摘要:

A scalar and a vector Mathieu transform pair are developed and their properties are discussed. The orthogonality relationships of the transform kernels are derived in both the spatial and the spectral domains. Finally, Parseval’s theorems for the two transforms are derived.

ISSN:0021-8979    

DOI:10.1063/1.337636

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

In this paper we present an optical method to control the geometry of buried layers in optoelectronic heterostructures. The technique uses an optical microscope equipped for infrared applications and relies on the fact that the different layers of the multilayer structure have different band gaps. Accordingly transmission/absorption, reflectance, and photoluminescence of the inidividual layers exhibit their characteristic near‐band‐gap spectral variations at different wavelengths. By appropriate selection of the wavelength range used for image formation, any layer of interest can be made visible. As an example we investigated a mushroom‐type InGaAsP/InP 1500‐nm laser structure with subsequent mass transport. Both technological steps, the formation of the mushroom by underetching, and the regrowth by mass transport represent critical processes in the fabrication of these index‐guided lasers. Our results show clearly that the successful accomplishment of the process can be controlled by images of the selected buried layer. Contrast and resolution of the pictures are sufficient to show any irregularity in etching or regrowth. The main advantage of the method is that it offers the possibility of investigating whole wafers without sample preparation and in a nondestructive way, which is in marked contrast to observation with a scanning electron microscope, where only profiles along cleaved facets can be inspected.

ISSN:0021-8979    

DOI:10.1063/1.337637

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The two infrared (10‐&mgr;m) wave fronts of an interferometer (Michelson or Mach‐Zehnder) interfere separately with a tilted reference beam on a dynamic recording medium consisting of a thin oil film on a glass substrate. Illumination of this twin hologram with a visible (He‐Ne) beam reconstructs simultaneously, in the same direction, two wave fronts characteristic of each arm of the interferometer. Practical realization and experimental constraints, such as air turbulence and mechanical vibrations, are easily satisfied with these long‐wavelength interferometers. Experimental results include air wedge determination, homogeneity test of a NaCl plate, step deposit evaluation and afocal assembly analysis. The real‐time aspect of our recording medium also permits the visual observation of transient phenomena.

ISSN:0021-8979    

DOI:10.1063/1.337638

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

In order to enhance the efficiency of a blue‐green laser through spectrum conversion of the pumping light, a converter dye BBQ was mixed in the laser dye solutions. The laser was pumped with a plasma radiation source. The increase of laser output over the maximum obtainable from the pure dye operation was better than 80% for the dye mixture of LD490+BBQ or coumarin 503+BBQ. The estimated enhancement calculated by a simple spectrum conversion model agrees well with the experimental results. The enhancement is mainly effected by irradiance in the UV from the pumping source, the fairly good match of the fluorescence band of converter dye with the absorption band of the laser dye, and the lack of the overlap of the fluorescence band of the laser dyes with the triplet–triplet absorption band of the converter dye used.

ISSN:0021-8979    

DOI:10.1063/1.337639

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A general solution of the heat diffusion equation is presented for the case of a semi‐infinite two‐layer system that is heated with a localized cw laser beam of Gaussian or uniform circular intensity profile. As an example, this theory is applied to thin layers of a thermoluminescent material on glass substrates. The transient thermoluminescence emission response is calculated and compared with experimental results, illustrating the validity of the solutions. Applications to transient laser heating of oxide‐semiconductor sandwiches are discussed.

ISSN:0021-8979    

DOI:10.1063/1.337640

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We have studied the relation of the energy‐loss rate and the enhanced diffusion with the amplitude of spontaneously excited low‐frequency plasma oscillation in a current‐carrying argon plasma. The experimental results (radial distributions of the electron density, electric floating potential, and electric field) and the theoretical model that is developed showed the important role of the low‐frequency plasma oscillations on the additional power losses of the plasma. Also, the energy‐loss rate has been studied as a function of the plasma radius.

ISSN:0021-8979    

DOI:10.1063/1.337590

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Spatially resolved soft x‐ray spectra were collected for neon plasmas produced by imploding hollow annular gas puffs with MA level driving currents. TheZ‐pinch imploded plasmas were studied for different risetime currents produced with or without the use of a plasma erosion opening switch (PEOS). Selected spectrograms were processed and analyzed to obtain absolute energies for the radiation emitted in the Ne ixand Ne xdiscrete transitions, as well as for total emission over the spectral range 900–1600 eV. The neon plasmas radiate 1–2.5 kJ in this energy range predominantly in the &agr; transitions of both ions. The plasma uniformity inferred from spatially resolved spectral lines improves significantly using a faster rise‐time driving current.

ISSN:0021-8979    

DOI:10.1063/1.337591

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Discharge time lag is experimentally studied when a single stepped voltage is applied to a gap with a stationary electron‐beam injection in a low‐pressure gas (0.06–2 mTorr). The time lag is found to be almost independent of the electron‐beam density. The beam density does, however, determine a discharge current, which is independent of the applied gap voltage and beam energy. A systematic measurement of the time lag as functions of the gap voltage, beam energy, gas pressure, and gap length is presented. The time becomes extremely short when the beam energy exceeds the ionization energy of the gas. The time lag, when a single pulsede‐beam is injected into the dc gap field, is also studied. The result is essentially the same in spite of pulsed operation.

ISSN:0021-8979    

DOI:10.1063/1.337592

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We present x‐ray absorption measurements on silicon clusters and silicon plasmas produced by pulsed laser irradiation of bulk silicon. The results are compared with earlier time‐resolved x‐ray absorption measurements on amorphous silicon foils under pulsed laser irradiation. Clusters are formed at an irradiance as low as 3.0 J/cm2. At an irradiance of 14 J/cm2ionized species up to Si4+are formed. We find a removed Si layer thickness of 80 A˚ at an irradiance of ≊6 J/cm2, at 15 ns pulse duration.

ISSN:0021-8979    

DOI:10.1063/1.337593

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This paper describes a theoretical treatment for the current neutralization of intense ion beams propagating radially inward through the drift region of a cylindrical Applied‐Bdiode. The drift region is bounded by conducting walls, and the beams are taken to have a current density profile that is constant across the surface transverse to the direction of propagation. The current neutralization calculation involves breaking the return current density into spatial harmonics in the transverse coordinate in such a way that the return current density vanishes at the walls. Each spatial harmonic is then shown to approximately obey a magnetic decay equation with a time constant proportional to the electrical conductivity of the gas. This conductivity is time dependent and is calculated locally from the degree of ionization and plasma heating created by the beam and the return current. Beams composed of protons and carbon ions are considered, and time‐of‐flight effects on the beam current and energy spectra are taken into account. The effects of drift region parameter variations on the time development of the conductivity and current neutralization are evaluated. Comparisons are made with experimental measurements taken at Sandia National Laboratories on the Proto‐I accelerator, and strengths and weaknesses of the present model are discussed.

ISSN:0021-8979    

DOI:10.1063/1.337797

出版商:AIP    

年代:1986

数据来源: AIP