Anisotropic reactive ion etching (RIE) in a SiCl
4:Ar gas discharge has, for the first time, been applied to the fabrication of straight, curved, and branching optical waveguiding structures in GaAs. In the low-pressure (2-10 mT) low-power (∼ 100 W) etching regime, high resolution geometries have been patterned which display linewidth control and sidewall definition that is superior to other etching techniques. Losses of 2,7 and 2.6 dB/cm have been realized for 6- and 10-μm straight rib waveguides (RWG), respectively, at

m.