Micro fabricação de placas óticas birrefringentes e suas aplicações

Abstract

We present a method for the fabrication and characterization of optical elements with nanometric periodic structures. They were created using electron beam lithography, resulting in an anisotropy of the refractive index, called form birefringence. The level of form birefringence may be controlled by altering structural parameters, such as width, depth and lling factor, allowing a stronger birefringence than the one found in natural crystals like quartz and calcite. Through the control of these parameters, the choice of the materials and wavelength for the fabrication of electromagnetic mode converters plates becomes unrestricted. Denominated q-plates, these optical plates were rst proposed and fabricated by Marrucci et al., using the process of micro-rubbing, and lled with liquid crystal, being able to demonstrate the spin-to-orbital angular momentum conversion. By using a nano fabrication procedureenabling the control of form and dimensions of the structures, in which titanium dioxide was precisely deposited on the surface of a glass plate, it was constructed a new version of q-plates without the necessity of liquid crystal. The characterization of the optical elements fabricated was made analysing intensity values and proles in an asymmetric Mach-Zehnder interferometer. It is possible to notice fringes with peculiar characteristics, showing the helicity of wave fronts of the generatedbeams, in a way to be observed phase gain and orbital angular momentum transfer.