Sodium carbonate modulated ultrashort mode-locked stretched pulses in an erbium-doped fiber laser.

In this paper, we propose a new, to the best of our knowledge, saturable absorber (SA) based on sodium carbonate ( ) for producing an ultrafast mode-locked stretched pulse in a passively erbium-doped fiber laser at near-zero dispersion. The solid film of a -SA was fabricated by the drop-casting method using polyvinyl alcohol as a host polymer. The modulation depth of the proposed SA, which was measured by a balanced twin detector technique, was 2.