JPS63308586A - Evaluating system for voltage detector - Google Patents

Abstract

PURPOSE:To enable the performance of a voltage detector for the ultrahigh speed voltage change of an object to be measured to be evaluated with a high reliability by making pulsed light with a pulse width shorter than several hundred f.sec incident upon an electrooptical material. CONSTITUTION:Pulsed light with a pulse width shorter than several hundred f.sec is incident upon an electro-optical material 62 in a condition wherein it is applied with no voltage from a f.sec laser 2 in parallel to the light path of incident light from a light source 53. As a result, an electromagnetic wave EM with the pulse width shorter than several hundred f.sec is transmitted through the material 62 toward a reflecting mirror 65 and the refractive index of the material 62 changes only for a time shorter than several hundred f.sec. Due to refractive index change thus generated, the polarization components of the incident light from the light source 53 passing a polarizer 54 and of emitted light to a streak camera 7 change and only the emitted light with a prescribed polarization component is extracted by an analyzer 57 to be incident upon the camera 7. Thus, since the emitted light from the light source 53 proceeds pursuant to the refractive index change and an interaction is elongated, polarization component change is increased and the performance of a voltage detector 1 can be evaluated by the camera 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method of detecting voltage by utilizing the fact that the polarization state of light changes depending on the voltage of a predetermined part of an object to be measured, such as an electric circuit. The present invention relates to a voltage detection device evaluation system that evaluates the performance of a voltage detection device.

[Conventional technology]

Conventionally, various voltage detection devices have been used to detect the voltage of a predetermined portion of an object to be measured such as an electric circuit. This type of voltage detection device is of the type that detects the voltage at a predetermined portion of the object to be measured by contacting the probe with the predetermined portion of the object to be measured, or the type that detects the voltage of that portion by making the probe contact the predetermined portion of the object. Types that detect the voltage at certain points are known.

By the way, there is a desire among those skilled in the art to accurately detect the rapidly changing voltage of a minute part of an object to be measured, such as a small integrated circuit with a complex structure, without affecting the state of the minute part. There is a strong demand.

However, in a voltage detection device that brings the probe into contact with a predetermined part of the object to be measured, it is not easy to bring the probe into direct contact with minute parts such as integrated circuits, and even if it is possible to bring the probe into contact, It has been difficult to accurately analyze the operation of integrated circuits based only on the voltage information. Furthermore, there is a problem in that the operating state within the integrated circuit changes when the probe comes into contact with the integrated circuit.

In addition, with a voltage detection device that uses an electron beam, it is possible to detect voltage without bringing the probe into contact with the object to be measured, but this is limited to devices where the part to be measured is placed in a vacuum and exposed. There was also the problem that the part to be measured was damaged by the electron beam.

Furthermore, with conventional voltage detection devices, the operating speed of the detector cannot follow high-speed voltage changes. There has been a problem in that it is not possible to accurately detect voltages that change rapidly in product circuits and the like.

[Problem that the invention seeks to solve]

In order to solve these problems, the polarization state of the light beam changes depending on the voltage at a predetermined part of the object to be measured, as described in a patent application filed May 30, 1986 by the inventors. A type of voltage detection device that detects voltage using

FIG. 4 is a block diagram of a voltage detection device of the type that detects the voltage of the object to be measured by utilizing the fact that the polarization state of the light beam changes depending on the voltage of a predetermined portion of the object to be measured.

In FIG. 4, the voltage detection device 50 includes an optical probe 52, a DC light source 53 such as a laser diode, and an optical fiber 51 that guides the light beam output from the DC light source 53 to the optical probe 52 via a condensing lens 60. and reference-5 from the optical probe 52 = optical fiber 92 that guides illumination light to the photoelectric conversion element 55 via the collimator 90 and guides the emitted light from the optical probe 52 to the photoelectric conversion element 58 via the collimator 91 It is composed of an optical fiber 93 and a comparison circuit 61 that compares the photoelectrically converted electrical signals from the photoelectric conversion elements 55 and 58.

The optical probe 52 includes an electro-optic material f462, such as optically-axial crystal lithium tantalate (L i Ta
O3) is accommodated in the tip 6 of the electro-optic material 62.
3 is processed into a truncated conical shape. Optical probe 52
A conductive electrode 64 is provided on the outer periphery, and a reflective mirror 65 made of a thin metal film or a dielectric multilayer film is attached to the tip 63.

The optical probe 52 further includes a collimator 94, condensing lenses 95 and 96, a polarizer 54 for extracting only a light beam having a predetermined polarization component from the light beam from the collimator 94, and a predetermined polarization component from the polarizer 54. The electro-optic material 6 is split into a reference beam and an incident beam.
A beam splitter 56 is provided to make the emitted light from the analyzer 2 enter the analyzer 57. The reference light and output light are
Optical fibers 92 through condensing lenses 95 and 96, respectively.
．． 93.

In the voltage detection device 50 having such a configuration, during detection, the conductive type f! 6
4 is held at a ground potential, for example.

Next, the tip 63 of the optical probe 52 is brought close to an object to be measured, for example, a product circuit (not shown). As a result, the refractive index of the tip 63 of the electro-optic material 62 of the optical probe 52 changes. More specifically, in an optically axial crystal or the like, the difference between the refractive index of ordinary light and the refractive index of extraordinary light in a plane perpendicular to the optical axis changes.

The light beam output from the light source 53 is passed through a condenser lens 60 .
Collimator 9 of optical probe 52 via optical fiber 51
4, and is further turned into a light beam of a predetermined polarization component with an intensity 2 by a polarizer 54, and enters the electro-optic material 62 of the optical probe 52 via a beam splitter 56. Note that the intensity of the reference light and the incident light split by the beam splitter 56 is π/2. Since the refractive index of the tip 63 of the electro-optic material 62 changes depending on the voltage of the object to be measured as described above, the polarization state of the incident light incident on the electro-optic material 62 at the tip 63 depends on the change in the refractive index. changes, reaches the reflecting mirror 65, is reflected by the reflecting mirror 65,
The electro-optic material 62 directs the emitted light to the beam splitter 56 again.

Assuming that the length of the tip 63 of the electro-optic material 62 is 1, the polarization state of the incident light is determined by the refractive index difference between the ordinary light and the extraordinary light due to the voltage and the length 2! It changes in proportion to J.

The emitted light returned to the beam splitter 56 is sent to an analyzer 57.
incident on . The intensity of the emitted light incident on the analyzer 57 is set to π/4 by the beam splitter 56. For example, if the analyzer 57 is configured to pass only a light beam with a polarization component orthogonal to the polarization component of the polarizer 54, the polarization state changes and the output of intensity I/4 that enters the analyzer 57 The intensity of the emitted light is determined by an analyzer 57 to be (π/
4).2s+n[:(π/2)-v/vo:] and is applied to the photoelectric conversion element 58. Here, V is the voltage of the object to be measured, and Vo is the half-wavelength voltage.

In the comparison port 1161, the intensity I/2 of the reference target photoelectrically converted in the photoelectric conversion element 55 and the intensity I/2 of the output light photoelectrically converted in the photoelectric conversion element 58 2 (π/4)-s+n I: (π/ 2) V/Vo) is compared.

Intensity of output light (π/4) −5in” [: (π
/2>v/vo] is the electro-optic material 6 due to voltage change.
Since the voltage changes depending on the change in the refractive index of the tip 63 of No. 2, the voltage at a predetermined portion of the object to be measured, for example, an integrated circuit, can be detected based on this.

In this manner, the voltage detection device 50 shown in FIG. Since the voltage of a predetermined part of an object is detected, the optical probe 52 detects the voltage of a minute part of an integrated circuit, which is difficult to contact, and which would affect the voltage to be measured if brought into contact. can be detected without contact. In addition, a pulsed light source such as a laser diode that outputs light pulses with a very short pulse width may be used as a light source to sample the high-speed voltage changes of the measured object over a very short time width, or a DC light source may be used as the light source. By using a high-speed response detector such as a streak camera as the detector to measure high-speed voltage changes of the object to be measured with high time resolution, it becomes possible to detect high-speed voltage changes with high accuracy.

By the way, in the voltage detection bag W50 shown in FIG. 4, a CW laser such as a laser diode or a helium neon laser, that is, a DC light source is used as the light source 53, and a high-speed response detector such as a streak camera is used as the detector to detect high-speed voltage. When trying to detect a change, the voltage detection device 50
It is necessary to test and evaluate how fast a voltage change can be detected.

As a conventional evaluation system, the short pulse width is -1n.
- The voltage detection device 50 was evaluated by applying an electrical voltage pulse for evaluation to the electro-optic material 62 and determining whether the voltage pulse could be detected as a streak image of a predetermined width by a streak camera. However, the pulse width of the electrical voltage pulse cannot be made shorter than 10 picoseconds, so in a system that uses electrical voltage pulses as evaluation pulses, ultra-high-speed voltage changes of the measured object on the order of femtoseconds are required. There was a problem in that it was not possible to evaluate the performance of

An object of the present invention is to provide an evaluation system for a voltage detection device that is capable of reliably evaluating the performance of an object to be measured with respect to ultra-high-speed voltage changes.

[Means for solving problems]

The present invention provides an evaluation system for evaluating the performance of a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of an object to be measured. A femtosecond laser that outputs pulsed light with a pulse width of OO fem l~ seconds or less, and causes an instantaneous change in the refractive index within the electro-optical material of the voltage detection device for an extremely short period of time due to the optical Cerenkov effect caused by this pulsed light. The present invention aims to improve the problems of the prior art described above by providing an evaluation system for a voltage detection device characterized by comprising:

[Effect]

In the present invention, the performance of a voltage detection device that uses, for example, a CW laser as a light source and uses, for example, a streak camera as a detector, is evaluated. For this purpose, for example, a femtosecond laser such as a CPM link dye laser that outputs pulsed light with a pulse width of femtoseconds is provided, and the pulsed light from the femtosecond laser is incident on the electro-optic material of the voltage detection device to create an optical Cherenkov. The effect causes an instantaneous and extremely short period of refractive index change within the electro-optic material.

As a result, the light beam from the light source, from which a predetermined polarization component has been extracted by the polarizer, changes its polarization state due to the change in the refractive index of the electro-optic material and is applied to the streak camera. By changing the refractive index of the electro-optic material in an extremely short pulse-like manner, the polarization state of the light beam from the DC light source changes in a pulse-like manner, and the output light with a predetermined polarization component is extracted by an analyzer. As a result, the streak camera detects a pulsed light intensity distribution. The evaluation system of the present invention evaluates whether the light intensity distribution of a streak image observed by a streak camera corresponds to pulsed light from a femtosecond laser. In other words, when the width of the detected pulsed light intensity distribution is smaller than a predetermined width, it is determined that the temporal resolution of the voltage detection device is good, and when it is larger than the predetermined width, the voltage detection device determines that the temporal resolution is good. It is judged that it does not have resolution. It is also possible to evaluate the performance of a sampling-type voltage detection device that uses a pulsed laser as a light source. For example, a light pulse from a femtosecond laser such as a CPM dye ring laser is split by a beam splitter, and one light pulse is used to generate an optical Cherenkov effect, and the other light pulse is used to detect a voltage, and the light pulses are made incident on an electro-optic material.

Due to the optical Zielenkoff effect, a refractive index change occurs in the opto-electric material for a very short time, and the polarization state of the voltage detection light pulse from which a predetermined polarization component has been extracted by the polarizer changes due to this refractive index change. By adding a variable optical delay to one of the two optical pulses split by the beam splitter and changing the mutual optical path difference between the two optical pulses, the magnitude of the change in the polarization state due to the change in the refractive index of the detection light is changed. By extracting a predetermined polarized light component using an analyzer, the light intensity detected by the detector changes. That is, the refractive index change in the electro-optic material is sampled, and the voltage detection device is evaluated based on the time resolution of this sampling. In this way, by using a femtosecond laser, the voltage detection device can be appropriately evaluated.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of a first embodiment of a voltage detection device evaluation system according to the present invention.

In the voltage detection device 1 to be evaluated in FIG. 1, a CW laser, ie, a DC light source, is used as the light source 53, and a streak camera 7 is used as the detector. Only a predetermined polarized component of the light beam from the light source 53 is extracted by the polarizer 54, and enters the electro-optic material 62 in the optical probe 52 as incident light via the beam splitter 56, as described above. The refractive index of the tip 63 of the electro-optic material 62 changes depending on the voltage of the object to be measured. As a result, the incident light having a predetermined polarization component that has entered the electro-optic material 62 changes its polarization state at the tip 63 of the electro-optic material 62, is reflected by the reflecting mirror 65, and exits from the electro-optic material 62 again. It is output as emitted light. The emitted light outputted from the electro-optic material 62 is returned to the beam splitter 56 again, split by the beam splitter 56, and only the emitted light having a predetermined polarization component is extracted by the analyzer 57 and added to the streak camera 7. It has become.

FIG. 2 is a configuration diagram of the streak camera 7.

The streak camera 7 has sleeves 1 to 11 into which the emitted light extracted by the analyzer 57 enters, a lens 12 into which the emitted light via the slit 11 enters, and -1 = the outgoing light condensed by the lens 12. Photocathode 1 where incident light enters
3, a deflection electrode that laterally deflects the electron beam photoelectrically converted by the photocathode 13; 4, a microchannel plate 1-15 that multiplies the deflected electron beam; It has a fluorescent surface 16 on which the electron beam is incident. Although the microchannel plate 15 and the fluorescent surface 16 are shown separated in FIG. 2, they are usually joined together. Further, although the lens 12 is shown to have a cylindrical shape, it is not normally cylindrical.

By applying a sawtooth voltage synchronized with a predetermined electric I/rega signal TR to the deflection electrode 14 of the streak camera 7, the emitted light that is incident on the photocathode 13 in time series is deflected laterally on the fluorescent surface 16. can be swept to As a result, the fluorescent surface 16 is
2, voltage changes in a predetermined portion of the object to be measured can be detected as a one-dimensional light intensity distribution FG.

By the way, in order to evaluate the performance of such a voltage detection device 1, the femtosecond laser 2 is used with no voltage applied to the electro-optic material 62, and the equation 1 from the femtosecond laser 2 is
Pulsed light having a pulse width of 00 femtoseconds or less is made to enter the tip 63 of the electro-optic material 62 perpendicularly, that is, parallel to the optical path of the incident light from the light source 53.

As a result, electromagnetic waves EM due to the optical Cerenkov effect propagate toward the reflecting mirror 65 in the shape of a Cerenkov cone with a pulse width of several 100 femtoseconds or less, and the refractive index of the electro-optic material 62 changes to several 1. The time is changed by OO femtoseconds or less. CW laser light source 53
The polarized light component of the incident light from the source via the polarizer 54 and the polarized light component of the outgoing light to the streak camera 7 are electromagnetic waves E propagating in a Cerenkov cone shape in the electro-optic material 62.
It changes as the refractive index changes due to M, and only the emitted light with a predetermined polarization component is extracted by the analyzer 57 and added to the streak camera 7. In this first embodiment, pulsed light with a pulse width of several hundred femtoseconds or less is made incident on the electro-optic material -17=62 in parallel to the optical path of the incident light, so that the incident light from the light source 53 is electrically The interaction length can be lengthened by following the pulsed refractive index change within the optical material 62, and the change in the polarization component can be increased. It can be evaluated with good sensitivity.

Note that the pulsed light from the femtosecond laser 2 is photoelectrically converted by a photoelectric conversion element 4 via a beam splitter 3 and applied to the deflection electrode 14 of the streak camera 7 as an electric trigger signal TR. The incident and emitted light forms a streak image F on the fluorescent surface 16 of the streak camera 7 in synchronization with this electric l/rega signal TR.
Detected as G. This streak image FG, that is, the light intensity distribution, is ideal because the change in refractive index caused in the electro-optic material 62 by the pulsed light from the femtosecond laser 2 is on the order of several hundred frames per second or less. must have an extremely short brightness width.

Therefore, the evaluation system can be modified from the femtosecond laser 2 to the number 1
The brightness width of the streak image FG detected when pulsed light on the order of 00 femtoseconds or less is incident on the tip 63 of the electro-optic material 62 is detected, and when this brightness width is smaller than a predetermined width, the voltage is It can be evaluated that the detection device 1 has a high time resolution higher than a predetermined level.

On the other hand, when the brightness width of the detected streak image FG is larger than the predetermined width, it is determined that the voltage detection device 1 does not have high temporal resolution. Note that factors that reduce the resolution of the voltage detection device 1 include a defect in the electro-optic material 62 itself, or a defect in the optical path of the incident light and the outgoing light from the light source 53 to the streak camera 7. It is conceivable that the change in the polarization state of the incident light and the output light does not respond quickly to the rapid change in the refractive index, or that the change in the intensity of the incident light and the output light causes a transmission loss while traveling along the optical path.

FIG. 3 is a configuration diagram of a second embodiment of the voltage detection device evaluation system according to the present invention.

In the evaluation system of the second embodiment, a sampling type voltage detection device using a pulsed light source is evaluated as =19-. Note that the sampling type voltage detection device is similar to that shown in FIG. 4, and the same parts as in FIG. 4 are denoted by the same reference numerals and the explanation thereof will be omitted. This sampling type voltage detection device splits a light pulse from a femtosecond laser 2 into two light pulses BMI and BM2 by a beam splitter 17, uses one light pulse BM1 for voltage detection, and uses the other light pulse BM1 for voltage detection.
2 is used to generate Cerenkov cone-shaped electromagnetic waves EM.

One of the optical pulses BMI split by the beam splitter 17 is sent to the polarizer 54 via the optical variable delay means 18.
The light is incident on the electro-optic material 62 from the beam splitter 56 as incident light for voltage detection.

The other optical pulse BM2 split by the beam splitter 17 is made to enter the electro-optic material 62 via the optical variable delay means 19 for generating Cerenkov cone-shaped electromagnetic wave EMI.

- Lin - In the evaluation system with such a configuration, the optical variable delay means 18 and 19 detect the position of change in the refractive index caused by the voltage detection optical pulse BMI, Cerenkov cone-shaped electromagnetic wave, and EMl within the electro-optic material 62. By adjusting the mutual optical path lengths of the two optical pulses BMI and BM2 so that they match, and further driving either one of the optical variable delay means 18 or 19 little by little to gradually reduce the mutual optical path lengths. , the pulsed refractive index change of the electro-optic material 62 is transferred to the photoelectric conversion elements 55, 58 . Sampling measurement can be performed using the comparison circuit 61 or the like. That is, the polarizer 54
The optical pulse BMI from which only the predetermined polarization component is extracted is
It is divided by the beam splitter 56, and one side is focused by the lettuce 9.
5. Reference light R via optical fiber 92 and collimator 90
The other is added to the photoelectric conversion element 55 as EF, and the polarization state changes due to the refractive index change due to Cerenkov cone-shaped electromagnetic wave EMI in the electro-optic material 62, and the output light, that is, the signal light SG, is split by the beam splitter 56 and analyzed by the analyzer 57. ．． Condensing lens 96. Optical tV-fiber 93. Photoelectric conversion element 5 via collimator 91
Join 8. When the mutual optical path lengths of the light pulses BMI and BM2 are gradually shifted, the light intensity of the signal light SG becomes the result of sampling the pulse-like refractive index change that occurs in the electro-optic material 62, and is sampled in the photoelectric conversion element 58. The results are converted into electrical signals. The comparison circuit 61 compares the electrical signal of the signal light SG from the photoelectric conversion element 58 based on the electrical signal of the reference light REF from the photoelectric conversion element 55, thereby improving the S/N ratio and further improving the evaluation accuracy. can be improved.

In this way, the refractive index of the electro-optic material 62 can be changed over a period of time on the order of several hundred femtoseconds or less, so whether or not the voltage detection device 1 has high time resolution is tested before shipping. or inspect it before it is put into use, giving an accurate assessment.

Note that it is preferable to paint the optical probe 52, including the side wall of the tip 63 of the electro-optic material 62, black so that the light beam incident on the inner wall of the optical probe 52 is not scattered.

〔Effect of the invention〕

As explained above, according to the present invention, pulsed light with a pulse width of several hundreds of femtoseconds or less is made incident on the electro-optical material of the voltage detection device, so that ultra-high-speed voltage changes of the measured object can be achieved. The performance of the voltage detection device can be evaluated with high reliability.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram of a first embodiment of a voltage detection device evaluation system according to the present invention, Fig. 2 is a schematic block diagram of a streak camera, and Fig. 3 is a block diagram according to the present invention. FIG. 4 is a block diagram of a second embodiment of the voltage detection device evaluation system, and FIG. 4 is a block diagram of a general voltage detection device. 1... Voltage detection device, 2... Femtosecond sensor, 7
... Streak camera, 52 ... Optical probe, 62
...Electro-optical material, 63...Tip, EM, EMI
...electromagnetic waves

Claims (1)

[Claims] 1) In an evaluation system for evaluating the performance of a type of voltage detection device using an electro-optic material whose refractive index changes depending on the voltage at a predetermined portion of a measured object, a pulse width of several hundred femtoseconds or less is used. The device is characterized by being equipped with a femtosecond laser that outputs pulsed light and causes an instantaneous and extremely short refractive index change in the electro-optical material of the voltage detection device by the optical Cerenkov effect caused by the pulsed light. Evaluation system for voltage detection equipment. 2) The refractive index of the electro-optic material is changed by the optical Cerenkov effect caused by the pulsed light from the femtosecond laser, and the pulsed light is branched from the femtosecond laser and only a predetermined polarized component is extracted by the polarizer of the voltage detection device. By changing the polarization state within the electro-optic material and extracting a predetermined polarization component from the light beam whose polarization state has changed within the electro-optic material, the intensity of the emitted light is detected by a high-speed response detector of the voltage detection device. 2. The voltage detection device evaluation system according to claim 1, wherein the voltage detection device evaluation system evaluates the time resolution of the detection device. 3) The voltage detection device evaluation system according to claim 2, wherein the high-speed response detector is a streak camera. 4) The refractive index of the electro-optic material is changed by the optical Cerenkov effect caused by the pulsed light from the femtosecond laser, and the pulsed light is branched from the femtosecond laser and only a predetermined polarized component is extracted by the polarizer of the voltage detection device. The polarization state is changed within the electro-optic material, and a predetermined polarization component is extracted from the light beam whose polarization state has changed within the electro-optic material. The intensity of the emitted light is detected and sampled with a photoelectric detector of a voltage detection device. 2. The voltage detection device evaluation system according to claim 1, wherein the voltage detection device evaluation system evaluates the time resolution of the voltage detection device. 5) The voltage detection device evaluation system according to claim 4, wherein the sampling is performed by changing a relative optical path difference between two branched femtosecond laser beams.