Angular distribution of polarized photon-pairs in a scattering medium with a Zeeman laser scanning confocal microscope.

A novel confocal microscope designed for use with turbid media is proposed. We use a Zeeman laser as the light source. Based on the properties of two-frequency polarized photon-pairs and the common-path feature of polarized photon-pairs with heterodyne detection employed in the proposed confocal microscope, three gatings (spatial filtering gating, polarization gating and spatial coherence gating) are thus simultaneously incorporated in the microscope. Experimental results for the angular distribution of polarized photon-pairs in a scattering medium indicate that polarization gating and spatial coherence gating preclude the detection of multiply scattered photons, whereas the pinhole selects the least scattered photon-pairs. Thus, better performance for axial resolution than can be obtained with a conventional confocal microscope is demonstrated experimentally. In addition, the proposed microscope is able to either look deeper into a turbid medium or work with a denser medium; furthermore, the axial resolution is improved.