Abstract: An iron-air battery including an iron electrode in contact with an anode current collector, wherein the iron electrode includes a plurality of channels; an oxygen reduction reaction electrode having a first surface facing the plurality of channels and an opposing second surface in contact with air; an oxygen evolution reaction electrode interdigitated with the plurality of channels of the iron electrode, wherein at least a portion of the oxygen evolution reaction electrode is disposed within the plurality of channels in a direction perpendicular to a plane of the oxygen reduction reaction electrode; and an electrolyte in contact with the iron electrode, the first surface of the oxygen reduction reaction electrode, the plurality of channels, and the oxygen evolution reaction electrode.

Abstract: A wavelength division multiplexer (WDM) utilizes cascaded interferometric devices, where the two output branches of interferometric devices in each new stage are each coupled to an additional stage of interferometric devices having the same wavelength separation or channel spacing, which suppresses the sidelobes of the signals from preceding stage of interferometric devices. In one embodiment, the interferometric devices are unbalanced Mach-Zehnder Interferometers.