Optical light oscillates at frequencies near 500 THz, more than 50,000 times faster than the caesium microwave atomic clock.
Millions of neutral strontium atoms can be trapped in an optical lattice of shallow trap sites, while ion clocks co-trap species such as aluminum and mercury.
Optical clocks have been demonstrated to keep time with less error than microwave caesium clocks; John L. Hall and Theodor W. Hänsch shared the 2005 Nobel Prize in Physics for contributions to their development.