Sensitive liquid refractive index sensors using tapered optical fiber tips

Abstract

An optical fiber sensor based on the change of optical confinement in a subwavelength tip is presented. The optical spot is substantially increased when the environmental refractive index (RI) increases from 1.3 to 1.4. By measuring the intensity of low angular spectral components, an intensity sensitivity up to 8000% per RI unit is achieved. The fiber tip sensors take advantage of the small detection volume and real-time responses. We demonstrate the application of the nanofiber sensors for measuring concentrations of acids and evaporation rates of aqueous mixtures.

Engineering of a Ge–Te–Se glass fibre evanescent wave spectroscopic (FEWS) mid-IR chemical sensor for the analysis of food and pharmaceutical products

“…Further enhancement in the concentration sensitivity in unclad fibre/waveguide design was demonstrated using tapered and nano-fibres [17][18][19][20][21], allowing subppm concentration analysis. However, for high sensitivity (10 3 -10 5 ) and signal-to-noise ratio, the spectral range between 2 and 16 m appears ideal for a range of spectroscopic characterization using a suitable transparent medium, which must be a non-silica host due to the strong multiphonon absorption in the core-clad silica and ARROW structures.…”

Recent Developments in Micro-Structured Fiber Optic Sensors

“…The advantages of chemical etching include reproducibility, reliability, surface smoothness, and good symmetry. Various etching methods such as hydrofluoric (HF) acid static A typical fiber tip structure using the chemical etching method is proposed in [197]. The fiber tip was produced by firstly removing the fiber jacket and immersing the fiber in a melting polymer to form a protective layer with a tapered shape.…”

“…Experiments were conducted with a demonstration of continuous vibration measurement with frequency range of 5 Hz-10 kHz. [197].…”

Micro/nanofiber optical sensors

“…More recently, Tai et al [43] presented a RI sensor based on the change of optical confinement in a subwavelength tip ( Fig.1 (b)). The optical spot was substantially increased when the environmental RI increased from 1.3 to 1.4.…”