摘要:

Superradiant waveguide evanescent‐type dye lasers are realized by polyurethane top layers containing Rhodamine 6G and Rhodamine B respectively on single‐mode glass waveguides with N2uv laser pumping. A new determination method of gain factor (negative absorption coefficient) by active guide length dependence of a triangle shape top layer is proposed.

ISSN:0021-8979    

DOI:10.1063/1.328097

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A backscattering formula for a single transducer geometry is derived. It expresses the output voltage of the transducer in terms of the angular spectra of scalar and vector acoustic potentials on a plane. The formulation is suitable for acoustic problems involving wide angular spectrum beams. The derived formula gives a simple expression for the problem of a circular transducer facing a plane reflector. The output voltage of a transducer receiving the backscattered waves from an arbitrary size spherical flaw is also presented.

ISSN:0021-8979    

DOI:10.1063/1.328098

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A system of approximate surface wave equations employed in an earlier treatment of the reflection of straight‐crested surface waves by arrays of reflecting strips is extended to the case of variable‐crested surface waves. Although the basic straight‐crested surface wave velocities are determined as in the previous treatment, in the present case a reduction in straight‐crested surface wave velocity in the unplated region due to the adjacent plated regions, which is essential for the existence of the guided transverse modes, is determined by means of a perturbation procedure. The attendant depth dependence for each region is employed in the variational principle as in the earlier treatment, but now the variable cresting relation for the isotropic substrate is incorporated in the description. The resulting equations are applied in the determination of both the transverse modes in each region and the transmission line representation of each mode. The transverse wave numbers in a given mode are taken to be the same in the plated and unplated regions in order that the interior edge conditions be satisfied pointwise. The system of parallel transmission lines is applied in the analysis of the reflection of variable‐crested surface waves by uniformly spaced arrays. The response to a rectangular input of a particular reflecting array consisting of aluminum reflecting strips onST‐cut quartz is calculated and compared with measurements.

ISSN:0021-8979    

DOI:10.1063/1.328099

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

ZnO films with an excellent crystal orientation and surface flatness have been prepared by high‐deposition‐rate rf planar‐magnetron sputtering. A detailed study of these films has been carried out using x‐ray diffraction, scanning electron microscopy, reflection electron diffraction, optical measurement, and electromechanical measurement. These films have thec‐axis perpendicular to the substrate. The value of the standard deviation angle &sgr; of thec‐axis orientation distribution is smaller than 0.5°, and the minimum value of &sgr; is 0.35°, where the sputtering conditions are that the gas pressure is 5×10−3–3×10−2Torr of premixed Ar (50%)+O2(50%) and the substrate temperature is 300–350 °C. ZnO films with a thickness up to 48 &mgr;m have been reproducibly prepared without the decreases of film quality and surface flatness. The surface flatness of these films is similar to that of a glass substrate. An optical waveguide loss for the TE0mode of the He‐Ne 6328‐A˚ line is as low as 2.0 dB/cm in a 4.2‐&mgr;m‐thick film, without postsputtering treatment. The effective surface wave coupling factors are greater than 95% of the theoretical values of the ZnO/glass structure, both in the case of the interdigital transducer (IDT)/ZnO/glass and ZnO/IDT/glass structure.

ISSN:0021-8979    

DOI:10.1063/1.328100

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We present an approximate analytic technique capable of describing the dynamics of nonlinear heat and mass diffusion. The technique is based on using adiabatic approximation in the Green’s‐function formulation and is illustrated for the case of heat transport during pulsed and cw laser annealing of Si. In particular, the heating efficiency is discussed explicitly as a function of pulse intensity for a fixed pulse energy.

ISSN:0021-8979    

DOI:10.1063/1.328101

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Cylindrically converging blast waves have been produced in normal atmospheric conditions by the detonation of the explosives, pentaerythritoltetranitrate, (PETN), over cylindrical surfaces. The shocks generated in this way are so strong that the fronts propagating through the air become luminous of themselves. The production and the propagation of the shocks have been monitored with a framing camera and a streak camera, and the time‐space relations of the shock propagations have been determined using an electrical ionization probing system. The results have shown that the trajectory of the shock fronts near the axis of the cylinder can be approximately represented by the Guderley’s formula.

ISSN:0021-8979    

DOI:10.1063/1.328102

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The effect of spherical expansion on energy coupling to the pusher region of an ablatively driven net‐energy‐gain electron‐beam target is discussed. The effect is evaluated numerically by using the density distribution in the coronal layers, obtained from hydrodynamic calculations, in a spherical‐geometry Monte Carlo transport code. Much of the incident energy is absorbed in the low‐density blowoff or is backscattered. Net energy gain targets will therefore require higher powers, and the optimum shell thickness may be less than predicted by previous calculations, which used deposition profiles for unexpanded material. Nevertheless, energy requirements are slightly lowered due to a decrease in bremsstrahlung heating of the pusher with target expansion.

ISSN:0021-8979    

DOI:10.1063/1.328103

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The addition of a small concentration of suitably chosen noble gas to a reactive plasma is shown to permit the determination of the functional dependence of reactive particle density on plasma parameters. Examples illustrating the simplicity of this method are presented using F atomic emission from plasma‐etching discharges and a comparison is made to available data in the literature.

ISSN:0021-8979    

DOI:10.1063/1.328060

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Studies are reported of stable glow discharges in high‐pressure Hg vapors (?2 amagats) produced by a 20‐nsec ionizing electron beam pulse. The discharges were very stable and operated for 4–5 &mgr;sec after thee‐beam initiating pulse atE/Nvalues up to 8×10−17V cm2and discharge current densities of 4 A/cm2. Power loadings of 3–6 kW/cm3were typically obtained. An electron recombination coefficient of 7.4×10−9cm3 sec−1was measured. Strong continuum radiation from both the visible (4900 A˚) and UV (3350 A˚) bands of molecular Hg were observed. Absorption measurements from 4000 to 6764 A˚ are presented. No gain in this spectral region was ever detected. A peak absorption cross section at 4800 A˚ was estimated to be 2×10−16cm2. The implication of this absorption on other potential laser systems employing Hg as a buffer gas are discussed.

ISSN:0021-8979    

DOI:10.1063/1.328061

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Previously, a simple yet exact characteristic equation was derived for steady‐state longitudinally uniform positive columns in which the electron densityneis given by the continuity equationD∇2ne+&ngr;ne+kn2e=0 with the coefficients independent of position and withne=0 at the boundaries, which can be of arbitrary cross‐sectional shape. The effective coefficients &ngr; andkmay be positive or negative and can each represent the net effect of various electron production and loss processes. The general characteristic equation contains a dimensionless quantityS(the integral of −∇2ne/neover the cross section) which provides information about the shape of the electron density distribution. TheSintegral has been evaluated numerically for circular and rectangular column cross sections. For the case of a circular cross section the variation of the density profile andShave been determined for all possible relative magnitudes and combinations of signs of &ngr; andk. The results provide a generalized parameter map which indicates steady‐state operating conditions for a large class of discharge columns.Svaries from large positive values for diffuse columns (fork<0, i.e., with electron loss by volume recombination) to large negative values for constricted columns (for &ngr;<0, i.e., with loss by attachment). For &ngr;<0, the results indicate that no steady‐state distributions exist with attachment‐dominated loss at the location of maximumne.

ISSN:0021-8979    

DOI:10.1063/1.328062

出版商:AIP    

年代:1980

数据来源: AIP