Thermally tunable microlenses using smetic liquid crystal defects

Abstract

We demonstrate a new type of a thermally tunable microlens which is entirely based on self-assembly of liquid crystal defects. Unlike previous researches for fabricating tunable microlens using liquid crystal, this method is used solely liquid crystalline materials without mixing other materials or applying external field. Due to antagonistic anchoring conditions of liquid crystals at the smectic A and air interface in microchannels coated planar anchoring materials, smectic liquid crystals form typical defect textures called toric focal conic domains (TFCDs). TFCD-based MLAs have several advantages over other MLAs. This system focuses light using the intrinsic molecular orientations of TFCDs rather than geometrical shape, leading to high quality lens properties. Furthermore, the lens itself has tunable light transportation and all the changes could be reversibly controlled by temperature. In addition, the focal length and array number of microlens can be easily controlled by varying the feature dimension of the confined channel. Thus, this method is very easy to fabricate thermal responsive MLAs with a variety of focal length and number of array using defect structure of smectic liquid crystal.