Mode-field expansion in photonic crystal fibers

Abstract

We propose two novel methods to make mode-field expanders using photonic crystal fibers (PCFs). By heating and collapsing the center rings of airholes around the core using the selective airhole collapse technique, we enlarge the core of the fibers and get mode-field expanders. Meanwhile, by heating and controlled shrinking all airholes of the PCFs, power confinement in the core will decrease and the mode-field diameter of the fibers will be enlarged, too. Both methods are studied in theory and experiment.