The wave interference effect can be demonstrated by dropping two pebbles in a pond, to reveal fixed directions along which spreading water ripples add up or cancel out. Can this phenomena help explain the unique ability to steer a laser light beam, using a fixed bank of modulator arms? Recall each arm slows a wave of light by a small amount, and thereby creates a tiny time lag for when it exits from an integrated photonics chip—and spreads out, or diverges—into air.