A single crystal multiple-wavelength electro-optic modulator

A new multi-wavelength low voltage electro-optic modulator has been constructed using the r41coefficient in a single crystal of ADP. It is intended for use in multi-color laser display and recording systems employing a single source such as a krypton-ion laser. The modulator accepts a coaxial mixed wavelength beam and separates the colors using a set of direct view spectroscopic prisms. Each color passes under separate sets of electrodes on the crystal, is individually modulated, and is recombined on axis with a second set of prisms. The design of the modulation section is based on a parallel arm interferometer arrangement with both arms passing under adjacent electrodes on the electro-optic crystal. This single crystal configuration makes the crystal simple to fabricate and adjust and results in stable operation with high optical powers and changes in ambient temperature. Typical characteristics, exemplified by the red channel, showed a 100% modulation voltage of 64 Vp-pacross 104 pF input capacitance with an extinction ratio of 50:1.