Characterization of sidewall Bragg gratings using optical low-coherence interferometry with a broadband source

In this work, we present fabrication and measurement of sidewall Bragg gratings in chalcogenide arsenic tri-sulfide (As2S3) on titanium-diffused lithium niobate (Ti:LiNbO3) channel waveguides. The transfer matrix method was used to analyze the temporal and spectral response of the sidewall gratings in the mid-infrared. The waveguide sidewall Bragg gratings were fabricated by electron-beam lithography (EBL), metal liftoff and subsequent reactive-ion etching (RIE). Insertion loss of the mid-infrared Ti:LiNbO3 optical waveguides were measured at ~2 dB and the propagation loss was estimated to be 0.45 dB/cm. Configuration of an optical low-coherence interferometer that is capable of characterizing the mid-infrared sidewall grating-based devices was experimentally implemented and preliminary results from fiber Bragg gratings are presented.