Narrow Results

In this paper, the spectral response of uniform and apodized (Gaussian, hyperbolic tangent, apod1, sine, and raised sine) FBGs is analyzed for sensing applications. The reflectivity at Bragg wavelength as well as for sidelobes was assessed as a function of grating length and apodization profiles. The FBG strain and temperature sensors were simulated and a linear response between applied strain or temperature and the wavelength shift is observed. The results indicate that the sensitivity of the sensor is found to be affected both by the grating length and apodization type. The typical strain and thermal sensitivity values are 1.223 pm/$\mu 𝜀$ and 13.60 pm/${}^{\circ }$C, respectively. The results suggest that Gaussian, sine, and raised sine profiles have lower sidelobe strength and reliable sensitivities. The key finding from this study specifies that the ideal grating length must be preferably between 5 and 10 mm for a good sensing behavior.

Oblique light propagation through a chiral photonic crystal (PC) layer with gradient parameters of modulation is considered. The problem is solved by Ambartsumian's layer addition modified method. It is shown that suppressing of diffraction oscillations near the photonic band gap (PBG) is possible at certain conditions. Thus, at certain conditions, the spectra for the finite PC layer is the same as that for the half space.