Hollow core large mode area fiber employing a zero contrast subwavelength grating reflector

We propose a hollow core large mode area fiber with a new type of guiding mechanism. The fiber is based on a zero contrast high refractive index subwavelength grating embedded on a silica cladding. The hollow core exhibits guided mode resonance for incident waves on a circular grating, thus acting as a highly reflective circular mirror. Finite element simulations are utilized to demonstrate low leakage loss near the guided mode resonances and to investigate the corresponding mode profiles and the reflectivity spectra. We also present alternative high-contrast self-suspended grating and compare the results.