Dicka

Dicka, a choir of glowing atoms in unison, sings one blinding note where a crowd of soloists would only hum.

The Physics

N excited atoms that radiate independently give N times the light of one. But if they are packed close together, within about a wavelength, or otherwise coupled to the same light field, they can lock into phase and radiate as one giant dipole. Then the peak intensity grows as N², and the light comes out in a short, bright burst. Robert Dicke predicted this in “Coherence in Spontaneous Radiation Processes” (Phys. Rev. 93, 99, 1954).

I_peak ∝ N²

• I_peak: peak emitted intensity (W)
• N: number of emitters radiating in phase

The total energy released is still N photons' worth. Because the intensity is about N times higher, the burst is about N times shorter than the emission time of a single atom in the ideal model.

Honest caveat: Independent emitters give I ∝ N; the N² law holds only when the emitters stay in phase. In real samples dephasing, atom motion and the sample's size and shape reduce the effect.

On the sticker

Dicka opens her mouth in song as a ring of violet atoms flashes together in her hands. Printed text: DICKA with the line I ∝ N². Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.