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A plasmonic integrated circuit configuration comprising plasmonic and electronic components is presented and the feasibility for high-speed signal processing applications is discussed. In integrated circuits, plasmonic signals transmit data at high transfer rates with light velocity. Plasmonic and electronic components such as wavelength-divisionmultiplexing (WDM) networks comprising metal wires, plasmonic multiplexers/demultiplexers, and crossing metal wires are connected via plasmonic waveguides on the nanometer or micrometer scales. To merge plasmonic and electronic components, several types of plasmonic components were developed. To ensure that the plasmonic components could be easily fabricated and monolithically integrated onto a silicon substrate using silicon complementary metal-oxide-semiconductor (CMOS)-compatible processes, the components were fabricated on a Si substrate and made from silicon, silicon oxides, and metal; no other materials were used in the fabrication. The plasmonic components operated in the 1300- and 1550-nm-wavelength bands, which are typically employed in optical fiber communication systems. The plasmonic logic circuits were formed by patterning a silicon oxide film on a metal film, and the operation as a half adder was confirmed. The computed plasmonic signals can propagate through the plasmonic WDM networks and be connected to electronic integrated circuits at high data-transfer rates.

We have developed near-infrared imaging equipment that can detect small organic substances in foodstuffs with thicknesses of more than 1 mm. The equipment is composed of a high output laser diode and a CMOS camera. The irradiated light power distribution was highly uniform with a maximum optical density of 1.3 W/cm 2 . A 0.3-mm-diameter wooden stick covered with a 2-mm-thick layer of ha m can easily be distinguished in the images. The bones in fish and in chicken wing sticks could also be distinguished. The thicknesses of the fish and the chicken wing sticks were approximately 30 mm and 20 mm, respectively. We eliminated the low spatial frequency components from the images to improve the image contrast. Keywords: near-IR imaging, optical equipment, food contaminan t detection, foreign substance, spatial frequency filter 1. INTRODUCTION In our daily lives, foreign substances in foods can cause se rious problems because they can badly affect human health 1 . Various systems, including X-ray computed tomography and metal detectors, have been used to detect these contaminant substances. In mass production lines in food processing factories, X-ray computed tomography is generally used to detect foreign substances in foods, including metal articles and high-density materials such as stones. However, organic materials, such as hairs and wooden sticks, are difficult to detect when using X-ray computed tomography or metal detectors. A contaminant detection technique that uses near-i nfrared (NIR) light has been a ttracting attentio n because the technique enables transmission images to be monitored at high speed. For example, detection systems based on NIR hyperspectral imaging spectroscopy can detect impurities in cereals

A surface plasmon polariton (SPP) is composed of collective electron oscillations that confine optical energies in nanoscale beyond the diffraction limit. This advantage of SPPs has promoted the development of high-density optoelectronic integrated circuits (OEICs) using SPPs. Schottky-type plasmonic detectors have attracted particular attention, because these devices show sensitivity in the telecommunications wavelength range and can be integrated into Si-based electronic circuits with a simple fabrication process. We have developed an Au/Si Schottky-type plasmonic detector with nano slits that excites SPPs at the Au/Si interface. In this report, we demonstrate a novel nano-slit arrangement that provides a sensitivity improvement for the detector. Using the finite-difference time-domain method, we have shown that the highest electric field intensity in the SPP mode on the Au/Si interface is generated by positioning slits with twice the pitch of the SPP wavelength at the Au/Si interface. Using this slit pitch, a weaker SPP mode intensity on the air/Au interface and a stronger SPP mode intensity at the Au/Si interface have also been confirmed. Nano slits with different slit pitches were formed in the Au film of the detector, and the slit pitch dependence of the photocurrent was measured. The experimental results showed similar tendencies to the simulation results. This novel nano-slit arrangement can provide an efficient plasmonic detector for future high-speed data processing applications.

The operation of a metal-oxide-semiconductor field-effect transistor (MOSFET) by a surface plasmon (SP) signal was demonstrated. The SP detector, composed of a gold/silicon Schottky diode with a nano-slit grating, was monolithically integrated with the MOSFETs on a silicon substrate. SP generation by the nano-slit gating (slit width of 100 nm, slit pitch of 440 nm, and slit depth of 300 nm) was confirmed by analytical calculations based on the finite-difference timedomain method. The SP detector operated at a photon energy (0.80 eV) that was below the bandgap energy of silicon (1.1 eV), with responsivity of 24 nA/mW and a dark current of 1.7 nA under reverse bias of 5.0 V. The photocurrent generated by the SP detector controlled the drain current of a monolithically integrated MOSFET.

Contamination of foodstuffs with foreign substances is a serious problem because it often has negative effects on consumer health. However, detection of small organic substances in foods can be difficult because they are undetectable with traditional inspection apparatus. In this work, we developed new equipment that can detect small organic contaminant substances in food at high speed using a near-infrared (NIR) imaging technique. The absorption spectra of various foods were measured, and the spectra showed low absorbance at wavelengths from 600 nm to 1150 nm. Based on the observable wavelength range of a CMOS camera, which has a high dynamic range, superluminescent diodes (SLDs) with a wavelength of 830 nm were selected as light sources. We arranged 40 SLDs on a flat panel and placed a diffusion panel over them. As a result, uniformly distributed light with an intensity of 0.26 mW/cm 2 illuminated an area of 6.0 cm × 6.0 cm. Insects (3 mm wide) and hairs (0.1 mm in diameter) were embedded in stacked ham slices and in chocolate, with a total thickness of 5 mm in each case, and the transmission images were observed. Both insects and hairs were clearly observed as dark shadows with high contrast. We also compensated the images by using software developed in this study to eliminate low spatial frequency components in the images and improve the sharpness and contrast. As a result, the foreign substances were more clearly distinguished in the 5-mm-thick ham.

Grating inscription in azo-dye doped polymers is an interesting phenomenon because of its high diffraction performance and applicability to real-time 3D displays. Although some of these materials were investigated under no external electric field with symmetric optical alignments in preceding studies, they often showed a phase shift of periodic modulation of refractive index from the interference fringe formed by irradiation beams, resulting in asymmetric energy exchange between two coupled beams. The mechanism of the behavior has been usually attributed to the molecular motions triggered by trans-cis isomerization, but their details are still unknown. Therefore, studies on temporal evolution of the process and their translation into physical meaning are necessary. In order to investigate the evolution of grating inscription and phase shift, several methods have been developed. In this study, we analyzed the coupled wave equations proposed by Kogelnik, and derived general solution applicable to the system with both phase and amplitude gratings with arbitrary phase relationship. We showed that the analysis based on the equation can give a direct evidence of the phase shift between the phase and amplitude gratings if it exists. This method was applied to the fringe pattern inscribed in thick films of PMMA doped with an azo-carbazole dye, showing that observed signals indicated the phase deviation between two types of gratings.

Optical circuits are needed to achieve high-speed, high-capacity information processing. An optical waveguide is an essential element in optical circuits. Electrospun polymer fibers have diameters in the nanometer range and high aspect ratios, so they are prime candidates for small waveguides. In this work, we fabricate uniform electrospun polymer nanofibers and characterize their optical waveguiding properties. Poly(methyl methacrylate) (PMMA) solutions of different concentration that contain a small amount of Nile Blue A perchlorate (NBA) are electrospun. Uniform PMMA/NBA nanofibers are obtained from the 10 wt% solution. The fibers are covered with transparent cladding and their ends cut vertically. A laser beam with a wavelength of 533 nm is irradiated onto the fiber from the direction vertical to the fiber axis so that it scans along the fiber. Photoluminescence (PL) at the end face of individual fibers is then measured. The PL intensity decreases with increasing distance (d) between the end face of a fiber and irradiating point of the laser beam as ~exp(-αd) with a loss coefficient (α). Measurements of five individual fibers reveal α is in the range of 17–75 cm -1 .