CN106569152A - Optical fiber cantilever beam magnetic field sensing probe based on giant magnetostrictive film - Google Patents

Abstract

The invention discloses an optical fiber cantilever beam magnetic field sensing probe based on a giant magnetostrictive film, and belongs to the technical field of optical fiber sensors. The optical fiber cantilever beam magnetic field sensing probe comprises an optical fiber, a fixing and supporting end, an optical fiber cantilever beam, a chromium metal film and the giant magnetostrictive film. The optical fiber cantilever beam is arranged on the optical fiber end surface. The optical fiber cantilever beam is connected with the optical fiber end surface through the fixing and supporting end. The optical fiber cantilever beam and the optical fiber end surface form a Fabry-Perot resonant cavity. The chromium metal film and the giant magnetostrictive film are plated on the external surface of the optical fiber cantilever beam in turn. In a magnetic field to be measured, telescoping of the giant magnetostrictive film results in the deflection of the optical fiber cantilever beam or the change of the resonant frequency, and the deflection of the optical fiber cantilever beam or the change of the resonant frequency is detected by the Fabry-Perot resonant cavity so as to measure the size of the external magnetic field.

Description

A Fiber Optic Cantilever Beam Magnetic Field Sensing Probe Based on Giant Magnetostrictive Film

technical field

The invention relates to a magnetic field sensing probe, in particular to an optical fiber cantilever beam magnetic field sensing probe based on a giant magnetostrictive film.

Background technique

The current magnetic field sensors are mainly based on mechanisms such as Hall effect, magnetoresistance effect, fluxgate effect, tunnel effect and nuclear magnetic resonance effect. Interference is generated, which limits the further improvement of the detection accuracy of this type of sensor. Traditional magnetic field sensors are bulky and difficult to detect magnetic fields in narrow spaces. The optical fiber magnetic field sensor does not affect the electromagnetic field to be measured, and has the advantages of corrosion resistance, light weight, small size, etc., which is beneficial to the application in aviation and aerospace fields and narrow spaces. The optical fiber cantilever beam magnetic field sensor combines the characteristics of the optical fiber magnetic field sensor and the cantilever beam, and has the advantages of miniaturization, easy realization of multi-point distributed detection, long-distance detection, high precision, low power consumption and all-optical transmission.

There are three main types of fiber-optic cantilever beams. (1) Paste the optical fiber on the cantilever beam, and the vibration of the cantilever beam will cause some physical quantities in the optical fiber to change, so as to know the change of the external quantity to be detected. (2) Fabricate a cantilever beam structure on the fiber body, and use the interference principle or other principles to measure the change of the external quantity to be detected. (3) The optical fiber itself is used as a cantilever beam, which is vibrated by a vibration source such as piezoelectric ceramics, so as to measure the change of the external quantity to be detected.

In the present invention, the cantilever beam is processed on the end face of the optical fiber to realize the integrated structure of the optical fiber. The outer surface of the optical fiber cantilever beam is coated with a chromium metal film and a giant magnetostrictive thin film (GMF: Giant Magnetostrictive Thin Film), forming a giant magnetostrictive thin film (GMF: Giant Magnetostrictive Thin Film). The thin-film optical fiber cantilever beam magnetic field sensing probe does not require electrical signal excitation, so there is no interference of the excitation electrical signal to the electromagnetic field to be measured, it can be miniaturized, and the detection accuracy is effectively improved.

Contents of the invention

Aiming at the shortcomings of traditional magnetic field sensors, the invention designs a fiber optic cantilever beam magnetic field sensing probe based on giant magnetostrictive films.

The technical scheme adopted in the present invention: a kind of optical fiber cantilever beam magnetic field sensing probe based on giant magnetostrictive film, comprising: optical fiber, fixed support end, optical fiber cantilever beam, chromium metal film, giant magnetostrictive thin film, as shown in Figure 1 Show.

The optical fiber cantilever beam is located on the end face of the optical fiber to form an integrated optical fiber structure.

The length of the fiber cantilever beam is 105 μm-115 μm, the width is 15 μm-30 μm, and the thickness is 3 μm-5 μm.

The length of the fixed support end is 10 μm-20 μm, the width of the fixed support end is the same as the width of the fiber cantilever beam, the fiber cantilever beam and the end face of the fiber are connected through the support end, and the fiber cantilever beam and the fiber end face form a Fabry-Perot resonant cavity .

The chromium metal film is plated on the outer surface of the optical fiber cantilever beam, and its thickness is 50nm, which acts as a buffer layer for the giant magnetostrictive film;

The giant magnetostrictive thin film is plated on the outside of the chromium metal film and is made of TbDyFe material with a thickness of 1 μm-1.5 μm.

The beneficial effects of the present invention are:

1. The optical fiber is used as the sensing probe. The optical fiber sensing probe works under all-optical excitation, which will not interfere with the magnetic field to be measured, and the magnetic field to be measured will not cause electromagnetic interference to the optical fiber sensing probe. The optical fiber sensing probe is small in size and suitable for magnetic field detection in narrow spaces.

2 Process the cantilever beam at one end of the optical fiber to form an integrated structure of the optical fiber and realize the miniaturization of the sensing probe. The cantilever beam and the end face of the fiber form a Fabry-Perot optical resonant cavity. The Fabry-Perot resonant cavity is an extrinsic type, and the cavity is composed of an air gap. Its refractive index n ₀ ≈1, and its detection accuracy can reach sub- Nano precision, so it can effectively improve the detection accuracy of the sensing probe.

3. The outer surface of the fiber optic cantilever beam is coated with chromium metal film, which effectively improves the reflectivity of light and forms a double-layer sensitive resonance structure. Coating a layer of giant magnetostrictive film on the chromium metal film, the giant magnetostrictive film has a larger magnetostriction coefficient, can produce larger magnetostriction, thereby effectively improving the detection accuracy of the magnetic field.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a front view of the optical fiber cantilever beam magnetic field sensing probe of the present invention. In the figure: 1 is an optical fiber, 2 is a fixed support end, 3 is a cantilever beam of an optical fiber, 4 is a chromium metal film, and 5 is a giant magnetostrictive film;

Fig. 2 is a top view of the optical fiber cantilever beam magnetic field sensing probe of the present invention. In Fig. 2: 1 is an optical fiber, 5 is a giant magnetostrictive film.

Figure 3 is a schematic diagram of the detection.

detailed description

In Fig. 1 and Fig. 2, the technical solution adopted by the present invention: a kind of optical fiber cantilever beam magnetic field sensing probe based on giant magnetostrictive film, comprising: optical fiber 1, fixed support end 2, optical fiber cantilever beam, 3, chromium metal Film 4, giant magnetostrictive film 5.

The optical fiber cantilever beam 3 is located at the end face of the optical fiber 1, has a length of 105 μm-115 μm, a width of 15 μm-30 μm, and a thickness of 3 μm-5 μm, forming an integrated optical fiber structure.

The length of the fixed support end 2 is 10 μm-20 μm, the width of the fixed support end is the same as the width of the optical fiber cantilever beam 2, the optical fiber cantilever beam and the end face of the optical fiber are connected through the fixed support end, and the optical fiber cantilever beam and the end face of the optical fiber form a Fabry-Perkin beam. Lo resonator.

The chromium metal film 3 is plated on the outer surface of the optical fiber cantilever 2, and its thickness is 50nm, which acts as a buffer layer of the giant magnetostrictive film, has a large reflectivity to the incident laser light, and makes the optical fiber cantilever form a double Layer-sensitive resonant structures.

The giant magnetostrictive film is plated on the outside of the chromium metal film and is a TbDyFe material with a thickness of 1 μm-1.5 μm. It will expand and contract under the action of a magnetic field, and its anisotropy constant is almost zero at room temperature, showing a huge Magnetostrictive effect, the magnetostrictive coefficient is as high as 1500-2000ppm, which can realize sensitive detection in the magnetic field.

The manufacturing process of the optical fiber cantilever beam in the present invention adopts the focused plasma beam processing method (FIB), and the technological process is as follows: (a) the end face of the optical fiber is polished and cleaned; Milling until the required width and height of the fiber cantilever along the diameter direction are reached; (c) the fiber is rotated through an angle of 90° along the axial direction, and then the focused ion beam is etched along the direction parallel to the fiber end face, and the fiber The fixed part at one end of the cantilever beam is removed by abrasion, and the fiber cantilever beam and the fiber end face form a Fabry-Perot cavity structure; (d) The fiber cantilever beam is thinned to the required thickness by focusing plasma beam milling. The chromium metal film and the giant magnetostrictive film were plated on the fiber cantilever beam by magnetron sputtering.

In Figure 3, the laser light source is connected to one fiber port on one side of the fiber coupler, the photodetector is connected to the other fiber port on one side of the fiber coupler, and one fiber port on the other side of the fiber coupler is connected to the fiber sensing probe connection, the other fiber port on the other side is immersed in the matching solution.

The basic principle of the invention for detecting the magnetic field is as follows: in the magnetic field, the giant magnetostrictive film expands and contracts, thereby driving the optical fiber cantilever beam to bend, and the cavity length of the Fabry-Perot cavity changes accordingly. The modulated light emitted by the laser light source is coupled into the optical fiber, enters the Fabry-Perot cavity, returns along the original path after being reflected in the Fabry-Perot cavity, meets and interferes, and is finally received by the photodetector ,As shown in Figure 3. The greater the magnetic field strength, the greater the shrinkage of the giant magnetostrictive material, the greater the deflection of the fiber cantilever beam, and the longer the cavity length of the Fabry-Perot resonator, so the interference output signal received by the photodetector Corresponding changes also occurred. The magnitude of the external magnetic field can be obtained by signal modulation of the interference output signal received by the photodetector. Another principle of the invention for detecting the magnetic field: in the magnetic field, the giant magnetostrictive film stretches, thereby driving the optical fiber cantilever beam to bend, and the difference in the size of the external magnetic field causes the difference in the stretching degree of the giant magnetostrictive film. The modulated light emitted by the laser light source is coupled into the optical fiber and incident on the optical fiber cantilever beam. Due to the "double film thermal effect", the optical fiber cantilever beam has photothermal excitation resonance. In the magnetic field, the giant magnetostrictive film stretches and changes the fiber cantilever The degree of deflection of the beam will change the resonant frequency of the fiber optic cantilever beam, and the frequency of the reflected signal received by the photodetector will change, so the magnitude of the external magnetic field can be obtained.

Claims (3)

1. a kind of optic fibre cantilev magnetic field sensing based on giant magnetostrictive thin film is popped one's head in, including：Optical fiber, clamped end, Optic fibre cantilev, chromium metal film, giant magnetostrictive thin film.Optic fibre cantilev is located at fiber end face, is formed Optical fiber integration, optic fibre cantilev is connected with fiber end face by clamped end, optic fibre cantilev and optical fiber end Face constitutes Fabry-Perot cavity, and optic fibre cantilev outer surface successively stretch by chrome-plated metal film and super mangneto Contracting film.

2. the optical fiber cantilever beam length described in is 105 μm -115 μm, and width is 15 μm -30 μm, and thickness is 3 μm -5 μm, clamped end length is 10 μm -20 μm, the width phase of clamped end width and optic fibre cantilev Together.

3. the chromium metal film and giant magnetostrictive thin film described in is plated in successively the outer surface of optic fibre cantilev, chromium metal film Thickness is 50nm, and Giant magnetostrictive thin film is TbDyFe materials, and thickness is 1 μm -1.5 μm.