Importance

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Abstract

In multiple quantum well directional couplers, non-centralized input and output legs, occupying major portions of the switches, are continuously forward biased, to produce sufficient gain in light intensity therein to overcome losses in the centralized portions, to in turn provide a transparent (ODB loss) two-by-two coupler switch. Short segments of the centralized coupling portion occupying minor portions of the switches, are switched between forward bias states and zero bias states to provide light beam switching. Thus these switches employ both carrier gain and carrier refraction. The large changes in the index of refraction enable extremely short, low loss, switches to be fabricated and cascaded if desired. A second group of less preferred switches employ solely the carrier refraction effect, by injecting carriers into the waveguides at high levels, preferably equal to or greater than 1.times.10.sup.18 /cm.sup.3.

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First Claim