Volume 13, Issue 11, 01 December 1968
Index of content:
13(1968); http://dx.doi.org/10.1063/1.1652473View Description Hide Description
Q‐switched laser emission is calculated using a fluctuating dipole model of spontaneous emission. The emission pattern for a broadband noise source is a complicated quasi‐periodic train of short pulses.
13(1968); http://dx.doi.org/10.1063/1.1652474View Description Hide Description
In a saturated absorption experiment with neon in a 6328‐Å He–Ne laser one can select a combination of isotopes of neon in the gain tube and the proper isotope in the loss tube so as to bring the maximum of the gain curve to the same frequency as that of the saturated absorption peak.
13(1968); http://dx.doi.org/10.1063/1.1652475View Description Hide Description
The induced index changes associated with thermal blooming have been observed in iodine‐doped CCl4 by means of a Mach‐Zehnder interferometer. The interference fringe shape next to the window and the temporal growth of the peak fringe displacement at various positions in the cell have been analyzed. Both the conductive and convective stages of thermal blooming are observed.
13(1968); http://dx.doi.org/10.1063/1.1652476View Description Hide Description
Possibilities of observing light scattering from an intense laser beam, whose electric field in well‐defined conditions can cause total orientation of the scattering microsystems, are investigated on the basis of a simple classical theory. This saturation of orientation affects the scattered light and should be accessible to measurement in solutions of macromolecules or colloidal particles by usual laser technique, whereas in molecular liquids it cannot be made apparent even if using the focused beam of a strong laser. The measurements under consideration are proposed as a novel and simple method of determining the sign of the optical anisotropy of macromolecules and colloidal particles.
13(1968); http://dx.doi.org/10.1063/1.1652477View Description Hide Description
Strong mode‐coupling was induced in a long 6328‐Å He–Ne laser by the addition of a separate cell containing excited Ne. The resulting single‐frequency output power represented most of the total multimode power available. The laser maintained the same mode of oscillation when tuned throughout the entire gain band. This scheme has produced 9.5 mV at a single frequency and was apparently free from any inherent power limitation.
13(1968); http://dx.doi.org/10.1063/1.1652478View Description Hide Description
Four specific experimentally observed phenomena associated with a laser‐produced carbon plasma in a vacuum are described. They are superheating of the target surface, a sharply defined and slightly indented leading boundary of the expanding plume, a density precursor in the expanding plume, and the merging of the electron and ion temperatures at very high laser fluxes. These observations are explained in terms of the effects of the laser beam's radiation pressure on the otherwise freely expanding plasma. The radiation pressure for a typical 10‐J Q‐switched ruby laser pulse with a half width of 65 nsec is equivalent to a maximum of 10 atm of pressure when focused to a 1‐mm‐diam spot.
13(1968); http://dx.doi.org/10.1063/1.1652479View Description Hide Description
The orientation dependence of the backscattered yield of 1.8‐MeV carbon ions has been used to determine the lattice location of In, Tl, Sb, Bi, and Pb ions implanted into Ge at 30–40 keV and at temperatures between 300° and 350°C. Similar to the behavior in silicon, the group IV and V elements are found to be highly substitutional. Thallium exhibits nearly equal numbers of atoms in the 〈111〉 interstitial sites and on the substitutional sites (as in Si). In indiumimplants, on the other hand, we find no evidence of the clearly defined interstitial component previously seen in Si. In all cases, we observe substitutional concentrations orders of magnitude above thermal equilibrium solubilities.
13(1968); http://dx.doi.org/10.1063/1.1652480View Description Hide Description
It is shown that substrate bias during dc sputtering effectively reduces oxygen contamination in nichrome films. This in turn leads to an enhancement of the preferred orientation of the deposits. Moreover, it appears that substrate bias plays an additional role in film orientation which is related to the initial nucleation and growth conditions.
13(1968); http://dx.doi.org/10.1063/1.1652481View Description Hide Description
Stimulated emission has been observed from an electrically accelerated copperplasma at 5106 and 5782 Å in a device employing a series of plasma guns which inject the vapor into the laser resonator. In addition to facilitating room temperature operation of a copper laser, this technique provides a flowing active medium which has extended the pulse duration by more than four‐fold over that originating from a stationary vapor.
13(1968); http://dx.doi.org/10.1063/1.1652482View Description Hide Description
Stimulated emission to 3 × 108 W/cm3 (about 200‐kW peak) have been obtained from CdS platelets, using a 3‐nsec, 260‐keV electron accelerator. Data are reported from 20 to 1400 A/cm2 at 300°K, and 500 A/cm2 at 77°K showing approximately constant efficiency at points well above threshold.
13(1968); http://dx.doi.org/10.1063/1.1652483View Description Hide Description
Reproduction of x‐ray diffraction topographic images has been made at about 25 diameters enlargement by a closed‐circuit television camera system with an x‐ray sensing Vidicon tube which utilizes a beryllium window and PbO photoconductive target. The height of video signals is exactly proportional to x‐ray intensity, and intensity distribution can be observed as a video waveform. It is shown that the television image system can be used for rapid observations of topographic images such as Pendellösung fringes and imperfections in crystals, although its resolution (about 30 μ) is inferior to that of the photographic method.
13(1968); http://dx.doi.org/10.1063/1.1652484View Description Hide Description
A superconductingNb TM010 mode cavity at 8.5 GHz machined from a single piece of reactor‐grade electron‐beam‐melted Nb to avoid joints had an unloaded Q (Q 0) of 2 × 1010. After some degradation in the Q 0, which took place as the microwave fields were increased, a high Q 0 of 1 × 109 was obtained at a peak electric field on the cavity surface of 27 MV/m. These results were obtained by using ultrahigh‐vacuum firing and chemical polishing of the Nb cavity, and ultrahigh vacuum within the cavity during measurement. The high Q 0 at high electric field demonstrates the usefulness of superconductingNb cavities for devices such as linear particle accelerators and rf separators.
13(1968); http://dx.doi.org/10.1063/1.1652485View Description Hide Description
The observation of photocurrents generated in Schottky barrierdiodes on Remeika‐grown reduced bariumtitanate is reported. Photon‐to‐electron conversion efficiencies of 5% at 0.3 μm have been measured which suggests that the effect may be large enough for employment in practical devices.
13(1968); http://dx.doi.org/10.1063/1.1652486View Description Hide Description
Alloy specimens, after predeformation at 4.2°K and intermittent holding at higher temperatures, respond to reapplication of stress by transient evolution of heat. These heat bursts have been measured and are interpreted as due to the breakdown of unstable defect configurations.
13(1968); http://dx.doi.org/10.1063/1.1652487View Description Hide Description
Efficient cw second harmonic conversion to 2573 Å has been achieved in an argon laser cavity by means of the nonlinear materials ADP and KDP. Peak SH power was 415 mW which represented 50% efficiency. Trace impurities in the crystals prevented the realization of theoretical efficiency. An increase in cavity loss was observed during the simultaneous presence of fundamental and SH beams.