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Cholesteric liquid crystal photonic ...

Zhou, Ying.

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Cholesteric liquid crystal photonic crystal lasers and photonic devices.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Cholesteric liquid crystal photonic crystal lasers and photonic devices./
Author:	Zhou, Ying.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2008,
Description:	154 p.
Notes:	Source: Dissertations Abstracts International, Volume: 70-06, Section: B.
Contained By:	Dissertations Abstracts International70-06B.
Subject:	Condensed matter physics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3335377
ISBN:	9780549888963

Cholesteric liquid crystal photonic crystal lasers and photonic devices.
Zhou, Ying.

Cholesteric liquid crystal photonic crystal lasers and photonic devices. - Ann Arbor : ProQuest Dissertations & Theses, 2008 - 154 p.

Source: Dissertations Abstracts International, Volume: 70-06, Section: B.

Thesis (Ph.D.)--University of Central Florida, 2008.

This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser emission is further demonstrated in a hybrid photonic band edge - Fabry-Perot (FP) type structure by sandwiching the CLC active layer within a circular polarized resonator consisting of two CLC reflectors. The resonator generates multiple FP modes while preserving the PBE mode from the active layer. More importantly this band edge mode can be greatly enhanced by the external resonator under some conditions. Theoretical analysis is conducted based on 4x4 transfer matrix and scattering matrix and the results are consistent with our experimental observations. To make the CLC laser more compact and miniaturized, we have developed a flexible polymer laser using dye-doped cholesteric polymeric films. By stacking the mirror reflecting layer, the active layer and the CLC reflecting layer, enhanced laser emission was observed in opposite-handed circular polarization state, because of the light recycling effect. On the other hand, we use the stacked cholesteric liquid crystal films, or the cholesteric liquid crystals and polymer composite films to demonstrate the single film broadband circular polarizers, which are helpful for converting a randomly polarized light into linear polarization. New fabrication methods are proposed and the circular polarizers cover ∼280 nm in the visible spectral range. Both theoretical simulation and experimental results are presented with a good match.

ISBN: 9780549888963Subjects--Topical Terms:

3173567
Condensed matter physics.
Subjects--Index Terms:

Cholesteric liquid crystals

Cholesteric liquid crystal photonic crystal lasers and photonic devices.
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020 $a 9780549888963
035 $a (MiAaPQ)AAI3335377
035 $a AAI3335377
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100 1 $a Zhou, Ying. $3 1680562
245 1 0 $a Cholesteric liquid crystal photonic crystal lasers and photonic devices.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2008
300 $a 154 p.
500 $a Source: Dissertations Abstracts International, Volume: 70-06, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Wu, Shin-Tson.
502 $a Thesis (Ph.D.)--University of Central Florida, 2008.
520 $a This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser emission is further demonstrated in a hybrid photonic band edge - Fabry-Perot (FP) type structure by sandwiching the CLC active layer within a circular polarized resonator consisting of two CLC reflectors. The resonator generates multiple FP modes while preserving the PBE mode from the active layer. More importantly this band edge mode can be greatly enhanced by the external resonator under some conditions. Theoretical analysis is conducted based on 4x4 transfer matrix and scattering matrix and the results are consistent with our experimental observations. To make the CLC laser more compact and miniaturized, we have developed a flexible polymer laser using dye-doped cholesteric polymeric films. By stacking the mirror reflecting layer, the active layer and the CLC reflecting layer, enhanced laser emission was observed in opposite-handed circular polarization state, because of the light recycling effect. On the other hand, we use the stacked cholesteric liquid crystal films, or the cholesteric liquid crystals and polymer composite films to demonstrate the single film broadband circular polarizers, which are helpful for converting a randomly polarized light into linear polarization. New fabrication methods are proposed and the circular polarizers cover ∼280 nm in the visible spectral range. Both theoretical simulation and experimental results are presented with a good match.
590 $a School code: 0705.
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Optics. $3 517925
653 $a Cholesteric liquid crystals
653 $a Liquid crystals
653 $a Photonic crystal lasers
653 $a Photonic devices
690 $a 0611
690 $a 0752
710 2 $a University of Central Florida. $3 1018467
773 0 $t Dissertations Abstracts International $g 70-06B.
790 $a 0705
791 $a Ph.D.
792 $a 2008
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3335377