Markus Hautakorpi

Surface-plasmon-resonance sensor based on three-hole microstructured optical fiber

We propose a novel surface-plasmon-resonance sensor design based on coating the holes of a three-hole microstructured optical fiber with a low-index dielectric layer on top of which a gold layer is deposited. The use of all three fiber holes and their relatively large size should facilitate the fabrication of the inclusions and the infiltration of the analyte. Our numerical results indicate that the optical loss of the Gaussian guided mode can be made very small by tuning the thickness of the dielectric layer and that the refractive-index resolution for aqueous analytes is 1x 10(-4).

Modal analysis of M-type-dielectric-profile optical fibers in the weakly guiding approximation

We study the applicability of the weakly guiding approximation (WGA) to the modal analysis of an M-type optical fiber in which a ring-shaped core lies between two uniform cladding layers. Besides being dependent on the refractive indices, the accuracy of the approximation is shown to be substantially affected by the transverse dimensions of the core. The accuracy is characterized by calculating an overlap integral between the exact and WGA-approximated modal fields. Fibers that have an inner cladding similar to the outer cladding, or similar to vacuum, are considered in detail. The feasibility of the WGA in determining the fiber parameters for single-mode guidance is also discussed.

Comprehensive numerical analysis of a surface-plasmon-resonance sensor based on an H-shaped optical fiber

We present and numerically characterize a surface-plasmon-resonance sensor based on an H-shaped optical fiber. In our design, the two U-shaped grooves of the H-fiber are first coated with a thin gold layer and then covered by a uniform titanium dioxide layer to facilitate spectral tuning of the device. A finite element method analysis of the sensor indicates that a refractive-index resolution of up to 5 · 10(3) nm/RIU can be obtained.

Modal analysis of the self-imaging phenomenon in optical fibers with an annular core

We investigate the occurrence of self-images, or Talbot images, in a spatially multimode field that propagates along an optical fiber whose core has an annular-shaped cross section. By use of full-vectorial modal analysis, we study the effect of the transverse fiber dimensions on the self-imaging properties. According to our analysis, good self-images can be expected when the fiber core is thin and the modes are far from their cutoffs. However, as the core diameter is made larger to increase the number of modes available in the imaging, the general self-imaging properties tend to deteriorate.

Surface-plasmon-resonance sensor based on H-shaped optical fibre

We propose and theoretically study a novel surface-plasmon-resonance sensor based on an H-shaped, elliptical-core optical fibre. The two grooves of the H-fibre are coated with a thin, uniform metal layer that in turn is covered with a high-index dielectric layer to allow broad spectral tunability. The sensor maintains linear polarization and facilitates effortless splicing. Electromagnetic mode analysis indicates a sensitivity of 1800 nm/RIU (refractive-index unit) for aqueous analytes.

Rotational frequency shifts in partially coherent optical fields

We study the frequency shifts taking place when a random, stationary optical field rotates with respect to an observer. The field is expanded in terms of fully coherent Laguerre-Gaussian basis modes, for which the rotational frequency shifts have been studied previously. We demonstrate the formalism by considering the spectrum of a Gaussian Schell-model field, and show that for a spatially highly incoherent field, significant spectral changes can be expected.

Surface-plasmon-resonance sensor based on suspended-core microstructured optical fiber

We propose a novel surface-plasmon-resonance sensor design based on coating the hole surfaces of a suspended-core optical fiber with low-index dielectric layer on top of which gold layer is deposited.

Novel sensor concept based on microstructured optical fiber with metal inclusions

We propose surface-plasmon-resonance sensor design based on suspended-core optical fiber with gold inclusions. Auxiliary dielectric layer is considered to provide tunable loss level and single-mode operation.

Photonic bandgaps in photonic crystal fibers with coated high-index inclusions

We investigate the photonic bandgaps in photonic crystal fibers coated with cylindrical high-index inclusions. Besides numerical modeling, we are studying the feasibility of the atomic layer deposition technique for producing the inclusions.