Surface Plasmon Resonance-Based Sensing Utilizing Spatial Phase Modulation in an Imaging Interferometer

Abstract

Spatial phase modulation in an imaging interferometer is utilized in surface plasmon resonance (SPR) based sensing of liquid analytes. In the interferometer, a collimated light beam from a laser diode irradiating at 637.1 nm is passing through a polarizer and is reflected from a plasmonic structure of SF10/Cr/Au attached to a prism in the Kretschmann configuration. The beam passes through a combination of a Wollaston prism, a polarizer and a lens, and forms an interference pattern on a CCD sensor of a color camera. Interference patterns obtained for different liquid analytes are acquired and transferred to the computer for data processing. The sensing concept is based on the detection of a refractive index change, which is transformed via the SPR phenomenon into an interference fringe phase shift. By calculating the phase shift for the plasmonic structure of SF10/Cr/Au of known parameters we demonstrate that this technique can detect different weight concentrations of ethanol diluted in water, or equivalently, different changes in the refractive index. The sensitivity to the refractive index and the detection limit obtained are −278 rad/refractive-index-unit (RIU) and 3.6 × 10 − 6 RIU, respectively. The technique is demonstrated in experiments with the same liquid analytes as in the theory. Applying an original approach in retrieving the fringe phase shift, we revealed good agreement between experiment and theory, and the measured sensitivity to the refractive index and the detection limit reached −226 rad/RIU and 4.4 × 10 − 6 RIU, respectively. These results suggest that the SPR interferometer with the detection of a fringe phase shift is particularly useful in applications that require measuring refractive index changes with high sensitivity.

Efficient Optical Sensing Based on Phase Shift of Waves Supported by a One-Dimensional Photonic Crystal

“…The second method, the spatial-domain interferometric method, was described in detail in a previous paper [ 47 ] demonstrating measurement of changes in the RI of a liquid analyte. In that method we used the experimental set-up comprising a laser diode irradiating at wavelength 637.1 nm, launching optics, a gold coated SF10 glass plate (Accurion, Goettingen, Germany), a coupling prism (SF10 glass, Accurion, Goettingen, Germany), a Wollaston prism (WP05, Thorlabs, USA) and a CCD camera (PL-B952U, Pixelink, Ottawa, Canada).…”

One-Dimensional Photonic Crystal with a Defect Layer Utilized as an Optical Filter in Narrow Linewidth LED-Based Sources

“…To measure the visibility function V(∆l) for the first LED-based source, a Michelson interferometer shown in Figure 6 was used and the interferogram captured by a camera was processed for different path lengths ∆l. The processing of the interferogram includes smoothing and evaluation of the intensity, as illustrated in a previous paper [64], to obtain their extremal values and express the visibility. As an example, an interferogram composed of the spatial interference fringes with a visibility of 0.606 is shown in Figure 9a for the smallest path difference.…”

Design and Analysis of GO Coated High Sensitive Tunable SPR Sensor for OATR Spectroscopic Biosensing Applications

“…Using Y-Function Method (YFM) equation, Alabsi et al mathematically investigated the effect of variation of certain physical parameters on electronic features improving the CNTFET devices sensing performance [10]. The fundamental operating mechanism of SPR biosensors is to analyze variations in input incoming light and determine the changes in its characteristics at the output terminal, specifically, the fluctuation in frequency, amplitude, phase, wavelength, or polarization of light [11]. These sensors bypass the timeconsuming labeling process for molecule binding and offer real-time monitoring, label-free detection, and analysis of the analytes.…”