Microfabricação de dispositivos ópticos integrados por meio de escrita direta a laser

Abstract

The three-dimensional microfabrication via direct laser writing techniques has opened a window of opportunities for research and technological applications in several areas such as optical communication, microfluidics, synthesis of new materials, 3D scaffolding for cell culture, construction of optical microdevices, and others. The possibility of building a 3D optical device directly on substrate or inside a transparent bulk has driven research groups and engineers around the world to design and develop integrated micro-optical systems capable of manipulating light signals and making them interact with mechanical, electronic, fluid, chemical and biological elements. The aim of our work was to use the ultrafast laser microfabrication to construct micro-optical devices able to modulate and guide structured light beams, in particular those possessing orbital angular momentum. This thesis comprises some of works developed with that purpose and that presented very significant results: (i) Initially, the two-photon polymerization technique was used to write a binary helical axicon, a light micro-modulator able to convert Gaussian beams into structured beams possessing orbital angular momentum, whose profile is described by a superposition of high-order Bessel beams. (ii) By means of a modifying laser process, we have written channel waveguides inside silverdoped tellurite glassy blades. The waveguide’s optical properties and the writing parameters were analyzed as a function of the matrix composition and of the silver nanoparticles concentration. (iii) Finally, we have built annular waveguides inside boro-aluminosilicate glassy blades. After characterization, we showed that these structures are able to guide optical vortex beams and their superpositions. In addition, we have proposed a coupling method that permits tuning the guided modes for the same waveguide and no need to modify the input beam. Our findings expand the available degrees of freedom for optical beams in photonic circuits, simplify the design of integrated optical chips and broaden the spectrum of possible applications for these systems.