We demonstrate sawtooth wave adiabatic passage (SWAP) in a grating magneto-optical trap (MOT) operating on the ${}^1{S}_0\to {}^3{P}_1$ transition of neutral ${}^{88}\mathrm{Sr}$. 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 2 improvement in transfer efficiency between our ${}^1{S}_0\to {}^1{P}_1$ grating MOT and our ${}^1{S}_0\to {}^3{P}_1$ grating MOT. We trap up to $3\times {10}^6 {}^{88}\mathrm{Sr}$ atoms in the ${}^1{S}_0\to {}^3{P}_1$ grating MOT, at an average temperature of 4.9 $\mu \mathrm{K}$ with a lifetime of approximately 0.7 s. Our results show that SWAP is effective in nonorthogonal laser beam geometries, allowing greater duty cycles or higher atom number in sensors based on narrow-line grating MOTs.

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• Atom & ion cooling
• Cooling & trapping