Electro-optic modulators can be used as choppers, function generators or optical power controllers. The materials dealt with are PLZT ceramics and nematic LC compared with smectic A and C LCs. PLZT is fast in the scatter mode, but its contrast is poor. The NCAP nematic LC structure has a high contrast, but is slow. Both PLZT ceramics and smectic phases can achieve microsecond switching times in the polarization mode. The achieved contrast is high with PLZT, while with LCs it depends on the switching speed. A modulator based on polarization has a complicated structure when non-polarized light is used.