Adiabatic Rapid Passage Forces for Laser Cooling

Optical forces from Adiabatic Rapid Passage (ARP) have been shown to be significantly larger than the ordinary radiative force even outside the usual adiabatic parameter range of $\Omega_0 \sim \delta_0 \gg \omega_m \gg \gamma$. Here $\Omega_0$ is the peak Rabi frequency, $2 \delta_0$ is the sweep range, $\omega_m$ is the repetition rate, and $\tau \equiv 1/\gamma$ is the excited state lifetime. For ARP to be useful for laser cooling it needs to be not only strong, but also dependent on atomic velocity $v$. We have shown preliminary $v$-dependent measurements with an apparatus having two independent counter-propagating chirped pulses. Having further improved our ability to measure and control the pulse shape and frequency chirp we present our newest $v$-dependent data and draw some comparisons between ARP and the bichromatic force.