Benzocyclobutene Microring Resonators

Abstract

Wavelength division multiplexing (WDM) at optical carrier frequencies offers more capacity and flexibility of fiber networks and upgrades conventional point-to-point fiber-optic transmission links to multiuser networks for the demand of high-speed network systems. The microring resonator, which has been seen in action in many photonic devices, is ideal for WDM applications in realization of narrow bandwidth with a wide free spectral range. In this research, microring resonators are fabricated in benzocyclobutene (BCB), a popular polymer in photonics and electronics applications. First, the single-mode BCB undercut-cladding waveguides were designed to reduce bending loss. BCB microring resonators were fabricated based on those principles. BCB single-microring devices were demonstrated as add-drop filters and notch filters with a negative coupling gap. Not only are the microring resonators compact (as small as 5 µm in radius) for photonic VLSI, they also exhibit a high out-of-band rejection (~ 30 dB), high extinction as well as a high finesse (~ 285). In addition, BCB lattices consisting of over one hundred microring resonators were fabricated and demonstrated as bandstop filters. The lattices, despite the large number of resonators, exhibit an extremely low propagation loss. Finally, optical bistability and the field-enhanced all-optical nonlinear switching were demonstrated in BCB microring devices.