摘要:

A study of photorefractive wave mixing with image bearing beams reveals unique capabilities in spatial modulation, filtering, and cleanup of amplitude and phase modulated beams. We study and explain the negligible image crosstalk in various photorefractive oscillators.

ISSN:0003-6951    

DOI:10.1063/1.98180

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new nonlinear optical crystal 2‐cyclooctylamino‐5‐nitropyridine (COANP) with point group symmetry mm2 has been grown by a temperature difference solution growth technique. Its linear and nonlinear optical properties have been investigated. The refractive indicesna=1.702,nb=1.847, andnc=1.681 (&lgr;=550 nm) and the nonlinear optical susceptibilitiesd31andd33(&lgr;&ohgr;=1.06 &mgr;m) have been determined. Type I phase matching for Nd:YAG lasers (&lgr;=1.06 &mgr;m) has been demonstrated for the configuration using a combination ofd31andd32by angle tuning. A peak efficiency &eegr;=P2&ohgr;/P&ohgr;=3.6% has been observed with a 0.90‐mm‐thick crystal and a fundamental powerP&ohgr;=560 W.

ISSN:0003-6951    

DOI:10.1063/1.98181

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report linewidth narrowing for 1.3‐&mgr;m InGaAsP distributed feedback lasers with either a long cavity length or a detuned Bragg wavelength. The narrowest linewidth measured was 3 MHz at 6 mW for a 780‐&mgr;m long‐cavity laser, and was 8 MHz at 5.5 mW for a 250‐&mgr;m regular‐length laser with detuned wavelength. From our analysis, distributed feedback lasers with 1 MHz linewidth appear to be feasible.

ISSN:0003-6951    

DOI:10.1063/1.98182

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A continuum model has been developed which successfully describes the concentration, movement, and energetics of charged particles within a rf discharge. This model includes continuity equations for all charged particles, Poisson’s equation to determine the local electric fields, and an electron energy balance to determine the ionization and energy‐loss rates. All input parameters (diffusivity, mobility, ionization, and energy‐loss rate) were defined using reported values determined in dc field experiments.

ISSN:0003-6951    

DOI:10.1063/1.98183

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report the use of microsecond current pulses to transform layered crystalline nickel‐zirconium films to amorphous alloy. Starting material was electron beam deposited multilayers with a composition modulation wavelength of 34 nm, an average composition of Ni63Zr37, and a total thickness of 680 nm. Electrical pulses were approximately rectangular and about 3 &mgr;s in duration, with an intensity of several hundred amperes, directly coupling 1.6 to 3 J of energy uniformly into the film. By monitoring current and voltage, the reaction and melting of the sample were observed, and the total energy of the pulse was easily computed. A sharp threshold in pulse energy for sample transformation was observed. A simple heat flow calculation demonstrated that the chemical energy released by the reaction, and the change in diffusion kinetics as the sample temperature exceeded the glass transition temperature of the amorphous alloy, are responsible for this sudden onset. The maximum temperature estimated from this calculation is below the melting point of the constituents, and the cooling rate is 107–108K/s which is in agreement with the formation of amorphous alloy.

ISSN:0003-6951    

DOI:10.1063/1.98184

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Metastable &bgr;‐tungsten was identified, using transmission electron microscopy, in arrays of low pressure chemical vapor deposited contacts on patterned silicon wafers. In contrast, only &agr;‐tungsten was found in films deposited onto bare silicon wafers under identical conditions. Thus, we have shown that contact wells etched through oxide can play a role in determining which tungsten phase is deposited by low pressure chemical vapor deposition. This effect was observed for a variety of furnace conditions (T=300–330 °C, H2/WF6=150:1–400:1). Transmission electron micrographs and selected area diffraction patterns are presented which illustrate the microstructural differences between the &agr;‐ and &bgr;‐tungsten phases. Possible sources of oxygen or fluorine, impurities which are believed to stabilize &bgr;‐tungsten, are discussed and related to the geometry of the vias cut through oxide on patterned wafers.

ISSN:0003-6951    

DOI:10.1063/1.98156

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Transmission electron microscope studies of Ti‐doped, congruent lithium niobate (LiNbO3) have shown that extended structural faults are only present within the Ti‐diffused layer (i.e., the wave guiding region). Structural faults have also been observed in undoped Li‐deficient LiNbO3, though not in undoped control crystals of congruent and stoichiometric LiNbO3. In both Ti‐doped and Li‐deficient LiNbO3, crystal chemistry predicts an increase in the concentration of the point defects V’’’’’Nband Nb....Liand therefore it is appealing to suggest that these defects are responsible for the creation of structural faults. Since the extent of these structural faults is tens of microns, they are clearly potential scattering sites for photons. In this regard, a systematic understanding of their origin and thermal stability is crucial to integrated optical device technologies based on LiNbO3and on the Ti‐doped waveguide fabrication technique.

ISSN:0003-6951    

DOI:10.1063/1.98157

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Microfabrication techniques have been used to prepare a new class of molecular scale microporous materials. These materials are formed by chemically etching slots into alternate layers of a lithographically exposed amorphous superlattice cross section. The slot width is accurately controllable from 10 A˚ to more than 500 A˚.

ISSN:0003-6951    

DOI:10.1063/1.98158

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Si amorphized by Cu implantation has been irradiated by spatially uniform pulses of 7.5 ns duration from a frequency‐doubled neodymium:yttrium aluminum garnet laser. After irradiation the samples were examined by cross‐section transmission electron microscopy. A laterally random pattern of polycrystalline Si patches was found imbedded in amorphous material. At low‐energy densities a considerable fraction of the regrown Si was polycrystalline. With increasing energy density the amount of polycrystalline Si decreased, both at the surface and in total. These results are discussed in terms of the time available for the nucleation of polycrystalline Si at a liquid‐solid interface and the temperature profile in both the liquid and the solid material.

ISSN:0003-6951    

DOI:10.1063/1.98142

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The 1/ffrequency fluctuation of quartz crystal resonators between liquid helium and room temperature is investigated in relation with acoustic attenuation. Large attenuation is observed at 50 K, due to ionic Na+impurity relaxation, at 20 K, corresponding to the interaction of the sound wave with thermal phonons, and below 7 K, which is a behavior already reported in amorphous glasses. A strong correlation is found between 1/fnoise level and acoustic attenuation around the phonon‐phonon relaxation peak; this correlation is not observed on the Na+impurity peak. Below 7 K, 1/fnoise also increases in relation with losses. A possible physical mechanism for 1/fnoise in quartz resonators is discussed.

ISSN:0003-6951    

DOI:10.1063/1.98143

出版商:AIP    

年代:1987

数据来源: AIP