Ultrawide dynamic bandwidth modulation of an antiresonant nanoweb hollow-core fiber

Abstract: We experimentally demonstrate an acoustically modulated antiresonant nanoweb hollow-core fiber (N-HCF) for the first time. The N-HCF contains two off-center air cores with a diameter difference of 5 microns, separated by a nanoweb of silica. We analytically simulate the influence of the N-HCF core diameter, cladding wall, and nanoweb thicknesses on the confinement losses, effective indices, and beatlengths of the guided fundamental (HE11) and higher-order modes (TE01, TM01), from 750 to 1200 nm. The phase-matching of the acoustic waves and modal beatlengths is also estimated and discussed. The fabricated 3.6 cm long acousto-optic device modulates record-wide bandwidths (up to 450 nm) while providing high modulation depths (up to 8 dB) at low drive voltages (10 V). Simulated and measured results provide useful insights for designing, modeling, and characterizing the N-HCF transmission spectrum and modulation performance. These achievements lead to highly efficient, compact, and fast all-fiber sensors and modulators promising for application in pulsed fiber lasers.