Electrochemical driven self-holding optical actuator: from materials to device concepts

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In the framework of this proposal we will develop a novel self-holding electrochemically driven optical actuator. Our key goal is to evaluate promising materials used for the actuator and to show that our approach is compatible with silicon photonics. The purpose of the actuator is the control of light transmission on photonic chips. The actuation principle is based on mixed ionic-electronic conductor (MIEC) materials that cover selected areas of silicon waveguides. Light waves propagating through the wave guide are affected by near-field coupling to the MIEC material. As base material for the optical modulator we use the electrochromic materials V2O5 and WO3. Both lithium and hydrogen will be used as mobile ions for the intercalation of the MIEC material. The ion content of the MIEC material can be changed by electrochemical reactions. With this change in stoichiometry also the optical properties, i.e., the refractive index and the extinction coefficient and thus the intensity and phase of light waves propagating in the underlying waveguide will be modified. In order to prove the concept of using MIEC materials as optical actuators, solid-state multilayer systems will be fabricated by sputter deposition. The electrochemical performance of the multilayer stack enables to adjust the ion content of the MIEC material and thus its optical properties by the voltage/current applied. The optical modulation capability will be studied by integrating the actuator system on silicon photonic circuits. For this purpose, the multilayer stack will be deposited in well-defined areas of various silicon waveguide structures that were fabricated before by means of electron beam lithography in combination with reactive ion etching. The optical properties of the silicon waveguide-actuator system derived from our experiments are compared with simulations in order to obtain an actuator material system with optimized properties in terms of design and performance from the comparison between experiment and simulation after several iterations.