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

Focusing Light with Curved Guided-Mode Resonance Reflectors

Employing numerical simulations, we investigate the possibility of using curved guided-mode resonance (GMR) elements to focus light in reflection. We treat GMR reflectors with a parabolic shape and show that they are capable of focusing light effectively across wavelength bands that extend several hundred nanometers. The spatially infinite reflector model is simulated with a finite-element method, whereas the spatially finite reflector is treated with a finite-difference-time-domain method. The numerical results demonstrate that light intensity at the focal point is 8.6 dB stronger than the incident intensity when the GMR reflector’s size is on the order of 10 wavelengths. The results indicate potential applicability of wideband-focusing devices in electromagnetics and photonics using compact resonance elements