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Measurements of the Rayleigh-Brillouin spectrum in dense argon gas at T = 298 K and pressures between 70 and 260 MPa are reported. No dispersion in the sound velocity was found up to frequencies of the order of 4 GHz, and low and high frequency measurements agree within 0.5%. This permits the use of hypersonic velocity for deriving thermodynamic quantities for this system. From our measurements we have derived the density behavior of the specific heats ratio γ. Moreover, in absence of dispersion, we have shown that Brillouin scattering gives the sole possibility of measuring both the very low and high sound velocities in fluids, at the same time, therefore giving the direct possibility of checking either the absence or presence of dispersion.

Molecular beam epitaxy has been used for growing self-assembled InAs quantum dots. A continuous variation of the InAs average coverage across the sample has been obtained by properly aligning the (001) GaAs substrate with respect to the molecular beam. Excitation of a large number of dots (laser spot diameter ≈100 μm) results in structured photoluminescence spectra; a clear quantization of the dot sizes is deduced from the distinct luminescence bands separated in energy by an average spacing of 20–30 meV. We ascribe the individual bands of the photoluminescence spectrum after low excitation to families of dots with roughly the same diameter and heights differing by one monolayer.

We demonstrate one-dimensional linear image differentiation, using an array of symmetric self-electro-optic effect devices with 64 × 32 elements. The device operates with pairs of power-supply beams. The spatial derivative, which may be of either sign, is given as the difference in the reflected output powers.

We describe an analog self-electro-optic-effect device that gives a difference between two optical output powers that is linearly proportional to electrical or optical drive, permitting bipolar processing in novel image-processing arrays. The device is able to operate over a range of more than four orders of magnitude optical power, from 50 nW to 2.5 mW, corresponding to uniform incident intensities as low as 3.3 mW/cm^2.