Executive Summary : | Optical vortex beams are a class of beams having azimuthally varying phase around the beam axis and spatially varying polarization. The azimuthally varying phase is responsible for the beam to have an integral orbital angular momentum (OAM= +-l) associated with its helicity and the sign depends on whether the phase increases or decreases in an anti-clockwise direction. Depending on whether the beam has homogeneous or inhomogeneous spatial polarization, these beams are classified as scalar and vector vortices. The generation of such beams is possible in various methods which include spiral phase plates, Diffractive optical elements, computer-generated holograms, etc., Using proper mode mixing, few-mode optical fiber (FMF) can be used for generating vortex beams. In fact, a fiber optic system is always preferable over bulk optics for sensing and communication point of view. Here, in the proposed project, we aim at the generation of vector vortices in a few-mode optical fiber. However, stability is a challenging issue in vortex beam generation using optical fiber. Keeping in view the sensing device and communication applications of few-mode fiber, the proposed project will address few of the challenges in the area of OAM generation and propagation in fibers. It will aim for the stable and controlled generation of higher order vector vortices by inscribing long period grating (LPG) on FMF using in-house developed electric arc discharge fabrication technique. After achieving the stability of the system and with a proper understanding of mode mixing phenomena, the OAM beams of the first order can be generated in FMF by exciting zeroth order vector modes. To generate higher order vector vortices, first-order vector modes need to be excited and mixed in a few-mode fiber in proper orders. Hence the polarization features of the generated beams can be analyzed thoroughly using Stokes Polarimetry. A complete polarization mapping of generated vortex beams from FMF will be a great asset for understanding the mode multiplexing which can play a key role in next-generation optical fiber communication and high-temperature sensing applications. Eventually, the generated vortex beams will be tested for high-temperature sensing applications. |
Co-PI: | Dr. Sujith Thomas Birla Institute Of Technology & Science Pilani, Goa,Bits-Pilani K.K. Birla Goa Campus, Nh 17b Bypass Road, Zuarinagar, Sancoale,Goa,South Goa-403726 |