Small-radii curved rib waveguides in GaAs/GaAlAs using electron-beam lithography

Small-radii curved optical waveguides have been fabricated in GaAs/GaAlAs using electron-beam lithography. Ion-beam milling was used as an isotropic etch. The insertion loss of these devices was limited not by bending loss but by input coupling and scattering loss from rib-wall imperfections. A minimum combined bending and scattering loss of 0.6 dB/rad was measured for a 2-μm-wide monomode guide with a radius of 300 μm.