Compact Semiconductor Tapers for Deep-to-Shallow Etch Transitions

Double-etched taper devices for application as mode converters between shallow and deep-etched waveguides are presented with particular attention paid to the derivation of the taper profile. Finite-difference time-domain simulations of the devices are carried out and compared with fabricated devices along with a transfer matrix method representation that confirms the extraction of values for reflectivity from the transmission spectra of the devices. Tapers of sub-100-mum lengths are shown to exhibit losses of <0.5 dB and reflectivities of <0.05%.