Sensor with increased sensitivity based on enhanced optical transmission in the infrared

Using enhanced optical transmission (EOT) through periodic nanoslits in thin metal films we demonstrate sensing in water with highly enhanced sensitivity in the infrared range for the first time. This is explained as a result of the enhancement in the penetration depth in the analyte thus increasing the interaction volume which in turn increases the sensitivity and allows for sensing of large bio-entities. The penetration depth enhancement in the EOT case is found to be larger than the corresponding enhancement factor in the Kretschmann configuration.