Fano lines in the reflection spectrum of directly coupled systems of waveguides and cavities: measurements, modeling and manipulation of the Fano asymmetry

摘要

We measure and analyze reflection spectra of directly coupled systems ofwaveguides and cavities. The observed Fano lines offer insight in thereflection and coupling processes. Very different from side-coupled systems,the observed Fano line shape is not caused by the termini of the waveguide, butthe coupling process between the measurement device fiber and the waveguide.Our experimental results and analytical model show that the Fano parameter thatdescribes the Fano line shape is very sensitive to the coupling condition. Amovement of the fiber well below the Rayleigh range can lead to a drasticchange of the Fano line shape.