• Random Lasing
• Nanofibers
• Nanofibers network
• 3D printing
• Electrospinning

Recently novel laser systems have been introduced (known as random lasers) in
which light amplification occurs through light diffusion in a disordered medium
with optical gain. Unlike conventional lasers, the emission of random lasers is a
consequence of multiple scattering, and they typically feature multimode emission.
The objective of this work is the realization of hybrid samples made of
3D structures and arrays of light-emitting nanofibers (NFs) with random lasing properties.
The apparatus built for the scope of this thesis has two separate printing and electrospinning (ES)
heads, while the sample platform is moved automatically from one to the other depending on the features of the samples to be realized.
In the first part of the work, the two printing stations were separately studied and the corresponding samples characterized.
For the realization of NFs, solutions with different concentrations of poly(vinyl alcohol) in distilled water were electrospun.
In the second part of the work, the deposition of NFs was optimized on top of 3D
printed structures.
Rhodamine B was added to PVA/water solution
as the chromophore, in order to obtain electrospun fluorescent NFs.
Then, samples with fibers suspended through a 3D printed
frame were realized. This geometry was selected because it allows a better confinement of light emitted by the dye in the electrospun fibers, due to the refractive index
contrast between the PVA polymer and the surrounding air.
Finally, the optical properties of the samples were investigated by optical pumping
with a Nd:YAG laser. Through such measurements the threshold excitation fluence
can be determined. Moreover,
a dependence of the lasing emission spectrum on the spatial intensity profile
of the excitation beam was observed.