The Focusing Properties And Focus Control Of Vector Beams

With the rapid development of laser and relevant technology, laser is not only promoting the science, but also playing a more and more important role in many aspect of our daily life. How to take better advantage of laser has become a new issue. The character of light involving the phase, frequency and amplitude have been deeply explored and put into lots of applications. However, the character of polarization has not got people’s attention until recently. Due to its complicated polarization and special properties, the focusing properties and polarization evolution of vector beams has attracted more and more interest recently while vector beams and its properties have already been used widely in fields like optic trapping and optic micromanipulation. However, the conception of vector beams is still new to many people and the research on it is not sophisticated yet. There remain many scientific and technological problems to be solved. This dissertation is mainly focused on the focusing properties and polarization evolution of vector beams. The main contributions of this dissertation are as follows:1.The generation of vector beams. The general methods to generate vector beam include two categories-the active way and passive way. Different methods to generate vector beams are discussed, especially a convenient approach for generating arbitrary vector beams in a 4f system with a spatial light modulator(SLM) and a common path interferometric arrangement, as well as a new way of replacing one-dimensional holographic gratings with two-dimensional ones.2.The focusing properties of vector beams. We study the mathematical derivation of the Richards-Wolf vector theory, which is commonly used to calculate the focal properties. Based on that, we discuss the focusing properties of some typical vector beams, such as linearly polarized beam, radially and azimuthally polarized beam and spatial-variant vector beam.3. Polarization evolution characteristics of focused hybridly polarized vector fields. We investigate both theoretically and experimentally the focusing property and polarization evolution characteristics of focused hybridly polarized vector fields. Three types of hybridly polarized vector fields, namely azimuthal-variant hybridly polarized vector field, radial-variant hybridly polarized vector field, and spatial-variant hybridly polarized vector field, are successfully generated and studied. The intensity distributions and 3D polarization distributions of these focused spatial-variant hybridly polarized vector fields are controllable through adjusting the parameters of the phase modulation.4. Focusing properties of asymmetric-sector-shaped vector beam. We investigate the particular focusing properties of asymmetric-sector-shaped vector beam with localized linear polarization. We have theoretically and experimentally demonstrated that the shape-only modulation of the vector beam allows one to simultaneously change the intensity, phase, and polarization, as well as SAM distributions at the focal plane.