Photonic Crystal Mikaelian Lenses and Their Potential Use as Transverse Focusing Elements in Microstructured Fibers

We numerically studied the focusing properties of a special type of graded index photonic crystal media, i.e., the so-called photonic crystal Mikaelian lenses (PCMLs). We considered PCMLs with a varying air hole diameter and with a varying air hole pitch in hexagonal and rectangular lattices, and we compared their frequency response and polarization dependence. Our eventual objective is to design microstructured optical fibers equipped with a PCML in their cladding region adapted to allow for more efficient femtosecond laser grating inscription. Therefore, we have also evaluated the possibility of using such lenses as transverse focusing elements in microstructured optical fibers.