阅读说明：本技术 一种碳纳米管饱和吸收体及激光装置 (Carbon nanotube saturable absorber and laser device ) 是由 阮双琛 许新统 陈加骐 于 2021-05-10 设计创作，主要内容包括：本发明提供了一种碳纳米管饱和吸收体及激光装置,其中,所述碳纳米管饱和吸收体包括：纳米分子筛和碳纳米管；所述纳米分子筛包括晶体孔道,所述碳纳米管固定在所述晶体孔道内。以分子筛晶体为模版合成出高定向碳纳米管,由于碳纳米管被规则地分布在分子筛的孔道内,从而使得碳纳米管饱和吸收体不易发生团聚,同时,分子筛的孔道可以为碳纳米管提供保护,有效阻隔空气和水汽对碳纳米管的影响,提升了碳纳米管饱和吸收体的稳定性,分子筛的孔道对碳纳米管的外包覆及均匀分布使得碳纳米管饱和吸收体的光损伤阈值得到较大的提升。通过偏振态的变化即可实现其调制深度的大幅度变化,从而实现脉冲激光运行状态在调Q及锁模之间的任意切换。(The invention provides a carbon nanotube saturable absorber and a laser device, wherein the carbon nanotube saturable absorber comprises: nano molecular sieve and carbon nanotube; the nanometer molecular sieve comprises a crystal pore canal, and the carbon nano tube is fixed in the crystal pore canal. The molecular sieve crystal is used as a template to synthesize the highly oriented carbon nanotube, and the carbon nanotube is regularly distributed in the pore channel of the molecular sieve, so that the carbon nanotube saturated absorber is not easy to agglomerate, meanwhile, the pore channel of the molecular sieve can provide protection for the carbon nanotube, the influence of air and water vapor on the carbon nanotube is effectively blocked, the stability of the carbon nanotube saturated absorber is improved, and the light damage threshold of the carbon nanotube saturated absorber is greatly improved due to the outer coating and uniform distribution of the pore channel of the molecular sieve on the carbon nanotube. The modulation depth can be greatly changed through the change of the polarization state, so that the random switching of the running state of the pulse laser between Q modulation and mode locking is realized.)

1. A carbon nanotube saturable absorber, comprising: nano molecular sieve and carbon nanotube; the nanometer molecular sieve comprises a crystal pore canal, and the carbon nano tube is fixed in the crystal pore canal.

2. The carbon nanotube saturable absorber of claim 1, wherein the carbon nanotube is a single-walled carbon nanotube.

3. The carbon nanotube saturable absorber of claim 2, wherein the single-walled carbon nanotube has a tube diameter of less than 1 nm.

4. The carbon nanotube saturable absorber of claim 1, wherein the crystal pore is a one-dimensional crystal pore.

5. The carbon nanotube saturable absorber of any one of claims 1-4, wherein the nanomolecular sieve is a metal-doped nanomolecular sieve.

6. The carbon nanotube saturable absorber of claim 1, wherein the nanomolecular sieve is an AEL zeolite.

7. A laser device, comprising: the carbon nanotube saturable absorber of claim 1.

8. The laser apparatus of claim 7, further comprising: the device comprises a laser, a wavelength division multiplexer, an optical fiber, an isolator, a polarization controller and an output coupler; the laser, the wavelength division multiplexer, the isolator, the polarization controller, the carbon nano tube saturated absorber and the output coupler are sequentially conducted through the optical fibers from head to tail.

9. The laser device of claim 8, wherein the optical fiber is a doped fiber selected from any one of erbium doped fiber, ytterbium doped fiber, and thulium doped fiber.

10. The laser apparatus of claim 9, wherein the carbon nanotube saturable absorber comprises a jumper port, the carbon nanotube saturable absorber being connected to the optical fiber through the jumper port.

Technical Field

The invention relates to the technical field of lasers, in particular to a carbon nanotube saturable absorber and a laser device.

Background

The pulse laser has the characteristics of narrow pulse width, high peak power, wide spectrum and the like, and has unique application value in the fields of national defense, space exploration, optical communication, biomedicine, material precision processing and the like. The passive Q-switching or mode-locking technology based on the saturable absorber is an effective way for realizing pulse laser, and has the advantages of simple cavity structure, easy realization and the like. The generation of the pulse laser mainly has two modes of active modulation and passive modulation, the active modulation needs to be realized by adding a modulator in a laser cavity, the cost is high, and the carrying is inconvenient; passive modulation, which requires no external devices, is the mainstream development.

At present, most commercial pulse lasers adopt a Q-switching or mode-locking technology, namely, a saturable absorber is introduced into a laser cavity, so that pulse modulation of laser is realized. Common saturated absorbers comprise dyes, semiconductor saturated absorbers and emerging two-dimensional materials (graphene, black phosphorus, molybdenum disulfide and the like), wherein the graphene has the advantages of high carrier mobility, wide-band response, large specific surface area and the like, but the absorption efficiency is low; the adjustable band gap characteristic and the good absorption at specific wavelength of the molybdenum disulfide make up the defects of the graphene, but the yield of the molybdenum disulfide is limited due to the large band gap and the complex preparation process; the black phosphorus is suitable for working in near-infrared bands, but is sensitive to the surrounding environment, has poor stability, cannot stably work for a long time, and cannot normally work in special environments such as humidity and the like; the semiconductor saturable absorber mirror has a small working wavelength range, is complex and expensive to manufacture, and simultaneously, the structures are accompanied with large insertion loss, so that the semiconductor saturable absorber mirror is not beneficial to the generation of large-energy and high-power ultrashort pulses.

Therefore, the prior art is still to be further improved.

Disclosure of Invention

The invention provides a carbon nanotube saturable absorber and a laser device, and aims to solve the technical problems that the saturable absorber in the prior art is sensitive to the environment and poor in stability to a certain extent.

The technical scheme for solving the technical problems is as follows:

in a first aspect, a carbon nanotube saturable absorber, comprising: nano molecular sieve and carbon nanotube; the nanometer molecular sieve comprises a crystal pore canal, and the carbon nano tube is fixed in the crystal pore canal.

Optionally, the carbon nanotube saturable absorber, wherein the carbon nanotube is a single-walled carbon nanotube.

Optionally, the carbon nanotube saturable absorber, wherein a tube diameter of the single-walled carbon nanotube is less than 1 nm.

Optionally, the carbon nanotube saturable absorber, wherein the crystal pore is a one-dimensional crystal pore.

Optionally, the carbon nanotube saturable absorber, wherein the nano molecular sieve is a metal element doped nano molecular sieve.

Optionally, the carbon nanotube saturable absorber, wherein the nanomolecular sieve is AEL zeolite crystals.

In a second aspect, a laser apparatus includes: the carbon nanotube saturable absorber described above.

Optionally, the laser device further includes: the device comprises a laser, a wavelength division multiplexer, an optical fiber, an isolator, a polarization controller and an output coupler; the laser, the wavelength division multiplexer, the isolator, the polarization controller, the carbon nano tube saturated absorber and the output coupler are sequentially conducted through the optical fibers from head to tail.

Optionally, the laser device, wherein the optical fiber is a doped optical fiber, and the doped optical fiber is selected from any one of an erbium-doped optical fiber, an ytterbium-doped optical fiber, and a thulium-doped optical fiber.

Optionally, the laser apparatus, wherein the carbon nanotube saturable absorber includes a jumper port, and the carbon nanotube saturable absorber is connected to the optical fiber through the jumper port.

Has the advantages that: the invention provides a carbon nanotube saturable absorber, wherein a carbon nanotube is fixed in a crystal pore channel of a nano molecular sieve, the nano molecular sieve can provide an environment protection effect for the carbon nanotube, and can effectively isolate the influence of air and water vapor on the saturable absorber, so that the carbon nanotube saturable absorber has high stability.

Drawings

Fig. 1 is a schematic structural diagram of a carbon nanotube saturable absorber according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a laser device according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a polarization dependent saturation absorption characteristic test provided by an embodiment of the present invention.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The inventor researches and discovers that when the pulse generated by the conventional pulse laser is modulated, a saturable absorber is introduced into a laser cavity, and the pulse modulation is realized by utilizing the saturable absorber. However, the existing saturable absorber manufacturing process is complex, and the structure of the prepared saturable absorber has large insertion loss and narrow response band and is easily influenced by environmental factors.

In order to solve the above technical problem, the present application provides a carbon nano saturable absorber, including: nano molecular sieve and carbon nanotube, the carbon nanotube is located (fixed) in the crystal pore canal of the nano molecular sieve. The crystal pore canal can provide an environment protection effect for the carbon nano material saturable absorber, and can effectively isolate the influence of air and water vapor on the saturable absorber, thereby improving the stability of the saturable absorber. The problem that the existing saturated absorber is easily influenced by environmental factors is solved.

As shown in fig. 1, fig. 1 is a schematic structural diagram of a carbon nanotube saturable absorber according to an embodiment of the present invention. The carbon nanotube saturable absorber includes: a nanometer molecular sieve 10 and a carbon nano tube 20 fixed in the pore canal of the nanometer molecular sieve crystal. Wherein the nanomolecular sieve 10 is an AEL zeolite crystal comprising pores 11, the pores 11 being highly oriented and having a dimension along the c-axis of the AEL zeolite crystal of about 100 μm x 100 μm. The duct 11 is a one-dimensional duct. The one-dimensional pore canal of the AEL zeolite crystal can be used for synthesizing the single-hand carbon nano tube.

In this embodiment, the carbon nanotube is a single-walled carbon nanotube, the diameter of the single-walled carbon nanotube is less than 1nm, the single-walled carbon nanotube has a single property and is easy to control, and the light damage threshold of the formed carbon nanotube saturable absorber can be increased by selecting a carbon nanotube with a diameter of less than 1 nm.

In this embodiment, the carbon nanotube saturable absorber may be prepared by using a molecular sieve as a template, pyrolyzing an organic amine or other carbon source, and then placing the host in a crystal pore channel of the molecular sieve template, wherein a decomposition product is a carbon-rich substance, and the carbon-rich substance is prepared into a highly oriented carbon nanotube array saturable absorber in a limited domain space of a one-dimensional pore channel of the carbon nanotube array by using a molecular sieve template method.

In this example, the carbon nanotube saturable absorber was prepared as follows.

Illustratively, the AEL zeolite large single crystal is synthesized by taking aluminum isopropoxide (98 wt%, 15ldrich), orthophosphoric acid (85 wt%, 15ldrich), DP15, hydrofluoric acid and deionized water as raw materials, and the sol component molar ratio adopted by a hydrothermal method is x ZnO: Al₂O₃:P₂O₅:y DPA:600H₂0.9HF, wherein x and y can be adjusted according to different experimental systems, the formed initial sol for preparing the crystals is filled into an autoclave with a polytetrafluoroethylene lining, and the sealed autoclave is put into a preset temperature of between 150 and 190 ℃ (such as 180 ℃) to crystallize for not less than 20 hours to obtain the AEL zeolite crystals. The AEL zeolite single crystal is then pyrolyzed under the high vacuum condition of 500-800 ℃ (such as 600 ℃), and the crystal is changed into dark black from the original transparent colorless state after pyrolysis, and has polarization absorption characteristic for light. The one-dimensional pore channel structure of the AEL zeolite crystal is characterized by being an ideal template for synthesizing a single-handed carbon nanotube. The (2,2) chiral single-walled carbon nanotube is successfully synthesized by using the AEL zeolite crystal as a template. The synthesized (2,2) hand-type single-walled carbon nanotubes were verified by polarized raman spectroscopy, which demonstrated that the templates of this host within the pore channels of AEL zeolite were highly oriented. The oriented carbon nanotube has good polarization absorption characteristic to light, and lays a good foundation for the development of a polarization-related saturable absorber.

In this embodiment, the molecular sieve crystal hosting the carbon-aligned carbon nanotube array is an ideal saturable absorber, and participates in the preparation of the laser device, and the carbon nanotube saturable absorber participates in the modulation of laser light, and can be realized by coating a carbon nanotube saturable absorber material on a reflector, transparent glass or an optical fiber port. The laser device involved in the preparation has the following advantages:

(1) the stability of the pulse fiber laser device is obviously improved. The prepared carbon nano has good dispersibility due to the regular distribution of molecular sieve pore passages, and can overcome the defect that a saturable absorber of a nano material is easy to agglomerate; (2) the construction of the laser device is simplified, and the integration of the saturable absorber device is convenient to realize. Only one molecular sieve crystal host with carbon nano materials (carbon nano tubes) is arranged at the jumper end of the optical fiber to be integrated into the optical fiber cavity; (3) the molecular sieve crystal can provide an environment protection effect for the carbon nano material saturable absorber, and can effectively isolate the influence of air and water vapor on the saturable absorber; (4) the external coating and uniform distribution of the nano-pores of the molecular sieve can improve the optical damage threshold of the saturable absorber of the carbon nano-tube; (5) the preparation cost of the carbon nanotube saturable absorber is greatly reduced, and once the molecular sieve framework is doped with metal elements, the synthesis temperature of the carbon material can be greatly reduced; (6) the non-linear parameter (such as modulation depth) adjustable range of the carbon nano tube saturable absorber is large, and the modulation depth can be greatly changed through the change of the polarization state, so that the random switching of the pulse laser operation state between Q modulation and mode locking is realized, and the application field of the corresponding optical fiber laser is widened. The host refers to a nano molecular sieve in which carbon nanotubes are fixed in crystal pores.

Based on the same inventive concept, as shown in fig. 3, embodiments of the present invention further provide a laser apparatus, which is an erbium-doped (including but not limited to doped fiber illustrated in the figure) all-fiber laser. The all-fiber laser included the AEL @ CNT-based saturable absorber of example 1. The all-fiber laser comprises seven parts which are respectively as follows: the device comprises a pump laser 1, a wavelength division multiplexer 2, a doped optical fiber 3, a polarization-independent isolator 4, a polarization controller 5, a molecular sieve @ carbon nanotube saturable absorber 6 and an output coupler 7. The wavelength division multiplexer 2, the erbium-doped optical fiber 3, the polarization-independent isolator 4, the polarizer 5, the molecular sieve @ carbon nanotube-based saturable absorber 6 and the output coupler 7 are sequentially in first-end optical conduction, the pump laser 1 and the wavelength division multiplexer 2 are in optical conduction and are used as a pump source, and the output coupler 7 is used for outputting laser.

It should be noted that, in this embodiment, the laser device is a ring cavity structure, a Laser Diode (LD) for 980nm/1550nm is used as a pump source, and the pump light is coupled into the laser resonant cavity by a Wavelength Division Multiplexer (WDM) of 980/1550. Single mode Erbium Doped Fiber (EDF), Ytterbium Doped (YDF) or Thulium Doped (TDF) may be used as the gain medium. An optical Isolator (ISO) is then connected to ensure that the light within the cavity is unidirectionally propagating. The polarization state in the fiber cavity is adjusted by a Polarization Controller (PC). An Optical Coupler (OC) is used to couple out 10% (not limited to other output powers) for laser metrology characterization.

Next, we measured the polarization dependent saturation absorption of 0.4nm highly aligned carbon nanotubes in the 1.5 μm band. Fig. 3 is a schematic diagram of a structure for performing a polarization dependent saturable absorption characteristic test, in which a femtosecond light source 12 is used, a polarization controller 13 is used to adjust the polarization state of light, a coupler 14 is used to divide the pulse energy into 50% and 50% which are respectively measured by an optical power meter 15 and an optical power meter 16, one path is through SWCNTs @ AEL (carbon nanotube saturable absorber) 17, the other path is not inserted, and finally the respective powers are measured by a power meter. The parameters of the adopted pulse laser are as follows: the center wavelength of operation was 1560nm, the pulse width was 200fs, and the repetition frequency was 22 MHz. With a certain power of pump light, we adjust the polarization controller so that the power meter 15 and the power meter 16 have the largest difference. In this case, the polarization direction of the laser light by aligning the carbon nanotubes is parallel to the direction of the carbon nanotubes (E/C), because in this state, the absorption of light by the carbon nanotubes is the largest. Then, with the polarization controller fixed, the saturation absorption characteristic of the carbon nanotube in this state (E/C) can be obtained by measuring a series of values on the power meter 15 and the power meter 16 by changing the power of the pump light, and after fitting the data with a non-linear method, we can see that the modulation depth of the carbon nanotube in this state (E/C) is 9.5%. By using the same method, the saturable absorption characteristic of the carbon nano tube can be measured when the laser polarization direction is vertical to the direction of the carbon nano tube (E ^ C). At a certain pump power, the difference between the power meter 15 and the power meter 16 is minimized by modulating the polarization controller, and the polarization direction of the laser is perpendicular to the direction of the carbon nanotubes, because the absorption of light by the aligned carbon nanotubes is minimal in this state. Then, under the condition that the polarization controller is fixed, the saturated absorption characteristic of the carbon nanotube under the state (E:) can be obtained by measuring a series of values on the power meter 15 and the power meter 16 by changing the power of the pump light, and after nonlinear fitting data, the modulation depth of the carbon nanotube under the state (E:) can be seen to be 4.5%. The polarization-dependent saturated absorption characteristic fully indicates that the high-orientation 0.4nm single-walled carbon nanotube can be used as a polarization-sensitive saturable absorber to realize the erbium-doped fiber laser with switchable pulse states. When the set pump power is 330mW, a stable mode-locked pulse output can be obtained by proper polarization controller adjustment, and the signal-to-noise ratio is 67dB, indicating that the pulse signal has good stability.

In summary, the present invention provides a carbon nanotube saturable absorber and a laser device including the same, wherein the carbon nanotube saturable absorber includes: nano molecular sieve and carbon nanotube; the nanometer molecular sieve comprises a crystal pore canal, and the carbon nano tube is fixed in the crystal pore canal. The carbon nanotube saturable absorber is characterized in that a molecular sieve crystal is used as a template to synthesize a highly oriented carbon nanotube, and the carbon nanotube is regularly distributed in a pore channel of the molecular sieve, so that the carbon nanotube saturable absorber is not easy to agglomerate, and meanwhile, the pore channel of the molecular sieve can protect the carbon nanotube, thereby effectively blocking the influence of air and water vapor on the carbon nanotube, improving the stability of the carbon nanotube saturable absorber, and greatly improving the optical damage threshold of the carbon nanotube saturable absorber by the coating and uniform distribution of the pore channel of the molecular sieve on the carbon nanotube. The modulation depth can be greatly changed through the change of the polarization state, so that the random switching of the running state of the pulse laser between Q modulation and mode locking is realized.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.