A Michelson-Morley Test of Lorentz Invariance Using a Rotating Optical Cavity

This thesis presents a modern Michelson-Morley experiment, which provides improved limits on test parameters that model a violation of Lorentz invariance in electrodynamics. The measurement thereby sets an upper limit on an anisotropy of the speed of light at a level of ∆c/c ∼ 10−16. The experiment compares the resonance frequencies of two optical highfinesse cavities, one of them continuously rotating on a turntable. To read out their resonance frequencies, two Nd:YAG lasers are frequency-stabilized to these cavities. On the timescale of a turntable rotation (∼ 45 s), a relative frequency stability of ∼ 1×10−14 is achieved, limited by thermal noise of the cavity mirrors. An anisotropic propagation of light would cause a modulation of the rotating cavity’s resonance at twice the turntable rotation rate, additionally modulated by Earth’s rotation and orbital revolution. Two test theories are applied here, to derive such an anisotropy signal as a consequence of a violation of Lorentz invariance. These test theories are an extension of the standard-model of particle physics, based on work by V.A. Kostelecký et al., and a kinematic formalism by H.P. Robertson, R. Mansouri and R.U. Sexl. Previously as well as simultaneously performed Michelson-Morley experiments were severely affected by systematic effects arising from the rotation of the setup on a turntable. Several systematic effects have been identified within the present experiment as well. These systematics are described in detail, together with the measures that have been taken to suppress systematic signal amplitudes below 1Hz. This is a reduction by up to a factor of 100 as compared to preceding experiments. During the course of one year, 27 frequency comparisons of the rotating with the non-rotating cavity have been performed, each spanning 24 h to 100 h of continuous measurement. In total, the measurement includes ∼ 105 rotations. An analysis of this data within the two test models is presented and limits on the relevant test parameters are deduced. These limits restrict an anisotropy of the speed of light at a level of 10−16, which is a factor of ten more stringent as compared to results of previous such measurements. Further improved limits on a violation of Lorentz invariance might be obtained within the near future. An improved setup with new cavities, that exhibit lower thermal noise, and first data from this setup are already presented here. The relative frequency stability has been enhanced to 2× 10−15 at the timescale of a turntable rotation. This opens the door to another order of magnitude improvement of the experiment’s sensitivity within a long-term measurement aiming for the ∆c/c ∼ 10−17 level of accuracy.