Evanescent-field sensor using selectively excited modesin step-index fibers

摘要

High-order skew modes will be excited in multimode step-index fibers using special excitation conditions. As a result, light with an angle of incidence larger than the maximum angle for meridional modes given by the numerical aperture of the fiber can be coupled into a fiber. Combining the selective mode-excitation with new powerful broadband light-sources, the spectral light-guidance of such skew modes in different optical fibers will be described in detail. Results of the proposed system in context of different light-sources will be discussed. A new evanescent sensor approach based on controlled coupling of skew modes will be introduced. Finally, first steps to construct such sensors for medical and analytical applications will be presented.