Loss Measurements in Silicon Core Optical Waveguides
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Silicon core fibers have, because of their non-linear optical properties and transmission in the IR, recently been the focus of several different research groups. At NTNU, a new method for production of silicon fibers has been suggested, using an alkaline oxide interface modifier between the core and the cladding in the silicon fibers.In this project, to measure the losses in these new silicon core optical fibers, a set-up is developed based on the scattering of light from the waveguide. The method is found to give accurate and reproducible results for wavegudies with high losses (> 1 dB/cm), where scattering is an important loss mechanism and losses are uniform. Compared to the more common cut-back method used for loss measurements, the scatter method is non-destructive and give additional information about the distribution of losses.Losses measured in the silicon fibers range from about 3 dB/cm to over 50 dB/cm. Charactarization by different methods suggest that surface scattering is an important loss mechanism in the new fibers. Polycrystallinity and impurities in may also be important contributors to the losses.