CN109406043B - Tubular waveguide grating sensor and preparation method thereof - Google Patents
Tubular waveguide grating sensor and preparation method thereof Download PDFInfo
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- CN109406043B CN109406043B CN201811282651.9A CN201811282651A CN109406043B CN 109406043 B CN109406043 B CN 109406043B CN 201811282651 A CN201811282651 A CN 201811282651A CN 109406043 B CN109406043 B CN 109406043B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
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Abstract
The invention provides a tubular waveguide grating sensor, comprising: the tubular waveguide is provided with an air outlet and an air inlet, and the air outlet and the air inlet are respectively arranged on the pipe walls at two ends of the tubular waveguide; the double-groove type grating part is arranged on the pipe wall of the tubular waveguide; the sealing parts are arranged at two ends of the tubular waveguide, wherein the double-groove type grating part comprises a first double-groove type grating unit, a second double-groove type grating unit and a third double-groove type grating unit, and the first double-groove type grating unit is arranged at one end, close to the air inlet, of the tubular waveguide; the third double-groove type grating unit is arranged at one end of the tubular waveguide close to the air outlet; the second double-groove-type grating unit is arranged between the first double-groove-type grating unit and the second double-groove-type grating unit. The tubular waveguide can realize the pressure detection of various gases under the condition of terahertz wave incidence, and in addition, the arrangement of the three double-groove type grating units can improve the sensitivity of the terahertz wave in detecting the gas pressure.
Description
Technical Field
The invention relates to the field of terahertz waves, in particular to a tubular waveguide grating sensor and a preparation method thereof.
Background
Terahertz waves refer to a very unique set of electromagnetic waves with frequencies between 0.1 and 10 THz. They are widely studied in the field of optoelectronics, since they lie in the electromagnetic spectrum between the microwave, millimeter wave and infrared. The terahertz wave-front technology is that the amplitude time waveform of a terahertz radiation electric field is directly recorded by utilizing an electro-optic sampling or photoconductive sampling method, and then spectral information of the amplitude and phase of a measurement signal is obtained after Fourier transform, so that the information of absorption, dispersion and the like of a sample in a terahertz wave band is obtained. Terahertz energy has a special effect on many materials, so that the terahertz energy is widely applied to the research of the characteristics of gas, liquid, solid and other media, and is also suitable for the fields of communication, biomedicine, nondestructive detection, environmental detection and the like.
Among them, the detection important in the environmental detection is gas detection. However, most of the existing devices for detecting the characteristics of the gas have the problems of low sensitivity, complex device and high cost.
Disclosure of Invention
The present invention is made to solve the above problems, and an object of the present invention is to provide a tubular waveguide grating sensor and a method for manufacturing the same.
The present invention provides a tubular waveguide grating sensor for detecting gas pressure characteristics, having the characteristics comprising: the tubular waveguide is provided with an air outlet and an air inlet, and the air outlet and the air inlet are respectively arranged on the pipe walls at two ends of the tubular waveguide; the double-groove type grating part is arranged on the pipe wall of the tubular waveguide; the sealing parts are arranged at two ends of the tubular waveguide, wherein the double-groove type grating part comprises a first double-groove type grating unit, a second double-groove type grating unit and a third double-groove type grating unit, and the first double-groove type grating unit is arranged at one end, close to the air inlet, of the tubular waveguide; the third double-groove type grating unit is arranged at one end of the tubular waveguide close to the air outlet; the second double-groove-type grating unit is arranged between the first double-groove-type grating unit and the third double-groove-type grating unit.
The tubular waveguide can realize the pressure detection of various gases under the condition of terahertz wave incidence, and in addition, the arrangement of the three double-groove type grating units can improve the sensitivity of the terahertz wave in detecting the gas pressure. Furthermore, the cost of the tubular waveguide grating sensor is relatively low.
In the tubular waveguide grating sensor provided by the present invention, the following features may also be provided: the first double-groove type grating unit consists of 26 double-groove type gratings with the period of 700 mu m, each double-groove type grating consists of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 150 mu m.
In the tubular waveguide grating sensor provided by the present invention, the following features may also be provided: the second double-groove type grating unit consists of 26 double-groove type gratings with the period of 700 mu m, each double-groove type grating consists of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 100 mu m.
In the tubular waveguide grating sensor provided by the present invention, the following features may also be provided: the third double-groove type grating unit consists of 26 double-groove type gratings with the period of 700 mu m, each double-groove type grating consists of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 50 mu m.
The first double-groove type grating unit, the second double-groove type grating unit and the third double-groove type grating unit are sequentially arranged on the tubular waveguide, and according to the etching depth, the arrangement of the first double-groove type grating unit, the second double-groove type grating unit and the third double-groove type grating unit is sequentially arranged in a step-shaped manner in a descending manner. The three double-groove grating units arranged in the ladder shape can cause local field enhancement, and the sensitivity of detecting the gas pressure by the terahertz waves is improved.
In the tubular waveguide grating sensor provided by the present invention, the following features may also be provided: wherein, the sealing element is a polytetrafluoroethylene sheet. The polytetrafluoroethylene sheet can seal the tubular waveguide, and gas is prevented from leaking.
The invention also provides a preparation method of the tubular waveguide grating sensor, which is characterized by comprising the following steps: etching a first double-groove type grating unit, a second double-groove type grating unit and a third double-groove type grating unit which are distributed in a step shape on the surface of a tubular waveguide by using a femtosecond laser direct writing technology; respectively drilling small holes at two ends of the tubular waveguide etched with the three double-groove grating unit structures by using an electric drill; thirdly, mounting ventilation pipelines in the two small holes; and step four, covering polytetrafluoroethylene sheets at two ends of the tubular waveguide respectively to obtain a tubular waveguide grating sensor, wherein the tubular waveguide sensor is the tubular waveguide grating sensor. The tubular waveguide grating sensor prepared by the preparation method can improve the sensitivity of effectively detecting the gas pressure. In addition, the preparation method utilizes the femtosecond laser direct writing technology to etch the double-groove type grating units on the tubular waveguide, and can accurately etch the three double-groove type grating units on the tubular waveguide in a step shape.
In the method for preparing the tubular waveguide grating sensor provided by the invention, the method can also have the following characteristics: wherein, the thickness of the polytetrafluoroethylene sheet is 0.5mm, and the length is 10 mm. The polytetrafluoroethylene can effectively seal the gas to be detected in the tubular waveguide from leaking outwards, so that the problem that the detection result has errors due to the gas leaking outwards is solved.
Drawings
FIG. 1 is a cross-sectional view of a tubular waveguide grating sensor in an embodiment of the present invention;
FIG. 2 is an apparatus diagram of a femtosecond laser direct writing system in a manufacturing method in an embodiment of the present invention;
FIG. 3 is a graph showing the effective refractive index of a tubular waveguide with and without a double-groove grating versus the frequency of a terahertz wave, respectively, in an embodiment of the present invention;
FIG. 4 is a graph of the effective refractive index of a tubular waveguide grating sensor versus the frequency of terahertz waves at different pressures in an embodiment of the present invention;
FIG. 5 is a diagram showing the intensity distribution of the fundamental mode of the tubular waveguide grating sensor of the present invention at a frequency of 260 GHz.
Detailed Description
In order to make the technical means, creation features, achievement objects and effects of the present invention easy to understand, the following embodiments are specifically described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view of a tubular waveguide grating sensor in an embodiment of the present invention.
As shown in fig. 1, a tubular waveguide grating sensor 100 for detecting the pressure of a gas includes: a tubular waveguide 10, a double-groove grating portion 20, and a sealing member 30.
The tubular waveguide 10 is made of a polymethylmethacrylate material and has an outer diameter of 7mm, a thickness of 1mm and a length of 70 mm. The tubular waveguide 10 is provided at both ends thereof with an air inlet 11 and an air outlet 12, respectively. The gas to be measured is input and output through pipes installed on the gas inlet 11 and the gas outlet 12.
The double-groove type grating part 20 is arranged on the tube wall of the tubular waveguide 10 and comprises a first double-groove type grating unit 21, a second double-groove type grating unit 22 and a third double-groove type grating unit 23.
A first double-groove grating 21 is arranged on the tubular waveguide 10 near the gas inlet 11. The first double-groove grating 21 consists of 26 double-groove gratings with a period of 700 μm. Each double-groove grating is composed of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 150 mu m.
The second double groove type grating unit 22 is disposed on a side of the first double groove type grating 21 away from the air inlet 11. The second double-groove grating 22 is composed of 26 double-groove gratings having a period of 700 μm. Each double-groove grating is composed of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 100 mu m.
A third double-groove grating 23 is arranged on the tubular waveguide 10 near the outlet 12. The third double-groove grating 23 consists of 26 double-groove gratings with a period of 700 μm. Each double-groove grating is composed of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 50 mu m.
The etching groove interface of the double-groove type grating structure in each double-groove type grating unit is rectangular.
The seal 30 comprises two sheets 31 of polytetrafluoroethylene. The polytetrafluoroethylene sheet 31 had a thickness of 0.5mm and a length and width of 10 mm. Two teflon sheets 31 are respectively disposed at both ends of the tubular waveguide for sealing the tubular waveguide 10.
Fig. 2 is a flow chart of an apparatus for a picosecond laser in a fabrication process according to an embodiment of the present invention.
In this embodiment, the method for manufacturing the tubular waveguide grating sensor 100 mainly includes the following steps:
step one, etching the double-groove type grating unit 20 on the tubular waveguide 10 by using a nanosecond laser direct writing technology.
The femtosecond laser device and the process thereof are shown in fig. 2, a one-dimensional platform 6 is fixed on an optical platform, and an optical bread board 5 with the width of 20 cm, the length of 30 cm and the thickness of 10mm is placed on the one-dimensional platform.
First, the tubular waveguide 10, which is cleaned and dried, is fixed to the stepping motor 3 and the manual displacement table 4 with bearings.
Then, the femtosecond laser 1 outputs a parallel femtosecond laser beam 7 to the laser galvanometer 2; the femtosecond laser beam 7 which is incident in parallel is shaped into a line beam 8 through the laser galvanometer 2. The line beam 8 emerging from the laser galvanometer 2 is focused onto the surface area of the tubular waveguide 10 to be machined.
And then, driving the one-dimensional displacement platform 6 to move by controlling the compiled control program, and rapidly and accurately processing 78 double-groove type grating structures in total on the tubular waveguide 10 by combining the femtosecond laser and the precise displacement platform, wherein the first double-groove type grating unit 21, the second double-groove type grating unit 22 and the third double-groove type grating unit 23 are formed.
Fixing the tubular waveguide 10 with the double-groove grating structure on a drilling platform, and accurately communicating two small holes at the positions without the double-grating period at the two ends of the tubular waveguide 10 by using a precision electric drill.
And step three, installing pipelines in the two small holes to serve as an air inlet 11 and an air outlet 12 of the tubular waveguide grating sensor 100.
And step four, fixing two polytetrafluoroethylene sheets 31 at two ends of the tubular waveguide 10, and sealing the tubular waveguide 10 to obtain the tubular waveguide grating sensor 100.
The end of the tubular waveguide grating sensor 100 close to the gas inlet 11 is an incident end, and the end close to the gas outlet 12 is an emergent end. The terahertz wave is vertically incident to the tubular waveguide incident end. The terahertz wave is transmitted along the tubular waveguide and is emitted out from the emergent end of the tubular waveguide.
In this embodiment, the effective refractive index of the tubular waveguide grating sensor with the no grating structure and the tubular waveguide grating sensor 100 of this embodiment are simulated by using simulation software based on a frequency domain finite difference method under different nitrogen pressures.
Fig. 3 is a graph showing the change of the effective refractive index of the tubular waveguide with and without the double-groove grating to the frequency of the terahertz wave, respectively, in the embodiment of the present invention.
As shown in fig. 3, the resonance frequency points of the tubular waveguide sensor of the mat-grating structure and the tubular waveguide grating sensor 100 are 240GHz and 260GHz, respectively. The corresponding effective indices are 0.9743 and 0.98, respectively.
FIG. 4 is a graph of the effective refractive index of a tubular waveguide grating sensor versus the frequency of terahertz waves at different pressures in an embodiment of the present invention.
The change curve graphs of the tubular waveguide grating sensor 100 to the terahertz wave frequency under the nitrogen pressure of 0.1MPa, 0.3MPa, 0.6MPa, 0.9MPa, 1.2MPa and 1.5MPa are respectively simulated by using a frequency domain finite difference method.
As shown in fig. 4, under different nitrogen pressures, the resonant frequency points of the tubular waveguide grating sensor 100 are all at 260GHz, and the corresponding effective refractive indexes are 0.98, 0.9803, 0.9807, 0.9811, 0.9815 and 0.9819, respectively.
FIG. 5 is a diagram showing the intensity distribution of the fundamental mode of the tubular waveguide grating sensor of the present invention at a frequency of 260 GHz.
As shown in fig. 5, it can be seen from the intensity distribution of the fundamental mode at the frequency point of 260 GHz. The mode in the center of the tube dominates because the cladding material is more absorbent than the center of the tube.
Hereinbefore, specific embodiments of the present invention are described with reference to the drawings. However, those skilled in the art will appreciate that various modifications and substitutions can be made to the specific embodiments of the present invention without departing from the spirit and scope of the invention, which is defined by the appended claims.
Claims (7)
1. A tubular waveguide grating sensor for sensing gas pressure characteristics, comprising:
the tubular waveguide is provided with an air outlet and an air inlet, and the air outlet and the air inlet are respectively arranged on the pipe walls at two ends of the tubular waveguide;
the double-groove type grating part is arranged on the pipe wall of the tubular waveguide;
a sealing member disposed at both ends of the tubular waveguide,
wherein the double-groove type grating part comprises a first double-groove type grating unit, a second double-groove type grating unit and a third double-groove type grating unit,
the first double-groove type grating unit is arranged at one end of the tubular waveguide close to the air inlet;
the third double-groove type grating unit is arranged at one end of the tubular waveguide close to the gas outlet;
the second double-groove type grating unit is arranged between the first double-groove type grating unit and the second double-groove type grating unit,
the etching depths of the first double-groove-shaped grating unit, the second double-groove-shaped grating unit and the third double-groove-shaped grating unit are sequentially arranged in a descending manner in a step shape.
2. The tubular waveguide grating sensor of claim 1, wherein:
the first double-groove type grating unit consists of 26 double-groove type gratings with the period of 700 mu m, each double-groove type grating consists of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 150 mu m.
3. The tubular waveguide grating sensor of claim 1, wherein:
the second double-groove type grating unit consists of 26 double-groove type gratings with the period of 700 mu m, each double-groove type grating consists of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 100 mu m.
4. The tubular waveguide grating sensor of claim 1, wherein:
the third double-groove type grating unit consists of 26 double-groove type gratings with the period of 700 mu m, each double-groove type grating consists of air grooves with the same etching width and the distance of 100 mu m, the etching width of each air groove is 200 mu m, and the etching depth is 50 mu m.
5. The tubular waveguide grating sensor of claim 1, wherein:
wherein the sealing element is a polytetrafluoroethylene sheet.
6. A method of making a tubular waveguide grating sensor comprising the steps of:
etching a first double-groove type grating unit, a second double-groove type grating unit and a third double-groove type grating unit which are distributed in a step shape on the surface of a tubular waveguide by using a femtosecond laser direct writing technology;
respectively drilling small holes at two ends of the tubular waveguide etched with the three double-groove grating unit structures by using an electric drill;
thirdly, mounting ventilation pipelines in the two small holes;
step four, covering polytetrafluoroethylene sheets at two ends of the tubular waveguide respectively to obtain the tubular waveguide grating sensor,
the tubular waveguide grating sensor is the tubular waveguide grating sensor as claimed in any one of claims 1 to 5.
7. The method of manufacturing a tubular waveguide grating sensor of claim 6, wherein:
wherein, the thickness of the polytetrafluoroethylene sheet is 0.5mm, and the length is 10 mm.
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| CN110244393B (en) * | 2019-06-17 | 2021-01-29 | 杭州光粒科技有限公司 | Method for manufacturing AR (augmented reality) glasses waveguide based on superstructure relief grating |
| CN112067576B (en) * | 2020-08-18 | 2023-04-28 | 上海理工大学 | Composite waveguide gas sensor based on hollow PMMA (polymethyl methacrylate) tube |
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