Liquid Crystal Digital Beam Steering Device Based on Decoupled Birefringent Deflector and Polarization Rotator

ABSTRACT

We describe digital beam deflectors (DBDs) based on liquid crystals. Each stage of the device comprises polarization rotator and birefringent prism deflector. We used prisms made of the uniaxial smectic A (SmA) liquid crystal and a solid yttrium orthovanadate crystal. SmA prisms have high birefringence and can be constructed in a variety of shapes. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Rotation of linear polarization is achieved by electrically switched twisted nematic or electrically controlled birefringent cell. We describe a four-stage DBD steering a normally incident laser beam within ±56 mrad range with 8 mrad steps.

Keywords:

• beam deflector
• birefringent prism
• polarization rotator
• smectic A

Acknowledgments

We thank Phil Bos for numerous useful discussions. The work was supported by NASA grant NAG3-2539 and by Rockwell Scientific Co.