Sensitivity maximization of leaky and weaky radiation micro/nano fiber sensors

Abstract

The maximization of sensitivities of both leaky and weakly radiation micro/nano fiber sensors based on the refractive index occurred by choose the suitable core material (nf) for each environmental material (ne) with a specific wavelength (λmax) at which the highest sensitivity is achieved. Where the refractive indices nf and ne are wavelength dependent. For the leaky radiation microfiber sensor, the value of nf less than and getting close to the value of ne. The core material can be available with environmental material at some wavelengths and not suitable with other wavelengths. Such as, the core (BK7 glass) unsuitable with styrene within band rejected wavelengths (λ = 0.783–1.033) from the transmittance range of styrene (λ = 0.4386–1.052 μm). The radiation angle sensitivity (Sθ) becomes very high with wavelength (λSθmax) at which nf ≈ ne. Such as, core (BK7 glass) and environmental (styrene) at λmax = 0.8 μm, the value of Sθ = 13759. In the weakly radiation, the value of nf greater than the value of ne. The sensitivity is evaluated by measurement the mode field radius (SW) or the fiber core power (SP). For core (BK7) and environmental (toluene) with core radius a = 1 μm, the sensitivity Sw = 2556 (μm/RIU) at λ = 1.75 μm and the sensitivity SP = 22.3 Pi (power unit/RIU) at λ = 1.05 μm (Pi is the fiber input power). The numerical evaluation of leaky radiation angle (θ) and sensitivity (Sθ) are excellent if they are compared with the published experimental measured results. The leaky and weakly sensors has potential applications due to their high sensitivity and simple constructions.