Ultra-Stable Optical Oscillator Transfer to the UV for Primary Thermometry

The temperature, T, is a key parameter in many fields of industry and science. Currently, the Kelvin definition in the International System of Units (SI) is linked to the triple point of water and this leads to significant difficulties in the precise measure of thermodynamical temperatures very far from it. As a consequence, in 2018, the International Committee for Weights and Measures (CIPM) established T measurements in terms of the thermal energy of the particle system, K
_B
T, setting an exact value for K
_B
, and then the recalibration of T scale for avoiding artifacts or material dependencies of the SI unit.