Optically trapped and controlled microapertures for studies of spatial coherence in an arbitrary light field

By controlling the rotation rate of a trapped birefringent particle with an optically applied torque, the authors introduce a miniscule wave front deformation at a specific location within an arbitrary light field, with the particle acting as an optical microdiffuser. A trapped birefringent particle and a trapped silica microsphere are positioned to form Young's double slit experiment within a probe light field. The far-field interference from the diffracted optical fields from these particles enable the authors to infer the relative spatial coherence between these local sampling points. With multiple trapped particles, the authors may perform multipoint coherence analysis of a light field.