Ultrastable laser based on multi-cavity

We report a proposal of developing ultrastable laser referenced to multi-cavity, reducing thermal noise by averaging effect of beam size. We perform an experiment to simulate a two-cavity system and obtained the instability is, $5\times 10-16 @1\mathrm{s}$, improved by a factor of ✓2 from a single cavity system. © 2019 The Author(s)