KR860000389B1 - Electric field detector - Google Patents

Abstract

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Description

Electric field detector

1 is a basic configuration of the electric field detection device.

2 is a block diagram of the present invention electric field detection device.

3 is a temperature characteristic diagram of polarization plane variation of 45 ° -z cut crystal.

4 is a temperature characteristic diagram of polarization plane variation of a Pockgels element in the present invention electric field detection device.

5 is a configuration diagram of an entire detection apparatus according to the present invention.

6 (a) and 6 (b) are a plan view and a front view, respectively, in which a cut state of a z-cut crystal is used for the Pockgels element according to the present invention.

7 is a temperature characteristic diagram of polarization plane fluctuations of the phogel gel device according to the present invention.

8 is an explanatory diagram of the Foxgels effect.

Fig. 9 is an explanatory diagram of incident light and an outgoing light of the Foxgels element.

FIG. 10 is an explanatory diagram of incident light and an outgoing light of the Foxgels element. FIG.

* Explanation of symbols for main parts of the drawings

4 analyzer 5 detection unit

9: H _e -H _e laser 11: Foxkels element (z-cut modification)

12: 1/4 wave plate

The present invention relates to a field detection device.

1 shows a basic configuration of an electric field detection device, (1) a light emitting portion such as a forward diode, (2) a polarizer for linearly polarizing light of front vibration in the light emitting portion (1) in a horizontal or vertical direction. (3) denotes a Foxels device in which the electric field E is applied in the vertical direction or the horizontal direction (the direction of the electric field E is determined by the crystal axis of the Foxels element 3). 3), when the electric field E is applied, the polarization plane of the polarization from the polarizer 2 rotates. In other words, when the electric field is applied, the difference between the refractive indices in the plane perpendicular to the electric field (xz plane) and the plane perpendicular to the electric field (yz plane) results in a difference in the phase of light components on these surfaces. The synthesized light becomes a towel polarized light in which the polarization plane rotates. Since the difference in refractive index is proportional to the magnitude of the electric field E (Pockkels effect), the phase difference is proportional to the magnitude of the electric field E. Reference numeral 4 denotes an analyzer having a polarization plane in a right angle or parallel relationship with the polarization plane of the polarizer 2, and the analyzer 4 receives light from the Foxkels element 3. Denoted at 5 is a detector that receives the light transmitted through the analyzer 4 and emits an electric signal in accordance with the amount of light. Therefore, when the polarization planes of the polarizer 2 and the analyzer 4 are at right angles, the electric field E becomes large, so that in the Foxels element 3, the components of the light of the xz plane and the light of the yz plane Since the phase difference 4 of the component becomes large, the amount of transmitted light of the analyzer becomes large, and the output of the detector 5 also becomes large.

In this regard, as shown in Fig. 8, light having only oscillation plane os (called linear polarization or planar polarization) is incident to be inclined at 45 ° with respect to the x and y axes of the crystal. The oscillation of oscillation oscillation is divided into xz plane and yz plane. On the incident surface, as shown in Fig. 9, the phases of vibration of both planes are the same, but in the crystal, the phase difference?

Therefore, as shown in FIG. 10, when the single vibration of the xz plane and the single vibration of the yz plane, which make the phase difference Ø, are combined in the emission plane, the elliptical polarization becomes different from the linear polarization in the incident plane.

When a voltage is applied to both the incidence plane and the outgoing plane of the crystal as shown by the dotted line in FIG. 10, dielectric polarization occurs in the crystal, and the refractive indices of the xz plane and the yz plane change. Therefore, the light at the exit surface becomes elliptical polarization as described above. Since this change in refractive index is proportional to the applied voltage, the voltage can be measured using this property.

For example, in the case where a polarizer is provided on the incidence side of the Foxkels element and the analyzer is installed on the exit side of the Foxkels element so as to be orthogonal to the optical axis of the polarizer, the analyzer is orthogonal to the os. Linearly polarized light vibrating is obtained.

As shown in FIG. 10, when the running voltage increases, the electric phase difference becomes large and the ellipse is in an expanded state, so the light quantity of the linearly polarized light from the analyzer becomes large, and thus the voltage applied based on the light quantity is increased. You can get it. In addition, when the polarizer planes of the polarizer 2 and the analyzer 4 are parallel to each other, as the electric field E increases, the amount of light passing through the analyzer 4 decreases, and the output of the detector 5 also decreases. In this way, the magnitude of the electric field E can be detected from the output of the detector 5, that is, the transmission amount of the analyzer 4.

However, in the conventional electric field detection device, KDP (KH ₂ PO ₄ ) or ADP (NH ₄ H ₂ SO ₄ ) is used as the Pockels element 3, but these are handled because of their high cost and degradability. This is very difficult. In addition, KDP and ADP are susceptible to disturbing the electric field due to the large dielectric constant (about 10 times of the quartz crystal), and easily cause errors in electric field measurement. On the other hand, if the crystal is used as a Foxells element, the crystal does not disturb the electric field due to the low dielectric constant, so the electric field measurement is accurate, and the crystal is cheap and easy to obtain. In addition, crystals are easy to handle with extremely stable crystals with constant light loss and no deliquescent properties.

However, the crystal has a so-called natural beneficiation property that when the linearly polarized light is incident on the light side direction, the polarization plane rotates regardless of the electric field. On the other hand, since the natural photorefractive property has a temperature characteristic, the precision and reliability of the electric field detection device are insufficient when the crystal is used as a Pockels element.

There, in Japanese Patent Application No. 56-46668, two modifications (6) and (7) having almost left and right symmetrical natural beneficiation with respect to temperature change, as shown in FIG. It was proposed to form the Foxells element 8 by sneaking in. Moreover 9 is in this case since the polarizer with H _{e e} -N laser (LASER) for generating a linearly polarized light is not required polarization from the laser 9 is added to the line width Kells element 8.

However, in the overall detection apparatus shown in FIG. 2, a 45 ° -z cut crystal, which is generally used as the crystal (6) and (7), is used, and the temperature characteristic (one crystal) of the polarization plane variation is shown in FIG. In addition, in FIG. 2, when the Pockels element 8 is put in the thermostat 10 and the temperature characteristic of the polarization fluctuation | variation is measured, it is as shown in FIG. 4, and the temperature of 20 degreeC-90 degreeC There is about 3% variation in the range.

This is because it is difficult to find two modifications with temperature characteristics of polarization plane variation of completely symmetry.

In addition, since the measurement of this temperature characteristic requires a long time, even if two crystals with almost bilateral symmetrical temperature characteristics are found, they are extremely lost. In the Foxells element 8, the phase difference between the light component in the xz plane and the light component in the yz plane is not only proportional to the electric field but also proportional to the element length in the optical axis direction.

The reason that the above phase difference is proportional to the element length is that the phase difference is δ, the wavelength is λ, each refractive index is n _o , n _e , and the element length is d.

Because it becomes.

Since 45 ° -z cut crystals are not sufficiently good in the field detection accuracy, it is necessary to lengthen the crystal length in order to improve the sensitivity, and the Foxkels element 8 has two crystals 6 and 7 in series. Because it was in close contact, it becomes large.

In order to bring the two crystals 6 and 7 into close contact so that no air layer is interposed therebetween and there is no optical problem, polishing of extremely high precision is required and manufacturing is inconvenient.

It is an object of the present invention to provide an electric field detection device which is easy to manufacture and compact, and has a high accuracy and high reliability by eliminating the aforementioned drawbacks.

Embodiments of the present invention will be described below with reference to the drawings.

5 shows the electric field detecting device according to the present embodiment, and in this embodiment, the Z-cut (optical direction cut) cut as shown in FIGS. 6 (a) and 6 (b) as the Foxkels element 11 or FIG. Almost uses a modification of zcut.

In the above-mentioned electric field sensor device, the linearly polarized light generated in the H _{e e} -N laser 9 is added to the width Kells element 11 either directly or through the quarter-wave plate 12. When the linearly polarized light is directly applied to the Foxkels element 11, the direction of the electric field E applied to the Foxkels element 11 is limited to its x direction, but the linearly polarized light is directly or quarter-wave plate 12 In the case where it is applied to the Foxkels element 11 through, the linearly polarized light is converted into circularly polarized light. In this case, the direction of the electric field E applied to the Foxkels element 11 may be any of x, y, and z directions. In either case of linearly polarized light or circularly polarized light, polarized light is transmitted in the z direction of the Foxkels element 11 (z-cut or almost z-cut crystal). In the Foxkels element 11, the polarization plane of polarization rotates by applying an electric field (E).

In other words, as mentioned above, a phase difference occurs between the component of the xz plane and the component of the light of the yz plane, which causes the light transmitted through the Foxels element to become an elliptical polarization in which the polarization plane rotates.

The polarized light then passes through the analyzer 4, but the analyzer 4 has a polarization plane which has a predetermined relationship with the polarization plane of the polarization generated by the laser 9, so that the electricity is eventually According to one phase difference, the amount of transmitted light of the analyzer 4 changes, and accordingly, the output of the detection unit 5 which emits an electric signal changes according to the amount of light.

Therefore, it is possible to detect the magnitude of the electric field E at the output of the detector 5. The specific example of this detection method can be performed based on the output of a detection part, as already mentioned using FIG. 9, FIG.

Here, when the Pockels element 11 is placed in the thermostat 10, and the characteristic of the polarization plane variation (the variation due to the natural optical polarization of the crystal and not depending on the electric field) is measured as shown in FIG. The variation is almost zero, within the range of the measurement error. For this reason, the output of the electric field E and the detection part 5 correspond exactly, and the electric field detection apparatus of high accuracy and reliability can be obtained. In addition, since the crystal of z-cut or nearly z-cut has an electric field detection sensitivity of 4 times stronger than that of 45-z cut, the element length can be made about 1/4 of the conventional length. The Foxels element 11 can be shaped in one crystal to make the Foxels element 11 and the entire device compact.

Furthermore, the laser 9 can be replaced with a light emitting part and a polarizer which emits light of front vibration.

As described above, in the entire detection apparatus of the present invention, the Foxkels element is formed by the crystal of z cut or almost z cut, and the crystal of z cut or almost z cut is applied to the electric field because the variation is almost zero depending on the temperature of the polarization plane. It is possible to obtain an accurate and highly reliable electric field detection device capable of accurately detecting the magnitude of the electric field in the amount of transmitted light of the analyzer, since it can be seen that the transmitted light amount of the analyzer and the analyzer accurately correspond to each other.

In addition, the z cut or almost z cut crystal has a good electric field detection sensitivity, so the length thereof can be shortened, and since the Foxkels element is formed of one crystal on it, it can be made compact and the whole apparatus can be made compact. . In addition, the Pockkels element is made of one crystal, eliminating the trouble of finding two crystals having almost symmetrical temperature characteristics, and it is easy to fabricate because the two crystals do not need to be closely adhered optically. In addition, by using a modification without using a conventional KDP or ADP as a Foxells device, the following effects are obtained.

(A) It is easy to process at low price, and the crystal is stable and easy to handle because it has constant light loss (reflection loss + absorption loss) at light transmission and no deliquescent property. (B) Since the crystal is not deliquescent, there is no need for sealed storage, the structure is simple, and the durability and reliability are improved. (C) Since the crystal has a low permittivity, the electric field detection is accurate with almost no influence on the electric field.

Claims (1)

Means for generating linearly polarized or circularly polarized light and a Porkkel element for transmitting the polarized light in the z-direction or the crystal of z-cut or almost z-cut to rotate the polarized plane of the polarized light according to the magnitude of the electric charge; An electric field detection device comprising an analyzer that transmits light transmitted through a Foxelx element and detects the magnitude of the electric field according to the amount of light transmitted by the analyzer.

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