Electro-Optically Tunable ${\rm As}_{2}{\rm S}_{3}$ Mach–Zehnder Interferometer on ${\rm LiNbO}_{3}$ Substrate

An electro-optically tunable vertically integrated As
₂
S
₃
Mach-Zehnder interferometer side coupled to a Ti-diffused waveguide on LiNbO
₃
substrate was designed and fabricated. Asymmetric coplanar strip electrodes were placed along the As
₂
S
₃
path, which show strong electro-optic tuning capability, shifting the FSR of the interferometer. The tuning of the TM polarization with 7-mm-long electrodes having a 7-μm gap was observed with V
_π
L = 15.9 V-cm, giving a tuning rate of 0.028 nm/V at 1530 nm. To our knowledge, this is the first demonstration of electro-optic tuning of an As
₂
S
₃
guided mode on LiNbO
₃
substrate.