Index of content:
Volume 13, Issue 7, 01 October 1968
13(1968); http://dx.doi.org/10.1063/1.1652579View Description Hide Description
Low‐temperature conductance peaks have been observed in tunneling measurements on aluminum‐phosphosilicate glass‐degenerate silicon sandwich structures. In magnetic fields up to 84 kOe these peaks split and, with certain assumptions, the g value for the impurity responsible for the peak is found to be 2.1 ± 0.1.
13(1968); http://dx.doi.org/10.1063/1.1652580View Description Hide Description
Single‐crystal lithium niobate has been used as a holographic storage medium. The material undergoes a change in refractive indices upon exposure to suitably intense light thus allowing it to act as a pure‐phase, volume‐holographic medium requiring no processing. The holograms formed have high diffraction efficiencies and are thermally erasable. The high resolution obtained suggests that such material may be useful in high‐capacity, changeable optical information storage, processing and display devices.
13(1968); http://dx.doi.org/10.1063/1.1652581View Description Hide Description
The calculation of filament diameter is based on the wave equation involving field‐dependent electric permittivity for light frequencies expanded up to sixth power of electric field vector. With reasonable assumptions a diameter of 4–6 μ has been obtained. For increasing power fed into the beam two or more filaments may be formed simultaneously. It is believed that there exist relaxation processes inside the filament somewhat diminishing nonlinear terms of electric permittivity. Thus, the solution of the wave equation becomes divergent resulting in filament vanishing. As a result, new filaments occur sequentially, forming an apparent light channel.
13(1968); http://dx.doi.org/10.1063/1.1652583View Description Hide Description
A single pulse was selected from the train of mode‐locked pulses of a Nd‐glass laser using optics external to the oscillatorcavity. Its pulse width was measured by the two‐photon fluorescence technique to be 10 to 15 psec with and without amplification. From energy measurements, the amplified single‐pulse power was determined to be typically 30 GW.
13(1968); http://dx.doi.org/10.1063/1.1652584View Description Hide Description
Emission of electrons into vacuum from a forward‐biased Schottky barrier has been demonstrated experimentally. The emitting contact is a thin layer of platinum on n‐type conducting ZnS with the outer surface of the platinum cesiated to reduce its work function.Capacitance and photoemissionmeasurements indicate that the ZnS:Pt barrier height is 2.3 eV. Under forward‐bias emission is observed.
TIME RESOLVED MEASUREMENTS OF ELECTRON NUMBER DENSITY AND ELECTRON TEMPERATURE USING LASER INTERFEROMETRY AT 337‐μm WAVELENGTH13(1968); http://dx.doi.org/10.1063/1.1652585View Description Hide Description
An experiment is described where a cw HCN laser working primarily at 337‐μm wavelength was used as the source of a Mach‐Zehnder interferometer for the study of plasma decay in the electron number density region 5 · 1015 > ne > 5 · 1013 cm−3. It was found that an estimate of the electron temperature in the range 103−104°K could also be made from the amplitude of the interferometer fringes.
13(1968); http://dx.doi.org/10.1063/1.1652586View Description Hide Description
By using a discharge tube filled with pure neon as a nonlinear element, it has been found possible to obtain simultaneous locking of both longitudinal and transverse modes of a 6328 Å He–Ne laser. Under certain circumstances, each transverse mode has all its longitudinal resonances phase locked to form a narrow pulse, but the pulses corresponding to the various transverse mode orders do not coincide in time. Beam scanning has been observed when the frequency spacing between the transverse modes is a simple fraction of the longitudinal mode spacing. Under these conditions, a ``spot'' of light traces out a zig‐zag path in the laser cavity.
13(1968); http://dx.doi.org/10.1063/1.1652587View Description Hide Description
13(1968); http://dx.doi.org/10.1063/1.1652590View Description Hide Description
Experiments on the sodiumD lines and an 0.82‐Å separated doublet in the iron spectrum have shown that holographically recorded dichromated gelatin diffraction gratings have resolving powers within 90% of theory. The diffraction gratings are of excellent optical quality, have background scatter less than 10−4 of the signal, are ghost free and have greater than 90% first‐order diffraction efficiency. Blazing is accomplished by rotating the grating to the incident angle which satisfies the Bragg condition for the blaze wavelength. The 3‐μ‐thick transmission gratings can be employed from 0.25 μ to at least 15 μ, with gelatin absorption interfering only at 2.6–4.0 μ and 5.8–8.5 μ.
13(1968); http://dx.doi.org/10.1063/1.1652591View Description Hide Description
A theory is given for two branches, I and II, of acoustoelectriccurrent oscillation under a transverse magnetic field in n‐InSb. The peculiar behavior of branch I at high electric fields can be explained by the ``Doppler‐shifted'' amplification and the drastic change of magnetic field dependence of amplifcation of phonons, both of which are due to the large drift velocity of electrons.
13(1968); http://dx.doi.org/10.1063/1.1652592View Description Hide Description
The range and distribution of 200‐ and 400‐ke V boron implanted into silicon in a nonchanneling direction has been investigated by a differential capacitance method. While the range is found to correspond to that predicted from Lindhard's theory of amorphous stopping, the mean deviation does not. From the symmetry of the observed distribution, it is concluded that channeling is not responsible for the discrepancy.
13(1968); http://dx.doi.org/10.1063/1.1652593View Description Hide Description
Evidence is presented indicating that, in some cases at least, a sinusoidal phase modulation is responsible for the spectral broadening observed in trapped filaments of laser (and Raman) light. This kind of modulation has been suggested recently by Cheung et al.