Development of Efficient Si-nanocrystal-sensitized optical waveguide amplifiers

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Er doped SiO_2 films containing Si nanocrystals as sensitizers have been investigated for an application to an efficient optical-amplifier. We demonstrate an optical-amplifier gain of 991cm^<-1> measured by the VSL (variable strip length) method at a wavelength of 1.55 μm using a slab waveguide. The amplification in the VSL measurement is observed within irradiation length of 60 μm in the slab waveguide. It has been found that the silicon-nanocrystals size (that is controlled by the annealing temperature) is very important to decrease the waveguide loss caused by excitons generated in the silicon nanocrystals. Core films containing silicon nanocrystals whose diameter is less than 2.7 nm show positive gain (that is amplification), because the above mentioned waveguide-loss is low. Sputtering and microfabrication processes to develop the optical amplifiers are deposition and RIE (reactive ion etching) of core patterns. A uniform core-film (4cmx8cm area) has been achieved on a 4 inch silicon wafer with a uniformity of ± 10 % in the photoluminescence intensity and the film thickness. 6 μm deep patterns in silica films have been fabricated using RIE, which can be used to fabricate the optical amplifiers. If the practical planar waveguide amplifier is realized at the wavelength of 1.55 μm used in optical telecommunication networks, a variety of novel photonic devices can be developed, because a new functionality is added to passive silica-based waveguide components.