We studied heat production in Pd-impregnated alumina powder in the presence of hydrogen and deute... more We studied heat production in Pd-impregnated alumina powder in the presence of hydrogen and deuterium gases, investigating claims of anomalous heat generated as a result of nuclear fusion, usually referred to as a low energy nuclear reaction (LENR). By selecting the water isotope used to fabricate the material and then varying the gas used for loading, we were able to influence the amount of heat released or consumed. We suggest that Pd in its nanoparticle form catalyzes hydrogen/deuterium (H/D) exchange reactions in the material. This hypothesis is supported by heat measurements, residual gas analysis (RGA) data, and calculations of energy available from H/D exchange reactions. Based on the results we conclude that the origin of the anomalous heat generated during deuterium loading of Pd-enriched alumina powder is chemical rather than nuclear.
We evaluate a technique to improve the performance of antenna-coupled diode rectifiers working in... more We evaluate a technique to improve the performance of antenna-coupled diode rectifiers working in the IR. Efficient operation of conventional, lumped-element rectifiers is limited to the low terahertz. By using femtosecond-fast MIM diodes in a traveling-wave (TW) configuration, we obtain a distributed rectifier with improved bandwidth. This design gives higher detection efficiency due to a good match between the antenna impedance and the geometry-controlled impedance of the TW structure. We have developed a method for calculating the responsivity of the antenna-coupled TW detector. Three TW devices, made from different materials, are simulated to obtain their impedance and responsivity at 1.5, 3, 5, and 10 µm wavelengths. The characteristic impedance of a 100-nm-wide TW is in the range of 50 Ω and has a small variation with frequency. A peak responsivity of 0.086 A/W is obtained for the Nb-Nb 2 O 5 -Nb TW diode at 3-µm wavelength. This corresponds to a quantum efficiency of 3.6% and is a significant improvement over the antenna-coupled lumped-element diode rectifiers. For IR imaging, this results in a normalized detectivity of 4 × 10 6 Jones at 3 µm. We have identified several ways for improving the detectivity of the TW detector. Possible methods include decreasing the diode resistance, reducing the noise, and increasing the effective antenna area.
ABSTRACT A recently issued patent [1] describes a method by which vacuum energy is extracted from... more ABSTRACT A recently issued patent [1] describes a method by which vacuum energy is extracted from gas flowing through a Casimir cavity. According to stochastic electrodynamics, the electronic orbitals in atoms are supported by the ambient zero-point (ZP) field. When the gas atoms are pumped into a Casimir cavity, where long-wavelength ZP field modes are excluded, the electrons spin down into lower energy orbitals and release energy in the process. This energy is collected in a local absorber. When the electrons exit the Casimir cavity they are re-energized to their original orbitals by the ambient ZP fields. The process is repeated to produce continuous power. In this way, the device functions like a heat pump for ZP energy, extracting it globally from the electromagnetic quantum vacuum and collecting it in a local absorber. This energy can be used for heating, or converted to electric power.
Numerous reports on gas loading of hydrogen isotope into powdered materials indicate excess heat ... more Numerous reports on gas loading of hydrogen isotope into powdered materials indicate excess heat generation that could be the result of a low energy nuclear reaction (LENR). When the amount of generated heat is small, it is important to characterize the calorimeter to account for possible measurement errors, or artifacts, which can result in long-term apparent excess heat. In this paper we investigate one of those possible measurement artifacts applicable to the gas loading systems that (1) use thermometry as a proxy for energy flow measurements, and (2) run at elevated temperatures. When loading gas into Pd-impregnated alumina, we have found that thermal gradients inside the system result in apparent heating or cooling of the measuring system. We experimentally magnified this effect and confirmed that it was due to temperature nonuniformity inside the calorimetric system. We quantified the effect using a numerical simulation tool to show that a temperature gradient as small as 0.5 K/m might result in 50 mW of apparent excess heat "generation". We suggest a simple approach for investigators to account for this measurement artifact by calibrating their systems with helium gas either prior to, or at the end of, the experimental sequence.
Our group has confirmed excess heat production and isotope effects in alumina and zeolite powders... more Our group has confirmed excess heat production and isotope effects in alumina and zeolite powders containing highly dispersed Pd nanoparticles. Varying the pressures and loading rates produced correlations between the exothermic and endothermic aspects of the experiments. It was shown that the generated power is proportional to the pressurization rate times a quantity , which is the energy content of what we called "fuel". There are two types of fuels, both of which can trigger the reaction that can be either exothermic or endothermic depending on the gas used in the experiment (deuterium or hydrogen). Observed heat generation during the pressurization phase is most likely of a chemical nature.
How wonderful that we have met with^ paradox. Now we have some hope of making progress." -Niels B... more How wonderful that we have met with^ paradox. Now we have some hope of making progress." -Niels Bohr Abstract. Although experimental evidence for retrocausation exists, there are clearly subtleties to the phenomenon. The bilking paradox, in which one intervenes to eliminate a subsequent cause after a preceding effect has occurred, appears on the surface to show that retrocausation is logically impossible. In a previous paper, the second law of thermodynamics was invoked to show that the entropy in each process of a psi interaction (presentence, telepathy, remote perception, and psychokinesis) cannot decrease, prohibiting psi processes in which signals condense from background fluctuations. Here it is shown, perhaps contrary to one's intuition, that reversible processes cannot be influenced through retrocausation, but irreversible processes can. The increase in thermodynamic entropy in irreversible processes -which are generally described by Newtonian mechanics but not Lagrangian dynamics and Hamilton's Principle -is required for causation. Thermodynamically reversible processes cannot be causal and hence also cannot be retrocausal. The role of entropy in psi interactions is extended by using the bilking paradox to consider information transmission in retroactive psychokinesis (PK). PK efficiency, r\ pK , is defined. A prediction of the analysis is that r\ PK ^ HIH Q , where H is the information uncertainty or entropy in the retro-PK agent's knowledge of the event that is to be influenced retrocausally. The information entropy can provide the necessary ingredient for nonreversibility, and hence retrocausation. Noise and bandwidth limitations in the communication to the agent of the outcome of the event increase the maximum PK efficiency. Avoidance of the bilking paradox does not bar a subject from using the premonition of an event to prevent it from occurring. The necessity for large information entropy, which is the expected value of the surprisal, is likely to be essential for any successful PK process, not just retro-PK processes. Hence uncertainty in the communication process appears to be a necessary component of retrocausation in particular, and of PK in general.
We demonstrate the capability of optically addressed spatial light modulators that incorporate su... more We demonstrate the capability of optically addressed spatial light modulators that incorporate surfacestabilized ferroelectric liquid crystals to reproduce gray scale. This capability is based on temporal averaging and is observed in an operating mode in which the applied voltage repeatedly cycles the device between writing and erasing at operating frequencies between 100 and 2000 Hz. A gray scale response is observed for write-light intensities below a saturation level that increases from 100 pW/cm 2 at 100 Hz to 2 mW/cm 2 at 2 kHz. We develop a procedure to determine the modulation transfer function from measurements of the diffraction efficiency as a function of spatial frequency and write-light intensity in a device with a nonlinear transfer characteristic. At an operating frequency of 500 Hz, the modulation transfer function is greater than or equal to 0.50 at a spatial frequency of 40 line pairs/mm.
ABSTRACT The present volumes form the proceedings of the Third International Conference on Ferroe... more ABSTRACT The present volumes form the proceedings of the Third International Conference on Ferroelectric Liquid Crystals, held in Boulder, Colorado, USA 23-28 June 1991. These volumes continue the publication of this conference series, the proceedings of the first conference (1987) held at Bordeaux/Arcachon appearing in Volumes 84 and 85, and the proceedings of the second conference (1989) held at Goteborg appearing in Volumes 113 and 114. As for the two preceding conferences, FLC-91 provided a broad forum for the exchange of information on FLCs, with most of the groups working in the field well represented. Exciting developments were reported in all FLC areas. The worldwide effort at developing new FLC materials continues apace, with the report of an FLC material possessing a spontaneous polarization nearly equal to the sum of all transverse molecular dipoles, and new thrusts in polymer FLCs and FLCs for electronic nonlinear optical applications. The conference saw many new developments in FLC basic and device physics, including the use of dielectric spectroscopy copy as a tool for studying the molecular origins of the polarization in FLCs. Particularly exciting were the FLC device developments with the emergence of sophisticated FLC devices for opto-electronic computing, display, and other light control applications, including a demonstration of a flexible polymer FLC display.
Http Dx Doi Org 10 1080 02678299108033148, Sep 24, 2006
The switching characteristics and the electro-optic response due to the electroclinic effect in c... more The switching characteristics and the electro-optic response due to the electroclinic effect in chiral smectic A liquid crystals are analysed theoretically. We give an exact analytic solution to the dynamic equation of the tilt angle (8) up to the O4 term in the Landau expansion of the free energy. The non-linear behaviour of B and the characteristic. time under an applied electric field are described near the S2-S; transition. They both have a finite value at the transition which depends on the field. The characteristic time (to) exhibits a critical slowing down at sufficiently low fields, which occurs only in the early stages of the switching. At late stages, the switching time exhibits a maximum at a particular temperature which depends on the field, and then decreases in a very narrow temperature range near the transition. The U4 term is important in explainingcertain properties even for very small 6, and it becomes essential for B > 5". The optical response of an electroclinic liquid crystal cell is considered in detail. We derive an expression for the output intensity of light passing through an electroclinic cell. The delay and rise times for the optical signal are shown to a first approximation to be 0.379 to and 2.577 to, respectively.
We present a model of size-dependent luminescence from a-Si:H and show that a blueshift of the lu... more We present a model of size-dependent luminescence from a-Si:H and show that a blueshift of the luminescence energy and a general increase in luminescence quantum efficiency are predicted as structure size decreases. In contrast to bulk a-Si:H structures, highly confined a-Si:H exhibits visible luminescence peak energies and high radiative quantum efficiency at room temperature, which is insensitive to changes in temperature or defect density. We also predict a decrease in mobility and radiative decay time as structure size shrinks. We compare our results with observations of visible light emission from porous silicon.
Biological thin films may form on a surface by specific molecular interactions. The fixed polariz... more Biological thin films may form on a surface by specific molecular interactions. The fixed polarizer ellipsometer (FPE) is a sensitive instrument that detects biological thin films either qualitatively or quantitatively. The design is simple and inexpensive. The assays are formatted on an optical surface, and the FPE detection is based on the phase shift of linearly polarized light after reflection through a thin film. We have constructed mathematical models of the FPE response to reflection through single-layer and two-layer films that agree closely with experimental data. Several biological assays have been measured with the FPE to demonstrate the application of this technology to clinical targets, including ultrasensitive immunoassays for hepatitis B surface antigen (0.1 ng/mL) and ␣-fetoprotein (0.01 ng/ mL) and DNA hybridization (0.5 fmol/L target probe).
We demonstrate the application of an asynchronous image-subtraction optically addressed spatial l... more We demonstrate the application of an asynchronous image-subtraction optically addressed spatial light modulator to particle image velocimetry fringe processing. The device comprises an amorphous silicon p-i-n-i-p photosensor and a ferroelelectric liquid-crystal light-modulating layer. The images to be subtracted are encoded on two separate wavelengths. The operation of the device is described, and characterization shows a frame rate of 100 Hz, a resolution of 3 line pairs/mm, and a write-light sensitivity of approximately equals 1 mW/cm2 at a wavelength of 514 nm. The device is read by the use of light with a 633-nm wavelength whereas the subtraction light is at a wavelength of 670 nm. Using this device to subtract a nonuniform pedestal from the optically computed power spectral density function (the Young's fringe
We report photoemission results from which we directly determined the density of states g(E) in t... more We report photoemission results from which we directly determined the density of states g(E) in the gap of a-Si:H between the top of the valence band E v and the Fermi level. At 0.4 eV above E v, g(E) was found to be ≈1×10 20 cm -3 eV -1 in the undoped film; P-doping increased g(E) in this region whereas annealing reduced it. The photoconductivity-derived optical absorption spectrum matched the shape of the photoemission spectrum, and thus supports the explanation that the photoconductivity shoulder at photon energies in the region of 1.3 eV is due to transitions from localized states above the valence band to the conduction band.
Conference Held in Boulder Co 23 28 Jun 1991, 1992
The present volumes form the proceedings of the Third International Conference on Ferroelectric L... more The present volumes form the proceedings of the Third International Conference on Ferroelectric Liquid Crystals, held in Boulder, Colorado, USA 23-28 June 1991. These volumes continue the publication of this conference series, the proceedings of the first conference (1987) held at Bordeaux/Arcachon appearing in Volumes 84 and 85, and the proceedings of the second conference (1989) held at Goteborg appearing in Volumes 113 and 114. As for the two preceding conferences, FLC-91 provided a broad forum for the exchange of information on FLCs, with most of the groups working in the field well represented. Exciting developments were reported in all FLC areas. The worldwide effort at developing new FLC materials continues apace, with the report of an FLC material possessing a spontaneous polarization nearly equal to the sum of all transverse molecular dipoles, and new thrusts in polymer FLCs and FLCs for electronic nonlinear optical applications. The conference saw many new developments in FLC basic and device physics, including the use of dielectric spectroscopy as a tool for studying the molecular origins of the polarization in FLCs. Particularly exciting were the FLC device developments with the emergence of sophisticated FLC devices for opto-electronic computing, display, and other light control applications including a demonstration of a flexible polymer FLC display.
We outline a procedure to extract the optical-absorption coefficient as a function of energy from... more We outline a procedure to extract the optical-absorption coefficient as a function of energy from measurements of photoconductivity and assess the assumptions involved in applying it to a-Si: H. Using this procedure, we obtain accurate absorption spectra in the range from 1.8 to below 1.2 eV. These spectra show an absorption shoulder around 1.3 eV which we analyze in terms of possible optical transitions involving specific distributions of states in the gap.
We studied heat production in Pd-impregnated alumina powder in the presence of hydrogen and deute... more We studied heat production in Pd-impregnated alumina powder in the presence of hydrogen and deuterium gases, investigating claims of anomalous heat generated as a result of nuclear fusion, usually referred to as a low energy nuclear reaction (LENR). By selecting the water isotope used to fabricate the material and then varying the gas used for loading, we were able to influence the amount of heat released or consumed. We suggest that Pd in its nanoparticle form catalyzes hydrogen/deuterium (H/D) exchange reactions in the material. This hypothesis is supported by heat measurements, residual gas analysis (RGA) data, and calculations of energy available from H/D exchange reactions. Based on the results we conclude that the origin of the anomalous heat generated during deuterium loading of Pd-enriched alumina powder is chemical rather than nuclear.
We evaluate a technique to improve the performance of antenna-coupled diode rectifiers working in... more We evaluate a technique to improve the performance of antenna-coupled diode rectifiers working in the IR. Efficient operation of conventional, lumped-element rectifiers is limited to the low terahertz. By using femtosecond-fast MIM diodes in a traveling-wave (TW) configuration, we obtain a distributed rectifier with improved bandwidth. This design gives higher detection efficiency due to a good match between the antenna impedance and the geometry-controlled impedance of the TW structure. We have developed a method for calculating the responsivity of the antenna-coupled TW detector. Three TW devices, made from different materials, are simulated to obtain their impedance and responsivity at 1.5, 3, 5, and 10 µm wavelengths. The characteristic impedance of a 100-nm-wide TW is in the range of 50 Ω and has a small variation with frequency. A peak responsivity of 0.086 A/W is obtained for the Nb-Nb 2 O 5 -Nb TW diode at 3-µm wavelength. This corresponds to a quantum efficiency of 3.6% and is a significant improvement over the antenna-coupled lumped-element diode rectifiers. For IR imaging, this results in a normalized detectivity of 4 × 10 6 Jones at 3 µm. We have identified several ways for improving the detectivity of the TW detector. Possible methods include decreasing the diode resistance, reducing the noise, and increasing the effective antenna area.
ABSTRACT A recently issued patent [1] describes a method by which vacuum energy is extracted from... more ABSTRACT A recently issued patent [1] describes a method by which vacuum energy is extracted from gas flowing through a Casimir cavity. According to stochastic electrodynamics, the electronic orbitals in atoms are supported by the ambient zero-point (ZP) field. When the gas atoms are pumped into a Casimir cavity, where long-wavelength ZP field modes are excluded, the electrons spin down into lower energy orbitals and release energy in the process. This energy is collected in a local absorber. When the electrons exit the Casimir cavity they are re-energized to their original orbitals by the ambient ZP fields. The process is repeated to produce continuous power. In this way, the device functions like a heat pump for ZP energy, extracting it globally from the electromagnetic quantum vacuum and collecting it in a local absorber. This energy can be used for heating, or converted to electric power.
Numerous reports on gas loading of hydrogen isotope into powdered materials indicate excess heat ... more Numerous reports on gas loading of hydrogen isotope into powdered materials indicate excess heat generation that could be the result of a low energy nuclear reaction (LENR). When the amount of generated heat is small, it is important to characterize the calorimeter to account for possible measurement errors, or artifacts, which can result in long-term apparent excess heat. In this paper we investigate one of those possible measurement artifacts applicable to the gas loading systems that (1) use thermometry as a proxy for energy flow measurements, and (2) run at elevated temperatures. When loading gas into Pd-impregnated alumina, we have found that thermal gradients inside the system result in apparent heating or cooling of the measuring system. We experimentally magnified this effect and confirmed that it was due to temperature nonuniformity inside the calorimetric system. We quantified the effect using a numerical simulation tool to show that a temperature gradient as small as 0.5 K/m might result in 50 mW of apparent excess heat "generation". We suggest a simple approach for investigators to account for this measurement artifact by calibrating their systems with helium gas either prior to, or at the end of, the experimental sequence.
Our group has confirmed excess heat production and isotope effects in alumina and zeolite powders... more Our group has confirmed excess heat production and isotope effects in alumina and zeolite powders containing highly dispersed Pd nanoparticles. Varying the pressures and loading rates produced correlations between the exothermic and endothermic aspects of the experiments. It was shown that the generated power is proportional to the pressurization rate times a quantity , which is the energy content of what we called "fuel". There are two types of fuels, both of which can trigger the reaction that can be either exothermic or endothermic depending on the gas used in the experiment (deuterium or hydrogen). Observed heat generation during the pressurization phase is most likely of a chemical nature.
How wonderful that we have met with^ paradox. Now we have some hope of making progress." -Niels B... more How wonderful that we have met with^ paradox. Now we have some hope of making progress." -Niels Bohr Abstract. Although experimental evidence for retrocausation exists, there are clearly subtleties to the phenomenon. The bilking paradox, in which one intervenes to eliminate a subsequent cause after a preceding effect has occurred, appears on the surface to show that retrocausation is logically impossible. In a previous paper, the second law of thermodynamics was invoked to show that the entropy in each process of a psi interaction (presentence, telepathy, remote perception, and psychokinesis) cannot decrease, prohibiting psi processes in which signals condense from background fluctuations. Here it is shown, perhaps contrary to one's intuition, that reversible processes cannot be influenced through retrocausation, but irreversible processes can. The increase in thermodynamic entropy in irreversible processes -which are generally described by Newtonian mechanics but not Lagrangian dynamics and Hamilton's Principle -is required for causation. Thermodynamically reversible processes cannot be causal and hence also cannot be retrocausal. The role of entropy in psi interactions is extended by using the bilking paradox to consider information transmission in retroactive psychokinesis (PK). PK efficiency, r\ pK , is defined. A prediction of the analysis is that r\ PK ^ HIH Q , where H is the information uncertainty or entropy in the retro-PK agent's knowledge of the event that is to be influenced retrocausally. The information entropy can provide the necessary ingredient for nonreversibility, and hence retrocausation. Noise and bandwidth limitations in the communication to the agent of the outcome of the event increase the maximum PK efficiency. Avoidance of the bilking paradox does not bar a subject from using the premonition of an event to prevent it from occurring. The necessity for large information entropy, which is the expected value of the surprisal, is likely to be essential for any successful PK process, not just retro-PK processes. Hence uncertainty in the communication process appears to be a necessary component of retrocausation in particular, and of PK in general.
We demonstrate the capability of optically addressed spatial light modulators that incorporate su... more We demonstrate the capability of optically addressed spatial light modulators that incorporate surfacestabilized ferroelectric liquid crystals to reproduce gray scale. This capability is based on temporal averaging and is observed in an operating mode in which the applied voltage repeatedly cycles the device between writing and erasing at operating frequencies between 100 and 2000 Hz. A gray scale response is observed for write-light intensities below a saturation level that increases from 100 pW/cm 2 at 100 Hz to 2 mW/cm 2 at 2 kHz. We develop a procedure to determine the modulation transfer function from measurements of the diffraction efficiency as a function of spatial frequency and write-light intensity in a device with a nonlinear transfer characteristic. At an operating frequency of 500 Hz, the modulation transfer function is greater than or equal to 0.50 at a spatial frequency of 40 line pairs/mm.
ABSTRACT The present volumes form the proceedings of the Third International Conference on Ferroe... more ABSTRACT The present volumes form the proceedings of the Third International Conference on Ferroelectric Liquid Crystals, held in Boulder, Colorado, USA 23-28 June 1991. These volumes continue the publication of this conference series, the proceedings of the first conference (1987) held at Bordeaux/Arcachon appearing in Volumes 84 and 85, and the proceedings of the second conference (1989) held at Goteborg appearing in Volumes 113 and 114. As for the two preceding conferences, FLC-91 provided a broad forum for the exchange of information on FLCs, with most of the groups working in the field well represented. Exciting developments were reported in all FLC areas. The worldwide effort at developing new FLC materials continues apace, with the report of an FLC material possessing a spontaneous polarization nearly equal to the sum of all transverse molecular dipoles, and new thrusts in polymer FLCs and FLCs for electronic nonlinear optical applications. The conference saw many new developments in FLC basic and device physics, including the use of dielectric spectroscopy copy as a tool for studying the molecular origins of the polarization in FLCs. Particularly exciting were the FLC device developments with the emergence of sophisticated FLC devices for opto-electronic computing, display, and other light control applications, including a demonstration of a flexible polymer FLC display.
Http Dx Doi Org 10 1080 02678299108033148, Sep 24, 2006
The switching characteristics and the electro-optic response due to the electroclinic effect in c... more The switching characteristics and the electro-optic response due to the electroclinic effect in chiral smectic A liquid crystals are analysed theoretically. We give an exact analytic solution to the dynamic equation of the tilt angle (8) up to the O4 term in the Landau expansion of the free energy. The non-linear behaviour of B and the characteristic. time under an applied electric field are described near the S2-S; transition. They both have a finite value at the transition which depends on the field. The characteristic time (to) exhibits a critical slowing down at sufficiently low fields, which occurs only in the early stages of the switching. At late stages, the switching time exhibits a maximum at a particular temperature which depends on the field, and then decreases in a very narrow temperature range near the transition. The U4 term is important in explainingcertain properties even for very small 6, and it becomes essential for B > 5". The optical response of an electroclinic liquid crystal cell is considered in detail. We derive an expression for the output intensity of light passing through an electroclinic cell. The delay and rise times for the optical signal are shown to a first approximation to be 0.379 to and 2.577 to, respectively.
We present a model of size-dependent luminescence from a-Si:H and show that a blueshift of the lu... more We present a model of size-dependent luminescence from a-Si:H and show that a blueshift of the luminescence energy and a general increase in luminescence quantum efficiency are predicted as structure size decreases. In contrast to bulk a-Si:H structures, highly confined a-Si:H exhibits visible luminescence peak energies and high radiative quantum efficiency at room temperature, which is insensitive to changes in temperature or defect density. We also predict a decrease in mobility and radiative decay time as structure size shrinks. We compare our results with observations of visible light emission from porous silicon.
Biological thin films may form on a surface by specific molecular interactions. The fixed polariz... more Biological thin films may form on a surface by specific molecular interactions. The fixed polarizer ellipsometer (FPE) is a sensitive instrument that detects biological thin films either qualitatively or quantitatively. The design is simple and inexpensive. The assays are formatted on an optical surface, and the FPE detection is based on the phase shift of linearly polarized light after reflection through a thin film. We have constructed mathematical models of the FPE response to reflection through single-layer and two-layer films that agree closely with experimental data. Several biological assays have been measured with the FPE to demonstrate the application of this technology to clinical targets, including ultrasensitive immunoassays for hepatitis B surface antigen (0.1 ng/mL) and ␣-fetoprotein (0.01 ng/ mL) and DNA hybridization (0.5 fmol/L target probe).
We demonstrate the application of an asynchronous image-subtraction optically addressed spatial l... more We demonstrate the application of an asynchronous image-subtraction optically addressed spatial light modulator to particle image velocimetry fringe processing. The device comprises an amorphous silicon p-i-n-i-p photosensor and a ferroelelectric liquid-crystal light-modulating layer. The images to be subtracted are encoded on two separate wavelengths. The operation of the device is described, and characterization shows a frame rate of 100 Hz, a resolution of 3 line pairs/mm, and a write-light sensitivity of approximately equals 1 mW/cm2 at a wavelength of 514 nm. The device is read by the use of light with a 633-nm wavelength whereas the subtraction light is at a wavelength of 670 nm. Using this device to subtract a nonuniform pedestal from the optically computed power spectral density function (the Young's fringe
We report photoemission results from which we directly determined the density of states g(E) in t... more We report photoemission results from which we directly determined the density of states g(E) in the gap of a-Si:H between the top of the valence band E v and the Fermi level. At 0.4 eV above E v, g(E) was found to be ≈1×10 20 cm -3 eV -1 in the undoped film; P-doping increased g(E) in this region whereas annealing reduced it. The photoconductivity-derived optical absorption spectrum matched the shape of the photoemission spectrum, and thus supports the explanation that the photoconductivity shoulder at photon energies in the region of 1.3 eV is due to transitions from localized states above the valence band to the conduction band.
Conference Held in Boulder Co 23 28 Jun 1991, 1992
The present volumes form the proceedings of the Third International Conference on Ferroelectric L... more The present volumes form the proceedings of the Third International Conference on Ferroelectric Liquid Crystals, held in Boulder, Colorado, USA 23-28 June 1991. These volumes continue the publication of this conference series, the proceedings of the first conference (1987) held at Bordeaux/Arcachon appearing in Volumes 84 and 85, and the proceedings of the second conference (1989) held at Goteborg appearing in Volumes 113 and 114. As for the two preceding conferences, FLC-91 provided a broad forum for the exchange of information on FLCs, with most of the groups working in the field well represented. Exciting developments were reported in all FLC areas. The worldwide effort at developing new FLC materials continues apace, with the report of an FLC material possessing a spontaneous polarization nearly equal to the sum of all transverse molecular dipoles, and new thrusts in polymer FLCs and FLCs for electronic nonlinear optical applications. The conference saw many new developments in FLC basic and device physics, including the use of dielectric spectroscopy as a tool for studying the molecular origins of the polarization in FLCs. Particularly exciting were the FLC device developments with the emergence of sophisticated FLC devices for opto-electronic computing, display, and other light control applications including a demonstration of a flexible polymer FLC display.
We outline a procedure to extract the optical-absorption coefficient as a function of energy from... more We outline a procedure to extract the optical-absorption coefficient as a function of energy from measurements of photoconductivity and assess the assumptions involved in applying it to a-Si: H. Using this procedure, we obtain accurate absorption spectra in the range from 1.8 to below 1.2 eV. These spectra show an absorption shoulder around 1.3 eV which we analyze in terms of possible optical transitions involving specific distributions of states in the gap.
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Papers by Garret Moddel