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Enhancement of photovoltaic performance due to alkali-metal doping in various thin-film compound solar cells such as chalcogenide Cu(In,Ga)Se2 (CIGS), Cu2ZnSnS4 (CZTS), and organic–inorganic hybrid perovskite, is significant in the development of photovoltaic technologies. In this work, the effects of light Li- and heavy Cs-doping in ternary CuGaSe2 (CGS) and quaternary CIGS thin-films and devices are compared. The new findings are: (i) heavy alkali-metal halide CsF postdeposition treatment (PDT) modifies the CGS film surface morphology and increases the carrier density; however, the beneficial effects of Cs on the CGS photovoltaic performance are low when compared to the results observed from quaternary CIGS devices; (ii) LiF-PDT leads to no significant CGS and CIGS film surface (hetero p-n junction interface) modifications; thus, the use of a thin (approximately 30 nm) CdS buffer layer is not effective in enhancing photovoltaic performance; and (iii) the beneficial effects of either light Li or heavy Cs on ternary CGS devices are modest; nonetheless, Li may be more effective than Cs, unlike quaternary CIGS devices.

We found that elemental Si-doped Cu(In,Ga)Se2 (CIGS) polycrystalline thin films exhibit a distinctive morphology due to the formation of grain boundary layers several tens of nanometers thick. The use of Si-doped CIGS films as the photoabsorber layer in simplified structure buffer-free solar cell devices is found to be effective in enhancing energy conversion efficiency. The grain boundary layers formed in Si-doped CIGS films are expected to play an important role in passivating CIGS grain interfaces and improving carrier transport. The simplified structure solar cells, which nominally consist of only a CIGS photoabsorber layer and a front transparent and a back metal electrode layer, demonstrate practical application level solar cell efficiencies exceeding 15%. To date, the cell efficiencies demonstrated from this type of device have remained relatively low, with values of about 10%. Also, Si-doped CIGS solar cell devices exhibit similar properties to those of CIGS devices fabricated with post deposition...

This study aimed to reveal the electrical characteristics of the composite electrodes of Li-ion batteries. LiCoO2 electrodes were analyzed using atomic force microscopy, and three-dimensional datasets of current–voltage (I–V) curves (IV-datacubes) were obtained. The IV-datacubes were then analyzed using principal component analysis to determine the typical I–V curve corresponding to each LiCoO2 particle on a statistical basis. Detailed analysis based on the thermionic emission model with series resistance showed that some of the particles exhibited poor electrical contact in the electrode. Overall, the obtained results suggested that our IV-datacube analysis can reveal the characteristics of buried electrical contacts within electrodes, which is otherwise difficult to accomplish using alternative methods. We, therefore, believe that the method presented herein is a promising analytical method for composite electrodes.

Scanning transmission electron microscopy-energy dispersive X-ray spectroscopy measurements performed on Cu(In,Ga)Se2 (CIGS) thin-film devices grown with RbF postdeposition treatment (RbF-PDT) revealed the formation of a RbInSe2 compound at the p-CIGS/n-CdS heterointerface. However, this type of Rb-compound formation was not observed with elemental In-free ternary CuGaSe2 (CGS) devices. The film surface of CIGS grown with RbF-PDT was found to be Ga-depleted; thus, the practical interface structure turned out to be CIGS/(CuInSe2, RbInSe2)/CdS. In contrast to the significant improvements observed in In-containing CIGS photovoltaic device performance with RbF-PDT, no significant improvements have been observed in In-free CGS devices thus far. These results suggest that the presence of elemental In plays a key role in obtaining beneficial alkali Rb effects for enhancing device performance as well as surface modification with RbF-PDT.Scanning transmission electron microscopy-energy dispersive X-ray spectroscopy measurements performed on Cu(In,Ga)Se2 (CIGS) thin-film devices grown with RbF postdeposition treatment (RbF-PDT) revealed the formation of a RbInSe2 compound at the p-CIGS/n-CdS heterointerface. However, this type of Rb-compound formation was not observed with elemental In-free ternary CuGaSe2 (CGS) devices. The film surface of CIGS grown with RbF-PDT was found to be Ga-depleted; thus, the practical interface structure turned out to be CIGS/(CuInSe2, RbInSe2)/CdS. In contrast to the significant improvements observed in In-containing CIGS photovoltaic device performance with RbF-PDT, no significant improvements have been observed in In-free CGS devices thus far. These results suggest that the presence of elemental In plays a key role in obtaining beneficial alkali Rb effects for enhancing device performance as well as surface modification with RbF-PDT.

A predistortion-type equi-path linearizer is created for a radio-on-fiber system based on wide-band code division multiple access; its main benefit is its simple optical circuit configuration. Experiments show that the phase difference between the carrier and third-order intermodulation (IM3) component of the laser diodes (LDs) is shifted by around 90/spl deg/ from that of the RF amplifier. To our knowledge, this is the first report to describe this phase shift, which is observed with both Fabry-Perot and distributed-feedback LDs. To counter this shift, we use additional phase shifters. The proposed design places a pre-amplifier between the linearizer and LD for lower power consumption and better insertion gain at the linearizer. Experimental and calculated results agree well, and more than 20-dB improvement in the IM3 components is obtained over the bandwidth of 60 MHz. The linearizer works well in the temperature range of 10/spl deg/C to 40/spl deg/C with a simple control circuit.

This paper describes a newly developed the system to detect spilled chemical substances. We had developed the prototype of fluorescence Lidar since 2001. The Lidar system was able to detect fluorescence of substances excited by the third harmonic generator of the YAG laser using CCD camera with gated image intensifier. The laser beam included 355 (third harmonic), 532 (second harmonic) and 1, 064nm (normal wavelength) light. An ICCD camera recorded images of the oil fluorescence that was excited by 355nm light. Both the sea depth and the observing altitude were measured by the reflectance signal of 532 and 1, 064nm beam. Detection system was composed of there detectors.We developed a new detection system to measure fluorescence of chemical substance with a high accurately, and confirmed the performance from 2002 to 2003. The system was composed of 4 lenses and an ICCD camera. Through lens mounted a different band-pass filter, four kinds of wavelength images were obtained at the same time as one image. The performance was confirmed by the field experiment and shipboard experiment.

物質の大量流通において海上輸送は大きな役割を果たしている. 残念なことに事故により海洋へ化学物質, 原油や重油などオイル類の流出が度々起こる. そのため流出状況の巨視的状態把握のために紫外線励起蛍光検出リモートセンシング装置の開発を行った. また, 回収処理後に残留物があり, 含有量の変化や生物への影響などについて未知な部分が多く, そこで蛍光分光法を利用した微視的なスクリーニング検出手法の開発を行った. 両者とも環境計測を目的としているために広域にモニタリングのためのプラットホームが必要である. 本研究ではオイル分析に絞り, 巨視的検出では航空機搭載実験を行った. 日本海上空で浮遊しているオイルの可視画像を取得し, また太陽光励起ではあるが同じ場所の波長選択フィルター像を得た. また微視的分析は蛍光分光法のオイル検出試験より得られた船舶搭載についての結果を報告する.

We examined the depressant effect of midazolam on respiration in 21 healthy women undergoing lower abdominal surgery with spinal anaesthesia. Airway gas flow, airway pressure, and the sound of snoring were recorded together with arterial oxygen saturation (SpO2). After spinal anaesthesia was established, subjects were deeply sedated with pentazocine 15 mg followed by incremental doses of midazolam 1 mg i.v. up to 0.1 mg.kg-1. When SpO2 decreased to < 90% or snoring and/or apnoea was observed, continuous positive airway pressure applied through the nose (nasal CPAP) was increased until the respiratory deterioration was reversed. While one patient remained free of respiratory events, the other 20 patients were successfully treated with nasal CPAP restoring normal SpO2 (95.5 +/- 1.7%) without snoring. Stepwise reduction of nasal CPAP determined the minimally effective CPAP to prevent snoring to be 5.1 +/- 2.1 cm H2O. Further reduction of nasal CPAP induced snoring in 15 patients and obstructive apnoea in five patients with the latter accompanied by a severe reduction of SpO2 (87.4 +/- 6.1%). Patients with apnoea were older than those who snored (P < 0.05. We conclude that upper airway obstruction contributes considerably to decreases in SpO2 during midazolam sedation for spinal anaesthesia.

Recent interest in biomedical imagings using lasers has been spurred by the need of nonionizing medical imaging diagnostics. Tunable solid-state lasers are well suited for spectroscopic measurements and imaging of biological tissues, which are expected to provide functional information of the samples. This paper summarizes our recent development of a laser-diode pumped, single-frequency CW Cr: LiSAF laser which has been demonstrated to be tunable over a wide range of 150 nm near the wavelength of 875 nm. By reviewing our recent progresss of optical imaging and computed tomography of tissues and tissue-like phantoms, we show some of the potential applications of the tunable solid-state lasers.

We report on a widely tunable, diode-pumped, continuous-wave, single-frequency Cr(3+):LiSrAlF(6) laser with a novel double-ring cavity configuration. The optical diode and the tuning element were located in the ring subcavity to decrease their insertion loss. Using an 1800-lines/mm grating as the tuning element, we obtained a laser emission of 20-mW output power at 870 nm and a tuning range of from 800 to 936 nm. When we used a 1200-lines/mm grating with a higher diffraction efficiency, the laser had a slightly wider tuning range of from 800 to 938 nm. However, the output power decreased at this tuning range.

This letter reports exceptionally broadband tuning of a continuous-wave optical parametric oscillator (cw OPO) using a temperature tuned, nonlinear crystal of MgO:LiNbO3 pumped by a diode-pumped, intracavity doubled Nd:YAG laser. The tuning range from 788 to 1640 nm, is about four times broader than those ever reported in cw OPOs operating around 1 μm. This performance was accomplished by newly developed, extremely broadband, high-reflection mirrors for the doubly resonant oscillation, designed to have a reflectivity of 99% from 0.7 to 1.6 μm. Threshold pump power increased from 80 mW near degeneracy to 150 mW at the tuning band edge in a double pass pumping configuration.

A frequency-converted radio-on-fiber (ROF) system that reduces the relative-intensity-noise (RIN) caused by reflection at optical fiber connectors is proposed. It is based on the simultaneous transmission of intermediate frequency (IF) and local-oscillation (LO) frequency. Optimum LO frequency and optical modulation index (OMI) that minimize RIN are investigated by experiments and calculations assuming the multi-reflection situation with random delays. The results agree well and show that RIN suppression is best achieved with high OMI and low LO frequency. RIN improvement of 10dB is obtained by this technique. The maximum number of connectors is also investigated. One calculation suggests that the proposed system can support 79 connectors, many more than the 13 possible with existing systems.

A predistortion type equi-path linearizer is created for a radio-on-fiber system based on W-CDMA; its main benefit is its simple optical circuit configuration. Experiments show that the phase of the third order intermodulation components of the laser diode is delayed by around 90 degrees from those of RF amplifier. To our knowledge, this is the first report to describe the phase delay. To counter this delay we place an additional phase shifters. The proposed design places a pre-amplifier between the linearizer and a laser diode for lower power consumption and better insertion gain at the linearizer. The experimental and calculated results agree well, and an over 20dB improvement in third order intermodulation components is obtained for the bandwidth of 60MHz. The linearizer works well in the temperature range of 10°C to 40°C with a simple control circuit.

We present a new stability mechanism in an intracavity-doubled Nd:YAG laser oscillating in a multi-fundamental-longitudinal mode. Self-mode-locked oscillation, in which phases of the modes give the destructive interference between the sum and doubling components, leads to the low-noise operation of the diode-pumped, >6-W cw green laser, which we previously demonstrated [Opt. Lett. 211912 (1996)]. This phase-locked mode of operation would reduce the nonlinear output coupling and ultimately eliminate the chaotic amplitude fluctuation from the so-called green problem. The internally reflected green light at the end mirror has a significant effect on phase locking and elimination of noise through parametric processes.

>6W green TEM00, low-noise output at 32% efficiency was obtained from a diode-pumped, intracavity-doubled Nd:YAG laser. Ti:sapphire laser pumped by the green laser produced 1.4W cw single-frequency output.

Treatment of dyspnea in patients with advanced cancer is an important issue. The purpose of the present study was to assess the effect of induced-metabolic alkalosis produced by administration of sodium bicarbonate on dyspneic sensation. In seven healthy subjects, dyspnea was induced by having them breathe with a flow-resistive load (24 cm H2O/L/sec) for 6 min before and after administration of sodium bicarbonate (0.5 mmol/kg, per os + 2 mmol/kg, IV). The intensity of dyspnea was rated using a visual analogue scale (VAS). The VAS scores and minute ventilation during loaded breathing after administration of sodium bicarbonate were significantly lower than those before administration of sodium bicarbonate. These results indicate that induced metabolic alkalosis may alleviate the intensity of dyspneic sensation by a reduction in ventilatory drive.

We present comparative studies of the laser performance of a diode-end-pumped, composite Tm:YAG rod with undoped ends. Efficient heat removal in a composite rod can reduce the peak of the rise in temperature in the 2-mm-long active segment by 19% compared with that in a noncomposite rod by theoretical calculation. The threshold pump power was reduced by 10%, and the focal power of the thermal lens was improved by 15%. These improvements permit high output performance and flexible design of laser cavities in diode-end-pumped Tm:YAG lasers.

We present comparative studies on laser performance of diode end-pumped, composite Nd:YAG rods with undoped ends at 946 nm. Efficient heat removal in a composite rod can reduce the peak of rise in temperature in the active segment to 61% by theoretical calculation. The maximum, continuous-wave output power of 1.5 W, which is three times higher than a conventional noncomposite rod, was obtained at an absorbed pump power of 8 W because of the 55 deg reduction in temperature rise that was estimated experimentally. The performance and characteristics of composite rods in quasi-three-level laser operation are analyzed and discussed in detail, taking into account the reduction in reabsorption loss, which is strongly temperature dependent.

We present what is to our knowledge the first theoretical and experimental estimation of the thermal characteristics of a composite Nd:YAG rod with an Al2O3 (sapphire) end in diode-end-pumped geometry. The peak temperature rise in the active segment is calculated to be reduced to 66% and the focal length of the thermal lens was measured to be reduced by 20% compared with a noncomposite Nd:YAG rod. By using a composite rod we successfully demonstrated the improvement of high-power performance that is due to reduction of thermally induced birefringence, which has not been observed in a composite rod with an undoped YAG end.