C-band passively Q-switched pulsed fiber laser and preparation method of saturable absorber based on CsPbBr3 perovskite nanocrystal

Abstract

The present invention discloses a C-band passively Q-switched pulsed fiber laser and a preparation method of a saturable absorber based on CsPbBr3 perovskite nanocrystals, belonging to the field of laser technology. The fiber laser is composed of a pump source, a wavelength division multiplexer, an erbium-doped gain fiber, an optical isolator, a saturable absorber based on a CsPbBr3 perovskite nanocrystal thin film, and a fiber output coupler connected in series end to end in sequence; in the present invention, the prepared CsPbBr3 perovskite nanocrystal thin film saturable absorber is inserted into the fiber laser cavity. Due to the characteristics of large optical absorption coefficient, high carrier mobility, low defect density, high gain value, and low saturation intensity of CsPbBr3 perovskite nanocrystals, it is more conducive to the output of Q-switched pulsed laser; the central wavelength of the Q-switched pulsed laser is about 1560 nm in the C-band, the maximum pulse repetition frequency is 49.70 kHz, the maximum output power is 1.9 mW, and the shortest pulse width is 7.92 μs.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and specifically relates to a C-band passively Q-switched pulsed fiber laser and a CsPbBr-based 3 Method for preparing perovskite nanocrystal saturable absorber. Background Art

[0002] Compared with traditional continuous lasers, pulsed lasers have great application potential in many fields such as biomedicine, spectroscopy, optical communications, and laser processing due to their large pulse energy and high peak power. Among the many pulse laser modulation technologies, passive Q-switching is considered to be one of the most effective methods to achieve pulsed lasers due to its compact cavity structure, low cost, high integration, and flexible design. In passively Q-switched pulsed fiber lasers, saturable absorbers are used as nonlinear optical modulators and play a very important role. The transmittance of saturable absorbers increases with the increase of input laser intensity, thereby realizing the transformation of continuous lasers to pulsed lasers.

[0003] In the past few decades, various optical nanomaterials have been used as saturable absorbers in the field of passive Q-switched laser technology. 3 Perovskite nanocrystals have attracted extensive attention due to their unique properties such as large absorption coefficient, low defect density, and low saturation intensity. In recent years, researchers have been working on CsPbBr 3 The synthesis of perovskite nanocrystals, the exploration of its nonlinear optical absorption properties, and the development of its application potential in the field of pulsed lasers. For example, in 2016, Zhou et al. 3 Nanocrystals were used as saturable absorbers to successfully obtain 1 mm band mode-locked pulse laser output; in 2017, Li et al. used CsPbBr 3 Perovskite quantum dots were used as saturable absorbers to achieve Q-switched pulsed laser output in the visible band (515 nm); subsequently, Liu et al. and Zhou et al. reported the use of CsPbBr 3 Nanocrystals can be used as saturable absorbers to achieve mode-locked pulse laser output in the 1.6 mm and 2 mm bands, respectively. However, despite certain progress, researchers have not found CsPbBr 3 The linear absorption and nonlinear saturable absorption characteristics of nanocrystals in the C band lead to the 3C-band passively Q-switched pulsed lasers with nanocrystal saturable absorbers have not been reported. The C-band is known as the most commonly used band, ranging from 1530nm to 1565nm. The C-band is widely used in fiber-optic communications, satellite communications and other fields due to its advantages such as the lowest fiber loss in fiber-optic communication systems. It is also considered to be the preferred frequency band for commercial 5G. Therefore, it is of great significance to explore the nonlinear optical properties of perovskite nanomaterials in the C-band region and related pulsed laser technologies and applications. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention aims to provide a C-band passively Q-switched pulsed fiber laser and a CsPbBr-based 3 The preparation method of perovskite nanocrystal saturable absorber comprises the following steps: 3 The perovskite nanocrystal film saturable absorber is inserted into the fiber laser cavity to obtain a stable Q-switched pulse laser with a central wavelength of about 1560nm in the C band, a maximum pulse repetition frequency of 49.70kHz, a maximum output power of 1.9mW, and a shortest pulse width of 7.92μs.

[0005] The present invention is achieved through the following technical solutions:

[0006] C-band passive Q-switched pulse fiber laser, composed of pump source, wavelength division multiplexer, erbium-doped gain fiber, optical isolator, CsPbBr 3 The saturable absorber of the perovskite nanocrystal film and the optical fiber output coupler are connected end to end in sequence; wherein the pump source is a 980nm semiconductor laser for generating pump light; the pump light is injected into the erbium-doped gain fiber through a wavelength division multiplexer; the optical isolator is used to ensure the unidirectional transmission of the laser signal in the cavity of the erbium-doped gain fiber; based on CsPbBr 3 The saturable absorber of the nanoperovskite nanocrystal film is used to adjust the Q value in the laser cavity, thereby generating a C-band pulsed laser signal; the generated C-band pulsed laser signal passes through the optical fiber output coupler, and the 10% port of the optical fiber output coupler is used for signal output and test analysis, and the 90% port feeds the remaining laser back to the cavity of the erbium-doped gain fiber for operation.

[0007] Furthermore, the power range of the pump source is 60 mW to 250 mW.

[0008] Furthermore, the CsPbBr 3 The nanocrystalline thin film saturable absorber is placed between two fiber jumper connectors in the fiber laser cavity.

[0009] Furthermore, the CsPbBr 3 The method for preparing a saturable absorber of a nanocrystalline film specifically comprises the following steps:

[0010] Step 1: CsPbBr 3 Preparation of Perovskite Nanocrystals:

[0011] Lead bromide (PbBr 2 ), cesium oleate (Cs-oleate) as raw materials, oleic acid (OA), oleylamine (OAm) and octadecene (ODE) as high temperature solvents, and synthesized by hot injection method;

[0012] Step 2: Based on CsPbBr 3 Preparation of saturable absorbers of perovskite nanocrystal films:

[0013] First, polymethyl methacrylate is dissolved in an acetone solution and stirred to obtain a polymethyl methacrylate (PMMA) film-forming agent; then the obtained polymethyl methacrylate film-forming agent is mixed with the CsPbBr prepared in step 1. 3 The perovskite nanocrystals are mixed in a volume ratio of 1:1-1:2 and ultrasonically dispersed uniformly; finally, the obtained mixture is spin-coated on a quartz substrate and dried naturally at room temperature to obtain a CsPbBr-based 3 Perovskite nanocrystal films are saturable absorbers.

[0014] Furthermore, the CsPbBr prepared in step 1 3 The concentration of perovskite nanocrystals is 40-80 μmol / L.

[0015] Furthermore, the CsPbBr prepared in step 1 3 The size of the perovskite nanocrystals is 20nm.

[0016] Furthermore, step one specifically includes the following contents:

[0017] First, 0.18 mmol of PbBr 2 Add into a mixed solvent of 0.8 mL of oleic acid, 0.8 mL of oleylamine and 5 mL of octadecene, stir and heat to 120°C and react for 30 minutes under vacuum conditions; then, heat to 185°C under a nitrogen atmosphere and inject 0.8 mL of oleylamine, 0.8 mL of oleic acid and 64 mL of cesium oleate into the reaction system in sequence, stir evenly, react for 5 seconds and quickly cool to room temperature in an ice water bath; finally, centrifuge the reaction solution and wash three times with n-hexane and ethyl acetate, and disperse the obtained product in acetone to obtain CsPbBr3 perovskite nanocrystals.

[0018] Furthermore, the mass fraction of the polymethyl methacrylate (PMMA) film-forming agent in step 2 is 5%-15%.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) The CsPbBr 3 perovskite nanocrystal saturable absorber provided by the present invention does not require a complex preparation process and can be synthesized under a low-temperature and low-cost process, which is beneficial to industrial application;

[0021] (2) The CsPbBr 3 perovskite nanocrystals involved in the present invention have characteristics such as a large optical absorption coefficient, a high carrier mobility, a low defect density, a high gain value, and a low saturation intensity, which are more conducive to the output of Q-switched pulsed lasers;

[0022] (3) For the first time, the nonlinear saturable absorption characteristics of the CsPbBr 3 perovskite nanocrystal saturable absorber are utilized to achieve high-stability Q-switched pulsed laser output in the C-band (~1560 nm) region in an erbium-doped fiber laser, providing more possibilities for constructing high-quality pulsed fiber lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0024] Figure 1 : Schematic diagram of the CsPbBr 3 perovskite nanocrystal saturable absorber of the present invention to achieve C-band passive Q-switched pulsed laser output;

[0025] Figure 2 : Transmission electron microscope (TEM) image of the prepared CsPbBr 3 perovskite nanocrystals;

[0026] Figure 3 : Particle size distribution diagram of the prepared CsPbBr 3 perovskite nanocrystals;

[0027] Figure 4 : X-ray diffraction pattern of the prepared CsPbBr 3 perovskite nanocrystals;

[0028] Figure 5 : Absorption spectrum of the CsPbBr 3 perovskite nanocrystal acetone solution;

[0029] Figure 6 : Absorption spectra of the CsPbBr 3 perovskite nanocrystal thin film and the PMMA empty thin film;

[0030] Figure 7 :CsPbBr 3 Saturable absorption characteristic curve of perovskite nanocrystal film;

[0031] Figure 8 :Based on CsPbBr 3 The structure of the C-band passively Q-switched pulsed fiber laser with perovskite nanocrystal saturable absorber, which consists of a 980nm semiconductor laser pump source (980nm LD), a wavelength division multiplexer (WDM), an erbium-doped gain fiber (EDF), an optical isolator (ISO), a CsPbBr3 nanocrystal saturable absorber, and a fiber output coupler (OC);

[0032] Fig. 9 :Spectrum of C-band passively Q-switched pulsed fiber laser;

[0033] Fig.10 : Pulse sequence diagram of C-band passively Q-switched pulse fiber laser;

[0034] Fig.11 : is the single pulse width of the C-band passively Q-switched pulse fiber laser;

[0035] Fig.12 :The relationship between the pulse width and repetition frequency of the C-band passively Q-switched pulse fiber laser and the pump power;

[0036] Fig.13 : is the relationship between the pump power and output power of the C-band passively Q-switched pulsed fiber laser;

[0037] Fig.14 : Time-correlated emission spectrum of a C-band passively Q-switched laser. DETAILED DESCRIPTION

[0038] The embodiments of the technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only used as examples and cannot be used to limit the protection scope of the present invention.

[0039] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the invention belongs.

[0040] Example 1

[0041] like Figure 8 As shown, this embodiment provides a CsPbBr 3C-band passively Q-switched pulsed fiber laser with perovskite nanocrystal saturable absorber, including pump source, wavelength division multiplexer, erbium-doped gain fiber, optical isolator, CsPbBr-based 3 The invention discloses a saturable absorber of a perovskite nanocrystal film and an optical fiber output coupler; wherein the wavelength division multiplexer, erbium-doped gain optical fiber, optical isolator and optical fiber output coupler are connected end to end in sequence; wherein the pump source is a 980nm semiconductor laser for generating pump light; the pump light is injected into the erbium-doped gain optical fiber through the wavelength division multiplexer; the optical isolator is used to ensure the unidirectional transmission of the laser signal in the cavity of the erbium-doped gain optical fiber; based on CsPbBr 3 The saturable absorber of the nanoperovskite nanocrystal film is used to adjust the Q value in the laser cavity, thereby generating a C-band pulsed laser signal; the generated C-band pulsed laser signal passes through the optical fiber output coupler, and the 10% port of the optical fiber output coupler is used for signal output and test analysis, and the 90% port feeds the remaining laser back to the cavity of the erbium-doped gain fiber for operation.

[0042] The CsPbBr 3 The nanocrystalline thin film saturable absorber is placed inside the laser cavity between two fiber patch cord connectors.

[0043] like Figure 1 As shown, it is based on CsPbBr 3 Schematic diagram of C-band passive Q-switched pulse laser output using perovskite nanocrystal saturable absorber. 3 Perovskite nanocrystal film has nonlinear saturable absorption characteristics in the communication C-band (1560nm), and its transmittance increases with the increase of input laser intensity, which plays a role in adjusting the Q value in the laser cavity, thereby realizing the generation of Q-switched pulsed laser in the C-band.

[0044] Example 2

[0045] This embodiment provides a CsPbBr 3 The preparation method of the perovskite nanocrystal saturable absorber specifically comprises the following steps:

[0046] Step 1: CsPbBr 3 Preparation of Perovskite Nanocrystals:

[0047] (1) 0.18 mmol of PbBr 2 , 0.8 mL of oleic acid, 0.8 mL of oleylamine and 5 mL of octadecene were added into a 50 mL two-necked flask, then heated to 120 °C and stirred under vacuum for 30 minutes;

[0048] (2) Then, the reaction system was heated to 185°C under a nitrogen atmosphere and 0.8 mL of oleylamine, 0.8 mL of oleic acid and 64 mL of cesium oleate were rapidly injected in sequence;

[0049] (3) After stirring evenly, react for 5 seconds and then cool rapidly to room temperature in an ice water bath, and centrifuge to separate and precipitate CsPbBr 3 The perovskite nanocrystals were then washed three times with hexane and ethyl acetate, and finally the product was dispersed in acetone;

[0050] like Figure 2 As shown, the prepared CsPbBr 3 Transmission electron microscope (TEM) image of perovskite nanocrystals. It can be seen from the image that the nanocrystal morphology is cubic;

[0051] like Figure 3 As shown, the prepared CsPbBr 3 Particle size distribution of perovskite nanocrystals. It can be seen from the figure that the prepared CsPbBr 3 The average size of perovskite nanocrystals is about 20 nm;

[0052] like Figure 4 As shown, the prepared CsPbBr 3 X-ray diffraction pattern of perovskite nanocrystals. It can be seen from the figure that the prepared CsPbBr 3 Perovskite nanocrystals are monoclinic CsPbBr 3 Perovskite crystal structure;

[0053] like Figure 5 As shown, it is CsPbBr 3 Absorption spectrum of perovskite nanocrystal acetone solution; it can be seen from the figure that CsPbBr 3 The solution has a strong band gap absorption in the range of 300-600 nm, and a relatively weak absorption in the range of 600-2000 nm;

[0054] like Figure 6 As shown, it is CsPbBr 3 Absorption spectra of perovskite nanocrystalline film and PMMA empty film. It can be seen from the figure that the nanocrystalline film exhibits strong absorption characteristics in the near-infrared spectral region (800-2000nm) due to boundary states and surface defects.

[0055] Step 2: Based on CsPbBr 3 Preparation of saturable absorbers of perovskite nanocrystal films:

[0056] (1) Preparation of polymethyl methacrylate (PMMA) film-forming agent:

[0057] Weigh a certain amount of polymethyl methacrylate and add it to acetone solvent, and continue stirring for 4-8 hours until it is completely dissolved, thereby obtaining a polymethyl methacrylate film-forming agent with a mass fraction of 5%-15%;

[0058] (2) The polymethyl methacrylate film-forming agent prepared above was mixed with CsPbBr with a concentration of 40-80 μmol / L. 3 The perovskite nanocrystals were mixed in a volume ratio of 1:1-1:2 and dispersed evenly by ultrasonication, and the resulting mixture was allowed to stand for 48 hours without precipitation;

[0059] (3) Spin-coat the mixed solution prepared above evenly on a 1 cm 2 After drying naturally at room temperature, the CsPbBr 3 Perovskite nanocrystal films are saturable absorbers.

[0060] Figure 7 CsPbBr 3 The saturable absorption characteristic curve of perovskite nanocrystal film shows that CsPbBr 3 The saturation intensity of the nanocrystalline film is 10.9MW / cm 2 , the non-saturation loss is 31.2% and the modulation depth is 19.1%;

[0061] Fig. 9 This is the spectrum of the passively Q-switched pulsed fiber laser in the C band. It can be seen from the figure that the central wavelength of the laser pulse laser output is in the C band of about 1.56μm;

[0062] Fig.10 This is the pulse sequence diagram of the C-band passively Q-switched pulse fiber laser. It can be seen from the figure that the interval between two adjacent pulses is about 25.87μs, and the corresponding pulse repetition frequency is 38.7kHz;

[0063] Fig.11 The single pulse width of the C-band passively Q-switched pulse fiber laser can be seen from the figure, the pulse width is 7.92μs;

[0064] Fig.12 The relationship between the pulse width and repetition frequency of the C-band passively Q-switched pulse fiber laser and the pump power. As can be seen from the figure, as the pump power increases from 60mW to 250mW, the pulse width decreases from 20.73μs to 5.96μs, and the repetition frequency increases from 10.97kHz to 49.70kHz. As the pump power increases, the pulse width decreases and the repetition frequency increases, showing the typical characteristics of a passively Q-switched laser;

[0065] Fig.13The relationship between the pump power and the output power of the C-band passively Q-switched pulsed fiber laser is shown in the figure. As the pump power increases from 60mW to 250mW, the output power increases linearly, and the corresponding maximum output power is 1.9mW, and the corresponding slope is 0.8%;

[0066] Fig.14 This is the time-dependent emission spectrum of the C-band passively Q-switched laser. It can be seen from the figure that the wavelength and intensity of the emission spectrum monitored every 10 minutes within 90 minutes did not change significantly, indicating that the CsPbBr based 3 The C-band passively Q-switched pulsed fiber laser with perovskite nanocrystal saturable absorber has good stability.

[0067] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0069] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. C-band passively Q-switched pulsed fiber laser, It is characterized in that It consists of a pump source, a wavelength division multiplexer, an erbium-doped gain fiber, an optical isolator, and a CsPbBr-based 3 The saturable absorber of the perovskite nanocrystal film and the optical fiber output coupler are connected end to end in sequence; wherein the pump source is a 980nm semiconductor laser for generating pump light; the pump light is injected into the erbium-doped gain fiber through a wavelength division multiplexer; the optical isolator is used to ensure the unidirectional transmission of the laser signal in the cavity of the erbium-doped gain fiber; based on CsPbBr 3 The saturable absorber of the nanoperovskite nanocrystalline film is used to adjust the Q value in the laser cavity, thereby generating a C-band pulse laser signal; the generated C-band pulse laser signal passes through the optical fiber output coupler, the 10% port of the optical fiber output coupler is used for signal output and test analysis, and the 90% port feeds the remaining laser back to the cavity of the erbium-doped gain fiber for operation; The power range of the pump source is 60mW to 250mW; The CsPbBr 3 The nanocrystalline film saturable absorber is placed between two fiber patch cord connectors in the fiber laser cavity; Wherein, the CsPbBr 3 The saturable absorber of the nanocrystalline thin film is prepared by the following method, which specifically comprises the following steps: Step 1: CsPbBr 3 Preparation of Perovskite Nanocrystals: Lead bromide (PbBr 2 ), cesium oleate (Cs-oleate) as raw materials, oleic acid (OA), oleylamine (OAm) and octadecene (ODE) as high temperature solvents, and synthesized by hot injection method; Step 2: Based on CsPbBr 3 Preparation of saturable absorbers of perovskite nanocrystal films: First, polymethyl methacrylate is dissolved in an acetone solution and stirred to obtain a polymethyl methacrylate (PMMA) film-forming agent; then the obtained polymethyl methacrylate film-forming agent is mixed with the CsPbBr prepared in step 1. 3 The perovskite nanocrystals are mixed in a volume ratio of 1:1-1:2 and ultrasonically dispersed uniformly; finally, the obtained mixture is spin-coated on a quartz substrate and dried naturally at room temperature to obtain a CsPbBr-based 3 Perovskite nanocrystal films are saturable absorbers.

2. The C-band passively Q-switched pulsed fiber laser according to claim 1, It is characterized in that Step 1: CsPbBr 3 The concentration of perovskite nanocrystals is 40-80 μmol / L.

3. The C-band passively Q-switched pulsed fiber laser according to claim 1, It is characterized in that Step 1: CsPbBr 3 The size of the perovskite nanocrystals is 20nm.

4. The C-band passively Q-switched pulsed fiber laser according to claim 1, It is characterized in that Step 1 specifically includes the following: First, 0.18 mmol of PbBr 2 Add to a mixed solvent of 0.8 mL oleic acid, 0.8 mL oleylamine and 5 mL octadecene, stir and heat to 120 ° C and react for 30 minutes under vacuum conditions; then, heat to 185 ° C under a nitrogen atmosphere and inject 0.8 mL oleylamine, 0.8 mL oleic acid and 64 mL cesium oleate into the reaction system in sequence, stir evenly, react for 5 seconds and then use an ice water bath to quickly cool to room temperature; finally, centrifuge the reaction solution, wash three times with n-hexane and ethyl acetate, and disperse the obtained product in acetone to obtain CsPbBr 3 Perovskite nanocrystals.

5. The C-band passively Q-switched pulsed fiber laser according to claim 1, It is characterized in that The mass fraction of the polymethyl methacrylate (PMMA) film-forming agent in step 2 is 5%-15%.

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