In the last years inorganic semiconductor (particularly CdSe and CdS) quantum dots (QDs) have received great attention
for their important optical properties. The possibility to tune the emission wavelength, together with their high
fluorescence quantum efficiency and photostability, can be exploited in photonic and optoelectronic technological
applications. The design of DFB devices, based on QDs as active optical material, leads to the realization of compact
laser systems. In this work we explore the use of an inorganic/organic hybrid material composed of CdSe-ZnS
semiconductor quantum dots doped into a zirconia sol-gel matrix for optical gain applications. Through the use of soft
lithography on a sol-gel germania-silica hybrid, large scale distributed feedback gratings can be created. Used in
conjunction with the CdSe-ZnS/ZrO2 hybrids, these gratings can act as microcavities and allow for the realization of true
lasing action. The lasing properties within these devices are characterized in the femtosecond regime by both one- and
two-photon excitation. From experimental data the value of the optical gain of the core-shell quantum dot samples has
been estimated. Moreover, one- and two-photon lasing threshold and stability are reported.
Two and three dimensional structures with micron and submicron resolution have been achieved in commercial resists,
polymeric materials and sol-gel materials by several lithographic techniques. In this context, silicon-based sol-gel
materials are particularly interesting because of their versatility, chemical and thermal stability, amount of embeddable
active compounds. Compared with other micro- and nano-fabrication schemes, the Two Photon Induced Polymerization
is unique in its 3D processing capability. The photopolymerization is performed with laser beam in the near-IR region,
where samples show less absorption and less scattering, giving rise to a deeper penetration of the light. The use of
ultrashort laser pulses allows the starting of nonlinear processes like multiphoton absorption at relatively low average
power without thermally damaging the samples.
In this work we report results on the photopolymerization process in hybrid organic-inorganic films based
photopolymerizable methacrylate-containing Si-nanobuilding blocks. Films, obtained through sol-gel synthesis, are
doped with a photo-initiator allowing a radical polymerization of methacrylic groups. The photo-initiator is activated by
femtosecond laser source, at different input energies. The development of the unexposed regions is performed with a
suitable solvent and the photopolymerized structures are characterized by microscopy techniques.
We present the design, synthesis, and characterization of a class of heteroaromatic bichromophores in order to investigate intermolecular interactions and their effect on optical and nonlinear optical properties. As a design strategy we have linked two dipolar or quadrupolar units through a non-conjugated alkyl chain. The two units are connected either through their donor or their acceptor end-groups. This study represents a first step towards the design of bi- and multichromophoric systems with optimized NLO responses in order to exploit collective and cooperative effects from interchromophore interactions.
In this work we report on the study of the photopolymerization process in hybrid organic-inorganic films containing photopolymerizable acrylic and methacrylic groups and. The films are doped with a proper photo-initiator for radical polymerization of (meth)acrylic units and are prepared using the sol-gel technique.
The photo-initiator is activated by using continuum (single-photon polymerization) or pulsed (two-photon polymerization) laser sources at different wavelengths. After the development of the unexposed regions with a suitable solvent, the photopolymerized structures are observed with microscopy techniques. The effects of the composition of the photopolymerizable mixture, the irradiation parameters (laser power and exposure time) and the external atmosphere in which the photopolymerization is performed are investigated.
The fabrication of 3D microstructures using multiphoton absorption processes is a promising technique that involves low amount of incident exposure dose with potentially high spatial resolution.
Organic-inorganic hybrid materials, composed of inorganic oxide structures and interpenetrated cross-linked organic
polymers, are promising candidates for electro/optical applications, combining the most important glasslike and
polymerlike properties. This is particularly true when large laser power density is used: these materials show high laser
damage resistance compared with that of polymeric systems.
A deep study of effects and causes of laser damage has never been done, especially for hybrid materials. The
mechanisms of optical damage depend on different factors like laser experimental parameters, such as pulse duration,
beam size and wavelength, or the microstructural characteristics and defects of the material.
Hybrid materials possessing desired shapes and optical and mechanical properties are well synthesized by the sol-gel
technique. The use of Glycidoxypropyltrimethoxysilane (GPTMS) allows preparing heterogeneous and resistant
materials, with good optical properties.
Different sol-gel matrices have been prepared in order to study their laser damage resistance. The possibility of varying
the catalysts and precursors or the synthesis protocol allows obtaining materials with similar chemical composition and
different microscopical properties. By this way, it is possible to study the laser damage threshold of these samples and to
find the way to enhance and optimize the laser damage resistance, useful in non-linear optical devices.