SENSITIVITY IMPROVEMENT OF AN ELECTROOPTIC HIGH-IMPEDANCE PROBE

This paper describes techniques for improving sensitivity of an electr o-optic (EO) high-impedance probe, which is a powerful tool for measur ing multigigahertz signals of on-board circuits, Higher sensitivity is achieved by decreasing the half-wave voltage of the EO crystal in the probe head and by increasing the laser power. To decrease the half-wa ve voltage, we employ Bi12TiO20, a newly developed crystal with a larg er EO coefficient, and a 1.3-mu m laser diode instead of a 1.55-mu m l aser diode. To boost the laser output power, the sampling rate is incr eased by using a specially designed laser driver unit. These technique s improve the total voltage sensitivity of the probe system 3.6 times compared with our previous system. This directly leads to a more than one order reduction of signal acquisition time. Moreover, these techni ques make the probe system cost effective because they eliminate the n eed for expensive optical components.