Home▸Physics & Mechanics▸The Purcell Effect: How a Cavity Controls Spontaneous Emission

💡 The Purcell Effect: How a Cavity Controls Spontaneous Emission

Explore why an excited atom's decay rate isn't fixed but depends on the electromagnetic environment around it. See how tuning a microcavity's quality factor and mode volume speeds up or suppresses spontaneous emission through the Purcell effect.

Physics & Mechanics3DModerate60 FPS

The simulator demonstrates that spontaneous emission rate is not fixed but emerges from Fermi's golden rule applied to the local density of photonic states, showing in real time how tuning a cavity's quality factor, mode volume, and detuning from the emitter's transition frequency enhances or suppresses the emission rate relative to free space, quantified by the Purcell factor.

🔬 What It Demonstrates

🎮 How to Use

Set the emitter's natural transition frequency and its free-space emission rate, then adjust the cavity's quality factor and mode volume to see the resulting Purcell factor and enhanced decay rate calculated live. Sweep the cavity's resonant frequency away from the emitter's transition to see enhancement fall off and, past a threshold, watch how a photonic-bandgap-style zero-density-of-states region suppresses emission below the free-space rate. Watch the accompanying density-of-states plot and decay-curve animation update as you change each parameter.

💡 Did You Know?

Did you know that Edward Purcell's original 1946 paper on this effect was only a few sentences long and said nothing about light at all? It concerned nuclear spins relaxing inside a radiofrequency resonant circuit; the leap to optical microcavities and single-photon sources came decades later, once scientists realized the same golden-rule logic about density of states applies equally to radio waves and to visible light.

⚙ Under the hood

quantum opticscavity qedspontaneous emissionphotonicssingle-photon sourcesdensity of statesmicrocavityfermi golden rule

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install