Study On Super - Resolution Optical Microscopy Of Semi - Immersion Microspheres

Beating Abbe’s diffraction limit has become one of the hottest research topics in photonics. Recently, microscale spherical lenses are found to have the ability of super-resolution, which can be used to enhance the resolution of a conventional optical microscope. Moreover, when a microscale spherical lens is semi-immersed in a medium, the quality of its super-resolution imaging can be significantly improved. In this thesis, we have researched on the imaging properties of semi-immersed4.87μm diameter silica spherical lenses. We have also introduced a self-assembly method to fabricate centimeter-sized arrays of spherical microlenses, in order to achieve large-area super-resolution imaging。First, the far-field imaging properties of a semi-immersed microscale spherical lens are experimentally studied, when the microscale spherical lens is spatially separated from the object. Our experimental results show that, when the lens is separated from the object, the semi-immersed microscale spherical lens can magnify the stripe patterns of a blu-ray disc, whose spacing is300nm. When the distance between the lens and the object is increased from0to14μm, the magnification of the lens decreases from1.47x to1.20x and the field of view increases from3.8to12.2μm. Interestingly, all the images are below the object in the experimentally tested range. The imaging properties cannot be described by geometrical optics.Second, we research a new physical phenomenon experimentally observed in the semi-immersed microscale lens imaging. In standard geometrical optics, depending on the relative position between an object and a lens, either a real or a virtual image is formed. However, we find that when a microscale spherical lens is semi-immersed in a medium, the microscale lens can form both a real image and a virtual image. Our findings will advance the understanding of the super-resolution imaging mechanisms in microscale lenses.Third, we have developed a gravity-assisted convective self-assembly method to fabricate arrays of spherical microlenses. In this method, centimeter-sized monolayer of hexagonal microlens arrays can be formed when the suspension concentration is in the range of0.32-2.5wt%. Experimental results show that, gravity plays an important role in the microlens arrays formation. In this method, the microspheres are transported to the edge of the suspension-glass interface, and then the extra particles can be moved to the edge of the slide by gravity, which eventually lead to the formation of monolayer microlens arrays.