In integrated photonics, precise control of light signals plays a pivotal role. Typically, light routing within photonic devices relies on multi-mode interferometers and micro resonators. Here, we investigate, both theoretically and experimentally, the use of such devices in achieving a versatile 3x3 tunable switch where light can be routed from each input port to any output ports. To accomplish this, we have designed and tested various 3x3 coupler structures in silicon. The results from the analysis of these structures, using coupled mode theory and a transfer matrix, are in good agreement with the experimental findings. We show that the device can cross the signal from the external waveguide while maintaining the central waveguide unaltered, or even achieving a balanced output across all three output ports. Direct (1-1), split (1-2+3), and cross (1-3) paths, along with any arbitrary combination thereof. In quantum optics, a single 3x3 coupler allows the manipulation of the photon state vector within almost the whole three-dimensional Bloch sphere.
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