摘要:

A two‐dimensional, time‐dependent analysis is made of array‐compatible bolometers directly deposited onto a single substrate. It applies both to antenna‐coupled and surface‐absorbing configurations. Unlike previous spherically symmetric treatments, it allows analysis of thermal crosstalk between closely neighboring detectors, and of the effects of finite substrate thickness. In a closely packed array of surface‐absorbing detectors, thermal crosstalk generally degrades the array’s resolution more severely than optical (diffractive) crosstalk. Diffraction‐limited resolution with surface‐absorbing detectors is possible only by sacrificing either thermal resistance, and therefore sensitivity, or filling factor. With a minimum substrate thickness ofLmin, a closely packed, diffraction‐limited array is limited to a thermal resistance ofZt≤0.08(&kgr;Lmin)−1, where &kgr; is the thermal conductivity of the substrate. An array of antenna‐coupled bolometers is not subject to this limitation since the thermally and optically sensitive areas need not be equal.

ISSN:0021-8979    

DOI:10.1063/1.346996

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Charge transfer was predicted in the Zn‐Ar system. We have shown experimentally the validity of this prediction and that in fact Ar+excites the Zn+ 2P3/2,1/2states. Moreover, we find that this process preferentially excites theJ= (1)/(2) state in this mixture. This is inferred from the behavior of the intensity ratio of the transition from these two states in correlation with the intensity of the 811.5‐nm line of Ari, where the latter is a measure for Ar ionization. Our model is based on the molecular states of Zn+Ar and Ar+Zn. The model displays a plausible curve crossings leading to the preference2P1/2excitation.

ISSN:0021-8979    

DOI:10.1063/1.346997

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Details of experiments aimed at achieving low ionization state selectivity in molybdenum are presented. Targets are excited with a 10 J CO2laser and the resultant vacuum ultraviolet spectrum (300–700 A˚) has been studied. Combinations of focal spot size, target depth, and target geometries are compared. Simple attenuation of energy is shown not to vary ionization stage composition significantly. Experiments conducted with grazing incidence targets result only in a hot plasma. Modular targets with cooling cylinders of various radii demonstrated good selectivity of the ionization states, but with low absolute signals. Finally, results from combinations of focal spot adjustment and radiative cooling illustrate increased control over desired plasma temperature and density for spectroscopic studies of molybdenum.

ISSN:0021-8979    

DOI:10.1063/1.347192

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Optical emission spectroscopy has been established as a valuable method for the analysis of broad oxygen ion beams. The ion beams used for reactive ion‐beam etching have been investigated in the energy range of 300–1500 eV. From survey spectra O+2molecules and neutral O atoms are identified as main emitting species. Concerning the occurrence of emission lines the beam spectrum resembles that obtained from an O2rf plasma. The intensity ratios however are strongly different within both spectra. Whereas electron impact is the main source for electronic excitation in ordinary etch plasmas, heavy particle collisions are suggested to play an important role in the investigated ion beams. Beam‐induced emissions of atomic oxygen neutrals were recorded at high resolution of 0.1 A˚. The O emission lines were found to be triple peaked. One peak at the unshifted wavelength and two Doppler‐shifted peaks could be resolved. The absolute values of the wavelength shifts are well correlated to the energies of the initial ions extracted from the ion source by a grid optics. Besides slow atoms, atoms moving with the full beam energy as defined by the ion extraction conditions and with only half the beam energy are detected. The observed Doppler structure is attributed to charge exchange and dissociative collisions taking place in the gas phase.

ISSN:0021-8979    

DOI:10.1063/1.346998

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The impedance and emission properties of capacitively coupled Hg‐Ar discharges have been studied in order to determine the limitations of efficiency and radiance of the Hg UV radiation. The background is an application in electrodeless discharge lamps. The Ar pressure was varied between 40 and 1330 Pa, the frequency range was 10–400 MHz. The radiation efficiency generally increases with frequency, in particular at low Ar pressure and high rf power. It is correlated with the variation of the resistive impedance component with rf current and frequency. The results are discussed in terms of a discharge structure consisting of a positive column‐like bulk plasma and two rf sheaths. The frequency dependence is mainly caused by the power dissipation in the non‐luminous sheaths. The power share between bulk plasma and sheaths is determined by a suitable impedance analysis. At high power densities, the efficiency is additionally limited by saturation phenomena. Efficiencies comparable to those known from conventional, electroded discharges can be obtained by a proper choice of parameters such as discharge current and operating frequency. The measurements of the Hg UV radiation are supplemented by a spatially resolved spectroscopy of the Ar excitation. The extension of the dark spaces corresponds to the sheath thicknessdsas derived from the impedance data.dsvaries with Ar pressurepArand frequency  fapproximately as (pAr)−1/3f−1/2. A recently described model for the power dissipation in the sheath of capacitively coupled rf discharges in Ar is also in good agreement with the impedance data of Hg‐Ar discharges. The complex sheath impedance is represented by a semi‐empirical, analytical expression over a wide range of Ar pressures and frequencies.

ISSN:0021-8979    

DOI:10.1063/1.346999

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have experimentally studied the influence of metallic slabs deposited in the vicinity of an optical waveguide on its guided propagation properties. The observed induced optical absorption is well described by the theory of the azimuthal effective‐index method recently proposed by Marcatili and Hardy [IEEE J. Quantum Electron.QE‐24, 766 (1988)].

ISSN:0021-8979    

DOI:10.1063/1.347000

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A rate equation model of a Y‐cavity solid‐state laser with a single active medium operating simultaneously on two laser lines having a common upper level is described. Application is made to Nd3+: YAG, where the 1.06‐&mgr;m and 1.32‐&mgr;m infrared lines can be sum‐frequency mixed to produce 0.589‐&mgr;m yellow radiation. The model is used to optimize cavity design with respect to efficiency of sum‐frequency mixing.

ISSN:0021-8979    

DOI:10.1063/1.347001

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We consider the scattering of electromagnetic waves from perfectly conducting fractal surfaces. The surface is modeled by a multiscaled bandlimited continuous fractal function. We analytically develop a generalized Rayleigh solution for electromagnetic wave scattering from such fractal surfaces. After an examination of the convergence of the Rayleigh systems, we numerically calculate the coupling strengths and relate the angular scattering energy distribution to the fractal descriptors of the surface. We find that the slope of the coupling strengths as a function of their corresponding spatial frequencies on a logarithmic scale depends monotonically on the fractal dimension of the scattering surface.

ISSN:0021-8979    

DOI:10.1063/1.347002

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

ZnSe coated Ag hollow waveguides transmitting CO2laser light were developed. An inner ZnSe coating of good quality was obtained with high rf power and high translating speed in deposition by rf sputtering. The inner ZnSe layer was found to be amorphous by x‐ray diffraction analysis; A layer structure (ZnSe‐Ag) was observed by Auger electron spectroscopy analysis. Transmission properties of the short waveguides with 25 cm length were evaluated by measurements of loss spectra in the mid‐IR region. As a result, ZnSe coated Ag waveguides showed lower loss than the Ge coated one fabricated previously, and the loss for CO2laser light was predicted to be 0.021 dB/m. Furthermore, it was found that a ZnSe coated Ag waveguide is durable in practical use.

ISSN:0021-8979    

DOI:10.1063/1.347003

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Four different erbium laser crystals, two YAG:Er (40 at. %) and two YAlO3:Er (30 at. % and 50 at. %), have been compared with respect to their laser thresholds and slope efficiencies. The performance of these laser crystals was further compared with a YSGG:Cr:Er (Y3Sc2Ga3O12) (3.6 at. % Cr3+and 4 at. % Er3+). The experimental results are explained with up‐conversion processes in the crystals.

ISSN:0021-8979    

DOI:10.1063/1.347004

出版商:AIP    

年代:1990

数据来源: AIP