Core mode

As aforementioned, the spectral characteristics of LPGs are determined by the coupling between the fundamental guided core mode and the co-propagating cladding modes when the core propagating light encounters a periodic perturbation... 

The presence of the HRI coating induces an increase in the effective refractive index of the cladding modes and thus a decrease in the resonance wavelengths. In addition, the spatial shift of the cladding mode field profile toward the HRI overlay promotes a decrease of the overlap integral with the core mode and so of the transmission loss peak. The subsequent evaporation of the solvent molecules from the nano-cavities results in a reduction of its refractive index. This explains the partial... 

Koyamada, Y., Numerical analysis of core mode to radiation mode coupling in long period fiber gratings, IEEE Photon. Technol. Lett. 2001, 13, 308 310... 

Core mismatch between two fiber segments can also cause part of the core-mode light coupled into the cladding modes. Based on this mechanism, CCMI sensors... 

Fig. 1. The autocorrelation function C(t) = (U (O)l I (i) is shown for a wavepacket initially prepared on the upper diabatic surface [7]. Panels (a) and (b) C(t) for the four core modes calculated by the standard MCTDH method for the model Hamiltonian Hy of Eq. (9), shown on different scales in the two panels. Panel (c) G-MCTDH calculation (bold line) as compared with standard MCTDH calculation (dotted line) for the composite system with four core modes (combined into two 2-dimensional particles

Global Rate Equations (Shrinking-core Mode ... 

In Fig. 6,1 present an example of a solid-core PBG fiber-based SPR sensor. By choosing the fiber core size to be small, one can considerably reduce the effective refractive index of the core mode. This enables plasmonic excitation at longer wavelengths in the near-IR. In Fig. 6a, I show cross section of a small-core Bragg fiber-based sensor, as well as energy flux distributions in the HE core mode and plasmon mode. Reflector layer thicknesses are chosen according to (15), where Ic = 760 nm, = 1.42, = 1.6, and Hcs = 1.39, thus resulting in = 654 nm,... 

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