High resolution integrated microfluidic Fabry-Perot refractometer in silicon

We present a high resolution, robust and low cost integrated refractometer for microfluidic systems. The device is made of two Bragg reflectors vertically etched in silicon to form an in-plane Fabry-Perot filter. Liquids are injected in the cavity through a microfluidic channel and the variation of the refractive index induces a shift of the resonance wavelength. A sensitivity of 920 nm/RIU (refractive index units) and a resolution of less than 10
^-3
are obtained and are in good agreement with optical simulations. This resolution is, to our knowledge, the lowest ever reported for an integrated microfluidic Fabry-Perot refractometer.