dorsal/arxiv
View SchemaQuantification of optical pulsed-plane-wave-shaping by chiral sculptured thin films
| Authors | J. B. Geddes III, A. Lakhtakia |
|---|---|
| Categories | |
| ArXiv ID | physics/0606066 |
| URL | https://arxiv.org/abs/physics/0606066 |
| DOI | 10.1080/09500340600833368 |
| Journal | Journal of Modern Optics, Vol. 53, 2763-2783 (2006) |
Abstract
The durations and average speeds of ultrashort optical pulses transmitted through chiral sculptured thin films (STFs) were calculated using a finite-difference time-domain algorithm. Chiral STFs are a class of nanoengineered materials whose microstructure comprises parallel helicoidal nanowires grown normal to a substrate. The nanowires are $\sim$10-300 nm in diameter and $\sim1-10 \mu$m in length. Durations of transmitted pulses tend to increase with decreasing (free-space) wavelength of the carrier plane wave, while average speeds tend to increase with increasing wavelength. An increase in nonlinearity, as manifested by an intensity-dependent refractive index in the frequency domain, tends to increase durations of transmitted pulses and decrease average speeds. The circular Bragg phenomenon exhibited by a chiral STFs manifests itself in the frequency domain as high reflectivity for normally incident carrier plane waves whose circular polarization state is matched to the structural handedness of the film and whose wavelength falls in a range known as the Bragg regime; films of the opposite structural handedness reflect such plane waves little. This effect tends to distort the shapes of transmitted pulses with respect to the incident pulses, and such shaping can cause sharp changes in some measures of average speed with respect to carrier wavelength. A local maximum in the variation of one measure of the pulse duration with respect to wavelength is noted and attributed to the circular Bragg phenomenon. Several of these effects are explained via frequency-domain arguments. The presented results serve as a foundation for future theoretical and experimental studies of optical pulse propagation through causal, nonlinear, nonhomogeneous, and anisotropic materials.
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"abstract": "The durations and average speeds of ultrashort optical pulses transmitted\nthrough chiral sculptured thin films (STFs) were calculated using a\nfinite-difference time-domain algorithm. Chiral STFs are a class of\nnanoengineered materials whose microstructure comprises parallel helicoidal\nnanowires grown normal to a substrate. The nanowires are $\\sim$10-300 nm in\ndiameter and $\\sim1-10 \\mu$m in length. Durations of transmitted pulses tend to\nincrease with decreasing (free-space) wavelength of the carrier plane wave,\nwhile average speeds tend to increase with increasing wavelength. An increase\nin nonlinearity, as manifested by an intensity-dependent refractive index in\nthe frequency domain, tends to increase durations of transmitted pulses and\ndecrease average speeds. The circular Bragg phenomenon exhibited by a chiral\nSTFs manifests itself in the frequency domain as high reflectivity for normally\nincident carrier plane waves whose circular polarization state is matched to\nthe structural handedness of the film and whose wavelength falls in a range\nknown as the Bragg regime; films of the opposite structural handedness reflect\nsuch plane waves little. This effect tends to distort the shapes of transmitted\npulses with respect to the incident pulses, and such shaping can cause sharp\nchanges in some measures of average speed with respect to carrier wavelength. A\nlocal maximum in the variation of one measure of the pulse duration with\nrespect to wavelength is noted and attributed to the circular Bragg phenomenon.\nSeveral of these effects are explained via frequency-domain arguments. The\npresented results serve as a foundation for future theoretical and experimental\nstudies of optical pulse propagation through causal, nonlinear, nonhomogeneous,\nand anisotropic materials.",
"arxiv_id": "physics/0606066",
"authors": [
"J. B. Geddes III",
"A. Lakhtakia"
],
"categories": [
"physics.optics",
"physics.class-ph"
],
"doi": "10.1080/09500340600833368",
"journal_ref": "Journal of Modern Optics, Vol. 53, 2763-2783 (2006)",
"title": "Quantification of optical pulsed-plane-wave-shaping by chiral sculptured thin films",
"url": "https://arxiv.org/abs/physics/0606066"
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