The propagation of the excitonic polariton along the directional coupl
er consisting of adjacent parallel GaAs quantum-wire waveguides is sim
ulated by using a finite element method. It is found that the coupling
length is as short as 2.5-4 mu m, which is three orders of magnitude
shorter than the conventional optical directional coupler made of bulk
GaAs. Such short coupling length will make it possible to fabricate e
xtremely small optoelectronic devices such as directional-coupler-type
switches. (C) 1996 Academic Press Limited