Dual mode light emitting diode/detector diode for optical fiber transmission lines

Claim 1

A unitary emitter-detector semiconductor diode device with the capability of direct optical coupling to optical transmission lines, the device having means for coupling to electrical forward bias and electrical reverse bias for selection between an optical emitter mode and an optical detector mode, and contact means for coupling to external electrical circuits, the improvement comprising: a unitary combination of a double heterostructure diode having optical and carrier confinement and a photodiode; in said combination a heavily doped semiconductor active layer of one conductivity type of a configuration having opposed surfaces, lateral edges and longitudinal ends, one surface of the said active layer forming a p-n junction with one surface of a coextensive lightly doped semiconducting waveguiding layer of a conductivity type opposite to that of the active layer; a first confining layer having a surface in contact with another surface of the waveguiding layer; a second confining layer having a surface in contact with the other of the opposed surfaces of said heavily doped active layer; a restricted electrical contact to the surface of the second confined layer opposite to the active layer contacting surface; and an optical fiber coupled to the surface of the first confining layer opposite to the waveguiding layer contacting surface, so that the recombination of carriers is isolated to an area directly within the area of the optical fiber.