Fabrication, characterization and mode locking application of single-walled carbon nanotube/polymer composite saturable absorbers
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We present the fabrication of a high optical quality single-walled carbon nanotubes (SWNTs) polyvinyl alcohol (PVA) composite film. The composites demonstrate strong saturable absorption at ∼1.5 μm, the spectral range for optical communications. By measuring the nonlinear transmission of a sub-picosecond pump pulse through the film, we were able to deduce a saturation fluence of ∼13.9 μJ/cm2 and a modulation depth ∼16.9% (in absorption) at a high pulse fluence ∼200 μJ/cm2. Transient saturable absorption is investigated by measuring the transmitted autocorrelation traces at various incident power levels. Observed side-peak suppression indicates a fast recovery time on the scale of ∼1 ps for our saturable absorber devices. Furthermore, we use these SWNT-PVA composite saturable absorbers as mode-lockers in an Er3+ fiber ring laser and achieve ∼560 fs pulse generation with good jitter performance and long term stability. The laser performance is also associated with the parameters of our SWNT based saturable absorber.
KeywordsCarbon nanotube Saturable absorber Nonlinear optical properties
We thank F. Hennrich for providing laser ablation nanotubes. We acknowledge funding from Advance Nanotech Inc., EPSRC grants GR/S97613/01, EP/E500935/1, ETRI Ministry of Information and Communication, Republic of Korea, Project No. A1100-0602-0101, A. C. F. from the Royal Society and The Leverhulme Trust.
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