Silicon micromachined photonic crystal integrated in an opto-fluidic microsystem

In this work, fabrication and testing of closed-loop opto-fluidic microsystems integrating both optical and fluidic functionalities on the same chip are reported. The microsystems consisted of an electrochemically micromachined silicon substrate, on which high-order vertical silicon/air one dimensional photonic crystals (1D PhCs) were integrated together with fluidic microchannels, bonded to a glass cover, the latter provided with inlet/outlet holes for liquid injection/extraction in/out the PhCs air gaps. An experimental characterization was performed by pumping different liquids (water, ethanol, isopropanol) through the opto-fluidic microsystem and by measuring the reflectivity spectrum in the wavelength range 1.0 - 1.7 μm (at normal incidence) with an inplane fiber optic setup. Experimental results, which well agreed with theoretical predictions, demonstrated the high sensitivity of the opto-fluidic microsystem in measuring small refractive index changes, which was estimated to be 1049 nm/RIU.