Spatial Manipulation Of Vector Light Fields And Its Applications To Focus Shaping

With the rapid development of laser technology, information acquisition and processing with the help of polarized light plays a more and more important role in the modern scientific and technological research. To fully take the advantage of photon, which acts as the carriers of information, the key issue is how to manipulate the optical field. The light’s characteristic parameters including the phase, frequency and amplitude have been deeply explored and widely used. The conventional manipulation way of light, such as tailoring of the phase and amplitude, has significant application in the field of the information processing. Due to their particular vector properties, the vector fields with the space-variant polarization state have attracted more and more interest in recent years and the research of vector fields has been paid more and more attention. The inhomogeneous polarization distribution of vector field makes a great impact on the spatial-temporal evolution and the interaction of light with matter and many novel phenomena and effects come from the impact. Furthermore, the extraordinary properties of the tightly focused field of these vector have attracted an increased interest and been extensively explored in recent years. The finding of new phenomena, novel effects and potential applications impose deep impact to the current science and technology.This dissertation is focused on the generation, optical properties and manipulation of vector beams, and the application to focus shaping, and is devoted insightful research on some novel effects from vector fields. The main points of this dissertation are as follows:1. After a review of vector fields as well as their generation, the general methods to generate vector fields have been introduced. There are two ways to generate vector fields depending on whether or not involving amplifying media, i.e. the active way and passive way, corresponding to the generation inside the laser cavity or outside of the laser cavity. Different methods to generate vector beams with spatially structured polarization and phase distribution have been theoretically proposed and experimentally demonstrated, especially including the liquid crystal spatial light modulators which allows to flexibly design the arbitrary spatial (phase or amplitude or both) modulation patterns to generate the desired optical modes. We propose a convenient approach to generating arbitrary space-variant vector beam with structured polarization and phase distribution, which is accomplished in a4f system with a spatial light modulator (SLM) and a common path interferometric arrangement. Furthermore, by replacing one-dimensional holographic gratings with two-dimensional ones, we incorporate phase modulation in addition to polarization modulation into the vector beams so that they can generate the desired intensity distribution and polarization state in the focal volume.2. The Richards-Wolf vector theory is explored to calculate the focal properties. We present a fast calculation scheme of the electromagnetic field within the focal volume by using the fast Fourier transform (FFT) method on the basis of the angular spectrum theory. The amplitude, intensity, phase and polarization distributions of focused field of different types of vector beams have been numerically calculated. Our scheme simulates an iterative process between the forward and backward propagations that relate the incident field and the focal field, which is analogous to the Gerchberg-Saxton (GS) algorithm for retrieving the phase of a pair of light distributions. With the help of the FFT, we can tailor the polarization state and phase structure efficiently in the focal plane. This provides a novel way to control the vectorial feature of the focal volume with the help of polarization tailoring. Based on the method to generate the vector beams with the phase and the polarization modulated independently, the ability and flexibility to tailor the feature of the focal volume is verified by optical experiments.3. We extend the study to tight focusing of vector beams that have space-variant distribution of amplitude, phase and the polarization, each of that can be independently and simultaneously modulated. By tailoring the modulation depth of holographic gratings, we obtained the arbitrary vector beams with space-variant shapes of amplitude, phase and polarization, all of which are modulated independently and simultaneously. With our novel iterative algorithm that is based on a close inspection at the3D Fourier transform for synthesizing optical beams in the focal volume, a continuous intensity shaping within a volume becomes available.4. One of the common schemes for achieving focus shaping is to modify the polarization and phase of an incident beam so that it can yield a desired irradiance distribution in the focal volume. By focusing a hybridly polarized vector beam whose polarization state is periodically distributed along radius, a super-length optical needle of strong longitudinal polarized field with homogeneous intensity along the optical axis is generated. Moreover, the hybridly polarized beam is reformed into cylindrical symmetry in order to generate a super-length optical tube with a polarization vortex in the ring-shaped region. The novel vector fields are promising in finding new effects, phenomena, and applications.