Research On Manipulation And Application Of Novel Vector Beam

The characters of light involving the amplitude, phase and frequency have been deeply studied and widely used in various fields. In recent years, the polarization state of light and its manipulation have attracted much attention. Spatially arranging the polarization state of a light beam, purposefully and carefully, is expected to lead new phenomena and applications. One example is radially polarized (RP) vector beam, which has cylindrical symmetry polarization in beam’s cross section. RP beam has a strong longitudinal field when focused by a high NA lens, which makes it the optimal polarization choice in various applications, such as particle trapping, second harmonic generation, optical data storage, laser cutting and surface plasmon excitation. Currently the research on vector beams is fresh and there remain many scientific and technological problems. Thus, this dissertation is focus on the generation and manipulation of vector beams, and the applications in focus shaping and surface plasmon poariton (SPPs) manipulation.The main contributions of this dissertation are as follows:1. A method of generating novel vector beams is proposed. Based on the principle that a general cylindrical vector beam is the superposition of a positive vortex encoded right circularly polarized beam and a negative vortex encoded left circularly polarized beam, we use a4-f interferometric system to generate vector beams. In this system, a special designed vortex phase grating and a Damman phase grating are used, which makes it higher energy conversion efficiency than the hologram reconstructed either by an SLM or amplitude-modulated diffractive elements. By introducing a special phase plate in one arm of the interferometer, hybride polarization states of the vector beam can be obtained accordingly. When the topological charge of the vortex phase grating is changed, vector beams with charge can be generated as well. This method shows higher energy conversion efficiency and easier polarization conversion for the vector beams.2. Based on the Richads-Wolf vecor diffraction theory, we analysis the focusing property of vector beams with hybride polarization states and with high topotogical charge. Then two methods for focal field shaping are discussed. The first method is using the Eular transmission function to modulate amplitude distribution of RP beams. We find that by introducing a group of optimized constant factors for the Eular amplitude transmission function, the depth of the focal field (DOF) is enlarged to11λ, the focal spot is reduced to0.535X, and the ratio of longitudinal field to total field is increased to71%. In order to maintain the long DOF and reduce the size of focal spot, we study the second method of both polarization and amplitude modulation for incident beams. By this method, a subwavelength focal spot (0.4171) with long DOF is achieved, and the ratio of longitudinal field to total field is as high as84%.3. By analysis the property of surface palsmon excitated by focused vector beams with hybride polarization states, we propose an all-optical method to localize and cotntrol the SPPs electric field distribution. Calculation results show that, SPPs focal spot can be elonged and splited into focal spot array when change the area ratio of the TE to TM polarization in the incident beam’s cross section. When the vector beam with different topological charge m is focused on the metal surface, focal spot array also can be achieved, and the relationship between the topological charge m and the number of SPPs focal spots is described by2(m-1). Meawhile, the method of polarization manipulation of the SPPs is confirmed in experiment. At last, we realize all-optical dynamic control of SPPs focal spot by combining the vortex phase with RP vector beams, and.find moving distance of the SPPs spot is enlarged when increasing the topological charge of the vortex phase. Compared to manipulation by metal nano-structures, the all-optical manupulation of SPPs has the advanteges of easy implementation and flexible control, leads to potential applications in phase-SPR biosensor and integrated nanophotonic device.