Low Loss MMI Couplers for High Performance MZI Modulators

Optical splitters and combiners which can provide precise splitting with low loss, high thermal stability, large optical bandwidth, high compactness, and insensitivity to fabrication tolerances are essential components for high performance Mach-Zehnder Interferometers (MZI)-based optical modulators. In this letter, we theoretically and experimentally investigate the multimode interference (MMI) based structure and the reduction in optical loss achievable through the use of linear tapers at the input and output ports. Our data shows that losses can be reduced to below 1 dB/MMI without affecting the static extinction when employed in MZIs.