Research On Optical Cavity-Enhanced Microwave Electric Field Measurement Based On Rydberg Atoms

Optical cavity is an excellent platform for the interaction between light and matter,providing a new method for improving the sensitivity of atomic sensing.One of the most important parts is intracavity electromagnetically induced transparency(EIT).Under the control of the external light field,the absorption and dispersion characteristics of the medium for the probe field changes,the cavity transmission changes accordingly.Intracavity EIT has widely used in slow light effects,frequency stabilization,and quantum communication.Rydberg atom has a large electric dipole moment,it determines a higher frequency response to the microwave(MW)field,which is suitable for the measurement of MW electric fields.Most current MW electric field measurement schemes are based on the absorption or transmission spectrum of the medium.The spectral linewidth limits the improvement of measurement sensitivity.This dissertation studies the scheme to improve the sensitivity of MW electric field measurement,main tasks as follows:1.An enhanced measurement of the MW electric field by using intracavity Rydberg atoms is proposed.Based on EIT,the intracavity atomic system exhibits two EIT windows when the MW field couples the Rydberg state transition,resulting in two narrow peaks in the cavity transmission.The peak-to-peak distance is sensitive to MW fields and can be used to probe MW electric field strength.Simulation results show that the detectable minimum strength of the MW fields is nearly eight times smaller than that without a cavity.Due to cavity coupling,the transmission spectrum is greatly narrowed,which improves the measurement resolution substantially.The numerical results show that the spectrum resolution is increased by more than twenty times.Furthermore,the linewidth of the transmission spectrum changes small under strong control field conditions,which means that the cavity-enhaned scheme maintaining a high sensitivity.As the detuning of the control field changes,the scheme could measure MV electric fields in different frequency ranges.In practical application,the influence of cavity detuning on the peak-to-peak distances and linewidth of the transmission spectrum is not obvious,indicating that the scheme is still applicable in the case of cavity detuning.2.A scheme for enhancing the sensitivity of MW electric field measurement based on the intracavity anomalous dispersion is proposed.The scheme uses four-level Rydberg atoms,when the Raman field couples the ground state transition and has a large frequency detuning,gain effect appears in the spectrum and two gain peaks appear in the cavity transmission spectrum.The peak-to-peak distance has a linear relationship with the MW field strength,which can be used to probe the MW electric field strength.Simulation results show that the large anomalous dispersion at the gain window can significantly broad the peak-to-peak distance,which improves the measurement sensitivity substantially.Compared with the scheme without cavity,the sensitivity of the cavity enhanced scheme is increased by more than ten times.In addition,the normal dispersion narrows the cavity transmission linewidth,which helps further improve the measurement sensitivity.