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Keizo Kato
2017 Volume E100.C Issue 2 Pages
112-113
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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Toshifumi KOBORI, Norihiko KAMATA, Takeshi FUKUDA
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
114-117
Published: February 01, 2017
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An optical intensity distribution under light irradiation in the organic photovoltaic cell affects the absorbance of the active layer, which determines the photovoltaic performance. In this research, we evaluated the optimum thickness of the organic active layer with poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] and [6,6]-phenyl C71-butyric acid methyl ester. The spectral response of external quantum efficiency was good agreement with the simulated optical intensity distribution within a device stack as a function of the position and the wavelength. As a result, the highest photoconversion efficiency of 10.1% was achieved for the inverted device structure.
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Kazuhiko SEGI, Shigeki NAKA, Hiroyuki OKADA
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
118-121
Published: February 01, 2017
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Organic optical materials are possible to sense light because of its high photosensitivity and large absorption only 100 nm thick films. These characteristics can be applied to an optoelectronic device, such as an organic photodiode. In our previous report, we studied blue and green organic photodiode respectively. In this report, we investigated a tandem photodiode which was vertically stacked blue and green OPDs inserting intermediate semitransparent electrode. Individual photoresponse was confirmed in each blue/green unit.
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Cuong Manh TRAN, Tatsuya MURAKAMI, Heisuke SAKAI, Hideyuki MURATA
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
122-125
Published: February 01, 2017
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We demonstrate the effect of vacuum pressure on the mobility (µ) and the threshold voltage (Vth) of organic field effect transistor (OFETs) using copper as source-drain electrodes. OFETs with copper electrodes deposited at high background pressure are better in electric characteristics compared with traditional devices fabricated under low pressure using gold electrodes.
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Heisuke SAKAI, Yushi TSUJI, Hideyuki MURATA
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
126-129
Published: February 01, 2017
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We integrate a pressure sensing capacitor and a low operation voltage OFET to develop a pressure sensor. The OFET was used as a readout device and an external pressure was loaded on the sensing capacitor. The OFET operates at less than 5 V and the change in the drain current in response to the pressure load (100 kPa) is two orders of magnitude.
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Ryo YAMAMICHI, Takaaki MANAKA, Dai TAGUCHI, Mitsumasa IWAMOTO
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
130-132
Published: February 01, 2017
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Carrier transport characteristics of TIPS-pentacene single crystalline film were controlled by changing the deposition condition of the blade-coating method. Anisotropic carrier transport in the single crystalline grain was visualized by means of the time-resolved microscopic optical second harmonic generation (TRM-SHG) measurement. Slow deposition yields the film with high mobility and large transport anisotropy. For molecular crystals, intermolecular interaction can be modified easily by changing the process condition.
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Toshiki YAMADA, Yoshihiro HARUYAMA, Katsuyuki KASAI, Takahiro KAJI, Yu ...
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
133-136
Published: February 01, 2017
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We prepared a bR thin film by the wire-bar coating technique, and investigated the transient photo-current characteristics of the bR photocell. The transient photo-current signal of bR photocells prepared by the wire-bar coating technique and the dip coating technique was compared. An almost identical transient photo-current signal intensity was obtained both for the wire-bar coating technique and dip coating technique, while the thickness of bR thin film prepared by the wire-bar coating technique is slightly thinner than that prepared by the dip-coating technique. Transparent conductive oxide dependence of the transient photo-current signal is almost the same dependence for the bR photocells with a bR thin film prepared by both techniques. Application of the wire-bar coating technique is significant from the viewpoints of the bR's sample consumption as well as simplicity of sample preparation.
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Kazuki HOSOYA, Ryo WAKAYAMA, Kei OYA, Satoru IWAMORI
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
137-140
Published: February 01, 2017
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Active oxygen species (AOS), e.g., excited singlet oxygen atom [O(1D)], excited singlet oxygen molecules (1O2), ground-state oxygen atom [O(3P)] and hydroxyl radical (OH), generated under two wavelengths (185 and 254 nm) of ultraviolet (UV) light were exposed to polyethylene (PE), polypropylene (PP) and polystyrene (PS) sheets. We investigated effects of the AOS exposure on the surface modification of these polymer sheets. Nonwoven sheet was used for the surface modification to eliminate an effect of the UV light irradiation. Although hydrophobicity of the PE and PP surfaces was maintained, the PS was changed into the hydrophilic surface.
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Keisuke TOMIDA, Hiroshi FUJITA, Satoshi USUI, Kuniaki TANAKA, Hiroaki ...
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
141-144
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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Thin films of vinyl derivatives of naphthalene diimide were prepared by electron-assisted vapor deposition. Monomer materials of N, N'-bis(allyl)-naphthalene diimide (Allyl-NDI) and N,N'-bis(p-vinyl-benzyl)-naphthalene diimide (Sty-NDI) were newly synthesized for this purpose. Uniform films were obtained by vapor-depositing these materials, whereas spin-coating yielded nonuniform films. IR analysis suggested that Sty-NDI can be polymerized upon vapor deposition. An insoluble film of Sty-NDI was obtained by the electron-assisted vapor deposition. On the other hand, Allyl-NDI had lower reactivity for polymerization. It was concluded that Sty-NDI is a promising material for preparing thin films of vinyl polymer having naphthalene diimide units.
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Hiroyuki MOCHIZUKI
Article type: BRIEF PAPER
2017 Volume E100.C Issue 2 Pages
145-148
Published: February 01, 2017
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Characteristics of the bis-styrylbenzene derivatives with trifluoromethyl or methyl moieties were evaluated in each as-vapor-deposited film, thermally-treated film, and the crystal from the solution. Thermal treatment dramatically changed morphologies and photo-physical properties of the vapor-deposited film.
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Special Section on Fabrication Technologies Supporting the Photonic/Nanostructure Devices
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Susumu Noda
2017 Volume E100.C Issue 2 Pages
149
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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Ryuichiro KAMIMURA, Kanji FURUTA
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
150-155
Published: February 01, 2017
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Dry etching is one of the elemental technologies for the fabrication of optical devices. In order to obtain the desired shape using the dry etching process, it is necessary to understand the reactivity of the materials being used to plasma. In particular, III-V compound semiconductors have a multi-layered structure comprising a plurality of elements and thus it is important to first have a full understanding of the basic trends of plasma dry etching, the plasma type and the characteristics of etching plasma sources. In this paper, III-V compound semiconductor etching for use in light sources such as LDs and LEDs, will be described. Glass, LN and LT used in the formation of waveguides and MLA will be introduced as well. And finally, the future prospects of dry etching will be described briefly.
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Eiji HIGURASHI, Ken OKUMURA, Yutaka KUNIMUNE, Tadatomo SUGA, Kei HAGIW ...
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
156-160
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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Wafers with smooth Au thin films (rms surface roughness: < 0.5nm, thickness: < 50nm) were successfully bonded in ambient air at room temperature after an Ar radio frequency plasma activation process. The room temperature bonded glass wafers without any heat treatment showed a sufficiently high die-shear strength of 47-70MPa. Transmission electron microscopy observations showed that direct bonding on the atomic scale was achieved. This surface-activated bonding method is expected to be a useful technique for future heterogeneous photonic integration.
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Jitsuo OHTA, Jeong Woo SHON, Kohei UENO, Atsushi KOBAYASHI, Hiroshi FU ...
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
161-165
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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Crystalline GaN films can be grown even on amorphous substrates with the use of graphene buffer layers by pulsed sputtering deposition (PSD). The graphene buffer layers allowed us to grow highly c-axis-oriented GaN films at low substrate temperatures. Full-color GaN-based LEDs can be fabricated on the GaN/graphene structures and they are operated successfully. This indicates that the present technique is promising for future large-area light-emitting displays on amorphous substrates.
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Tatsuro ENDO, Hiroshi KAJITA
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
166-170
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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For the future medical diagnostics, high-sensitive, rapid, and cost effective biosensors to detect the biomarkers have been desired. In this study, the polymer-based two-dimensional photonic crystal (2D-PC) was fabricated using nanoimprint lithography (NIL) for biosensing application. In addition, for biosensing application, label-free detection of fibrinogen which is a biomarker to diagnose the chronic obstructive pulmonary disease (COPD) could be achieved using antigen-antibody reaction high-sensitively (detection limit: pg/ml order) and rapidly. Using this polymer-based 2D-PC, optical biosensor can be developed cost effectively. Furthermore, by using polymer as a base material for fabrication of 2D-PC, label-free detection of antigen-antibody reaction can be performed in visible region.
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Takahiro KITADA, Hiroto OTA, Xiangmeng LU, Naoto KUMAGAI, Toshiro ISU
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
171-178
Published: February 01, 2017
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Compact and room-temperature operable terahertz emitting devices have been proposed using a semiconductor coupled multilayer cavity that consists of two functional cavity layers and three distributed Bragg reflector (DBR) multilayers. Two cavity modes with an optical frequency difference in the terahertz region are realized since two cavities are coupled by the intermediate DBR multilayer. In the proposed device, one cavity is used as the active layer for two-color lasing in the near-infrared region by current injection and the other is used as the second-order nonlinear optical medium for difference-frequency generation of the two-color fundamental laser light. The control of the nonlinear polarization by face-to-face bonding of two epitaxial wafers with different orientations is quite effective to achieve bright terahertz emission from the coupled cavity. In this study, two-color emission by optical excitation was measured for the wafer-bonded GaAs/AlGaAs coupled multilayer cavity containing self-assembled InAs quantum dots (QDs). We found that optical loss at the bonding interface strongly affects the two-color emission characteristics when the bonding was performed in the middle of the intermediate DBR multilayer. The effect was almost eliminated when the bonding position was carefully chosen by considering electric field distributions of the two modes. We also fabricated the current-injection type devices using the wafer-bonded coupled multilayer cavities. An assemble of self-assembled QDs is considered to be desirable as the optical gain medium because of the discrete nature of the electronic states and the relatively wide gain spectrum due to the inhomogeneous size distribution. The gain was, however, insufficient for two-color lasing even when the nine QD layers were used. Substituting two types of InGaAs multiple quantum wells (MQWs) for the QDs, we were able to demonstrate two-color lasing of the device when the gain peaks of MQWs were tuned to the cavity modes by lowering the operating temperature.
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Hideki YAGI, Yoshihiro YONEDA, Mitsuru EKAWA, Hajime SHOJI
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
179-186
Published: February 01, 2017
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This paper reports dual-polarization In-phase and Quadrature (DP-IQ) modulators and photodetectors integrated with the 90° hybrid using InP-based monolithic integration technologies for 100/200Gb/s coherent transmission. The DP-IQ modulator was monolithically integrated with the Mach-Zehnder modulator array consisting of deep-ridge waveguides formed through dry etching and benzocyclobutene planarization processes. This DP-IQ modulator exhibited the low half-wavelength voltage (Vπ=1.5V) and the wide 3-dB bandwidth (f3dB > 28GHz). The photodetector monolithically integrated with the 90° hybrid consisting of multimode interference structures was realized by the butt-joint regrowth. A responsivity including total loss of 7.9dB in the waveguide was as high as 0.155A/W at a wavelength of 1550nm, and responsivity imbalance of the In-phase and Quadrature channels was less than ±0.5dB over the C-band. In addition, the low dark current (less than 500pA up to 85°C @ -3.0V) and the stable operation in the accelerated aging test (test condition: -5V at 175°C) over 5,000h were successfully achieved for the p-i-n-photodiode array with a buried heterostructure formed through the selective embedding regrowth. Finally, a receiver responsivity including intrinsic loss of 3dB in the polarization beam splitter was higher than 0.070A/W at a wavelength of 1550nm through the integration of the spot-size converter, and demodulation of 128Gb/s DP-QPSK and 224Gb/s DP-16QAM modulated signals was demonstrated for the compact coherent receiver using this photodetector integrated with the 90° hybrid. Therefore, we indicated that these InP-based monolithically integrated photonic devices are very useful for 100/200Gb/s pluggable coherent transceivers.
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Keita MOCHIZUKI, Tadashi MURAO, Mizuki SHIRAO, Yoshiyuki KAMO, Nobuyuk ...
Article type: INVITED PAPER
2017 Volume E100.C Issue 2 Pages
187-195
Published: February 01, 2017
Released on J-STAGE: February 01, 2017
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We have succeeded in developing three techniques, a precise lens-alignment technique, low-loss built-in Spatial Multiplexing optics and a well-matched electrical connection for high-frequency signals, which are indispensable for realizing compact high-performance TOSAs and ROSAs employing hybrid integration technology. The lens position was controlled to within ±0.3 µm by high-power laser irradiation. All components comprising the multiplexing optics are bonded to a prism, enabling the insertion loss to be held down to 0.8 dB due to the dimensional accuracy of the prism. The addition of an FPC layer reduced the impedance mismatch at the junction between the FPC and PCB. We demonstrated a compact integrated four-lane 25 Gb/s TOSA (15.1 mm × 6.5 mm × 5.6 mm) and ROSA (17.0 mm × 12.0 mm × 7.0 mm) using the built-in spatial Mux/Demux optics with good transmission performance for 100 Gb/s Ethernet. These are respectively suitable for the QSFP28 and CFP2 form factors.
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Takuro FUJII, Koji TAKEDA, Erina KANNO, Koichi HASEBE, Hidetaka NISHI, ...
Article type: PAPER
2017 Volume E100.C Issue 2 Pages
196-203
Published: February 01, 2017
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We have developed membrane distributed Bragg reflector (DBR) lasers on thermally oxidized Si substrate (SiO2/Si substrate) to evaluate the parameters of the on-Si lasers we have been developing. The lasers have InGaAsP-based multi-quantum wells (MQWs) grown on InP substrate. We used direct bonding to transfer this active epitaxial layer to SiO2/Si substrate, followed by epitaxial growth of InP to fabricate a buried-heterostructure (BH) on Si. The lateral p-i-n structure was formed by thermal diffusion of Zn and ion implantation of Si. For the purpose of evaluating laser parameters such as internal quantum efficiency and internal loss, we fabricated long-cavity lasers that have 200- to 600-µm-long active regions. The fabricated DBR lasers exhibit threshold currents of 1.7, 2.1, 2.8, and 3.7mA for active-region lengths of 200, 300, 400, and 600µm, respectively. The differential quantum efficiency also depends on active-region length. In addition, the laser characteristics depend on the distance between active region and p-doped region. We evaluated the internal loss to be 10.2cm-1 and internal quantum efficiency to be 32.4% with appropriate doping profile.
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