Fabrication and characterization of rugate structures composed of SiO_(2) and Nb_(2)O_(5)

Gradient index layers and rugate structures were fabricated on a Leybold Syrus pro deposition system by plasma-assisted coevaporation of the low index material silica and the high index material niobium pentoxide.To obtain information about the compositional profiles of the produced layers,cross sectional transmission electron microscopy was used in assistance to deposition rate data recorded by two independent crystal monitors during the film preparation.The depth dependent concentration profiles were transformed to refractive index gradients by means of effective medium approximation.Based on the refractive index gradients the corresponding samples`transmission and reflection spectra could be calculated by utilizing matrix formalism.The relevance of the established refractive index profiles could be verified by comparison of the calculated spectra with the measured ones.