摘要:

A large number of laser transitions in the 11–17‐&mgr;m region have been obtained by optically pumping CF4, NOCl, CF3I, and NH3with a single line‐tunable CO2TEA laser. These lasers have respectable conversion efficiency and can be scaled to high energies in a spectral region where the selective excitation of molecules is prerequisite to performing selective photodissociation and laser‐induced chemistry experiments.

ISSN:0021-8979    

DOI:10.1063/1.324368

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A 60‐&mgr;m‐thick and 0.5‐mm‐long LiNdP4O12slab waveguide laser clad by sputtered SK12 glass was fabricated. Single TE0‐mode pulse and quasi‐cw laser oscillations at 1.047 &mgr;m were obtained by longitudinal pumping with a rhodamine 6G laser and an argon laser, respectively. The round‐trip waveguide loss was evaluated from the threshold pump pulse energy to be 0.035 for TE0‐mode oscillation.

ISSN:0021-8979    

DOI:10.1063/1.324369

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Liquid‐phase epitaxial (LPE) single and multiple thin quaternary layer In1−xGaxP1−zAszlaser diodes (x∼0.13,z∼0.28; &lgr;∼1.1 &mgr;m, 77 °K) that exhibit quantum size effects (QSE) are described. LPE quaternary active layers approachingLz∼200 A have been achieved. As a prototype for the behavior of multilayer heterostructures, the operation of single In1−xGaxP1−zAszpotential wells, or recombination layers, located a small distance into thepside of an InPp‐njunction, is considered. Almost all the carrier recombination is observed to occur in the quaternary potential well, and little absorption occurs in the single‐active‐layer structure, consistent with the small change in the effective index of refraction measured in a large range (1500 A, 150 meV). This general behavior, i.e., single‐well recombination, is observed also in thin‐active‐layer multilayer heterostructures in which the InP layers between quaternary layers are relatively thick (400–1000 A). In multilayered diode structures, distributed feedback may contribute, along with QSE, to modulation of the longitudinal (Fabry‐Perot) modes.

ISSN:0021-8979    

DOI:10.1063/1.324370

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A technique has been developed for determining the optical‐transmission rise times of subnanosecond switching KD*P electro‐optic modulators. Optical streak‐camera data with 15‐psec overall resolution and 30‐psec resolution electrical sampling measurements taken on several commercial devices are reported.

ISSN:0021-8979    

DOI:10.1063/1.324371

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The limitations of high‐power electrical lasers due to heating of the gas and the instability of the glow discharge can be alleviated by the flow of the lasing medium. We describe here the results of two experiments which combine glow discharges with gas flow. In the first experiment we study the effects of supersonic flow and shock waves on glow discharges. The results of some numerical calculations of the variation of the gas properties along the discharge tube are then described. In the second experiment the influence of a highly swirled and turbulent flow on electrical discharges is studied. It is observed that both flows have a favorable effect on the discharge stability.

ISSN:0021-8979    

DOI:10.1063/1.324339

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A perturbation formulation of the equations of linear piezoelectricity is obtained using a Green’s function approach. Although the resulting equation for the first perturbation of the eigenvalue strictly holds for real perturbations of real eigenvalues only, it is formally extended to the case of purely imaginary perturbations of real eigenvalues. The extended equation is applied in the calculation of the attenuation of surface waves due to the finite electrical conductivity of thin metal films plated on the surface and air loading. The influence of the viscosity of the air is included in the air‐loading analysis, and the calculated attenuation increases accordingly. Since the metal films are thin compared with a wavelength, an approximate thin‐plate conductivity equation is employed in the determination of the attenuation due to the electrical conductivity of the films. The resulting attenuation is obtained over a very large range of values of sheet conductivity. This is accomplished by using the equation for the first perturbation of the eigenvalue iteratively to determine the solution and attendant attenuation to any desired degree of accuracy. The phase velocity dispersion curve due to the mechanical effect of a thin film plated on a substrate is determined for relatively large wavelengths by employing the perturbation equation iteratively, and excellent agreement is obtained with the results of other more direct approaches. The calculations have been performed for an aluminum film on either ST‐cut quartz orY‐Zlithium niobate.

ISSN:0021-8979    

DOI:10.1063/1.324340

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Past work has shown that surface‐active environments can influence the hardness of such nonmetallic solids as silver chloride, magnesium oxide, alumina, quartz, and soda‐lime glass. Specifically, a maximum in hardness can be produced when the &zgr; potential of these solids is zero. This ’’&zgr; correlation’’ has been taken to imply that surface charge can markedly influence near‐surface hardness and, in particular, that solids are hardest when their surface charge is zero. To test this implied relationship between surface charge and hardness in a more direct fashion, the hardness of the (0001) surface of ZnO has been measured as a function of surface charge controlled using an electrolytic cell. The results of this study demonstrate that for ZnO a maximum in hardness is produced, but apparently not when the surface charge is zero. Rather, the hardness maximum is observed when the ZnO surface is positively charged (modest downward band bending). Moreover, previous suggestions attempting to explain the ’’&zgr; correlation’’ are shown to be inapplicable to the present results on ZnO, and an alternative mechanism involving charge exchange between donor levels and the conduction band is suggested.

ISSN:0021-8979    

DOI:10.1063/1.324341

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

This paper presents an interferometry study of a CO2laser plasma focus created in a 1‐cm copper annular target. The average electron density measured on the plasma axis is approximatelyne∼1.6×1018cm−3. Spatial and temporal plasma luminosity measurements suggest a simple model for the plasma motion. This laser‐produced plasma has an axis and a plane of symmetry which make it an interesting subject for further studies on laser plasma interactions.

ISSN:0021-8979    

DOI:10.1063/1.324328

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A method of calculation of corona‐onset and breakdown voltage in short point‐to‐plane air gaps is proposed in this paper. This method is based on the assumption that for corona (for negative voltage on the point electrode) or breakdown (for positive voltage on the point electrode) to occur, the energy input into the gap due to the formation of an electron avalanche should reach a critical value. The critical value of the energy is calculated numerically from the known experimental value of the breakdown voltage in uniform field. The corona‐onset and breakdown voltages calculated from the proposed method are compared with other existing methods as well as with experimental results.

ISSN:0021-8979    

DOI:10.1063/1.324329

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The EUV emission from 10‐ to 100‐mg/cm2‐thick planar targets (Z=6–79) exposed to 60‐nsec‐duration focused relativistic electron beams was examined at current densities of 0.4–1.0 MA/cm2. Spatially resolved spectra were obtained with a stigmatic near‐normal incidence spectrograph, in the wavelength range 500–2100 A˚, along axial and radial directions. Time‐resolved EUV data were obtained with windowless photoelectric diodes operated unfiltered and filtered with 0.5‐&mgr;m‐thick aluminum. The axial views show copious emission from the diode gap associated with late‐time impedance collapse. Radial views show continuum radiation which is emitted from the region of the target exposed to the focused REB and line radiation which originates from a lower‐density (approximately 1019cm−3) more‐extended late‐time plasma resulting from foil expansion. The region of the foil exposed to the focused REB radiates as a blackbody source with a peak temperature of 2–6 eV. These temperatures are a factor of 2 below the calculated temperatures for classical deposition in the foils exposed to the focused beam assuming no hydrodynamic foil expansion.

ISSN:0021-8979    

DOI:10.1063/1.324330

出版商:AIP    

年代:1978

数据来源: AIP