JPH05267408A - Electric field detector - Google Patents

Abstract

(57) [Abstract] [Purpose] The structure is equipped with a measurement probe for easy use of electric field measurement by the optical pulse sampling method. [Structure] A portion which requires optical precision is previously made into a solid solid structure as a probe, and this probe and a main body device on which a light source and a light receiving means are mounted are connected by a flexible optical fiber. [Effect] Since the probe is operated manually and the tip of the probe is brought into contact with the electrode to be measured, a troublesome device such as a fine movement stage is not required, and extremely high-speed phenomena can be performed simply like a general oscilloscope. It can be observed and the electric field strength can be measured stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used for measuring the electric field strength on an electric circuit. In particular, the present invention relates to an electric field intensity detection technique by light modulation using an electro-optical element.

[0002]

2. Description of the Related Art Recently, in the field of laser, a few picoseconds (p
s, 10 ^-12 seconds) to several femtoseconds (fs, 10
It is becoming possible to obtain a light pulse of ^-15 seconds). An optical sampling device uses this optical pulse as a sampling pulse of a sampling oscilloscope, and it is possible to measure a high-speed signal that cannot be measured by a conventional electrical method. Further, since it is not necessary to bring a probe or the like into contact with the element to be measured, it is possible to perform measurement without affecting the element.

A conventional example will be described with reference to FIG. FIG. 6 is a block diagram of a conventional device.

Since it is impossible to process a measured high-speed electric signal in real time, a sampling method is generally used as a low-speed phenomenon.

The principle of the sampling method will be described with reference to FIG. FIG. 7 is a diagram for explaining the principle of the sampling method.

Sampling is performed by shifting the repetition frequency (f) of the drive circuit of the circuit to be measured slightly (Δf) from the repetition frequency (f ₀ ) of the laser pulse. As a result, a part of the repetitive waveform is sequentially shifted and extracted, and the original waveform is reproduced at the frequency Δf. When this is expressed by an equation, f = n × f ₀ + Δf (n is an integer). The time resolution of the sampling method is determined by the time width of the signal from which the waveform is extracted, that is, the pulse width of the light (this series of operations is similar to the conventional sampling oscilloscope).

The principle of detecting the electric field strength by the electro-optical effect will be described with reference to FIG. FIG. 8 is a diagram for explaining the principle of detecting the electric field strength by the electro-optical effect.

The principle of detecting the electric field strength utilizes the fact that the plane of polarization of light changes due to the electro-optic effect. Figure 8 (a)
Then, the pulsed light from the pulsed light source passes through the polarizer and is applied to the circuit under measurement. Here, the measured circuit is GaAs or In
If it is made of a material having an electro-optical effect such as P, it changes the plane of polarization of the emitted light if the circuit is in an operating state. Therefore, the reflected return light has a polarization plane different from that of the incident light. This component is detected by a polarizer (this is called the direct probe method).

FIG. 8 (b) shows an example of the configuration in the case where the circuit to be measured is a material such as silicon having no electro-optical effect. Lithium tantalate (LiTaO ₃ ) and KTP (K
A crystal material having an electro-optical effect such as TiOPO ₄ ) is placed near the circuit to be measured, and its leak electric field is similarly measured by an optical pulse (non-contact probe method).

[0010]

However, in the direct probe method, the substrate is not limited to InP or GaAs, and the back surface of the substrate does not block light with electrodes or the like.
Moreover, it must be an optically polished surface, and there is a problem that it can be used only for measuring elements having a limited structure.

Further, the non-contact probe method is a practical method without the restrictions as in the direct probe method. But,
At present, this probe is designed to measure a part of an integrated circuit. Therefore, precise position adjustment between the probe and the circuit under measurement is required, and a precision mechanism such as a fine movement stage is required.

However, when measuring an electrode portion prepared in advance, the adjustment mechanism such as the fine movement stage rather impairs the operability, so that it is not necessary to perform manual or strict position adjustment like a general oscilloscope probe. A moveable probe is desired. The present invention has been made against such a background, and an object of the present invention is to provide a small-sized electric field detection apparatus which has high operability and which is manually operated or does not require strict position adjustment by an optical sampling method.

[0013]

According to the present invention, a polarizer, a wave plate, an electro-optical element exposed to an electric field to be measured, and a light-reflecting surface are arranged on the optical axis in the order described above. An optical element is provided with an electrode, an input optical circuit for guiding the input light from the light source to the light input surface of the polarizer, and an output optical circuit for guiding the output light appearing on the light output surface of the polarizer to the light receiving means. In the electric field detecting device, the polarizer, the wave plate, the electrode, the electro-optical element, and the light-reflecting surface are integrated as a probe so that the electro-optical element is located near the tip thereof, and the input The optical circuit for output and the optical circuit for output include optical fibers for connecting the light source and the probe, and the probe and the receiving means, respectively, and a part of an optical fiber for measuring the electric field to be measured is provided at the tip of the probe. Guide to contact Wherein the body layer is provided.

It is desirable that the electrodes are arranged perpendicular to the optical axis and that the light transmitting portion is missing or transparent.

Further, it is desirable that the electrode is connected to a reference potential.

Further, an air layer may be provided between the conductor layer and the electro-optical element.

The conductor may be formed in a triangular pyramid shape.

The conductor may be formed in a disc shape.

The electro-optical element may be formed in a trapezoidal shape.

The reflective surface may be provided on the conductor.

[0021]

A polarizer, a wave plate, an electro-optical element and a light-reflecting surface, which require optical precision, are integrally formed as a probe into a solid structure in advance, and a main body device having a built-in light source and light receiving means is provided. Can be used by connecting it with a flexible optical fiber and directly contacting the probe with the object to be measured.
A fine movement stage and other precision machinery are not required for the measurement, and the probe can be manually operated and used easily.

The optical pulse sent from the main body of the device is guided to the optical fiber for incidence and is incident on the probe connected to the electric field detecting device by the optical fiber.
It reaches the probe tip through the wave plate.

The probe tip portion includes an electrode connected to the electrode to be measured through a power source of a reference potential, an electro-optical element,
It is composed of contact parts.

The light pulse is incident on the electro-optical element placed in the electric field to be measured generated between the electrode to be measured and the fixed electrode, and is reflected by the light reflecting surface provided on the back surface of the incident surface or the contact portion. It is reflected back.

The contact portion is made of a conductor, and the potential of the electrode to be measured with which the contact portion is in contact is guided as it is into the probe. Therefore, by preparing a contact portion having a shape suitable for any shape of the electrode to be measured, the potential of the electrode is introduced into the probe as it is and the potential provided from the electrode to be measured and the electrode provided on the electro-optical element are measured. An electric field to be measured can be formed between the two.

Due to the electro-optical effect of the electro-optical element, the polarization plane of the light pulse is phase-difference modulated at a rate according to the electric field strength.

This phase difference-modulated light pulse returns to the polarizer that first passed through it, but since the polarizer has the property of transmitting only the light of a specific polarization plane, it is phase difference modulated due to the effect of the electro-optic effect. The light pulses are intensity-modulated here.

The intensity-modulated optical pulse is made incident on the optical fiber for emission and is guided to the light receiving element of the apparatus main body. In the main body of the apparatus, the electric field strength is measured by knowing the rate of change of the polarization plane by comparing the intensity of the optical pulse sent and the intensity of this return light.

In addition to using a mirror provided in the polarizer for inducing an optical pulse in the emission optical fiber as a half mirror and causing the light to enter the emission optical fiber, a half in the polarizer is used. There is also a method in which the return light transmitted through the mirror is made incident on another emission optical fiber and made incident on the apparatus main body. It is well known that this return light has an opposite phase to the above-mentioned return light from the relationship between the back of the mirror and the front. On the other hand, it is possible to detect and remove the noise component from the signal by utilizing the fact that the noise component entering from the unspecified portion has the same phase.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the first embodiment of the present invention.

According to the present invention, the polarizer 5, the wave plate 6, the electro-optical crystal 8 as an electro-optical element exposed to the electric field 12 to be measured, and the light reflecting surface 9 are arranged on the optical axis in the above order. Was
The electro-optic crystal 8 is provided with an electrode 7, and an input optical circuit for guiding the input light from the light source to the light input surface of the polarizer 5 and an output optical circuit for guiding the output light appearing on the light output surface of the polarizer 5 to the light receiving means. In the electric field detection device including an optical circuit, the polarizer 5, the wave plate 6, the electrode 7, the electro-optic crystal 8 and the light reflection surface 9 are integrated as a probe so that the electro-optic crystal 8 is located near the tip thereof. The input optical circuit and the output optical circuit include optical fibers 1 and 3 for connecting the light source and the probe and the probe and the receiving means, respectively, and a measured electric field 12 is provided at the tip of the probe. It is characterized in that a contact portion 10 as a conductor layer for contacting a part of the electrode 11 to be measured as an object to be generated is provided.

The electrode 7 is arranged perpendicularly to the optical axis and lacks a light transmitting portion or is transparent.

Further, the electrodes are connected to a power source 20 having a reference potential.

Further, an air layer 13 is provided between the contact portion 10 as a conductor layer and the electro-optic crystal 8.

Next, the operation of the first embodiment of the present invention will be described.

The pulsed light passes through the optical fiber 1 and the lens 2
Then, it becomes parallel light, and passes through the polarizer 5 and the wave plate 6 to enter the electro-optic crystal 8. The two wave plates 6 are half
The wave plate and the quarter wave plate give a phase difference to the respective incident light pulses, but the half wave plate functions to optimize the polarization plane of the light and the orientation of the electro-optic crystal 8. The quarter-wave plate serves to optically bias the operating point of modulation of the optical modulator.

An electrode 7 is provided on the electro-optic crystal 8 and is connected to the electrode 11 to be measured via a power source 20 by grounding. The electrode 7 is a transparent electrode and transmits an optical pulse.

On the other hand, the apex of the triangular pyramid of the contact portion 10 formed in the triangular pyramid shape is in contact with the electrode 11 to be measured which is to measure the voltage. Therefore, the potential of the electrode 11 to be measured is directly introduced into the probe by the contact portion 10.
Between the contact portion 10 and the electrode 7 of the electro-optic crystal 8,
The measured electric field 12 is generated. Therefore, the phase difference of the light pulse passing through the electro-optic crystal 8 is further changed according to the electric field strength, and as a result, the plane of polarization is changed. The light pulse is on the light reflecting surface 9 on the other side of the electro-optic crystal 8.
And then enters the optical fiber 3 from the wave plate 6 and the polarizer 5 through the lens 4 again. This light is detected by the light receiving element. The intensity of light guided to the optical fiber 3 is proportional to the electric field intensity, and the electric field intensity of the electrode 11 to be measured can be measured using this. This operation is the same as that of the optical modulator using the electro-optic crystal 8 and is well known, so a detailed description thereof will be omitted (the dotted line in the drawing indicates a cross section of the frame which is integrated as a whole). is there).

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram of the second embodiment of the present invention.

The second embodiment of the present invention is an example in which the air layer 13 is omitted. Since the distance from the electrode 7 and the contact portion 10 that guides the potential from the electrode 11 to be measured becomes short, the electro-optic crystal 8
The electric field strength applied to the
Impedance decreases for AC signals. Therefore, the measurement is limited to the measurement object that does not affect the operation even when the probe is in contact.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of the third embodiment of the present invention.

In the third embodiment of the present invention, the shape of the contact portion 10 is changed from a triangular pyramid shape to a disk shape, and the electrode 11 to be measured and the contact portion 10 are made.
Increase the contact area and reduce the contact pressure. It is suitable for measurements on soft or brittle materials that cannot be damaged or damaged by pin contact.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram of the fourth embodiment of the present invention.

In the fourth embodiment of the present invention, the electric field direction is orthogonal to the light direction inside the electro-optic crystal 8. As for the advantage of this method, various substances used for the electro-optic crystal 8 have been confirmed, but among them, there is one in which the electric field detection sensitivity is improved by the configuration in which the electric field and the light direction are orthogonal to each other. For this reason, it is desirable to use optimum directions for the direction of the electric field and the direction of the light depending on the properties of the electro-optic crystal 8. From this point of view, the method of the third embodiment of the present invention is useful.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram of the fifth embodiment of the present invention.

In the fifth embodiment of the present invention, signal detection is performed by differential detection. The return light from the electro-optic crystal 8 is split into two by a half mirror in the polarizer 5. Both of these components are made incident on the optical fibers 3 and 14, respectively, converted into electric signals by the light receiving elements, and the difference between the two is taken as a detection signal. The return light that enters the optical fiber 3 and the return light that enters the optical fiber 14 have a relationship between the back and front of the mirror in the half mirror in the polarizer 5 and the signals have opposite phases, but the noise components have the same phase. Therefore, by taking the difference, only the noise component of light can be canceled. Therefore, there is an advantage that instability of the pulse light source and noise components generated in the optical fiber 1 can be canceled.

The circuit configuration of the receiving side is shown in FIG. The light from the optical fibers 3 and 14 is received by the light receiving elements 15 and 15 '.
Is input to the detection signal output terminal 18. The remaining signal is output from the detection signal output terminal 18.

Regarding the first to fifth embodiments of the present invention,
The half-wave plate can be omitted if the rotation angles of the electro-optic crystal 8 and the polarizer 5 are optimally selected. This is because the half-wave plate is for optimizing the polarization plane and the orientation of the electro-optic crystal 8, and can be omitted by setting the orientation in advance to the optimum orientation.

Although the light reflecting surface 9 is one surface of the electro-optic crystal 8, the light reflecting surface may be provided on the contact portion 10 or on the other surface.

Either the lens 2 or the lens 4 may be used. Generally, the optical fiber 1 uses a single mode fiber, but the optical fibers 3 and 14 use a fiber having a large core diameter. There are advantages such as low loss and a large positional deviation tolerance. Therefore,
Since there is a difference in core diameter, the lens 4 may be omitted.

The electrode 7 of the electro-optical crystal 8 is not a transparent electrode but may have a shape in which a hole is formed only in a portion through which light passes, and the electrode 7 may be provided on the side surface of the electro-optical crystal 8.

[0052]

EFFECTS OF THE INVENTION The electric field strength detection by the optical sampling method, which has been used only for a special purpose, requires an optical precision because it requires a fine movement stage and other precision machines for the measurement, and it takes time to prepare for the measurement. A polarizer that requires high precision,
The wave plate, the electro-optical element and the light reflecting surface are integrally configured as a probe in a solid structure in advance, and the light source and the light receiving means are connected by a flexible optical fiber to the main unit.
Since the probe can be used by directly contacting the object to be measured, it can be used like a probe of a general oscilloscope.

Further, since the contact portion is brought into contact with the electrode to be measured, the electric field strength can always be stably measured. The contact portion is made of a conductor, and the potential of the electrode under measurement with which the contact portion is in contact is directly introduced into the probe of the contact portion. Therefore, by preparing a contact portion having a shape suitable for any shape of the electrode to be measured, it becomes possible to guide the potential as it is into the probe to generate an electric field to be measured and perform measurement.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment device of the present invention.

FIG. 3 is a configuration diagram of an apparatus according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a fourth embodiment device of the present invention.

FIG. 5 is a configuration diagram of a fifth embodiment device of the present invention.

FIG. 6 is a block diagram of a conventional device.

FIG. 7 is a diagram illustrating the principle of an optical sampling method.

FIG. 8 is a diagram for explaining the principle of detection of electric field strength by the electro-optic effect.

[Explanation of symbols]

 1, 3 and 14 Optical fiber 2 and 4 Lens 5 Polarizer 6 Wave plate 7 Electrode 8 Electro-optic crystal 9 Light reflecting surface 10 Contact part 11 Measured electrode 12 Measured electric field 13 Air layer 15, 15 'Light receiving element 16, 16 'Amplifier 17 Arithmetic circuit 18 Detection signal output terminal 20 Power supply

Claims (4)

[Claims] 1. A polarizer, a wave plate, an electro-optical element exposed to an electric field to be measured, and a light-reflecting surface are arranged in this order on an optical axis, and the electro-optical element includes an electrode. In an electric field detection device comprising an input optical circuit for guiding the input light from the light source to the light input surface of the polarizer, and an output optical circuit for guiding the output light appearing on the light output surface of the polarizer to the light receiving means, The polarizer, the wave plate, the electrode, the electro-optical element, and the light-reflecting surface are integrated as a probe so that the electro-optical element is located near the tip thereof, and the input optical circuit and the output light are provided. The circuit includes an optical fiber that connects the light source and the probe, and the probe and the receiving unit, respectively, and a conductor layer for contacting a part of the probe with an object that generates an electric field to be measured is provided at a tip of the probe. Was given Characteristic electric field detection device. 2. The electric field detecting device according to claim 1, wherein the electrode is arranged perpendicularly to the optical axis, and a light transmitting portion is absent or transparent. 3. The electric field detecting device according to claim 1, wherein the electrode is connected to a reference potential. 4. The electric field detecting device according to claim 1, wherein an air layer is provided between the conductor layer and the electro-optical element.