Broadband saturable absorber and multi-soliton laser

Abstract

The present application discloses a wide-band saturable absorber and a multi-soliton state laser. In the first aspect of the present application, the application of two-dimensional germanium sulfide in saturable absorber materials, saturable absorber devices, lasers and equipment is provided. According to the application of the embodiments of the present application, at least the following beneficial effects are achieved: the applicant discovered during the experiment that the GeS two-dimensional material has a narrow band gap of about 1.6 eV, and the size of the band gap can be tuned by external strain, so it is inferred that it has a wide-band saturable absorption, and the wide-band responsiveness of the saturable absorber device based on the GeS two-dimensional material is confirmed by experiments. Furthermore, the laser made of the saturable absorber device based on the GeS two-dimensional material has good tolerance to high pump power, and pulse splitting will occur under high pump power, resulting in multi-pulse mode locking and harmonic mode locking, and the generation of multi-soliton state phenomenon, so that this laser has certain research value and application value.

Description

Technical Field

[0001] The present application relates to the field of pulse laser technology, and in particular to a wide-band saturable absorber and a multi-soliton laser. Background Art

[0002] The ultrashort pulses generated by lasers are widely used in fields such as communications, detection, mechanical processing, and biomedicine. Both solid-state lasers and fiber lasers can produce high-quality ultrashort pulses. Among them, solid-state lasers face a series of problems such as high price, complex adjustment, poor stability, and strict temperature and humidity requirements. In contrast, fiber lasers have the advantages of low price, high integration, good stability, good environmental compatibility, and convenient collimation output, and have become a hot topic in research in the field. The technologies for generating pulsed lasers in fiber lasers include active mode locking and passive mode locking. Passive mode locking technology can produce shorter pulses without active adjustment and has broader application prospects. In passive mode locking technology, realizing ultrashort pulses based on saturated absorbers is currently a major method. The principle of this method is that when a light pulse passes through a saturable absorber, the light with high energy at the center of the pulse is transmitted, while the light with low energy at the edge of the pulse has greater loss, forming a narrowed light pulse and locking the mode.

[0003] As a typical nonlinear optical system, passively mode-locked fiber lasers can exhibit a variety of complex soliton pulse dynamics, such as dissipative solitons, soliton rain, exploding solitons, breathing solitons, pulsating solitons, optical weird waves, etc. Multi-soliton state pulses can reorganize their own positions and eventually form harmonic mode locking, so that high repetition rate pulse output can be obtained, which has certain research value and application value. However, the generation of multi-soliton states is affected by a combination of factors such as the damage threshold of the material, the dispersion accumulation of the laser resonator, the tolerance of the material to high pump power, and the modulation depth. For example, some saturable absorbers will lose lock at high pump power, resulting in the disappearance of multi-soliton states. On the other hand, most materials have a narrow response band, such as molybdenum disulfide is only applicable to the visible light region, and black phosphorus is only applicable to the near-infrared band, which limits the application potential of various saturable absorber materials. Therefore, it is necessary to provide a saturable absorber that is tolerant to high pump power and has a wide response band, which can still exhibit multi-soliton states at high pump power and achieve multi-pulse mode locking and harmonic mode locking. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a wide-band saturable absorber and a multi-soliton state laser. This saturable light absorber is tolerant to high pump power and has a wide response band, while the multi-soliton state laser can achieve multi-pulse mode locking and harmonic mode locking under high pump power.

[0005] In a first aspect of the present application, there is provided an application of two-dimensional germanium sulfide in any one of the following a1) to a8):

[0006] a1) Saturable absorber materials;

[0007] a2) a saturable absorber device comprising the saturable absorber material described in a1);

[0008] a3) a laser comprising the saturable absorber material described in a1);

[0009] a4) a laser comprising the saturable absorber device described in a2);

[0010] a5) A device comprising the saturable absorber material described in a1);

[0011] a6) A device comprising the saturable absorber device described in a2);

[0012] a7) an apparatus comprising the laser described in a3);

[0013] a8) A device comprising the laser described in a4).

[0014] According to the application of the embodiment of the present application, there are at least the following beneficial effects:

[0015] The applicant discovered during the experiment that GeS2D material has a narrow band gap of about 1.6eV, and the size of the band gap can be tuned by external strain, so it is inferred that it has wide-band saturable absorption, and the wide-band responsiveness of the saturable absorber device based on GeS2D material has been confirmed by experiment. Furthermore, the laser made of saturable absorber device based on GeS2D material has good tolerance to high pump power, and pulse splitting will occur under high pump power, resulting in multi-pulse mode locking and harmonic mode locking, and the generation of multi-soliton state phenomenon, which makes this laser have certain research value and application value.

[0016] According to a second aspect of the present application, a saturable absorber material is provided. The saturable absorber material includes two-dimensional germanium sulfide.

[0017] In some embodiments of the present application, the saturable absorber material may be compounded with other materials on the basis of containing two-dimensional germanium sulfide, for example, compounded with other materials with good nonlinear saturation absorption performance, specifically carbon materials, transition metal carbides, transition metal nitrides, transition metal oxides, transition metal sulfides, transition metal carbonitrides, perovskite materials, metal materials, phosphorus or phosphorus-containing compounds or other sulfides, etc. Among them, carbon materials include but are not limited to graphene and carbon nanotubes. Transition metal elements in transition metal carbides, transition metal nitrides, transition metal oxides, transition metal sulfides, and transition metal carbonitrides include but are not limited to at least one of Ti, Nb, V, Ta, Mo, Cr, etc. Perovskite materials include but are not limited to inorganic perovskite materials, organic perovskite materials, organic-inorganic hybrid perovskite materials, etc. It is understandable that the above materials can also be further modified materials obtained by means of functional group modification, doping, etc. The metal material can be gold nanomaterials, etc. Phosphorus or phosphorus-containing compounds include but are not limited to black scale, phosphide (such as arsenic phosphide, germanium phosphide, etc.), phosphate (such as iron selenophosphite, etc.). In some embodiments, these materials with good nonlinear saturation absorption performance are at least one of zero-dimensional materials, one-dimensional materials, and two-dimensional materials, such as nanocrystals, nanotubes, nanowires, nanosheets, etc.

[0018] In some embodiments of the present application, the number of layers of the two-dimensional germanium sulfide in the saturable absorber material is 1 to 50 layers, such as 1 layer, 2 layers, 3 layers, 4 layers, 5 layers, 10 layers, 15 layers, 20 layers, 30 layers, 40 layers, and 50 layers. In some embodiments, the number of layers of the two-dimensional germanium sulfide in the saturable absorber material is 1 to 30 layers, 1 to 20 layers, 1 to 10 layers, 1 to 8 layers, 1 to 5 layers, and 1 to 3 layers.

[0019] In some embodiments of the present application, the thickness of the two-dimensional germanium sulfide of the saturable absorber material is 30 nm or less, for example, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm. In some embodiments, the thickness of the two-dimensional germanium sulfide in the saturable absorber material is 20 nm or less, 15 nm or less, 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2 nm or less.

[0020] In some embodiments of the present application, the lateral size of the two-dimensional germanium sulfide of the saturable absorber material is below 800nm, for example, 10nm, 20nm, 30nm, 50nm, 100nm, 200nm, 300nm, 500nm, 600nm, 700nm. In some embodiments, the lateral size of the two-dimensional germanium sulfide in the saturable absorber material is below 700nm, below 600nm, below 500nm, below 400nm, below 300nm. The lateral size refers to the lateral length or width of the two-dimensional germanium sulfide.

[0021] In some embodiments of the present application, a method for preparing a saturable absorber material is also involved, specifically including a method for preparing two-dimensional germanium sulfide, which can be prepared by at least one of the methods of "top-down" and "bottom-up". Among them, the "top-down" method includes at least one of mechanical exfoliation and liquid phase exfoliation, and the "bottom-up" method includes at least one of epitaxial growth, chemical vapor deposition, solution synthesis, etc. It can be understood that the two-dimensional germanium sulfide obtained by the above different methods only differs in size and other aspects, but the specific microstructure or performance has not changed significantly, and does not affect its use as a saturable absorber material or its further product raw material.

[0022] In some embodiments of the present application, the preparation method of two-dimensional germanium sulfide is prepared by liquid phase exfoliation, which includes the following steps: mixing blocky germanium sulfide with a solvent, applying shear force, and exfoliating the germanium sulfide into two-dimensional nanosheets.

[0023] In some embodiments of the present application, the solvent used in liquid phase stripping is at least one of water, an organic solvent, and an ionic liquid.

[0024] In some embodiments of the present application, the organic solvent used in the liquid phase stripping is selected from at least one of N-methylpyrrolidone (NMP), N-vinylpyrrolidone (NVP), N-cycloethylpyrrolidone (CHP), N-octylpyrrolidone, formamide, N-methylformamide (NMF), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), methanol, ethanol, ethylene glycol, isopropanol, tert-butanol, acetone, 2-pentanone, 3-pentanone, etc.

[0025] In some embodiments of the present application, the manner of applying shear force during liquid phase stripping includes but is not limited to ultrasound, jetting, homogenization, etc.

[0026] In some embodiments of the present application, the preparation method of two-dimensional germanium sulfide is prepared by liquid phase exfoliation method, comprising the following steps:

[0027] S1: Mix blocky germanium sulfide with a solvent, and ultrasonicate at 100-1000W for 10min-10h to obtain a suspension;

[0028] S2: Centrifuge at 1000-12000 rpm for 10 min-6 h, collect the precipitate, wash and dry to obtain a two-dimensional germanium sulfide nanosheet.

[0029] In some embodiments of the present application, the temperature of the ultrasonic treatment in S1 is 0-25° C. In some embodiments, the temperature of the ultrasonic treatment in S1 is 5-15° C., for example, about 5° C., 6° C., 7° C., 8° C., 9° C., 10° C., 11° C., 12° C., 13° C., 14° C., 15° C.

[0030] In some embodiments of the present application, the power of the ultrasonic treatment in S1 is 100-800 W, 200-600 W, for example, it can be about 200 W, 250 W, 300 W, 350 W, 400 W, 450 W, 500 W, 550 W, or 600 W.

[0031] In some embodiments of the present application, the time for ultrasonic treatment in S1 is 30 min to 8 h, 1 h to 6 h, 2 h to 6 h, 3 h to 5 h, for example, it can be 10 min, 20 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h.

[0032] In some embodiments of the present application, S2 is centrifuged at 1000-3000 rpm for 10 min-1 h, the supernatant is taken and centrifuged at 3000-5000 rpm for 10 min-1 h, the supernatant is taken and centrifuged at 5000-7000 rpm for 10 min-1 h, the supernatant is taken and centrifuged at 7000-9000 rpm for 10 min-1 h, the supernatant is taken and centrifuged at 9000-12000 rpm for 10 min-1 h, the precipitate is collected, washed and dried to obtain two-dimensional germanium sulfide nanosheets.

[0033] According to a third aspect of the present application, a saturable absorber device is provided. The saturable absorber device includes an optical element and the aforementioned saturable absorber material loaded on the optical element.

[0034] In some embodiments of the present application, the optical element includes at least one of optical fiber and transparent glass.

[0035] In some embodiments of the present application, the optical fiber is a micro-nano optical fiber.

[0036] In some embodiments of the present application, the optical fiber is provided with a tapered region, and the saturable absorber material is disposed in the tapered region.

[0037] In some embodiments of the present application, the optical fiber has an end face, and the saturable absorber material is disposed on the end face.

[0038] The embodiments of the present application also provide a method for preparing a saturable absorber device, including providing a saturable absorber material and an optical element, and applying the saturable absorber material to the optical element.

[0039] In some embodiments of the present application, a method for preparing a saturable absorber device includes applying a saturable absorber material to a tapered region or an end face of an optical element.

[0040] In some embodiments of the present application, the method of applying the saturable absorber material to the optical element includes but is not limited to at least one of coating, deposition, bonding, and printing.

[0041] In some embodiments of the present application, the coating method may be to apply a dispersion containing a saturable absorber material to the optical element by at least one of spin coating, roller coating, and the like.

[0042] In some embodiments of the present application, the deposition method may be to immerse the optical element in a dispersion of the saturable absorber material, introduce light of a set wavelength into the optical element to generate an evanescent field, and thereby deposit the saturable absorber material onto the optical element.

[0043] In some embodiments of the present application, the bonding method may be to directly adhere a strip or film containing the saturable absorber material to the optical element.

[0044] In some embodiments of the present application, the imprinting method may be to imprint a strip or film containing a saturable absorber material onto an optical element through a substrate. In some of these embodiments, the substrate may be a flexible substrate or a rigid substrate. In some of these embodiments, the rigid substrate includes but is not limited to a silicon substrate, a silicon dioxide substrate, a silicon nitride substrate, and an organic glass substrate, and the flexible substrate includes but is not limited to a silicone substrate, a polydimethylsiloxane substrate, a polyacrylic acid substrate, a polypropylene substrate, a polyurethane substrate, and a hydrogel substrate.

[0045] According to a fourth aspect of the present application, a laser is provided. The laser includes the aforementioned saturable absorber material, or includes the aforementioned saturable absorber device.

[0046] In some embodiments of the present application, the laser is a fiber laser. In some other embodiments, the laser may also be a solid-state laser.

[0047] In some embodiments of the present application, the laser is an all-fiber laser.

[0048] In some embodiments of the present application, the laser is suitable for visible light, near infrared, and mid-infrared bands. In some embodiments, the visible light band is 380-760nm, the near infrared band is 760-1800nm, and the mid-infrared band is 1800-5000nm.

[0049] In some embodiments of the present application, the wavelength band of the laser includes the 1500±100nm band and the 1800±100nm band. In some embodiments, the wavelength band of the laser includes 1500±80nm and 1800±80nm, 1500±50nm and 1800±50nm, 1500±30nm and 1800±30nm, 1500±20nm and 1800±20nm, 1500±10nm and 1800±10nm.

[0050] In some embodiments of the present application, the laser includes a pump source and a laser resonant cavity which are sequentially arranged along a light propagation direction, and a saturable absorber device is arranged in the laser resonant cavity.

[0051] In some embodiments of the present application, the laser resonant cavity is a ring resonant cavity.

[0052] In some embodiments of the present application, the laser resonant cavity includes the aforementioned saturable absorber and at least one device selected from the group consisting of a wavelength division multiplexer, a gain fiber, a polarization-independent isolator, a fiber coupler, and a polarization controller.

[0053] In some embodiments of the present application, the laser resonant cavity includes the aforementioned saturable absorber, as well as a wavelength division multiplexer, a gain fiber, and a fiber coupler.

[0054] In some embodiments of the present application, the devices in the laser resonant cavity are connected to each other through connecting optical fibers to form the laser resonant cavity. In some embodiments, the connecting optical fibers are single-mode optical fibers.

[0055] In some embodiments of the present application, the gain fiber includes but is not limited to at least one of ytterbium-doped fiber, erbium-doped fiber, and thulium-doped fiber.

[0056] In some embodiments of the present application, the coupling ratio of the optical fiber coupler is 1-x:x, where x is the ratio of the laser output from the output end of the optical fiber coupler.

[0057] In some embodiments of the present application, x is 0 to 1. In some embodiments, x is 0 to 0.9, 0 to 0.8, 0 to 0.7, 0 to 0.6, 0 to 0.5, 0 to 0.4, 0 to 0.3, 0 to 0.2, 0 to 0.1.

[0058] In some embodiments of the present application, the laser resonant cavity includes the aforementioned saturable absorber, as well as a wavelength division multiplexer, a gain fiber, a polarization-independent isolator, a fiber coupler, and a polarization controller.

[0059] In some embodiments of the present application, the pump source provides pump light in the near-infrared band, and the laser resonant cavity includes a wavelength division multiplexer, a gain fiber, a polarization-independent isolator, a saturable absorber, a fiber coupler and a polarization controller connected in sequence along the light propagation direction.

[0060] In some embodiments of the present application, the pump source provides pump light in the mid-infrared band, and the laser resonant cavity includes a wavelength division multiplexer, a gain fiber, a polarization controller, a saturable absorber, a fiber coupler and a polarization-independent isolator connected in sequence along the light propagation direction.

[0061] According to a fifth aspect of the present application, a device is provided, which includes the aforementioned saturable absorber material, or includes the aforementioned saturable absorber device, or includes the aforementioned laser.

[0062] In some embodiments of the present application, the device is at least one of a communication device, a detection device, a mechanical processing device, and a medical device. Ultrashort pulse lasers based on saturable absorbers have broad application prospects in the fields of precision machining, medicine, detection, and communication, so these devices can be communication equipment, detection equipment, mechanical processing equipment, and medical equipment. Among them, the mid-infrared band covers the intrinsic absorption lines of many important atoms or molecules, which is called the "molecular fingerprint region". Therefore, the lasers in the present application that can produce mid-infrared pulse lasers with characteristics such as good stability play an important role in equipment in the fields of bioimaging, gas sensing and detection. In addition, based on its characteristics such as a wide response band, it also has certain application prospects in conventional optical communications, ranging, and other aspects.

[0063] In some embodiments of the present application, a device includes a light source system, and the light source system includes the aforementioned laser.

[0064] The embodiment of the present application provides a saturable absorber based on GeS material and a multi-soliton state laser prepared based on the saturable absorber. The saturable absorber has nonlinear optical response from visible light to mid-infrared bands and can achieve saturated absorption. The laser has good environmental stability, achieves multi-pulse mode locking at least in the near-infrared and mid-infrared bands, and has high tolerance to high pump power.

[0065] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1Element energy spectrum distribution diagram of the two-dimensional GeS nanosheet used in the examples of this application;

[0067] Figure 2 The Z scan characterization results of the GeS thin film prepared in the embodiment of the present application at different wavelengths of 475-1800 nm are shown in FIG. 1 , where a to d represent the scanning results at wavelengths of 475 nm, 800 nm, 1550 nm, and 1800 nm, respectively.

[0068] Figure 3 The structure and experimental results of the near-infrared all-fiber laser provided in Example 1 of the present application are shown in Figure 1. Among them, a is a schematic diagram of the structure of the near-infrared all-fiber laser; b is an output spectrum of the near-infrared all-fiber laser in the near-infrared band; and c is a pulse sequence of the near-infrared all-fiber laser in the near-infrared band.

[0069] Figure 4 The pulse sequence of the near-infrared all-fiber laser provided in Example 1 of the present application under different mode locking conditions, wherein a is a pulse sequence under multi-pulse mode locking, and b is a pulse sequence under harmonic mode locking.

[0070] Figure 5 The structure and experimental results of the mid-infrared all-fiber laser provided in Example 2 of the present application are shown in Figure 1. Among them, a is a schematic diagram of the structure of the mid-infrared all-fiber laser; b is an output spectrum diagram of the mid-infrared all-fiber laser in the mid-infrared band; and c is a pulse sequence of the mid-infrared all-fiber laser in the mid-infrared band. DETAILED DESCRIPTION

[0071] The following will clearly and completely describe the concept of the present application and the technical effects produced in combination with the embodiments, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present application.

[0072] The embodiments of the present application are described in detail below. The described embodiments are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0073] In the description of this application, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, "above", "below", "within", etc. are understood to include the number itself, and "about" means within the range of ±20%, 10%, 8%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.2%, 0.1%, etc. of the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0074] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0075] In the following embodiments, the output performance of the fiber laser is recorded by an optical spectrum analyzer (OSA, YOKOGAWAAQ6370C), a 1GHZ oscilloscope (OSC, Tektronix MDO4104C), a 5GHz detector (Thorlabs DET08CFC / M), an optical autocorrelator (Femtochrome FR-103HS) and a 3.6GHz spectrum analyzer (ESA, Agilent N9030A). The pump source, wavelength division multiplexer, single-mode fiber, polarization controller, polarization-independent isolator, and fiber coupler are conventionally selected in the industry and are not specifically limited in the embodiments of the present application.

[0076] Example 1

[0077] This embodiment provides a GeS nanosheet, which is prepared by a liquid phase exfoliation method, and the specific steps are as follows:

[0078] (1) Commercially available GeS polycrystalline powder (~0.3 mm, 99.999%) was dispersed in anhydrous ethanol (99.9%) solution with an initial concentration of 1 g / L of N-methyl-2-pyrrolidone (NMP, 99.9%) and subjected to ultrasonic treatment at 400 W for 4 h at 10°C to obtain a dark brown suspension.

[0079] (2) Take the dark brown suspension obtained in (1), centrifuge it at 2000 rpm for 30 minutes, and extract the supernatant for further separation.

[0080] (3) Take the supernatant obtained in (2), centrifuge at 4000 rpm for 30 minutes, extract the supernatant by centrifugation at 6000 rpm for 30 minutes, extract the supernatant by centrifugation at 8000 rpm for 30 minutes, and extract the supernatant by centrifugation at 10000 rpm for 30 minutes, collect the precipitate, wash off NMP with ethanol, and dry it in vacuum at 80°C to obtain GeS nanosheets.

[0081] The GeS nanosheets prepared in this example are typical few-layer two-dimensional materials. Electron microscopy results show that the surface is smooth, the lateral size is 800-1500 nm, the thickness is 1.2-1.4 nm, and there are about 3 layers.

[0082] Example 2

[0083] This embodiment provides a saturable absorber device, and the preparation process thereof includes the following steps:

[0084] (1) 1 mg of the GeS nanosheets prepared in Example 1 was added to 10 mL of isopropanol to obtain a mixed solution, and the mixed solution was centrifuged at 5000 rpm for 1 hour to form a uniform dispersion.

[0085] (2) After stripping the coating layer of the single-mode optical fiber, a taper machine is used to perform tapering to form a micro-nano optical fiber with a taper diameter of about 5 to 10 μm.

[0086] (3) Immerse the micro-nano optical fiber prepared in step (2) in the GeS nanosheet dispersion prepared in step (1), and fuse the output tail fiber of the 980nm continuous light output semiconductor laser and one end of the micro-nano optical fiber, inject a laser beam into the micro-nano optical fiber at a power of 50mW for 30 minutes, and utilize the strong evanescent field of the micro-nano optical fiber to deposit the GeS nanosheets on the side of the cone region of the micro-nano optical fiber, thereby completing the preparation of the saturable absorber device.

[0087] The saturable absorber device prepared in this embodiment includes a micro-nano optical fiber and two-dimensional GeS deposited in a tapered region of the micro-nano optical fiber.

[0088] The elemental composition of GeS2 nanosheets in the GeS2 dispersion was analyzed by scanning electron microscopy. Figure 1 As shown, the GeS2 two-dimensional nanosheets are composed of two elements, S and Ge, with a content of approximately 1:1, which conforms to the GeS chemical formula stoichiometric ratio.

[0089] In order to characterize the saturable absorption characteristics of two-dimensional GeS materials, the transmittance of the GeS film deposited on the micro-nano optical fiber at wavelengths of 475nm, 800nm, 1550nm and 1800nm ​​was measured using a Z-scan description device. Figure 2As shown, in the open hole state, the curve has the maximum transmittance, indicating that the GeS film has nonlinear optical absorption under the action of these four bands, has strong saturable absorption characteristics, and can be used as a wide-band saturable absorber material from visible light to mid-infrared bands.

[0090] Example 3

[0091] This embodiment provides an all-fiber laser in the near-infrared band. Figure 3 The all-fiber laser includes a pump source (Pump) and a laser resonant cavity arranged in sequence along the light propagation direction. The laser resonant cavity includes a wavelength division multiplexer (WDM), a gain fiber (EDF), a polarization-independent isolator (ISO), a saturable absorber device (GeS SA), an optical fiber coupler (OC) and a polarization controller (PC) arranged in sequence along the light propagation direction to form a ring resonant cavity structure. Each device is connected by a single-mode optical fiber (SMF).

[0092] Wherein, the wavelength division multiplexer includes at least one pump end (or reflection end), at least one common end and at least one signal end. The pump source is connected to the pump end of the wavelength division multiplexer through a single-mode optical fiber, so that the pump light is input into the laser resonant cavity. One end of the gain optical fiber is connected to the common end of the wavelength division multiplexer, and the other end is connected to the input end of the polarization-independent isolator. The output end of the polarization-independent isolator is connected to one end of the saturable absorber device. The saturable absorber device is the saturable absorber device prepared in Example 2, and the other end is connected to the input end of the optical fiber coupler. The coupling ratio of the optical fiber coupler is 90:10, and the 10% end of the optical fiber coupler outputs signal light, and the 90% end is fused with a section of single-mode optical fiber and connected to one end of the polarization controller. The other end of the polarization controller is connected to the signal end of the wavelength division multiplexer.

[0093] The pump source used by the all-fiber laser in this embodiment is a laser diode light source with a wavelength of 976nm. The gain fiber is an erbium-doped fiber, which is used as the gain medium of the laser and has a length of 1.5m. The cavity length of the all-fiber laser is about 13m.

[0094] refer to Figure 3 b and c, the saturable absorber device based on the two-dimensional GeS material provided in Example 2 achieves stable mode-locked pulse output in the near-infrared laser resonant cavity of this embodiment, and successfully obtains stable mode-locking at low pump power. Among them, Figure 3 FIG. 5 b shows the output spectrum of the all-fiber laser, from which obvious symmetrical Kelly sidebands can be seen, with a central wavelength of 1564.35 nm and a 3 dB bandwidth of 3.1 nm. Figure 3Figure c shows the output pulse sequence. It can be seen from the figure that the output pulses have good stability, and their interval is about 143ns, corresponding to a repetition frequency of 6.8MHz, which is consistent with the cavity length.

[0095] Figure 4 Figures a and b show the pulse states of multi-pulse mode locking and harmonic mode locking caused by pulse splitting of the all-fiber laser of this embodiment at a high pump power of 840 mW, respectively, maintaining the same Figure 3 The same stability is achieved at low pump powers as shown. These different pulse states can be transformed by adjusting the polarization controller. The above results show that the near-infrared all-fiber laser provided in Example 3 has good tolerance to high pump powers.

[0096] Example 4

[0097] This embodiment provides an all-fiber laser in the mid-infrared band. Figure 5 The all-fiber laser includes a pump source (Pump) and a laser resonant cavity arranged in sequence along the light propagation direction. The laser resonant cavity includes a wavelength division multiplexer (WDM), a gain fiber (TDF), a polarization controller (PC), a saturable absorber device (GeSSA), an optical fiber coupler (OC) and a polarization-independent isolator (ISO) arranged in sequence along the light propagation direction to form a ring resonant cavity structure. Each device is connected by a single-mode optical fiber (SMF).

[0098] Wherein, the wavelength division multiplexer includes at least one pump end (or reflection end), at least one common end and at least one signal end. The pump source is connected to the pump end of the wavelength division multiplexer through a single-mode optical fiber, so that the pump light is input into the laser resonant cavity. One end of the gain optical fiber is connected to the common end of the wavelength division multiplexer, and the other end is connected to one end of the polarization controller. The other end of the polarization controller is connected to one end of the saturable absorber device. The saturable absorber device is the saturable absorber device prepared in Example 2, and the other end is connected to the input end of the optical fiber coupler. The coupling ratio of the optical fiber coupler is 80:20, and the 20% end of the optical fiber coupler outputs signal light, and the 80% end is fused with a section of single-mode optical fiber and connected to the input end of the polarization-independent isolator. The other end of the polarization-independent isolator is connected to the signal end of the wavelength division multiplexer.

[0099] The pump source used by the all-fiber laser in this embodiment is a laser diode light source with a wavelength of 1550nm. The gain fiber is a thulium-doped fiber, which serves as the gain medium of the laser. The cavity length of the all-fiber laser is about 33m.

[0100] The saturable absorber device based on the two-dimensional GeS material provided in Example 2 achieves mode-locked pulse output in the mid-infrared laser resonant cavity of this embodiment, which is due to the broadband nonlinear optical properties of the two-dimensional GeS material. The laser is similar to Example 3, and the polarization controller can be appropriately adjusted to achieve stable mode locking at a high pump power of 840mw. The relevant results are shown in Figure 5 As shown in b and c. Figure 5 FIG. 5 b shows the output spectrum of the all-fiber laser, from which obvious symmetrical Kelly sidebands can be seen, with a central wavelength of 1933.96 nm and a 3 dB bandwidth of 2.52 nm. Figure 5 Figure c shows the output pulse sequence, from which it can be seen that the output pulses have good stability, and their interval is about 100ns, corresponding to a repetition frequency of 10.0MHz, which is consistent with the cavity length. The above results show that the mid-infrared band all-fiber laser provided in Example 4 also has good tolerance to a high pump power of 840mw (e.g., 840mW).

[0101] Comparative Example 1

[0102] This comparative example provides an all-fiber laser, which differs from Example 3 in that the material used in the saturable absorber device is SnS 2 , SnS 2 The obtained product is prepared by a liquid phase exfoliation method similar to that in Example 1.

[0103] The spectral shape and pulse sequence of the all-fiber laser were in the single-pulse mode-locked state when the pump power increased from 75mW to 500mW. When the pump power increased further, the laser lost the lock. In addition, no multi-pulse phenomenon was observed during the above experiment, and the pulse sequence was unstable.

[0104] Comparison of Example 1 with Examples 3 and 4 shows that based on SnS 2 The maximum power of the mode-locked laser is 500mW. It loses lock when it exceeds 500mW and no multi-pulse phenomenon is observed. However, the GeS material used in the embodiment of the present application is tolerant to high power and remains in a mode-locked state when the pump power reaches 800mW. This property of tolerance to high pump power allows the laser of this patent to undergo pulse splitting at high power, resulting in multi-pulse mode-locking and multi-soliton state phenomena of harmonic mode-locking.

[0105] Example 5

[0106] This embodiment provides a saturable absorber device, which differs from the embodiment 2 in that the source of the GeS nanosheets is different, specifically, after centrifugation at 4000 rpm for 30 min in step (3) of the embodiment 1, the collected precipitate is washed with ethanol and vacuum dried at 80° C. The thickness of the GeS nanosheets is about 14 nm, and there are about 28 layers.

[0107] Example 6

[0108] This embodiment provides a saturable absorber device, which differs from the embodiment 2 in that the source of the GeS nanosheets is different, specifically, after centrifugation at 6000 rpm for 30 min in step (3) of the embodiment 1, the collected precipitate is washed with ethanol and vacuum dried at 80° C. The thickness of the GeS nanosheets is about 4.2 nm, and there are about 8 layers.

[0109] Example 7

[0110] This embodiment provides a saturable absorber device, which differs from the embodiment 2 in that the source of the GeS nanosheets is different, specifically, after centrifugation at 8000 rpm for 30 min in step (3) of the embodiment 1, the collected precipitate is washed with ethanol and vacuum dried at 80° C. The thickness of the GeS nanosheets is about 3.2 nm, and there are about 6 layers.

[0111] Example 8

[0112] This embodiment provides a saturable absorber device, which is different from Embodiment 2 in that the source of GeS nanosheets is different. In this embodiment, the GeS nanosheets are obtained by exfoliation using a mechanical ball milling method.

[0113] Example 9

[0114] This embodiment provides a saturable absorber device, and the preparation steps are as follows:

[0115] (1) 2 mL of 1-dodecanethiol (1-DDT), 3 mL of 1-octadecene (ODE), and 2 mL of oleylamine (OAm) were mixed in N 2 Add to a 25 mL three-necked round-bottom flask under N atmosphere, install it on a reflux condenser, and 2 As carrier gas, 0.2 mmol GeI was added to the mixture. 4 Continue to pass N 2 to remove water and other impurities. Then the flask was placed under N 2 The mixture was heated to 320°C and reacted for 10 hours to obtain a dark purple mixture. Acetone was added to precipitate the nanosheets, which were centrifuged at 4000 rpm for 3 minutes, washed and dried to obtain GeS nanosheets.

[0116] (2) Then, 10 g of polyvinyl alcohol (PVA) powder was dissolved in 80 mL of deionized water and stirred at 145° C. until completely dissolved. Then, the GeS nanosheets prepared in step (1) were added and stirred for 4 hours. The mixture was introduced into a culture dish and dried at room temperature. After standing for 2 days, the GeS film was peeled off.

[0117] (3) Take the single-mode optical fiber after stripping the coating layer, and use a taper machine to taper it to form a micro-nano optical fiber with a taper diameter of about 5 to 10 μm. The GeS film obtained in step (2) is bonded to the end face of the micro-nano optical fiber to complete the preparation of the saturable absorber device.

[0118] Embodiments 10 to 14

[0119] Embodiments 10 to 14 provide an all-fiber laser respectively, which differs from embodiment 3 in that the saturable absorber device respectively adopts the saturable absorber device in the above embodiments 5 to 9. After detection, the all-fiber lasers provided by embodiments 10 to 14 can also generate mode-locked pulses, and cause multi-pulse mode-locking and harmonic mode-locking under high pump power, realize multi-soliton pulse output, and have good stability.

[0120] From the above embodiments, it can be seen that by using two-dimensional GeS material, a saturable absorber with good stability and modulation performance from visible light to mid-infrared bands can be obtained. The laser environment constituted by it has good stability, can achieve mode locking in a multi-pulse state, obtain multi-soliton pulse output, has tolerance to high pump power, and can be further applied to multi-soliton state lasers to better meet scientific research and commercial needs.

[0121] The present application is described in detail above in conjunction with the embodiments, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. Laser, It is characterized in that A saturable absorber device is provided, wherein the saturable absorber device comprises an optical element and a saturable absorber material loaded on the optical element, wherein the saturable absorber material comprises a two-dimensional germanium sulfide nanosheet, wherein the lateral dimension of the two-dimensional germanium sulfide nanosheet is 800-1500 nm, and the thickness is 1.2-1.4 nm, and the saturable absorber material has a saturable absorption characteristic from visible light to mid-infrared band; The two-dimensional germanium sulfide nanosheet is prepared by the following method: (1) GeS polycrystalline powder was dispersed in anhydrous ethanol solution of N-methyl-2-pyrrolidone with an initial concentration of 1 g / L, and ultrasonicated at 400 W for 4 h at 10 °C to obtain a dark brown suspension; (2) taking the dark brown suspension, centrifuging at 2000 rpm for 30 minutes, and extracting the supernatant; (3) Take the supernatant in (2), centrifuge at 4000 rpm for 30 minutes, extract the supernatant by centrifugation at 6000 rpm for 30 minutes, extract the supernatant by centrifugation at 8000 rpm for 30 minutes, extract the supernatant by centrifugation at 10000 rpm for 30 minutes, collect the precipitate, wash away NMP with ethanol, and dry it in vacuum at 80°C to obtain GeS nanosheets.

2. The laser according to claim 1, It is characterized in that The optical element includes an optical fiber.

3. The laser according to claim 2, It is characterized in that The optical fiber is provided with a tapered region, and the saturable absorbing material is deposited in the tapered region.

4. The laser according to claim 1, It is characterized in that The laser comprises a pump source and a laser resonant cavity which are sequentially arranged along the light propagation direction, and the saturable absorber device is arranged in the laser resonant cavity.

5. The laser according to claim 4, It is characterized in that The pump source provides pump light in the near-infrared band, and the laser resonant cavity comprises a wavelength division multiplexer, a gain optical fiber, a polarization-independent isolator, the saturable absorber, an optical fiber coupler and a polarization controller which are sequentially connected along the light propagation direction.

6. The laser according to claim 4, It is characterized in that The pump source provides pump light in the mid-infrared band, and the laser resonant cavity comprises a wavelength division multiplexer, a gain fiber, a polarization controller, the saturable absorber, a fiber coupler and a polarization-independent isolator which are sequentially connected along the light propagation direction.

7. Equipment, It is characterized in that A laser comprising the laser according to any one of claims 1 to 6.

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