  We report on experiments generating a magneto-optical trap (MOT) of
88-strontium ($^{88}$Sr) atoms at microkelvin temperature, using
integrated-photonics devices. With metasurface optics integrated on a
fused-silica substrate, we generate six-beam, circularly polarized,
counter-propagating MOTs on the blue broad-line, 461 nm, and red narrow-line,
689 nm, Sr cooling transitions without bulk optics. By use of a diverging beam
configuration, we create up to 10 mm diameter MOT beams at the trapping
location. To frequency stabilize and linewidth narrow the cooling lasers, we
use fiber-packaged, integrated nonlinear waveguides to spectrally broaden a
frequency comb. The ultra-coherent supercontinuum of the waveguides covers 650
nm to 2500 nm, enabling phase locks of the cooling lasers to hertz level
linewidth. Our work highlights the possibility to simplify the preparation of
an ultracold 88Sr gas for an optical-lattice clock with photonic devices. By
implementing a timing sequence for control of the MOT lasers and the quadrupole
magnetic-field gradient, we collect atoms directly from a thermal beam into the
blue MOT and continuously cool into a red MOT with dynamic detuning and
intensity control. There, the red MOT temperature is as low as $2~{\mu}$K and
the overall transfer efficiency up to 16%. We characterize this sequence,
including an intermediate red MOT with modulated detuning. Our experiments
demonstrate an integrated photonics system capable of cooling alkaline-earth
gases to microkelvin temperature with sufficient transfer efficiencies for
adoption in scalable optical clocks and quantum sensors.
