Multifunctional mesogenic microparticles: optomechanics and photonics

Abstract

The development of efficient and cost-effective micromachines is a challenge for applied and fundamental science given their wide fields of interest. Light has become a suitable tool to move small objects in a non-contact way, given its capabilities in exerting forces and torques. However, when complex machining is required, the assembly of micro-objects with proper architecture able to play a specific role in the dynamics, is extremely helpful. To this aim, the design of opto-responsive micrometric devices was carried out by exploiting the dielectric-metal coupling. Such structures are able to couple with different forces carried by the optical field, and selectively acquire orbital and rotational momentum, depending on the presence of a raspberry-like gold nanoparticles shell. Furthermore, the particles can have a chiral supramolecular structure due to the cholesteric nature of the mesogenic precursor. This allows the study of collective optomechanical phenomena and to the use of these as laser resonance cavities. The study, therefore, of how these microparticles under appropriate structures of the field are able to couple with it, giving rise to the birth of collective phenomena of angular momentum transfer. The addition of fluorescent molecules in the polymeric core enables laser emission and demonstrate higher resistance to degradation of the core-shell particles, which represents the current limit of similar organic microresonators. Bragg and whispering gallery emissive modes were observed and an increase in operating cycles was obtained. 6 The thesis is completed with a detailed part concerning the production protocol and variants useful for obtaining versatile structures in both photonic and optomechanical fields. A profound characterization was carried out in order to appropriately exploit the different properties offered by this technology.