Plasmons based optical-fiber biosensors created from gold coating tilted Bragg gratings have been demonstrated.
Plasmon resonances in the transmission are used to detect the banding of single stranded DNA (aptamer) and the further
banding of target DNA (matched one).
The generation of surface plasmon resonances (SPRs) in gold-coated weakly tilted fiber Bragg gratings (TFBGs)
strongly depends on the state of polarization of the core guided-light. Recently, it was demonstrated that rotating the
linear state of polarization of the guided light by 90° with respect to the grating planes allows to turn the SPR on and off.
In this paper, we demonstrate that this strong polarization dependence can be advantageously used to demodulate the
TFBG amplitude spectrum and retrieve the SPR shift induced by a change of the surrounding refractive index. The
correlation between two amplitude spectra recorded with two particular orthogonally polarized light states yields a new
refractive index measurement method accurate to ~2 10-5.
This paper presents a Surface Plasmon Resonance (SPR) fiber sensor capable of monitoring the deposition of thin
nm-scale polymer films. The sensor was used for in situ monitoring of the adsorption of 30 mono-layers of oppositely
charged polyelectrolytes with an overall thickness of each individual monolayer less than 0.55 nm. The in situ
monitoring of the formation of multi-layer structures was implemented through the excitation of SPR on the surface of a
gold-coated fiber with a Tilted Fiber Bragg Grating (TFBG) written in the core of the optical fiber.
A new Surface Plasmon Resonance (SPR) sensor design is proposed and fabricated based on an optical fiber with a photo-written Tilted Fiber Bragg Grating (TFBG) and a thin gold deposited layer. The TFBG allows the transfer of light from the core mode into a multitude of cladding modes, each wavelength corresponding to a different incidence angle. The most pronounced SPR effect was obtained for a gold thickness of 20 nm, however every tested thickness showed SPR at a certain level. To characterize the uniformity of gold films, the coated fiber were imaged using Atomic Force Microscopy (AFM) and showed a high level of graininess, as expected from such thin layers. Scanning Electron Microscope (SEM) images were used to characterize the quality of the gold coating before and after experiments. Despite the high non-uniformity and graininess of gold coating, the angular spread of SPR is as narrow as expected from theory. The sensitivity obtained reaches 454 nm per refractive index unit.
In this paper we consider linguistic model as an algebraic model and restrict our consideration to the semantics only. The concept allows “natural-like” language to be used by human-teacher to describe for machine the way of the problem solving, which is based on human’s knowledge and experience. Such imprecision words as “big”, “very big”, “not very big”, etc can be used for human’s knowledge representation. Technically, the problem is to match metric scale, used by the technical device, with the linguistic scale, intuitively formed by the person. We develop an algebraic description of 4-f Fourier-holography setup by using triangular norms based approach. In the model we use the Fourier-duality of the t-norms and t-conorms, which is implemented by 4-f Fourier-holography setup. We demonstrate the setup is described adequately by De-Morgan’s law for involution. Fourier-duality of the t-norms and t-conorms leads to fuzzy-valued logic. We consider General Modus Ponens rule implementation to define the semantical operators, which are adequate to the setup. We consider scales, formed in both +1 and -1 orders of diffraction. We use representation of linguistic labels by fuzzy numbers to form the scale and discuss the dependence of the scale grading on the holographic recording medium operator. To implement reasoning with multi-parametric input variable we use Lorentz function to approximate linguistic labels. We use an example of medical diagnostics for experimental illustration of reasoning on the linguistic scale.