It's the TEM 01 beam structure that allowed the simultaneous measurement of the wave-like interference pattern and the particle-like path through one of the slits.

His analyses showed that experimentally observed interference patterns, maxima and minima, could in fact be explained in terms of bright (detectable) and dark (undetectable) states of light.

They found that, in the very faint inelastic intensity, no fringes seem present, whereas interference fringes are recovered, at a very low intensity, when the elastic image is taken.

His analyses showed that experimentally observed interference patterns, maxima and minima, could in fact be explained in terms of bright (detectable) and dark (undetectable) states of light.