Cladding mode reorganization in high-refractive-index-coated long-period gratings: effects on the refractive-index sensitivity.
We theoretically and experimentally investigated the reorganization of cladding modes in high-refractive-index- (HRI-) coated long-period gratings (LPGs), focusing on the influence of refractive-index sensitivity. When azimuthally symmetric nanoscale HRI coatings are deposited along LPG devices, a significant modification of the distribution of cladding modes occurs, depending on the layers' features (refractive index and thickness) and on the external refractive index. In particular, if these parameters are properly chosen, a transition between cladding modes and overlay modes occurs. Numerical and experimental effects of the mode transition on the sensitivity of the surrounding refractive index are described.
Cusano
Andrea
A
Optoelectronic Division, Department of Engineering, University of Sannio, Benevento, Italy. a.cusano@unisannio.it
Iadicicco
Agostino
A
Pilla
Pierluigi
P
Contessa
Luigi
L
Campopiano
Stefania
S
Cutolo
Antonello
A
Giordano
Michele
M