چكيده به لاتين
The introduction of Metasurfaces, and further increasing their operating frequency to the optical range, that has occurred thanks to the emergence and completion of new technologies for the construction of Nano devices, has created a great deal of hope for full control of light propagation.
High-level compatibility of Metasurfaces with cost-effective "Planar" Manufacturing Process, makes it easy to integrate them into more complex structures. This gives us distinctive capabilities for full control of the optical wave characteristics, including frequency, phase, angular momentum and polarization, which results in the realization of flat optics and photonics. Metasurfaces, by changing the amplitude and phase of the incident wave, creates a wavefront, depending on the required application. The main challenge in the functionality of metasurfaces is the selection of elements as building blocks of metasurface which can cover the required phase shift while maintaining the amplitude of the scattered wave suitably high.
In this thesis we have shown that, in a patch based metasurface, using the thicknesses of elements as a new controlling parameter will give us the ability to increase the range of the phase shift and simultaneously maintain the amplitude of the scattered wave dramatically high. This feature significantly improves performance both in terms of the efficiency and the high accuracy of the built-in wavefront compared to the optimal wavefront. To this end, the thesis describes the role of this new parameter in step-by-step development from the simplest structure to the final structure along with the introduction of analytic methods as well as the use of numerical simulations.
It has been shown that with the use of patch elements with just two thicknesses of 30 and 50 nm, the phase shift range increases up to 330 degrees, while the reflection amplitude in all modes is above 85 percent. In this case, one can select phase steps as small as 30 degrees. Finally, by designing a polarization beam splitter and a solar cell, we have verified the improved performance of these devices by applying the new controlling parameter.
Keywords: Metasurfaces, Plasmonics, Optical components, Optical patch antenna, Phase front engineering
