Abstract: A mechanical probe for optical measurement of electrical potentials. The probe of the present invention is composed of a cubic, electro-optical crystal fashioned in the form of a tip and of a metallization which is at ground potential and which covers the crystal with the exception of those surface regions located immediately opposite a measuring location, for example an interconnect of an integrated circuit. Since the metallization acting as a cooperating electrode significantly facilitates the penetration of the electrical stray field into the crystal tip, geometry-dependent effects and influences of electrical microfields are nearly completely supressed. The probe therefore makes it possible to utilize the voltage difference instead of the topography-dependent field difference for optical measurement of electrical signals with high chronological resolution.