Variable phase retarder made of a dielectric elastomer actuator

We present a polymeric optical phase retarder that is electrically tunable by a dielectric elastomer actuator. The soft material device affords a large tuning range (14pi at lambda=488 nm) combined with high accuracy in optical path length and low drift rate (8.3 nm/min). Furthermore, the phase retarder is not sensitive to polarization, introduces a wavefront distortion<lambda/30, and tolerates high power densities (>141 kW/cm2). We show the dynamics for periodic phase modulation and demonstrate a simple drive technique for fast phase stepping. The polymer-based device is inexpensive, easy to fabricate, and its design can be adapted to specific applications.