Fabrication of 64×64 arrayed-waveguide grating multiplexer onsilicon

A 64 channel arrayed-waveguide multiplexer with 0.4 nm (50 GHz) channel spacing at 1.55 μm has been fabricated using SiO₂-Si waveguides. The authors obtained a crosstalk of less than -27 dB to neighbouring and all other channels. The on-chip insertion loss ranges from 3.1 to 5.7 dB for central and peripheral output ports, respectively     

Network architecture for optical path transport networks

This paper proposes a new layered transport network architecture on which the WDM optical path network can be effectively created. The optical path network will play a key role in the development of the transport network that will realize the bandwidth-abundant B-ISDN. This paper extends the layered transport network architecture described in ITU-T Recommendation G.803 which is applied in existing SDH networks. First, we elucidate an application example of WDM optical path networks. Next, we propose a new layered architecture for WDM-based transport networks that retains maximum commonality with the layered architectures developed for existing B-ISDN networks. The proposed architecture is composed of circuit layer networks, electrical path layer networks, optical layer networks, and physical media (fiber) networks. The optical layer is divided into an optical path layer and an optical section layer. The optical path layer accommodates electrical paths. Optical section layer networks are divided into optical multiplex section (OMS) layer networks and optical repeater section (ORS) layer networks. The OMS layer network is concerned with the end-to-end transfer of information between locations transferring or terminating optical paths, whereas the ORS layer is concerned with the transfer of information between individual optical repeaters. Finally, a detailed functional block model of WDM optical path networks, the function allocation of each layer, and an optical transport module (OTM) are developed     

Development of 170 GHz/500 kW gyrotron

A development of 170GHz/500kW level gyrotron was carried out as R&D work of ITER. The oscillation mode is TE_31,8. In a short pulse experiment, the maximum power of 750kW was achieved at 85kV/40A. The efficiency was 22%. In the depressed collector operation, 500kW/36%/50ms was obtained. The maximum efficiency of 40% was obtained at P_RF=470kW whereas the power decrease by the electron trapping was observed. Pulse extension was done up to 10s at P_RF=170kW with the depressed collector operation. The power was limited by the temperature increase of the output window.     

Growth of (111) HgCdTe on (100) Si by MOVPE using metalorganic tellurium adsorption and annealing

(lll)B CdTe layers free of antiphase domains and twins were directly grown on (100) Si 4°-misoriented toward<011> substrates, using a metalorganic tellurium (Te) adsorption and annealing technique. Direct growth of (lll)B CdTe on (100) Si has three major problems: the etching of Si by Te, antiphase domains, and twinning. Te adsorption at low temperature avoids the etching effect and annealing at a high temperature grows single domain CdTe layers. Te atoms on the Si surface are arranged in two stable positions, depending on annealing temperatures. We evaluated the characteristics of (lll)B CdTe and (lll)B HgCdTe layers. The full width at half maximum (FWHM) of the x-ray double crystal rocking curve (DCRC) showed 146 arc sec at the 8 |im thick CdTe layers. In Hg_1−xCd_xJe (x = 0.22 to 0.24) layers, the FWHMs of the DCRCs were 127 arc sec for a 7 (im thick layer and 119 arc sec for a 17 (im thick layer. The etch pit densities of the HgCdTe were 2.3 x 106 cm2 at 7 ^m and 1.5 x 106 cm-2 at 17 um.     

Direct growth of CdTe on (100), (211), and (111) Si by metalorganic chemical vapor deposition

CdTe epilayers were grown directly on (100), (211), and (111) silicon substrates by metalorganic chemical vapor deposition (MOCVD). The crystallinity and the growth orientation of the CdTe film were dependent on the surface treatment of the Si substrate. The surface treatment consisted of exposure of the Si surface to diethyltelluride (DETe) at temperatures over 600°C prior to CdTe growth. Direct growth of CdTe on (100) Si produced polycrystalline films whereas (lll)B single crystals grew when Si was exposed to DETe prior to CdTe growth. On (211) Si, single crystal films with (133)A orientation was obtained when grown directly; but produced films with (211)A orientation when the Si surface was exposed to DETe. On the other hand, only (lll)A CdTe films were possible on (111) Si, both with and without Te source exposure, although twinning was increased after exposure. The results indicate that the exposure to a Te-source changes the initial growth stage significantly, except for the growth on (111) Si. We propose a model in which a Te atom replaces a Si atom that is bound to two Si atoms.     

Eight-channel flat spectral response arrayed-waveguide multiplexer with asymmetrical Mach-Zehnder filters

An eight-channel flat spectral response arrayed-waveguide grating (AWG) multiplexer with asymmetrical Mach-Zehnder filters has been fabricated on the planar lightwave circuit (PLC). The monotonic spectral loss characteristics of AWG have been canceled by the opposite spectral response in the asymmetric MZ filter. The 1.5 dB bandwidth of 141 GHz and 3 dB bandwidth of 159 GHz are obtained for the 200 GHz channel spacing. The 1.5 dB bandwidth becomes 1.8 times wider than that of the conventional AWG. Crosstalks to neighboring and all other channels are less than -24 dB and the on-chip insertion losses range from 7.0 to 7.4 dB, respectively.     

Development of a compact high-density microbial hydrogen reactor for portable bio-fuel cell system

The development of a compact high-density microbial reactor for hydrogen production is described with possible implications to use as a portable bio-fuel cell system. To construct the compact bioreactor, mainly, the cell density and immobilization methods were optimized in this paper. The encapsulation of hydrogen producing bacterium, Escherichia coli strain MC13-4, in alginate gel beads provided approximately three-fold increase in hydrogen production in comparison with the free cell suspension. The immobilized cells (cell density; O.D. 100) and 500 mM glucose solution were packed into a 20 mL glass bottle that was connected to the fuel cell. This system has generated electricity of over 20 mW for 20 min.     

Preparation and properties of CuInS2 thin film prepared from electroplated precursor

Thin CuInS₂ films were prepared by sulfurization of Cu/In bi-layers. First, the precursor layer was electroplated onto the treated surface of Mo-coated glass. Observation of the cross-section prepared by focused ion beam (FIB) etching revealed that the void-free film was initially formed on the top surface of the precursor layer and continued to grow until the advancing front of the film reached the Mo layer. The nucleation of voids near the bottom of the CuInS₂ film followed. To determine whether the condition of the Cu/In alloy influences the CuInS₂ quality we investigated the Cu/In alloy state using FIB. We found that the annealed precursor of low Cu/In ratio (1.2) has several voids in the mid position in the layer compared with Cu-rich precursor (1.6). The cross-sectional view of the Cu-rich absorber layer is uniform compared with the low copper absorber layer. Thin film solar cells were fabricated using the CuInS₂ film (Cu/In ratio: 1.2) as an optical absorber layer. It was found that the optimization of a sulfurization period is important in order to improve the cell efficiency. We have not yet obtained good results with high Cu-rich absorber because of a blister problem. This blister was found before sulfurization. So, we are going to solve this blister problem before sulfurization.     

370 W output power GaN-FET amplifier for W-CDMA cellular base stations

A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power.