Poster Effects of surfactant concentration in carbon nanotube polymer composite for ultrafast fibre laser

Abstract

Saturable absorbers (SAs) based on nonlinear optical absorption plays a key role in achieving ultrashort laser pulses in a fibrelaser system. Among these, carbon nanotubes (CNTs) based SAs serves as an excellent candidate to ensure stable modelocking.Numerous approaches using CNT have been developed to enhance the nonlinear interaction, maintaining the all-fibreconfiguration. For example, a hollow core1 or D-shaped fibres2 can be employed. However, these methods expand the lasersystem, increasing the final cost, or reduce the integrity of the all-fibre structure. CNT polymer composite fabricated fromeffective dispersion of CNT in solvent offers a very convenient approach3. Usually, the CNT powder is mixed with surfactantand dispersed in water followed by ultrasonication and centrifugation. After centrifugation, the resultant solution is mixed withpolymer and poured in the Petri dish to obtain the CNT polymer composite via drying the sample in the desiccator.During the CNT SA preparation procedure, the ratio between CNTs powder and surfactant is critical which would helpefficient dispersion of CNT in solvent preventing agglomeration in the later steps. However, there has no report so far on theeffect of surfactant concentration in CNTs polymer composite on an ultrafast fibre laser performance.In order to study this effect, we have produced set of CNT polymer composites with 0.2% CNTs and different surfactantconcentration. The samples thus obtained were characterized by optical microscopy, and applied in an Erbium doped ultrafastfibre laser system.Based on the results obtained, we can conclude that all samples ensure comparable generation of 700-fs pulses with theaverage power of 17mW at 200mW pump power. Though, samples with 0.5% and 1% surfactant demonstrate only partial modelocking,whereas the sample with 2% surfactant maintains stable (for 24hours) ultrashort pulse generation even at remarkablehigh output power of 50mW.