Based on the phenomena that electro-optical devices with "cat eye effect" can reflect input light beam exactly back along the direction the beam incidents, a resonator of novel configuration was formed by utilizing the "cat eye" system as an equivalent resonant mirror of laser. The equivalent reflectivity of "cat eye system" was defined to describe the ability of reflecting input light exactly backward. Laser oscillation was achieved by pumping a Nd:YAG rod located between a corner cube prism and a cat eye system. These properties make it possible to be applied in electro-optical countermeasures.