Active modelocking of semiconductor diode lasers in an external cavity by synchronous electrical pumping is a simple and attractive method for generation of short optical pulses in the wavelength region of interest for optical communication [1]. Up to now, most attention has been paid to the time-averaged behaviour of pulse width, optical spectrum and time-bandwidth product, but pulse intensity fluctuations are of major importance in communications and logic applications. In this paper we investigate this type of noise and demonstrate a partial suppression by cw injection locking. Similar results have previously been demonstrated in a CO2 laser [2].
A recently proposed position, rotation, and scale-invariant optical pattern recognition system using a holographic logpolar mapping filter is analyzed with respect to resolution and accuracy. The limits are set by the resolution of the mapping filter, which must have a bandwidth proportional to the square of the input bandwidth. With 1800 x 1800 pixels in the computer-generated mapping filter, we get a maximum input field of 24 x 24 pixels and an angular resolution of 4.80 degrees . Determination of the position of the input object is possible with at best 50% relative accuracy, and, in practice, multiobject capability is highly questionable. Numerical simulations and experimental evidence support the resolution limits found.
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