Long-period fiber grating as wavelength selective element in double-clad Yb-doped fiber-ring lasers

TL;DR

This paper demonstrates how long-period fiber gratings can be used as wavelength-selective elements to control the operating wavelength of Yb-doped fiber-ring lasers, achieving broad spectral tuning and high power handling.

Contribution

It introduces a novel method of using customized LPFGs as broad-band rejection filters to tune laser wavelengths, including the shortest LPFG period reported with CO2 laser inscription.

Findings

Achieved spectral oscillation range of 1050-1110 nm.

Successfully inscribed LPFGs with periods down to 175 μm.

Demonstrated wavelength tuning by modifying LPFG design and fiber length.

Abstract

Selection of operating wavelength of the Yb-doped fiber-ring lasers using longperiod fiber gratings (LPFGs) is suggested. In the proposed method, customized LPFG that sustains high powers serves as a broad-band rejection filter. It modifies the net gain profile of the laser, enabling the peak gain to occur at a designed wavelength. Spectral range of oscillation between 1050-1110 nm was experimentally demonstrated. This range can be extended to both shorter and longer wavelengths with proper design of the LPFG and length of the Yb-doped fiber. The gratings were inscribed by CO2 laser and the grating period down to 175 ?m was achieved being, to our best knowledge, the shortest reported LPFG period using this technique.