Response of the transmission spectrum of tapered optical fibres to the deposition of a nanostructured coating

Abstract

Nanostructured coatings have been deposited onto tapered optical fibres using the Langmuir–Blodgett technique. The response of the transmission spectrum of the tapered fibres to changes in thickness of the coating has been analysed. The effects observed are shown to be dependent on the diameter of the tapered region.

Optical Gas Sensor Fabrication Based on Porphyrin-Anchored Electrostatic Self-Assembly onto Tapered Optical Fibers

“…The detailed description of the fiber tapering procedure can be found elsewhere (Jarzebinska et al 2009). Briefly, a single mode silica optical fiber was tapered using the heat and pull technique.…”

“…When the tapered fiber is immersed into water, the wavelength of the channeled spectra undergoes a red shift along with a change in the amplitude of the optical spectrum due to increase of the refractive index (RI) of the surrounding medium from 1.00 (air) to 1.33 (water). The wavelength shift of the channeled spectrum is a result of a differential change in the propagation constants of the modes within the tapered region (Corres et al 2007;Jarzebinska et al 2009), while the reduction in amplitude is a result of the reduced confinement of the modes that accompanies immersion in water, which has a higher refractive index than that of air. Interestingly, the wavelength shifts (determined as an average value across the spectrum) of the spectral features are 28, 16, and 15 nm for the 9-, 10-, and 12-mm tapered optical fibers, respectively, suggesting that the fiber with thinner waist diameter possesses higher sensitivity to RI change.…”

“…The optical properties of the tapered fiber waveguide are influenced by the profile of the conical tapering sections, by the diameter of the taper waist and by the optical thickness of the surrounding medium. The proportion of the power in the evanescent field, and thus the interaction with the surrounding medium, increases with decreasing the diameter of the taper waist (Jarzebinska et al 2009). In the tapering section, the guided mode of the single mode fiber is converted into a mode of the waist.…”

“…In adiabatic tapers this is achieved without coupling to higher order modes. In non-adiabatic tapers the taper profile is such that a proportion of the light is coupled into higher order modes of the tapered section, which interfere to produce the channeled spectra reported for tapers of diameter of order 5 mm (Jarzebinska et al 2009;Corres et al 2008).…”

Applied optics to engineering photonics: a retrospective

“…To achieve this requires precise control of the thickness of the overlay deposited, provided by the LB technique, and modelling of the dispersion curves of the LPG with the overlay. Recently we have been investigating tapered optical fibers [139] (Fig. 49), as a means of accessing the evanescent field for chemical and gas sensing and combining the tapers with grating technology for high sensitivity sensing.…”