Asal, R., Rivers, P.E. and Rutt, H.N.
Optical properties and local structures of gallium lanthanum sulphide/oxide thin film for waveguide lasers
At Quantum Electronics Conference (QE13), United Kingdom.
08 - 11 Sep 1997.
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Rare earth doped glass waveguides have recently received considerable attention because of their potential in the realization of active waveguide devices. Such devices offer a possible means of incorporating sources and amplifiers into integrated optical circuits. We have used pulsed laser deposition technique to grow GALAS thin film waveguides in an oxygen atmosphere. The flow rates of the oxygen, and hence its partial pressure, were adjusted to vary the content of oxygen in the film. The base pressure was about 4 x 10 Torr and the total chamber pressure during the deposition was about 10m Torr.
In this presentation, we report the effect of oxygen on optical and structural properties of GLS thin film waveguides. Incorporation of oxygen into GLS results in a decrease in Urbach absorption and, hence the waveguide losses. A preliminary EXAFS result shows that the oxygen bonds to all three elements present and the system appears to be chemically ordered. Optical absorption measurements are also reported and the results discussed and correlated with the structural data.
We have also investigated the effect of annealing on the optical and structural properties of GLS thin film. The effect of the annealing is that the optical gap increases and the absorption edge shifts to higher energy. this may be due to the breakage of the homopolar bonds and formation of heteropolar bonds in GLS thin film network
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