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/cm2. A 0.3-mmdiameter wooden stick covered with a 2-mm-thick layer of ham 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.
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/cm2 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.