Physics Colloquium - Friday, March 10th, 2006, 4:00 P.M.

E300 Math/Science Center; Refreshments at 3:30 P.M. in Room E200

Rick Trebino
Georgia Institute of Technology

Frontiers in the Characterization of Ultrashort Laser Pulses

FROG (Frequency Resolved Optical Gating) is a technique that completely characterizes an ultrashort laser pulse in time. Since its introduction about a decade ago, FROG has evolved into a fairly general and powerful technique for measuring ultrashort laser pulses. But to become truly useful, any optical technique must go beyond the measurement of mere laser pulses, whose intensity and phase are well-behaved in space, time, and frequency, and which have fairly high intensity. It will need to be able to measure, more generally, light pulses, whose intensity and phase are not so well-behaved in space, time, and frequency, and which often aren't all that intense. For example, we'd like to be able to measure ultrabroadband continuum pulses from micro-structure optical fiber and ultraweak luminescence from "non-fluorescent" molecules important in biology and human physiology--light pulses whose measurement will lead to new technologies or teach us important things about life, not just how well our laser is aligned. And we'd like to do so with confidence in our measurements. This necessarily means a simple device, not one so complex that it could easily cause the same distortions it hopes to measure. The goal is not a complex device that can only measure simple pulses, but a simple device that can measure complex pulses. We are making good progress, and recent developments include techniques for measuring light pulses that are extremely weak, have poor spatial coherence, have random absolute phase, have spatio-temporal distortions, and/or are extremely complex--and our devices are quite simple.