Surface plasmon resonance optical cavity enhanced refractive index sensing

• Published in: Optics letters Vol. 38; no. 11; p. 1951
• Main Authors: Giorgini, A, Avino, S, Malara, P, Gagliardi, G, Casalino, M, Coppola, G, Iodice, M, Adam, P, Chadt, K, Homola, J, De Natale, P
• Format: Journal Article
• Language: English
• Published: United States 01.06.2013
• Subjects: Optical Phenomena; Surface Plasmon Resonance - methods; Time Factors
• ISSN: 1539-4794
• DOI: 10.1364/OL.38.001951

We report on a method for surface plasmon resonance (SPR) refractive index sensing based on direct time-domain measurements. An optical resonator is built around an SPR sensor, and its photon lifetime is measured as a function of loss induced by refractive index variations. The method does not rely on any spectroscopic analysis or direct intensity measurement. Time-domain measurements are practically immune to light intensity fluctuations and thus lead to high resolution. A proof of concept experiment is carried out in which a sensor response to liquid samples of different refractive indices is measured. A refractive index resolution of the current system, extrapolated from the reproducibility of cavity-decay time determinations over 133 s, is found to be about 10(-5) RIU. The possibility of long-term averaging suggests that measurements with a resolution better than 10(-7) RIU/√Hz are within reach.