Design of Single-Band Bandpass Filter Using Photonic Bandgap Fiber by Suppressing Core Modes in Higher Order Bandgaps

We present two designs of all-solid photonic bandgap fiber (PBGF) for higher order bandgap suppression to realize a unique transmission window for optical filtering purposes. These two approaches are based on either applying a low-refractive-index core or a high-refractive-index background. This paper describes direct calculations of different modes in high-index rods in the all-solid PBGF using the antiresonant reflecting optical waveguide model for a double-cladded step index fiber. The flat-top single-band bandpass filter was obtained with potential center wavelength over ultraviolet, visible, and infrared regions. We achieve the single-band bandpass filter with minimum passband-to-rejection-band ratio of 20 dB in core power. From the calculated performance, both analytical and simulation results are in good agreement with confinement loss calculation.