Saturable absorption of multi-walled carbon nanotubes/hybrid-glass composites

The saturated optical absorption of multi-walled carbon nanotube (MWNT)-doped hybrid-glass composites was studied at 1064 nm with nanosecond long pulses using the Z-scan technique. Increased transmission was demonstrated for high intensity pulses. The results were modeled for the limiting cases of a slow or a fast saturable absorber, both referring to a three-level system. The ground-state absorption cross section was estimated as 2.3x10(-18) cm(2), in good agreement with that of a single carbon atom. The excited state absorption cross section for carbon nanotubes (CNTs) was estimated for the first time as 6.9x10(-19) cm(3). The absorber's density of 2.8x10(18) cm(-3) is smaller by approximately a factor of 5 compared to the nominal density of carbon atoms incorporated into the glass. This could be a result of the broad band-like states formation in the MWNTs. The above figures were obtained by assuming that the excited state decay time was longer than the pulse duration of similar to 1 ns. (C)2012 Optical Society of America