Test of the Isotropy of the Speed of Light Using a Continuously Rotating Optical Resonator

We report on a test of Lorentz invariance performed by comparing the resonance frequencies of one stationary optical resonator and one continuously rotating on a precision air bearing turntable. Special attention is paid to the control of rotation induced systematic effects. Within the photon sector of the standard model extension, we obtain improved limits on combinations of 8 parameters at a level of a few parts in ${10}^{-16}$. For the previously least well known parameter we find ${\tilde{\kappa }}_{e-}^{ZZ}=(-1.9\pm 5.2)\times {10}^{-15}$. Within the Robertson-Mansouri-Sexl test theory, our measurement restricts the isotropy violation parameter $\beta -\delta -\frac{1}{2}$ to $(-2.1\pm 1.9)\times {10}^{-10}$, corresponding to an eightfold improvement with respect to previous nonrotating measurements.