We demonstrate monolithically integrated four and eight-channel coarse-wavelength-division multiplexers with low insertion loss (IL) and wide flat-top passbands based on integrated-holographic filters. Like thin-film filters (TFFs), integrated-holographic filters function via a multipath interference and thus offer flexible passband control without the IL penalty that passband shaping typically incurs in single-mode angularly dispersive devices. Unlike TFF-based multiplexers, the multiplexers described here are based on the silica-on-silicon planar lightwave circuit platform rather than discrete optics and thus uniquely provide powerful TFF-like filtering function in fully integrated format. The multiplexer performance demonstrated is superior to the integrated solutions demonstrated to date, and competitive with discrete TFF-based devices.
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