Oblique incidence and polarization effects in coupled gratings.

Oblique incidence and polarization orientation of the input beam have dramatic effects on the spectral response of coupled dielectric waveguide gratings. Coupled gratings with small periodic perturbations can be described as a problem of two coupled resonances at strictly normal incidence, but we find that the device involves four coupled resonances when oblique incidence and polarization effects are included in the analysis. Very small deviations from normal incidence change qualitatively the spectral response and four peaks are observed, whereas only two peaks are present at normal incidence.

Differential toolbox to shape dispersion behavior in photonic crystal fibers.

We present an analytical procedure to compute the first derivatives of the propagation constants with respect to several structural parameters in photonic crystal fibers (PCFs). From them we can easily evaluate the same derivatives of other directly related magnitudes. The above derivatives provide the trend of the magnitude at issue, which allows us to take advantage of a gradient-based algorithm to shape the properties of the guiding structure.