Optical frequency tuning by laser-irradiation in silica-based March-Zehnder-type multi/demultiplexers

Optical frequency tuning due to photoinduced refractive-index changes is described in Mach-Zehnder interferometer-type frequency division multiplexers (FDMs) which are composed of GeO/sub 2-/silica-based waveguides on Si substrates. A maximum refractive-index change of about 4*10/sup -5/ at 1.3 mu m is obtained at an Ar/sup +/ laser power of 20 W and an irradiation time of 1 h. This leads to frequency tuning of more than half a period in FDM with a free spectral range of 25 GHz. In addition, the annealing effects on the refractive-index change are investigated.<
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