Measurement Of Optical Goos-H(?)nchen Shift And The Tight Focusing Properties Of Spatial-variant States Of Polarization Vector Beam

Bounded beam totally reflected from an interface between two different dielectric media may undergoes a lateral shift from the position predicted by geometrical optics. This phenomenon was referred to the Goos-H(a|¨)nchen (GH) effect. In recent years, people has attached great importance and done a great deal of research to the rule of limited light beam reflected by different optical microstructures. People also offer a lot of studies on experimental measurement of GH shift, such as: multiple reflections to increase displacement, position sensitive detectors (PSD), microwave method for measuring the GH displacement etc. This paper has simply and precise measured the GH shift of total reflection in prism by the light crystal light valve (LCLV) and the light beam profiler (LBP), compared and analyzed with the theoretical calculation. For the potential applications in new optical devices such as optical switches.As the vector beams has special polarization distribution, some innovative properties may happened when it has interaction with matters. Especially when it is tightly focused, we can gain some particular properties, such as can form a strong longitudinal field, can form a smaller spot size, optical cage and so on. This has great research significance and provide us new path to know and understand the properties of matters and the essence of the light beam.Base on research of GH shift and spatial-variant states of polarization vector beams, this paper has mainly completed two parts works: firstly, a novel approach to directly observe the small optical beam shift(GH shift)based on LCLV and the LBP; secondly, research of the generation and tight focusing properties of spatial-variant states of polarized vector beams. For the two parts job are mainly divided into three parts to discuss:1. Design and modify the experimental system of small optical shift GH. The novel experimental approach is a simple measurement based on LCLV and the LBP, which can be raised the accuracy of experiment result to nanometer scale. We studied the optical modulation characteristics of LCLV in experiment, and the results show that the polarization states of light changed when external voltage changes. The difference between the TM and TE polarized longitudinal GH shift at the condition of total internal reflection on a prism-air interface can be modulated the polarization state of the beam by the LCLV and detected by LBP registered the barry center of the beam. This method doesn't need complex external processing circuit, and the experimental result shows good agreement with theoretical calculation.2. The generation of spatial-variant states of polarized vector beams. Firstly, adjust the polarization converter, convert the linearly incident polarized beam into radially or azimuthally polarized beam and changed between them. Then the spatial-variant states of polarized vector beams can be obtained when radially or azimuthally polarized beam after the Liquid Crystal Variable Retarder (LCVR). As the LCVR are controlled by external voltage, we can obtain the continuous retardation angleδfrom 0 toπ, therefore the polarized distribution can be continuously changed by varying retardation angleδfrom 0 toπin real-time.3. Research of tightly focusing properties of spatial-variant states of polarization vector beam. The magnitude of the intensities strongly depends on the focusing angleαand the ratio of the pupil radius and the beam waistβ. However, the focusing intensity is not proportional toαorβ. In this article, we simulated and analyzed the impact to longitudinal electric field intensity whenαandβchanges, got the maximum longitudinal focus field and the corresponding optimum value ofαandβ. Then, we numerically simulated the transverse and longitudinal electric field intensity of spatial-variant states of polarized vector beams in the focal plane with the optimum value ofαandβ. The numerical results indicate a strong dependence of the field near the focus on the phase retardation angleδ. The evolution of the transverse focal pattern has little changes when the phase retardation angle changes from 0 toπ, while the longitudinal focal pattern is varied remarkably. Therefore,the longitudinal focal pattern can be continuous changed by varying retardation angleδfrom 0 toπin real-time.