Active optical waveguides based on Er- and Er/Yb-doped silicate glasses

The growing interest for the use of integrated optical (IO) amplifiers in optical fibre telecom systems has led to depth search for ever better rare-earth-doped glassy materials. In the present paper we report some properties of a set of Er3+/Yb3+-doped soda-lime silicate glasses. Several batches were prepared, all with the same base mol% composition (73SiO2–1Al2O3–0.4P2O5–14Na2O–0.6K2O–11CaO) containing Er2O3 (0.32–0.48%) and Yb2O3 (0.63 and 0.78%). The resulting glasses were cut into rectangular plates about 1 mm thick, and one surface was optically polished. Planar and channel waveguides were subsequently obtained in these plates by Ag+–Na+ ion-exchange. Spectroscopic analysis showed that the fluorescence emission peak for all the samples was observed at 1532±1 nm, with a full-width at half-maximum equal to 19 nm. Measurements of the lifetime of the metastable state of Er3+ were performed upon excitation by laser pumps at 514.5 and 980 nm, and times of the order of 7 ms were measured in most samples. The intensity of the up-conversion fluorescence was less in Er3+/Yb3+ co-doped glasses than in Er3+-doped ones. Preliminary measurements of the transmitted power at 1540 nm in channel waveguides made in the glass doped with nominal 0.32 mol% of Er2O3 have confirmed their potential of achieving optical gain; in fact, a signal enhancement (internal gain) >1 dB/cm was measured with more than 1 mW input signal.