Widely tunable dual acousto-optic interferometric device based on a hollow core fiber

TL;DR

This paper demonstrates a novel all-fiber dual Mach-Zehnder interferometer using an acoustically modulated hollow-core fiber, enabling precise frequency tuning for advanced optical applications.

Contribution

It introduces a new acousto-optic modulator design within hollow-core fibers that allows for widely tunable interferometric devices with potential for multiwavelength filtering and sensing.

Findings

Achieved frequency tuning of the MZI by 1 Hz increments.

Enabled control over the coupling between fiber modes.

Simulated and analyzed modal interactions and spectra.

Abstract

An all-fiber dual Mach-Zehnder interferometer (MZI) based on an acoustically modulated hollow-core fiber (HCF) is experimentally demonstrated for the first time. By attaching an acoustic driver in between the fixed ends of an HCF, we fabricated two acousto-optic modulators (AOMs) with distinct driver positions, allowing for synchronizing two in-line MZIs inside the HCF. The first MZI is set by two acoustic long-period gratings separated by a second MZI formed at the fiber and driver attaching region. We show that this setup enables frequency-tuning of the coupling between the fundamental and higher-order modes in the HCF. Additionally, we simulate and analyze the HCF modal couplings and MZIs' modulated spectra under distinct device parameters using the transfer matrix method. The new AOM-MZI enables tuning of the MZIs free spectral range by adjusting 1 Hz of the electrical frequency, which is promising to modulate multiwavelength filters, sensors and fiber lasers.