Demeton Technologies (United States)

This paper describes the design, fabrication, and measurement of backward-wave-cancelled distributed traveling-wave photodetectors. One of the fundamental issues in traveling-wave photodetectors is the generation of backward-waves, which reduces bandwidth or, in the case of matched input termination, reduces their radio-frequency (RF) efficiencies by up to 6 dB. We report a traveling-wave photodetector with multisection coplanar strip transmission lines. The reflections at the discontinuities of the transmission line cancel the backward propagating waves exactly. The bandwidth reduction due to backward-waves is eliminated without sacrificing the RF efficiency. We have demonstrated a broadband backward-wave-cancelled traveling-wave photodetector with three discrete photodiodes. The photodetector is realized in InGaAs/InGaAsP/InP material systems and operates at 1.55 /spl mu/m. A 3-dB bandwidth of 38 GHz and a linear RF output of -1 dBm at 40 GHz have been achieved. The experimental results agree very well with the theoretical calculations.

This present paper is concerned with two main conditions, that of normality of a lattice, and separation and semi‐separation of two lattices, both looked at using measure theoretic techniques. We look at each property using {0, 1} two valued measures and associated {0, 1} valued set functions.For normal lattices we look at consequences of normality in terms of properties of their measures and closely allied set functions. For separation and semi‐separation of two lattices, we investigate the realtionship between regular measures of both lattices, define the notion of weak going up and look at this notion in terms of separation and semi‐separation. We then give necessary and sufficent conditions for semi‐separation in terms of equality of two set fuctions, derived from regular measures on the smaller lattice on the larger lattice.