Optically induced mode conversion in graded-index fibers using ultra-short laser pulses

TL;DR

This paper demonstrates efficient, broad-wavelength optically induced mode conversion in graded-index fibers using ultrashort laser pulses, enabling all-optical modulation with preserved pulse shape.

Contribution

It introduces a novel method for mode conversion in graded-index fibers using ultrashort laser pulses and long-period gratings, with high efficiency and broad wavelength applicability.

Findings

High-efficiency LP 01 to LP 11 mode conversion achieved.

Mode conversion observed over 1100nm to 1800nm wavelengths.

Pulse shape preserved during mode conversion.

Abstract

We propose the use of graded-index few-mode fibers for mode-conversion by long-period gratings (LPG) transiently written by ultrashort laser pulses using the optical Kerr effect. The mode inter- action is studied by numerically solving the multi-mode coupled nonlinear Schroedinger equations. We present highly efficient conversion of the LP 01 - into the LP 11 -mode preserving the pulse shape in contrast to previous results in step-index fibers. Furthermore, mode conversion using different wavelengths for inducing and probing the LPG is shown. Due to the flat phase-matching curve of the examined modes in the graded-index fiber, mode-conversion can be observed for probe center wavelengths of 1100nm up to 1800nm with a write beam centered around 1030nm. Therefore, a complete separation of the probe from the write beam should be possible as well as the application of optically induced guided mode conversion for all optical modulation across a broad wavelength range.