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A novel surface plasmon multiplexers having low return loss are demonstrated in 1.31-μm- and 1.55-μm-wavelength bands. The size of the multiplexer comprising SiO 2 stripes on a gold film was 2.5 μm × 6.0 μm and its performance were experimentally confirmed. To reduce further the size of multiplexer, a multiplexer comprising a gold/TiO 2 /gold layered structure was designed and its operation was analyzed via numerical simulations. Introducing the layered structure reduced the size of multiplexer to 0.6 μm × 0.8 μm.

We analyzed the guiding properties of 1.31 and 1.55 μm wavelength surface plasmon polaritons (SPPs) on a Au stripe waveguide on Si, noting the propagation length with different waveguide widths and Au thicknesses. Further, we designed a wavelength-selective structure for 1.31 and 1.55 μm wavelength SPPs, and the operation was experimentally confirmed.

We introduce a novel multimode-interference-based plasmonic phase adjuster, which simplifies cascaded photonic-integrated-circuit (PIC) patterns. A cascaded plasmonic half-adder circuit that includes the proposed phase adjuster is demonstrated using scanning near-field optical microscopy. The proposed phase adjuster will be indispensable for future PIC technologies.

We demonstrate a plasmonic intensity modulator using plasmonic superfocusing. The device comprises a metallic taper and a nanoscale waveguide. Its 10.8 dB extinction ratio is confirmed by controlling the phase difference between two input plasmons.

We investigate the detection efficiency of a metallic-grating-based plasmonic detector composed of a Schottky diode and multiple plasmonic waveguides. We then demonstrate a metal-oxide-semiconductor field-effect transistor that includes the plasmonic detector and two plasmonic waveguides.

This paper presents a type of plasmonic circuit that is monolithically integrated with electronic devices on a silicon substrate and discusses the concept behind this circuit. Surface plasmon waveguides and detectors are integrated with metal-oxide-semiconductor field-effect transistors (MOSFETs) on the substrate. In the circuits, surface plasmon signals are generated by light at a wavelength at which silicon is transparent, and propagate along the waveguide before being converted into electrical signals by the detector. These electrical signals drive the MOSFETs during both dc and ac operation. The measured performances of these devices indicate that the surface plasmons propagate on the metal surface at the speed of light and drive the electronic devices without any absorption in silicon.

We present a promising design for low-loss asymmetric plasmonic crystal waveguides. The plasmonic crystal consists of Au cylinders, and the waveguide is introduced by eliminating a single line of cylinders on Au metal.

We demonstrate the dynamic operation of monolithically integrated plasmonic detector and MOSFETs on silicon. The integrated device operates at the beat signal of surface plasmons converted from two light beams in 1.31μm-wavelength band.

We fabricate single electrospun polymer nanofibers consisting of poly(vinylcarbazole) (PVCz) doped with 4,4'-bis [(N-carbazole)styryl]biphenyl (BSB-Cz). The diameter of the fibers measured by scanning electron microscopy is approximately 300 nm. Waveguiding in a fiber is confirmed by comparing the photoluminescence intensities of the middle and end of a fiber. We confirm that the guided light is mainly emitted from BSB-Cz.

Electrospun nanofibers are fabricated from poly(DL-lactic acid) (PLA), and the piezoelectric-like response and waveguiding properties of these nanofibers are demonstrated. A sheet composed of randomly orientated PLA fibers sandwiched between electrodes exhibits a linear increase in thickness with increasing applied voltage. This indicates that the fibers act like a piezoelectric material. The waveguiding properties of the fibers when doped with an organic dye are investigated by aligning the fibers unilaterally. Photoluminescence from the dye propagates within the fibers, with an attenuation of

This paper demonstrates the monolithic integration of a plasmonic device with metal-oxide-semiconductor field-effect transistors (MOSFETs) on a Si substrate. The plasmonic device consists of a waveguide and a detector, and is fabricated by a simple process. We confirmed that surface plasmon polaritons (SPPs) propagate for a distance of 100 μm on the Au surface, and are detected as a photocurrent. In addition, an integrated circuit containing the plasmonic device and the MOSFETs was operated by the photocurrent converted from the SPPs.

The feasibility of optical signal transmission and electrical bias separation was demonstrated by forming a 3-μm-wide separation gap between a plasmonic waveguide and a Au/Si Schottky diode. To transmit optical signals, a surface plasmon polariton was excited at the air/Au interface of the Au film deposited on the SiO 2 layer. The transmitted optical signal was detected as a photocurrent using the Au/Si Schottky diode. The electrical separation was confirmed by applying a bias voltage between the plasmonic waveguide and the Si substrate. From the transmitted power, optical signal transmission only across the electrical separation gap was confirmed.

The synthesis of single-crystal silicon (Si) nanowires by a metal-catalyst-free vapor-liquid-solid (VLS) process has been studied. Si nanowires have been successfully synthesized by a simple thermal treatment without using a metal catalyst, while well-aligned nanowires have been grown by the conventional Au-catalytic VLS process. It is thought that sulfur, rather than metals, plays an important role in this synthesis technique, which is distinct from the conventional metal-catalytic VLS process. For the case without metal catalysts, single-crystal Si nanowires are grown by a VLS process in which the silicon sulfides produced by a reaction between Si and sulfur act as both molten eutectic alloy droplets and the source gases for nanowire growth. Structural characterizations of the nanowires were performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The XRD measurements showed that the single crystal nanowires on a (111)-oriented Si substrate were preferentially oriented in a growth direction.

A gold/silicon Schottky-type plasmonic detector was monolithically integrated with two metal-oxide-semiconductor field-effect transistors (MOSFETs) on a silicon substrate. The output current from the detector was amplified 14000 times by using the MOSFETs.

Arrays of single-crystal zinc oxide (ZnO) nanowires have been synthesized on silicon substrates by vapor-liquid-solid growth techniques. The effect of growth conditions including substrate temperature and Ar gas flow rate on growth properties of ZnO nanowire arrays were studied. Structural and optical characterization was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The XRD measurements showed that the single crystal nanowires exhibited growth in the (002) direction. SEM images of the ZnO nanowire arrays grown at various Ar gas flow rates indicated that the alignment and structural features of ZnO nanowires were affected by the gas flow rate. The PL of the ZnO nanowire arrays exhibited strong ultraviolet (UV) emission at 380□nm and weak green emission around 510□nm. A blue shift and broadening of the UV emission was observed with an increment of Ar gas flow rate.

We propose a polarization-independent Au/Si Schottky-type photodetector with a ring-type grating that excites surface plasmon polaritons. The electromagnetic fields in ring-type and rectangular-type grating structures are calculated using the finite-difference time-domain method. For samples with the two geometries (slit width of 100 nm, slit pitch of 440 nm, and Au film thickness of 300 nm), the polarization dependence of the photocurrent is measured and compared. We confirm that the ring-type grating photodetector has a polarization-independent photocurrent, whereas the rectangular-type grating photodetector has only higher sensitivity at specific polarization angles.

We propose an optimal structure for an Au/Si Schottky-type photodetector with a multi-slit grating that excites surface plasmon polaritons (SPPs). The intensity of the SPPs excited by the grating is simulated using the finite-difference time-domain method. The calculation results show that the optimum Au film thickness and slit pitch were determined by the resonance effects of SPPs inside the slit and the in-phase interference of the SPPs generated by each slit, respectively. Using these results, we fabricate and evaluate an optimal photodetector with the grating. We also confirm the operation of metal-oxide-semiconductor field-effect transistors by the SPP-enhanced photocurrent.

We have experimentally and theoretically demonstrated a suitable design for optical antennas with nanorods on a Si substrate to realize plasmonic integrated circuits (PICs). We show that the reflectance measurement results for gold nanorods arranged on the Si substrate correspond to the results calculated by the finite-difference time-domain (FDTD) method. Based on these studies, we designed a structure for the arrangement of aluminum nanorods for Si-PICs for a wavelength range of 800–2000 nm, to match the wavelengths of 1300 nm and 1550 nm that are commonly used in optical communication systems.

We discuss an analytic expression for the spectral shape of propagating surface plasmon polaritons (SPPs). Based on Drude's model, the SPP spectral deformation, determined by differences in the intensity decay length, has been confirmed.

We report results from a numerical study of optical-frequency signal transmission via localized surface plasmons (LSPs). LSPs excited within a Au disk on a Si substrate propagate over a chain of disks providing the signal.