Surface Plasmon Resonance sensor showing enhanced sensitivity for CO2 detection in the mid-infrared range

We present the first optical sensor based on Surface Plasmon Resonance (SPR) operating in the mid-infrared range. The experimental setup is based on a Kretschmann geometry with Ti/Au layers deposited on a CaF2 prism where light excitation is provided by a Quantum Cascade Laser (QCL) source. Evidence of SPR is presented and the sensing capability of the system is demonstrated by using CO2 and N-2 mixtures as test samples. Due to the absorption of CO2 at this wavelength, it is shown that the sensitivity of this configuration is five times higher than a similar SPR sensor operating in the visible range of the spectrum. (C) 2008 Optical Society of America