Schematic of the photonic beam combiner including, from left to right, the four inputs of the chip, and photometric taps labeled Y1 and Y2, the first combination stage composed of two directional couplers, and the second stage consisting of a single directional coupler mixing the dark outputs of the first stage. The chip has eight outputs, including photometric outputs (0, 1, 6, and 7), bright outputs (2 and 5), and two complementary dark outputs (3 and 4).