Strong Field Multiphoton Inversion of a Three-Level System Using Shaped Ultrafast Laser Pulses

We demonstrate strong-field population inversion in a three-level system with single and multiphoton coupling between levels using a single shaped ultrafast laser pulse. Our interpretation of the pulse shape dependence illustrates the difference between sequential population transfer and adiabatic rapid passage in three-level systems with multiphoton coupling between levels.

Figure 1

The solid and dashed curves show fluorescence measurements (including light from the $7s\mathrm{\text{−}}3p$ and $6d\mathrm{\text{−}}3p$ transitions) for GA optimized and unshaped laser pulses; the inset shows the Wigner distribution for an optimal pulse.

Figure 2

(a) Measurement of $7s\mathrm{\text{−}}3p$ and $6d\mathrm{\text{−}}3p$ fluorescence as a function of chirp. The data are normalized to the maximum fluorescence measured and the white $X$ marks the chirp rate associated with a pulse discovered by the GA. (b) Simulation of the $7p$ population as a function of pulse energy and chirp.

Figure 3

Calculated Wigner distributions for chirp rates of (a) $-0.002{\mathrm{ps}}^2$ and (b) $0.002{\mathrm{ps}}^2$. (c),(d) The $3s$ (dashed line), $4s$ (dash-dotted line), and $7p$ (solid red line) populations, as well as the field envelope (solid black line), corresponding to (a) and (b), respectively, for a pulse energy of $3U_0$.

Figure 4

Calculated dressed states using ${\mathbf{H}}_{\mathbf{I}}(t)$. The inset shows normalized nonadiabatic corrections for one of the eigenvalues of equation ${\mathbf{H}}_{\mathbf{I}}^{\prime }(t)$ as a function of $\beta$.