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

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 (n_f) for each environmental material (n_e) with a specific wavelength (λ_max) at which the highest sensitivity is achieved. Where the refractive indices n_f and n_e are wavelength dependent. For the leaky radiation microfiber sensor, the value of n_f less than and getting close to the value of n_e. 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 (S_θ) becomes very high with wavelength (λ_Sθmax) at which n_f ≈ n_e. Such as, core (BK7 glass) and environmental (styrene) at λ_max = 0.8 μm, the value of S_θ = 13759. In the weakly radiation, the value of n_f greater than the value of n_e. The sensitivity is evaluated by measurement the mode field radius (S_W) or the fiber core power (S_P). For core (BK7) and environmental (toluene) with core radius a = 1 μm, the sensitivity S_w = 2556 (μm/RIU) at λ = 1.75 μm and the sensitivity S_P = 22.3 P_i (power unit/RIU) at λ = 1.05 μm (P_i is the fiber input power). The numerical evaluation of leaky radiation angle (θ) and sensitivity (S_θ) 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.