We present the characterization of highly photorefractive Er3+/Yb3+-doped 75SiO2-25GeO2 planar waveguides, single mode at 1550 nm, deposited by radio-frequency-magnetron-sputtering (RFMS) technique. Details of the deposition process are reported. The material presents an intense absorption band (alpha approximately 10;3/10;4 cm;-1) in the UV region. Irradiations by a KrF excimer laser source at lambda = 248 nm have produced large positive (up to 310-3) refractive index changes, without the need of particular sensitization procedures. Direct measurements of UV photo-induced volume densification demonstrates that glass compaction accounts for large part of the refractive index change. Highly efficient photo-induced phase gratings have thus been fabricated in the waveguide.

A phase grating is produced in an iron-doped lithium niobate photorefractive crystal by two-beam holographic configuration. Digital holography is used to investigate the two-dimensional profile of index of refraction produced by the photorefractive process. The proposed technique gives a direct and quantitative two-dimensional profile of index of refraction in photorefractive structures, can monitor defects and can be used for in situ visualization during the photorefractive process.

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