Sawtooth wave adiabatic passage in a grating magneto-optical trap

We demonstrate sawtooth wave adiabatic passage (SWAP) in a grating magneto-optical trap (MOT) operating on the ¹S₀ → ³P₁ transition of neutral ⁸⁸Sr. From numerical simulations of SWAP using our laser beam geometry, we find that SWAP provides greater cooling than triangle wave frequency modulation despite the complex polarization environment of a grating MOT. The simulation is confirmed by our experimental results, where we demonstrate a factor of two improvement in transfer efficiency between our ¹S₀ → ¹P₁ grating MOT and our ¹S₀ → ³P₁ grating MOT. We trap up to 3times10^{6 88}Sr atoms in the ¹S₀ → ³P₁ grating MOT, at an average temperature of 4.9 μK with a lifetime of approximately 0.7 s. Our results show that SWAP is effective in non-orthogonal laser beam geometries, allowing greater duty cycles or higher atom number in sensors based on narrow-line grating MOTs.