Hang Liu Fei Wu
Keiji GOTO Toru KAWANO Ryohei NAKAMURA
Takahiro SASAKI Yukihiro KAMIYA
Xiang XIONG Wen LI Xiaohua TAN Yusheng HU
Anton WIDARTA
Hiroshi OKADA Mao FUKINAKA Yoshiki AKIRA
Shun-ichiro Ohmi
Tohgo HOSODA Kazuyuki SAITO
Shohei Matsuhara Kazuyuki Saito Tomoyuki Tajima Aditya Rakhmadi Yoshiki Watanabe Nobuyoshi Takeshita
Koji Abe Mikiya Kuzutani Satoki Furuya Jose A. Piedra-Lorenzana Takeshi Hizawa Yasuhiko Ishikawa
Yihan ZHU Takashi OHSAWA
Shengbao YU Fanze MENG Yihan SHEN Yuzhu HAO Haigen ZHOU
Ryo KUMAGAI Ryosuke SUGA Tomoki UWANO
Jun SONODA Kazusa NAKAMICHI
Kaiji Owaki Yusuke Kanda Hideaki Kimura
Takuya FUJIMOTO
Yuji Wada
Fuyuki Kihara Chihiro Matsui Ken Takeuchi
Keito YUASA Michihiro IDE Sena KATO Kenichi OKADA Atsushi SHIRANE
Tomoo Ushio Yuuki Wada Syo Yoshida
Futoshi KUROKI
Jun FURUTA Shotaro SUGITANI Ryuichi NAKAJIMA Takafumi ITO Kazutoshi KOBAYASHI
Yuya Ichikawa Ayumu Yamada Naoko Misawa Chihiro Matsui Ken Takeuchi
Ayumu Yamada Zhiyuan Huang Naoko Misawa Chihiro Matsui Ken Takeuchi
Yoshinori ITOTAGAWA Koma ATSUMI Hikaru SEBE Daisuke KANEMOTO Tetsuya HIROSE
Hikaru SEBE Daisuke KANEMOTO Tetsuya HIROSE
Zhibo CAO Pengfei HAN Hongming LYU
Takuya SAKAMOTO Itsuki IWATA Toshiki MINAMI Takuya MATSUMOTO
Koji YAMANAKA Kazuhiro IYOMASA Takumi SUGITANI Eigo KUWATA Shintaro SHINJO
Minoru MIZUTANI Takashi OHIRA
Katsumi KAWAI Naoki SHINOHARA Tomohiko MITANI
Baku TAKAHARA Tomohiko MITANI Naoki SHINOHARA
Akihiko ISHIWATA Yasumasa NAKA Masaya TAMURA
Atsushi Fukuda Hiroto Yamamoto Junya Matsudaira Sumire Aoki Yasunori Suzuki
Ting DING Jiandong ZHU Jing YANG Xingmeng JIANG Chengcheng LIU
Fan Liu Zhewang Ma Masataka Ohira Dongchun Qiao Guosheng Pu Masaru Ichikawa
Ludovico MINATI
Minoru Fujishima
Hyunuk AHN Akito IGUCHI Keita MORIMOTO Yasuhide TSUJI
Kensei ITAYA Ryosuke OZAKI Tsuneki YAMASAKI
Akira KAWAHARA Jun SHIBAYAMA Kazuhiro FUJITA Junji YAMAUCHI Hisamatsu NAKANO
Seiya Kishimoto Ryoya Ogino Kenta Arase Shinichiro Ohnuki
Yasuo OHTERA
Tomohiro Kumaki Akihiko Hirata Tubasa Saijo Yuma Kawamoto Tadao Nagatsuma Osamu Kagaya
Haonan CHEN Akito IGUCHI Yasuhide TSUJI
Keiji GOTO Toru KAWANO Munetoshi IWAKIRI Tsubasa KAWAKAMI Kazuki NAKAZAWA
Advanced optical transmission fibers have enabled 40-Gb/s transmission over distances of up to 5200km with 100-km amplified spans. This paper will discuss a number of the enabling fiber properties including dispersion, dispersion slope, Raman gain efficiency, and polarization mode dispersion.
Sze Yun SET Chee Seong GOH Kazuro KIKUCHI
The generation of high repetition-rate optical pulse train using a passively mode-locked figure-8 fiber ring laser is presented. The laser employs a novel configuration incorporating a superstructure fiber Bragg grating. Pulse train with repetition rates up to 100GHz is possible and transform-limited pulses with pulsewidth below 1ps can be achieved with chirp compensation. The output pulses can further be reduced to 83fs with an external pulse compressor.
Young-Geun HAN Un-Chul PAEK Youngjoo CHUNG
We will present a novel core mode blocker fabricated with hydrogen loaded Ge-B co-doped fiber exposed to the electric arc discharge using local heat exposure. Tunable bandpass filter based on cascaded LPFGs with a core mode blocker inserted between the LPFGs will be also described. The characteristics are: 6.5-nm bandwidth, 30-nm tuning range, and 15-dB dynamic range, respectively. It can be very useful for application to wavelength stabilization and physical sensors.
Yunsong JEONG Woojin SHIN Hoon JEONG Kyunghwan OH
We have exploited a high-power-tolerant variable optical attenuator (VOA) based on the fused fiber coupler in the all-fiber structure. A newly designed VOA employs the external modulation by forcing an axial stress in the tapered region of the fused fiber coupler. In the tapered region, the axial stress changes the refractive index of silica glasses resulting in a change in the coupling coefficient of the coupler. In this paper, we explain the principle of the novel device, VOA, and the optimized fabrication of the fused fiber coupler for the attenuation. The changes of the transmission spectrum for the coupler and the optical power spectrum for pump laser diode (LD), whose center wavelength is 1.47µm, versus the axial displacement were verified by experiment. The possibility of the wavelength uniformity less than 1dB over the range of 1460-1500nm was also obtained by another coupler under a different fabrication condition. The polarization-dependent loss (PDL) at 1.47µm wavelength was 0.65dB for a maximum displacement of 150µm. The designed device has an attractive feature of another output port of the coupler available as a monitoring tap. The device showed a high attenuation above 34dB and an insertion loss below 0.15dB. The all-fiber structure can provide less alignment, which in turn provides a high power tolerance. This novel design, moreover, has a simple and cost-effective structure.
Hiroyasu SONE Masaaki IMAI Yoh IMAI Yasuhiro HARADA
It is found that the supercontinuum spectrum is generated from cross-phase modulated soliton pulses which are propagated through a dispersion-flattened/decreasing fiber with low birefringence. The cross-phase modulation is achieved by exciting two orthogonally polarized modes in a birefringent fiber and the effect of input azimuth of linearly polarized pulses is discussed theoretically and numerically.
Kiyotaka SASAGAWA Kazushi KUSAWAKE Keiichiro KAGAWA Jun OHTA Masahiro NUNOSHITA
Self-pulsation of Nd3+-doped fluoride fiber laser is experimentally and theoretically demonstrated using a Tm3+-doped fluoride fiber pumped at 808 nm as a saturable absorber. Self-pulsation at finite pump power predicted by linear stability analysis is confirmed through experiments, achieving a pulse width and peak power of
The rapid spread of the Internet has led to the construction of broadband networks and the steady installation of optical fiber to the home. The air blowing cable system makes it possible to construct optical fiber networks efficiently and economically when the service demand is unpredictable. We have installed this system for intra-building applications. In this paper, we report ways of applying the air blowing system to aerial distribution using access networks. We showed that certain problems must be overcome before the system can be used for aerial applications. We describe these problems, which include those related to installation distance and environmental conditions and also the system components. In particular, the characteristics at high temperature were degraded because of a reduction in the flux. However, we were able to improve these characteristics by adopting the flexibility of the optical fiber unit.
Yoshiyasu UENO Morio TAKAHASHI Shigeru NAKAMURA Kouichi SUZUKI Takanori SHIMIZU Akio FURUKAWA Takemasa TAMANUKI Kazuo MORI Satoshi AE Tatsuya SASAKI Kazuhito TAJIMA
Control scheme for accurately optimizing (and also automatically stabilizing) the interferometer phase bias of Symmetric-Mach-Zehnder (SMZ)-type ultrafast all-optical switches is proposed. In this control scheme, a weak cw light is used as a supervisory input light and its spectral power ratio at the switch output is used as a bipolar error signal. Our experimental result at 168-Gb/s 16:1 demultiplexing with a hybrid-integrated SMZ switch indicates the feasibility and the sensitivity of this control scheme.
Kenichiro TSUJI Naoyuki MATSUSHITA Noriaki ONODERA Masatoshi SARUWATARI
Wavelength conversion using the cross-gain modulation (XGM) of amplified spontaneous emission (ASE) in a traveling-wave type semiconductor optical amplifier (TW-SOA) is theoretically studied. Taking into account the spatial and temporal variations of carrier density along the SOA length, output signal and converted ASE waveforms are analyzed. We also reveal the dependency of the signal and converted ASE waveforms on input signal power and repetition frequency, and confirm that numerical analyses well agree with the experimental results. Finally we qualitatively clarify the way to improve frequency response by simulating eye-diagrams for long SOAs and assist light pumping for the first time.
Ryusuke NAKASAKI Mitsumasa ITO Satoshi ARAKAWA Akihiko KASUKAWA
We fabricated 1.3µm AlGaInAs inner-stripe laser diodes (LDs), employing a GaInAsP waveguide layer and an n-InP current blocking layer. We compared the effects of the thickness of n-InP current blocking layer. A blocking layer with 500nm thick restricts the leakage current significantly. The inner-stripe LD was compared with the conventional ridge LD. I-L characteristics of both types of LDs were measured. Threshold currents of the inner-stripe LD and the ridge LD were 8.5 and 10.6mA, respectively. A threshold current of the inner-stripe LD is smaller than that of ridge LD. And the resistance of the inner-stripe LD was a few ohms lower than that of the ridge LD. Output power of 88mW was obtained at 200mA with 300µ m-long cavity. This was twice the power of a conventional ridge laser. The characteristic temperature of the inner-stripe LD was obtained 76 K from 20 to 85
Katsuhiko HIRABAYASHI Chikara AMANO
We have formed simple polarization-controller arrays by inserting liquid crystal (LC) in trenches cut across planar lightwave circuits (PLCs). We fabricated LC layers for use as polarization controllers on PLCs in two ways; in one, the ultra-thin layer of LC is held in a cell that is inserted into a trench on the PLC while in the other, the trench is directly filled with the LC. The ultra-thin LC cell can change the phase of 1.55-µm light from 0 to 3π while the LC filling can change the phase of light at the same wavelength from 0 to 12π below 5Vrms. Two former parallel-aligned ultra-thin LC cells, where the directions of alignment of the liquid crystals are rotated by 45
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Jun SHIBAYAMA Koichi SADANO Junji YAMAUCHI Hisamatsu NAKANO
A bent-waveguide-based multimode interference (MMI) demultiplexer is designed for the operation at 0.85- and 1.55-µm wavelengths using the three-dimensional semi-vectorial beam-propagation method. First, it is shown that the use of a straight MMI waveguide results in a long coupler length of more than 1000µm for wavelength demulitplexing. To reduce the coupler length, we next introduce a bent MMI waveguide. Bending with a radius of 1500µm leads to a coupler length of less than 200µm. After designing two output waveguides connected to the MMI section, we finally choose a coupler length to be 175µm for efficient demultiplexing properties. Consequently, an output power of more than 90% can be obtained, leading to a low insertion loss of 0.34dB at both 0.85- and 1.55-µm wavelengths. The demultiplexer achieves small polarization dependence, i.e., less than 2dB difference in contrast and 0.02dB difference in insertion loss.
Myung-Hyun LEE Suntak PARK Jung Jin JU Seung Koo PARK Jung Yun DO Jong-Moo LEE
Multi-channel arrayed waveguide devices are crucial for WDM optical communication systems. Multi-channel arrayed polymer-based waveguide devices have been important for reducing cost and size. This paper introduces two types of multi-channel arrayed polymer-based waveguide devices. We designed and fabricated a four-channel arrayed 2
A new device structure for electrooptic tunable wavelength filter is reported. Finger electrode electrooptic mode converters are placed on an optical waveguide. The drive voltage amplitude is changed along the propagation distance with a sinusoidal function. Changing the spatial period of sinusoidal voltage results in wavelength tuning. Structure uses interleaved mode converter groups generating cosine and sine function mode conversion strengths.
Electron field emission from diamond, diamond-like carbon, carbon nanotubes and nano-structured carbon is compared. It is found that in all practical cases, emission occurs from regions of positive electron affinity with an emission barrier of
Electron emissions from single-crystalline diamond surfaces by internally exciting electrons from the valence to conduction bands have been investigated. Monte Carlo simulations have been employed to estimate the impact ionization rates of carriers in diamond under high electric fields up to 1
Field emission display (FED) is evolving as a promising technique of flat panel displays in the future. In this paper, various carbon based nanostructures are acted as cathode materials for field emission devices. Dendrite-like diamond-like carbon emitters, carbon nanotubes, carbon nanotips are synthesized by microwave plasma chemical vapor deposition. Many factors affect the performance of field emitters, such as the shape, work function and aspect ratio of emission materials. Modified process of carbon based nano-materials for enhancing field emission efficiency are included intrinsic and extrinsic process. These reformations contain the p-type and n-type doping, carburization and new ultra well-aligned carbon nano-materials. It is found that carbon nano-materials grown on micropatterned diode show higher efficiency of FED. In addition, to achieve a low- turn-on field, the novel scheme involving a new fabrication process of gated structure metal-insulator-semiconductor (MIS) diode by IC technology is also presented.
Nan JIANG Kazuhito NISHIMURA Yoshihiro SHINTANI Akio HIRAKI
Seeding substrates with diamond nanocrystals has been considered to be a promising nondestructive pretreatment method for growth of diamond films. However, its application is strongly impeded by the segregation of diamond nanocrystals on substrates. In the present study, we suggest a very simple but effective seeding way ("sandwich" (SW) seeding way) to prevent nanocrystals from segregation. By the SW seeding way, the diamond nanocrystals can be nearly uniformly dispersed on Si substrates with the areal density of the order of 108cm-2. On the nano-seeded Si substrates the continuous and homogeneous diamond films can be successfully fabricated using a microwave plasma enhanced chemical-vapor-deposition (MPECVD) equipment. The cross-sectional transmission electron microscopy (TEM) images reveal that compare with the diamond films grown on the Si substrates pretreated by the conventional scratching method, the films deposited on the nano-seeded Si substrates present a much flatter interfacial structure, suggesting that the SW seeding way can effectively reduce the interface coarseness.
Akio HIRAKI Bukinakere S. SATYANARAYANA
We report field emission from multilayered cathodes grown on silicon and glass substrates. The cathode consist of a layer of nanoseeded diamond and overlayers of nanocluster carbon (sp2 bonded carbon) and tetrahedral amorphous carbon (predominantly sp3 bonded carbon). These films exhibit good field emission characteristics with an electron emission current density of 1µA/cm2, at a field of 5.1V/µm. The multilayered cathodes on silicon substrates exhibit even lower emission threshold field of about 1-2V/µm for an emission current density of 1µA/cm2. The emission is influenced by the nanoseeded diamond size and concentration and the properties of the nano carbon over layer.
Kazuhito NISHIMURA Nan JIANG Akio HIRAKI
A type of carbon nanoform (carbon nanowalls: CNWs) has been successfully deposited on both Ni wafers and Ni wires using dc plasma chemical-vapor-deposition (CVD) method. Transmission electron microscopy (TEM) and Raman spectroscopy were used to characterize CNWs' microstructure. It is found that CNWs are well crystallized, and each CNW consists of several pieces of curved graphene sheets, presenting a quasi-two-dimensional geometry. The average length and width of CNWs are about 2-4µm, while their thickness is less than 7nm. Field emission measurement showed that such CNW films exhibited the excellent electron emission efficiency, comparable to the high-grade carbon nanotube (CNT) emitters. The threshold field defined as the field to obtained 1µA/cm2 is less than 1V/µm and the electrical field for 1mA/cm2 current density is only about 1.5V/µm. Moreover, the CNWs have stable emission behaviors, and we have successfully fabricated a kind of high-brightness lamps based on the CNW coated Ni wires.
Akimitsu HATTA Taku SUMITOMO Hideo INOMOTO Akio HIRAKI
Electron field emission from polycrystalline diamond films has been investigated. Electron emission was measured locally at randomly chosen point on a diamond film fabricated by a microwave plasma chemical deposition method. In the original film, there were some points with a large emission current where flaws were found after the measurements, some points with a small and stable emission current without any flaw, and the other points with no emission. At the point of no emission, the film was electrically broken down by applying a high voltage. After the intentional breaking down, a small and stable emission always appeared there with no flaw. The maximum emission current extracted from an emission site was usually 1µA with no structural flaw found after the measurements. By using a simple model of emission site consisting of a core conductor embedded in insulator, the limitation of emission current is estimated from heating by the current and heat transfer to the insulator.
Toshio ITO Katsuaki MAGARI Yasuo SHIBATA Yoshihiro KAWAGUCHI Yasuhiro KONDO Yuichi TOHMORI Yasuhiro SUZUKI
We propose a novel method of precisely measuring the polarization dependence of single pass gain (PDG) in a semiconductor optical amplifier integrated with spot-size convertors (SS-SOA). By averaging the signal gain of a SS-SOA over a wide wavelength range using the amplified spontaneous emission (ASE) of an erbium doped fiber (EDF), the PDG can be accurately estimated. This is because the influence of gain ripples on the measurement results are drastically reduced. We successfully evaluated the PDG of an angled-facet SS-SOA, even before the process of anti-reflection coating, within a small error of 0.5dB. The EDF-ASE technique is useful in sampling tests and selecting angled-facet SS-SOA chips from wafers. The polarization dependence of the coupling efficiency (PDCE) between a SS-SOA and optical fiber is also evaluated by measuring the photo-current of the active layer for TE and TM input signals. It is possible, therefore, to specify the polarization characteristics of the active region and spot-size converter region, which are indispensable parameters for the design of the SS-SOA.
We demonstrate a mode-locked fiber laser (MLFL) method for measuring the chromatic dispersion of long transmission fiber. In this method, device under test (DUT) is inserted in the laser cavity, and the chromatic dispersion is measured by the shift of mode-locking frequency when the lasing wavelength is changed. The experimental results of the MLFL method for a 5km-long single-mode fiber had good agreement with the conventional phase-shift method.
Hisako SATO Mariko OHTSUKA Kazuya MAKABE Yuichi KONDO Kazumasa YANAGISAWA Peter M. LEE
This paper presents an efficient application of hot-carrier reliability simulation to delay libraries of 0.18µm and 0.14µm gate length logic products. Using analysis of simple primitive inverter cells, a design rule was developed in restricting signal rise time, and delay libraries of actual products were screened to check whether the rise time restrictions were met. At 200MHz, maximum rise time (0-100%) triseMAX was 0.8nsec (17% of duty) under Δtd/td = 5%. For a 800,000 net product, only 25 simulations were done (each less than one minute CPU time) for the internal devices with screening done for this logic process. 30 nets were caught, but judged reliable due to their reduced duty.
Decreased power dissipation and transient voltage drops in CMOS power distribution networks are important for high-speed deep submicrometer CMOS integrated circuits. In this paper, three CMOS buffers based on the charge-transfer, split-path and bootstrapped techniques to reduce the power dissipation and transient voltage drop in power supply are proposed. First, the inverted-delay-unit is used in the low-power inverted-delay-unit (LPID) CMOS buffer to eliminate the short-circuit current of the output stage. Second, the low-swing bootstrapped feedback-controlled split-path (LBFS) CMOS buffer is proposed to eliminate the short-circuit current of the output stage by using the feedback-controlled split-path method. The dynamic power dissipation of the LBFS CMOS buffer can be reduced by limiting the gate voltage swing of the output stage. Moreover, the propagation delay of the LBFS CMOS buffer is also reduced by non-full-swing gate voltage of the output stage. Third, the charge-recovery scheme is used in the charge-transfer feedback-controlled 4-split-path (CRFS) CMOS buffer to recovery and pull up the gate voltage of the output stage for reducing power-delay product and power line noise. Based on HSPICE simulation results, the power-delay product and the transient voltage drop in power supply of the proposed three CMOS buffers can be reduced by 20% to 40% as compared to conventional CMOS tapered buffer under various capacitive load.
Jin-Hyeok CHOI Seong-Ik CHO Mu-Hun PARK Young-Hee KIM
We present a new multi-stage charge pump that is suitable for low-voltage operation, and in particular for low voltage flash memory. Compare to the Dickson charge pump and previously reported modified Dickson charge pumps, the proposed charge pump offers the improved pumping voltage gains. The proposed charge pump is composed of a pair of pumps and utilizes the internal boosted voltages of one side of the paired pumps as the charge transferring voltages to the other side. The simulated and measured results indicate that the proposed pump is highly efficient in overcoming both the pumping gain decrease and the current driving capability degradation caused by the threshold voltage of the charge-transfer gate.
Takako YASUI Tomofumi FURUTA Tadao ISHIBASHI Hiroshi ITO
The power dissipation tolerances for InP/ InGaAs uni-travelling-carrier photodiodes (UTC-PDs) and pin-PDs under high power optical inputs are compared. Catastrophic failures occur at constant power dissipations of 240 and 160mW for the UTC-PDs and pin-PDs, respectively. Scanning electron microscope observations confirm that the areas of destruction are located in the high electric-field region in the depletion layer.
Young Chul LEE Ki Chan EUN Chul Soon PARK
We have devised and implemented a new low-loss microstrip transmission structure on LTCC substrate by including void cavities in the dielectric layer between conductor strip and ground plane. Measurements of λ/4 T-resonators with the novel microstrip structure reveal total loss of 0.0126dB/mm and Q-factor of 267 at 15.85GHz. The dielectric loss is analyzed as small as 0.0005dB/mm at the frequency, and that is equivalent to an improvement of a factor of 18 compared to the conventional LTCC microstrip structure. The proposed microstrip structure with the embedded void cavities is suited for low loss LTCC based RF-MCM applications.