Controlling light inside a multi-mode fiber by wavefront shaping

Binici, Halil İbrahim
Light is the primary tool used for collecting information from macroscopic and microscopic structures of matter. Micro-nano technology based materials like microcavities, waveguides, photonic crystals and fibers are used for confining light in space and the latter enable long distance information transfer. To increase the capacity of an information link, the core size of an optical fiber must be increased. Due to increased size of the fiber, the number of supported modes increases and becomes a multi-mode fiber. Given the increased number of modes, interference starts to play a major role and a random speckle pattern forms at the output of the fiber. In this thesis speckle pattern is controlled via controlling interference of the fiber modes by controlling relative phase among the guided modes. Wavefront shaping is developed for guiding light through highly scattering materials by spatially modulating the wavefront of an incident coherent beam. The most common way to shape the wavefront is to use a spatial light modulator (SLM). SLMs can be used to modulate the phase of a guided mode when employed at the input of an optical fiber as a spatial filter. As a result, the intensity pattern at the output plane can be controlled. In fact, the speckle pattern that is forming at the output of a multimode optical fiber can be concentrated to a single spot. In this thesis, we provide methods to control output of an optical fiber for developing advanced technologies for life sciences and communication technologies.
Citation Formats
H. İ. Binici, “Controlling light inside a multi-mode fiber by wavefront shaping,” M.S. - Master of Science, Middle East Technical University, 2018.