טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBiener Gabriel
SubjectSubwavelength Polarization Gratings: Design, Realization and
Applications
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Erez Hasman


Abstract

Subwavelength polarization gratings have opened up new methods for forming beams with sophisticated phase and polarization distributions. In this thesis we present 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. We realized the gratings for CO2 laser radiation at a wavelength of 10.6 mm on GaAs substrates utilizing advanced photolithographic and etching techniques.

We present novel optical phase elements based on the space-domain Pancharatnam-Berry phase. Unlike diffractive and refractive elements, the phase is not introduced through optical path differences, but results from the geometrical phase that accompanies space-variant polarization manipulation. We introduce and experimentally demonstrate continuous Pancharatnam-Berry phase optical elements (PBOEs) based on subwavelength grating such as polarization beam-splitters, optical switches and spiral phase element. We also discuss a theoretical analysis and an experimental demonstration of quantized Pancharatnam-Berry phase diffractive optics (Quantized-PBOE). The formation of a quantized geometrical phase is done by discrete orientation of the local subwavelength grating. We realized a quantized geometrical blazed phase of polarization diffraction grating, as well as polarization dependent focusing lens, and spiral phase elements for infrared radiation. The PBOEs will enable a variety of applications in modern optics. Additionally, we introduce a unique method for rapid polarization measurement based on subwavelength polarization grating and also depolarizing the light using subwavelength polarization grating depolarizer.