Two-color pulsed laser excitation of dipolar molecules: Absolute laser carrier phase effects

Abstract

The excitation of a two-level dipolar (d not equal 0) molecule with two Gaussian pulsed lasers is examined theoretically for the case where one laser's frequency is tuned close to the energy level separation (pump laser) while the second laser's frequency is extremely small (probe laser). The final excited state populations are shown to depend on the probe laser's absolute carrier phase while remaining independent of the pump laser's absolute carrier phase. They do not depend on the relative phase difference between the two laser fields as in many other pump-probe scenarios. The absolute carrier phase effect is negligible for non-dipolar (d = 0) molecules. The probe laser absolute carrier phase effect arises through the coherent excitation of multiple optical paths from the initial to the final state containing a common number of pump photons (N_pump=1) and a varying number of probe photons. Excited state populations, after the interaction of the pulses with the molecule is complete, are examined as a function of the probe laser's absolute carrier phase forvarying field strengths, frequencies, and pulse durations in order to verify the source of the probe laser absolute carrier phase effect and to determine the conditions needed to most readily detect it.

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