The data-carrying light waves in optical fibers have either horizontal or vertical polarities. Both types of waves are easily processed in today’s millimeter-scale photonic devices, but polarization differences may lead to signal loss in future micrometer-scale devices on chips. This submicrometer structure from MIT’s Research Laboratory of Electronics can be etched into silicon. Light enters a waveguide and is split into horizontal and vertical components. Vertical beams are rotated to horizontal for processing and later recombined.