Sub-Doppler spectroscopy of the strontium intercombination line in a microfabricated vapor cell

We report a 100 kHz linewidth for the ¹S₀ to ³P₁ intercombination line of ⁸⁸Sr atoms at 689 nm in a microfabricated (9×14×4.4) mm³ vapor cell. This puts an upper bound on the residual gas pressure in the vapor cell of 10 mTorr. The microfabricated Sr vapor cell offers an inexpensive and scalable way to lock lasers in state-of-the-art cold-atom-based atomic clocks and quantum computing experiments. It also paves the way for compact and precise optical frequency references based on alkaline earth vapor cells.