TY - BOOK

T1 - Investigations of disorder, extraordinary transmission, and polarization conversion in photonic crystals

AU - Glushko, Oleksandr

N1 - no embargo

PY - 2011

Y1 - 2011

N2 - The rising demand for new materials for controlling light signals at a micrometer scale is a general trend in development of optics and photonics during last two decades. Among such promising new materials are photonic crystals – composite structures where the dielectric constant depends periodically on the spatial coordinates. Photonic crystals can exhibit frequency regions of total reflection which are known as photonic band gaps. In addition, the optical properties of photonic crystals (e.g. spectral positions of the band gaps) can be easily varied by a proper choice of their geometry or even dynamically. This thesis presents investigations of several aspects of photonic crystal properties and applications. The influence of the surface roughness of 1D photonic crystals was investigated theoretically and experimentally. The calculated transmission spectra showed high robustness of the lowest band gap to surface roughness. With increasing frequency the effect of surface roughness on transmittance becomes more pronounced: the gaps become shallower and narrower; between the gaps the interference fringes smear out and the average transmittance decreases. The experimental transmission spectra are found to be in a very good agreement with the calculations. We believe that our results provide a fast and convenient way to estimate whether imperfections during the fabrication of a submicron 1D PhC will affect its transmission and reflection properties. The effect of disorder on the reflection peak of dilute 3D colloidal photonic crystals with bcc lattice was investigated by means of 3D FDTD calculations. In the case of disorder in the radii only a high amount (40% and more) has a visible effect on the reflection peak. Positional disorder decreases the maximal value of the peak only if the spheres are randomly shifted out of the (110) planes. Random removal of 20% of silica spheres from the structure results in a clearly visible decrease of the maximum of the reflection peak. We did not observe any broadening of the reflection peak as effect of disorder – only the maximal value is reduced. In the last Chapter of this thesis we explore the effects of extraordinary transmission and polarization conversion observed in 2D photonic crystal slabs covered with a metal layer. It was shown that these effects occur due to resonant coupling of the incident wave to specific doubly-degenerate photonic crystal eigenmodes with dipole symmetry. The excited modes are localized within a subwavelength distance below the metal and are polarized perpendicularly to the polarization of the incident wave. Beyond the fundamental interest the presented effects can be utilized for the improvement of the sensitivity of quantum well infrared photodetectors, to coupling of light to planar photonics elements or for the fabrication of transparent metal contacts.

AB - The rising demand for new materials for controlling light signals at a micrometer scale is a general trend in development of optics and photonics during last two decades. Among such promising new materials are photonic crystals – composite structures where the dielectric constant depends periodically on the spatial coordinates. Photonic crystals can exhibit frequency regions of total reflection which are known as photonic band gaps. In addition, the optical properties of photonic crystals (e.g. spectral positions of the band gaps) can be easily varied by a proper choice of their geometry or even dynamically. This thesis presents investigations of several aspects of photonic crystal properties and applications. The influence of the surface roughness of 1D photonic crystals was investigated theoretically and experimentally. The calculated transmission spectra showed high robustness of the lowest band gap to surface roughness. With increasing frequency the effect of surface roughness on transmittance becomes more pronounced: the gaps become shallower and narrower; between the gaps the interference fringes smear out and the average transmittance decreases. The experimental transmission spectra are found to be in a very good agreement with the calculations. We believe that our results provide a fast and convenient way to estimate whether imperfections during the fabrication of a submicron 1D PhC will affect its transmission and reflection properties. The effect of disorder on the reflection peak of dilute 3D colloidal photonic crystals with bcc lattice was investigated by means of 3D FDTD calculations. In the case of disorder in the radii only a high amount (40% and more) has a visible effect on the reflection peak. Positional disorder decreases the maximal value of the peak only if the spheres are randomly shifted out of the (110) planes. Random removal of 20% of silica spheres from the structure results in a clearly visible decrease of the maximum of the reflection peak. We did not observe any broadening of the reflection peak as effect of disorder – only the maximal value is reduced. In the last Chapter of this thesis we explore the effects of extraordinary transmission and polarization conversion observed in 2D photonic crystal slabs covered with a metal layer. It was shown that these effects occur due to resonant coupling of the incident wave to specific doubly-degenerate photonic crystal eigenmodes with dipole symmetry. The excited modes are localized within a subwavelength distance below the metal and are polarized perpendicularly to the polarization of the incident wave. Beyond the fundamental interest the presented effects can be utilized for the improvement of the sensitivity of quantum well infrared photodetectors, to coupling of light to planar photonics elements or for the fabrication of transparent metal contacts.

KW - Photonic crystal

KW - disorder

KW - surface roughness

KW - extraordinary optical transmission

KW - polarization conversion

KW - metal hole array

KW - coupling of light

KW - dipole mode

M3 - Doctoral Thesis

ER -