Fabrication, characterization and mode locking application of single-walled carbon nanotube/polymer composite saturable absorbers
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?m, 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?J/cm2 and a modulation depth ?16.9% (in absorption) at a high pulse fluence ?200?J/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 ?1ps 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 ?560fs 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.
carbon nanotube saturable absorber nonlinear optical properties