טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBomzon Ze'ev
SubjectComputer Generated Subwavelength Optical Elements: Design,
Realization, and Applications
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Erez Hasman


Abstract

We have recently developed a novel method for designing and realizing nonuniformly polarized beams using computer generated space-variant subwavelength gratings. Our design is based on determining the local period and direction of the grating at each point, forming space-varying polarizers or waveplates that convert uniformly polarized light into any desired space-variant polarization. Our gratings are continuous thereby guaranteeing the continuity of the electromagnetic field. We realized the gratings for CO2 laser radiation at a wavelength of 10.6 mm on GaAs and ZnSe substrates utilizing advanced photolithographic and etching techniques. Our designs include a grating for converting circular polarization into radial polarization , as well as a grating for forming azimuthal polarization.


Furthermore, our work shows that space-variant polarization state manipulations are accompanied by a space-variant phase modification resulting from the Pancharatnam-Berry phase. This phase modification results solely from the polarization manipulation and is purely geometrical in nature. We found that this phase could be understood by projecting the resulting polarization onto the Poincare sphere. Our experiments and calculations showed that this phase was critical in understanding the propagation of space-variant polarized beams, and that it left a clear signature on their far-field images.


Finally we have also demonstrated a unique method for rapid polarization measurement based on a subwavelength space-variant polarization grating. The Stokes parameters of the incident beam are determined by spatial Fourier analysis, and the method enables real time polarization measurement.