Lithographically rendered, slab-waveguide-based, volume holographic filters are shown, via fabrication and test, capable of providing fully integrated, single-mode compatible, flat-topped and low loss filtering for wide bandwidth multiplexers as, for example, used in coarse wave-division multiplexing (CWDM). Single-mode compatibility is preserved since the filters operate via multi-path interference like thin-film filters rather than the angular dispersion typically utilized by grating type devices. Flexible apodization, entirely consistent with simple binary etch, is employed to provide steep passband falloff. High reflectivity and wide bandwidth is enabled through a tailored dual core waveguide geometry providing for mode concentration on the diffractive elements.
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