Very compact ring resonators with conventional waveguides, total internal reflection mirrors and etched beam splitters

Ring resonators have been received much attentions because they can provide a wide range of optical signal processing functions as stand-alone devices or building blocks of more complicated photonic devices. Additionally, their possibility of compact size enables high levels of photonic integrations. For the realization of complex photonic integrated circuits they should be integrated with other active and passive components. Most of these components are based on weakly confined waveguides, which can be engineered to have low propagation loss and high optical gain. However, using such waveguides it is very difficult to reduce ring resonator size due to lack of compact low radiation loss bends and short couplers. Possible solutions are total internal reflection mirrors for abrupt bends and etched beam splitters for submicron couplers.;This dissertation reports on the experimental study and theoretical analysis of total internal reflection mirrors, etched beam splitter and novel compact ring resonators based on these components. Total internal reflection mirrors were demonstrated with loss as low as 0.4 dB. Polymer-filled etched beam splitters were also fabricated that give power transmission in 10% to 30% range when angles of incidence are around 30° and gap widths are from 0.3 to 0.5 mum. Using these components the bandstop and add/drop filters based on single ring resonator with circumference of down to 55 mum were first designed and demonstrated in GaAs/AlGaAs platform. Also the compact filters with integrated semiconductor optical amplifiers inside the ring resonator were designed and fabricated in InP/InGaAsP material system. In this platform the bandstop filters with circumference as low as 45 mum corresponding to a free spectral range in excess of 14 nm were demonstrated at 1.55 mum. These filters occupy an area of about 20 mum x 20 mum and have tunable transfer functions with tuning currents less than 2.5 mA.