Ultrathin fiber probes with extended depth of focus for optical coherence tomography

We report on a novel scheme for extending the depth of focus (DOF) of ultrathin (125 mu m diameter) fiber probes for optical coherence tomography (OCT) using a simple phase mask consisting of graded-index (GRIN) fiber. The technique is compatible with existing all-in-fiber probe fabrication techniques, and our simulations show that it can provide a DOF gain of similar to 2 at a modest similar to 5 dB reduction of peak sensitivity. In a prototype device using commercially available GRIN fiber, a DOF gain of 1.55 is obtained, validated by beam profiling and OCT imaging. (C) 2012 Optical Society of America