Reflection and transmission calculations in a multilayer structure with coherent, incoherent, and partially coherent interference, using the transmission line method.

A generalized transmission line method (TLM) that provides reflection and transmission calculations for a multilayer dielectric structure with coherent, partial coherent, and incoherent layers is presented. The method is deployed on two different application fields. The first application of the method concerns the thickness measurement of the individual layers of an organic light-emitting diode. By using a fitting approach between experimental spectral reflectance measurements and the corresponding TLM calculations, it is shown that the thickness of the films can be estimated. The second application of the TLM concerns the calculation of the external quantum efficiency of an organic photovoltaic with partially coherent rough interfaces between the layers. Numerical results regarding the short circuit photocurrent for different layer thicknesses and rough interfaces are provided and the performance impact of the rough interface is discussed in detail.

Fabrication of high-reflectivity superimposed multiple-fiber Bragg gratings with unequal wavelength spacing.

We report the inscription of as many as 10 superimposed Bragg gratings of high reflectivity in a 25-mm segment of fiber. Using hydrogenated boron codoped and germanosilicate fibers, we inscribed 10 superimposed gratings with reflectivities above 80% and 6 superimposed gratings with reflectivities above 98%, respectively. The superimposed gratings had unequal wavelength spacing and were written over a 20-nm wavelength span in the region of 1530 nm. The inscription of each new grating caused an increase in the FWHM linewidth of the existing gratings, while their reflectivity was unaffected.