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Showing papers on "Energy conversion efficiency published in 1996"


Journal ArticleDOI
Ray H. Baughman1
TL;DR: In this paper, the application of conducting polymers for the direct conversion of electrical energy to mechanical energy in electromechanical actuators is analyzed using theoretical and experimental results, and basic principles of operation, predicted performance advantages and disadvantages, comparisons with natural muscle, evaluations of initial device demonstrations, and methods for improving device performance are provided.

861 citations


Journal ArticleDOI
TL;DR: In this article, double layer anti-reflection (DLAR) was used to improve the energy conversion efficiency of silicon solar cells under monochromatic light, achieving 46.3% for 1.04 μm wavelength light.

240 citations


Journal ArticleDOI
TL;DR: In this paper, a periodically domain reversed AlGaAs waveguide was used for difference-frequency generation in a fabricated buried heterowaveguide, achieving a 90 nm conversion bandwidth, polarization diversified operation, and polarization independent conversion efficiency.
Abstract: Wavelength conversion by difference‐frequency generation is achieved in a periodically domain reversed AlGaAs waveguide. The AlGaAs waveguide is epitaxially grown on a template substrate where a periodic crystal domain inversion is achieved using wafer bonding, selective etching, and organometallic chemical vapor deposition. Wavelength conversion experiments on a fabricated buried heterowaveguide showed a 90 nm conversion bandwidth, polarization diversified operation, and polarization independent conversion efficiency. The experimental results also showed linearity and spectral inversion, which imply transparency to signal formats including analog and frequency modulation. Simultaneous conversion of multiple input wavelengths with no measurable cross talk is also demonstrated.

203 citations


Journal ArticleDOI
TL;DR: Two-photon pumped green cavity lasing has been observed in a solution of a new dye in N,N-dimethyl formamide (DMF) as mentioned in this paper, and the absorption and the fluorescence spectra of the new dye, along with the spectral and temporal behavior of the two-oton pumped lasing output is presented.

145 citations



Journal ArticleDOI
TL;DR: In this article, the conversion efficiency of spectral emission from laser-irradiated solid targets was investigated for short wavelength source development, and the plasma brightness was quantified using absolutely calibrated detectors for 20 materials and spectra were obtained between 50 and 200 A.
Abstract: The conversion efficiency of spectral emission from laser‐irradiated solid targets was investigated for short wavelength source development. The plasma brightness was quantified using absolutely calibrated detectors for 20 materials and spectra were obtained between 50 and 200 A. Laser parameters such as wavelength, pulse length, intensity, and spot size were systematically varied to establish a comprehensive database for source optimization. Qualitative differences in the underlying dominant emission features as a function of atomic number and laser wavelength were observed that accounted for the relatively high spectral conversion efficiencies produced. In the specific case of Sn, a conversion efficiency greater than 0.8%/eV has been observed in the technologically important region of λ=134.0 A using a laser intensity of 1–2×1011 W/cm2.

123 citations


Journal ArticleDOI
TL;DR: High pulse energies of nanosecond-level fourth- and fifth-harmonic (4omega and 5omega) generation of a Nd:YAG laser have been obtained with a CsLiB(6)O(10) (CLBO) nonlinear crystal.
Abstract: High pulse energies of nanosecond-level fourth- and fifth-harmonic (4omega and 5omega) generation of a Nd:YAG laser have been obtained with a CsLiB(6)O(10) (CLBO) nonlinear crystal. 500 mJ of 4omega output with a conversion efficiency of 50% from the second-harmonic input was generated. 5omega output at 213 nm of as high as 230 mJ was obtained by sum-frequency generation of the 266- and 1064-nm beams, corresponding to a 10.4% conversion efficiency of the initial fundamental input energy. The characteristics of the CLBO crystal that permit this effective frequency conversion are discussed.

114 citations


Journal ArticleDOI
TL;DR: In this article, an efficient, high-dynamic range microwave mixer implemented using an analog fiber-optic link with an overdriven optical modulator to produce the local oscillator requirement has been demonstrated and analyzed.
Abstract: An efficient, high-dynamic range microwave mixer implemented using an analog fiber-optic link with an overdriven optical modulator to produce the local oscillator requirement has been demonstrated and analyzed. This approach is compared with the heterodyned lasers approach to generating the local oscillator requirement and it is shown that increased conversion efficiency and more frequency and phase stable upconverted or downconverted signals are obtainable. Aside from RF link loss, which can be compensated with preamplification, a conversion loss below 5 dB has been demonstrated out to 10 GHz.

112 citations


Journal ArticleDOI
TL;DR: In this article, the effect of electrode separation on the power conversion efficiency of a ferricyanide/ferrocyanide thermogalvanic cell containing platinum electrodes was studied at electrode separations up to 150 cm, using the cold-above-hot electrode configuration.
Abstract: Thermogalvanic cells are electrochemical cells in which thermal energy is converted to electrical energy by maintaining the two (usually identical) electrodes at different temperatures. The effect of electrode separation on the power conversion efficiency of a ferricyanide/ferrocyanide thermogalvanic cell containing platinum electrodes was studied at electrode separations up to 150 cm, using the ``cold-above-hot`` electrode configuration. The open-circuit potential difference is almost independent of electrode separation, but the short-circuit current density falls continuously with increasing electrode separation, while the power conversion efficiency increases asymptotically to a plateau value of ca. 0.04% at a separation near 150 cm. This corresponds to an efficiency of ca. 0.6% relative to that of a Carnot engine operating between the temperatures of 293.1 and 313.1 K used in the present study. A separation of 10 cm provides efficiencies which are ca. 83% of the plateau value and is a convenient separation to use if minimal cell volume is required. The power conversion efficiency of the cell was largely limited by ohmic overpotential. Measured exchange current densities showed that activation overpotential has negligible effect on cell current. Mass transport does not limit the cell current because of the beneficial convection caused by the ``cold-above-hot`` electrode configuration.

97 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed nonlinear optical devices for the near and mid infrared range that use an absorption transparency along with a resonantly enhanced second order susceptibility for efficient frequency conversion or parametric amplification.

96 citations


Journal ArticleDOI
TL;DR: In this paper, an integration of biomass as a basic product for the synthesis of methanol improves the conversion efficiency from solar energy to methanoline, and a lower energy demand for the recovery of CO2 from atmosphere than from combustion fluegases is achieved.

Journal ArticleDOI
TL;DR: In this article, a self-supporting silicon membrane was used to achieve energy conversion efficiency above 20% for a silicon cell of less than 50 μm thickness, with efficiency up to 21.5% independently confirmed for a 47-μm thick device.
Abstract: Although many calculations since the early 1980s have predicted that high performance in thin crystalline silicon cells is feasible, performance levels demonstrated in the past have been quite modest. Using a self-supporting silicon membrane, experimen tal energy conversion efficiency above 20% is described for the first time for a silicon cell of less than 50 μm thickness, with efficiency up to 21.5% independently confirmed for a 47-μm thick device. The cells demonstrate a better ability to tra p light internally within their structure than any previously measured device. They also demonstrate the surface passivation benefits of the recently described parallel multijunction thin-film silicon cell approach.

Journal ArticleDOI
TL;DR: In this article, the authors report measurements of the dark-current and open-circuit voltage of a number of quantum well cells in three different lattice matched material systems, namely, Al0.35Ga0.65As/GaAs, GaInP/GaA, and InP/InGaAs.
Abstract: It is known that quantum well solar cells (QWSCs) can enhance short circuit current and power conversion efficiency in comparison with similar, conventional solar cells made from the quantum well (QW) barrier material alone. In this article we report measurements of the dark‐current and open‐circuit voltage (Voc) of a number of quantum well cells in three different lattice‐matched material systems, namely, Al0.35Ga0.65As/GaAs, GaInP/GaAs, and InP/InGaAs. We also present the results obtained from comparable control cells without wells formed either from the material of the barriers or the well material alone. Our results clearly demonstrate in all three cases that, at fixed voltage, QWSC dark currents are systematically lower than would be expected from control cells with the same effective absorption edge. Measurements of Voc in a white‐light source show that the open‐circuit voltages of the QWSCs are higher than those of control cells formed from the well material. Furthermore, this enhancement is more t...

Journal ArticleDOI
TL;DR: In this article, a theoretically ideal motion profile for point-to-point control under acceleration was derived by adopting Pontryagin's minimum principle, and the performance of this energy efficient motion profile was compared to those of three conventional profiles widely used in practice: trapezoidal, variable-rate transymmetric, and exponential.

Journal ArticleDOI
TL;DR: In this paper, a monocrystalline ZnO/CdS/CuGaSe2 heterojunction was fabricated for photovoltaic applications, which achieved a maximum cell efficiency of 9.7% at room temperature under 100 mW/cm2 AM1.5 illumination, given by an open-circuit voltage of 946 mV, a short circuit current density of 15.5 mA/cm 2, and a fill factor of 66.5%.
Abstract: Heterojunctions, such as ZnO/CdS/CuGaSe2, were fabricated for photovoltaic applications. Optimization of device structures based on monocrystalline CuGaSe2 led to the highest-to-date power conversion efficiencies for CuGaSe2 solar cells. At room temperature under 100 mW/cm2 AM1.5 illumination a maximum cell efficiency of 9.7% was achieved, given by an open-circuit voltage of 946 mV, a short circuit current density of 15.5 mA/cm2, and a fill factor of 66.5%. Preparation and performance of the optimum device are described. Current voltage characteristics dependent on illumination intensity and temperature, spectral response and electron-beam-induced current measurements were performed to determine the device parameters as well as to analyse the current transport and loss mechanisms. Tunneling, assisted by defect levels in the CdS layer, seems to play a major role. High injection effects are observed at forward bias ofV > 0.5 V or an illumination level ofP > 10 mW/cm2. Under such conditions, as well as at low temperatures, the non-zero series resistance comes into play. Effects of the shunt resistance, however, are negligible in all cases.

Journal ArticleDOI
TL;DR: In this article, a photovoltaic cell with carbonaceous thin film/n-type silicon (C/n−Si) was fabricated, which was deposited on an n-type single-crystal-silicon substrate by chemical-vapor deposition of 2,5dimethylp-benzoquinone at 500°C.
Abstract: A photovoltaic cell with carbonaceous thin film/n‐type silicon (C/n‐Si) was fabricated. The carbonaceous thin film was deposited on an n‐type single‐crystal‐silicon substrate by chemical‐vapor deposition of 2,5‐dimethyl‐p‐benzoquinone at 500 °C. Without light irradiation, the photovoltaic cell displayed an almost perfect rectifying current–voltage characteristic. Under illumination of 15 mW cm−2 light with wavelengths between 400 and 800 nm similar to the solar light, it generated 2.73 mA cm−2 of short‐circuit and 325 mV of open‐circuit voltage. With the same light condition, a power conversion efficiency of 3.80% and a fill factor value of 0.65 were achieved.

Journal ArticleDOI
TL;DR: In this article, the authors present an experimental study of harmonic generation in molecular gases, using the fundamental (800 nm) and the second harmonic (400 nm) of a 150 fs titanium - sapphire laser at an intensity of.
Abstract: We present an experimental study of harmonic generation in molecular gases, using the fundamental (800 nm) and the second harmonic (400 nm) of a 150 fs titanium - sapphire laser at an intensity of . We compare the conversion efficiency and the maximum energy obtained in different species: rare gases (Ar, Xe), diatomic molecules (, , , CO) and polyatomic molecules (, O, , , ). The harmonic spectra from molecular gases are very similar to those obtained in the atomic gases, with a plateau and a cutoff whose location is strongly correlated to the value of the ionization potential. The conversion efficiency is not higher than that of the rare gases.

Journal ArticleDOI
TL;DR: First-order quasi-phase-matched frequency doubling of picosecond pulses to the green, using a sample of periodically poled lithium niobate, with significant photorefractive damage is reported.
Abstract: We report on first-order quasi-phase-matched frequency doubling of picosecond pulses to the green, using a sample of periodically poled lithium niobate. In cw mode-locked operation. 330 mW of average green power was generated with an average conversion efficiency of ~52%. With a quasi-cw mode-locked pulse train an average conversion efficiency of ~65% was achieved, and 1.3 W of green power (average power within the 10-ps pulse envelope) was produced. At these powers there was no significant photorefractive damage, as confirmed by measured M 2 beam-quality factors of ~1.1 for both output fundamental and second-harmonic beams.

Journal ArticleDOI
TL;DR: A compact and efficient source of cw single-frequency radiation at 532 nm with excellent long-term stability has been realized by external frequency doubling of a diode-pumped miniature Nd:YAG ring laser.
Abstract: A compact and efficient source of cw single-frequency radiation at 532 nm with excellent long-term stability has been realized by external frequency doubling of a diode-pumped miniature Nd:YAG ring laser. With a semimonolithic MgO:LiNbO3 resonator an optical-to-optical conversion efficiency of 89% from 1064 to 532 nm at an output power of 1.1 W was achieved, with a wall plug efficiency of 9%. This system represents an ideal pump source for narrow-linewidth cw optical parametric oscillators with good frequency stability.

Journal ArticleDOI
TL;DR: In this article, two types of p-n heterojunction devices consisting of thin films of titanyl phthalocyanine (TiOPc) and N,N′-dimethyl-3,4:9,10-peryle-nebis(dicarboximide) (MPCI), sandwiched between indium tin oxide (ITO) and gold (Au), have been fabricated, and their performance characteristics investigated.

Journal ArticleDOI
TL;DR: In this paper, the effects of the phase mismatch due to cubic nonlinearity in the equations for second-harmonic generation are investigated, and it is shown that phase mismatch induced by the nonlinear refractive index of a doubling crystal can dramatically reduce the conversion efficiency of high-peak-power laser pulses.
Abstract: The effects of the phase mismatch due to cubic nonlinearity in the equations for second-harmonic generation are investigated. We show that the phase mismatch induced by the nonlinear refractive index of a doubling crystal can dramatically reduce the conversion efficiency of high-peak-power laser pulses. Simple, analytic expressions are derived for the conversion efficiency of cw radiation and for the estimation of the dispersion in the nonlinear refractive index of the doubling crystal, which is quite important in the determination of the magnitude of the nonlinear effects on maximum conversion. The consequences that these nonlinearities have on the frequency doubling of ultrashort (≤100 fs) pulses, including the additional effects of group-velocity walk-off between the pulses, are then numerically calculated.

Journal ArticleDOI
TL;DR: In this article, the dependence of conversion efficiency on thickness and incident wavelength is extensively investigated for evaporated coatings of p-terphenyl and tetraphenyl butadiene.
Abstract: The need for, and benefits of using, wavelength shifters with certain dark matter scintillator detectors is discussed. The dependence of conversion efficiency on thickness and incident wavelength is extensively investigated for evaporated coatings of p-terphenyl and tetraphenyl butadiene, and for plastic waveshifters based upon p-terphenyl. For the latter the effect of varying the p-terphenyl concentration is studied and some factors which must be considered when developing them for use in the UV are also discussed.

Journal ArticleDOI
TL;DR: The photocurrent quantum yield of a porous SiC/electrolyte diode is spectacularly enhanced with respect to that of a flat diode for light absorbed in the indirect bandgap and for sub-bandgap light.
Abstract: Scanning electron microscopy micrographs of n‐type silicon carbide (SiC) anodized in HF solution showed a highly porous layer having structures with dimensions of about 50 nm. The capacitance of the porous electrodes revealed a huge surface area. The photocurrent quantum yield of a porous SiC/electrolyte diode is spectacularly enhanced with respect to that of a flat diode for light absorbed in the indirect‐bandgap and for sub‐bandgap light.

Journal ArticleDOI
TL;DR: In this paper, thin film flexible CuInSe2 (CIS) solar cells have been fabricated for the first time on light-weight polymeric substrates and demonstrated active area conversion efficiency of 9.3%.

Patent
H. Morikawa1, Hisao Kumabe1
02 Feb 1996
TL;DR: In this paper, a photovoltaic thin semiconductor crystalline film is formed on an underlying substrate and hydrogen passivated throughout the film thickness direction of the PV film whereby a high efficiency solar cell is obtained.
Abstract: In a method of producing a solar cell, a photovoltaic thin semiconductor crystalline film is formed on an underlying substrate and hydrogen passivated throughout the film thickness direction of the photovoltaic film whereby a high efficiency solar cell is obtained. In addition, since the passivation process is performed before forming a rear surface electrode on the thin semiconductor crystalline film, the passivation process is not limited by the rear surface electrode. Thereby, a solar cell having a higher energy conversion efficiency is obtained. The passivation process is performed by exposing the thin semiconductor crystalline film to a hydrogen ion ambient having a low acceleration energy, below 2 KeV, or to a plasma ambient. Therefore, the uniformity of the passivation process at a wafer surface is improved and a large area wafer can be efficient processed. Furthermore, the passivation process can be performed to a plurality of solar cells having the thin semiconductor crystalline films and arranged in a module.

Journal ArticleDOI
TL;DR: In this paper, the authors measured a signal gain of 5 dB and idler conversion efficiency of 4 dB in a CW fibre optical parametric amplifier with pump dithering used to suppress SBS.
Abstract: The authors have measured a signal gain of 5 dB and idler conversion efficiency of 4 dB in a CW fibre optical parametric amplifier. The broadening of the idler spectrum resulting from pump dithering used to suppress SBS is observed, and a means to eliminate it is proposed.

01 Jan 1996
TL;DR: In this article, the efficiency and optimization of cw second harmonic generation by elliptical Gaussian laser beams were studied, and single pass measurements of the efficiency for doubling 5 15nm radiation in beta-barium borate (BBO) agree with theory.
Abstract: We present a study of the efficiency and optimization of cw second harmonic generation by elliptical Gaussian laser beams. Elliptical focusing slightly improves conversion efficiency and reduces crystal damage risk when heavy walk-off is present. Single-pass measurements of the efficiency for doubling 5 15-nm radiation in beta-barium borate (BBO) agree with theory. Thermal effects, caused by radiation absorption, limit the doubling efficiency of single-frequency radiation in an extemal enhancement ring cavity.

Journal ArticleDOI
TL;DR: In this article, the efficiency and optimization of cw second harmonic generation by elliptical Gaussian laser beams were studied, and single pass measurements of the efficiency for doubling 515-nm radiation in beta-barium borate (BBO) agree with theory.

Journal ArticleDOI
TL;DR: In this article, a photoelectrochemical cell based on neutral poly(3-methylthiophene) electrochemically coated on indium-tin oxide as a photoactive electrode, an amorphous poly(ethylene oxide) complexed with an I3−/I− redox couple as a solid polymer electrolyte, and thin transparent platinum film vapour deposited on the indium surface as a counter electrode has been constructed.

Journal ArticleDOI
TL;DR: In this paper, the effect of nonlinear loss on four-wave mixing (FWM) conversion efficiency was analyzed and it was shown that the maximum FWM conversion efficiency is geometry independent and is equal to e−2|χ(3)/Im{χ (3)}|2 when non-linear loss dominates.
Abstract: We analyze the effect of nonlinear loss on four‐wave mixing (FWM) conversion efficiency. Maximum conversion efficiency is geometry independent and equal to e−2|χ(3)/Im{χ(3)}|2 when nonlinear loss dominates. Optimum device length and operating conditions are obtained and theoretical results are verified with a picosecond pulse FWM experiment.