摘要:

The following is theoretically shown: (1) The Freedericksz transition for nematic liquid crystals (NLC) can be defined in a clear‐cut way for cases where NLC is initially aligned uniformly in an arbitrary direction &agr;0and is weakly anchored to cell walls; (2) the critical magnetic field for the transition varies according to the anchoring stiffness. These transition phenomena will make it possible to estimate the anchoring stiffness at the wall.

ISSN:0003-6951    

DOI:10.1063/1.90784

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Spectroscopy of the cadmium sulphide–nickel chloride interface has been performed by measuring the acoustoelectric voltage induced by a SAW‐delay line. Observation of transitions at different radiation wavelengths is attributed to the presence of electronic levels at the interface.

ISSN:0003-6951    

DOI:10.1063/1.90785

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A liquid‐metal gallium‐ion source was imaged by unity‐magnification single‐gap accelerating lens with a postlens deflector to form a focused scanning probe. We report the dependence of the probe diameter and probe current on the lens acceptance half‐angle. The results range between probe diameters of 1000 and 5000 A˚ at currents of 0.12–3.0 nA for half‐angles of 1.2–6 mrad. The current density and brightness at the target for the 1000‐A˚‐diam 57‐kV probe were 1.5 A/cm2and 3.3×106A/cm2 sr, respectively. Astigmatic probes were also produced with dimensions smaller than 1000 A˚.

ISSN:0003-6951    

DOI:10.1063/1.90786

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The depth of melt front penetration induced byQ‐switched ruby‐laser irradiation has been measured by electron microscopy for laser pulses of different duration and energy density in silicon crystals diffused with phosphorous. In as‐diffused specimens (1100 °C 1‐h PH3source) dislocation loops and phosphorous precipitates were distributed to a depth of about 1.0 &mgr;m. The precipitates and loops were dissolved to certain depths by irradiation withQ‐switched ruby‐laser pulses. Dissolving of precipitates provides evidence for melting by the laser radiation, and the depth over which precipitates are dissolved provides a measure of the melt front penetration depth.

ISSN:0003-6951    

DOI:10.1063/1.90787

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Transient absorption in Ne/Xe/HCl mixtures and various rare gas combinations are measured. The observed results are matched with a numerical model to determine the dominant absorbing species in the XeCl laser. In pure neon plasmas Ne*2is a dominant absorber. Addition of xenon greatly reduces this absorption through the mechanism of Penning ionization. Absorption is not changed by adding HCl to the optimum neon‐xenon concentration.

ISSN:0003-6951    

DOI:10.1063/1.90788

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We propose a tunable electronic Raman‐scattering process which yields tuning of the scattered frequency over ≳10 cm−1in the far infrared. For a specific example of donor levels in GaAs and an incident photon frequency of ∼66.2 cm−1(151 &mgr;m), a magnetic field of 10–30 kG yields Raman‐scattering cross sections of 10−24–10−23cm2 sr−1. We show that a tunable Raman laser covering a frequency region from ∼30.7 to ∼16.0 cm−1(i.e., from ∼325 to ∼625 &mgr;m) is feasible.

ISSN:0003-6951    

DOI:10.1063/1.90789

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

AQ‐switched frequency‐doubled Nd : YAG laser was used to record holograms in LiNbO3 : Fe. For 1% diffraction efficiency, only 50 mJ/cm2was needed, as compared to 500 mJ/cm2for cw recording. Induced absorption, comparable in magnitude with the linear absorption at 647 nm, was observed during hologram recording. This indicates the existence of secondary absorption centers in LiNbO3 : Fe. Their contribution to the enhanced photorefractive effect is discussed.

ISSN:0003-6951    

DOI:10.1063/1.90790

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The rate constants for quenching of theBstates of HgBr and HgI by the rare gases and simple halogenated molecules have been measured. The experimental approach consisted of photodissociating either HgBr2or HgI2(in the presence of the desired quenching gas) and recording the subsequent radiative decay of the HgX(X=Br or I) excited‐state population. The large rate constant determined for two‐body destruction of HgBr (B) by Hg (1.3×10−10cm3 sec−1) and bromine donors (Br2 : 5.5×10−10cm3 sec−1) enhances the attractiveness of HgBr lasers pumped by dissociative excitation of HgBr2.

ISSN:0003-6951    

DOI:10.1063/1.90791

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Integral harmonic intensities in the radiation scattered from nanosecond 10.6‐&mgr;m laser‐target interaction have been studied as a function of laser energy and target orientation. Measurements suggest a power‐law dependence of scattered harmonic intensity with increasing laser intensity,In&ohgr;0∝In&ohgr;0, up to ∼1×1014W/cm2incident with evidence of saturation above this level. The scattered harmonic light at 7&ohgr;0was found to be fairly isotropic in front of the target.

ISSN:0003-6951    

DOI:10.1063/1.90775

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Spectral hole burning corresponding to a gain reduction of the order of 1% has been observed in GaAs junction lasers. This observation is made possible by the use of the strong superradiant amplification of the spontaneous emission along the junction.

ISSN:0003-6951    

DOI:10.1063/1.90776

出版商:AIP    

年代:1979

数据来源: AIP