1D and 2D photonic crystals for thermo-photovoltaic converters and electro-optic modulators

Photonic crystals are widely used in photovoltaic applications such as filters, mirrors, and selective radiators due to their tunable energy bands and the advantage that photons travel faster than electrons without interaction. This thesis describes photonic crystal components in thermophotovoltaic systems that may improve the overall efficiency, with a particular focus on spectral efficiency and the band structures of 2D photonic crystals under the influence of rough surfaces and complex refractive indices.

Spectral efficiency is crucial for assessing the optical performance of filters. Although 1D photonic crystals have been extensively studied, there are still many open questions on the inevitable fabrication defects in practical production. In this work, the spectral efficiency of a wide range of structures is found to be reduced by the effect of complex refractive index. Studies on the interface roughness show a similar trend and further illustrate that the structures when modified by an evolution algorithm allow such defects to be compensated to some extent. In addition, emissivity studies of 1D photonic crystals have shown that a non-periodic structure can obtain the same radiation peaks as a periodic structure with more layers while having a smaller total thickness and fewer interference peaks.

To explore the photonic band characteristics of 2D photonic crystals, the structures that achieve the largest bandgaps are obtained by comparing different hole/cylinder shapes in a variety of lattices. Also, alternative materials and optimizations of the filling fraction are used to derive the optimal structure with the maximum photonic band utilization rate, providing a theoretical basis for relevant applications.

In addition, in the study of 2D photonic crystal slabs, it was found that annular holes make it easier to obtain higher effective refractive indices and relatively small bandgap shifts. We report the design of an inner radius optimized honeycomb lattice with annular holes, which exhibits a normalized bandgap width of 3*10^-6 and a utilization rate of less than 0.001\%. This helps to achieve fast band switching of the modulator.