A novel optimized heterodyne method that recovers the complete electric field of any four-wave mixing signal at its point of origin is demonstrated. A tracer pulse is sent along the signal path and characterized at the sample by frequency-resolved optical gating. Spectral interferometry is used to determine the phase difference between the tracer and a reference pulse, the absorptive change in tracer phase in the sample, and the reference-signal phase difference. Together, these measurements allow calculation of the signal phase at the sample. The phase of three pulse-scattering signals from solutions of the infrared dye IR 144 in methanol determines the absolute signal-emission time within 0.5 fs.
© 1998 Optical Society of America
Sarah M. Gallagher, Allison W. Albrecht, John D. Hybl, Brett L. Landin, Bhavani Rajaram, and David M. Jonas, "Heterodyne detection of the complete electric field of femtosecond four-wave mixing signals," J. Opt. Soc. Am. B 15, 2338-2345 (1998)