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Optimal Intensity Distribution in a Laser Beam for FSO Communications
Barcík, Peter ; Capsoni, Carlo (oponent) ; Číp, Ondřej (oponent) ; Wilfert, Otakar (vedoucí práce)
The doctoral thesis is focused on analysing the distribution of optical intensity within a radiated laser beam at the plane of the transmitting (TXA) and receiving (RXA) aperture which is affected by propagation through free space as well as through the atmosphere. The aim of the thesis is to determine the optimal intensity distribution of the laser beam at the transmitter plane which is less affected by turbulence during propagation and transmitter aperture itself. In order to analyse the propagation of an optical wave through atmospheric turbulence, the simulation based on the Split-Step method is utilized. The propagation of the Flattened Gaussian beam was analysed for weak and moderate turbulence regimes. The thesis discusses usage of multimode fiber with large diameter as a shaping element and includes a design of the refraction beam shaper which is able to convert the Gaussian beam to a flattened Gaussian beam. Finally, a model of a fully photonic transmitter and receiver was built. The system is used for generating and receiving an optical coherent wave.
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Advancements of Holographic endoscopy for in-vivo observations
Michálková, Ivana ; Tyc, Tomáš (oponent) ; Čižmár, Tomáš (vedoucí práce)
In recent years, a novel technique called holographic endoscopy has been developed and systematically improved. This unique technology utilizes a single hair-thin optical multimode fiber as a minimally invasive probe for deep tissue in vivo microscopy. A major milestone was reached last year when near-perfect focusing through a multimode fiber was achieved with the holographic endoscope. This breakthrough is significant for adapting scanning fluorescent microscopy techniques because it allows for more precise imaging with lower unwanted noise, thanks to the purity and fidelity of the focused excitation light. The achievement led to a new question: is it possible to generate more complex optical fields than diffraction-limited foci through the multimode fiber with comparable quality? This thesis aims to investigate this issue by producing Airy beams at the tip of the multimode fiber using the holographic endoscope setup. Two methods were used to produce Airy beams in this study: Fourier domain and direct field synthesis. The quality of the resulting beams was evaluated by comparing them to simulations. The propagation of the generated beams was also recorded and observed, and the potential of Fourier domain synthesis to control and modify the propagation characteristics of an Airy beam was explored. The analysis revealed that using the holographic endoscope setup, it is possible to create more complex optical fields, such as Airy beams, at the tip of a multimode fiber with an accuracy that matches the high-quality diffraction-limited foci produced in 2022. It is hoped that this work will serve as another stepping stone for the holographic endoscope's ability to work in microscopy regimes that utilize more complex light fields, such as structured illumination microscopy or stimulated emission depletion microscopy.
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Optimal Intensity Distribution in a Laser Beam for FSO Communications
Barcík, Peter ; Capsoni, Carlo (oponent) ; Číp, Ondřej (oponent) ; Wilfert, Otakar (vedoucí práce)
The doctoral thesis is focused on analysing the distribution of optical intensity within a radiated laser beam at the plane of the transmitting (TXA) and receiving (RXA) aperture which is affected by propagation through free space as well as through the atmosphere. The aim of the thesis is to determine the optimal intensity distribution of the laser beam at the transmitter plane which is less affected by turbulence during propagation and transmitter aperture itself. In order to analyse the propagation of an optical wave through atmospheric turbulence, the simulation based on the Split-Step method is utilized. The propagation of the Flattened Gaussian beam was analysed for weak and moderate turbulence regimes. The thesis discusses usage of multimode fiber with large diameter as a shaping element and includes a design of the refraction beam shaper which is able to convert the Gaussian beam to a flattened Gaussian beam. Finally, a model of a fully photonic transmitter and receiver was built. The system is used for generating and receiving an optical coherent wave.
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