Fiber laser

Abstract

The utility model provides an optical fiber laser, which comprises a single-mode neodymium-doped laser pumping source, a first wavelength division multiplexer, a high-reflectivity optical fiber grating, a passive silica optical fiber, a low-reflectivity optical fiber grating, a second wavelength division multiplexer and an optical fiber collimator, and is characterized in that the single-mode neodymium-doped laser pumping source is connected with a pumping end of the first wavelength division multiplexer; the common end of the first wavelength division multiplexer is connected with one end of the high-reflectivity fiber bragg grating, the other end of the high-reflectivity fiber bragg grating is connected with one end of the passive silica fiber, the other end of the passive silica fiber is connected with one end of the low-reflectivity fiber bragg grating, and the other end of the low-reflectivity fiber bragg grating is connected with the common end of the second wavelength division multiplexer. And the signal end of the second wavelength division multiplexer is connected with the optical fiber collimator. According to the 980nm band fiber laser, the excited Raman effect in the passive silica fiber is utilized, the pump light generated by the pump source is efficiently and nonlinearly shifted to the 980nm band, and 980nm band fiber laser output which is simple in structure, high in conversion efficiency and low in cost is obtained.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of optical fiber laser, especially to a kind of optical fiber laser capable of realizing 980nm waveband optical fiber laser output. BACKGROUND

[0002] 980nm waveband laser is commonly used laser source in industry, medical treatment, military and other fields.Compared with the waveband semiconductor laser, 980nm waveband optical fiber laser has significant advantages in beam quality, wavelength stability, temperature insensitivity and other aspects, and can be used as 1 micron waveband high-power optical fiber laser and other waveband optical fiber laser high-brightness pump source.In addition, 980nm waveband optical fiber laser can obtain new waveband laser output by combining nonlinear frequency conversion, wherein 490nm waveband laser generated by frequency doubling can replace argon ion laser as blue laser source, and has important application in blue light communication, semiconductor processing and other fields.It is the potential application in above fields that makes 980nm waveband optical fiber laser have high research value.

[0003] Emission spectrum of rare earth ytterbium (Yb) ion covers 980nm waveband, and Yb-doped optical fiber can directly generate this waveband laser oscillation, which is the common rare earth doped optical fiber for making 980nm waveband optical fiber laser.However, there are many challenges in obtaining 980nm waveband high-brightness high-efficiency laser output in Yb-doped optical fiber.The essence is determined by energy level of ytterbium ion.980nm waveband is three-level structure, and lower energy level of laser is ground state, which exists strong self-absorption effect, resulting in low laser conversion efficiency and high pump threshold.In addition, 980nm laser output in Yb-doped optical fiber competes with gain of four-level (1020~1100nm) ASE.To realize 980nm laser output, it is required that more than 50% of lower energy level particles of gain medium are inverted to upper energy level, while only about 5% is required for ASE generation.Therefore, it is necessary to improve pumping absorption of gain medium and increase inverted particle number to suppress ASE self-oscillation.

[0004] To solve the above problems, the main technical scheme for realizing 980 nm band Yb-doped fiber laser at present is to use Yb-doped fiber with special structure, such as large core-cladding ratio, photonic bandgap fiber, photonic crystal fiber, air hole outer cladding fiber, tapered fiber, etc. The patent number "ZL201710102903.4" "All-fiber structure 980 nm band high power fiber oscillator" increases the core-cladding ratio of Yb-doped double-clad fiber to obtain kilowatt-level 980 nm band laser. In the literature "Optics Express, 27(18), 24972, 2019", a hundred-watt high-brightness 980 nm laser is realized by using photonic bandgap fiber design. Although the Yb-doped fiber with structural design can improve the performance of 980 nm band laser, it also introduces some new problems. First, the design and preparation of special structure fibers such as large core-cladding ratio and photonic bandgap fiber are complex and difficult to produce; second, it is difficult to develop matching passive fiber devices (such as fiber gratings, mode field adaptors, etc.), which need to be highly customized. The above problems make it difficult to promote and apply 980 nm laser based on special structure Yb-doped fiber.

[0005] In addition to fiber structure design, optimizing the performance of 980 nm band Yb-doped fiber laser from the aspect of laser technology is also a common solution. The patent number ZL201310749840.3 "980 nm band all-fiber structure composite cavity single-mode fiber laser" proposes a composite cavity scheme for 980 nm band fiber laser. This scheme expands the number of semiconductor laser direct pumping oscillator modules to improve the output efficiency of the entire laser system, thereby realizing power expansion while ensuring the efficiency of electro-optical conversion, but the optical structure of this scheme is still complex. In the literature "Optics Express, 31(6), 10019, 2023", the amplification efficiency of 972 nm laser is improved by heating the Yb-doped fiber to 300℃, achieving 10W-level high-brightness 972 nm laser output. However, heating the fiber, especially heating the fiber above 100℃, can severely damage the fiber coating and degrade the long-term working stability of the laser, so it does not have practical application value.

[0006] In summary, the current 980 nm band fiber laser based on Yb-doped fiber has the technical disadvantages of difficult production, complex structure, and low conversion efficiency. It is of great significance to construct a simple and efficient 980 nm fiber laser. Practical new type content

[0007] In view of the above technical problems, the utility model provides a simple structure, conversion efficiency high, low cost's fiber laser, this laser utilizes the stimulated Raman effect in passive quartz optical fiber, and high efficiency nonlinear frequency shift of doped neodymium fiber laser is to 980nm wave band, realizes 980nm wave band fiber laser output.

[0008] The utility model discloses a kind of fiber lasers, including single-mode doped neodymium laser pump source, first wave division multiplexer, high reflection fiber grating, passive quartz optical fiber, low reflection fiber grating, second wave division multiplexer and fiber collimator, single-mode doped neodymium laser pump source is connected with the pump end of first wave division multiplexer, the common end of first wave division multiplexer is connected with one end of high reflection fiber grating, another end of high reflection fiber grating is connected with one end of passive quartz optical fiber, another end of passive quartz optical fiber is connected with one end of low reflection fiber grating, another end of low reflection fiber grating is connected with the common end of second wave division multiplexer, the signal end of second wave division multiplexer is connected with fiber collimator.

[0009] Preferably, the single-mode doped neodymium laser pump source is a single-mode doped neodymium fiber laser, and the center wavelength of the single-mode doped neodymium laser pump source is located in the 919-940 nm wave band.

[0010] Preferably, the passive quartz optical fiber is a single-clad quartz optical fiber.

[0011] Preferably, the core diameter of the passive quartz optical fiber is not greater than 20 μm.

[0012] Preferably, the length of the passive quartz optical fiber is not less than 20 m.

[0013] Preferably, the center wavelength of the high reflection fiber grating is located in the 960-983 nm wave band, and the reflectivity at the center wavelength is not less than 95%. Further, the center wavelength of the low reflection fiber grating is the same as that of the high reflection fiber grating, and the reflectivity of the low reflection fiber grating at the center wavelength is 10-50%. Still further, the 3dB reflection bandwidth of the high reflection fiber grating is not greater than 2 nm, and the 3dB reflection bandwidth of the low reflection fiber grating is 0.04-1 nm.

[0014] Preferably, the cutting angle of the signal end of the first wave division multiplexer and the pump end of the second wave division multiplexer is 5-20°.

[0015] Compared with the prior art, the optical fiber laser of the utility model, through setting the pump source as single mode neodymium doped laser pump source, setting the gain medium as passive quartz optical fiber, using the stimulated Raman effect of passive quartz optical fiber, obtaining high efficiency 980nm waveband optical fiber laser through nonlinear frequency shift means, breaking through the limitation of 980nm waveband Yb doped fiber laser in conversion efficiency, cost, structure and the like, finally realizing simple structure, low cost, high conversion efficiency 980nm waveband laser output. The optical fiber laser in the utility model has high quantum efficiency and low heat consumption, and since the Raman gain in the optical fiber is proportional to the pump light intensity and has no saturation effect, therefore the 980nm waveband output power in the utility model can be linearly improved with the pump power. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the specific embodiment of the utility model or the technical scheme in the prior art, the drawings needed to be used in the specific embodiment or the prior art description will be briefly introduced as follows, and obviously, the drawings in the following description are some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creating labor.

[0017] Figure 1 It is a structural schematic view of the optical fiber laser of an embodiment of the utility model.

[0018] Figure 2 It is an output power growth curve schematic view of the optical fiber laser of an embodiment of the utility model with the pump power.

[0019] Figure 3 It is an output power growth curve schematic view of the optical fiber laser of another embodiment of the utility model with the pump power.

[0020] Figure 4 It is an output power growth curve schematic view of the optical fiber laser of another embodiment of the utility model with the pump power.

[0021] The drawings are as follows: 1-single mode neodymium doped laser pump source; 2-first wave division multiplexer; 3-high reflection fiber grating; 4-passive quartz optical fiber; 5-low reflection fiber grating; 6-second wave division multiplexer; 7-optical fiber collimator. DETAILED DESCRIPTION

[0022] In order to further understand the purpose, structure, features and functions of the utility model, the embodiments are described in detail as follows.

[0023] In the description of the utility model, it is necessary to explain, the term '' center '' '' upper '' '' lower '' '' left '' '' right '' '' vertical '' '' horizontal '' '' internal '' '' external '' etc. Indicate the orientation or positional relation of the drawing shown is based on the orientation or positional relation, only is for the convenience of describing the utility model and simplifying the description, and is not indicate or imply the device or element must have a particular orientation, with a particular orientation structure and operation, therefore can not be understood as the restriction of the utility model.

[0024] Please see Figure 1 The utility model discloses a kind of fiber lasers, including single-mode neodymium-doped laser pumping source 1, first wave division multiplexer 2, high reflection fiber grating 3, passive quartz optical fiber 4, low reflection fiber grating 5, second wave division multiplexer 6 and fiber collimator 7, single-mode neodymium-doped laser pumping source 1 is connected with the pump end of first wave division multiplexer 2, the common end of first wave division multiplexer 2 is connected with one end of high reflection fiber grating 3, the other end of high reflection fiber grating 3 is connected with one end of passive quartz optical fiber 4, the other end of passive quartz optical fiber 4 is connected with one end of low reflection fiber grating 5, the other end of low reflection fiber grating 5 is connected with the common end of second wave division multiplexer 6, the signal end of second wave division multiplexer 6 is connected with fiber collimator 7.

[0025] Pump light generated by single-mode neodymium-doped laser pumping source 1 is coupled into the core of passive quartz optical fiber 4 by first wave division multiplexer 2 to excite stimulated Raman effect, high reflection fiber grating 3, passive quartz optical fiber 4 and low reflection fiber grating 5 jointly constitute Raman resonant cavity, and the 980nm waveband laser generated is separated from residual pump light by second wave division multiplexer 6, and finally is output by fiber collimator 7.

[0026] Preferably, single-mode neodymium-doped laser pumping source 1 is a single-mode neodymium-doped fiber laser, and the center wavelength of single-mode neodymium-doped laser pumping source 1 is located in the 919nm-940nm waveband.

[0027] Preferably, passive quartz optical fiber 4 is a single-clad quartz optical fiber.

[0028] Preferably, the core diameter of passive quartz optical fiber 4 is not greater than 20μm.

[0029] Preferably, the length of passive quartz optical fiber 4 is not less than 20m.

[0030] Preferably, the center wavelength of high reflection fiber grating 3 is located in the 960nm-983nm waveband, and the reflectivity at the center wavelength is not less than 95%. Further, the center wavelength of low reflection fiber grating 5 is the same as that of high reflection fiber grating 3, and the reflectivity of low reflection fiber grating 5 at the center wavelength is 10%-50%. Still further, the 3dB reflection bandwidth of high reflection fiber grating 3 is not greater than 2nm, and the 3dB reflection bandwidth of low reflection fiber grating 5 is 0.04nm-1nm.

[0031] Preferably, the cutting angle of the signal end of the first wavelength division multiplexer 2 and the pump end of the second wavelength division multiplexer 6 is 5° to 20°.

[0032] In actual use, the core composition of the passive quartz optical fiber 4 does not contain any rare earth ions; the devices are connected through fusion, specifically, the single-mode neodymium-doped laser pump source 1 and the first wavelength division multiplexer 2, the first wavelength division multiplexer 2 and the high-reflection fiber grating 3, the high-reflection fiber grating 3 and the passive quartz optical fiber 4, the passive quartz optical fiber 4 and the low-reflection fiber grating 5, the low-reflection fiber grating 5 and the second wavelength division multiplexer 6, and the second wavelength division multiplexer 6 and the fiber collimator 7 are connected through fusion, thereby forming a full-fiber structure.

[0033] The fiber laser of the embodiment of the utility model, the center wavelength of single-mode neodymium-doped laser pump source 1 is 919nm;The center wavelength of high-reflection fiber grating 3 is 960nm, the reflectivity of high-reflection fiber grating 3 at the center wavelength is 95%, and the 3dB reflection bandwidth of high-reflection fiber grating 3 is 2nm;The center wavelength of low-reflection fiber grating 5 is 960nm, the reflectivity of low-reflection fiber grating 5 at the center wavelength is 10%, and the 3dB reflection bandwidth of low-reflection fiber grating 5 is 0.5nm;Passive quartz optical fiber 4 is passive Hi780 quartz optical fiber, the fiber core diameter is 4μm, and the length is 100m;The cutting angle of the signal end of the first wavelength division multiplexer 2 and the pump end of the second wavelength division multiplexer 6 is 20°.

[0034] Please see Figure 2 , Figure 2 It is the output power of the fiber laser of the embodiment with the growth curve of pump power, and 50W 960nm laser output is realized under the condition that the 919nm pump power is 80W, and the conversion efficiency is 68%.

[0035] The fiber laser of another embodiment of the utility model, the center wavelength of single-mode neodymium-doped laser pump source 1 is 940nm;The center wavelength of high-reflection fiber grating 3 is 983nm, the reflectivity of high-reflection fiber grating 3 at the center wavelength is 99%, and the 3dB reflection bandwidth of high-reflection fiber grating 3 is 1.5nm;The center wavelength of low-reflection fiber grating 5 is 983nm, the reflectivity of low-reflection fiber grating 5 at the center wavelength is 20%, and the 3dB reflection bandwidth of low-reflection fiber grating 5 is 1nm;Passive quartz optical fiber 4 is passive PM80 quartz optical fiber, the fiber core diameter is 7μm, and the length is 20m;The cutting angle of the signal end of the first wavelength division multiplexer 2 and the pump end of the second wavelength division multiplexer 6 is 8°.

[0036] Please see Figure 3 , Figure 3The output power of the fiber laser of the embodiment increases with the growth curve of the pump power, and 70W of 983nm laser output is achieved under the condition that the 940nm pump power is 100W, and the conversion efficiency is 78%.

[0037] The center wavelength of the single-mode neodymium-doped laser pump source 1 is 930nm; the center wavelength of the high-reflection fiber grating 3 is 972nm, the reflectivity of the high-reflection fiber grating 3 at the center wavelength is 98%, and the 3dB reflection bandwidth of the high-reflection fiber grating 3 is 1nm; the center wavelength of the low-reflection fiber grating 5 is 972nm, the reflectivity of the low-reflection fiber grating 5 at the center wavelength is 50%, and the 3dB reflection bandwidth of the low-reflection fiber grating 5 is 0.04nm; the passive quartz optical fiber 4 is a 20 / 125 single-clad quartz optical fiber, the fiber core diameter is 20μm, and the length is 50m; and the cutting angle of the signal end of the first wavelength division multiplexer 2 and the pump end of the second wavelength division multiplexer 6 is 5°.

[0038] Please refer to Figure 4 , Figure 4 The output power of the fiber laser of the embodiment increases with the growth curve of the pump power, and 70W of 983nm laser output is achieved under the condition that the 940nm pump power is 100W, and the conversion efficiency is 78%.

[0039] The fiber laser of the utility model, through setting pump source as single-mode neodymium-doped laser pump source, setting gain medium as passive quartz optical fiber, utilizing the stimulated Raman effect of passive quartz optical fiber, obtaining high-efficiency 980nm waveband fiber laser through nonlinear frequency shift means, breaking through the limitation of 980nm waveband Yb-doped fiber laser in conversion efficiency, cost, structure and the like, finally realizing simple structure, low cost, high conversion efficiency 980nm waveband laser output. The fiber laser in the utility model has high quantum efficiency and small heat consumption, and since the Raman gain in the optical fiber is proportional to the pump light intensity, there is no saturation effect, so the 980nm waveband output power in the utility model can be linearly improved with the pump power.

[0040] The utility model has been described by the above related embodiments, however the above embodiment is only for the example of implementing the utility model. In addition, the technical features involved in the different embodiments of the utility model described above can be combined with each other as long as there is no conflict between them. It must be pointed out that the disclosed embodiments do not limit the scope of the utility model. On the contrary, changes and modifications made without departing from the spirit and scope of the utility model are within the scope of the patent protection of the utility model.

Claims

1. A fiber laser, characterized by, The device comprises a single-mode neodymium-doped laser pumping source, a first wavelength division multiplexer, a high-reflection fiber grating, a passive quartz optical fiber, a low-reflection fiber grating, a second wavelength division multiplexer and a fiber collimator, the single-mode neodymium-doped laser pumping source is connected with a pumping end of the first wavelength division multiplexer, a common end of the first wavelength division multiplexer is connected with one end of the high-reflection fiber grating, the other end of the high-reflection fiber grating is connected with one end of the passive quartz optical fiber, the other end of the passive quartz optical fiber is connected with one end of the low-reflection fiber grating, the other end of the low-reflection fiber grating is connected with a common end of the second wavelength division multiplexer, and a signal end of the second wavelength division multiplexer is connected with the fiber collimator; wherein the center wavelength of the single-mode neodymium-doped laser pumping source is located in a 919nm-940nm wave band; the passive quartz optical fiber is a single-clad quartz optical fiber, the core diameter of the passive quartz optical fiber is not more than 20μm, and the length of the passive quartz optical fiber is not less than 20m; the center wavelength of the high-reflection fiber grating is located in a 960nm-983nm wave band, the reflectivity of the high-reflection fiber grating at the center wavelength is not less than 95%, and the 3dB reflection bandwidth of the high-reflection fiber grating is not more than 2nm; the center wavelength of the low-reflection fiber grating is the same as that of the high-reflection fiber grating, the reflectivity of the low-reflection fiber grating at the center wavelength is 10%-50%, and the 3dB reflection bandwidth of the low-reflection fiber grating is 0.04nm-1nm.

2. The fiber laser of claim 1, wherein, The single-mode neodymium-doped laser pumping source is a single-mode neodymium-doped fiber laser.

3. The fiber laser of claim 1, wherein, The cutting angle of the signal end of the first wavelength division multiplexer and the pumping end of the second wavelength division multiplexer is 5°-20°.

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