Effects of static and random magnetic fields on atoms in a gray optical lattice

We study magnetic field-induced modifications of the well-to-well tunneling behavior of atoms in a one-dimensional grey optical lattice. Measurements of the tunneling frequency as a function of the applied magnetic field reveal several tunneling resonances. We further show that the tunneling signal can be suppressed by randomly varying the symmetry of the potential wells. The tunneling is suppressed most effectively if the autocorrelation time of the lattice-well variation is on the order of the tunneling time. Experimental and theoretical results are in good agreement.     

Light saturation of InGaAsP-InP LED's

The saturation behavior of the spontaneous light-current characteristic of InGaAsP (lambda = 1.3 mum) lasers and light emitting diodes are investigated as a function of injection level and temperature. For carrier injection levels below that at which optical gain is observed, it is shown that a nonradiative Auger recombination mechanism is consistent with the observed saturation behavior of the spontaneous emission intensity of lasers. Further evidence of the importance of Auger recombination at these low injection levels is provided by the dependence of the nonradiative component of the measured carrier lifetime (τA) on injection level (n) where it is found thattau_{A}^{-1} propto n^{2.1}. For injection levels above that required to achieve optical gain we report the direct observation of superlinear emission due to single pass gain in edge emitting LED's. The onset of this superluminescence at low temperatures (T < 200K) is found to correspond with the onset of saturation of the spontaneous emission from the sides. These results show that both Auger recombination and superluminescence should be taken into account when the electrooptical characteristics of InGaAsP LED's are calculated.     

Frequency response of a multiplexed charge-transfer delay line

The magnitude and delay responses of a multiplexed charge-transfer delay line are shown to be equal ripple. While the magnitude ripple decreases with increase in the number of parallel channels, the delay ripple is independent of this number and is determined only by the charge-transfer inefficiency.     

Gain and carrier lifetime measurements in AlGaAs single quantum well lasers

We have measured the optical gain and carrier lifetime (τ) at threshold in AlGaAs single quantum well lasers in the temperature range10-70degC. The small shift of the spectral position of the gain peak with increasing injection is evidence for the two-dimensional-like density of states in a quantum well. The net gainGis found to vary linearly with the currentI. The observed slow decrease ofdG/dIand τ with increasing temperature suggests the absence of a large temperature-dependent nonradiative carrier loss or optical absorbtion loss in these lasers. This is also supported by the observed low temperature dependence of the external differential quantum efficiency.     

Some arithmetically symmetrical bandpass filters

A combination of the conventional and Matthaei lowpass-bandpass transformations is shown to result in some bandpass filters with very good arithmetic symmetry.     

On linearity in the special theory of relativity

In deductions of Lorentz transformations of the special theory of relativity, linearity of transformation is always postulated. There are only a few discussions about this linearity in which it is deduced from some basic physical facts. Here, it is shown to be almost a mathematical consequence of the principle of relativity.     

Temperature dependence of electron magnetic resonance and magnetization in NiO nanorods

For NiO nanorods of 5 nm diameter prepared by sol-gel technique, variations of the magnetization M with temperature T (5-370 K) and magnetic field H up to 55 kOe are reported. Also, temperature variations of the EMR (electron magnetic resonance) parameters (intensity I₀, linewidth ΔH and resonance field H_r) of an observed line due to uncompensated spins are followed for The M vs. H and T variations yield a blocking above which the data fits modified Langevin function with magnetic moment μ_p?1240 μ_B/particle. For the EMR line, I₀ decreases rapidly for T<T_B, and the line broadens and shifts to lower H with lowering T, following the lineshift δH_r=(ΔH)ⁿ with n?2.8. This is close to the value of n=3 expected for randomly oriented particles.