength drift does not significantly affect the laser's efficiency and power stability. However, the ytterbium ion absorption coefficient near 915nm is only approximately one-third of that at 976nm, and the ytterbium-doped fiber is relatively short. Therefore, the efficiency of a 1018nm ytterbium-doped fiber oscillator pumped by a 915nm LD is extremely low, significantly limiting its ability to achieve high-power, high-efficiency laser output.

[0006] Therefore, starting from the system structure design of the 1018nm fiber laser oscillator itself, broadening the temperature range in which it can operate stably with high power and high efficiency has important practical application value. Utility Model Content

[0007] In response to the problem that existing 1018nm ytterbium-doped fiber oscillators are difficult to operate in a wide temperature range, the utility model proposes a 1018nm fiber laser oscillator that can operate stably with high power, high efficiency, and in a wider operating temperature range. It is suitable for special environments with large ambient temperature changes.

[0008] In order to achieve the above technical purpose, the technical solution adopted by this utility model is:

[0009] A 1018nm fiber laser oscillator includes a pump source module, a high-reflectivity fiber Bragg grating (FBG), a gain fiber, and a low-reflectivity fiber Bragg grating (FBG), wherein the gain fiber is an ytterbium-doped fiber. The high-reflectivity fiber Bragg grating, the gain fiber, and the low-reflectivity fiber Bragg grating are sequentially connected to form an oscillation cavity. The grating center wavelengths of the high-reflectivity fiber Bragg grating and the low-reflectivity fiber Bragg grating are 1018nm. The pump source module outputs pump light with an operating wavelength of 915nm. The pump source module is connected to the high-reflectivity fiber Bragg grating to couple the pump light into the oscillation cavity. The core of the ytterbium-doped fiber is inscribed with one or more chirped tilted gratings with high loss to ASE in the 1030-1080nm band.

[0010] Furthermore, the pump source module includes one or more semiconductor lasers with a wavelength of 915 nm.

[0011] Furthermore, the pigtail of the semiconductor laser is a multimode optical fiber or a passive double-clad optical fiber.

[0012] Furthermore, when the pump source module includes N semiconductor lasers and N is greater than or equal to 2, the pigtail of the semiconductor laser is a multimode optical fiber, and the output pigtails of the N semiconductor lasers 1 correspond to the N input arms of the N×1 pump combiner, and the output arms of the N×1 pump combiner are fused to high-reflectivity fiber Bragg gratings.

[0013] Furthermore, the output end of the low-reflectivity fiber Bragg grating is fused with a cladding light stripper to output a 1018 nm laser.

[0014] Furthermore, the ytterbium-doped optical fiber is a double-clad ytterbium-doped optical fiber.

[0015] Furthermore, the high-reflectivity fiber Bragg grating is inscribed in the core of a passive double-clad optical fiber, and the low-reflectivity fiber Bragg grating is inscribed in the core of a passive double-clad optical fiber, and the model of the passive double-clad optical fiber for inscribed high-reflectivity fiber Bragg grating is the same as the model of the passive double-clad optical fiber for inscribed low-reflectivity fiber Bragg grating.

[0016] Furthermore, the diameters of the core and cladding of the double-clad ytterbium-doped optical fiber and the numerical aperture thereof match those of the core and cladding of the passive double-clad optical fiber for writing high-reflectivity fiber Bragg gratings.

[0017] Preferably, one or more chirped tilted fiber gratings (CTFBGs) with high loss to ASE in the 1030-1080 nm band are written into the core of the ytterbium-doped optical fiber by femtosecond or ultraviolet writing technology.

[0018] Compared with the prior art, the beneficial technical effects that this utility model can produce are:

[0019] By incorporating a CTFBG into an ytterbium-doped fiber, this invention reduces ASE loss in the 1030-1080nm band, addressing the limitations imposed by the length of the ytterbium-doped fiber in 1018nm fiber laser oscillators on ASE gain. This increased ytterbium-doped fiber length allows high conversion efficiency to be achieved even when pumping a 1018nm ytterbium-doped fiber oscillator using a 915nm laser diode (LD) with a lower absorption coefficient. Because the absorption coefficient of ytterbium ions near 915nm varies only slightly with wavelength, temperature-induced LD wavelength drift will not significantly affect laser efficiency and output power stability when the laser's ambient temperature fluctuates significantly. Therefore, the 1018nm fiber laser oscillator of this invention can operate stably and efficiently over a wider temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of the optical path structure of a 1018nm fiber laser oscillator provided in one embodiment;

[0022] Figure 2 It is a schematic diagram of suppressing amplified spontaneous emission in the 1030-1080 nm band;

[0023] Numbers in the figure:

[0024] 1. Semiconductor laser; 2. N×1 pump combiner; 3. High-reflectivity fiber Bragg grating; 4. Ytterbium-doped fiber; 5. Low-reflectivity fiber Bragg grating; 6. Cladding light stripper; 7. Fusion point.

[0025] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0026] Aiming at the problem that the existing 1018nm ytterbium-doped fiber laser oscillator pumped by 976nm semiconductor laser cannot operate stably in a wide temperature range, the utility model proposes a new solution of 1018nm high-efficiency fiber laser oscillator pumped by 915nm semiconductor laser that can operate in a wide temperature range.

[0027] A 1018nm fiber laser oscillator provided in one embodiment includes a pump source module, a high-reflectivity fiber Bragg grating 3, a gain fiber, and a low-reflectivity fiber Bragg grating 5, wherein the gain fiber is an ytterbium-doped fiber 4; the high-reflectivity fiber Bragg grating 3, the gain fiber 4, and the low-reflectivity fiber Bragg grating 5 are connected in sequence to form an oscillation cavity, and the grating center wavelengths of the high-reflectivity fiber Bragg grating 3 and the low-reflectivity fiber Bragg grating 5 are 1018nm; the pump source module outputs pump light with an operating wavelength of 915nm, and the pump source module is connected to the high-reflectivity fiber Bragg grating 3 to couple the pump light into the oscillation cavity. The core of the ytterbium-doped fiber 4 is engraved with one or more chirped tilted gratings 4-1 with high loss to ASE in the 1030-1080nm band.

[0028] Reference Figure 1 The 1018nm fiber laser oscillator provided by one embodiment of the present invention adopts Figure 1The optical path structure schematic shown in FIG. 1 shows a pump source module comprising one or more semiconductor lasers 1 with a wavelength of 915 nm. The pigtail of the semiconductor laser 1 can be a multimode fiber or a passive double-clad fiber. Optionally, when the pump source module comprises N semiconductor lasers 1 and N is greater than or equal to 2, the pigtail of the semiconductor laser 1 is a multimode fiber. The output pigtails of the N semiconductor lasers 1 are fused to the N input arms of an N×1 pump combiner 2, respectively. The output arms of the N×1 pump combiner 2 are fused to a high-reflectivity fiber Bragg grating 3. The high-reflectivity fiber Bragg grating 3, the ytterbium-doped fiber 4, and the low-reflectivity fiber Bragg grating 5 are sequentially fused to form an oscillator cavity. The output end of the low-reflectivity fiber Bragg grating 5 is fused to a cladding light stripper 6 to output 1018 nm laser light. The fusion points between the above components form fusion points 7. Preferably, the ytterbium-doped fiber 4 is a double-clad ytterbium-doped fiber. The core of the ytterbium-doped optical fiber 4 is engraved with one or more chirped tilted gratings 4-1 with high ASE loss in the 1030-1080 nm band.

[0029] The present invention utilizes the relatively flat absorption spectrum of the ytterbium ions in the ytterbium-doped fiber 4 in the 915nm band to reduce the impact of LD wavelength drift caused by temperature changes on the stability of the laser output power. Furthermore, one or more chirped tilted gratings 4-1 with high ASE loss in the 1030-1080nm band are engraved in the core of the ytterbium-doped fiber 4. Figure 2 The chirped tilted grating 4-1 scatters ASE into the inner cladding of the ytterbium-doped fiber, allowing the 1018nm laser to continue transmitting through the CTFBG with low loss. Because the CTFBG reduces ASE loss, the 1018nm ytterbium-doped fiber oscillator's ytterbium fiber length requirement is significantly reduced, allowing a significant increase in fiber length to ensure sufficient absorption of the 915nm pump light.

[0030] In this way, the present invention can effectively suppress ASE in the 1030-1080 nm band, thereby significantly increasing the length of the ytterbium-doped fiber to compensate for the insufficient absorption of pump light caused by the small absorption coefficient of ytterbium ions in the 915 nm band, ensuring that the 1018 nm fiber laser oscillator pumped by the 915 nm LD can achieve high conversion efficiency.

[0031] Refer to Table 1, which shows the Figure 1 The 1018nm Yb-doped fiber laser oscillator with the optical path structure shown in the figure is Figure 1The following table compares the structural and performance differences of traditional 1018 nm fiber laser oscillators with the optical path structures shown. The gain fibers used are all double-clad ytterbium-doped fibers (core / cladding diameters of 15 / 130 μm, NA = 0.065 / 0.46, absorption coefficients of 2 dB / m@915 nm and 6 dB / m@976 nm). The reflectivity of the high-reflectivity fiber Bragg gratings is 99%, and the reflectivity of the low-reflectivity fiber Bragg gratings is 10%.

[0032] Table 1

[0033]

[0034] In summary, compared with the traditional 1018 nm fiber laser oscillator, the 1018 nm fiber laser oscillator provided by the present invention has the following advantages:

[0035] The chirped tilted grating written by femtosecond or ultraviolet writing technology on the ytterbium-doped optical fiber of the 1018nm optical fiber laser oscillator provided by the utility model has the advantages of low insertion loss and high power bearing capacity.

[0036] The 1018nm fiber laser oscillator provided by this utility model uses a 915nm LD pump. Compared to 976nm LD pumping, which significantly reduces the absorption coefficient of the ytterbium-doped fiber caused by wavelength drift due to ambient temperature, the 915nm pump effectively avoids the impact of wavelength drift caused by operating temperature changes on laser power and efficiency, enabling stable operation over a wider temperature range.

[0037] The 1018nm fiber laser oscillator provided by this utility model incorporates a chirped tilted grating written by femtoseconds in an ytterbium-doped fiber, effectively suppressing ASE in the 1030-1050nm band. Compared to existing 1018nm ytterbium-doped fiber laser oscillators pumped by a 915nm laser diode, the ytterbium-doped fiber provided by this utility model can significantly increase the length of the ytterbium-doped fiber to fully absorb the 915nm pump light, thereby achieving higher laser efficiency.

[0038] Matters not covered in this utility model are known technologies.

[0039] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0040] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. 1018nm fiber laser oscillator, characterized by: The invention comprises a pump source module, a high-reflectivity fiber Bragg grating (FBG), a gain fiber, and a low-reflectivity fiber Bragg grating (FBG), wherein the gain fiber is an ytterbium-doped fiber. The high-reflectivity fiber Bragg grating, the gain fiber, and the low-reflectivity fiber Bragg grating are sequentially connected to form an oscillation cavity. The grating center wavelengths of the high-reflectivity fiber Bragg grating and the low-reflectivity fiber Bragg grating are 1018 nm. The pump source module outputs pump light with an operating wavelength of 915 nm. The pump source module is connected to the high-reflectivity fiber Bragg grating to couple the pump light into the oscillation cavity. The core of the ytterbium-doped fiber is engraved with one or more chirped tilted gratings with high loss to ASE in the 1030-1080 nm band.

2. The 1018 nm fiber laser oscillator according to claim 1, characterized in that: The pump source module includes one or more semiconductor lasers with a wavelength of 915 nm.

3. The 1018 nm fiber laser oscillator according to claim 2, characterized in that: The pigtail of the semiconductor laser is a multimode optical fiber or a passive double-clad optical fiber.

4. The 1018 nm fiber laser oscillator according to claim 1, characterized in that: When the pump source module includes N semiconductor lasers and N is greater than or equal to 2, the pigtails of the semiconductor lasers are multimode optical fibers, the output pigtails of the N semiconductor lasers (1) correspond to the N input arms of the N×1 pump combiner, and the output arms of the N×1 pump combiner are fused to high-reflectivity fiber Bragg gratings.

5. The 1018 nm fiber laser oscillator according to any one of claims 1 to 4, characterized in that: The output end of the low-reflectivity optical fiber Bragg grating is fused with a cladding light stripper and then outputs a 1018 nm laser.

6. The 1018 nm fiber laser oscillator according to claim 5, characterized in that: The ytterbium-doped optical fiber is a double-clad ytterbium-doped optical fiber.

7. The 1018 nm fiber laser oscillator according to claim 6, characterized in that: The high-reflectivity fiber Bragg grating is inscribed in the core of a passive double-clad optical fiber, and the low-reflectivity fiber Bragg grating is inscribed in the core of a passive double-clad optical fiber. The model of the passive double-clad optical fiber for inscribed high-reflectivity fiber Bragg grating is the same as the model of the passive double-clad optical fiber for inscribed low-reflectivity fiber Bragg grating.

8. The 1018 nm fiber laser oscillator according to claim 7, characterized in that: The diameters and numerical apertures of the core and cladding of the double-clad ytterbium-doped optical fiber match those of the core and cladding of the passive double-clad optical fiber for writing high-reflectivity fiber gratings.

9. The 1018 nm fiber laser oscillator according to claim 6, 7 or 8, characterized in that: The core / cladding diameters of the double-clad ytterbium-doped fiber are 15 / 130 μm, NA=0.065 / 0.46, and the absorption coefficients are 2 dB / m@915 nm and 6 dB / m@976 nm.

10. The 1018 nm fiber laser oscillator according to claim 9, characterized in that: The length of the double-clad ytterbium-doped fiber is 10-15m.

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