Photonic-Fluidic Integrated Microstructures for Sensor and Photonic Device Applications

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Photonic-Fluidic Integrated Microstructures for Sensor and Photonic Device Applications Claire L. Callender, Patrick Dumais, Christopher J. Ledderhof, and Julian P. Noad Communications Research Centre, Ottawa, ON, K2H 8S2, Canada

ABSTRACT The design, fabrication and characterization of liquid-filled microchannels embedded in silica layers and integrated with optical waveguides for applications in on-chip sensors and novel photonic devices are presented. These integrated microstructures are formed using plasmaenhanced chemical vapor deposition (PECVD), photolithography and reactive ion etching (RIE). Surface accessible fluid introduction ports have been developed, and microfluidic circuits including bends, T-junctions and splitters are demonstrated. Coupling of light from integrated solid silica waveguides via directional coupling or direct end-fire coupling into fluid filled channels has been achieved on-chip, and optical losses assessed experimentally and theoretically. Optimization of the microstructures for sensor applications and for novel photonic devices based on nonlinear and other optical properties of fluids in integrated liquid waveguide segments is discussed. INTRODUCTION Integrated microstructures in which light can interact with nanoscale liquid samples have many applications in chemical and biological sensors. The integration of fluid-filled microstructures with lightguiding components on a wafer can also provide novel photonic device architectures for exploiting the unique properties of fluids or nanoparticle suspensions for applications in optical communications. Waveguides integrated with microfluidic channels have been previously demonstrated using a variety of materials [1-7]. Typically, open top channels are formed alongside or perpendicular to optical waveguides and a bonding process is required to seal the structures. These methods often require multi-step processes, and the top sealing of the open channels can present particular challenges. Femtosecond laser machining has recently opened up possibilities for more complex 3D architectures of microchannels, without the need for top sealing, although full integration with optical waveguides using this method is still under development [8,9]. We have previously demonstrated the controlled fabrication of embedded microchannels in silica glass layers [10]. In this paper we demonstrate more complex photonic-fluidic microstructures based on these microchannels. Key functionalities such as on-chip fluid introduction, microfluidic circuitry and coupling of light between solid and liquid waveguide segments are presented. These integrated microstructures are formed using a combination of plasma-enhanced chemical vapor deposition (PECVD), photolithography, reactive ion etching (RIE) and a final reflow anneal. This approach utilizes processes and materials already in use to fabricate optical devices in silica and requires no additional steps for the formation of the microchannels. It is compatible with large wafer processing, offering potentia