Experimental Progress Toward Multiple Adiabatic Rapid Passage Sequences

Multiple repetitions of adiabatic rapid passage (ARP) sweeps with counterpropagating light beams can enable huge optical forces on atoms\footnote{T. Lu, X. Miao, and H. Metcalf, Phys., Rev. {\bf A 71} 061405(R) (2005)}. The repetition rate of the ARP sweeps $\omega_s \gg \gamma$ results in a force $\hbar k \omega_s/\pi \gg \hbar k \gamma/2 \equiv F_{rad}$ where $1/\gamma \equiv \tau$ is the excited state lifetime and $F_{rad}$ is the ordinary radiative force. This is because each pair of ARP-induced inversions can coherently transfer momentum $\pm 2 \hbar k$ between the light beams, and thus $\mp 2 \hbar k$ to the atoms. In developing instruments for such experiments on the 2$^3$S$_1 \rightarrow$ 2$^3$P$_2$ transition at $\lambda$ = 1083 nm in He, we exploit recent developments in the optical communications industry. We use commercial phase and intensity modulators of the LiNbO$_3$ waveguide type having $V_{\pi}$ as low as 6 V and thus requiring relatively low rf power for the modulation. Synchronized driving of the two modulators can produce the necessary multiple ARP sequences of 10 ns chirped pulses that span several GHz, as needed for the experiment$^3$. We are also developing optical methods for characterizing these pulses.