Research On Waveform Variation Mechanism Of Optical Pulses And Photon Echo Signals In Inhomogeneous Broadening Media

The transient coherent interaction of optical pulses with matter is a fundamental problem in quantum optics.When the atomic relaxation time is much longer than the interaction time,the relaxation effect does not have enough time to break the coherence of the system,making the interaction process satisfying this time scale requirement unique phenomena,such as the photon echo.The Mc Call-Hahn area theorem well describes the nonlinear transport process of an optical pulse in an inhomogeneous broadening media with a near-resonant frequency.However,the description of the transmission process by using only the pulse area fails to fully reveal the pulse waveform evolution law,and the rules about the evolution of the pulse waveform have not been well summarized so far,while the mechanism of the pulse waveform change in the media affects the identification and control of the photon echo signal.This thesis will apply accurate and effective numerical calculation methods to analyze and discuss the variation law of pulse waveform,and reveal the internal mechanism of photon echo signal waveform distortion.The main work of this thesis mainly includes the following aspects.1.The current status and analysis of domestic and international research on the nonlinear transmission process of optical pulses in media and photon echo effect are summarized,and the properties of doped rare-earth ion materials usually used to realize the photon echo effect and three photonic storage protocols based on the photon echo effect are briefly introduced.Based on the density matrix equation of motion of the two-energy system,a method is proposed to convert the set of Maxwell-Bloch equations into fully differential form by using the separation of space-time variables,and the equations are solved numerically by using the central difference format and the forecast-correction iterative algorithm,which effectively reduces the computational effort and computing time.2.Based on the evolution of the macroscopic population difference and the macroscopic dipole moment with time,the evolution law of optical pulse waveforms in the media is clarified and the physical mechanisms that make pulse area and waveform evolution are well explained.In a homogeneous broadening media,the pulse area and waveform of the pulse oscillate more readily than in an inhomogeneous broadening media.In homogeneous and inhomogeneous broadening media,the evolutionary trend of optical pulses is toward macroscopic population differences and macroscopic dipole moments evolving synchronously with time.The emphasis of the pulse waveform on the macroscopic population differences and the macroscopic dipole moments allows the atomic ensemble to still have the energy to drive pulse area and waveform evolution after the pulse action.3.Depending on whether the macroscopic dipole moment has a phase shift or not,the phenomenon of distortion of the photon echo signal,which is not intuitively similar to the input signal,is divided into two cases.The first case is the collective coherent natural adjoint photon echo signal waveform variations and the output time drifts of the atomic ensemble,which is known as false signal distortion.The second case is caused by the change of the recorded information through time-delay control,which leads to variations in the waveform of the photon echo signals and drifts in the output time,which is called real signal distortion.Taking the time-delay control technology in the two-pulse photon echo protocol as an example,it is found that the phase shift of the in-phase point of the macroscopic dipole moment caused by the pulse waveform making the real signal distortion of the photon echo signal waveform,and the output time of the photon echo signal does not change linearly with the duration of the control pulse,which provides a reference for the time and waveform correction of the photon echo control protocol.