Photo-and Electro-Switchable 1/2D Diffractive Structures Exploiting Soft-Matter.

摘要

Photosensitive Liquid Crystals (PLC's) are promising materials in the photonics field as they combine the photosensitivity of photochromic molecules such as azobenzene-based materials with the high birefringence that is typical of liquid crystals. By exposing azobenzene molecules to suitable wavelength radiation, they undergo a conformational change (trans-cis isomerization) which can occur in nanoseconds and which can drive the liquid crystal through an isothermal nematic-isotropic phase transition. This photo- induced isotropic state possesses a much different refractive index and the ability to switch between these two states enables ultra-fast photonic devices of tremendous scientific and technological interest. In addition, the possibility to confine and stabilize PLC's has been very recently examined by our group. Confinement in an anisotropic structure with periodicity on the order of the radiation wavelength leads to the creation of novel diffractive structures (termed H-PDLCs) whose optical properties can be switched using an electric field. The possibility to realize an optically controllable photonic device by combining the photosensitivity of azobenzene materials and the optical properties of H-PDLCs is of tremendous interest to Air Force applications. This was accomplished during this grant, and multiple characteristics and properties of H-PDLCs measured and confirmed.