A surface-plasmon-based optical sensor using acousto-optics

Abstract

In this work the construction of a wavelength-tunable optical sensor with a fixed angle of incidence, incorporating an acousto-optic tunable filter (AOTF) is described. The AOTF is used to control the wavelength of a ppolarized light beam incident on a gold-coated diffraction grating. A surface plasmon resonance (SPR) is observed as a deep minimum in the intensity of the reflected beam as the incident wavelength is incremented. Slight modification of this arrangement allows measurement of the differential reflectivity profile with respect to wavelength. By locking to the zero differential corresponding to the SPR reflectivity minimum and monitoring the AOTF drive frequency (typically about 100 MHz) the SPR minimum position is then measured to within a precision of 0.0005 nm. The sensitivity of this system was found to be equal to a change in the refractive index of a gas of 1 x concentration of 0.01 ppm NO2 in N2 was detected.Furthermore, by adding a chemically active overlayer to the system a

Surface-plasmon voltammetry using a gold grating

“…The differential-detection system used here allows the resonant optical wavelength to be monitored to a precision of 0.0005nm. 44 This is equivalent to a sensitivity of ~8×10 −4 of a sulphate ion monolayer. By optimising the grating pitch and the refractive index contrast between the electro-deposited material and the bulk electrolyte it should be possible to improve this sensitivity by at least an order of magnitude.…”

“…SPR excitation is observed as a minimum in the reflectivity at ~660 nm. 44 electrode. Hydrogen evolution occurs on the positive sweep up to about -400 mV after which double-layer charging occurs.…”

“…44 This detection system allows the position of the SPR, in wavelength, to be continuously monitored as cyclic voltammetry is performed. 45 …”

Surface Plasmon Resonance Tunability in Au−VO2 Thermochromic Nano-composites

“…Recently, within the expansion of the multidisciplinary field of Nanosciences, this surface plasmon resonance effect, involving noble metals, is frequently used for biosensing to monitor binding and changes in biological molecules (3)(4) and to improve immunolabeling (5). Likewise, it is used for ultra-low doses gas sensing and bio-hazardous gases identification (6) as well as high-sensitivity electrochemical studies (7). In the standard Kretchmann geometry, this surface plasmon resonance is used to monitor with a high accuracy the optical parameters of Langmuir-Blodgett synthesized thin films (8)(9).…”

Improvement for sensitivity of biosensor with total internal reflection imaging ellipsometry (TIRIE)

“…The total internal reflection ellipsometry (TIRE or surface plasmon enhanced ellipsometry) biosensor is developed from the conventional SPR biosensor, based on the ellipsometer operating in the total internal-reflection mode [12,13]. The polarization control of the ellipsometry in the SPR biosensor is applied for the biomolecule detection [7,[14][15][16]. Its sensitivity is shown to be 10 times higher than that of the conventional SPR biosensor [13], however, highthroughput is a difficult part in design.…”