Mode-locked lasers are used for a vast amount of applications, e.g. corneal
surgery and optical data storage . The currently established technique for
mode-locking with a semiconductor saturable absorber mirror is expensive and in-
volves a fairly advanced production technique . Carbon nanotubes incorporated
into thin plastic films present an easy to produce and comparatively cheap alter-
native. These films are produced by solving carbon nanotubes in a proper solvent,
mixing with a host plastic material and finally spin coating to a substrate. Earlier
studies have successfully produced and used carbon nanotube thin film saturable
absorbers for mode-locking, most notably in the near infrared spectral region .
In this work, different solutions are produced using different solvents and varying
the carbon nanotube and plastic ratios in these solutions. The different solvents used
were toluene, 1,2-dichlorobenzene and acetone. Another fabrication parameter is the
revolutions per minute used during the spin-coating process. and the revolutions
per minute varied between 500-1250. A total of 17 different solutions was prepared,
and spin-coated onto glass substrates with different revolutions per minute.
Although proper mode-locking could not be achieved for most of the samples
the best solvent seemed to be 1,2-dichlorobenzene which is used in other studies as
well[5, 6] . As a result of the laser’s output, which shows modulation, a conclusion
of that the sample has non-linear absorber properties can be made. A tendency for
q-switching was also observed, however, this operation is unstable in terms of repeti-
tion rate. To be able to get desired laser behavior the modulation introduced by the
absorber has to be adjusted, by altering e.g., the film’s thickness or carbon nanotube
concentration. No proper mode-locking was observed for toluene regardless of the
concentration of solvent or carbon nanotubes.
2011. , 16 p.