"Measuring Everything You've Always Wanted to Know About a Laser Pulse"
September 7, 2011 - 11:00am
Marcus Nanotech Conf.
Measuring an event in time seems to require a shorter one. As a result, the development of a technique for measuring ultrashort laser pulses—the shortest events ever created—has been particularly difficult. We have, however, developed simple methods for fully characterizing these events, that is, for measuring a pulse's intensity and phase vs. time. One involves making an optical spectrogram of the pulse by using nonlinear optic. The mathematics involved is equivalent to the two-dimensional phase-retrieval problem—a problem that’s solvable because the Fundamental Theorem of Algebra fails for polynomials of two variables. We call this method Frequency-Resolved Optical Gating (FROG), and it’s simple, rigorous, intuitive, and general. FROG has been used to measure pulses as short as 80 attoseconds (8×10-17s), and it has also measured the most complex ultrashort pulse ever generated. And we have recently developed simple methods (also with frivolous acronyms: SEA TADPOLE, MUD TADPOLE, and STRIPED FISH) for measuring the complete spatio-temporal field of an arbitrary laser pulse, making ultrashort laser pulses the best characterized form of light known to humankind.