Microporous array grating temperature and pressure sensor and preparation method and test calibration method thereof

Abstract

A micropore array grating temperature and pressure sensor disclosed by the present invention comprises an optical waveguide, a micropore array grating and a microcavity array grating, an optical transmission channel is arranged in the optical waveguide, and the micropore array grating and the microcavity array grating are formed in the optical transmission channel of the optical waveguide in parallel. The micropore array grating is communicated with the external environment, and the microcavity array grating is isolated from the external environment. The micropore array grating temperature and pressure sensor can avoid mutual influence of environment temperature and environment pressure during measurement so as to realize simultaneous measurement of different environment temperatures and different environment pressures. The invention also provides a preparation method and a test calibration method of the micropore array grating temperature and pressure sensor.

Description

Technical Field

[0001] The invention relates to grating sensing technology, and in particular to a micro-hole array grating temperature and pressure sensor and a preparation method and a test and calibration method thereof. Background Art

[0002] Real-time in-situ measurement of high-temperature multi-parameters (temperature, pressure, strain, vibration) is of great significance in promoting the solution of the "bottleneck" problem in the development of major equipment such as hypersonic aircraft, aircraft engines, gas turbines, shock tunnels, etc. in my country. In terms of high-temperature pressure measurement, the main electronic high-temperature pressure sensor can achieve stable and reliable pressure measurement by detecting changes in sensor parameters such as capacitance and resistance. However, due to the high-temperature resistance of electronic components, existing electronic sensors cannot achieve high-temperature pressure measurement.

[0003] The current fiber-optic high-temperature pressure sensor mainly measures pressure based on the fiber Fabry-Perot interferometer (FPI), and its structure is a diaphragm-fiber end face type. This structure combines the pressure-sensitive diaphragm with the fiber end face through gluing or welding to form a pressure sensing head, and the fiber serves as the optical signal transmission carrier. This structure has the problem that the pressure-sensitive diaphragm is easy to fall off and loosen under high-temperature operation, and it is difficult to achieve quasi-distributed measurement.

[0004] A microhole array grating is a fiber grating formed by making a microhole array inside an optical fiber that is connected to the external environment. Since the microhole array is connected to the external environment, the air medium in the microhole array can flow freely with the air medium in the external environment. When the air refractive index of the external environment changes, the air refractive index of the microhole array also changes by the same amount, thereby causing the effective refractive index of the microhole array grating to change. By demodulating the reflection peak wavelength of the microhole array grating, the air refractive index of the external environment can be measured; however, the air refractive index is affected by both ambient temperature and ambient pressure. When the microhole array grating is used as a temperature sensor, the ambient pressure needs to be controlled to be constant to avoid the air refractive index being affected by changes in ambient pressure, thereby affecting the measurement accuracy of the ambient temperature. Similarly, when the microhole array grating is used as a pressure sensor, the ambient temperature needs to be controlled to be constant to avoid the air refractive index being affected by changes in ambient temperature, thereby affecting the measurement accuracy of the ambient pressure.

[0005] From the above, it can be seen that when the microhole array grating is used as one of the temperature sensors or pressure sensors, it is necessary to control another environmental parameter to be constant, and the requirements for the measurement environment are very stringent. At present, the microhole array grating can only measure the ambient temperature or ambient pressure by keeping another environmental parameter constant in the laboratory. In actual applications, it is almost impossible to measure the ambient temperature or ambient pressure by the microhole array grating by keeping another environmental parameter constant. Summary of the invention

[0006] In order to solve the above-mentioned deficiencies of the prior art, the present invention provides a micro-hole array grating temperature and pressure sensor, which can avoid the mutual influence of ambient temperature and ambient pressure during measurement, so as to achieve simultaneous measurement of different ambient temperatures and different ambient pressures.

[0007] The present invention also provides a preparation method and a test calibration method for the microhole array grating temperature and pressure sensor.

[0008] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0009] A microhole array grating temperature and pressure sensor comprises an optical waveguide, a microhole array grating and a microcavity array grating. The optical waveguide has an optical transmission channel inside. The microhole array grating and the microcavity array grating are formed in parallel in the optical transmission channel of the optical waveguide. The microhole array grating is connected to the external environment, and the microcavity array grating is isolated from the external environment.

[0010] Furthermore, the optical waveguide is an integrated optical waveguide or a cylindrical optical waveguide, and its waveguide material is glass, sapphire, lutetium oxide or ceramic; wherein the integrated optical waveguide includes a planar (thin film) dielectric optical waveguide and a strip dielectric optical waveguide, and the cylindrical optical waveguide includes an optical fiber.

[0011] Furthermore, the microhole array grating includes a plurality of open microholes, each of which is distributed along the light transmission direction of the optical waveguide and is connected to the external environment.

[0012] Furthermore, the microcavity array grating includes a plurality of closed microcavities, each of which is distributed along the light transmission direction of the optical waveguide and isolated from the external environment.

[0013] Furthermore, the closed microcavity is formed by inducing a local refractive index change in the internal medium of the optical waveguide, and this part of the internal medium is completely ablated or the refractive index changes permanently; the closed microcavity is a hollow microcavity, the interior of which is a vacuum, air or a vaporized medium material, or the closed microcavity is a solid microcavity, the interior of which is a medium material with a changed refractive index.

[0014] Furthermore, the microhole array grating has a first central wavelength, and the microcavity array grating has a second central wavelength.

[0015] Furthermore, the ambient pressure P and the air refractive index n sensed by the microhole array grating tp and the ambient temperature t sensed by the microcavity array grating, satisfying the following formula:

[0016]

[0017] n s ×10 -8 =8342.54+2406147×[130-σ 2 ] -1 +15998×[38.9-σ 2 ] -1

[0018] The above formula is the dispersion formula of standard dry air, n s is the mantissa of the refractive index of air under standard conditions, and σ is the wave number.

[0019] The method for preparing the microhole array grating temperature and pressure sensor comprises the following steps:

[0020] Step 100: designing structural parameters of the microhole array grating and the microcavity array grating respectively;

[0021] Step 200: using a femtosecond laser to sequentially write the microhole array grating and the microcavity array grating in the optical transmission channel of the optical waveguide to obtain the microhole array grating temperature and pressure sensor.

[0022] Furthermore, after step 200, the following steps are also included:

[0023] Step 300: using an etching solution to etch the microhole array grating.

[0024] Furthermore, after step 300, the following steps are also included:

[0025] Step 400: performing high temperature annealing on the microhole array grating temperature and pressure sensor.

[0026] Furthermore, in step 200, the steps of sequentially writing the microhole array grating and the microcavity array grating in the optical transmission channel of the optical waveguide using a femtosecond laser are as follows:

[0027] Step 210: Build a femtosecond laser writing system, the femtosecond laser writing system includes an optical subsystem and a motion subsystem, the optical subsystem is used to shape the femtosecond laser, and the motion subsystem is used to drive the optical waveguide to move; the optical subsystem includes a femtosecond laser, a power attenuator, a polarization controller, a mechanical shutter, a beam splitter, a Michelson interferometer, a spatial light modulator, a focusing lens, a dichroic mirror, a focusing objective lens and a CCD camera, the Michelson interferometer has a first interference arm and a second interference arm, the first interference arm includes a first reflector, the second interference arm includes a second reflector and a one-dimensional A displacement platform; wherein the femtosecond laser, power attenuator, polarization controller, mechanical shutter, beam splitter, spatial light modulator, focusing lens, dichroic mirror and focusing objective are sequentially arranged along the propagation path of the femtosecond laser, the first reflector and the second reflector of the Michelson interferometer are respectively arranged on the two splitting paths of the beam splitter, and the CCD camera is located on the side of the dichroic mirror facing away from the focusing objective; the motion subsystem includes a rotating fixture, a six-axis pitch platform and a precision displacement platform, the rotating fixture is arranged on the six-axis pitch platform, and the six-axis pitch platform is arranged on the precision displacement platform;

[0028] Step 220: clamping and fixing the optical waveguide on the rotating fixture;

[0029] Step 230: Loading the required axicon phase diagram into the spatial light modulator;

[0030] Step 240: controlling the femtosecond laser to emit a single-pulse femtosecond laser, so that the single-pulse femtosecond laser forms a double-pulse Bessel beam after being shaped by the Michelson interferometer and the spatial light modulator, and focusing the double-pulse Bessel beam in the optical transmission channel of the optical waveguide;

[0031] Step 250: driving the rotating fixture to pitch and displace via the six-axis pitch platform and the precision displacement platform, thereby adjusting the writing posture of the optical waveguide, so that the double-pulse Bessel light beam writes and forms the microhole array grating in the optical transmission channel of the optical waveguide;

[0032] Step 260: shielding the first interference arm or the second interference arm of the Michelson interferometer, and not loading any axicon phase diagram in the spatial light modulator;

[0033] Step 270: Control the femtosecond laser to emit the single-pulse femtosecond laser again, and focus the single-pulse femtosecond laser in the optical transmission channel of the optical waveguide;

[0034] Step 280: The rotating fixture is driven to pitch and displace by the six-axis pitch platform and the precision displacement platform, thereby adjusting the writing posture of the optical waveguide so that the single-pulse femtosecond laser writes in the optical transmission channel of the optical waveguide to form the microcavity array grating.

[0035] The test and calibration method of the micro-hole array grating temperature and pressure sensor comprises the following steps:

[0036] Step S1: Under a normal pressure environment P0, the microhole array grating temperature pressure sensor is placed in different temperature environments to obtain the first reflection peak wavelength of the microhole array grating in different temperature environments and the second reflection peak wavelength of the microcavity array grating at different temperatures, and the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating under normal pressure P0 and the ambient temperature-second reflection peak wavelength response relationship of the microcavity array grating are respectively fitted;

[0037] Step S2: placing the microhole array grating temperature pressure sensor in different pressure environments under different temperature environments, and obtaining the first reflection peak wavelength of the microhole array grating in different pressure environments, and fitting the ambient pressure-first reflection peak wavelength response relationship and pressure sensitivity of the microhole array grating in different temperature environments respectively;

[0038] Step S3: placing the microcavity array grating temperature pressure sensor in a calibration environment, and calculating the ambient temperature T1 of the calibration environment according to the second reflection peak wavelength of the microcavity array grating in the calibration environment and the ambient temperature-second reflection peak wavelength response relationship;

[0039] Step S4: Calculate the total wavelength drift Δλ of the microhole array grating when it changes from a normal temperature and pressure environment to the calibration environment according to the ambient pressure-first reflection peak wavelength response relationship of the microhole array grating under different temperature environments, and calculate the wavelength drift component Δλ caused by the ambient temperature change when the microhole array grating changes from a normal temperature and pressure environment to the calibration environment according to the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating under the normal pressure environment P0. T , then the total wavelength shift Δλ of the microhole array grating is subtracted from its wavelength shift component Δλ T , the wavelength drift component Δλ caused by the change of the ambient pressure when the microhole array grating changes from the normal temperature and pressure environment to the calibration environment is obtained p ;

[0040] Step S5: Calculate the ambient pressure of the calibration environment P = P0 + Δλ P / S P,T1 , where SP,T1 is the pressure sensitivity of the microhole array grating at ambient temperature T1.

[0041] The present invention has the following beneficial effects: the present invention prepares the microhole array grating and the microcavity array grating in the optical waveguide at the same time, and the microhole array grating and the microcavity array grating can respectively sense the air refractive index and the ambient temperature of the external environment, and finally calculate the ambient pressure according to the air refractive index and the ambient temperature of the external environment. When sensing the ambient temperature, the microcavity array grating is not affected by the ambient pressure, and when sensing the ambient pressure, the microhole array grating can calculate the ambient pressure using the ambient temperature detected by the microcavity array grating, thereby avoiding the mutual influence of the ambient temperature and the ambient pressure during measurement, and realizing the simultaneous sensing of different ambient temperatures and different ambient pressures, and having the advantages of high reliability, high sensitivity, and easy serial multiplexing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of a radial cross section of the microhole array grating temperature and pressure sensor provided by the present invention.

[0043] Figure 2 for Figure 1 Schematic diagram of the axial cross section of the microhole array grating temperature and pressure sensor shown.

[0044] Figure 3 A radial cross-sectional schematic diagram of another microhole array grating temperature and pressure sensor provided by the present invention.

[0045] Figure 4 for Figure 3 Schematic diagram of the axial cross section of the microhole array grating temperature and pressure sensor shown.

[0046] Figure 5 This is a system schematic diagram of the femtosecond laser writing system provided by the present invention.

[0047] Figure 6 A flowchart of the steps of the method for preparing the microhole array grating temperature and pressure sensor provided by the present invention.

[0048] Figure 7 This is a block diagram of the steps of step 200 in the method for preparing the microhole array grating temperature and pressure sensor provided by the present invention.

[0049] Figure 8 This is a block diagram of the steps of step 300 in the method for preparing the microhole array grating temperature and pressure sensor provided by the present invention.

[0050] Fig. 9 A flowchart of the steps of the test and calibration method of the microhole array grating temperature and pressure sensor provided by the present invention. DETAILED DESCRIPTION

[0051] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments, examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0052] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0053] In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0054] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix", "set" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] Embodiment 1

[0056] like Figure 1-4 As shown, a microhole array grating temperature and pressure sensor includes an optical waveguide 110, a microhole array grating 120, and a microcavity array grating 130. The optical waveguide 110 has an optical transmission channel inside. The microhole array grating 120 and the microcavity array grating 130 are formed in parallel in the optical transmission channel of the optical waveguide 110. The microhole array grating 120 is connected to the external environment, and the microcavity array grating 130 is isolated from the external environment.

[0057] During sensing, the detection light signal is coupled into the light transmission channel of the optical waveguide 110, and then the reflected light signal reflected by the microhole array grating 120 and the microcavity array grating 130 is received to obtain the reflection spectrum of the reflected light signal; since the microhole array grating 120 and the microcavity array grating 130 have different central wavelengths, they can reflect back the different wavelength parts of the detection light signal, so the reflection spectrum has a first reflection peak corresponding to the microhole array grating 120 and a second reflection peak corresponding to the microcavity array grating 130; since the microhole array grating 120 is connected to the external environment, the air medium inside it can flow freely with the air medium of the external environment, so the effective refractive index of the microhole array grating 120 is the same as the refractive index of the air in the external environment and is affected by the environmental pressure and the environment. The influence of temperature, when the air refractive index of the external environment changes, the effective refractive index of the microhole array grating 120 also changes, thereby causing the wavelength drift of the first reflection peak, and the air refractive index of the external environment can be obtained by wavelength demodulating the first reflection peak; and the microcavity array grating 130 is isolated from the external environment, and the air medium inside it cannot circulate with the air medium of the external environment. Therefore, the effective refractive index of the microcavity array optical waveguide 110 is only affected by the ambient temperature. When the ambient temperature of the external environment changes, the effective refractive index of the microcavity array grating 130 also changes, thereby causing the wavelength drift of the second reflection peak, and the ambient temperature of the external environment can be obtained by wavelength demodulating the second reflection peak; finally, the ambient pressure is calculated according to the air refractive index and ambient temperature of the external environment.

[0058] This patent simultaneously prepares the microhole array grating 120 and the microcavity array grating 130 in the optical waveguide 110. The microhole array grating 120 and the microcavity array grating 130 can respectively sense the air refractive index and the ambient temperature of the external environment, and finally calculate the ambient pressure according to the air refractive index and the ambient temperature of the external environment. When sensing the ambient temperature, the microcavity array grating 130 is not affected by the ambient pressure, and when sensing the ambient pressure, the microhole array grating 120 can calculate the ambient pressure using the ambient temperature detected by the microcavity array grating 130, thereby avoiding the mutual influence of the ambient temperature and the ambient pressure during measurement, and realizing the simultaneous sensing of different ambient temperatures and different ambient pressures, and having the advantages of high reliability, high sensitivity, and easy serial multiplexing.

[0059] The ambient pressure P and the air refractive index n sensed by the micro-hole array grating 120 tp and the ambient temperature t sensed by the microcavity array grating 130, satisfying the following formula:

[0060]

[0061] n s ×10 -8 =8342.54+2406147×[130-σ 2 ] -1 +15998×[38.9-σ 2 ] -1

[0062] The above formula is the dispersion formula of standard dry air, n s is the mantissa of the refractive index of air under standard conditions, and σ is the wave number.

[0063] The microhole array grating 120 and the microcavity array grating 130 are arranged as centrally as possible in the light transmission channel. For example, the two can be respectively located on both sides of the axis of the light transmission channel and have the same distance from the axis of the light transmission channel. For example, one of them can be located at the axis of the light transmission channel, and the other can be located on one side of the axis of the light transmission channel.

[0064] The optical waveguide 110 may be an integrated optical waveguide or a cylindrical optical waveguide, and its waveguide material may be, but is not limited to, glass, sapphire, lutetium oxide or ceramic, etc.; wherein the integrated optical waveguide includes a planar (thin film) dielectric optical waveguide and a strip dielectric optical waveguide, and the cylindrical optical waveguide includes an optical fiber.

[0065] like Figure 1 and 2 As shown, the optical waveguide 110 may be a dual-medium or multi-medium structure having a central dielectric layer 111 and a peripheral dielectric layer 112, such as a buried strip optical waveguide, a single-mode optical fiber, etc. For the optical waveguide 110 of such a structure, due to the difference in refractive index between the central dielectric layer 111 and the peripheral dielectric layer 112, the optical signal in the central dielectric layer 111 may be totally reflected at the interface between the central dielectric layer 111 and the peripheral dielectric layer 112, thereby maintaining forward transmission in the central dielectric layer 111, and the central dielectric layer 111 is the optical transmission channel.

[0066] like Figure 3 and 4 As shown, the optical waveguide 110 may also be a single medium structure, with external air as the peripheral medium, such as sapphire optical fiber, etc. For the optical waveguide 110 of this structure, the entire interior of the optical waveguide 110 is the light transmission channel.

[0067] The microhole array grating 120 is located at the axis of the light transmission channel, and the microcavity array grating 130 is located on one side of the axis of the light transmission channel, or the microhole array grating 120 and the microcavity array grating 130 are respectively located on both sides of the axis of the light transmission channel and are at the same distance from the axis of the light transmission channel.

[0068] Preferably, if the optical waveguide 110 is a dual-medium or multi-medium structure, the microhole array grating 120 is located at the axis of the central medium layer 111, and the microcavity array grating 130 is located on one side of the axis of the central medium layer 111; if the optical waveguide 110 is a single-medium structure, the microhole array grating 120 and the microcavity array grating 130 are respectively located on both sides of the axis of the optical waveguide 110 and are at the same distance from the axis of the optical waveguide 110.

[0069] The microhole array grating 120 includes a plurality of open microholes 131, each of which is distributed along the light transmission direction of the optical waveguide 110 and is connected to the external environment. The arrangement of the microhole array can be changed to form a Bragg grating, a phase-shift grating or a chirped grating.

[0070] Specifically, the open micropore 131 may be, but is not limited to, a columnar micropore, a conical micropore, or a trapezoidal micropore, etc.; at least one end of the open micropore 131 extends outside the optical waveguide 110 to communicate with the external environment.

[0071] In this embodiment, the extending direction of the open micropores 131 is perpendicular to the light transmission direction of the optical waveguide 110. In a specific implementation, the extending direction of the open micropores 131 may also be arranged at an inclined angle to the light transmission direction of the optical waveguide 110.

[0072] The microcavity array grating 130 includes a plurality of closed microcavities 131, each of which is distributed along the light transmission direction of the optical waveguide 110 and isolated from the external environment. The arrangement of the microcavity array can be changed to form a Bragg grating, a phase-shift grating or a chirped grating.

[0073] Specifically, the closed microcavity 131 may be, but is not limited to, a spherical microcavity or an ellipsoidal microcavity, etc., which may not have an extension direction (such as a spherical shape), or may be similar to the open micropore 131, have an extension direction (such as an ellipsoid shape) and its extension direction is also perpendicular to the light transmission direction of the optical waveguide 110 or is set at an inclined angle, or is parallel to the extension direction of the open micropore 131; the closed microcavity 131 does not extend to the outside of the optical waveguide 110 in any direction, thereby being isolated from the external environment.

[0074] It should be particularly noted that the closed microcavity 131 is formed by the internal medium of the optical waveguide 110 undergoing a local refractive index change induced by external energy such as a femtosecond laser. This part of the internal medium is eventually completely ablated or the refractive index changes permanently. Therefore, the interior of the closed microcavity 131 can be either a hollow microcavity (with vacuum, air or vaporized medium material inside) or a solid microcavity (with a medium material with a changed refractive index inside).

[0075] The microhole array grating 120 has a first central wavelength, and the microcavity array grating 130 has a second central wavelength, so that the reflection spectrum can form a first reflection peak corresponding to the microhole array grating 120 and a second reflection peak corresponding to the microcavity array grating 130 at different wavelength positions.

[0076] Embodiment 2

[0077] like Figure 6 As shown, a method for preparing a microhole array grating temperature and pressure sensor is used to prepare the microhole array grating temperature and pressure sensor described in Example 1.

[0078] The preparation method comprises the following steps:

[0079] Step 100: designing structural parameters of the microhole array grating 120 and the microcavity array grating 130 respectively.

[0080] In step 100, the structural parameters of the microhole array grating 120 and the microcavity array grating 130 correspond to their respective grating parameters, and the structural parameters of the microhole array grating 120 and the microcavity array grating 130 can be obtained through simulation and design according to the required grating parameters.

[0081] The refractive index modulation spectrum of the microhole array grating 120 has the following two important differences compared with the grating of the optical waveguide 110 with a sinusoidal refractive index modulation spectrum written by a conventional ultraviolet laser: 1) The refractive index modulation of the microhole array grating 120 is a square wave spectrum with a large refractive index difference; 2) The refractive index modulation area of ​​the microhole array grating 120 is composed of open microholes 131 with a high aspect ratio, which only covers the central area of ​​the optical transmission channel. Therefore, the Rouard algorithm and the transfer matrix method are combined to simulate and design the microhole array grating 120, and the structural parameters of the microhole array grating 120 are obtained through simulation, wherein the microhole aperture of the open microholes 131 corresponds to the width of the refractive index modulation area of ​​the microhole array grating 120, and the microhole spacing of the open microholes 131 corresponds to the grating period, duty cycle, number of periods, and grating order of the microhole array grating 120. On the other hand, the influence of the microhole offset of the open microhole 131 on the overlap integral, that is, the influence on the reflectivity of the microhole array grating 120 is studied through simulation.

[0082]

[0083] In the above formula, R0, S0, R M , S M are the complex amplitudes of the forward transmission mode and the reverse transmission mode at the head end and the end of the microhole array grating 120, respectively. M is the number of open microholes 131 set in the simulation. F M is the transmission matrix of the Mth open micropore 131.

[0084]

[0085] Each open micropore 131 can be regarded as a uniform weak grating, and its transmission matrix is ​​shown in the above formula, where κ is the AC coupling coefficient; σ is the DC coupling coefficient; Δz is the micropore spacing of the micropore array grating 120; γ B The value is defined as the square root of the difference between the AC coupling coefficient and the DC coupling coefficient. On the other hand, the open micropores 131 only cover a portion of the light transmission channel, and the overlap integral η of the micropore array grating 120 v will change with the location of the open micropore 131 and the aperture size of the open micropore 131. Therefore, the coupling coefficient of each order mode κ v The relationship between the position and the aperture size of the open micropore 131 is κ v =η v πΔn / λB, where Δn is the refractive index modulation, λ B is the wavelength of the first reflection peak of the microhole array grating 120, and v is the optical frequency of the detection light signal.

[0086] Step 200: using a femtosecond laser to sequentially write the microhole array grating 120 and the microcavity array grating 130 in the optical transmission channel of the optical waveguide 110 to obtain the microhole array grating temperature and pressure sensor.

[0087] In step 200 , a femtosecond laser writing system is used to modulate the refractive index inside the optical waveguide 110 , so as to sequentially form the microhole array grating 120 and the microcavity array grating 130 .

[0088] like Figure 5 As shown, the femtosecond laser writing system includes an optical subsystem and a motion subsystem, wherein the optical subsystem is used to shape the femtosecond laser, and the motion subsystem is used to drive the optical waveguide 110 to move; the optical subsystem includes a femtosecond laser 1, a power attenuator 2, a polarization controller 3, a mechanical shutter 4, a beam splitter 5, a Michelson interferometer 5, a spatial light modulator 7, a focusing lens 8, a dichroic mirror 9, a focusing objective lens 10 and a CCD camera 11, wherein the Michelson interferometer 5 has a first interference arm and a second interference arm, wherein the first interference arm includes a first reflector 61, and the second interference arm includes a second reflector 62 and a one-dimensional displacement platform 63; wherein the femtosecond laser An optical device 1, a power attenuator 2, a polarization controller 3, a mechanical shutter 4, a beam splitter 5, a spatial light modulator 7, a focusing lens 8, a dichroic mirror 9 and a focusing objective lens 10 are sequentially arranged along the propagation path of the femtosecond laser. The first reflecting mirror 61 and the second reflecting mirror 62 of the Michelson interferometer 5 are respectively arranged on the two splitting paths of the beam splitter 5. The CCD camera 11 is located on the side of the dichroic mirror 9 facing away from the focusing objective lens 10. The motion subsystem includes a rotating fixture 12, a six-axis pitch platform 13 and a precision displacement platform 14. The rotating fixture 12 is arranged on the six-axis pitch platform 13, and the six-axis pitch platform 13 is arranged on the precision displacement platform 14.

[0089] The single-pulse femtosecond laser emitted by the femtosecond laser 1 passes through the power attenuator 2, the polarization controller 3 and the mechanical shutter 4 in sequence for power attenuation adjustment, polarization state adjustment and optical path on-off control, and then enters the beam splitter 5. The beam splitter 5 divides the single-pulse femtosecond laser into two mutually perpendicular femtosecond laser beams at a ratio of 1:1. After one femtosecond laser beam enters the first interference arm of the Michelson interferometer 5, it is reflected back to the beam splitter 5 by the first reflector 61. After the other femtosecond laser beam enters the second interference arm of the Michelson interferometer 5, it is reflected back to the beam splitter 5 by the second reflector 62. The second reflector 62 is driven to move by the one-dimensional displacement platform 63 to adjust the distance between the second reflector 62 and the beam splitter 5, so that there is an optical path difference between the two femtosecond laser beams, thereby generating Pulse delay is performed to convert the single-pulse femtosecond laser into a double-pulse femtosecond laser to achieve pulse shaping in timing; then the double-pulse femtosecond laser is re-emitted onto the spatial light modulator 7, and modulated by the conical lens phase diagram loaded in the spatial light modulator 7 to convert the double-pulse femtosecond laser from a Gaussian beam to a Bessel beam to achieve pulse shaping in space; after reflection, transmission and focusing processing by the focusing lens 8, the dichroic mirror 9 and the focusing objective lens 10, the double-pulse Bessel beam is focused into the optical transmission channel of the optical waveguide 110; and the six-axis pitch platform 13 and the precision displacement platform 14 drive the rotating fixture 12 to pitch and displace during the writing process of the microhole array grating 120 and the microcavity array grating 130, thereby adjusting the writing posture of the optical waveguide 110.

[0090] Specifically, Figure 7 As shown, in step 200, the steps of sequentially writing the microhole array grating 120 and the microcavity array grating 130 in the light transmission channel of the optical waveguide 110 using a femtosecond laser are as follows:

[0091] Step 210: construct the above-mentioned femtosecond laser writing system.

[0092] Step 220 : clamping and fixing the optical waveguide 110 on the rotating fixture 12 .

[0093] Step 230: Load the required axicon phase diagram into the spatial light modulator 7.

[0094] Step 240: Control the femtosecond laser 1 to emit a single-pulse femtosecond laser, so that the single-pulse femtosecond laser forms a double-pulse Bessel beam after being shaped by the Michelson interferometer 5 and the spatial light modulator 7, and focus the double-pulse Bessel beam in the optical transmission channel of the optical waveguide 110.

[0095] Step 250: The rotating fixture 12 is driven to pitch and displace by the six-axis pitch platform 13 and the precision displacement platform 14, thereby adjusting the writing posture of the optical waveguide 110 so that the double-pulse Bessel light beam can be written in the optical transmission channel of the optical waveguide 110 to form the microhole array grating 120.

[0096] Step 260: shielding the first interference arm or the second interference arm of the Michelson interferometer 5 , and not loading any conical lens phase diagram in the spatial light modulator 7 .

[0097] Step 270 : controlling the femtosecond laser 1 to emit the single-pulse femtosecond laser again, and focusing the single-pulse femtosecond laser in the optical transmission channel of the optical waveguide 110 .

[0098] Step 280: The rotating fixture 12 is driven to pitch and displace by the six-axis pitch platform 13 and the precision displacement platform 14, thereby adjusting the writing posture of the optical waveguide 110 so that the single-pulse femtosecond laser can write in the optical transmission channel of the optical waveguide 110 to form the microcavity array grating 130.

[0099] During the writing process, the repetition rate of the femtosecond laser 1 and the moving speed of the optical waveguide 110 can be adjusted to flexibly control the grating period of each of the microhole array grating 120 and the microcavity array grating 130, and the optical waveguide 110 can be imaged in real time through the focusing objective lens 10 by the CCD camera 11 to observe the grating morphology of each of the microhole array grating 120 and the microcavity array grating 130 in real time.

[0100] Step 300: Etching the microhole array grating 120 using an etching solution.

[0101] In step 300, since the inner wall of the open micropores 131 etched by femtosecond laser is relatively rough, the spectrum quality of the micropore array grating 120 is relatively poor. In order to ensure the smoothness of the inner wall of the micropores of the micropore array grating 120 and improve the spectrum quality of the micropore array grating 120, a chemical etching method is used to reduce the insertion loss of the device. At the same time, etching can also finely control the micropore aperture of the micropore array grating 120 and flexibly adjust the duty cycle of the micropore array grating 120 to control and optimize the refractive index sensitivity of the micropore array grating 120. In addition, since the closed microcavity 131 of the microcavity array grating 130 is not connected to the outside world, the etching liquid will not enter the closed microcavity 131 of the microcavity array grating 130 when etching the inner wall of the open micropores 131 of the micropore array grating 120, so the microcavity array grating 130 will not be damaged.

[0102] Specifically, Figure 8 As shown, in step 300, the steps of etching the microhole array grating 120 of the optical waveguide 110 with an etching solution are as follows:

[0103] Step 310: placing the microhole array grating temperature and pressure sensor into the etching solution.

[0104] In step 310, the etching solution may be contained in a sealed container made of plastic or glass, and a resistance wire may be used to heat the sealed container containing the etching solution to speed up the etching process.

[0105] If the optical waveguide 110 is made of quartz, the etching solution is preferably but not limited to 5% hydrofluoric acid, and the sealed container is made of plastic; if the optical waveguide 110 is made of sapphire, the etching solution is preferably but not limited to a mixture of sulfuric acid and phosphoric acid in a molar ratio of 3:1, and the sealed container is made of glass.

[0106] When etching the sapphire optical waveguide 110, the temperature of the etching solution can be heated and maintained at about 330°C. At the same time, a glass sleeve is used outside the sealed container to protect the optical waveguide 110 to prevent the portion of the optical waveguide 110 outside the sealed container from being affected by the etching solution and depositing sulfate.

[0107] Step 320: Connect the microhole array grating temperature and pressure sensor to a spectrum monitoring system, and obtain the reflection spectrum of the microhole array grating temperature and pressure sensor in real time through the spectrum monitoring system.

[0108] In step 320, the spectral monitoring system includes a detection laser, a spectrometer and a circulator, wherein the circulator has an incident end, a reflection end and a transmission end, wherein the incident end is connected to the detection laser, the reflection end is connected to the spectrometer, and the transmission end is connected to the microhole array grating temperature and pressure sensor; the detection light signal emitted by the detection laser is coupled into the microhole array grating temperature and pressure sensor via the circulator, and the reflected light signal reflected back by the microhole array grating temperature and pressure sensor is coupled to the spectrometer via the circulator, and the spectrometer collects and outputs the reflection spectrum of the reflected light signal, thereby obtaining the first reflection peak and the second reflection peak corresponding to the microhole array grating 120 and the microcavity array grating 130 respectively on the reflection spectrum.

[0109] Step 330: Observe the reflection spectrum of the microhole array grating temperature and pressure sensor. When the first reflection peak corresponding to the microhole array grating 120 in the reflection spectrum gradually becomes smooth and has the minimum loss, remove the microhole array grating temperature and pressure sensor from the etching solution.

[0110] Step 340: Cleaning the microhole array grating temperature and pressure sensor.

[0111] In step 340, the microhole array grating temperature and pressure sensor may be immersed in distilled water and then placed in an isopropanol solution for ultrasonic cleaning to thoroughly clean the etching solution remaining on the microhole array grating temperature and pressure sensor.

[0112] Step 400: performing high temperature annealing on the microhole array grating temperature and pressure sensor.

[0113] In step 400, in order to release the internal residual stress of the microhole array grating 120 and the microcavity array grating 130 and to increase the thermal stability and reliability of the microhole array grating 120 and the microcavity array grating 130, the prepared microhole array grating temperature and pressure sensor is placed in a high-temperature furnace for a long-term annealing treatment. During the annealing process, the spectral monitoring system is used to monitor and record the reflection spectrum of the microhole array grating temperature and pressure sensor in real time until the first reflection peak wavelength and the second reflection peak wavelength of the reflection spectrum tend to be stable.

[0114] Specifically, during high-temperature annealing, if the optical waveguide 110 is made of quartz, the annealing temperature is gradually increased from room temperature (20°C) to 900°C; if the optical waveguide 110 is made of sapphire, the annealing temperature is gradually increased from room temperature (20°C) to 1500°C, with a heating rate of 10°C / min. Each time the temperature is increased by 100°C, it is kept stable for one hour. After the wavelength of the reflection spectrum is stabilized, the temperature is continued to be increased.

[0115] Embodiment 3

[0116] like Fig. 9 As shown, a test and calibration method for a microhole array grating temperature and pressure sensor is used to test and calibrate the microhole array grating temperature and pressure sensor described in Example 1.

[0117] The test and calibration method of the micro-hole array grating temperature and pressure sensor comprises the following steps:

[0118] Step S1: Under normal pressure environment P0, the microhole array grating temperature pressure sensor is placed in different temperature environments to obtain the first reflection peak wavelength of the microhole array grating 120 in different temperature environments and the second reflection peak wavelength of the microcavity array grating 130 at different temperatures, and the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating 120 under normal pressure P0 and the ambient temperature-second reflection peak wavelength response relationship of the microcavity array grating 130 are respectively fitted.

[0119] In step S1, the spectral monitoring system is used to detect the reflection spectra of the microhole array grating temperature pressure sensor at different temperatures in the normal pressure environment P0. When the microhole array grating 120 and the microcavity array grating 130 are at different temperatures, the effective refractive indexes in the microhole array grating 120 and the microcavity array grating 130 are changed by the photothermal effect, thereby causing the wavelength drift of the first reflection peak and the second reflection peak. Then, a polynomial fitting function is used to linearly fit the first reflection peak wavelength of the microhole array grating 120 at different temperatures and the second reflection peak wavelength of the microcavity array grating 130 at different temperatures, respectively, to obtain the ambient temperature-first reflection peak wavelength response relationship under normal pressure P0 and the ambient temperature-second reflection peak wavelength response relationship.

[0120] Step S2: Under different temperature environments, the microhole array grating temperature pressure sensor is placed in different pressure environments, and the first reflection peak wavelength of the microhole array grating 120 in different pressure environments is obtained, and the ambient pressure-first reflection peak wavelength response relationship and pressure sensitivity of the microhole array grating 120 in different temperature environments are respectively fitted.

[0121] In step S2, the spectral monitoring system is used to detect the reflection spectrum of the microhole array grating temperature and pressure sensor under different pressure environments. When the microhole array grating 120 is under different temperature and pressure environments, the effective refractive index of the microhole array grating 120 is affected by both the ambient temperature and the ambient pressure, and will change, thereby causing the wavelength of the first reflection peak to drift. Then, a polynomial fitting function is used to linearly fit the first reflection peak wavelength of the microhole array grating 120 under different temperature and pressure environments, and the ambient pressure-first reflection peak wavelength response relationship and pressure sensitivity (the slope of the response relationship) at different ambient temperatures are obtained.

[0122] Step S3: placing the microhole array grating temperature pressure sensor in a calibration environment, and calculating the ambient temperature T1 of the calibration environment according to the second reflection peak wavelength of the microcavity array grating 130 in the calibration environment and the ambient temperature-second reflection peak wavelength response relationship.

[0123] In step S3, since the effective refractive index of the microcavity array grating 130 is not affected by the ambient pressure, the ambient temperature T1 of the calibration environment can be calculated by substituting the second reflection peak wavelength of the microcavity array grating 130 in the calibration environment into the ambient temperature-second reflection peak wavelength response equation.

[0124] Step S4: Calculate the total wavelength drift Δλ of the microhole array grating 120 when it changes from a normal temperature and pressure environment to the calibration environment according to the ambient pressure-first reflection peak wavelength response relationship of the microhole array grating 120 under different temperature environments, and calculate the wavelength drift component Δλ caused by the ambient temperature change when the microhole array grating 120 changes from a normal temperature and pressure environment to the calibration environment according to the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating 120 under the normal pressure environment P0. T , then the total wavelength drift Δλ of the microhole array grating 120 is subtracted from its wavelength drift component Δλ T , the wavelength drift component Δλ caused by the change of the ambient pressure when the microhole array grating 120 changes from the normal temperature and pressure environment to the calibration environment is obtained p .

[0125] In step S4, the first reflection peak wavelength of the microhole array grating 120 under normal temperature and pressure environment is found through the ambient pressure-first reflection peak wavelength response relationship of the microhole array grating 120 under different temperature environments, and then the first reflection peak wavelength of the microhole array grating 120 under normal temperature and pressure environment is subtracted from the first reflection peak wavelength of the microhole array grating 120 under the calibration environment to obtain the total wavelength drift Δλ of the microhole array grating 120.

[0126] Similarly, the first reflection peak wavelength of the microhole array grating 120 under the normal pressure environment P0 and temperature T1 is found through the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating 120 under the normal pressure environment P0, and then the first reflection peak wavelength of the microhole array grating 120 under the calibration environment is subtracted from the first reflection peak wavelength of the microhole array grating 120 under the normal pressure environment P0 and temperature T1, so as to obtain the wavelength drift component Δλ caused by the ambient temperature change when the microhole array grating 120 changes from the normal temperature and pressure environment to the calibration environment. T .

[0127] Step S5: Calculate the ambient pressure of the calibration environment P = P0 + Δλ P / S P,T1 , where S P,T1 is the pressure sensitivity of the microhole array grating at ambient temperature T1.

[0128] In step S5, the calculated value of the ambient pressure of the calibration environment is compared with its actual value, so as to know the sensing detection error of the microhole array grating temperature and pressure sensor to the ambient pressure, and then calculate the error correction coefficient and write the correction coefficient into the demodulation device of the microhole array grating temperature and pressure sensor.

[0129] Preferably, the test calibration method of the present patent can be performed during the high temperature annealing step of the microhole array grating temperature pressure sensor and completed together with the high temperature annealing step.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention rather than to limit them. Although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the embodiments of the present invention can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microhole array grating temperature and pressure sensor, characterized in that: The invention comprises an optical waveguide, a microhole array grating and a microcavity array grating. The optical waveguide has an optical transmission channel inside. The microhole array grating and the microcavity array grating are formed in parallel in the optical transmission channel of the optical waveguide. The microhole array grating is connected to the external environment, and the microcavity array grating is isolated from the external environment.

2. The microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The optical waveguide is an integrated optical waveguide or a cylindrical optical waveguide, and its waveguide material is glass, sapphire, lutetium oxide or ceramic; wherein the integrated optical waveguide includes a planar (thin film) dielectric optical waveguide and a strip dielectric optical waveguide, and the cylindrical optical waveguide includes an optical fiber.

3. The microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The microhole array grating includes a plurality of open microholes, each of which is distributed along the light transmission direction of the optical waveguide and is connected to the external environment.

4. The microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The microcavity array grating includes a plurality of closed microcavities, each of which is distributed along the light transmission direction of the optical waveguide and isolated from the external environment.

5. The microhole array grating temperature and pressure sensor according to claim 4, characterized in that: The closed microcavity is formed by inducing a local refractive index change in the internal medium of the optical waveguide, and this part of the internal medium is completely ablated or the refractive index changes permanently; the closed microcavity is a hollow microcavity, the interior of which is a vacuum, air or a gasified medium material, or the closed microcavity is a solid microcavity, the interior of which is a medium material with a changed refractive index.

6. The microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The microhole array grating has a first central wavelength, and the microcavity array grating has a second central wavelength.

7. The microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The ambient pressure P and the air refractive index n sensed by the microhole array grating tp and the ambient temperature t sensed by the microcavity array grating, satisfying the following formula: n s ×10 -8 =8342.54+2406147×[130-p 2 ] -1 +15998×[38.9-s 2 ] -1 The above formula is the dispersion formula of standard dry air, n s is the mantissa of the refractive index of air under standard conditions, and σ is the wave number.

8. The method for preparing the microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The steps include: Step 100: designing structural parameters of the microhole array grating and the microcavity array grating respectively; Step 200: using a femtosecond laser to sequentially write the microhole array grating and the microcavity array grating in the optical transmission channel of the optical waveguide to obtain the microhole array grating temperature and pressure sensor.

9. The method for preparing the microhole array grating temperature and pressure sensor according to claim 8, characterized in that: After step 200, the following steps are also included: Step 300: using an etching solution to etch the microhole array grating.

10. The method for preparing the microhole array grating temperature and pressure sensor according to claim 8, characterized in that: After step 300, the following steps are also included: Step 400: performing high temperature annealing on the microhole array grating temperature and pressure sensor.

11. The method for preparing the microhole array grating temperature and pressure sensor according to claim 8, characterized in that: In step 200, the steps of sequentially writing the microhole array grating and the microcavity array grating in the light transmission channel of the optical waveguide using a femtosecond laser are as follows: Step 210: Build a femtosecond laser writing system, the femtosecond laser writing system includes an optical subsystem and a motion subsystem, the optical subsystem is used to shape the femtosecond laser, and the motion subsystem is used to drive the optical waveguide to move; the optical subsystem includes a femtosecond laser, a power attenuator, a polarization controller, a mechanical shutter, a beam splitter, a Michelson interferometer, a spatial light modulator, a focusing lens, a dichroic mirror, a focusing objective lens and a CCD camera, the Michelson interferometer has a first interference arm and a second interference arm, the first interference arm includes a first reflector, the second interference arm includes a second reflector and a one-dimensional A displacement platform; wherein the femtosecond laser, power attenuator, polarization controller, mechanical shutter, beam splitter, spatial light modulator, focusing lens, dichroic mirror and focusing objective are sequentially arranged along the propagation path of the femtosecond laser, the first reflector and the second reflector of the Michelson interferometer are respectively arranged on the two splitting paths of the beam splitter, and the CCD camera is located on the side of the dichroic mirror facing away from the focusing objective; the motion subsystem includes a rotating fixture, a six-axis pitch platform and a precision displacement platform, the rotating fixture is arranged on the six-axis pitch platform, and the six-axis pitch platform is arranged on the precision displacement platform; Step 220: clamping and fixing the optical waveguide on the rotating fixture; Step 230: Loading the required axicon phase diagram into the spatial light modulator; Step 240: controlling the femtosecond laser to emit a single-pulse femtosecond laser, so that the single-pulse femtosecond laser forms a double-pulse Bessel beam after being shaped by the Michelson interferometer and the spatial light modulator, and focusing the double-pulse Bessel beam in the optical transmission channel of the optical waveguide; Step 250: driving the rotating fixture to pitch and displace via the six-axis pitch platform and the precision displacement platform, thereby adjusting the writing posture of the optical waveguide, so that the double-pulse Bessel light beam writes and forms the microhole array grating in the optical transmission channel of the optical waveguide; Step 260: shielding the first interference arm or the second interference arm of the Michelson interferometer, and not loading any axicon phase diagram in the spatial light modulator; Step 270: Control the femtosecond laser to emit the single-pulse femtosecond laser again, and focus the single-pulse femtosecond laser in the optical transmission channel of the optical waveguide; Step 280: The rotating fixture is driven to pitch and displace by the six-axis pitch platform and the precision displacement platform, thereby adjusting the writing posture of the optical waveguide so that the single-pulse femtosecond laser writes in the optical transmission channel of the optical waveguide to form the microcavity array grating.

12. The test and calibration method of the microhole array grating temperature and pressure sensor according to claim 1, characterized in that: The steps include: Step S1: Under a normal pressure environment P0, the microhole array grating temperature pressure sensor is placed in different temperature environments to obtain the first reflection peak wavelength of the microhole array grating in different temperature environments and the second reflection peak wavelength of the microcavity array grating at different temperatures, and the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating under normal pressure P0 and the ambient temperature-second reflection peak wavelength response relationship of the microcavity array grating are respectively fitted; Step S2: placing the microhole array grating temperature pressure sensor in different pressure environments under different temperature environments, and obtaining the first reflection peak wavelength of the microhole array grating in different pressure environments, and fitting the ambient pressure-first reflection peak wavelength response relationship and pressure sensitivity of the microhole array grating in different temperature environments respectively; Step S3: placing the microcavity array grating temperature pressure sensor in a calibration environment, and calculating the ambient temperature T1 of the calibration environment according to the second reflection peak wavelength of the microcavity array grating in the calibration environment and the ambient temperature-second reflection peak wavelength response relationship; Step S4: Calculate the total wavelength drift Δλ of the microhole array grating when it changes from a normal temperature and pressure environment to the calibration environment according to the ambient pressure-first reflection peak wavelength response relationship of the microhole array grating under different temperature environments, and calculate the wavelength drift component Δλ caused by the ambient temperature change when the microhole array grating changes from a normal temperature and pressure environment to the calibration environment according to the ambient temperature-first reflection peak wavelength response relationship of the microhole array grating under the normal pressure environment P0. T , then the total wavelength shift Δλ of the microhole array grating is subtracted from its wavelength shift component Δλ T , the wavelength drift component Δλ caused by the change of the ambient pressure when the microhole array grating changes from the normal temperature and pressure environment to the calibration environment is obtained p ; Step S5: Calculate the ambient pressure of the calibration environment P = P0 + Δλ P / S P,T1 , where S P,T1 is the pressure sensitivity of the microhole array grating at ambient temperature T1.

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