Index of content:
Volume 11, Issue 11, 01 December 1967
11(1967); http://dx.doi.org/10.1063/1.1755001View Description Hide Description
The parametric amplification of a short optical pulse, such as is produced by a mode‐locked laser, is treated. The pump signal is also a short optical pulse whose center frequency is twice that of the signal pulse. It is shown that the signal pulse undergoes considerable sharpening. The sharpening is ultimately limited by the mismatch in the group velocities of the pump and signal pulses.
11(1967); http://dx.doi.org/10.1063/1.1755002View Description Hide Description
A new technique for fabricatingoptical diffractiongratings of specified blaze angle is described. The method is based on the formation of a periodic, thermodynamically stable, faceted surface. This arises from variation in surface free energy with surface orientation.
11(1967); http://dx.doi.org/10.1063/1.1755003View Description Hide Description
Output powers up to 63 W/m and lifetimes in excess of 1000 hr are obtained with sealed‐off CO2 lasers. The addition of 0.2 torr H2O or 0.2 torr H2 to the convential mixture of CO2, N2, and He is essential for obtaining these results. The influence of the observed OH radials on the extended lifetime is discussed.
11(1967); http://dx.doi.org/10.1063/1.1755005View Description Hide Description
Nonlinear acoustic sum and difference frequency generation has been observed in fused quartz using the technique of optical Bragg diffraction. The technique possesses significant advantages over direct acoustic detection and should be very useful in other studies of acoustic nonlinearities in optically transparent materials.
11(1967); http://dx.doi.org/10.1063/1.1755006View Description Hide Description
The frequency of the 118.6‐μm water‐vapor laser transition has been measured as 2,527,952.8 MHz in a harmonic mixing experiment. Accuracy of several parts in 108 has been obtained by phase locking the klystron harmonic source to a tunable crystal oscillator and by centering the laser to the Lamb dip.
11(1967); http://dx.doi.org/10.1063/1.1755007View Description Hide Description
A regular spiking pattern has been observed in the light output of GaAs injection lasers with a stripe geometry contact. Computer solutions to the rate equations involving the photon density and the inverted population are compared and found to be in good agreement with the experimental results. The rate equations are based on the assumption that a spatially inhomogeneous inversion exists along the resonator length.
11(1967); http://dx.doi.org/10.1063/1.1755008View Description Hide Description
In a recent communication, Larrabee and Hicinbothem presented measurements of the dielectric constant of high‐resistivity GaAs showing a region of anomalous dispersion centered at 9.5 GHz. We have made similar measurements over the frequency range between 8.5 and 70 GHz but have not obtained their results. Our measurements indicate that the relative dielectric constant is independent of frequency in the microwave range and equal to 12.95 ± .10 at room temperature.
11(1967); http://dx.doi.org/10.1063/1.1755009View Description Hide Description
The dielectric constant of GaAs in the range 1.9–13 GHz has been determined from measurements of the fringing capacitance of bulk samples terminating a coaxial line. There is no indication of a large deviation from the low‐frequency value recently reported by Larrabee and Hicinbothem, although there may be a small resonance effect near 10 GHz.
11(1967); http://dx.doi.org/10.1063/1.1755010View Description Hide Description
The dielectric constant of Cr‐doped semi‐insulating GaAs has been measured from 4 to 40 GHz. Contradictory to the anomalous variation in this range reported by R. D. Larabee and W. A. Hicinbothem, Jr., for oxygen‐doped S‐I GaAs, no frequency dispersion was observed.
11(1967); http://dx.doi.org/10.1063/1.1755011View Description Hide Description
The dielectric constant of gallium arsenide has been measured over the frequency range around 9.5 GHz where a resonance has been reported. No evidence of an appreciable variation in dielectric constant was observed. An accurate measurement at 9.4 GHz gave a dielectric constant of 12.35 and a loss tangent of 5.6 × 10−4.
11(1967); http://dx.doi.org/10.1063/1.1755012View Description Hide Description
The results of EPR and resistivity measurements on vapor‐grown GaP are discussed. The study shows that the appearance of Fe3+ EPR signals and the resistivity values are dependent on substrate orientation. A model based on the formation of Ga vacancies during growth is proposed to account for the observations.
11(1967); http://dx.doi.org/10.1063/1.1755013View Description Hide Description
The Schottky barrier height at the interface of cesium metal and vacuum‐cleaved p‐type GaAs has been found to be 0.63 ± 0.03 eV. These measurements were made photovoltaically at 80°K and indicate that a heavy coverage of cesium leaves the surface roughly intrinsic.
11(1967); http://dx.doi.org/10.1063/1.1755014View Description Hide Description
Radiation sensitive characteristics of a uniform InSb—metal‐oxide‐semiconductor (MOS) structure have been used to detect images. By rapid optical scanning this structure with visible light of 0.63 μ we have detected infrared images due to 5‐μ radiation. In addition information can be read‐in and stored (or ``photographed'') by using 1‐μ radiation, nondestructively read‐out with 5‐μ radiation, and erased with 0.25‐μ radiation.
11(1967); http://dx.doi.org/10.1063/1.1755015View Description Hide Description
Work‐function measurements have been made at room temperature, using the vibrating capacitor technique, on (110) and (100) oriented tungsten single‐crystal surfaces both clean and covered with cesium. After complete cesiation the work functions of the two surfaces were, respectively, 2.06 ± 0.01 eV and 1.82 ± 0.01 eV. On the basis of a model involving epitaxialgrowth of the cesium and a doubling of the lattice constant, the work‐function differences between the two surfaces, clean and cesiated, are found to agree well with the predictions of Smoluchowski. Comparison of the present result on the (110) plane, covered with a monolayer of cesium, with a published value for a thick film of cesium indicates that there may be very little contribution to the work function from atoms in the solid other than those in the outermost atomic layer.