Test Of Lorentz Invariance Using Optical Cavities

Lorentz invariance plays an important role in space-time transformations since the discovery of the theory of special relativity during Einstein’s annus mirabilis in 1905.However,some developing theories of quantum gravity implies a violation of Lorentz invariance in Planck scale.Probing this spacetime symmetry in low-energy region with high precision not only verifies the theory of special relativity but may also lead to experimental clues for developing new theoretical models beyond the standard model of elementary particle physics.Experiments using rotating optical cavities take the advantage of the high frequency stability and detection sensitivity.The rotating-opticalcavities system,which is capable of continuous and long-term operation,is adopted to test Lorentz invariance in laboratory.In this thesis,we focus on a rotating-opticalcavities apparatus to test Lorentz invariance.In the 2017,we developed a rotating-optical-cavities apparatus based on a mechanical bearing turntable.In our previous work,the test precision was at the level of 10-15,which was limited by the fluctuation of tilt and laser intensity fluctuation.In this work,extensive improvements have been made on the test apparatus.The mechanical turntable is replaced by a more advanced,highly precision air-floated one.Two lasers are separately guided onto the turntable from the ceiling and floor,respectively.After improving the beam pointing and polarization stability on the rotating breadboard,the intensity fluctuation caused by table rotation is reduced.To avoid thermal effect due to the variations of the laser powers circulating inside the resonators,active stabilization of the cavity transmitted optical power has been implemented.In addition,multiple uninterruptible power suppliers are adopted to ensure long-term and continuous operation.In rotating-cavity experiment,tilt variation of the turntable during rotation is a major limiting factor that affects the test precision and contaminates an otherwise ideal null result.Incorporated into the existing active vibration isolation,a single-stage,twoaxis tilt control system is developed to suppress the tilt variation from its free-running value of±30 μrad to within±0.1μrad,leading to a reduced influence on the test precision below 10-17 level.A multi-step,least-square fitting procedure with constraint is developed to analyze the experimental data as well as the systematic effects.Prior to its usage,the validity of the fitting procedure is verified by numerical simulations.After above-mentioned improvements,the system has been operated for 173 days,collecting totally 119 days’(～170,000 rotations)worth of valid data.By fitting the data to the predication of the test model,Lorentz invariance violating parameters both in Standard Model Extension and Robertson-Mansouri-Sexl model are constrained with precisions at the level of 10-17.Uncertainties of the experimental values of five κeparameters show a1/√t decreasing trend with the measurement time.Influence of major five external perturbations,including the intensity(optical power)fluctuation,residual amplitude modulation(RAM),residual tilt variation,temperature fluctuation,and the instability of the rotational speed,are quantitatively analyzed.Currently,the intensity fluctuation and RAM are two dominant precision-limiting sources.In addition,we explore the feasibility of correlation test in the rotating-cavity experiment.The correlation method is quantitatively analyzed by using numerical simulation in our investigation.Except for a possibility of losing the phase information,the simulation shows that results of the correlation measurement agree with these obtained by using least square.To sum up,several performance-limiting problems,such as the tilt variation of the turntable,have been addressed in current investigation,enabling a reliable and longterm operation of the test apparatus and the determination of the eight Lorentz violating parameters relevant to the rotating-cavity experiment in the framework of standard model extension.These works have laid a solid foundation for the future improvement on the experiment and hence for the 10-18-level test precision and beyond.