Low-crosstalk WDM by Bragg diffraction fromthermally fixed reflection holograms in lithium niobate

Dense wavelength-division-multiplexing (WDM) systems require narrowband wavelength filters for simultaneous multiplexing/demultiplexing of several channels. As a proof of concept the authors report the demultiplexing of two channels (channel spacing 0.8 nm) by Bragg diffraction from two thermally fixed volume phase reflection holograms in photorefractive lithium niobate crystals doped with iron. More than 25 dB crosstalk suppression is achieved, and intensity losses are only between 2.3 and 5.2 dB.