Modeling of waveguide UV-induced Bragg gratings with arbitrary apodization function: Tools for designing high-performance related devices

We present a semi-analytical modeling suitable for the investigation of the spectral characteristics of UV-waveguide Bragg gratings (UV-WBGs) having arbitrary apodization function and extending both in the film layer and in the overlayer. The modeling is based on a proper combination of coupled mode theory and transfer matrix formalism and provides a powerful tool for designing and simulation of complex UV-grating based structures. The results of a detailed investigation of UV-WBGs in doped silica based channel optical waveguides are presented and critical issues for upgrading the performances of related device are discussed. Validation of the modeling is provided by means of an extensive comparison between theoretical and experimental results relevant to UV-WBGs realized in phosphorous (P)- and boron (B)-doped silica based waveguides.     

Identification of the IR frequencies of the interstitial carbon atom in some M6C (M = Fe,Ru) carbonyl clusters by13 C-enrichment

¹³C-enriched carbido carbonyl clusters of the type [M₆C(CO) _n ] ^z? (M=Fe,n=16,z=2; M=Ru,n=16 ifz=2 andn=17 ifz=0) have been prepared and their IR spectra observed in the 900?600 cm^?1 region; the band shifts occurring upon¹³ C substitution enable the assignment to the stretching modes of the interstitial C atom. Band patterns reflect the symmetry of the M₆C core, but the frequencies seem dependent on other molecular features.