We present the first results from a rotating Michelson-Morley experiment that uses two orthogonally orientated cryogenic sapphire resonator oscillators operating in whispering gallery modes near 10 GHz. The experiment is used to test for violations of Lorentz invariance in the framework of the photon sector of the standard model extension (SME), as well as the isotropy term of the Robertson-Mansouri-Sexl (RMS) framework. In the SME we set a new bound on the previously unmeasured ${\tilde{\kappa }}_{e-}^{ZZ}$ component of $2.1(5.7)\times {10}^{-14}$, and set more stringent bounds by up to a factor of 7 on seven other components. In the RMS a more stringent bound of $-0.9(2.0)\times {10}^{-10}$ on the isotropy parameter, $P_{\mathrm{MM}}=\delta -\beta +\frac{1}{2}$ is set, which is more than a factor of 7 improvement.

• Received 2 May 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.040404