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Design of metasurfaces for advanced optical elements
Březina, Tomáš ; Kvapil, Michal (referee) ; Hrtoň, Martin (advisor)
Metasurfaces represent an intriguing class of materials with a wide range of promising applications, one of them being advanced planar optical elements for industrial production and imaging. The main goal of this thesis is to design such an optical element, namely a beam-shaper consisting of dielectric anostructures in HCTA (high constrast transmitarray) arrangement. The first part of this work introduces a simplified theoretical model of the optical response of building blocks that facilitates understanding of the basic functional mechanism behind the phase metasurfaces. To quantify the optical response of dielectric building blocks with enough precision, numerical FDTD simulations were employed. As a result, a database compatible with lithographic fabrication procedures was created. To find the phase distribution ensuring the desired beam-shaping function, two approaches were investigated and implemented: the semi-analytical method of geometric transformation and the iterative Gerchberg-Saxton algorithm. The final output of this work is then the distribution of building blocks within the metasurface that imprints into the impinging beam the previously calculated phase profile.
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Analysis of frequency and transient properties of non-integer order filters
Cieslar, Šimon ; Kubánek, David (referee) ; Koton, Jaroslav (advisor)
The bachelor thesis deals with analysis of frequency and transient properties of noninteger ( + )-order filters. These filters allow the use of a lower order, compared to the next higher integer-order ( + 1). For example, a system should be created, but a second order would not be sufficient, and in case of the integer-order, a third order system would be considered, but in the case of using a non-integer-order, a fractal-order between them can be used. In the following documentation, attention is paid to the defined group of fractal-order transfer functions, which approximate the identical course of the modulus characteristic according to Butterworth. The form of the function of the linear systems was not taken into account and characteristics such as phase response, group delay, step response and stability were analyzed and evaluated. All for the system ( + )-order, where 3, 4, variable Z1, 4 for (3 + )-order, variable Z1, 5 for (4 + )-order, and (0, 1). Non-integer systems offer a infinite number of orders, making them sometimes more advantageous in a step response or group delay. They can also provide an additional degree of freedom in designing a filter to fine-tune the slope of the amplitude characteristic in the bandwidth. The bachelor thesis deals with non-integer orders and their use in the case of required properties. For easier selection of the correct non-integer order with respect to the required properties, a design recommendation was written within the bachelor’s thesis.
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Design of metasurfaces for advanced optical elements
Březina, Tomáš ; Kvapil, Michal (referee) ; Hrtoň, Martin (advisor)
Metasurfaces represent an intriguing class of materials with a wide range of promising applications, one of them being advanced planar optical elements for industrial production and imaging. The main goal of this thesis is to design such an optical element, namely a beam-shaper consisting of dielectric anostructures in HCTA (high constrast transmitarray) arrangement. The first part of this work introduces a simplified theoretical model of the optical response of building blocks that facilitates understanding of the basic functional mechanism behind the phase metasurfaces. To quantify the optical response of dielectric building blocks with enough precision, numerical FDTD simulations were employed. As a result, a database compatible with lithographic fabrication procedures was created. To find the phase distribution ensuring the desired beam-shaping function, two approaches were investigated and implemented: the semi-analytical method of geometric transformation and the iterative Gerchberg-Saxton algorithm. The final output of this work is then the distribution of building blocks within the metasurface that imprints into the impinging beam the previously calculated phase profile.
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Analysis of frequency and transient properties of non-integer order filters
Cieslar, Šimon ; Kubánek, David (referee) ; Koton, Jaroslav (advisor)
The bachelor thesis deals with analysis of frequency and transient properties of noninteger ( + )-order filters. These filters allow the use of a lower order, compared to the next higher integer-order ( + 1). For example, a system should be created, but a second order would not be sufficient, and in case of the integer-order, a third order system would be considered, but in the case of using a non-integer-order, a fractal-order between them can be used. In the following documentation, attention is paid to the defined group of fractal-order transfer functions, which approximate the identical course of the modulus characteristic according to Butterworth. The form of the function of the linear systems was not taken into account and characteristics such as phase response, group delay, step response and stability were analyzed and evaluated. All for the system ( + )-order, where 3, 4, variable Z1, 4 for (3 + )-order, variable Z1, 5 for (4 + )-order, and (0, 1). Non-integer systems offer a infinite number of orders, making them sometimes more advantageous in a step response or group delay. They can also provide an additional degree of freedom in designing a filter to fine-tune the slope of the amplitude characteristic in the bandwidth. The bachelor thesis deals with non-integer orders and their use in the case of required properties. For easier selection of the correct non-integer order with respect to the required properties, a design recommendation was written within the bachelor’s thesis.
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