RSS FeedThe Circular Bragg Phenomenon
Category: EMch/ESc 514 Seminars
Posted by: sls60
on Sep 4, 2013
Dr. Muhammad Faryad
Department of Engineering Science and Mechanics, PSU
Wednesday, September 18, 2013
3:35pm - 4;25pm
114 EES Building
Abstract:
Circular Bragg phenomenon is the almost total reflection of incident light of one circular polarization state but very little of incident light of the other circular polarization state. The circular Bragg regime is the spectral regime in which this phenomenon occurs. Circularly polarized light has applications in synthesis of chiral compounds, efficient ionizations of atoms, fast and reversible coding of a magnetic tape, liquid-crystal displays, and three-dimensional displays. Cholesteric liquid crystals (CLCs) and chiral sculptured thin films (STFs) are the two most prominent dielectric thin-film materials exhibiting the circular Bragg phenomenon. The circular Bragg regime is blue-shifted for oblique incidence, and finally disappears at very high angle of incidence. The bandwidth and the center wavelength of the Bragg regime can be engineered by controlling the morphology of CLCs and chiral STFs. The circular Bragg phenomenon can even be made polarization insensitive and spatially dependent by appropriately modulating the chiral STFs during fabrication. Chief application of the circular Bragg phenomenon is the circular polarization filters. Single-section chiral STFs or CLCs can be used as bandstop filters. A narrowband bandpass or bandstop filter can be fabricated by manufacturing a defect in a chiral STF or a CLC. The optical filters can be used as laser mirrors and as filters in measuring instruments. The possibility of using the circular Bragg phenomenon in sensing an infiltrating fluid has also been demonstrated. A combination sensor that utilizes the circular Bragg phenomenon and multiple surface-plasmon-polariton waves can enhance further the capabilities of multi-analyte sensors. The utilization of Bragg phenomenon for sensing, and the combination sensors, are still in their infancy and there is great room for research, especially in their device level implementation. The promise of chiral STFs and CLCs as circular polarization light sources has been well established. Circular Bragg mirrors forming the cavity housing the active medium in a laser are used as circular polarization lasers. The emission spectrum of such lasers is dictated by the circular Bragg phenomenon. With the applications of the circularly polarized light on the rise, the need for the development of circular polarization lasers must grow.
Department of Engineering Science and Mechanics, PSU
Wednesday, September 18, 2013
3:35pm - 4;25pm
114 EES Building
Abstract:
Circular Bragg phenomenon is the almost total reflection of incident light of one circular polarization state but very little of incident light of the other circular polarization state. The circular Bragg regime is the spectral regime in which this phenomenon occurs. Circularly polarized light has applications in synthesis of chiral compounds, efficient ionizations of atoms, fast and reversible coding of a magnetic tape, liquid-crystal displays, and three-dimensional displays. Cholesteric liquid crystals (CLCs) and chiral sculptured thin films (STFs) are the two most prominent dielectric thin-film materials exhibiting the circular Bragg phenomenon. The circular Bragg regime is blue-shifted for oblique incidence, and finally disappears at very high angle of incidence. The bandwidth and the center wavelength of the Bragg regime can be engineered by controlling the morphology of CLCs and chiral STFs. The circular Bragg phenomenon can even be made polarization insensitive and spatially dependent by appropriately modulating the chiral STFs during fabrication. Chief application of the circular Bragg phenomenon is the circular polarization filters. Single-section chiral STFs or CLCs can be used as bandstop filters. A narrowband bandpass or bandstop filter can be fabricated by manufacturing a defect in a chiral STF or a CLC. The optical filters can be used as laser mirrors and as filters in measuring instruments. The possibility of using the circular Bragg phenomenon in sensing an infiltrating fluid has also been demonstrated. A combination sensor that utilizes the circular Bragg phenomenon and multiple surface-plasmon-polariton waves can enhance further the capabilities of multi-analyte sensors. The utilization of Bragg phenomenon for sensing, and the combination sensors, are still in their infancy and there is great room for research, especially in their device level implementation. The promise of chiral STFs and CLCs as circular polarization light sources has been well established. Circular Bragg mirrors forming the cavity housing the active medium in a laser are used as circular polarization lasers. The emission spectrum of such lasers is dictated by the circular Bragg phenomenon. With the applications of the circularly polarized light on the rise, the need for the development of circular polarization lasers must grow.