The change in the optical properties of VO2 across its insulator to metal to transition could give rise to novel photonic devices with beyond state-of-the art performance in terms of footprint, power consumption and speed operation. However, the final performance strongly depends on the control and efficiency of the phase transition in the VO2. For electro-optical applications, such control and efficiency is highly dependent on the electrode configuration. In this work, the influence of the electrodes is experimentally analyzed and an alternative approach is proposed to switch the VO2 to the metallic state by minimizing the electrical power consumption. The electro-optical performance of the proposed short-circuited electrode is also experimentally demonstrated. An extinction ratio of 12 dB is achieved with a 20μm long hybrid VO2/Si waveguide with an electrical power of only 11mW. The power consumption could be further reduced by decreasing the distance between the electrode and the silicon waveguide, which in this work has been fixed to 1.5μm, without affecting the optical losses.
A novel method to significantly decrease power consumption in a silicon switch based on an asymmetric Mach-Zehnder interferometer (MZI) structure is proposed and experimentally demonstrated. A radical power consumption reduction up to 50% is achieved for switching digital data at bit rates from 10 to 30Gbps with respect to a conventional switch based on a symmetric MZI. Furthermore, the broadband performance of the proposed silicon MZI comb switch is also demonstrated by transmitting a 120 Gbps DWDM data stream.
Silicon-photonic 2×2 electro-optical switching elements and modulators based on the carrier depletion mechanism using both dual-resonator and MZI layout configurations have been developed. The passive photonic structures were developed and optimized using a fast design-fabrication-characterization cycle. The main objective is to deliver smallfootprint, low-loss and low-energy silicon photonic electro-optical switching elements and modulators equipped with standard input-output grating couplers and radio-frequency electrical contact tips to allow their characterization in highspeed probe-station setups. The insertion losses, crosstalk, power consumption and BER performance will be addressed for each electro-optical structure. The fabrication steps, including low loss waveguide patterning, pn junction and low resistive ohmic contact formation have been optimized to produce high performance devices with relaxed fabrication tolerances, employing both optical and electron-beam lithography.