A multiple‐stripe quantum well heterostructure laser diode operated in an external grating cavity is shown to exhibit the far‐field radiation patterns of the ‘‘supermode’’ eigenstates predicted by coupled mode analysis. Data (∼7330 A˚) are presented on a gain‐guided laser array at various continuous (cw, 300 K) operating currents to illustrate the progression of the supermodes from double‐lobed patterns (phase shift between emitters) to a single‐lobed pattern (no phase shift between emitters). As the cavity wavelength is scanned a cyclical progression (2.8‐A˚ period) of far‐field patterns (supermodes) is observed.