Third-order nonlinear optical studies of carbon nanotubes developed by floating catalyst technique

Carbon nanotubes were developed via floating catalyst technique using acetylene and ferrocene as carbon and catalyst precursors respectively at temperatures varying from 700 to 1150 °C. Structure and morphology were characterized via SEM, TEM and Raman spectroscopy. The dimensions and yield of grown CNT's were observed to be same in all temperatures. The crystalline perfection of CNT's was improved with an increase in temperature. It is observed that the temperature of the synthesis could affect the degree of nanotubes graphitization. Catalytic growth of CNT's was elucidated on the basis of the model of vapour-liquid-solid and the proposed model was supported by TEM. Growth rate of nanotubes rises at higher temperatures and graphite sheets builds with lower defect. Nonlinear optical and limiting characteristics were determined using ns pulses at 532 nm. CNT's display strong nonlinear absorption coefficient of 29.9 cm/GW. CNT's exhibiting excellent optical limiting with a limiting threshold of 3 J/cm 2.