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 kappa(ZZ)(e-) component of 2.1(5.7) x 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) x 10(-10) on the isotropy parameter, P(MM) = delta-beta + 1 / 2 is set, which is more than a factor of 7 improvement.

The realization of high-performance tunable absorbers for terahertz frequencies is crucial for advancing applications such as single-pixel imaging and spectroscopy. Based on the strong position sensitivity of metamaterials' electromagnetic response, we combine meta-atoms that support strongly localized modes with suspended flat membranes that can be driven electrostatically. This design maximizes the tunability range for small mechanical displacements of the membranes. We employ a micro-electromechanical system technology and successfully fabricate the devices. Our prototype devices are among the best-performing tunable THz absorbers demonstrated to date, with an ultrathin device thickness (~1/50 of the working wavelength), absorption varying between 60% and 80% in the initial state when the membranes remain suspended, and fast switching speed (~27 μs). The absorption is tuned by an applied voltage, with the most marked results achieved when the structure reaches the snap-down state. In this case, the resonance shifts by 4200% of the linewidth (14% of the initial resonance frequency), and the absolute absorption modulation measured at the initial resonance can reach 65%. The demonstrated approach can be further optimized and extended to benefit numerous applications in THz technology.

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Recent experiments based on cryogenic microwave oscillators [1,2,3] have tested the isotropy of the speed of light (Michelson-Morley experiment) at sensitivities of the order of a part in 10 15 , which is a similar sensitivity to other best tests [4,5].Further improvements of the accuracy in this type of experiment are not expected due to the already long data set and the systematic error limit [3]. We have constructed a new rotating Michelson-Morley experiment consisting of two cylindrical cryogenic sapphire resonators. The temperature of the dual cavity is controlled at approximately 6 K where the beat frequency between two oscillators is independent on temperature. By rotating the experiment an improvement of several orders of magnitude in our sensitivity to light speed anisotropy is expected, as the relevant time variations will now be at the rotation frequency where the frequency stability of the cryogenic oscillators is the best. Michelson-Morley, Crypgenic Sapphire Oscillator, Dual Cavity

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