Speaker: Sruthy J L(EE16S021)
Date : July 22, 2019 (Monday)
Time : 4.00 PM
Venue : ESB 244, Seminar hall
Guide : Dr. Shanti Bhattacharya
Structured light refers to optical beams with modulated amplitude, phase or polarization. A Gaussian beam generated by a laser source can be structured to have helical wavefront by inducing a phase modulation of the form = , is the azimuthal phase angle,l is an integer. Such beams carry orbital angular momentum (OAM) with a quantized value of l and are called OAM beams.
This research is based on the design and fabrication of compact diffractive optical elements (DOEs) for the generation of OAM beams and to evaluate their performance on propagation through scattering medium. We design diffractive phase gratings with fork dislocation at the center that modulates a Gaussian beam to generate diffraction orders carrying OAM. As several applications require arrays of beams, we have designed Dammann gratings that can generate a large number of complex beams of equal intensity simultaneously. The diffractive optical elements (DOEs) are designed as binary elements for easier fabrication and therefore have only two phase values .OAM beams have diverse applications. For example, many such beams have properties that make them resistant to disturbances in the medium of propagation. They could then be used in applications such as imaging and communication, where the propagating beam travels through a scattering or turbid medium. Experiments were carried out to understand the effect of scattering on OAM beams. We design and fabricate a multifunctional DOE (MDOE) that facilitates a compact single channel interferometer (CSCI) which can replace the bulkier interferometer setup and acts as an elegant method to study the performance of OAM beams in a scattering medium.In addition, we demonstrate modal demultiplexing of generated OAM modes using diffractive elements