Focusing And Special Beam Generation Through Scattering Medium By Polarization Transmission Matrix

Optical focusing and imaging relies on the illuminate,collect and light transmission capability through the scattering medium.The transmission matrix method relates the incident light field to the output light field through the scattering medium in a matrix.Once the optical transmission matrix of the scattering medium is measured,the channels of the transmission matrix can be optimally used to coherently transmit and recover arbitrary images with high fidelity.The study of the optical transmission matrix is important for the study of the scattering properties of the scattering medium,which is generally modulated in terms of intensity,phase and polarization in the spatial domain of the optical field.With the development of optics,the study of phase and amplitude in the direction of wavefront shaping has gradually matured,while polarization is less studied.In addition,by manipulating the optical field inside the scattering medium to generate special beams,such as Bessel beams,smaller focal spot size and longer depth of focus can be generated.The study of optical field modulation inside the scattering medium will provide new ideas for the application of wavefront shaping techniques in biomedicine,super-resolution imaging and optical communication.Based on the status of domestic and international research,this paper proposes a single-polarization transmission matrix method,which carries out systematic theoretical analysis,numerical analysis and experimental verification of focusing and imaging through scattering media and the generation of special beams,and the specific research work is as follows:(1)Based on the analysis of light transmission in scattering media,the scalar transmission matrix theory and the vector transmission matrix theory are introduced.On this basis,based on the angular spectrum diffraction theory,the four-step phase-shift holographic method and the Hadamard basis measurement method,it is shown by numerical simulation that focusing or imaging through the scattering medium can be achieved based on the scalar transmission matrix method.Based on the experiments,the spatial light modulator is calibrated.by the vector transmission matrix theory,it is verified that the light through scattering medium is linearly depolarized.(2)An experimental system based on a single polarization transmission matrix is designed to realize scattering focusing and imaging.Based on the vector transmission matrix theory,two transmission matrices with orthogonal polarization directions are measured and correlated with the ideal single polarization transmission matrix to obtain the single polarization transmission matrix containing the optimal polarization angle,and the binary polarization modulation method is designed based on the characteristics of the spatial light modulator.Then feasibility of this method is verified in numerical simulations and experiments,respectively.In addition,the focusing results are quantitatively evaluated by the enhancement factor.It is shown that the results obtained by the binary polarization modulation method and the binary phase modulation method are approximate,indicating that the polarization also contains important information of the original image.(3)An experimental system based on the transmission matrix method is designed to generate special beams through the scattering medium.Based on the theoretical analysis of the scalar transmission matrix through the scattering medium to generate vortex beams,the Fourier domains of the transmission matrix in the vertical and horizontal polarization directions are filtered numerically by the phase mask corresponding to the vortex beams,and then the single-polarization transmission matrix with the phase encoding of the vortex beams is obtained by the inter-correlation method.The vortex beam is successfully generated through the scattering in the numerical simulation and experiment.In addition,it’s verified that the feasibility of generating a vector beam through the scattering medium in numerical simulation,by modulating two orthogonally polarized transmission matrices with corresponding Ermey Gaussian light fields.In summary,this paper proposes to realize scattering focusing and imaging based on single polarization transmission matrix for the polarization nature after passing through the scattering medium;In addition,it realizes the manipulation of the optical field inside the medium through numerical filtering,and conducts an in-depth study on generating special beams after passing through the scattering medium,and the single-polarization transmission matrix method is discussed and explored extensively through numerical simulation and experiments system.The above conclusions have a positive effect on the further development of transmission matrix technology and the exploration and application of polarization properties.