Passively Q-Switched Erbium Doped Fiber Laser Using Nanomaterials

A passively Q-switched Er-doped fiber laser (EDFL) with ring cavity operating at 1568.6 nm was demonstrated using a saturable absorber (SA) based on double walled carbon nanotubes (DWCNTs) film, which was prepared using polyvinyl alcohol (PVA) as a host polymer. The Q-switching operation was achieved at a low pump threshold of 40 mW. The proposed fiber laser produced stable pulses train of repetition rate ranging from 14.7 KHz to 47 KHz as the pump power increased from threshold to 203 mW. The minimum recorded pulse width was 4.6 µs at 203 mW while the highest energy obtained was 102.1 nJ. The concentration effect of multi-walled carbon nanotubes (MWCNTs) dispersed in PVA polymer matrix was experimentally investigated as an SA to stabilize the Q-switching performance of ring cavity EDFL. A shortening in the pulse width ranging from 4.6, 4.4 to 4 µs corresponding to an increase in MWCNTs¿ SA concentration of 0.25, 0.5 and 0.75 wt% was obtained. The Q-switched EDFL output was very stable as the MWCNTs¿ concentration increased from 0.5 to 0.75 wt%, while the lowest MWCNTs concentration 0.25% showed a noticeable instability.