Control of structured light beams focusing through anisotropic multiple-scattering media via multi-focus-based digital optical phase conjugation

Abstract

A framework to focus structured light beams through an anisotropic multiple-scattering medium (AMSM) with multi-focus-based digital optical phase conjugation is proposed. In this work, the measured full vector transmission matrix (VTM) in conjunction with a well-designed multifocal target field can be used to calculate the required input field, which consists of two orthogonally linear polarization components. The polarization, amplitude and phase of the light before and after the AMSM are then shaped and controlled by encoding the input field into a double-channel computer generated hologram that is displayed on a vector spatial light modulator. The desired output field composed of multifocal spots can be obtained through the AMSM. We demonstrated several examples, generating vector beams, array vector beams and vortex beams, to experimentally validate the feasibility of our approach. Additionally, the peak to background ratio (PBR) of the generated multifocal structured light can be predicted theoretically by introducing the idea of critical focus number. The simulated and experimental results show that the generated structured light with a clear optical ring and high PBR can be realized through the AMSM. Consequently, our method provides an effective way to control and optimize structured light beams focusing through the AMSM.