TRANSIENT-GRATING FREQUENCY-RESOLVED OPTICAL GATING

We introduce a transient-grating beam geometry for frequency-resolved optical-gating measurements of ultrashort laser pulses and show that i t offers significant advantages over currently used geometries. Backgr ound free and phase matched over a long interaction length, it is the most sensitive third-order pulse-measurement geometry. In addition, fo r pulses greater than similar to 300 fs in length and similar to 1 mu J in energy, the nonlinear medium can be removed and the nonlinearity of air can be used to measure the pulse. (C) 1997 Optical Society of A merica.