Integrated silicon optical sensors based on hollow core waveguide

In this work we show that integrated silicon hollow core AntiResonant Reflecting Optical Waveguide (ARROW) can be used as a basic tool for the realization of optical sensors. ARROW waveguides, with hollow core, permit to confine the light in a low refractive index liquid core, by means of two cladding layers designed to form a high reflectivity Fabry- Perot antiresonant cavity. This arrangement allows to realize microchannels that can simultaneously act as microfluidic networks and optical waveguides with a strong advantage in the integration and with an increased interaction efficiency between the light and the liquid substance that can be very useful in sensing applications (fluorescence, absorption spectroscopy, etc.). Another ARROW waveguides advantage is the ability to tailor the wavelength response of the device. In fact, the waveguide propagation losses strongly depend on the change of the resonant condition inside the interference cladding. In this paper we report three sensing applications of hollow core ARROW waveguide. A long path absorbance cell for colorimetric protein assay, a high sensitivity integrated refractometer and a micro flow cytometer for cell/particles analysis. The proposed devices have been realized in standard silicon technology by using two silicon wafers bonded together.