Design, Realization and Analysis of an Apodised, Film-Loaded Acousto-Optic Tunable Filter

The design and realisation of a SiO(2) film-loaded Ti : LiNbO(3) integrated acousto-optic tunable filter are presented. An optimised Hamming apodisation is achieved through introducing an angular offset between the acoustic and optic cal waveguides along with carefully placed acoustic absorbers. The realised device has a 20-mm acoustic interaction length and achieves a 3-dB linewidth of 1.8 nm with 19-dB sidelobe suppression. The realised device is highly efficient, requiring a RF drive power of only 10 mW to achieve complete polarisation conversion. The enhanced drive efficiency of the device is analysed using both acoustic and optical mode analysis. Based on this analysis, possible explanations for the improved behaviour are presented and directions that may lead to further enhancements are discussed.