Blue-phase liquid crystal (BPLC) is introduced into the pores of capillary arrays to fabricate fiber arrays. Owing to the photonic-crystals like properties of BPLC, these fiber arrays exhibit temperature dependent photonic bandgaps in the visible spectrum. With the cores maintained in isotropic as well as the Blue phases, the fiber arrays allow high quality image transmission when inserted in the focal plane of a 1x telescope. Nonlinear transmission and optical limiting action on a cw white-light continuum laser is also observed and is attributed to laser induced self-defocusing and propagation modes changing effects caused by some finite absorption of the broadband laser at the short wavelength regime. These nonlinear and other known electro-optical properties of BPLC, in conjunction with their fabrication ease make these fiber arrays highly promising for imaging, electro-optical or all-optical modulation, switching and passive optical limiting applications.

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We present the results and critical analyses of recent studies of ultrafast optical nonlinearities of liquid crystals in the isotropic and ordered phases for time scales spanning femtosecondsmicroseconds. Pure undoped liquid crystals as well as liquid crystals containing plasmonic nanoparticles have been investigated. Individual molecular electronic optical nonlinearities are found to be useful for femtoseconds -nanoseconds nonlinear transmission clamping applications. On the other hand, laser induced order parameter and birefringence modification in aligned nematic cells allow very rapid transmission switching of visible as well as near infrared lasers with response times in the sub-microseconds -few nanoseconds regime. INTRODUCTIONIn the current quest for high performance material and optical devices, liquid crystals occupy an ever widening niche as a result of their unique physical and optical properties [1, 2], and compatibility with almost all other technologically important optoelectronic materials. Their dual fluid-crystalline properties enable assembly or integration into a variety of forms, shapes and geometry such as photonic crystals [3,4], fiber or channel waveguides [5,6], periodic or aperiodic nanostructures [7-9] and other flexible specialized forms and shapes.The science and technology of electro-optical effects in liquid crystalline materials have been very well developed by now, and fuel the world-wide display industry. This paper is focused on the all-optical version, in which the optical processes are triggered by the action of the impinging optical fields on the material, causing index and birefringence changes which in turn causes amplitude and phase modulation on the optical fields [2]. We will discuss the results from recent studies of ultrafast individual molecular electronic optical nonlinearities of isotropic phase LC as well as laser induced order parameter and birefringence modification in the ordered nematic phase, and some novel all-optical switching processes enabled by these optical nonlinearities with response times several orders of magnitude faster than their electro-optics counterparts.

A critical analysis of various nonlinear mechanisms such as laser induced thermal/order parameter changes and flow orientation effects in nematic liquid crystal is presented, along with feasibility demonstrations of all-optical switching and optical image processing and tunable photonics using these mechanisms. The merits and limitation of nematics are discussed together with some preliminary results with Blue Phase liquid crystals that could circumvent some of the limitations.