In this contribution we show highly polarized photoluminescence (PL) from aligned polyethyleneoxide: polyphenylenevinylene derivative composite nanofibers. We demonstrate PL polarization ratios (parallel to perpendicular) greater than 13. This ratio is further increased (up to $\sim 25$ ) by stretching the nanofibers. Stretching also results in an increase in conjugation length, fiber density, and PL lifetime. We argue that the effect of stretching is equivalent to applying a permanent and strong pressure. Our results open up the possibility for new optoelectronic devices and fundamental science studies based on polymer nanofibers.

All-optical logic circuits using surface plasmon polaritons have a potential for high-speed information processing with high-density integration beyond the diffraction limit of propagating light. However, a number of logic gates that can be cascaded is limited by complicated signal phase adjustment. In this study, we demonstrate a half-adder operation with simple phase adjustment using plasmonic multimode interference (MMI) devices, composed of dielectric stripes on a metal film, which can be fabricated by a complementary metal-oxide semiconductor (MOS)-compatible process. Also, simultaneous operations of XOR and AND gates are substantiated experimentally by combining 1 × 1 MMI based phase adjusters and 2 × 2 MMI based intensity modulators. An experimental on-off ratio of at least 4.3 dB is confirmed using scanning near-field optical microscopy. The proposed structure will contribute to high-density plasmonic circuits, fabricated by complementary MOS-compatible process or printing techniques.

Two passive plasmonic demultiplexers with multimode interferometer (MMI)-based rectangular and bow-tie designs are demonstrated for 1.31- and 1.55-μm-band wavelength division multiplexing system operation in plasmonic circuits. These demultiplexers are designed using the finite-difference time-domain (FDTD) method and fabricated using complementary metal-oxide-semiconductor-compatible processes. SiO2 films deposited on metal films are etched to form mesa structures by focused ion beam milling, and single-mode waveguides, MMIs, and bow-tie structures are then formed on the metal films. In the plasmonic circuits, 1.31- or 1.55-μm-wavelength surface plasmon polariton (SPP) signals can be distributed to each of the different demultiplexer outputs without any change in signal propagation speed. The SPP intensity distributions that are measured using a scanning near-field optical microscope agree well with the distributions that were calculated using the FDTD method. The insertion loss and crosstalk are then calculated for each demultiplexer. In the rectangular-type demultiplexer, the calculated values were less than 9.5 dB and -2.4 dB, and in the bow-tie-type demultiplexer, the corresponding values were 8.9 dB and less than -2.3 dB, respectively. These results demonstrate the applicability of the developed plasmonic demultiplexers to plasmonic circuits when monolithically integrated on a silicon substrate.

A poly-DL-lactide (PLA) fiber film was prepared using the electrospinning method. This film consisted of randomly oriented PLA nanofibers. Consequently, it had sponge-like structure and was quite soft compared to PLA films prepared by spin coating. The average diameter of the fibers and the density of the film were 730 nm and 20%, respectively. By applying a voltage, the PLA film was subjected to electric-field-induced strain: expansion and compression in the thickness direction. When a voltage of −200 V was applied to the film, its thickness shrank from 13.5 μm to 10.0 μm (a 26% reduction). Electric-field-induced strain can occur via two different mechanisms: The first is electrostrictive behavior. That is, in a highly electric field region, a change of film thickness occurs (compression only) from the electrostatic force between electrodes. The second mechanism is piezoelectric-like behavior that occurs in racemic PLA, wherein a PLA nanofiber is expanded and compressed by applying positive and negative voltage. Such piezoelectric-like behavior was not observed in spin-coated PLA films.

We demonstrate a simple and versatile method for the fabrication of a submicron channel for an organic field-effect transistor (OFET) using a single electrospun fibre as a shadow mask. A single electrospun fibre is produced by an alternative switching electrospinning method and is stretched 2.5-fold. The average diameter of the stretched fibres is 302 nm. The stretched fibre is placed on ultrathin dielectric layers of aluminium oxide and a self-assembled monolayer (SAM). During electrode deposition the fibre acts as a very small shadow mask. After removing the fibre, electrodes with very narrow gaps of around 350 nm and with high uniformity are easily obtained. We fabricate an OFET by depositing pentacene as an active layer onto the electrodes. The OFET is operable at low voltages, with a threshold voltage of - 1.1 V and a subthreshold swing of 0.27 V decade(-1), values which are one order of magnitude lower than those obtained with a channel length of 75 µm.