  We propose to use high numerical aperture single mode optical fibers like
photonic crystal fiber for lensless in-line holographic microscopy. Highly
divergent beam helps to overcome the spatial sampling limitation of the image
sensor. In this paper, a submicron lateral resolution has been demonstrated,
with an imaging sensor of pixel pitch 1.12 micrometer and a photonic crystal
fiber of mode field diameter 1.8 micrometer. In earlier methods of single-shot
lensless imaging, submicron resolution has been obtained at very small working
distance and field of view. The proposed method improves the resolution without
compromising the working distance. A working distance of (but not limited to)
~1.7 mm with a field of View ~1.4 mm has been demonstrated.
