Influence of the size of the cubic atomic vapor cell on a Rydberg atomic microwave sensor

This study investigates the enhancement of the microwave (MW) electric (E) field due to the Fabry-Perot (FP) effect in cubic cells of varying sizes, and it is confirmed that the lower limit of MW power can be measured. Theoretical simulations and empirical validations are conducted for three vapor cells of different sizes. At a MW frequency of 23.904 GHz, the FP effect in the 10 mm cell is found to significantly enhance the MW E-field relative to larger cells (20 and 25 mm). The results show that, due to the existence of the FP effect, the lower limit of MW power can be measured in the cubic atomic vapor cells with different sizes. These findings contribute to the advancement of the vapor cell design for quantum accuracy measurements and the development of future atomic MW communication technologies.