Nanophotonics in low cost applications

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The goals of the research are to investigate nanostructures for new or enhanced optical properties and build low cost biosensing applications around them. Of different nanostructures, nanowires and surface plasmons are of particular interest. Nanowires can confine photons and carriers in two dimensions while allowing them to propagate in the third. Surface plasmons are guided waves which can be resonantly guided on the surface of metal-dielectric boundary. We have developed structural colors using surface plasmonic two dimensional nano-gratings and shown that the colors are sensitive to refractive index of the material or changes to the surface. The goal of the Discovery project will be integrate our two platforms for building low cost photonics applications. The research will involve both fundamental studies and material characterizations and engineering designs for developing low cost applications.**Over the short term, we will investigate building low cost bio-chemical sensors integrating our chips with cell-phones. Three applications namely detection of pollutants and pathogens in water; detection of pathogens in food especially in meat processing to facilitate the food producers in Ontario; and detection of traces of explosives in environment will be considered. The main difference in these applications is the functionalization of the chips. Since the nanostructures change color vividly in presence of detectants, the sensing system will be built around cell-phones using the cameras for imaging and processors for analyzing. 2-dimensional assay of chips will be designed and built where each chip will be functionalized specifically to bind to one single detectant. The chips will be integrated with micro-fluidic channels and the targeted detectants will travel through these channels to the chips where capture and detection will occur. We will also see whether the silicon nanowire arrays can be used for sorting molecules of different sizes. In order to understand this, fundamental studies will be done at how water interacts and flows within two dimensional periodic nanostructures. These interactions will be studied using nuclear magnetic resonance measurements. To our knowledge, no such study has been carried. Other features of cell-phones like the GPS and the wireless connectivity will also be used in our sensing system. For example, for water pollution testing, the test data can be tagged with the geographical locations and the results sent to a server to create in-situ maps as testing is being done. One can also imagine a decentralized testing system where information of pathogens detected can be quickly distributed to the local population through online social portals. This could result in testing done by "people for the people". The low cost and small form factor of the sensors means that these could easily be distributed and networked through the wireless connectivity for detecting explosives. Setting up the devices for special events like marathons will be easy due to the portable nature. Inspired by the "tricorder" in Star-trek; our goal is to use the power of nanotechnology and the ubiquitous nature of cell-phones to make this fiction a reality. **Over the long term, we plan to investigate these nanostructures for their enhanced optical properties through experimental and theoretical means. Properties like holographic images for three dimensional displays; enhanced electric fields and optical nonlinearities for optical logic and terahertz generation will be investigated. We will also develop fabrication and etching methods for creating nanowire arrays on direct bandgap III-V materials like gallium arsenide. New simulation methods for optical and electrical properties of nanostructures will be investigated.