photo echo

photo echo

[′fōd·ō ‚ek·ō]
(optics)
A coherent pulse of light generated in a nonlinear medium at a characteristic time after two other pulses, separated by a certain time interval, have entered the medium.
References in periodicals archive ?
uk, with contact information and a few details about the photo ECHO reader Glenda Bonnici from Walton sent in this official photograph of the pre-opening of the Mersey Tunnel in 1934.