Design of an Electro-Optic Polarization Switch for a High-Capacity High-Speed Digital Light Deflection System

Abstract

Modulator requirements for an active electro-optic polarization switch to operate in a digital light deflector (DLD) are derived. It is shown that a simple capacity speed product of the form (capacity) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> × (address rate) ≦ (constant) × (driver power) can be derived for both linear and biased quadratic electro-optic modulator materials. The usefulness of this relation is demonstrated by applying it to a biased quadratic electro-optic material (KTN) and two linear electro-optic materials (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> and ZnTe). The results indicate that KTN will operate a DLD at a rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> random addresses/sec and a capacity of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> addresses with a reactive power of 2.6 watts, a bias voltage of 1200 volts, and a driver voltage of 42 volts, provided, (i) fluctuations in the Curie temperature and ambient operating temperature are held to less than 0.01°C, (ii) some form of ac bias is used to circumvent space charge effects, and (iii) strain and defect-free material meeting these requirements can be grown to a size of at least 1 × 1 × 2 cm. A linear electro-optic material such as ZnTe with a reduced half-wave voltage (unity aspect ratio) in the 2 to 3-kV range (2.5 kV at 6000 Å) will provide 3.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> addresses at a rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> addresses/sec with a reactive driver power of 10 watts, delivered at a drive voltage of 1250 volts. Experimental results obtained using KTN as a high-speed pulsed light modulator are also presented.