Azo surface relief grating doped with oxidized carbon nanotubes and preparation method thereof

Abstract

The present invention belongs to the fields of grating optical devices, carbon and azo functional materials, and advanced nano-processing technologies. It discloses an azo surface-relief grating optical device doped with oxidized carbon nanotubes and a method for preparing the same. Chemically prepared oxidized carbon nanotubes are then doped into an azo material solution at a specific ratio to form an azo film doped with oxidized carbon nanotubes. The oxidized carbon nanotube-doped azo surface-relief grating is then fabricated using linear interference polarized laser light. The oxidized carbon nanotube-doped azo surface-relief grating of the present invention is characterized by its high diffraction efficiency, compact size, light weight, and high degree of design freedom, as a typical micro-optical device. It has broad application prospects in optical imaging, optical data storage, laser technology, biomedicine, and other fields.

Description

Technical Field

[0001] The present invention belongs to the fields of grating optical devices, carbon and azo functional materials, and advanced nano-processing technology, and in particular relates to an azo surface relief grating doped with oxidized carbon nanotubes and a preparation method thereof, as well as applications thereof in optical imaging, optical data storage, laser technology, biomedicine, and other fields. Background Art

[0002] As a typical micro-diffraction optical device, grating has good application prospects in optical imaging, optical data storage, laser technology, biomedicine and other fields. With the development of modern optical systems, higher requirements are placed on the processing efficiency and preparation accuracy of diffraction optical elements, and it is hoped that the diffraction grating has high diffraction efficiency. At present, the technologies used to prepare grating diffraction optical devices include etching technology, grayscale mask method, single-point diamond turning technology, binary optical method, molding method, laser lithography, etc., but they all have different disadvantages. International Journal of Modern Physics B, 2017, 31, 1741004; International Journal of Advanced Manufacturing Technology, 2021, 117, 2545-2564 reported that dry and wet etching technologies have the disadvantages of high cost, low etching accuracy, poor accuracy and flexibility. Applied Optics, 1995, 34, 7507-7517 reported that the grayscale mask method has the disadvantages of being difficult to control and requiring high light source uniformity. Optics Express, 2003, 11, 191-198 reported that single-point diamond turning technology is limited in processing materials, surface shapes, and minimum dimensions, making it difficult to mass produce. The binary optical method has many processing steps, long cycles, and high costs. Applied Optics, 2010, 49, 6149-6159 reported that the molding method for preparing grating diffraction optical devices is difficult to meet the requirements of very fine optical structures. Optics & Laser Technology, 2022, 153, 108209 reported a non-contact, wear-free technology with high precision, high flexibility, and the ability to process complex contours, while also improving processing accuracy and diffraction efficiency. However, this technology is still a top-down strategy and has problems with processing materials, material loss, and environmental protection. Therefore, grating diffraction optical devices with high precision, high diffraction efficiency, economy, environmental protection, and mass production have attracted much attention from industry and academia.

[0003] Applied Physics Letters, 1995, 66, 1166-1168; Applied Physics Letters, 1995, 66, 136-138; Langmuir, 2008, 24, 2740-2745; Polymer, 2015, 60, 292-301 reported the fabrication of sinusoidal surface relief gratings on azo polymer films and azo molecular glass films by irradiating them with linear interference polarized lasers. These gratings exhibit high precision, high diffraction efficiency, are economical, environmentally friendly, highly efficient, and can be mass-produced. Wang Xiangxian et al. (Grant No. CN203149265U) have applied for a utility model patent for a lithography system for surface relief gratings on azo polymer films based on guided-mode interferometry. Unlike the aforementioned laser lithography method, this method requires low laser power and eliminates material loss, making it a green and environmentally friendly method for fabricating gratings. However, the most critical technology of this processing technology method lies in the molecular structure design, synthesis and modification of the azo material, so as to achieve surface relief gratings with higher diffraction efficiency, higher processing accuracy, shorter processing time, and greater freedom in period and height design, thereby meeting the needs of diffraction optical devices. Summary of the Invention

[0004] In response to the development of grating diffraction optical device processing technology and the problems existing in the existing technology, the present invention provides an oxidized carbon nanotube-enhanced azo surface relief grating and a preparation method thereof, and more particularly relates to a preparation method of an oxidized carbon nanotube-doped azo surface relief grating with high diffraction efficiency and high processing precision, and its application as a diffraction optical device in the fields of optical imaging, optical data storage, laser technology, biomedicine, etc.

[0005] The present invention is achieved by providing an azo surface relief grating doped with oxidized carbon nanotubes. The azo surface relief grating is based on an azo material and has an oxidized carbon nanotube doping content of 0.001-15wt%. The height of the azo surface relief grating doped with oxidized carbon nanotubes is 10-2000nm and the period is 600-50000nm.

[0006] Furthermore, when the azo surface relief grating is irradiated with a point light source of 633 nm wavelength and approximately perpendicular to the surface of the azo surface relief grating doped with oxidized carbon nanotubes, the diffraction efficiency of the first-order diffraction point is 4%-35%. Based on the azo surface relief grating with the same period and height, the diffraction efficiency of the first-order diffraction point of the azo surface relief grating doped with oxidized carbon nanotubes can be increased by 5%-200%.

[0007] Furthermore, the optical path system of the azo surface relief grating is as follows: linear interference polarized laser light of uniform intensity is used to irradiate the azo film doped with oxidized carbon nanotubes at a certain power and a certain incident angle.

[0008] Another object of the present invention is to provide a method for preparing the azo surface relief grating doped with oxidized carbon nanotubes, the method comprising: further, the wavelength of the linearly polarized laser is 488nm, the irradiation power is 30-300mW / cm 2 , the incident angle is 3°-20°, and the irradiation time is 0-60min.

[0009] Another object of the present invention is to provide a method for preparing the azo surface relief grating doped with oxidized carbon nanotubes, the method comprising: ultrasonically dispersing oxidized carbon nanotubes to prepare a dispersion having a certain weight ratio, mixing the oxidized carbon nanotube dispersion with an azo material to prepare a solution having a certain concentration; dropwise adding the azo material solution doped with oxidized carbon nanotubes onto a heated glass sheet, and preparing the azo film doped with oxidized carbon nanotubes by spin coating;

[0010] The concentration of the oxidized carbon nanotube dispersion is 0.01-10 wt %;

[0011] The concentration of the azo material solution doped with oxidized carbon nanotubes is 5-30 wt %;

[0012] The thickness of the azo film doped with oxidized carbon nanotubes is 1-20 μm;

[0013] The solvent for dispersing the oxidized carbon nanotubes and the solvent for the azo material solution doped with the oxidized carbon nanotubes is any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide;

[0014] The spin coating speed for preparing the azo film doped with oxidized carbon nanotubes is 300-2000 rpm.

[0015] Furthermore, the oxidized carbon nanotubes are prepared by chemical oxidation using multi-walled carbon nanotubes as raw materials, and the multi-walled carbon nanotubes have a length of 100-100000 nm and an outer diameter of 3-50 μm;

[0016] Furthermore, the multi-walled carbon nanotubes are reacted in a mixed acid of concentrated sulfuric acid and nitric acid in a volume ratio of 1:1-1:5 at a temperature of 50-100° C. for 6-48 hours, and then washed with water, filtered, and dried.

[0017] Furthermore, the atomic ratio of oxygen to carbon is 2%-8%.

[0018] Another object of the present invention is to provide an application of the azo surface relief grating doped with oxidized carbon nanotubes as an optical device in the fields of optical imaging, optical data storage, laser technology, biomedicine, etc.

[0019] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0020] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving these problems, this paper closely combines the technical solutions to be protected by the present invention and the results and data during the research and development process, and analyzes in detail and in depth how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about by solving the problems. The specific description is as follows:

[0021] The present invention belongs to the fields of grating optical devices, carbon and azo functional materials, and advanced nano-processing technology. It particularly relates to an azo surface relief grating doped with oxidized carbon nanotubes, a method for its preparation, and its applications in optical imaging, optical data storage, laser technology, biomedicine, and other fields. Azo materials are light-responsive functional materials containing azobenzene chromophores. Under irradiation conditions of a certain wavelength, the azobenzene chromophores undergo cis-trans isomerization, resulting in macroscopic mass migration. When linear interference polarized laser light is irradiated onto the surface of an azo film, a surface relief grating is formed. The grating diffraction optical device prepared by this method offers advantages such as cost-effectiveness, environmental friendliness, and wide design freedom for the grating period. However, its diffraction efficiency, processing accuracy, and grating height are all affected by the properties of the azo material. Although numerous studies have reported improving the optical writing speed, grating height, and diffraction efficiency of azo surface relief gratings through molecular structural design of azo materials, these improvements still fall short of meeting application requirements. The present invention utilizes high-refractive-index oxidized carbon nanotubes to dope and modify azo materials, and utilizes one-dimensional oxidized carbon nanotubes to orderly orient and arrange in an azo film matrix to form a phase grating. Through the processing and preparation technology of linear interference polarized laser irradiation of the oxidized carbon nanotube-doped azo film, the azo surface relief grating doped with oxidized carbon nanotubes and the preparation method thereof are realized.

[0022] In order to prepare an azo surface relief grating doped with oxidized carbon nanotubes with faster optical writing speed, larger grating height, greater diffraction efficiency and higher processing precision, the present invention provides an azo surface relief grating doped with oxidized carbon nanotubes and a preparation method thereof.

[0023] In order to prepare an oxidized carbon nanotube with better dispersion in an azo material and to obtain a higher processing precision of an azo surface relief grating doped with the oxidized carbon nanotube, the present invention provides an oxidized carbon nanotube and a preparation method thereof.

[0024] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0025] The present invention can prepare a grating device with high diffraction efficiency by adding one-dimensional oxidized carbon nanotubes with high refractive index to the grating device. At the same time, as part of the overall technical solution of the present invention, the present invention can prepare a surface relief grating with fast optical writing speed, large grating height, high diffraction efficiency, and high freedom in grating period design by optimizing and synthesizing suitable azo materials and utilizing linear interference polarized laser irradiation. First, by increasing the doping content of oxidized carbon nanotubes, the diffraction effect of the first-order diffraction point can be improved in the surface relief grating with the same grating height and grating period; second, by regulating the incident angle of the linear interference polarized laser, the period size of the oxidized carbon nanotube-doped azo surface relief grating can be regulated; finally, by regulating the laser power and irradiation time of the linear interference polarized laser, the grating height of the oxidized carbon nanotube-doped azo surface relief grating can be adjusted.

[0026] The present invention will establish a processing technology for preparing azo surface relief gratings based on interference polarized laser irradiation and functional modification of azo materials by oxidizing carbon nanotubes, thereby establishing a processing technology for preparing azo surface relief gratings with higher diffraction efficiency and higher processing precision.

[0027] The azo surface relief grating doped with oxidized carbon nanotubes provided by the present invention has higher diffraction efficiency when applied in the fields of optical imaging, optical data storage, laser technology, biomedicine, etc.

[0028] Third, as auxiliary evidence for the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0029] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0030] Grating optical devices have important applications in optical imaging, optical data storage, laser technology, biomedicine and other fields, but are limited by processing and preparation technology and low diffraction efficiency, and the commercial application of grating optical devices is very limited. The technology of using azo materials to prepare surface relief gratings is a technical solution with high efficiency and design freedom, but due to its low diffraction efficiency, there are currently few application cases of azo surface relief gratings as optical devices. The technical solution of the present invention will greatly improve the diffraction efficiency of azo surface relief gratings, and can replace grating devices prepared by traditional technologies such as etching technology, grayscale masking method, single-point diamond turning technology, binary optical method, molding method, laser lithography, etc. After the technical solution of the present invention is transformed, it will bring huge benefits to the fields of optical imaging, optical data storage, laser technology, biomedicine and so on.

[0031] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0032] The technical solution of the present invention prepares an azo surface relief grating by doping it with a highly refractive one-dimensional carbon nanotube material. By leveraging the high refractive index and ordered arrangement of the one-dimensional carbon nanotube material, the diffraction efficiency of the azo surface relief grating can be significantly improved. Currently, this technical solution represents a technological gap both domestically and internationally. Furthermore, the present invention improves the dispersibility of the carbon nanotube material in solution and in the azo surface relief grating by oxidative modification, thereby enhancing the stability of the carbon nanotube-doped azo surface relief grating device. More importantly, the present invention describes the oxidation process and degree of the carbon nanotubes, which are key components and innovations of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a scanning electron microscope photograph of the oxidized carbon nanotubes provided in Examples 1-10 of the present invention;

[0034] Figure 2 1 is an elemental analysis diagram of the oxidized carbon nanotubes and carbon nanotubes provided in Examples 1-10 of the present invention;

[0035] Figure 3 is a thermogravimetric analysis graph of oxidized carbon nanotubes and carbon nanotubes provided in Examples 1-10 of the present invention;

[0036] Figure 4 This is a stability analysis chart of the oxidized carbon nanotubes and the N,N-dimethylformamide dispersion of carbon nanotubes provided in Examples 1-10 of the present invention;

[0037] Figure 5 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 1 of the present invention;

[0038] Figure 6 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 2 of the present invention;

[0039] Figure 7 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 3 of the present invention;

[0040] Figure 8 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 4 of the present invention;

[0041] Figure 9 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 5 of the present invention;

[0042] Figure 10 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 6 of the present invention;

[0043] Figure 11 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 7 of the present invention;

[0044] Figure 12 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 8 of the present invention;

[0045] Figure 13 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 9 of the present invention;

[0046] Figure 14 This is an atomic force microscope photograph of the azo surface relief grating doped with oxidized carbon nanotubes provided in Example 10 of the present invention;

[0047] Figure 15 The optical path system provided by the embodiment of the present invention irradiates the azo film doped with oxidized carbon nanotubes with a linear interference polarized laser of uniform light intensity at a certain power and a certain incident angle.

[0048] In the figure: 1. Linearly polarized laser; 2. Azo film coated with oxidized carbon nanotubes; 3. Reflector; α is the angle between the laser propagation direction and the azo film, and β is 90 degrees. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0050] In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an explanatory embodiment that expands on the technical solutions of the claims.

[0051] An embodiment of the present invention provides an azo surface relief grating doped with oxidized carbon nanotubes. The azo surface relief grating is based on an azo material, and the weight percentage of the oxidized carbon nanotube doping content is 0.001-15wt%. The height of the azo surface relief grating doped with oxidized carbon nanotubes is 10-2000nm, and the period is 600-50000nm.

[0052] When the azo surface relief grating is irradiated with a point light source of 633 nm wavelength and approximately perpendicular to the surface of the azo surface relief grating doped with oxidized carbon nanotubes, the diffraction efficiency of the first-order diffraction point is 4%-35%. Based on azo surface relief gratings with the same period and height, the diffraction efficiency of the first-order diffraction point of the azo surface relief grating doped with oxidized carbon nanotubes can be increased by 5%-200%.

[0053] An embodiment of the present invention provides a method for preparing the azo surface relief grating doped with oxidized carbon nanotubes. The method for preparing the azo surface relief grating doped with oxidized carbon nanotubes includes: using an optical path system as shown in the figure, irradiating the azo film doped with oxidized carbon nanotubes with a linear interference polarized laser of uniform light intensity at a certain power and a certain incident angle.

[0054] like Figure 15 As shown, 1 is a linearly polarized laser, 2 is an azo film coated with doped oxidized carbon nanotubes, 3 is a reflector, α is the angle between the laser propagation direction and the azo film, β is 90 degrees, and 1 and 2 are perpendicular to each other.

[0055] The wavelength of the linearly polarized laser is 488 nm, and the irradiation power is 30-300 mW / cm 2 , the incident angle is 3°-20°, and the irradiation time is 0-60min.

[0056] An embodiment of the present invention provides a method for preparing an azo surface relief grating doped with oxidized carbon nanotubes. The method for preparing an azo film doped with oxidized carbon nanotubes comprises: ultrasonically dispersing oxidized carbon nanotubes to prepare a dispersion having a certain weight ratio; mixing the oxidized carbon nanotube dispersion with an azo material to prepare a solution having a certain concentration; dropwise adding the azo material solution doped with oxidized carbon nanotubes onto a heated glass sheet; and preparing an azo film doped with oxidized carbon nanotubes by spin coating.

[0057] The concentration of the oxidized carbon nanotube dispersion is 0.01-10 wt %;

[0058] The concentration of the azo material solution doped with oxidized carbon nanotubes is 5-30 wt %;

[0059] The thickness of the azo film doped with oxidized carbon nanotubes is 1-20 μm;

[0060] The solvent for dispersing the oxidized carbon nanotubes and the solvent for the azo material solution doped with the oxidized carbon nanotubes is any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide;

[0061] The spin coating speed for preparing the azo film doped with oxidized carbon nanotubes is 300-2000 rpm.

[0062] The oxidized carbon nanotubes are prepared by chemical oxidation using multi-walled carbon nanotubes as raw materials. The multi-walled carbon nanotubes have a length of 100-100000 nm and an outer diameter of 3-50 μm.

[0063] The multi-walled carbon nanotubes are reacted in a mixed acid of concentrated sulfuric acid and nitric acid in a volume ratio of 1:1-1:5 at a temperature of 50-100° C. for 6-48 hours, and then washed with water, filtered, and dried.

[0064] The atomic number ratio of oxygen to carbon is 2% to 8%.

[0065] In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the claimed technical solution on specific products or related technologies.

[0066] The embodiment of the present invention provides an application of the azo surface relief grating doped with oxidized carbon nanotubes as an optical device in the fields of optical imaging, optical data storage, laser technology, biomedicine, etc.

[0067] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware portion can be implemented using dedicated logic; the software portion can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. Those skilled in the art will understand that the above-mentioned devices and methods can be implemented using computer-executable instructions and / or contained in processor control code, for example, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, or can be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0068] The embodiments of the present invention have achieved some positive effects during the development or use process, and indeed have great advantages compared with the existing technology. The following content describes them in conjunction with data, charts, etc. of the experimental process.

[0069] The oxidized carbon nanotubes provided in the embodiment of the present invention are prepared by reacting multi-walled carbon nanotubes in a mixed acid of concentrated sulfuric acid and nitric acid (volume ratio of 1:1-1:5) at a temperature of 50-100°C for 6-48 hours, then washing, filtering and drying. The ratio of oxygen and carbon atoms in the prepared oxidized carbon nanotubes is 2%-8%. The specific operation steps are as follows: First, add carbon nanotubes (20g) with an outer diameter of 8-10nm and a length of 500-3000nm to a mixed acid of concentrated sulfuric acid (20mL) and nitric acid (60mL), react at 70 degrees for 12 hours, and finally wash, filter and dry to prepare oxidized carbon nanotubes. Figure 1As shown, the morphology of the oxidized carbon nanotubes prepared by the above scheme was characterized by scanning electron microscopy. The outer diameter of the oxidized carbon nanotubes was slightly increased, and the length was still within the range of 500-3000 nm. Figure 2 Through elemental analysis, it was characterized that the ratio of oxygen and carbon atoms in the oxidized carbon nanotubes prepared by the above scheme was 3.3%. Through the comparison of the peak intensity of the oxygen element, the peak intensity of the oxygen element of the oxidized carbon nanotubes was much larger than that of the carbon nanotubes, which proved that the scheme successfully carried out oxidative modification of the carbon nanotubes. Figure 3 Thermogravimetric analysis shows that the stability of the oxidized carbon nanotubes prepared by the above scheme is worse than that of carbon nanotubes. When the temperature is raised to 800°C, the residual mass percentages of the oxidized carbon nanotubes and carbon nanotubes are approximately 95% and 98% respectively. Figure 4 The stability of the oxidized carbon nanotubes and carbon nanotube N,N-dimethylformamide dispersions prepared by the above scheme was characterized by UV-visible absorption spectroscopy. The UV-visible absorbance of the oxidized carbon nanotubes and carbon nanotube dispersions with a mass concentration ratio of 5wt% decreased by about 5% and 45%, respectively, after standing for 2.5 hours, confirming that the oxidized carbon nanotube dispersion has better stability than the carbon nanotube dispersion.

[0070] Example 1

[0071] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). The inventors selected a fast-responsive azo molecular material (abbreviated as IAC-4, RSC Advances, 2016, 6, 64203-64207) that has been synthesized and reported by the inventors. Its molecular structure is shown in the figure:

[0072]

[0073] An IAC-4 solution in N,N-dimethylformamide was prepared with a concentration of 20 wt % and a doping ratio of 0.1 wt % oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at a rotation speed of 800 rpm.

[0074] The wavelength is 488nm and the power is 100mW / cm 2 The linear interference polarized laser was used to irradiate the IAC-4 film doped with oxidized carbon nanotubes at an incident angle of 8°. When the irradiation time was 50 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 5As shown, the average height and period of the surface relief grating are 280 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 15%, which is 98% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0075] Example 2

[0076] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a doping ratio of 0.05 wt% of the oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0077] The wavelength is 488nm and the power is 100mW / cm 2 The linear interference polarized laser was used to irradiate the IAC-4 film doped with oxidized carbon nanotubes at an incident angle of 8°. When the irradiation time was 50 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 6 As shown, the average height and period of the surface relief grating are 450 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 20%, which is 65% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0078] Example 3

[0079] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a doping ratio of 0.025 wt% of the oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0080] The wavelength is 488nm and the power is 100mW / cm 2 The linear interference polarized laser was used to irradiate the IAC-4 film doped with oxidized carbon nanotubes at an incident angle of 8°. When the irradiation time was 50 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 7As shown, the average height and period of the surface relief grating are 550 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 17%, which is 35% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0081] Example 4

[0082] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a 1 wt% doping ratio of oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0083] The wavelength is 488nm and the power is 100mW / cm 2 The linear interference polarized laser was used to irradiate the IAC-4 film doped with oxidized carbon nanotubes at an incident angle of 8°. When the irradiation time was 50 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 8 As shown, the average height and period of the surface relief grating are 120 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 12%, which is 187% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0084] Example 5

[0085] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a doping ratio of 0.1 wt% of the oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0086] The wavelength is 488nm and the power is 200mW / cm 2 The linear interference polarized laser was irradiated at an incident angle of 8° on the IAC-4 film doped with oxidized carbon nanotubes. When the irradiation time was 33 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 9As shown, the average height and period of the surface relief grating are 320 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 18%, which is 105% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0087] Example 6

[0088] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a doping ratio of 0.1 wt% of the oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0089] The wavelength is 488nm and the power is 50mW / cm 2 The linear interference polarized laser was irradiated at an incident angle of 8° on the IAC-4 film doped with oxidized carbon nanotubes. When the irradiation time was 60 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 10 As shown, the average height and period of the surface relief grating are 240 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 14%, which is 94% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0090] Example 7

[0091] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a doping ratio of 0.1 wt% of the oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0092] The wavelength is 488nm and the power is 100mW / cm 2 The linear interference polarized laser was irradiated at an incident angle of 10° on the IAC-4 film doped with oxidized carbon nanotubes. When the irradiation time was 25 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 11As shown, the average height and period of the surface relief grating are 260 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 28%, which is 78% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0093] Example 8

[0094] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A 20 wt% IAC-4 solution in N,N-dimethylformamide was prepared, with a doping ratio of 0.1 wt% of the oxidized carbon nanotubes. An IAC-4 film doped with oxidized carbon nanotubes was prepared by spin coating at 800 rpm.

[0095] The wavelength is 488nm and the power is 100mW / cm 2 The linear interference polarized laser was irradiated at an incident angle of 6° on the IAC-4 film doped with oxidized carbon nanotubes. When the irradiation time was 55 minutes, the diffraction efficiency of the first-order diffraction point of the IAC-4 surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the IAC-4 surface relief grating doped with oxidized carbon nanotubes was completed. Figure 12 As shown, the average height and period of the surface relief grating are 320 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 13%, which is 143% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0096] Example 9

[0097] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). A fast-responsive azo polymer material (abbreviated as CH-AZ-CA, Polymer, 2015, 60, 292-301) synthesized and reported by the inventors was selected. Its molecular structure is shown in the figure:

[0098]

[0099] A CH-AZ-CA solution in N,N-dimethylformamide was prepared with a concentration of 20 wt % and a doping ratio of 0.1 wt % oxidized carbon nanotubes. A CH-AZ-CA film doped with oxidized carbon nanotubes was prepared by spin coating at a rotation speed of 800 rpm.

[0100] The wavelength is 488nm and the power is 100mW / cm 2The linear interference polarized laser was used to irradiate the CH-AZ-CA film doped with oxidized carbon nanotubes at an incident angle of 8°. When the irradiation time was 55 minutes, the diffraction efficiency of the first-order diffraction point of the CH-AZ-CA surface relief grating doped with oxidized carbon nanotubes reached the maximum. At this time, the irradiation was stopped and the preparation of the CH-AZ-CA surface relief grating doped with oxidized carbon nanotubes was completed. Figure 13 As shown, the average height and period of the surface relief grating are 110 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 10%, which is 44% higher than the diffraction efficiency of the CH-AZ-CA surface relief grating with approximately the same height and period.

[0101] Example 10

[0102] Oxidized carbon nanotubes were prepared according to the above method and ultrasonically prepared into a 5 wt% dispersion (solvent: N,N-dimethylformamide). The azo polymer material (abbreviated as BP-AZ-CA, Polymer, 2015, 60, 292-301) previously synthesized by the inventors was selected, and its molecular structure is shown in the figure:

[0103]

[0104] A BP-AZ-CA solution in N,N-dimethylformamide was prepared with a concentration of 20 wt % and a doping ratio of 0.1 wt % oxidized carbon nanotubes. A BP-AZ-CA film doped with oxidized carbon nanotubes was prepared by spin coating at a rotation speed of 800 rpm.

[0105] The BP-AZ-CA film doped with oxidized carbon nanotubes was irradiated with a linear interference polarized laser of 488 nm and 100 mW / cm2 at an incident angle of 8°. When the irradiation time was 60 min, the diffraction efficiency of the first-order diffraction point of the BP-AZ-CA surface relief grating doped with oxidized carbon nanotubes reached its maximum. At this time, the irradiation was stopped and the preparation of the BP-AZ-CA surface relief grating doped with oxidized carbon nanotubes was completed. Figure 14 As shown, the average height and period of the surface relief grating are 90 nm and 1770 nm respectively, and the diffraction efficiency of the first-order diffraction point is 7%, which is 126% higher than the diffraction efficiency of the IAC-4 surface relief grating with approximately the same height and period.

[0106] Table 1. Size parameters of gratings and diffraction efficiency of first-order diffraction points in Examples 1-10

[0107]

[0108] Table 1 shows the dimensional parameters and diffraction efficiencies of the first-order diffraction points of the azo surface relief gratings doped with oxidized carbon nanotubes prepared in Examples 1-10. According to the formula d = λ / sin(2θ), the grating period is related to the wavelength and incident angle of the linearly polarized laser. At a certain wavelength, such as 488 nm, the grating period can be varied by adjusting the incident angle. In Example 1, the period and height of the oxidized carbon nanotube-doped IAC-4 surface relief grating were 1770 nm and 280 nm, respectively, and the diffraction efficiency of the first-order diffraction point reached 15%. Compared to an IAC-4 surface relief grating with the same period and height, this diffraction efficiency was enhanced by 98%. Compared to Example 1, the oxidized carbon nanotube content in Examples 2 and 3 was reduced to 0.05wt% and 0.025wt%, respectively. The grating heights were increased to 450nm and 550nm, respectively, and the diffraction efficiency of the first-order diffraction point increased to 20% and 17%, respectively. However, compared to an IAC-4 surface relief grating of the same period and height, the diffraction efficiency enhancement ratio decreased to 65% and 35%, respectively. This is because the increase in grating height increases the diffraction efficiency of the grating diffraction points. Meanwhile, in Example 4, the oxidized carbon nanotube content was increased to 1wt%. Compared to an IAC-4 surface relief grating of the same period and height, the diffraction efficiency of the first-order diffraction point increased by 187%. However, with a grating height of only 120nm, the diffraction efficiency of the first-order diffraction point decreased to 12%. These results indicate that there is an optimal range for the oxidized carbon nanotube doping content, balancing both the diffraction efficiency and enhancement ratio of the first-order diffraction point.

[0109] Compared to Example 1, the laser irradiation intensities in Examples 5 and 6 were 200 and 50 mW / cm², respectively. Light intensity affects the ease and speed of mass migration in the azo material. The greater the light intensity, the faster the mass migration of the azo material forms a grating, and the greater its height. Compared to Example 1, Examples 7 and 8 demonstrate how the period and height of the grating change when laser light is applied to the surface of an azo film doped with oxidized carbon nanotubes at an incident angle. The larger the incident angle, the smaller the grating period and the lower the period height. However, in Example 7, the reduction of the grating period to 1420 nm increases the diffraction efficiency of the first-order diffraction point; whereas, in Example 8, the increase of the grating period decreases the diffraction efficiency of the first-order diffraction point. Comparing Examples 1, 7, and 8, the diffraction efficiency of small-period surface-relief gratings doped with oxidized carbon nanotubes is relatively high. While the diffraction efficiency of large-period surface-relief gratings doped with oxidized carbon nanotubes is lower, the resulting increase in diffraction efficiency is even greater. These results address the application challenge of low diffraction efficiency for large-period azo surface-relief gratings.

[0110] Compared to Example 1, Examples 9 and 10 employed azo polymers CH-AZ-CA and BP-AZ-CA, respectively. The photoresponse speeds of CH-AZ-CA and BP-AZ-CA were slower than that of IAC-4. The grating heights in Examples 9 and 10 were 110 nm and 90 nm, respectively, and the diffraction efficiencies were 10% and 7%, respectively. Compared to CH-AZ-CA and BP-AZ-CA surface relief gratings of the same period and height, the diffraction efficiencies were enhanced by 44% and 126%, respectively.

[0111] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. An azo surface relief grating doped with oxidized carbon nanotubes, characterized in that: The azo surface relief grating is based on an azo material, and the weight percentage of the oxidized carbon nanotube doping content is 0.001-15wt%; the height of the azo surface relief grating doped with the oxidized carbon nanotube is 10-2000nm, and the period is 600-50000nm; When the azo surface relief grating is irradiated with a point light source of 633 nm wavelength and approximately perpendicular to the surface of the azo surface relief grating doped with oxidized carbon nanotubes, the diffraction efficiency of the first-order diffraction point is 4%-35%. Based on azo surface relief gratings with the same period and height, the diffraction efficiency of the first-order diffraction point of the azo surface relief grating doped with oxidized carbon nanotubes can be increased by 5%-200%.

2. A method for preparing an azo surface relief grating doped with oxidized carbon nanotubes as claimed in claim 1, characterized in that: By using high-refractive-index oxidized carbon nanotubes to dope modified azo materials, and using one-dimensional oxidized carbon nanotubes to orderly orient and arrange in an azo film matrix to form a phase grating, and through the processing and preparation technology of linear interference polarized laser irradiation of oxidized carbon nanotube-doped azo film, the azo surface relief grating doped with oxidized carbon nanotubes and its preparation method are realized.

3. The method for preparing an azo surface relief grating doped with oxidized carbon nanotubes according to claim 2, wherein: The wavelength of the linear interference polarized laser is 488 nm, and the irradiation power is 30-300 mW / cm 2 , the incident angle is 3°-20°, and the irradiation time is 0-60min.

4. The method for preparing an azo surface relief grating doped with oxidized carbon nanotubes according to claim 2, wherein: Specific methods include: The method comprises the following steps: ultrasonically dispersing oxidized carbon nanotubes to prepare a dispersion having a certain weight ratio; mixing the oxidized carbon nanotube dispersion with an azo material to prepare a solution having a certain concentration; dropping the azo material solution doped with oxidized carbon nanotubes onto a heated glass sheet; and preparing an azo film doped with oxidized carbon nanotubes by spin coating; The concentration of the oxidized carbon nanotube dispersion is 0.01-10 wt %; the concentration of the azo material solution doped with the oxidized carbon nanotubes is 5-30 wt %; the thickness of the azo film doped with the oxidized carbon nanotubes is 1-20 μm; the dispersion solvent for the oxidized carbon nanotubes and the solvent of the azo material solution doped with the oxidized carbon nanotubes are any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide; and the spin coating speed for preparing the azo film doped with the oxidized carbon nanotubes is 300-2000 rpm.

5. The method for preparing an azo surface relief grating doped with oxidized carbon nanotubes according to claim 2, wherein: The oxidized carbon nanotubes are prepared by chemical oxidation using multi-walled carbon nanotubes as raw materials. The length of the multi-walled carbon nanotubes is 100-100000 nm and the outer diameter is 3-50 μm.

6. The method for preparing an azo surface relief grating doped with oxidized carbon nanotubes according to claim 5, wherein: The multi-walled carbon nanotubes are reacted in a mixed acid of concentrated sulfuric acid and nitric acid in a volume ratio of 1:1-1:5 at a temperature of 50-100° C. for 6-48 hours, and then washed with water, filtered, and dried.

7. The method for preparing an azo surface relief grating doped with oxidized carbon nanotubes according to claim 2, wherein: In the oxidized carbon nanotubes, the atomic ratio of oxygen to carbon is 2%-8%.

8. Application of the azo surface relief grating doped with oxidized carbon nanotubes as claimed in claim 1 as an optical device in the fields of optical imaging, optical data storage, laser technology, and biomedicine.

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