Electro-optic sampling probe and a method for adjusting the same

A method for adjusting an optical axis of an electro-optic sampling probe having an electro-optic element which is to be positioned to contact with wiring on an IC wafer surface as a measurement target and whose optical characteristics are changed depending on an electric field applied via said wiring, and an electro-optic sampling optical system module having a polarized beam splitter, a wave plate, and a photo diode having a light receiving surface, said module for separating light which is transmitted through said electro-optic element and is reflected by a surface of said electro-optic element from laser light emitted from the outside and for converting the separated light into an electric signal, said method comprising the steps of:

• adjusting the emission point of said laser light within a plane by moving an optical fiber for emitting said laser light in the directions of two axes which are perpendicular to each other;
• adjusting the state of the collimated light from said electro-optic sampling optical system module by moving said optical fiber in the direction of the optical axis of said optical fiber;
• adjusting the inclination of said plane by rotating said two axes, which are perpendicular to each other, around their axes, respectively;
• and
• adjusting said light receiving surface of said photo diode by moving said photo diode in the directions of two axes which are perpendicular to each other and any one of which is along a direction parallel to the axis of the laser light in order to enter the light reflected by said electro-optic element to the receiving surface of said photo diode.