Photonic crystals engineering for light manipulation: low symmetric and graded index media
Dr. Mirbek Turduev
Photonic crystals known as multi-dimensional periodic dielectric structures are versatile tools toward the realization of wavelength-scale photonic devices. Photonic crystals (PCs) are highly symmetric in terms of structural patterns, due to the lattice types and shape of the elements occupying the PC unit-cell. Since the first introduction of PCs the researchers have been paid much attention to photonic applications based on periodic media. However, periodic structures may be disadvantageous in some cases because of their high-symmetry. For example, high-symmetric structures are very sensitive to structural deformation, the tight operating bandwidth issue, and structural degradation during the fabrication process can be considered as another possible problem, since it causes deviation from the ideal cases. For this reason, introduction of quasi-periodic and disordered media to the literature have extended the research domain and provided additional novelties for manipulating and controlling light propagation. The idea of intentionally introducing reduced-symmetry paves the way to search for anomalous optical characteristics so that these types of PCs can be used in the design of novel optical devices. Breaking either translational or rotational symmetries of PCs provides enhanced and additional optical characteristics such as creation of a complete photonic band-gap, wavelength de-multiplexing, super-collimation, tilted self-collimation, and beam deflecting/routing properties. Utilizing these characteristics allows the design of several types of photonic devices such as polarization-independent waveguides, wavelength de-multiplexers, beam deflectors, and routers.
The talk will start with a brief introduction to photonic crystals along with a number of examples of the use of them for photonic devices and discuss the unique advantages in relation to conventional ones. Then the challenges related to photonic crystals will be mentioned with the novel approaches such as the concept of low symmetric photonic crystals and graded index photonic crystals proposed by the author to solve the aforementioned problems.