Time-resolved @O04314@ in which the inhomogeneous broadening of absorbers is eliminated by the proper choice of geometry in a four-wave mixing experiment.
- Term applied to a group of @NT07426@ such as integrated echo, time-gated echo, three-pulse echo peak shift, heterodyne-detected echo and 2D-echo.
- Photon echo techniques make use of the third-order optical @P04712@ and 'hyper-susceptibility'. The main distinguishing feature of photon echo methods from all other third-order processes is the time ordering of the field interactions that leads to a rephasing process in the induced @P04712@ to remove inhomogeneous contributions to the absorption linewidth.
- In terms of mathematical description, the photon echo is equal to the spin echo (solid-state physics) from which a term 'echo' was borrowed.
- Technique used, e.g., to probe @S05747@ dynamics upon (ultra-short) pulse excitation of a @C01076@.