Chirped fiber Bragg gratings directly inscribed by a femtosecond laser in an ytterbium-doped fiber for spectrum recovery, loss compensation and effective use in a CPA scheme

Abstract

Point-by-point femtosecond laser inscribed chirped Bragg gratings are good candidates for use in fiber chirped pulse amplification systems due to the high flexibility of their dispersion properties, low cost, and no length limitation. However, such gratings have two significant drawbacks: high losses and distortions of the short-wavelength part of the spectrum when operating in the normal group velocity dispersion mode. We propose a novel approach based on writing such gratings in a highly doped active fiber, which allows us to correct both shortcomings. We have also demonstrated, for the first time to our knowledge, a successful use of such gratings as stretchers in a fiber chirped pulse amplification system.