Math & science · 1917

Stimulated emission

Einstein predicts that light can trigger an atom to emit an identical photon.

The idea sat unused for decades until it became the operating principle of the maser (1954) and the laser (1960).

Arcs above join it to what it stood on, arcs below to what it led to. The bar places this stretch on the tree's whole timeline.

What it built on 2

The dashed line marks when it first worked.

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