Preparation Method and Application of a Saturable Absorber Based on Carbon Nanonion Particles

Abstract

The present invention provides a method for preparing a saturable absorber based on carbon nano-onion particles, comprising: preparing carbon nano-onion particles; mixing the carbon nano-onion particles, a film-forming agent and deionized water in proportion to form a mixed solution; after ultrasonic dispersion of the mixed solution, preparing a saturable absorber based on carbon nano-onions. In the mixed solution, the mass fraction of carbon nano-onion particles is 0.2 parts to 1.63 parts, the mass fraction of deionized water is 30 to 50 parts, and the mass fraction of the film-forming agent is 8 to 25 parts. The saturable absorber prepared by mixing carbon nano-onion nanoparticles and a film-forming agent in the present invention has good light transmittance, exhibits an obvious saturable absorption effect, is simple to prepare, has good stability, greatly improves the interaction between light and materials, and enhances the damage threshold of the saturable absorber. The present invention also provides a saturable absorber and its application in a fiber laser.

Description

Technical Field

[0001] The present invention relates to the field of pulsed laser technology, and particularly relates to a saturable absorber based on carbon nano-onions, a preparation method thereof, and an application thereof. Background Art

[0002] Pulsed fiber lasers exhibit significant advantages of narrow pulse width and high peak power, which enable them to have a wide range of applications such as material processing, fiber sensing, medical surgery, and free space communication. Passive Q-switching and mode-locking are the main means to achieve pulsed fiber lasers. As a nonlinear optical modulator in the laser cavity, a saturable absorber is the key to realizing pulsed laser technology. Existing saturable absorbers have many limitations. Exploring new mechanisms, new materials, and developing a new generation of ultrafast lasers are currently hot research topics. Nonlinear polarization rotation, as an artificial saturable absorber, realizes mode-locking by using the combination of a polarizer in the laser cavity and the nonlinear birefringence of the optical fiber. It has a rapid response and a high damage threshold. However, the structure of nonlinear polarization rotation is relatively complex, its state is easily affected by temperature, and higher requirements are imposed on the cavity structure, which greatly limits the application of saturable absorbers based on nonlinear polarization rotation in ultrafast lasers.

[0003] Therefore, it is of great significance to explore new high-performance saturable absorbers, such as those with simple preparation processes, low costs, flexible parameter regulation, especially saturable absorbers with a relatively wide nonlinear absorption bandwidth, which can achieve multi-band pulsed laser output. Summary of the Invention

[0004] The present invention provides a preparation method of a saturable absorber based on carbon nano-onions. The saturable absorber prepared by mixing carbon nano-onion nanoparticles and a film-forming agent has good light transmittance, exhibits an obvious saturable absorption effect, is simple to prepare, has good stability, greatly improves the interaction between light and the material, and enhances the damage threshold of the saturable absorber.

[0005] The technical solution provided by the present invention is as follows:

[0006] A preparation method of a saturable absorber based on carbon nano-onion particles, comprising:

[0007] Preparing carbon nano-onion particles;

[0008] Mixing the carbon nano-onion particles, a film-forming agent, and deionized water in proportion to form a mixed solution;

[0009] After ultrasonic dispersion of the mixed solution, a saturable absorber based on carbon nano-onions is prepared.

[0010] Preferably, the mass fraction of carbon nano-onion particles in the mixed solution is 0.2 to 1.63 parts, the mass fraction of deionized water is 30 to 50 parts, and the mass fraction of the film-forming agent is 8 to 25 parts.

[0011] Preferably, after the mixed solution is ultrasonically dispersed, it is applied on the glass surface or deposited on the surface of a tapered optical fiber, a D-shaped optical fiber or a clad-etched optical fiber, or filled in the air holes of a photonic crystal, and a saturable absorber based on carbon nano-onions is obtained after drying.

[0012] Preferably, the film-forming agent is one or more of sodium carboxymethyl cellulose, polyvinyl alcohol, polymethyl methacrylate or polydimethylsiloxane.

[0013] Preferably, the preparation of the carbon nano-onion particles includes:

[0014] Sprinkle the mixed powder of Ni-Fe / Al2O3 and NiO-Fe2O3 into an incubator, and set the temperature of the incubator to the first reaction temperature; wherein, the mass fraction of Ni-Fe / Al2O3 is 0.2 to 1.63 parts, and the mass fraction of NiO-Fe2O3 is 30 to 50 parts;

[0015] Fill hydrogen into the incubator to reduce the mixed powder, and cool it to room temperature under a nitrogen atmosphere to obtain Ni-Fe powder. Among them, the charging flow rate of the hydrogen is 100 mL / min, and the charging time is 1 h;

[0016] Heat the incubator to the second reaction temperature, and fill it with methane, nitrogen and hydrogen. After constant temperature treatment, carbon nano-onion precipitates are grown by chemical vapor deposition;

[0017] Insulate the incubator and cool it to room temperature under a nitrogen atmosphere, and synthesize the carbon nano-onion precipitates into carbon nano-onion particles.

[0018] Preferably, the first reaction temperature is set to 450°C - 500°C.

[0019] Preferably, the second reaction temperature is 750°C - 950°C, and the heating rate to the second reaction temperature is 10°C / minute.

[0020] Preferably, the cooling rate of the incubator is 5°C / min.

[0021] A saturable absorber based on carbon nano-onions, such as a saturable absorber prepared by the preparation method of the saturable absorber based on carbon nano-onions.

[0022] A preparation method and application of a saturable absorber based on carbon nano-onion particles.

[0023] Beneficial effects

[0024] 1. The present invention provides a method for preparing a saturable absorber based on carbon nano-onions. The saturable absorber prepared by mixing carbon nano-onion nanoparticles with a film-forming agent has good light transmittance, exhibits an obvious saturable absorption effect, and is simple to prepare and has good stability.

[0025] 2. For the fiber laser provided by the present invention, the saturable absorber prepared by mixing carbon nano-onion nanoparticles with a film-forming agent has good laser operation output, stable pulse sequence data, and good repeatability. Description of the drawings

[0026] Figure 1 It is a flowchart of the method for preparing a saturable absorber based on carbon nano-onion particles according to the present invention.

[0027] Figure 2 It is a schematic structural diagram of the fiber laser according to the present invention.

[0028] Figure 3 It is a scanning electron microscope photograph of the carbon nano-onion saturable absorber according to the present invention.

[0029] Figure 4 It is a high-magnification transmission electron microscope photograph of the carbon nano-onion saturable absorber according to the present invention.

[0030] Figure 5 It is an absorption spectrum diagram of the carbon nano-onion saturable absorber according to the present invention.

[0031] Figure 6 It is the output spectrum of the saturable absorber film prepared by mixing carbon nano-onions and sodium carboxymethylcellulose in a Q-switched laser at 1.56 μm according to the present invention.

[0032] Figure 7 It is the pulse sequence data of the saturable absorber film prepared by mixing carbon nano-onions and sodium carboxymethylcellulose in a Q-switched laser at 1.56 μm according to the present invention.

[0033] Figure 8 It is a trend diagram of the Q-switched laser pulse repetition frequency and pulse width varying with the pump power according to the present invention.

[0034] Figure 9 It is the output spectrum of the saturable absorber with carbon nano-onions coated on a D-type fiber in a mode-locked laser at a central wavelength of 1562 nm according to the present invention.

[0035] Figure 10The saturable absorber of carbon nano-onion coated D-type fiber according to the present invention is used for pulse sequence data in a mode-locked laser with a central wavelength of 1562 nm.

[0036] Figure 11 The saturable absorber of carbon nano-onion coated D-type fiber according to the present invention is used for the output spectrum in a mode-locked laser with a central wavelength of 1932 nm.

[0037] Figure 12 The saturable absorber of carbon nano-onion coated D-type fiber according to the present invention is used for pulse sequence data in a mode-locked laser with a central wavelength of 1932 nm. Detailed implementation manners

[0038] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "inside", "above", "below", "horizontal", "inside", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description, rather than indicating or implying that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0040] In addition, it should be further noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0041] As Figure 1 shown, based on the technical problems proposed in the background art, the present invention provides a preparation method based on a carbon nano-onion saturable absorber, including the following steps:

[0042] Step S110, preparing carbon nano-onion particles;

[0043] Step S120: Mix carbon nano-onion particles, film-forming agent and deionized water in proportion to make a mixed solution;

[0044] Step S130: After ultrasonic dispersion of the mixed solution obtained in Step S120, a saturable absorber based on carbon nano-onions is prepared.

[0045] Among them, the mass fraction of carbon nano-onion particles in the mixed solution is 0.2 to 1.63 parts, the mass fraction of deionized water is 30 to 50 parts, and the mass fraction of the film-forming agent is 8 to 25 parts.

[0046] As a preference, in Step S130, the preparation process of the saturable absorber of carbon nano-onions can be achieved by ultrasonic dispersing the mixed solution obtained in Step S120, then smearing it on the glass surface or depositing it on the surface of a tapered fiber, D-type fiber or etched cladding fiber, or filling it into the air holes of a photonic crystal, and after drying, a saturable absorber based on carbon nano-onions is obtained.

[0047] As a preference, the film-forming agent is one or several of sodium carboxymethyl cellulose, polyvinyl alcohol, polymethyl methacrylate or polydimethylsiloxane.

[0048] In a preferred embodiment, the preparation of the carbon nano-onion particles includes:

[0049] Evenly sprinkle Ni-Fe / Al2O3 and NiO-Fe2O3 powders into an incubator, and under the protection of nitrogen, heat up at a rate of 10 °C / min to raise the temperature of the incubator from room temperature to 450 °C - 500 °C; among them, the mass fraction of Ni-Fe / Al2O3 is 0.2 to 1.63 parts, and the mass fraction of NiO-Fe2O3 is 30 to 50 parts.

[0050] Charge hydrogen into the incubator at a flow rate of 100 mL / min for reduction. After 1 h, then cool it to room temperature under a nitrogen atmosphere to obtain Ni-Fe powder;

[0051] The incubator is heated from room temperature to 750 °C - 950 °C at a speed of 10 °C / min. Using methane as the carbon source gas and nitrogen and hydrogen as the carrier reaction gases, keep it at a constant temperature for 1 h, and grow carbon nano-onion particles by chemical vapor deposition;

[0052] After adiabatic, the reaction product is cooled to room temperature at a cooling rate of 5 °C / min under a nitrogen atmosphere to obtain carbon nano-onion particles;

[0053] Mix carbon nano-onion particles, film-forming agent and deionized water in proportion to make a mixed solution;

[0054] Specific film-forming agents are mixed at a molar ratio of 8-25:1 of the film-forming agent to deionized water and stirred evenly until the solution becomes colorless and transparent. Specifically, the film-forming agent is one or more of sodium carboxymethyl cellulose, polyvinyl alcohol, polymethyl methacrylate, or polydimethylsiloxane.

[0055] After ultrasonic dispersion of the mixed solution, it is coated on the surface of glass or deposited on the surface of a tapered optical fiber, a D-shaped optical fiber, or a cladding-etched optical fiber, or filled into the air holes of a photonic crystal. After drying, a saturable absorber based on carbon nano-onions is obtained.

[0056] Specifically, in this embodiment, a film is made by mixing carbon nano-onion nanoparticles with sodium carboxymethyl cellulose, or polyvinyl alcohol, or polymethyl methacrylate, or polydimethylsiloxane and used as a saturable absorber. It has good light transmittance, shows an obvious saturable absorption effect, and has a simple preparation process and good stability, greatly improving the interaction between light and the material and enhancing the damage threshold of the saturable absorber.

[0057] As Figure 2 shown, the present invention also provides a fiber laser, including: a pump light source 110, a coupling device 120, a gain medium 130, a polarization-independent fiber isolator 140, a fiber connection device 150; a polarization controller 160, an optical splitter 170, and a pulsed light output end 180.

[0058] Among them, the pump light source 110 is a 980nm semiconductor laser or a 1570nm fiber laser, and the gain medium 130 is a ytterbium / erbium / thulium-doped silica fiber; the coupling device 120 is arranged between the pump light source 110 and the gain medium 130 and can couple the pump light emitted by the pump light source 110 into the gain medium 130 to form excited-state particles.

[0059] As a preference, 140 is a polarization-independent fiber isolator, and its operating wavelength is 1060nm / 1550nm / 1980nm, which can ensure the unidirectional operation of the laser in the laser cavity.

[0060] The fiber connection device 150 is a fiber connector for placing a carbon nano-onion saturable absorber; the polarization controller 160 is used to adjust the polarization state in the cavity.

[0061] The optical splitter 170 can obtain the pulsed laser and can feedback 90% of the pulsed laser back into the laser cavity for operation, and 10% is used as the output laser. Specifically, 10% of the output pulses are output through the optical output end 180.

[0062] Preferably, the pump light source is a 980 nm semiconductor laser or a 1570 nm fiber laser; the coupling device is a wavelength division multiplexer, and the coupling wavelengths of the wavelength division multiplexer are 980 / 1060 nm or 980 / 1550 nm or 1570 / 1980 nm; the operating wavelengths of the optical splitter are 1060 nm or 1550 nm or 1980 nm.

[0063] The carbon nano-onion saturable absorber is used in a laser, and the output characteristics of the laser are detected to verify the stability of the saturable absorber.

[0064] Experimental Example 1: A saturable absorber prepared by mixing carbon nano-onion nanoparticles and sodium carboxymethylcellulose is used for Q-switching laser output at 1.56 μm;

[0065] 1. Sample preparation process

[0066] The Ni-Fe / Al2O3 and NiO-Fe2O3 powders are evenly sprinkled into an oven. Under the protection of nitrogen, the temperature is increased at a rate of 10 °C / min, so that the oven temperature rises from room temperature to 450 °C - 500 °C; hydrogen is flushed into the oven at a flow rate of 100 mL / min for reduction. After 1 h, it is then cooled to room temperature under a nitrogen atmosphere to obtain Ni-Fe powder; under the protection of nitrogen, the oven is heated from room temperature to between 750 °C - 950 °C at a speed of 10 °C / min. Methane is used as the carbon source gas, and nitrogen and hydrogen are used as the carrier reaction gases. The reaction is carried out at a constant temperature for 1 h, and carbon nano-onion particles are grown by chemical vapor deposition; after adiabatic treatment, the reaction product is cooled to room temperature at a cooling rate of 5 °C / min under a nitrogen atmosphere to obtain carbon nano-onion particles;

[0067] The deionized aqueous solution of sodium carboxymethylcellulose (NaCMC) is prepared by mixing sodium carboxymethylcellulose powder and deionized water in a molar ratio of 8 - 25:1 and stirring evenly until the solution becomes colorless and transparent. The synthesized carbon nano-onion nanoparticles are mixed with the deionized aqueous solution of sodium carboxymethylcellulose in a molar ratio of 1:1 - 64, and after ultrasonic dispersion for 2 - 5 h, the mixed solution is spin-coated on the surface of a flat glass slide and naturally dried in a vacuum-sealed container until a film is formed. This layer of film is the prepared saturable absorber.

[0068] Perform fiber laser tests, such as Figure 3As shown, it is a ring cavity fiber laser operating at the 1.56 μm band. Among them, 110 is a 980 nm semiconductor laser, serving as the pump light source. 120 is a 980 nm / 1560 nm wavelength division multiplexer. 130 is a 20 cm long erbium-doped silica fiber, serving as the gain medium for laser generation. 140 is a 1560 nm polarization-independent fiber isolator, which is used to ensure the unidirectional operation of the laser in the laser cavity. 150 is a fiber connection device. Specifically, a saturable absorber is placed on the surface of the fiber joint. 160 is a polarization controller, which is used to regulate the polarization state of the laser cavity. 170 is a 1560 nm 10 dB optical splitter, which is used to split and export the generated pulsed light. 180 is the pulsed light output end, which is respectively connected to a spectrometer and an oscilloscope for spectral and pulse testing. All the components in the entire experimental setup are connected using single-mode fiber SMF-28 at the in-cavity joints and then welded using a fiber welding machine. The pump source is the 980 nm semiconductor laser 110. The pump light is guided into the cavity through the wavelength division multiplexing device 120 operating at 980 / 1560 nm. The 20 cm long erbium-doped gain fiber 130 is inserted into the cavity as the gain medium. The isolator 140 mainly ensures the unidirectional transmission of light. The carbon nanotube onion film is placed in the 150 fiber ferrule. The polarization state of the cavity is adjusted through the polarization controller 160. The output laser passes through a 10 dB optical coupler 170 to output 10% of the light to the 180 OSA spectrometer or oscilloscope to observe the pulse shape or pulse train.

[0069] The experimental results are as Figures 6 - 8 shown: The central wavelength of the Q-switched laser spectrum is 1559 nm. The repetition rate of the pulses increases with the increase of the pump power. At the same time, the pulse width decreases with the increase of the pump power, which is a typical characteristic of the Q-switched pulsed laser output.

[0070] Example 2: A saturable absorber of carbon nanotube onion-coated D-type fiber and its application to mode-locked laser output at the 1.56 μm band;

[0071] 1. Sample preparation process

[0072] The Ni-Fe / Al2O3 and NiO-Fe2O3 powders are uniformly sprinkled into a thermostat, and the temperature is raised at a rate of 10°C / min under the protection of nitrogen, so that the thermostat rises from room temperature to 450°C-500°C; hydrogen is injected into the thermostat at a flow rate of 100mL / min for reduction, and after 1 hour, it is cooled to room temperature in a nitrogen atmosphere to obtain Ni-Fe powder; under the protection of nitrogen, the thermostat is heated at a rate of 10°C / min from room temperature to between 750°C-950°C, with methane as the carbon source gas, nitrogen and hydrogen as the carrier gas reaction gas, and the temperature is kept constant for 1 hour, and carbon nano-onion particles are grown by chemical vapor deposition; after insulation, the reaction product is cooled to room temperature at a cooling rate of 5°C / min in a nitrogen atmosphere to obtain carbon nano-onion particles;

[0073] The obtained carbon nano onion nanoparticles are mixed with deionized water in a volume ratio of 1:4 to 10, and ultrasonic dispersion is performed for 6 hours. The mixed solution after ultrasonic dispersion is coated on the surface of a D-type optical fiber, and naturally dried in a vacuum-sealed container. The water evaporates, and the carbon nano onion nanoparticles covering the surface of the D-type optical fiber are saturable absorbers.

[0074] 2. Perform fiber laser testing, such as Figure 2 As shown in the figure, it is a ring cavity fiber laser operating at 1.56μm band, wherein 110 is a 980nm semiconductor laser, which is used as a pumping light source, 120 is a 980nm / 1560nm wavelength division multiplexer, 130 is a 20cm long erbium-doped quartz fiber, which is used as a gain medium for laser generation, 140 is a 1560nm polarization-independent fiber isolator, in order to ensure the unidirectional operation of the laser in the laser cavity, 150 is a fiber connection device, specifically a saturable absorber placed on the surface of the fiber connector, 160 is a polarization controller, which is used to adjust the polarization state of the laser cavity, 170 is a 1560nm 10dB optical splitter, which is used to branch and export the generated pulse light, and 180 is a pulse light output end, which is connected to a spectrometer and an oscilloscope respectively to test the spectrum and pulse; the joints in the cavity of each component in the whole experimental device are connected with single-mode optical fiber SMF-28, and then welded by an optical fiber welding machine. The pump source is a 980nm semiconductor laser 110. The pump light is guided into the cavity through a wavelength division multiplexing device 120 operating at 980 / 1560nm. An erbium-doped gain fiber 130 with a length of 20cm is inserted into the cavity as a gain medium. The isolator 140 is mainly used to ensure the unidirectional transmission of light. The D-type optical fiber 150 coated with carbon nano-onion nanoparticles is connected to the laser. The polarization state of the cavity is adjusted by a polarization controller 160. The output laser outputs 10% of the light through a 10dB optical coupler 170 to an OSA spectrometer or oscilloscope to form a pulse shape or pulse sequence. Gradually increase the pump power of the laser 110, adjust the polarization of the fiber laser, and achieve mode-locked pulse laser output,

[0075] The experimental results are as Figures 9 - 10 follows: The central wavelength of the mode-locked laser spectrum is 1562 nm, the interval between adjacent pulse trains is 52 ns, and the repetition frequency is 19.2 MHz.

[0076] Example 3: A saturable absorber of carbon nano-onions coated on a D-shaped fiber and used for mode-locked laser output at the 2-μm band;

[0077] 1. Sample preparation process

[0078] The Ni-Fe / Al2O3 and NiO-Fe2O3 powders are evenly sprinkled into an oven. Under the protection of nitrogen, the temperature is raised at a rate of 10 °C / min, so that the temperature of the oven rises from room temperature to 450 °C - 500 °C; hydrogen is flushed into the oven at a flow rate of 100 mL / min for reduction. After 1 h, it is then cooled to room temperature under a nitrogen atmosphere to obtain Ni-Fe powder; under the protection of nitrogen, the oven is heated from room temperature to between 750 °C - 950 °C at a speed of 10 °C / min. Using methane as the carbon source gas and nitrogen and hydrogen as the carrier reaction gases, it is kept at a constant temperature for 1 h, and carbon nano-onion particles are grown by chemical vapor deposition; after adiabatic treatment, the reaction product is cooled to room temperature at a cooling rate of 5 °C / min under a nitrogen atmosphere to obtain carbon nano-onion particles;

[0079] The obtained carbon nano-onion nanoparticles are mixed with deionized water in a volume ratio of 1:4 - 10, and ultrasonic dispersion is carried out for 6 hours. The ultrasonic-dispersed mixed solution is coated on the surface of the D-shaped fiber and naturally dried in a vacuum-sealed container. After the water evaporates, the carbon nano-onion nanoparticles cover the surface of the D-shaped fiber to form a saturable absorber.

[0080] 2. Conduct fiber laser tests, such as Figure 2As shown in the figure, it is a ring-cavity fiber laser operating at the 2μm band. Among them, 110 is a 1570nm fiber laser, serving as the pump light source. 120 is a 1570nm / 1980nm wavelength division multiplexer. 130 is a 20cm long thulium-doped silica fiber, and 140 serves as the gain medium for laser generation. It is a 1980nm polarization-independent fiber isolator. In order to ensure the unidirectional operation of the laser in the laser cavity, 150 is a fiber connection device. Specifically, a saturable absorber is placed on the surface of the fiber connector. 160 is a polarization controller, used to regulate the polarization state of the laser cavity. 170 is a 10dB optical splitter at 1980nm, used to split and export the generated pulsed light. 180 is the pulsed light output end, which is respectively connected to a spectrometer and an oscilloscope for spectral and pulse tests. All the components in the entire experimental device are connected with single-mode fiber SMF-28 at the cavity joints and then welded by a fiber welding machine. The pump source is the 1570nm fiber laser 110. The pump light is guided into the cavity through the wavelength division multiplexing device 120 operating at 1570 / 1980nm. The 20cm long thulium-doped gain fiber 130 is inserted into the cavity as the gain medium. The isolator 140 mainly ensures the unidirectional transmission of light. The D-type fiber 150 coated with carbon nanotube onion nanoparticles is connected to the laser. The polarization state of the cavity is adjusted by the polarization controller 160. The output laser passes through a 10dB optical coupler 170 to output 10% of the light to the OSA spectrometer or oscilloscope to observe the pulse shape or pulse train. Gradually increase the pump power of the laser 110, adjust the polarization of the fiber laser, and realize the output of mode-locked pulsed laser.

[0081] The experiment is as Figures 11 - 12 shown: The central wavelength of the mode-locked laser spectrum is 1932nm, the interval between adjacent pulse trains is 46.94ns, and the repetition frequency is 27.3MHz.

[0082] The present invention provides a preparation method of a saturable absorber based on carbon nanotube onions. The saturable absorber made by mixing carbon nanotube onion nanoparticles with a film-forming agent has good light transmittance, exhibits an obvious saturable absorption effect, and is simple to prepare and has good stability.

[0083] For the fiber laser provided by the present invention, the saturable absorber made by mixing carbon nanotube onion nanoparticles with a film-forming agent has good laser operation output, stable pulse train data, and good repeatability.

[0084] So far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing a saturable absorber based on carbon nano-onion particles, characterized in that, Comprising: Preparing carbon nano-onion particles; Mixing the carbon nano-onion particles, a film-forming agent and deionized water in proportion to form a mixed solution; After ultrasonic dispersion of the mixed solution, obtaining a saturable absorber based on carbon nano-onions; The preparation of the carbon nano-onion particles includes: Sprinkling the mixed powder of Ni-Fe / Al2O3 and NiO-Fe2O3 into an incubator, and setting the temperature of the incubator to a first reaction temperature; wherein, the mass fraction of Ni-Fe / Al2O3 is 0.2 parts to 1.63 parts, and the mass fraction of NiO-Fe2O3 is 30 to 50 parts; Filling hydrogen into the incubator to reduce the mixed powder, and cooling to room temperature in a nitrogen atmosphere to obtain Ni-Fe powder, wherein the charging flow rate of the hydrogen is 100 mL / min and the charging time is 1 h; Raising the temperature of the incubator to a second reaction temperature, and filling methane, nitrogen and hydrogen, and after constant temperature treatment, growing carbon nano-onion precipitates by chemical vapor deposition; Performing adiabatic treatment on the incubator, and cooling to room temperature in a nitrogen atmosphere, and synthesizing the carbon nano-onion precipitates into carbon nano-onion particles.

2. The preparation method of the saturable absorber based on carbon nano-onion particles according to claim 1, characterized in that, The mass fraction of carbon nano-onion particles in the mixed solution is 0.2 parts to 1.63 parts, the mass fraction of deionized water is 30 to 50 parts, and the mass fraction of the film-forming agent is 8 to 25 parts.

3. The preparation method of the saturable absorber based on carbon nano-onion particles according to claim 1 or 2, characterized in that, After ultrasonic dispersion of the mixed solution, it is coated on the surface of glass or deposited on the surface of a tapered optical fiber, a D-shaped optical fiber or a cladding-etched optical fiber, or filled in the air holes of a photonic crystal, and after drying, a saturable absorber based on carbon nano-onions is obtained.

4. The method for preparing a saturable absorber based on carbon nano-onion particles according to claim 3, characterized in that, The film-forming agent is one or more of sodium carboxymethyl cellulose, polyvinyl alcohol, polymethyl methacrylate or polydimethylsiloxane.

5. The preparation method of the saturable absorber based on carbon nano-onion particles according to claim 4, characterized in that The first reaction temperature is set to 450°C - 500°C.

6. The method for preparing a saturable absorber based on carbon nano-onion particles according to claim 5, characterized in that, The second reaction temperature is 750°C - 950°C, and the heating rate for raising the temperature to the second reaction temperature is 10°C / minute.

7. The preparation method of the saturable absorber based on carbon nano-onion particles according to claim 6, wherein, The cooling rate of the incubator is 5°C / min.

8. A carbon nano-onion-based saturable absorber, characterized in that, A saturable absorber prepared by the method for preparing a saturable absorber based on carbon nano-onion particles according to any one of claims 1-7.

9. An application of the saturable absorber based on carbon nano-onions as claimed in claim 8 in a fiber laser.

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