The Nonlinear Properties of Single-Walled Carbon Nanotube Saturable Absorber at E11 and E22 Transitions

Abstract

In this paper, we compare the nonlinear optical properties and suitability of small (∼0.8 nm) and large diameter (∼1.4 nm) single wall carbon nanotubes (SWCNT) for fiber laser mode-locking near the technologically important 1 μm wavelength. We measured the nonlinear modulation depth ant saturation fluence in 1030–1070 nm wavelength interval, which is close to the first excitonic transition (E11) of small diameter SWCNTs. We verify, that small diameter SWCNTs are beneficial for fiber laser mode-locking at the 1064 nm wavelength as they have much lower saturation fluence (F sat, 11 = 8 μJ/cm2) than larger diameter SWCNTs — (F sat,22 = 329 μJ/cm2) working at E22 transition. The bulk absorption of small diameter (∼0.8 nm) nanotubes consists of superposition of absorption narrow optical absorption lines of SWCNTs with different chirality