Ultra-wide bandwidth all-solid specialty bandgap fiber for ultrashort pulse delivery

Abstract

Photonic bandgap (PBG) fibers provide a versatile platform for ultra-short pulse delivery with low-loss, and low dispersion. Precisely, Braggkind of 1D PBG fibers with periodic cladding bilayers offer ample degrees of freedom to tailor fiber bandwidth along with loss, and dispersion. In this paper, we propose a next-level specialty bandgap fiber with multiple concentric cores based on the 1D PBG geometry in an all-solid form. It has three sets of tailored bilayer thickness in which each set of bilayer forms an effective core region that allows confinement of specific range of wavelengths. Thus, the successive overlap of the wavelength ranges supported by each of these concentric cores effectively enhances the overall transmission bandwidth of the fiber. Moreover, the concept can be extended to form a large number of concentric cores that allows further enhancement of the fiber bandwidth. As a proof-of-concept, an ultra-wide low-loss bandwidth covering a wavelength range of ~ 1600 nm for the fundamental mode has been achieved. Going beyond, an advanced level customization of the proposed fiber geometry has enabled further minimization of loss and enhancement in structural robustness. The propagation dynamics of an ultrashort pulse ~ 300 fs have been investigated numerically in both the normal and the anomalous dispersion regime of the proposed specialty fiber in the presence of nonlinearity and loss. Eventually, such all-solid multicore large-bandwidth fiber is proposed as a promising candidate for the delivery of ultrashort optical pulses over long distance with minimum amount of distortion and wave-breaking possible.