Highly asymmetrical vertical coupler wavelengthfilter in InGaAlAs/InP

Abstract
For the first time a narrowband wavelength filter in InGaAlAs/InP is reported. A highly asymmetrical, vertically-coupled directional coupler operating near the band edge is formed by a narrow ridge and a wide strip-loaded waveguide. Operation at a centre wavelength of ~1.5 µm with a bandwidth of 18 Å and transfer efficiency of ~50–70% has been achieved.