Konstanz 1998 – scientific programme

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Q: Quantenoptik

Q 2: Nichtlineare Optik I

Q 2.5: Talk

Monday, March 16, 1998, 15:00–15:15, R 512

The dip in the nearly degenerate four wave mixing spectra - new interpretation — •O. K. Andersen, D. Lenstra, and S. Stolte — Dept. of Chemistry, Laser Centre, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, Netherlands

We present a new interpretation of the ’dip’ observed at linecenter observed for nearly degenerate four wave mixing (NDFWM) in alkali metal vapors when the pump is tuned to the atomic resonance. The theoretical treatment starts from the Schr"odinger equation of a two level atom interacting with a pump field at frequency w. The semiclassical dressed states for this system are calculated, and the probe field with frequency w+d,|d|<<w is considered as a perturbation to the dressed atom. In this picture the NDFWM signal at w-d is a consequence of the dressed atom undergoing a transition from one dressed state to the other.Theory then predicts the shape of the yield to be strongly dependent on the specific initial conditions: starting the system in one of the two dressed states gives no dip at all, while certain superposition states do result in dips. The dip is thus a quantum interference effect between two channels.