Nonlinear Optical Phenomena and Photonic Materials

The increasing demand for faster processing, storage and distribution of information can only be achieved by miniaturisation of the basic electronic devices down to the atomic/molecular level. Opto-electronic/photonic technologies, where light is used as information carrier instead of electrons, is expected to offer an answer. Towards this goal, the development of new photonic materials possessing suitable linear/nonlinear optical response for such tasks are of high interest.

Our research efforts are oriented towards:

• the understanding of the physical origins of the NLO response
• the systematic study of the relationship between molecular structure and NLO response
• the tailoring of the NLO properties in order to match specific needs (e.g. 2- or 3-photon absorption, nonlinear refraction, χ⁽³⁾, n₂, 2^nd hyperpolarizability, etc.)

Some examples of materials of interest:

• Graphene(s) and graphene derivatives: structure/functionalization and NLO response
• Defect engineering and doping of graphene for tuning their NLO response: the case of fluorographenes
• Other 2D materials (e.g. Silicenes)
• Polycyclic Aromatic Hydrocarbons (PAHs) and nanoribbons
• Charge transfer/π-π interactions and NLO response: fullerenes, functionalized fullerenes (e.g., with porphyrins, ferrocenes, etc.), fullerene dendrimers, endohedral fullerenes
• Metal (e.g., Ni, Pt, etc.) dithiolenes  
• Molecular nano-machines & molecular shuttles (e.g. rotaxanes)
• Azo-benzene systems, cis-trans isomerization and NLO response
• Metallic and semiconductor nanoparticles
• Plasmonic nanoparticles and nano-alloys (effects of: size/shape, ordering/dis-ordering, functionalization, local environment, on their NLO response)

Graphene, being an one-atom thick single layer of sp²-bonded carbon atoms arranged in a honeycomb lattice, is a perfect two-dimensional (2D) material, exhibiting many surprising and unique physical/electronic/optical properties, which originate from its unusual electronic structure. These unexpected properties made it an attractive candidate for numerous applications.

As a result, it has greatly attracted the research interest of the scientific community.

So, very soon after its first isolation, several research activities have been oriented towrds the design/synthesis of various modified graphenes and graphene derivatives, oriented towards various potential applications in several technological and scientific areas.

The ability of tailoring/controlling graphenes’ properties, especially the modulation of the band gap, the engineering of the defects, the modulation of the ratio of the sp2/sp3 domains, the decoration of graphenic plane with specific chemical groups or nanoparticles, etc. have largely extended the functionalities of these 2D materials.

Among them, the linear and nonlinear optical properties arising from the interaction of light with these 2D materials are of high interest as they are closely linked with the fundamental physical knowledge, while they are key parameters for the design and development of novel photonic materials and devices.

Some of our most recent works regarding the nonlinear optical and optical limiting properties of graphene derivatives of interest regard:

• graphene oxide
• graphene fluoride or fluorographene
• hydrogenated fluorographene
• diethylamino-fluorographene
• methoxythiophenol- and dimethylamino- fluorographene
• octylamine- fluorographene
• other derivatives (nitrile-, arginine-, pentyl-, allyl-, isophtalic acid graphene, etc.)

and more.