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Perry, J. W.

Publications and source records attributed to Perry, J. W..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Enhanced Reverse Saturable Absorption and Optical Limiting in Heavy-Atom Substituted Phthalocyanines

The reverse saturable absorption and optical limiting response of metal phthalocyaninies can be enhanced by using the heavy-atom effect. Phthalocyanines containing heavy metal atoms, such as In, Sn, and Pb show nearly a factor of two enhancement in the ratio of effective excited-state to ground-state absorption cross sections compared to those containing lighter atoms, such as Al and Si. In an f/8 optical geometry, homogeneous solutions of heavy metal phthalocyanines, at 30% linear transmission, limit 8-ns, 532-nm laser pulses to less than or equal to 3 (micro)J (the energy for 50% probability of eye damage) for incident pulses up to 800 (micro)J.

metal phthalocyanines↗
NASA NTRS1993

Optimization of the First and Second Hyperpolarizabilities of Organic Dyes (abstract)

We have been attempting to correlate hyperpolarizabilities with bond-length alteration (BLA), which is defined as the difference in the average length between adjacent carbon-carbon bonds in a polymethine [(CH)(sub n)] Polyenes have alternating double and single bonds (bond length equal to 1.34 Sand 1.45 U respectively), and thus show a high degree of bond-length alteration (BLA = -0.11 u.

organic dyes carbon-carbon bonds hyperpolarizabili↗
NASA NTRS1993

Experimental Demonstration of the Dependence of the First Hyperpolarizability of Donor-Acceptor Substituted Polyenes on the Ground-State Polarization and Bond Length Alternation

The dependence of the product of the first hyperpolarizability, beta, and the ground-state dipole moment, mu, for a series of donor-acceptor polyenes with a large range of ground-state polarization, was measured in a variety of solvents by electric field induced second harmonic generation. The observed behavior of mu times beta as a function of ground-state polarization agrees well with theoretical predictions. In particular, as a function of increasing polarization, mu times beta was found to first increase, peak in a positive sense, decrease, pass through zero, become large and negative, and eventually peak in a negative sense.

hyperpolarizability donor-acceptor substituted pol↗
NASA NTRS1992

Direct measurements of nonlinear absorption and refraction in solutions of phthalocyanines

Direct measurements are reported of the excited singlet-state absorption cross section and the associated nonlinear refractive cross section using picosecond pulses at 532 nm in solutions of phthalocyanine and naphthalocyanine dyes. By monitoring the transmittance and far-field spatial beam distortion for different pulsewidths in the picosecond regime, it is shown that both the nonlinear absorption and refraction are fluence (energy-per-unit-area) rather than irradiance dependent. Thus, excited-state absorption is the dominant nonlinear absorption process, and the observed nonlinear refraction is also due to real population excitation.

Wei, T. H.↗
NASA NTRS1988

Silane and germane plasma diagnostics for depositing photosensitive a-SiGe:H films

Highly photosensitive a-SiGe:H films with a light-to-dark conductivity ratio of 8 x 103 and an optical bandgap of 1.40 eV have been produced by RF glow discharge using hydrogen dilution of SiH4 and GeH4 mixed gas plasma. The critical role of hydrogen dilution in GeH4 containing plasmas is to suppress the gas-phase polymerization and promote the incorporation of Ge into the film. It is observed that inelastic laser light scattering of the RF plasma is a sensitive method for monitoring the onset of the gas-phase polymerization. In situ coherent anti-Stokes Raman spectroscopy measurements have shown that the dissociation rate of GeH4 is a factor of three larger than that of SiH4.

Shing, Y. H.↗
NASA NTRS1987

In situ process diagnostics of silane plasma for device-quality a-Si:H deposition

Coherent anti-Stokes Raman spectroscopy (CARS) and mass spectrometry (MS) have been applied to in situ process diagnostics of a silane plasma for device-quality a-Si:H film deposition. Silane depletion was directly measured by CARS and is linearly dependent on RF power in the region of 4-12 W with a slope of 0.5 percent/mW-sq cm. The depletion is also dependent on SiH4 flow rate starting with a 50 percent depletion at a low flow rate of 5.6 sccm and asymptotically approaching an 8 percent depletion at a flow rate of 80 sccm. The mass spectral line signal intensity of disilane increases with RF power and shows an apparent transition at 6 W. Disilane formation in silane plasma, film deposition rate, and silane depletion ratio as a function of the RF power indicate that the film growth mechanism in the low-power region of 3.5-6.5 W is substantially different from that in the high-power region of 6.5-12 W.

Shing, Y. H.↗
NASA NTRS1987

Amorphous silicon deposition diagnostics using coherent anti-Stokes Raman spectroscopy

This paper reports on an in situ silicon deposition process diagnostics, using CARS performed at state-of-the-art a-Si:H film deposition conditions in a reactor designed for a-Si:H solar cell fabrication. The diagnostics procedure measures the silane depletion in an RF plasma as a function of the silane flow rate (where the relationship is linear between 50-percent depletion, at a flow rate of 5.6 sccm, and about 8-percent depletion, at 80 sccm) and the RF power (where the silane depletion is linearly dependent on the RF power in the region of 4 to 12 W). The linear RF power dependence of the silane depletion is considered to be consistent with the mechanism of silane decomposition primarily by electron impact dissociations, while the flow rate dependence is interpreted in terms of the residence time of the SiH4 molecules in the glow discharge region, where an increase of the residence time at a low flow rate results in a high depletion ratio.

Shing, Y. H.↗
NASA NTRS1986

Direct picosecond time resolution of unimolecular reactions initiated by local mode excitation

Attention is given to the first results of direct, picosec measurements of the Delta-nu(OH) 5 local mode transition of H2O2. These time-resolved studies yield a direct measure of the unimolecular dissociation rate, and furnish a lower limit for the rate of energy redistribution from the OH stretch to the O-O reaction coordinate. The data thus determined may be used to ascertain the domain of validity for statistical unimolecular reaction rate theories.

Scherer, N. F.↗