Theoretical and experimental investigation of silicon nanowire waveguide displacement sensors

Abstract

Efforts towards integrated optical circuits have seen significant interest for combining microelectronics and photonics in order to bring compact device sizes and volume economics. Silicon nanowire waveguides and photonic crystals are among those heavily investigated. Photonic devices with embedded Nano/Microelectromechanical Systems (NEMS/MEMS) such as an optical add-drop multiplexer deploying relative motion of silicon waveguides, nanowire waveguide ring and microdisk resonators demonstrated as narrow-band filters, optical switches utilizing silicon nanowire waveguide couplers, and an optical waveguide modulator have been reported. Integrated photonic circuit devices with embedded NEMS/MEMS technology utilize either in-plane or out-of plane motion to accomplish their task. Characterization of such devices can be realized either under Scanning Electron Microscope (SEM) or optical microscopes. Ultimate device characterization, therefore, depends on the quality and evaluation accuracy of the series of images taken consecutively under the corresponding microscope at various actuation levels. Hence, employment of images for device motion characterization causes measurement errors from several tens to hundreds of nanometers during evaluation stage for SEM and optical microscope uses, respectively. Without proper characterization of devices where precise motion or distance in the nano/micro-system level is critical, full understanding of the studied concept, or proper operation or control of the system becomes impossible. In addition, they are usually only for testing purposes and cannot be integrated into the device level.