Spatial Modulation Of Optical Fields In Optical Microscopy And Applications

Spatial modulations of amplitude,phase and/or polarization state of optical fields with two-dimensional array devices,such as liquid crystal spatial light modulators(LC-SLM)or digital micro-mirror devices(DMD),may generate various specific optical fields in 2D/3D with desired spatial intensity distributions(e.g.,multi-focal spots arrays,non-diffracting beams,self-bending beams,etc.),which have found many applications in the fields of optical data storage,micro/nano structure fabrication,micro-particle manipulation,laser-induced plasma channel generation,super-resolution microcopy and so forth,putting this research direction in the frontier of current photonic researches.In this dissertation,by using liquid crystal spatial light modulator to modulate the spatial phase and/or amplitude of femtosecond laser or CW laser in optical microscopic systems,various multi-focal spots arrays and novel non-diffracting beams are produced,and exploited in a few applications.The main works are summarized as follows.1.An improved fast algorithm based on the classical Gerchberg-Saxton iterative algorithm has been proposed to calculate the computer-generated-hologram(CGH)of an arbitrary target optical field for an expected XZ cross section intensity distribution with high quality reconstruction merit.Three types of complex amplitude encoding algorithms for phase-type CGHs,i.e.,Davis algorithm,Arrizon1 algorithm and Arrizon2 algorithm,are implemented and compared in performance by numerical simulation.The theoretical reconstruction method of CGH is improved by incorporating the chirped Z-transform with the vectorial diffraction Richards-Wolf integration,which is significant for the improvement of experimental results.2.A multimodal experimental system for spatial modulation of optical field with femtosecond laser is designed and constructed.The phase modulation curve of a phase-only LC-SLM is optimized to be linear in the range of 0-2? by gamma correction with the method of binary phase grating maximal diffraction.Based on the principle of adaptive optics,the phase aberration of the optical system is corrected to obtain improved reconstruction optical fields by using the genetic algorithm,which is important for the applications of novel non-diffracting beams generation and parallel optical data storage.3.Several non-diffracting beams with new propagation characteristics have been theoretically proposed and experimentally implemented.By modifying the spatial frequency spectrum of the classical Airy beam,a new class of multi-main-lobe accelerating beams with parabolic accelerating trajectories have been generated.By superimposing kinoforms of multi-focal patterns into the spatial frequency spectrum of accelerating beams,different types of beam arrays,e.g.,Airy beam 3D arrays and two-main-lobe accelerating beam 3D arrays,are generated and measured by scanning a reflection mirror near the focal region along the optical axis.The presented technique can generate a variety of complex non-diffracting optical beams rapidly and obtain their three-dimensional intensity distributions accurately,which has potential applications in various fields.4.Permanently parallel optical data storage and polarization-sensitive microstructure fabrication in bacteriorhodopsin(BR)films are implemented.A femtosecond laser two-photon induced blue-shifted product in BR films was found and named F540 state,which has the permanent anisotropy induced by linearly polarized femtosecond laser beams.Based on this property,parallel optical data storage with polarization multiplexing or multilevel scheme has been demonstrated in BR films,with both the data throughput and storage intensity significantly increased.Polarization-sensitive microstructures,e.g.,one-dimensional gratings,two-dimensional optical lattices,Bessel zone plates,are also fabricated in BR films,which can be used as polarization controllable diffraction optical elements.5.An abnormal effect of femtosecond laser induced isotropic property in plastic polarizers was observed.Both theoretical analysis and experimental results reveal that this phenomenon is a two-photon absorption induced irreversible chemical reaction.With the merit of high polarization contrast,this two-photon induced isotropy(TPII)effect has been successfully exploited in parallel optical data storage with polarization multiplexing scheme,and various types of polarization-sensitive microstructures have been fabricated in plastic polarizers,which present very high structural contrast and high diffraction efficiency when used as polarization controllable diffraction optical elements.