JPH03287088A - Manufacture of magnetic sensor - Google Patents

Abstract

PURPOSE:To reduce a manufacture cost by producing two Faraday elements by cutting a GGG substrate to be 45 deg. oblique and further making the GGG substrate usable as a total reflection mirror. CONSTITUTION:Garnet crystalline films 1 having a Faraday effect are grown on both surfaces of the GGG (gadolinium.gallium.garnet) substrate 2 by an LPE (liquid crystal epitaxial growing method) method to cut into a cube. Next, GGG substrate 2a is cut so as to make an angle to the surface of films 1a be 45 deg. and optically polished. Thus, the garnet crystalline films 1a provided with two total reflection mirrors 2b of GGG substrate are produced. A magnetic sensor is assembled by using these films 1a. An independent total reflection mirror is unrequired for this magnetic sensor. As the result, the number of constituting component and bonding places for the magnetic sensor are reduced, then the manufacture cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a magnetic sensor that optically measures the strength of a magnetic field using the Faraday effect.

2. Description of the Related Art Conventionally, this type of magnetic sensor has had a configuration as shown in FIG. As shown in the figure, the optical fiber 6 on the light incidence side
a, Ceramic 5a with Rondo lens.

Polarizer 3, garnet crystal film 1 with Faraday effect
b. Gadolinium gallium garnet (hereinafter referred to as GGG)
) A substrate 2C, a garnet crystal film 1C having a Faraday effect, a total reflection mirror 7, an analyzer 4 + a ceramic 6b with a rod lens, and an optical fiber 6b are arranged in this order, and the gap between the garnet crystal films 1b and 1e and the GGG substrate 2 can be removed. All were fixed with adhesive. Garnet crystal film 1b, 1
When C is placed in a magnetic field, the plane of polarization of the incident light rotates due to the Faraday effect, and the amount of light passing through the analyzer 4 changes. The strength of the magnetic field is measured by detecting changes in the amount of light.

The method of assembling this magnetic sensor is as shown in Figure 3.
First, a liquid crystal epitaxial growth method (hereinafter abbreviated as LPE) was applied to both sides of an optically polished GGG substrate 2C having a thickness of several hundred μm.

) Garnet crystal films 1b and 10 with a thickness of several tens of micrometers are formed, and the surfaces thereof are optically polished. A polarizer 3 and a total reflection mirror 7 are adhered to both surfaces of the Faraday element thus prepared using a thermosetting epoxy resin, thereby assembling the faraday element. Furthermore, as shown in FIG. 3, other optical components were similarly bonded and assembled using thermosetting epoxy resin to create a magnetic sensor.

Problems to be Solved by the Invention Due to the large number of parts and the large number of adhesive connections in a conventional configuration, the yield rate for magnetic sensors is low and manufacturing costs are high. There was M.

Further, the GGG substrate 2C constituting the Faraday element is necessary only when growing the garnet crystal films 1b and 1c, and is not originally necessary for the magnetic sensor.

It is desirable that the thickness be as thin as possible. However, in order to construct a highly sensitive magnetic sensor, a garnet crystal film 1
It is necessary to increase the Faraday rotation angle by increasing the film thickness of b and 1c, and in order to create a thick garnet film,
In order to prevent the GGG substrate 2C from cracking, a thick QGG substrate is required. As a result, the two garnet films are separated by the thickness of the GGG substrate 2c, which makes it difficult to create a magnetic sensor that extends in the magnetic field detection direction. There was a problem that it became difficult to

The present invention solves these problems, and aims to provide a compact, highly sensitive optical magnetic sensor with a high yield and low cost.

Means for Solving the Problem In order to solve this problem, the present invention provides LP garnet crystal films having a Faraday effect on both sides of a thick GGG substrate.
After growing using the E method, two Faraday elements were created by cutting the GGG substrate at an angle of 45°, and then growing using the G method.
The GG substrate can also be used as a total reflection mirror.

Effect: This configuration allows the total reflection mirror to be omitted, reducing the number of parts required to construct the magnetic sensor, and reducing the number of adhesive bonding points, reducing the number of man-hours required to assemble the magnetic sensor. At the same time, manufacturing costs are also reduced. Furthermore, the phenomenon in which the Faraday rotation angle is affected by the stress caused by the difference in thermal expansion coefficients generated at the bonding points is also eliminated as the number of bonding points is reduced.

Since a thick GGG substrate is used, a thick garnet film can be grown stably, and the Faraday rotation angle can be increased, resulting in improved sensitivity of the magnetic sensor.

Embodiment FIGS. 1 and 2 show the entire structure of a magnetic sensor according to an embodiment of the present invention. First, as shown in FIG. 1(a), on both sides of a thick circular GGG substrate 2 with a thickness of -.

A garnet crystal film 1 having a Faraday effect having a thickness of several tens of μm is grown by the LPE method and cut into cubes as shown in FIG. 1(b). The GGG substrate 2& is set at an angle of 45° with respect to the surface of the garnet crystal film 1a, as shown in FIG. Cut and optically polish. In this way, two garnet crystal films 1d with GGG substrate total reflection mirrors 2b are created from one member. This G
As shown in FIG. 2, a magnetic sensor is assembled using the GG substrate and the garnet crystal film 1al with the total reflection mirror 2b. That is, from the light incident side, the optical fiber 6a, the ceramic with rod lens 5a, the polarizer 3, the gannet crystal film 1a, and the GG
It is constructed in this order: a G-substrate total reflection mirror 2b, an analyzer 4, a rod lens-equipped ceramic 5b, and an optical fiber z<6b. In this magnetic sensor, the garnet crystal film 1a, the GGG substrate 5, and the autopsy mirror 2b are all bonded together with thermosetting epoxy resin. Optical axis alignment work is required only between the analyzer 4 and the rod lens-equipped ceramic, and the other parts are bonded with the surface accuracy of each member. Oh, the GGG board full autopsy mirror 2b.

Optical polishing is also required for the joint surface with analyzer 4, as shown in Figure 1(c).
Polished at the same time as total reflection mirror polishing.

When such a magnetic sensor is placed in an AC or DC magnetic field, when light polarized by the polarizer 3 passes through the garnet crystal film 1a exhibiting the Faraday effect, the plane of polarization changes in proportion to the strength of the magnetic field. Rotate.

When the light with the polarization plane rotated passes through the analyzer 4, which is arranged in advance so that the polarization plane is orthogonal to the polarizer 3,
The amount of light passing through the analyzer 4 increases in proportion to the strength of the magnetic field. By measuring this amount of light, the strength of the magnetic field and changes in the strength of the magnetic field can be determined.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, by utilizing GGG for growing a garnet crystal film, a Faraday element made of a garnet crystal film integrated with a total reflection mirror can be used. Yosi.

An independent total reflection mirror is not required. As a result, the number of magnetic sensor components and bonding locations are reduced, preventing a drop in magnetic sensor yield due to poor bonding.

It is possible to reduce manufacturing costs.

In addition, since the garnet crystal film, which exhibits the Faraday effect in response to magnetic fields, is bonded with adhesive on only one side, this phenomenon occurs due to curing shrinkage of the adhesive or the difference in thermal expansion coefficient between the adhesive and the garnet crystal film. The effects of stress are reduced and the temperature characteristics of the magnetic sensor are also improved.

Furthermore, since the GGG substrate is made of goldstone, it is possible to grow a thick garnet crystal film, and a highly sensitive magnetic sensor can be realized. Further, since two Faraday elements can be obtained by cutting the thick GGG substrate portion diagonally, the productivity of Faraday elements is increased and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a method for manufacturing a garnet crystal film according to an embodiment of the present invention, FIG. 2 is a perspective view showing the structure of the same magnetic sensor, and FIG. 3 is a perspective view showing the structure of a conventional magnetic sensor. It is a diagram. 1.1a...Garnet crystal film, 2a...
...GGG board, 2b...C1GG board total reflection mirror, 3...Polarizer, 4...Analyzer, 5a, 5b...With rod lens ceramic y
-, ea, eb... Optical fiber.

Claims (1)

[Claims] A method for manufacturing a magnetic sensor using the Faraday effect, which includes a polarizer, a garnet crystal grown film having the Faraday effect, a mirror, and an analyzer, the Faraday effect being formed on a substrate cut from a gadolinium-gallium-garnet single crystal. A method for manufacturing a magnetic sensor in which a garnet single crystal film having a 100% oxide film is formed by a liquid crystal epitaxial growth method, the gadolinium gallium garnet single crystal plate is cut at an angle of 45 degrees, and the cut surface is photon-polished to be used as a total reflection mirror.