ISLA - main idea
A saturable absorber (SA) is an optical device that exhibits an intensity - dependent transmission. In passive mode - locking, the SA will selectively absorb low - intensity light, and transmit sufficiently high intensity pulses, thus facilitating the generation of a train of ultra - short laser pulses.
Graphene possesses a nearly wavelength indepen dent linear absorption from the visible through to the far infrared, while absorbing a significant amount (2.3%) of light per s ingle layer. With a finite number of carriers in the monolayer, Pauli blocking enables graphene to exhibit optical - saturable absorption. G raphene can be saturated over the visible to near - infrared region and it has a smaller non - saturable loss and higher d amage threshold, compared with Carbon Nanotubes.
For initial experiments, d ispersions of graphene were prepared in DMF at an initial concentration of 5.0 mg/mL. The se dispersions were stable against sedimentation and displayed no further aggregation for a period of weeks. The graphene was transferred onto the end face of a fibre pigtail via optically driven deposition using a single - mode laser diode at 976 nm. The complete SA unit is produced by joining the graphene - deposited fibre pigtail and a clean fibre pigtail with a mating sleeve.