Effect of induced inner curvature on refractive index sensitivity in internally tilted long-period gratings

Abstract

A new complete analysis of the effect of induced inner curvature on refractive index (RI) sensitivity in internally tilted long-period gratings (ITLPGs) is presented. The responses in terms of RI sensitivity of a standard LPG and different ITLPGs with curvature values between 15 and 19 m^-1 were compared. The analysis suggests first, that the larger the induced curvature, the greater the RI sensitivity; and second, that the RI sensitivity exponentially increases with both the curvature and cladding mode order. RI sensitivity greater than 100 nm RIU^-1 can be attained with curvature greater than 25 m^-1 for LP₀₆ mode. Conversely, the temperature sensitivity of ITLPGs is comparable to standard LPGs for the considered cladding mode order.

D-shape polymer optical fibres for surface plasmon resonance sensing

“…3 we present the resonance curves obtained for the three sensors for the refractive index of glycerol solution n s = 1.332 and different bending radii R. The resonance occurs at around 600 nm for all the investigated sensors and it shifts toward longer wavelengths in response to a curvature in− crease. Similar effect was observed for internally tilted long− −period gratings [29]. We clearly see in Fig.…”

Manufacturing and Spectral Features of Different Types of Long Period Fiber Gratings: Phase-Shifted, Turn-Around Point, Internally Tilted, and Pseudo-Random

“…This structure essentially mimics the effect of an external bending of the optical fiber, while a straight configuration of the fiber is maintained. It was proved that the sensitivity to the surrounding RI changes of internally-tilted LPFGs is higher than standard LPFGs, considering the same cladding mode order, and this effect increases when greater tilt angles are realized [26]. Lastly, it is worth pointing out that chirped LPFGs, which represent another class of fiber gratings where the grating period increases monotonically according to a chirp value, can be also manufactured with the proposed experimental setup.…”

“…Moreover, this effect becomes larger when the realized inner curvature C (C = 1/R, R is the radius of curvature) of the grating planes increases as well (or R decreases) [25,26]. It was experimentally demonstrated that the previous effect follows a non-linear exponential behavior [26].…”

“…The main advantage of this configuration is that the intrinsic RI sensitivity of each cladding mode increases, while the temperature sensitivity remains almost constant [25]. Moreover, this effect becomes larger when the realized inner curvature C (C = 1/R, R is the radius of curvature) of the grating planes increases as well (or R decreases) [25,26]. It was experimentally demonstrated that the previous effect follows a non-linear exponential behavior [26].…”

A sensitive tapered-fiber optic biosensor for the label-free detection of organophosphate pesticides

“…The results were corrected by taking into account the material dispersion of the solution RIs. In fact, in the case of water, the difference in RI reaches roughly 0.014 RIU and cannot be neglected when precise measurements are discussed and compared [37].…”