Light scattering from multilayer optics I Tools of investigation

Amra, Claude

doi:10.1364/josaa.11.000197

Cited by 132 publications

(72 citation statements)

References 19 publications

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“…Other studies have looked at interfacial roughness in multilayers using perturbation analyses [Amra (1994), Elson (1995)]. However, these studies are limited to roughness scales much less than the wavelength of light and cannot be simply modified for specific 1 DPC configurations.…”

Section: - Total Fieldmentioning

confidence: 99%

“…Xiong, et al (1997) Never gives reflectance spectra or roughness. Amra (1994) Never gives roughness. Amra, et al (1997) Never gives roughness or micrograph.…”

Section: Micrographs Ohno Et Al (2001)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Again, application of homogenization theory to these structures confirms its predictive power for this type of imperfection as well. Additionally, the problem of acircular pores in 2D photonic crystals is investigated, 3 showing that almost a 50% change in reflectivity can occur for some structures.Furthermore, this study reveals trends that are consistent with the D simulations: parameter changes that increase the absolute reflectivity of the photonic crystal will also increase its tolerance to structural imperfections. Finally, experimental reflectance spectra from roughened D photonic crystals are compared to the results predicted computationally in this thesis.…”

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confidence: 99%

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Computational Study and Analysis of Structural Imperfections in 1D and 2D Photonic Crystals

Maskaly

2005

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Dielectric reflectors that are periodic in one or two dimensions, also known as 1D and 2D photonic crystals, have been widely studied for many potential applications due to the presence of wavelength-tunable photonic bandgaps. However, the unique optical behavior of photonic crystals is based on theoretical models of perfect analogues. Little is known about the practical effects of dielectric imperfections on their technologically useful optical properties. In order to address this issue, a finite-difference time-domain (FDTD) code is employed to study the effect of three specific dielectric imperfections in 1D and 2D photonic crystals. The first imperfection investigated is dielectric interfacial roughness in quarter-wave tuned ID photonic crystals at normal incidence. This study reveals that the reflectivity of some roughened photonic crystal configurations can change up to 50% at the center of the bandgap for RMS roughness values around 20% of the characteristic periodicity of the crystal. However, this reflectivity change can be mitigated by increasing the index contrast and/or the number of bilayers in the crystal. In order to explain these results, the homogenization approximation, which is usually applied to single rough surfaces, is applied to the quarter-wave stacks. The results of the homogenization approximation match the FDTD results extremely well, suggesting that the main role of the roughness features is to grade the refractive index profile of the interfaces in the photonic crystal rather than diffusely scatter the incoming light. This result also implies that the amount of incoherent reflection from the roughened quarterwave stacks is extremely small. This is confirmed through direct extraction of the amount of incoherent power from the FDTD calculations. Further FDTD studies are done on the entire normal incidence bandgap of roughened ID photonic crystals. These results reveal a narrowing and red-shifting of the normal incidence bandgap with increasing RMS roughness. Again, the homogenization approximation is able to predict these results. The problem of surface scratches on ID photonic crystals is also addressed. Although the reflectivity decreases are lower in this study, up to a 15% change in reflectivity is observed in certain scratched photonic crystal structures. However, this reflectivity change can be significantly decreased by adding a low index protective coating to the surface of the photonic crystal. Again, application of homogenization theory to these structures confirms its predictive power for this type of imperfection as well. Additionally, the problem of acircular pores in 2D photonic crystals is investigated, 3 showing that almost a 50% change in reflectivity can occur for some structures.Furthermore, this study reveals trends that are consistent with the D simulations: parameter changes that increase the absolute reflectivity of the photonic crystal will also increase its tolerance to structural imperfections. Finally, experimental reflectance spectra from roughened ...

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Section: - Total Fieldmentioning

confidence: 99%

“…Xiong, et al (1997) Never gives reflectance spectra or roughness. Amra (1994) Never gives roughness. Amra, et al (1997) Never gives roughness or micrograph.…”

Section: Micrographs Ohno Et Al (2001)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Computational Study and Analysis of Structural Imperfections in 1D and 2D Photonic Crystals

Maskaly

2005

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“…However, in those applications (e.g., atmosphere) the boundaries are nonscattering and hence do not significantly impact the scattering process. There are, indeed, several other applications such as subsurface sensing , optical mirrors (Amra, 1994;Elson, 1995), and seismology (Sato & Fehler, 1998) where the boundaries do scatter, thereby influencing the multiple scattering process. Consider the problem of two scattering media separated by a boundary.…”

Section: Introductionmentioning

confidence: 99%