Efficient liquid crystal wavefront modulator

Liquid crystal waveplates are known as efficient phase or wavefront modulators for applications requiring the active control of laser beams such as beam steering, focusing or diffraction. In developing such devices researchers have used so far two types of electrode structures: (i) the discrete structure where the liquid crystal is modulated by means of a large number of independent narrow stripe-shaped low-resistive electrodes, and (ii) the continuous structure where broad electrodes with areas of different resistivities modulate the liquid crystal via a linear or nonlinear voltage gradient generated in the electrode plane. The former approach has the advantage of high transmission efficiency and unproblematic fabrication of the electrodes. The huge number of electrodes requires however a high expenditure in fabricating the complex LC driver. The latter approach keeps down the complexity of the LC driver, however, a high optical throughput has not yet been reported. In this paper, we present an electrode design that aims at combining the advantages found in both approaches. The usefulness of the novel electrode design was verified for the first time in an experiment demonstrating the nearly diffraction limited performance of an adaptive LC microlens array.