Reflectivity measurements of deeply etched DBR gratings in InP-based double heterostructures

A three-level masking process has been developed for etching DBR gratings in InP/InGaAsP double hetero-structures. The masking consists of a ZEP/Cr/SiOx layer stack. The ZEP layer is used to open the Cr which is a good mask for etching anisotropically the SiOx layer. The InP-based double heterostructure is etched in an ICP process using Cl2:Ar:H2. With this process deep etched waveguides are simultaneously etched with the DBR gratings with various numbers of periods (1 to 5). 2 µm wide waveguides show a loss of 3 dB/cm and the reflectivity of a 2 period DBR grating was found to be 80%