#nonlinear optics
Every note tagged #nonlinear optics, newest first — or browse the full archive.
From blinking to absorption: how one molecule becomes a spectrum
A single fluorescent molecule blinks; a cuvette full of the same molecules gives a smooth absorption band. The two pictures are the same Jablonski diagram read at different scales — one molecule versus an ensemble, one photon at a time versus a steady-state rate. This post traces the path from quantized absorption and emission events to a bulk spectrum, and extends the same diagram to two-photon absorption as the nonlinear version of the same transition.
Molecules as circuits — a chromophore as an RLC resonator
An absorption energy gap is a resonant frequency, a transition dipole is charge sloshing across a capacitor, and a linewidth is a resistance — so a dye molecule is literally a driven RLC circuit. This post makes the analogy pay its way, pinning every circuit element to a number from a real chromophore I synthesized, then shows the three places the model quietly stops describing the physics: the hyperpolarizability, the quantum interference in the wiring, and the many-body order that actually sets device performance.
One matrix element, two experiments: molar absorptivity and the Pockels effect
A companion to the molar-absorptivity post. The absolute height of an absorption band, the refractive index, and the electro-optic coefficient of a poled material are three readouts of one quantity — the transition dipole. Normalizing every spectrum to 1 throws that quantity away. This traces the same matrix element from Beer's law through the two-level model to the Pockels effect, with worked numbers.