| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect spike pulse of low voltage and short pulse width by respectively impressing a voltage signal and a voltage signal regulating this in phase on both electrodes of the pockels of an electro-optical modulator, and detecting intensity of light transmitted through the electro-optical modulator. SOLUTION: High frequency voltage RF1 for exciting plasma is impressed on the electrode 23 of the pockels cell 18 of an electro-optical modulator 15, high frequency voltage RF2 adjusted so that the phase of the high frequency voltage RF1 is delayed by 2π(rad) or a little is impressed on the other electrode 24 by a phase adjuster. Light from a LED (light source) 13 is incident on the electro-optical modulator 15, light transmitted through the pockels cell 18 is incident on a pin photo-diode 26 through an optical fiber 25, and light intensity is detected. Hereby, because the high frequency voltage RF1 can be perfectly cancelled with the high frequency voltage RF2 regulated in the phase, up to spike pulse of GHZ order can be sharply detected, without being influenced by distortion, noise, and the like of the high frequency voltage RF1.
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