Toward an ultra-stable laser based on cryogenic silicon cavity

We present the development of an ultra-stable laser based on a Fabry-Perot cavity made from single crystal silicon. This cavity is cooled down to 17 K to reach a nulling of the thermal expansion. Thanks to the high mechanical quality factor of silicon and to the low temperature, the expected thermal noise limited fractional frequency instability is 3 × 10
^-17
.