Tunable binary retarder using self-aligned liquid crystal on anisotropic polymer film by photo-assisted imprinting Jiyoon Kim, 1 Yong-Woon Lim, 2 Jun-Hee Na, 1 and Sin-Doo Lee 1, * 1 School of Electrical Engineering, Seoul National University, Kwanak, P.O. Box 34, Seoul 151-600, South Korea 2 Samsung Displays Co. Ltd., Giheung-gu, Yongin-si, Gyoenggi-do 446-711, South Korea *Corresponding author: sidlee@plaza.snu.ac.kr Received 16 January 2013; revised 18 February 2013; accepted 18 February 2013; posted 20 February 2013 (Doc. ID 183613); published 8 March 2013 We demonstrate an electrically tunable binary retarder (ETBR) with a self-aligned liquid crystal (LC) on an anisotropic polymer film produced by photo-assisted imprinting. The ETBR has two parts: a tunable optical layer of an LC and a static optical layer of an imprinted anisotropic polymer film possessing two different in-plane optic axes. The anisotropic polymer film was produced using reactive mesogens spon- taneously aligned along the topographic microgrooves by imprinting under the exposure of ultraviolet light. An electrically tunable hybrid wave plate, whose phase retardation varies from a quarter to a half- wave, is constructed using the self-aligned LC layer on the imprinted polymer film that behaves as a quarter wave plate with two alternating optic axes. This approach can be used to design a new class of tunable optical devices with multiple in-plane optic axes. © 2013 Optical Society of America OCIS codes: 160.3710, 230.3720, 230.2090, 230.0230. 1. Introduction Many types of electro-optical (EO) components capable of modulating the optical phase retardation or manipulating the polarization state of light recently have been demonstrated for use in diverse optical systems, such as three-dimensional (3D) dis- plays [ 1– 5], optical data storage [ 6– 9], and optical communications [ 10– 13]. Among them, liquid crystal (LC)-based devices have been most extensively stud- ied due to the large optical anisotropy, low-voltage operation, and well-established fabrication technol- ogy [ 14– 16]. Moreover, to enhance the electro-optic effect of the LC, device configurations can be easily tailored by means of the electrode structure and the LC alignment geometry. For example, an electri- cally tunable lens made of an LC on a structured liquid crystalline polymer (LCP) surface [ 15, 17, 18] showed a relatively wide tuning range of the focal length. In this case, the polymer layer yields a fixed focal length while the LC layer produces a tunable lens [ 18] or a light modulator [ 17]. Another case is a patterned retardation film that serves as one of the key elements needed for 3D displays [ 4, 5]. More recently there have been reports of a patterned retarder in a reflective 3D LC display produced by selective ultraviolet (UV) exposure [ 19] and a polym- erized micropatterned optical birefringence film fabricated using beam mixing [ 20]. However, for more sophisticated applications, the multifunctional- ity associated with the EO effects inherent to differ- ent geometrical constraints [ 16, 21] and/or different functional layers remains to be explored. In this work, we demonstrate an electrically tuna- ble binary retarder (ETBR) with a self-aligned LC on an anisotropic polymer film produced by photo- assisted imprinting. The polymer film was produced using reactive mesogens (RMs) under the exposure of UV light. Figure 1 shows the ETBR, which consists of 1559-128X/13/081752-06$15.00/0 © 2013 Optical Society of America 1752 APPLIED OPTICS / Vol. 52, No. 8 / 10 March 2013