Advanced control of light propagation in symmetry reduced photonic media

Recently in new generation photonic devices, the designs having elements with different sizes in the unit cell are widely used in photonics, since they have larger bandwidths, richer characteristics in the transmission spectrum, lower back reflection losses than those with high symmetry. In this thesis, asymmetric transmission properties, surface modes, and slow light characteristics are examined in the periodic structures with reduced rotational symmetry. In addition, cavity structure and surface waveguides are designed by breaking the high rotational symmetry of quasicrystals. The optical diodes are used in advanced photonics applications that prevent the optical signal to reach the other side of the structure. In the first part of the thesis, in addition to the broadband feature of the asymmetric transmission at the telecom wavelength, the photonic crystal structure has been designed to separate the light into different diffraction orders. The diffraction grating, which is designed in a heterogeneous manner using dielectric cylinders with different radii of silicon material, is very tolerant of the incident angle of the light wave. The design can transmit the light in the direction of +x by 73%, while the photonic crystal diffraction grating can reflect light at certain frequencies up to 99% in the opposite direction. In addition, the grating structure successfully divides the forward wave into the diffraction orders. The crystal structure designed with these features is a suitable candidate for use in the field of the spectrometer. In the third part of the thesis, control of the directional transmission of frequency selective and decelerated surface Bloch waves in low symmetric periodic structures is studied. For this purpose, additional elements have been added to the periodic structure and only the positions of the cylinders on the surface have been modified, as well as the frequency of the surface mode, the group velocity and the direction of propagation have been easily controlled. At the low values of the orientation angle, the group index of the surface increased to the value of 237. Since the waves that are attached to the surface are index guided, the position change of the rods causes the electric field distribution to vary. The changing effective refractive index of the structure allows the modulation of the surface frequency. Also, the negative slope of the surface modes appearing in the band diagram shows that backward transmission is possible on the structure surface. For the low orientation angles, the light travels in both directions, while the backward propagation becomes more dominant as the angle of orientation increases. Owing to the slow light property of the surface modes which can be easily modified on the surface, the design can be used in solar cells, sensor applications, and interferometers as a beam splitter waveguide. In the last part of the thesis, the high rotational symmetry of the octagonal quasicrystals is reduced to enhance the performance of the design in terms of cavity effect and surface modes. In quasicrystal, frequency, mode areas, and quality factors of the cavity modes are easily controlled. The surface-induced modification provides surface waves in this arrangement. Thanks to the size and position change of the cylinders located on the surface, frequency adjustment has become possible.