Transfer Of Orbital Angular Momentum Of Light Using Electromagnetically Induced Transparency

Optical vortex is a special optical field with helical wavefront phase and orbital angular momentum.With the increasingly development of science and technology,optical information storage has also gradually attracted more and more people's attention,the demand of large amount of information increases the requirement of optical information storage capacity,Due to its special wave-front structure and orbital angular momentum,vortex light has been applied in optical information storage by many researchers.Therefore,experiments on vortex light used in optical information storage have been widely reported.We can encode the information in the OAM degree of freedom of the light field,so the constructed high-dimensional quantum state(infinite dimensional Hilbert space)can greatly increase the information capacity of the quantum network,at the same time,this method can also process quantum information more efficiently,providing a good way for quantum information processing and quantum computing.Experiments on optical information storage have been mainly carried out in atomic gases,while there are few reports on opticalinformation storage experiments in solids.However,in practical applications,solid materials are more advantageous experimental media than gas materials,the advantages of solid materials,such as small size,easy integration,excellent spectral structure and portability,all indicate that it is a good carrier of optical information.Therefore,solid optical information storage will play a huge role in quantum communication.We experimentally investigate the transfer of orbital angular momentum(OAM)of light in a solid driven by electromagnetically induced transparency(EIT).Under the condition of dynamical EIT,in order to avoid the absorption loss of the probe field,the first control field is non-vortex light,and the probe field is vortex light with OAM,the storage and retrieval of the OAM of the probe pulse in the experimental medium are realized successfully by operating the closing and opening of the first control field.In this experiment,we not only verify the consistency of the topological charge before and after storage,but also further analyze the relationship between storage efficiency and storage time,and the fidelity of the retrieved OAM image.It has important application value in the development of solid quantum memory.Next,we use the four-level double-lambda system to realize the transfer of OAM based on EIT storage.In this experiment,the probe field is vortex light with OAM,and the first control field and the second control field are both non-vortex light.Firstly,the first control field isclosed to realize the optical information storage,after a period of time,the second control field is opened to retrieve the stored information.Experiments show that the OAM can be transferred from the probe field to the newly generated signal field,which has a new space-frequency mode compared with the input mode.Then the second control field is vortex light with OAM,and the probe field and the first control field are both non-vortex light.Repeating the above experimental steps,the results show that the OAM can also be transferred from the second field to the newly generated signal field.It has laid an important foundation for the research of quantum storage technology and quantum secure communication.Furthermore,we use EIT-based four-wave mixing(FWM)to investigate the direct OAM transfer without experiencing the storage,where we do not need to switch off and back-on the control field.There are potential applications for future quantum networks.