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Highly transparent, low-resistance SnO 2 :F films suitable as a substrate material for thin-film CdS/CdTe solar cells have been developed on 10 × 10, 30 x 60 and 82 x 71 cm 2 glass substrates by an ultrasonic spray pyrolysis (pyrosol) process. Dimethyltin dichloride, NH 4 F and HF dissolved in water served as the source solution. A fine spray of the source solution has been transported using air as a carrier gas onto hot glass plates in a belt furnace maintained at 500-530°C. A very high growth rate of > 15 nm/s and a high throughput of 3 min/glass plate (82 x 71 cm 2 size) have been achieved with films showing greater uniformity, low sheet resistance and high optical transmission. Typical films exhibited a thickness of 500 nm, a sheet resistance of 8.1 Ω/sq., a mobility of 43.8 cm 2 /V s and a donor concentration of 3.5 x 10 20 cm -3 . A thin-film CdS/CdTe solar cell fabricated on a 30 x 60 cm 2 SnO 2 :F transparent conducting substrate exhibited a solar energy conversion efficiency maximum of 14.95% for 1 cm 2 cell and an average efficiency of 14.24% for 178 isolated 1 cm 2 cells.

Highly efficient large area (10.5%, 1376 cm2) thin-film CdS/CdTe solar cell sub-module has been fabricated. Very recently we also have fabricated a very large area sub-module of aperture area 5413 cm2 exhibiting a conversion efficiency of 8.4%. Such a high efficiency has been achieved by depositing all the constituent films such as SnO2: F, CdS and CdTe having greater uniformity and better quality under atmospheric pressure conditions. A post deposition treatment of CdTe surface with CdCl2 has been optimized to improve the overall solar cell output performance significantly.

The dependence of the leakage current in 1.3-/spl mu/m InGaAsP buried heterostructure (BH) lasers with p-n-p-n current blocking layers on well number, mesa width, and carrier density has been analyzed using a two-dimensional device simulator and compared with the electroluminescence (EL) emitted from InP layers. The analysis of the minority carrier flow reveals that the electron current flowing through the p-n-p-n current blocking layers is the dominant component of the leakage current. The measured EL intensity has two peaks at both sides of the n-blocking layer apart from the active layer. The EL intensity decreases with increasing well number and carrier density of the p-blocking layer, and increases with increasing mesa width. These results are consistent with the simulations.

High-efficiency CdSCdTe solar cells with thin CdS film have recently been developed. Semiconductive layers of CdS via the CVD method and of CdTe via the CSS method were deposited on an ITO/#7059 substrate. Cell performance depends primarily on the thickness of CdS film, and the conversion efficiency is highest for a CdS film thickness of around 60 nm. Since the CdS film thickness decreases by about 30% during deposition of the CdTe layer, a thickness of 95 nm is required to obtain a 60 nm-thick CdS film after deposition of a CdTe layer. By observing the CdS film during the CdTe deposition process, a decrease was detected before CdTe layer completely covers the surface of the CdS film. By optimizing the thickness of CdS film, an efficiency of 15.12% for the best cell under AM 1.5 verified at JQA was obtained. This fabrication process has good reproducibility; 92.5% of 1 cm2 solar cells fabricated under the same conditions have efficiencies above 14%.

We have studied reliability of 680-nm visible laser diodes (LDs) with a window-mirror structure formed by zinc-diffusion-induced disordering of GaInP quantum wells. Aging tests under the condition of CW output power in the range of 50-100 mW for ambient temperature from 40/spl deg/C to 70/spl deg/C have been carried out for 650-/spl mu/m-long LDs and 900-/spl mu/m-long LDs with three kinds of the front facet reflectivities (1.5%, 6% and 13%). In all tests, laser operation was stable for over 5000 h. For example, reliable 500-10000-h operation of the 900-/spl mu/m LDs was realized under the conditions of output power of 50 mW at 70/spl deg/C, 70 mW at 60/spl deg/C, and 100 mW at 40/spl deg/C for the first time. By various aging test results, dependence of the temperature and the output power on increase of the operating current has been investigated. Also, influences of the facet reflectivities and the cavity lengths on the reliability have been studied with focus on the optical power density and the current density. Consequently, it has been clarified that the degradation of the window LDs rather strongly depends on the operating current density than the optical power density. Moreover, it has been proven that the reliability of the window LDs is effectively improved by the reduction of the operating current density due to extension of the cavity length.

Strained-layer multiquantum-well distributed-feedback (MQW-DFB) lasers at a wavelength of 1.3 /spl mu/m operating from -40/spl deg/C to 85/spl deg/C without any coolers are demonstrated. Extremely low threshold current of 17 mA at 85/spl deg/C and operation current of 37 mA at 5 mW and 85/spl deg/C are obtained. To the best of our knowledge, each of them is the lowest value so far reported in InGaAsP-InP based DFB lasers. The lasers also realize low distortion of less than -50 dBc at 65/spl deg/C in 78-channel composite second order distortion (CSO) measurements. An experimental estimation of the leakage current in buried heterostructure presents that the distortion at high temperatures is mostly dominated by the carrier overflow from an active layer, not by the leakage current flowing through current blocking layers. On the basis of the leakage current analysis, a laser structure including the active layer and the current blocking layer is chosen to achieve low distortion over a wide-temperature-range. The uncooled distributed-feedback (DFB) laser we have developed is very useful for several channel transmission in CATV systems.

CdS/CdTe solar cells have attracted attention recently for their potential as low-cost, high-efficiency solar cells of the future. It is because the CdTe layer (used for photoelectric conversion) has a bandgap energy of 1. 51 eV, which corresponds well to sunlight spectra, and the direct transition type energy band structure enables formation of thinner films. We have already industrialized CdS/CdTe solar cells in mass production stage using a printing-sintering process, as large-area modules for electric power generation(Higuchi et al. , 1993, Omura et al. , 1991), and as cells for indoor applications (primarily in calculators. Suyama et al. , 1986). However, this solar cell has a conversion efficiency of approximately 6%. Recently, there has been considerable research into thin-film CdS/CdTe solar cells which have a thinner CdS film formed by CVD or CBD (Britt et al. , 1993) process, and thus are photosensitive to light with wavelengths of 500 nm or less. At present stage of our art, in solar cells formed by the CSS with a CdTe film on CVD CdS, a conversion efficiency of 15. 05% has been obtained in cells with an area of 1 cm2 (verified at JQA).

The screen printed CdS/CdTe hetero-junctions formed on the (0001), (1120), (1010) surfaces of CdS single crystals have been studied by an X-ray double crystal spectrometer, electron diffraction, transmission electron microscopy (TEM), and EBIC. For CdS/CdTe formed on the CdS (0001) structure, the epitaxiality of the CdTe layer formed on (0001) of CdS was better than that formed on the other surfaces. The diffusion length of minority carriers formed on the single crystal CdS was found to be larger than that of sintered CdS/CdTe junction prepared by the screen printing method especially for the junctions grown on the (0001) plane of CdS.

Theoretical and experimental investigations on the real-time transmission of 3-D images formed by parallax panoramagrams are described. At the image-taking station, a 3-D image is optically decomposed into line images, which can be directly handled by a high resolution TV set. By registering a lenticular sheet to the reproduced line images on a monitor screen, the reconstructed 3-D image is seen by the naked eye. By using an ordinary color TV set with a 350-line resolution and a cylindrical lens array with a 3-mm pitch, 3-D color images composed of thirty-five elements in the horizontal direction and seen from four directions are successfully transmitted and reconstructed with clear parallax.

An outline is given of a constructed model rotor and the preliminary experimental results are described. The model rotor was excited up to a rated current of 2000 A without training. The normal zone propagating velocities were measured in a rotating cryostat and were also calculated using the estimated heat transfer coefficients. By considering the change in the voltage drops after the normal transition, minimum burn-out current were found. If the operating current is smaller than this current, the conductor will not burn out even after the normal transition. This minimum burn-out current could be used as a safety current criterion.

High-power GaInP QW laser diodes with a window-mirror-structure lasing at a wavelength of around 650 nm have been fabricated. The maximum light output power over 150 mW has been realized without optical mirror damage. In addition, the laser shows the fundamental-mode-operation at 50 mW and the dynamic characteristics sufficient for recordable digital versatile disc (DVD) applications. The lasers have been operating for 2000 h under the condition of CW, 50 mW, and 60/spl deg/C, for the first time.

For the improvement of the transparency of CdS window layers produced by the printing and sintering method, a new substrate structure is proposed and examined. It is found that insertion of a TiO/sub 2/ and SiO/sub 2/ mixed layer between the glass substrate and CdS window layer diminishes the pores in CdS window layer. This is due to the good wettability between the CdS layer and TiO/sub 2/-SiO/sub 2/. A CdTe solar cell with this CdS layer (2.8/spl times/10 cm/sup 2/) has a high J/sub sc/ of 21 mA/cm/sup 2/. Another trial to achieve high package factor (the ratio of active-area/total-area) and high area productivity have also been carried out. By developing a wide-width writing method laser scribed CdTe/C double layer, the package factor increases from 85% to 90% and an efficiency of 8.7% is obtained in a 30/spl times/40 cm/sup 2/ submodule. >

By reduction of the operating current density due to a long cavity length of 900 /spl mu/m, reliable 5,000-hour operation of 680-nm window lasers has been realized under the conditions of 70 mW at 60/spl deg/C and 100 mW at 40/spl deg/C for the first time.

The DFB-LD with a width-tapered waveguide lens is fabricated and narrow beam divergence property is realized. Excellent light output-current (L-l) characteristics in wide-temperature range and error-floor-free transmission at 622 Mbps-40 km are also confirmed. It is promising for the surface-mountable DFB-LD modules.

We report on a COD (catastrophic optical damage) free 1.02 /spl mu/m laser diode with a window structure, which is formed by a quantum-well intermixing technique using Si ion implantation. Thermally-limited maximum power of 450 mW and kink free power over 200 mW are realized. Stable operation is obtained over 5000 hours under the condition of 50 centigrade, 150 mW.

We have fabricated a distributed-feedback laser diode (DFB-LD) with monolithically integrated electroabsorption modulator (EAM), which has small chirp characteristics (effective /spl alpha/ parameter =0.2). 2.5 Gbps-700 km penalty-free transmission without any intentional pre-biasing or self phase modulation effect is successfully demonstrated using the EAM-LD.

Recent advances in ultra-thin silicon-on-insulator (SOI) technology have made partially depleted (PD)-SOI-CMOS a promising candidate for use in high-speed circuits. However, some breakthroughs must still be made, the most important of which would be understanding and control of hysteretic behavior. Some hysteretic characteristics have been analyzed, and some methods to suppress this behavior have been proposed (Assaderaghi et al., 1994; Houston et al., 1998; Maeda et al., 1998; Wei et al., 1998; Pelella et al., 1999). However, the operation-period dependent circuit-delay is not sufficiently understood. In this paper, closed form analysis was used to analyze the operation-period-dependent circuit delay, and the results were confirmed with circuit simulators.

Passive mode-locking (ML) operation in semiconductor quantum-well (QW) lasers with Fabry-Perot (FP) cavities is investigated theoretically and experimentally. Structural and operational conditions for a semiconductor QW laser to exhibit ``amplitude modulation (AM)'' or ``frequency modulation'' ML operations are investigated by numerical analysis based on a semiclassical laser model. It is shown experimentally that clear AM ML pulses self-build and persist under continuous current injection in ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}\mathrm{As}/{\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{As}}_{y}{\mathrm{P}}_{1\ensuremath{-}y}/\mathrm{InP}$-based FP QW lasers with cavity lengths of $300\ensuremath{-}600 \ensuremath{\mu}\mathrm{m}.$ The observed ML features are explained in terms of the laser model.

Strained-layer MQW-DFB lasers at a wavelength of 1.3 micrometers operating from -40 degree(s)C to 85 degree(s)C without any coolers are demonstrated. On the basis of the leakage current analysis, a laser structure including the active layer and the current blocking layer is chosen to achieve low distortion over wide-temperature-range. Extremely low threshold current of 17 mA at 85 degree(s)C and operation current of 37 mA at 5 mW and 85 degree(s)C are obtained. The lasers realize low distortion of less than -50 dBc at 65 degree(s)C in 78-channel CSO measurements. Furthermore, a fabricated laser module with a coaxial package also achieved low CSO values of -55 dBc under 16-channel loading in the temperature range from -40 degree(s)C to 85 degree(s)C. This uncooled DFB laser module is very useful for return path application in CATV systems.

A high-sensitive surface mount PD preamplifier module has been developed by applying a passive alignment structure to a low-capacitance surface-illuminated PD. The sensitivity of over - 36 dBm has been obtained for 622 Mb/s signal.

An integrated electro-absorption modulator-distributed feedback laser with a very low carrier-concentration active layer has been developed. It exhibits excellent chirp characteristics and a 20 GHz bandwidth even at zero offset-bias operation.

The 780nm 35mW I2SPB lasers(Inverted Inner Stripe Laser with a p- GaAs Buffer Layer) with a thin active layer have been successflly developed by employing MOCVD. Accelerated aging tests on the ISPB lasers with the cavity length of 400iim at 60 °C, 30mW project lifetimes (MTTF) greater than l0000hrs. The narrow standard deviations of beam divergences parallel and perpendicullar to the junction plane, respectively 0.18 and O.2Odeg, are achieved. The small astigmatic distance less than 6iim and the high optical S/N ratio more than 65dB (at f=2OkHz, BW=300Hz and P=3OmW) are obtained. These exellent results indicate that the I2SPB lasers are available for the Magneto-Optical Disk (MOD) applications.

High efficiency cadmium sulfide (CdS)/cadmium telluride (CdTe) solar cells have been developed using ultrathin CdS films having a thickness of 50 nm. CdS films deposited on indium tin oxide (ITO)/#1737 glass substrates by the metal organic chemical vapor deposition technique, and CdTe films subsequently deposited by the close-spaced sublimation technique were used for the fabrication of CdS/CdTe solar cells. A photovoltaic conversion efficiency of 16.0% under Air Mass (AM) 1.5 conditions has been measured by the Japan Quality Assurance Organization.

Low-distortion 1.3 /spl mu/m DFB lasers operating from -40 to 85/spl deg/C without any coolers are demonstrated. Extremely low threshold current of 17 mA at 85/spl deg/C is obtained. The lasers also realise low distortion

Leakage current in p-substrate 1.3 μm InGaAsP/InP Buried Crescent (PBC) lasers has been examinedcompared with n-substrate Buried Crescent (BC) lasers. It has been found that the value of the leakage currentcan be estimated by dV/dI-I (differential resistance vs. current) curve above threshold. The leakage current intypical PBC laser is about one order of magnitude smaller than that in BC laser, in which the leakage currentbecomes a few 10 mA at high temperature (70-80°C) and degrades remarkably the P-I (light output power vs.current) characteristics. In order to achieve excellent characteristics at high temperature and high power levels, it is important to minimize the current flowing into p-blocking layer adjacent to the active region.

High performance of newly developed InGaAsP P-substrate buried crescent (PBC) laser diodes is described. It is shown that the PBC laser has superior characteristics to the conventional buried crescent (BC) laser with n-InP substrate. The maximum output power of 140 mW under a CW condition is realized at room temperature. CW light output power of 10 mW up to 110°C is achieved. A maximum CW temperature of 135°C is obtained. Stable CW operations have been confirmed in 70°C 5-mW and 70°C 20-mW aging tests. The reason for the high performance is discussed in relation to the leakage current which flows through the current blocking layers.

An experimental investigation of the flow around smooth circular cylinders in the Reynolds number range 0.8 × 105

Laser diodes with the p-substrate buried-crescent structure have been fabricated for the 1.2-1.55- mu m wavelength region. The dependence of laser characteristics on wavelength has been measured. Up to 70 degrees C, the increasing rates of the threshold current with temperature are similar, while, above 70 degrees C, a shorter-wavelength laser shows a larger increasing rate. At the same full width at half maximum of the far-field pattern perpendicular to the junction plane, the external differential quantum efficiency of the 1.55- mu m laser diode is only 10% smaller than that of the 1.3- mu m laser. The absorption loss coefficients in the active layer of the 1.2-, 1.3-, and 1.55- mu m laser are estimated to be 26, 34, and 73 cm/sup -1/, respectively. >

Stable high-power CW operation of 1.3-μm InGaAsP/InP p-substrate buried crescent laser diodes (PBC-LD'S) has been realized, by controlling the front and rear facet reflectivities of the laser diode chips. The front facet reflectivity is reduced to 17 percent and the rear facet reflectivity is increased to 90 percent, by evaporating multilayer dielectric films (Si/Al 2 O 3 SiO 2 :17 percent, SiO 2 /Si/SiO 2 /Si/SiO 2 :90 percent) on each facet. CW light output power of 50 mW is achieved up to 60°C. Aging tests have been carried out under automatic power control (APC) mode conditions of 50°C-30 mW, 40 mW, 50 mW, and 30°C-50 mW. All samples are operating stably in spite of junction-up configuration. The lifetimes are estimated to be more than 2 \times 10^{4} h for all conditions.

An InGaAsP/InP laser diode emitting at 1.3 μm with a crescent shaped active region is described. The active region is completely embedded in InP by a two-step LPE technique, and a double current confinement scheme is incorporated with two reverse biased p-n junctions at both sides of the active layer. A threshold current as low as 20 mA has been achieved in CW operation at room temperature. Fundamental transverse mode operation with linear light output-current characteristics and single longitudinal mode oscillation have been obtained.

We have found a degradation of the buried crescent (BC) InGaAsP/InP lasers that occurs when the p‐n junction plane coincides with the surface exposed in the high‐temperature H2 ambient before the melt contact during the liquid phase epitaxial growth. To eliminate the degradation, we have fabricated a new structure of the BC laser and have obtained stable cw operation at 80 °C.

As light sources for optical communication systems, diode lasers must exhibit low threshold current and stable fundamental transverse mode operation. An InGaAsP/InP buried crescent (BC) laser is one of the most promising lasers satisfying these requirements.1 In the earlier BC laser, however, some devices exhibited higher-order transverse modes at high pump levels. The structure has now been improved by reducing the width and thickness of the active region to stabilize the transverse mode and to reduce the threshold current.

An experimental investigation of the flow around a smooth circular cylinder at the beginning of the critical transition, where the drag coefficient starts to decrease, was carried out. The measurements disclosed the presence of spanwise structures occurring symmetrically on both sides of the cylinder, associated with large amplitude, low frequency flow components. Mean pressure maps and spanwise cross correlations of pressures and velocities are presented.

A high output power of 85 mW in cw conditions and 460 mW in pulse conditions has been obtained in a 1.3-μm InGaAsP p-substrate buried crescent (PBC) laser diode in spite of junction-up mounting. The lasers have been operating stably for 350 h in a preliminary aging test at 70°C with a 20-mW constant light output.

The temperature dependence of the internal loss α of the InGaAsP/InP buried crescent laser is presented in the temperature range 20–80 °C. α is about 18 cm−1, and no apparent temperature dependence of α is observed in this temperature range. This indicates that the temperature‐sensitive behavior of the threshold current in InGaAsP/InP long‐wavelength lasers is not due to the temperature dependence of internal loss. The decrease in the external quantum efficiency with increasing temperature is attributed to the decrease in the internal quantum efficiency.

A leakage current flowing through a junction between a p-InP current blocking layer and an n-InP cladding layer is examined in connection with a degradation of a buried crescent laser diode at a high temperature. The degradation characteristics have been successfully explained by a theoretical model proposed in this study.

The temperature dependence of the internal loss α of the InGaAsP/InP buired crescent (λ=1.3 µm) laser is presented in the temperature range 20∼80°C. α is about 18 cm-1 and no apparent temperature dependence of α is observed in this temperature range. This indicates that the temperature-sensitive behavior of the threshold current in 1.3 µm laser is not due to the internal loss. The decrease in the external quantum efficiency with increasing temperature is attributed to the decrease in the internal quantum efficiency, which is possibly caused by some leakage current.

The threshold current and beamwidth of the fundamental transverse mode have been examined of the buried crescent (BC) laser. The active region with less than 2.0 µm wide was successfully grown inside the channel prepared on the InP substate and the minimum threshold current of 8 mA has been obtained at room temperature (cavity length L=300 µm). An analytical expression for the beamwidth of far field patterns parallel to the junction plane (θ//) has been obtained and it was confirmed that a good agreement is shown between the theoreitcal calculation and the experimental result.

It is found that electroluminescent mode aging at high-temperature and high-current levels is useful for selecting long-lived InGaAsP 1.3 μm lasers. Lasers selected by this screening have little change in threshold current or forward voltage through the aging test at an elevated temperature with constant light-output power.

Theoretical and experimental investigations on real time transmission of a 3-D image using volume scanning and spatial modulation are described. By using a phase stabilized spatial modulation, a 3-D image is transmitted in real time at the rate of fifteen 3-D images per second. The signal and noise, the effect of continuous illumination, and the conditions for distortion-free imaging are shown with experimental verifications. The present system can be realized with presently available optical and electronic components.

A 1.3 μm InGaAsP/InP buried crescent laser diode has been fabricated on p-InP substrate. The laser diode has a low threshold current, as low as 10 mA. It operates at the output power of 5 mW under CW condition at temperatures higher nary aging test at 70°C with a constant light output of 5 mW, the lasers have been operating stably for more than 1000 h.