Design of an Electro-Optic Polarization Switch for a High-Capacity High-Speed Digital Light Deflecting System
01 October 1966
In this paper we examine the design of a high-speed optical polarization switch utilizing the electro-optic properties of certain crystalline solids. Primary emphasis has been placed on potassium tantalate-niobate, but linear electro-optic materials are also considered. The design 1209 1210 T H E BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 196f> equations are applied to a switch for a 106 addresses/sec digital light deflector (DLD) described by Nelson1 and Tabor.2 In Section II a derivation of the capacity-speed equation is given. Sections III and IV discuss the reactive power limitations due to heating of a KTN modulator, and typical operating characteristics for a highspeed modulator are tabulated. Section V discusses additional limitations on the capacity-speed product of KTN due to composition inhomogeneities and ambient temperature fluctuations. Space charge effects and ac biasing are treated in Section VI. In Section VII the advantages of a rectangular aperture are considered and a comparison is made of the capacity speed product of KTN with those of the linear electro-optic materials ZnTe and LiNbOs. Finally, in Section VIII some experimental results are presented for pulse modulation of light using KTN. I I . DERIVATION OF T H E CAPACITY-SPEED RELATION