Search

Focused ion beam (FIB) fabrication of fiber optic sensors, mainly chemical sensors, which are based on plasmonics-active nanostructures formed on the cleaved tips of optical fibers, is reported. The nanostructures fabricated included nanoholes in optically thick metallic films as well as metallic nanopillars and nanorods. The sensing mechanism is based on detecting shifts in surface plasmon resonances (SPRs) associated with nanoholes in metallic films and localized SPRs of metallic nanopillars and nanorods, when the refractive index of the medium surrounding the nanostructures is changed. These sensors can be employed for the detection of chemical agents in air as well as liquid media surrounding the sensors. FIB milling was employed to fabricate ordered arrays of nanoholes in optically thick (100–240 nm) metallic films deposited on cleaved end faces of multimode, four-mode, and single-mode optical fibers. Separately, metallic nanorods and nanopillars were formed by first depositing a metallic (gold or silver) film on tips of optical fibers, which was followed by FIB milling large area patterns to form freestanding nanorods and nanopillars. Utilizing FIB allows engineering nanostructure geometries, i.e., nanostructure shapes and sizes that are chosen based on the plasmon resonances associated with them. Formation of periodic arrays of nanoholes provides a means of tuning plasmon resonance peaks, associated with extraordinary transmission of light through the array of nanoholes in the metallic films, based on periodicity and shape of the nanoholes as well as on refractive index changes to form sensitive chemical sensors. [ABSTRACT FROM AUTHOR]

Recently ferroelectric ceramic and bent-core nematic liquid crystals have demonstrated flexoelectricity (coupling between curvature strains to electric polarization) up to 104 times larger than the previous standards. This may allow for usable electromechanical devices. However, ceramics are too rigid to withstand large bending and bent-core nematic fluids must be physically supported—their technological applicability is still limited. In this paper, we show that novel side-chain bent-core nematic elastomers not only produce giant flexoelectricity but are also robust and flexible enough for microscale parasitic power generation. [ABSTRACT FROM AUTHOR]

We report an approach for generating truly random digital numbers. This approach is based on probing the chaotic and unpredictable fluctuations that take place in a nematic liquid crystal when it is undergoing turbulent, electrically induced, convective flow. This technique generates a stream of numbers that passes standard benchmark tests for randomness. A device utilizing this technique is not only inexpensive to construct, but also tamper proof. We discuss various strategies for improving the operating characteristics, primarily the bit generation rate, of a device constructed on this principle. [ABSTRACT FROM AUTHOR]