Tunable axially symmetric optical device and novel applications via dye-doped liquid crystal films of axial symmetric photoalignment method

摘要

Introduction An axially symmetric liquid crystal (LC) structure can be used generally in axially symmetric optical system as spatial polarization converter and axial waveplates. Such waveplates present a valuable photonics tool for beam shaping, imaging, laser material processing, spectral filtering and for optical tweezer applications. On the other hand, axially symmetric LC structure is independent of linearly polarized light in the azimuthal angles because the LC directors are oriented symmetrically in the radial directions. Therefore, it can be used as an optical device to change the polarization of axial polarization beam. Besides, there has potential for developing the space-variant polarized light with axial symmetry devices. Several methods for tuning the polarization characteristic have been explored. Those use special LC cells with circular rubbing or subwavelength gratings to produce the radially or azimuthally polarized light. However, these approaches require a complicated fabricating procedure such as circular rubbing or micro-fabrication process. Besides, there are difficult to tunable the polarization state in those axially symmetric devices. One approach uses the axial waveplate which is fabricated by liquid crystal polymer (LCP). The major shortcoming of this method is unable to tunable the phase retardation for broad band at one cell and fabrication process is complicated to match a special wavelength.