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A '''liquid crystal laser''' is a [[laser]] that uses a [[liquid crystal]] as the [[resonator cavity]], allowing selection of emission wavelength and [[Polarization (waves)|polarization]] from the [[active laser medium]]. The lasing medium is usually a [[dye laser|dye]] doped into the liquid crystal. Liquid crystal lasers are comparable in size to [[Laser diode|diode lasers]], but provide the continuous wide spectrum tunability of [[dye laser]]s while maintaining a large [[Coherence (physics)|coherence area]]. The tuning range is typically several tens of [[nanometers]].<ref name=Woltman2007_357>[[#Woltman 2007|Woltman 2007]], p. 357</ref> [[Self-organization#Self-organization in physics|Self-organization]] at micrometer scales reduces manufacturing complexity compared to using layered [[photonic metamaterial]]s. Operation may be either in [[Continuous wave|continuous wave mode]] or in [[Laser#Pulsed_operation|pulsed mode]].<ref name=CWandPulsed />
A '''liquid-crystal laser''' is a [[laser]] that uses a [[liquid crystal]] as the [[resonator cavity]], allowing selection of emission wavelength and [[Polarization (waves)|polarization]] from the [[active laser medium]]. The lasing medium is usually a [[dye laser|dye]] doped into the liquid crystal. Liquid-crystal lasers are comparable in size to [[Laser diode|diode lasers]], but provide the continuous wide spectrum tunability of [[dye laser]]s while maintaining a large [[Coherence (physics)|coherence area]]. The tuning range is typically several tens of [[nanometers]].<ref name=Woltman2007_357>[[#Woltman 2007|Woltman 2007]], p. 357</ref> [[Self-organization#Self-organization in physics|Self-organization]] at micrometer scales reduces manufacturing complexity compared to using layered [[photonic metamaterial]]s. Operation may be either in [[Continuous wave|continuous wave mode]] or in [[Laser#Pulsed operation|pulsed mode]].<ref name=CWandPulsed />


==History==
==History==
Distributed feedback lasing using [[Bragg's law|Bragg reflection]] of a periodic structure instead of external [[mirror]]s was first proposed in 1971,<ref name="Kogelnik1971" /> predicted theoretically with [[cholesteric]] liquid crystals in 1978,<ref name="Kukhtarev1978" /> achieved experimentally in 1980,<ref name="Ilchishin1980" /> and explained in terms of a photonic [[band gap]] in 1998.<ref>[[#Woltman 2007|Woltman 2007]], p. 310</ref><ref name="Kopp1998" /><ref name="Dolgaleva2008" />
Distributed feedback lasing using [[Bragg's law|Bragg reflection]] of a periodic structure instead of external [[mirror]]s was first proposed in 1971,<ref name="Kogelnik1971" /> predicted theoretically with [[cholesteric]] liquid crystals in 1978,<ref name="Kukhtarev1978" /> achieved experimentally in 1980,<ref name="Ilchishin1980" /> and explained in terms of a photonic [[band gap]] in 1998.<ref>[[#Woltman 2007|Woltman 2007]], p. 310</ref><ref name="Kopp1998" /><ref name="Dolgaleva2008" />
A [[United States patent law|United States Patent]] issued in 1973 described a liquid crystal laser that uses "a liquid lasing medium having internal distributed feedback by virtue of the molecular structure of a cholesteric liquid crystal material."<ref name=Patent />
A [[United States patent law|United States Patent]] issued in 1973 described a liquid-crystal laser that uses "a liquid lasing medium having internal distributed feedback by virtue of the molecular structure of a cholesteric liquid-crystal material."<ref name=Patent />


==Mechanism==
==Mechanism==
Starting with a liquid crystal in the nematic phase, the desired helical pitch (the distance along the helical axis for one complete rotation of the nematic plane subunits) can be achieved by doping the liquid crystal with a chiral molecule.<ref name="Dolgaleva2008" /> For light circularly polarized with the same handedness, this regular modulation of the refractive index yields selective reflection of the wavelength given by the helical pitch, allowing the liquid crystal laser to serve as its own resonator cavity. [[Photonic crystal]]s are amenable to [[Electronic band structure|band theory]] methods, with the periodic dielectric structure playing the role of the periodic electric potential and a photonic band gap (reflection notch) corresponding to forbidden frequencies. The lower photon group velocity and higher [[density of states]] near the photonic bandgap suppresses [[spontaneous emission]] and enhances [[stimulated emission]], providing favorable conditions for lasing.<ref name="Kopp1998" /><ref name="Kuroda2009" /> If the electronic band edge falls in the photonic bandgap, electron-hole recombination is strictly suppressed.<ref name="Yablonovich1987" /> This allows for devices with high lasing efficiency, low lasing threshold, and stable frequency, where the liquid crystal laser acts its own waveguide. "Colossal" [[nonlinear optics|nonlinear]] change in refractive index is achievable in doped nematic-phase liquid crystals, that is the refractive index can change at a rate of about 1000 per 1 W/cm<sup>2</sup> of illumination intensity.<ref name="Lucchetti2004" /><ref name="Khoo1995" /><ref name="Khoo2007" /> Most systems use a semiconductor [[Laser pumping|pumping laser]] to achieve [[population inversion]], though flash lamp and electrical pumping systems are possible.<ref name="Morris2008" />
Starting with a liquid crystal in the nematic phase, the desired helical pitch (the distance along the helical axis for one complete rotation of the nematic plane subunits) can be achieved by doping the liquid crystal with a chiral molecule.<ref name="Dolgaleva2008" /> For light circularly polarized with the same handedness, this regular modulation of the refractive index yields selective reflection of the wavelength given by the helical pitch, allowing the liquid-crystal laser to serve as its own resonator cavity. [[Photonic crystal]]s are amenable to [[Electronic band structure|band theory]] methods, with the periodic dielectric structure playing the role of the periodic electric potential and a photonic band gap (reflection notch) corresponding to forbidden frequencies. The lower photon group velocity and higher [[density of states]] near the photonic bandgap suppresses [[spontaneous emission]] and enhances [[stimulated emission]], providing favorable conditions for lasing.<ref name="Kopp1998" /><ref name="Kuroda2009" /> If the electronic band edge falls in the photonic bandgap, electron-hole recombination is strictly suppressed.<ref name="Yablonovich1987" /> This allows for devices with high lasing efficiency, low [[lasing threshold]], and stable frequency, where the liquid-crystal laser acts its own waveguide. "Colossal" [[nonlinear optics|nonlinear]] change in refractive index is achievable in doped nematic-phase liquid crystals, that is the refractive index can change with illumination intensity at a rate of about 10<sup>3</sup>cm<sup>2</sup>/W of illumination intensity.<ref name="Lucchetti2004" /><ref name="Khoo1995" /><ref name="Khoo2007" /> Most systems use a semiconductor [[Laser pumping|pumping laser]] to achieve [[population inversion]], though flash lamp and electrical pumping systems are possible.<ref name="Morris2008" />


Tuning of the output wavelength is achieved by smoothly varying the helical pitch: as the winding changes, so does the length scale of the crystal. This in turn shifts the band edge and changes the optical path length in the lasing cavity. Applying a static electric field perpendicular to the dipole moment of the local nematic phase rotates the rod-like subunits in the hexagonal plane and reorders the chiral phase, winding or unwinding the helical pitch.<ref name="Maune2004" /> Similarly, optical tuning of the output wavelength is available using laser light far from the pick-up frequency of the gain medium, with degree of rotation governed by intensity and the angle between the polarization of the incident light and the dipole moment.<ref name="Furumi2004" /><ref name="Fuh2004" /><ref name="Khoo1993" /> Reorientation is stable and reversible. The chiral pitch of a cholesteric phase tends to unwind with increasing temperature, with a [[Order and disorder (physics)|disorder-order transition]] to the higher symmetry nematic phase at the high end.<ref name="Ilchishin1980" /><ref name="Morris2005" /><ref name="Morris2009" /><ref name="Ozaki2002" /> By applying a temperature gradient perpendicular to the direction of emission varying the location of stimulation, frequency may be selected across a continuous spectrum.<ref name="Huang2006" /> Similarly, a quasi-continuous doping gradient yields multiple laser lines from different locations on the same sample.<ref name="Morris2008" /> Spatial tuning may also be accomplished using a wedge cell. The boundary conditions of the narrower cell squeeze the helical pitch by requiring a particular orientation at the edge, with discrete jumps where the outer cells rotate to the next stable orientation; frequency variation between jumps is continuous.<ref name="Jeong2008" />
Tuning of the output wavelength is achieved by smoothly varying the helical pitch: as the winding changes, so does the length scale of the crystal. This in turn shifts the band edge and changes the optical path length in the lasing cavity. Applying a static electric field perpendicular to the dipole moment of the local nematic phase rotates the rod-like subunits in the hexagonal plane and reorders the chiral phase, winding or unwinding the helical pitch.<ref name="Maune2004" /> Similarly, optical tuning of the output wavelength is available using laser light far from the pick-up frequency of the gain medium, with degree of rotation governed by intensity and the angle between the polarization of the incident light and the dipole moment.<ref name="Furumi2004" /><ref name="Fuh2004" /><ref name="Khoo1993" /> Reorientation is stable and reversible. The chiral pitch of a cholesteric phase tends to unwind with increasing temperature, with a [[Order and disorder (physics)|disorder-order transition]] to the higher symmetry nematic phase at the high end.<ref name="Ilchishin1980" /><ref name="Morris2005" /><ref name="Morris2009" /><ref name="Ozaki2002" /> By applying a temperature gradient perpendicular to the direction of emission varying the location of stimulation, frequency may be selected across a continuous spectrum.<ref name="Huang2006" /> Similarly, a quasi-continuous doping gradient yields multiple laser lines from different locations on the same sample.<ref name="Morris2008" /> Spatial tuning may also be accomplished using a wedge cell. The boundary conditions of the narrower cell squeeze the helical pitch by requiring a particular orientation at the edge, with discrete jumps where the outer cells rotate to the next stable orientation; frequency variation between jumps is continuous.<ref name="Jeong2008" />
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==Applications==
==Applications==
* Biomedical sensing: small size, low cost, and low power consumption offer a variety of advantages in biomedical sensing applications. Potentially, liquid crystal lasers could form the basis for "lab on a chip" devices that provide immediate readings without sending a sample away to a separate lab.<ref name="Physorg2005" />
* Biomedical sensing: small size, low cost, and low power consumption offer a variety of advantages in biomedical sensing applications. Potentially, liquid-crystal lasers could form the basis for "lab on a chip" devices that provide immediate readings without sending a sample away to a separate lab.<ref name="Physorg2005" />
* Medical: low emission power limits such medical procedures as cutting during [[surgeries]], but liquid crystal lasers show potential to be used in [[microscopy]] techniques and ''[[in vivo]]'' techniques such as [[photodynamic therapy]].<ref name=Woltman2007_357 />
* Medical: low emission power limits such medical procedures as cutting during [[surgeries]], but liquid-crystal lasers show potential to be used in [[microscopy]] techniques and ''[[in vivo]]'' techniques such as [[photodynamic therapy]].<ref name=Woltman2007_357 />
* Display screens: liquid crystal laser based displays offer most of the advantages of standard liquid crystal displays, but the low spectral spread gives more precise control over color. Individual elements are small enough to act as single pixels while retaining high brightness and color definition. A system in which each pixel is a single spatially tuned device could avoid the sometimes long relaxation times of dynamic tuning, and could emit any color using spatial addressing and the same monochromatic pumping source.<ref name="Physorg2005" /><ref name="Physorg2009" /><ref name="LFW2009" />
* Display screens: liquid-crystal-laser-based displays offer most of the advantages of standard liquid-crystal displays, but the low spectral spread gives more precise control over color. Individual elements are small enough to act as single pixels while retaining high brightness and color definition. A system in which each pixel is a single spatially tuned device could avoid the sometimes long relaxation times of dynamic tuning, and could emit any color using spatial addressing and the same monochromatic pumping source.<ref name="Physorg2005" /><ref name="Physorg2009" /><ref name="LFW2009" />
* Environmental sensing: using a material with a helical pitch highly sensitive to temperature, electric field, magnetic field, or mechanical strain, color shift of the output laser provides a simple, direct measurement of environmental conditions.<ref name="Palffy-Muhoray2006" />
* Environmental sensing: using a material with a helical pitch highly sensitive to temperature, electric field, magnetic field, or mechanical strain, color shift of the output laser provides a simple, direct measurement of environmental conditions.<ref name="Palffy-Muhoray2006" />


==References==
== References ==

{{reflist|2|refs=
{{reflist|30em|refs=
* <ref name="Dolgaleva2008">{{cite journal|title = Enhanced laser performance of cholesteric liquid crystals doped with oligofluorene dye|journal = Journal of the Optical Society of America|year = 2008|first = Ksenia|last = Dolgaleva|coauthors = Simon K.H. Wei, Svetlana G. Lukishova, Shaw H. Chen, Katie Schwertz, and Robert W. Boyd|volume = 25|issue = 9|pages = 1496–1504|doi=10.1364/JOSAB.25.001496|bibcode = 2008JOSAB..25.1496D }}</ref>
* <ref name="Fuh2004">{{cite journal|title = Lasing in chiral photonic liquid crystals and associated frequency tuning|journal = Optics Express|year = 2004|first = Fuh|last = Andy|coauthors = Tsung-Hsien Lin, J.-H. Liu, and F.-C. Wu|volume = 12|issue = 9|pages = 1857–1863|doi=10.1364/OPEX.12.001857|pmid = 19475016|bibcode = 2004OExpr..12.1857F }}</ref>
* <ref name="Dolgaleva2008">{{cite journal|title = Enhanced laser performance of cholesteric liquid crystals doped with oligofluorene dye|journal = Journal of the Optical Society of America|year = 2008|first = Ksenia|last = Dolgaleva|author2=Simon K.H. Wei |author3=Svetlana G. Lukishova |author4=Shaw H. Chen |author5=Katie Schwertz |author6=Robert W. Boyd |volume = 25|issue = 9|pages = 1496–1504|doi=10.1364/JOSAB.25.001496|bibcode = 2008JOSAB..25.1496D }}</ref>
* <ref name="Furumi2004">{{cite journal|title = Phototunable photonic bandgap in chiral liquid crystal device|journal = Applied Physics Letters|year = 2004|first = Seiichi|last = Furumi|coauthors = Shiyoshi Yokoyama, Akira Otomo, and Shinro Mashiko|volume = 84|pages = 2491|doi=10.1063/1.1699445|issue = 14|bibcode = 2004ApPhL..84.2491F }}</ref>
* <ref name="Fuh2004">{{cite journal|title = Lasing in chiral photonic liquid crystals and associated frequency tuning|journal = Optics Express|year = 2004|first = Fuh|last = Andy |author2=Tsung-Hsien Lin |author3=J.-H. Liu |author4=F.-C. Wu|volume = 12|issue = 9|pages = 1857–1863|doi=10.1364/OPEX.12.001857|pmid = 19475016|bibcode = 2004OExpr..12.1857F |doi-access = free}}</ref>
* <ref name="Huang2006">{{cite journal|title = Spatially tunable laser emission in dye-doped photonic liquid crystals |journal = Applied Physics Letters|year = 2006|first = Yuhua|last = Huang|coauthors = Ying Zhou, and Shin-Tson Wu|volume = 88|pages = 011107| doi=10.1063/1.2161167|bibcode = 2006ApPhL..88a1107H }}</ref>
* <ref name="Furumi2004">{{cite journal|title = Phototunable photonic bandgap in chiral liquid crystal device|journal = Applied Physics Letters|year = 2004|first = Seiichi|last = Furumi|author2=Shiyoshi Yokoyama |author3=Akira Otomo |author4=Shinro Mashiko |volume = 84|pages = 2491|doi=10.1063/1.1699445|issue = 14|bibcode = 2004ApPhL..84.2491F }}</ref>
* <ref name="Ilchishin1980">{{cite journal|title = Generation of a tunable radiation by impurity cholesteric liquid crystals|journal = Journal of Experimental and Theoretical Physics Letters|year = 1980|first = I.P.|last = Ilchishin|coauthors = E.A. Tikhonov, V.G. Tishchenko, and M.T. Shpak|volume = 32|pages = 24–27|bibcode = 1980JETPL..32...24I }}</ref>
* <ref name="Huang2006">{{cite journal|title = Spatially tunable laser emission in dye-doped photonic liquid crystals |journal = Applied Physics Letters|year = 2006|first = Yuhua|last = Huang |author2=Ying Zhou |author3=Shin-Tson Wu|volume = 88|issue = 1|pages = 011107| doi=10.1063/1.2161167|bibcode = 2006ApPhL..88a1107H | s2cid=119500768 |url = https://stars.library.ucf.edu/facultybib2000/6241}}</ref>
* <ref name="Jeong2008">{{cite journal|title = Spatial tuning of laser emission in a dye-doped cholesteric liquid crystal wedge cell|journal = Applied Physics Letters|year = 2008|first = Mi-Yun|last = Jeong|coauthors = Hyunhee Choi, and J. W. Wu|volume = 92|pages = 051108|doi=10.1063/1.2841820|issue = 5|bibcode = 2008ApPhL..92e1108J }}</ref>
* <ref name="Ilchishin1980">{{cite journal|title = Generation of a tunable radiation by impurity cholesteric liquid crystals|journal = Journal of Experimental and Theoretical Physics Letters|year = 1980|first = I.P.|last = Ilchishin |author2=E.A. Tikhonov |author3=V.G. Tishchenko |author4=M.T. Shpak|volume = 32|pages = 24–27|bibcode = 1980JETPL..32...24I }}</ref>
* <ref name="Kogelnik1971">{{cite journal|title = Stimulated emission in a periodic structure|journal = Applied Physics Letters|year = 1971|first = H.|last = Kogelnik|coauthors = C.V. Shank|volume = 18|pages = 152| doi=10.1063/1.1653605|issue = 4|bibcode = 1971ApPhL..18..152K }}</ref>
* <ref name="Jeong2008">{{cite journal|title = Spatial tuning of laser emission in a dye-doped cholesteric liquid crystal wedge cell|journal = Applied Physics Letters|year = 2008|first = Mi-Yun|last = Jeong|author2=Hyunhee Choi |author3=J. W. Wu |volume = 92|pages = 051108|doi=10.1063/1.2841820|issue = 5|bibcode = 2008ApPhL..92e1108J }}</ref>
* <ref name="Kogelnik1971">{{cite journal|title = Stimulated emission in a periodic structure|journal = Applied Physics Letters|year = 1971|first = H.|last = Kogelnik|author2=C.V. Shank |volume = 18|pages = 152| doi=10.1063/1.1653605|issue = 4|bibcode = 1971ApPhL..18..152K }}</ref>
* <ref name="Khoo1993">{{cite book|last1 = Khoo|first1 = Iam-Choo|last2 = Wu|first2 = Shin-Tson|title = Optics and nonlinear optics of liquid crystals|publisher = World Scientific|year = 1993|accessdate = 2011-04-09|isbn = 9789810209346}}</ref>
* <ref name="Khoo1993">{{cite book|last1 = Khoo|first1 = Iam-Choo|last2 = Wu|first2 = Shin-Tson|title = Optics and nonlinear optics of liquid crystals|publisher = World Scientific|year = 1993|isbn = 978-981-02-0934-6}}</ref>
* <ref name="Khoo1995">{{cite journal|title = Holographic grating formation in dye- and fullerene C60-doped nematic liquid-crystal film|journal = Optics Letters|year = 1995|first = I.C.|last = Khoo|volume = 20|issue = 20|pages = 2137–2139|doi=10.1364/OL.20.002137|pmid = 19862276|bibcode = 1995OptL...20.2137K }}</ref>
* <ref name="Khoo1995">{{cite journal|title = Holographic grating formation in dye- and fullerene C60-doped nematic liquid-crystal film|journal = Optics Letters|year = 1995|first = I.C.|last = Khoo|volume = 20|issue = 20|pages = 2137–2139|doi=10.1364/OL.20.002137|pmid = 19862276|bibcode = 1995OptL...20.2137K }}</ref>
* <ref name="Khoo2007">{{cite book|last1 = Khoo|first1 = Iam-Choo|title = Liquid Crystals|publisher = Wiley-Interscience|year = 2007|accessdate = 2011-04-24|isbn = 9780471751533}}</ref>
* <ref name="Khoo2007">{{cite book|last1 = Khoo|first1 = Iam-Choo|title = Liquid Crystals|publisher = Wiley-Interscience|year = 2007|isbn = 978-0-471-75153-3}}</ref>
* <ref name="Kopp1998">{{cite journal|title = Low-threshold lasing at the edge of a photonic stop band in cholesteric liquid crystals|journal = Optics Express|year = 1998|first = V.I.|last = Kopp|coauthors = B. Fan, H. K. M. Vithana, and A. Z. Genack|volume = 23|issue = 21|pages = 1707–1709| doi=10.1364/OL.23.001707|bibcode = 1998OptL...23.1707K|pmid=18091891}}</ref>
* <ref name="Kopp1998">{{cite journal|title = Low-threshold lasing at the edge of a photonic stop band in cholesteric liquid crystals|journal = Optics Express|year = 1998|first = V.I.|last = Kopp|author2=B. Fan |author3=H. K. M. Vithana |author4=A. Z. Genack |volume = 23|issue = 21|pages = 1707–1709| doi=10.1364/OL.23.001707|bibcode = 1998OptL...23.1707K|pmid=18091891| s2cid=17966093 }}</ref>
* <ref name="Kukhtarev1978">{{cite journal|title = Cholesteric liquid crystal laser with distributed feedback|journal = Soviet Journal of Quantum Electronics|year = 1978|first = NV|last = Kukhtarev|volume = 8|pages = 774|doi=10.1070/QE1978v008n06ABEH010397|issue = 6|bibcode = 1978QuEle...8..774K }}</ref>
* <ref name="Kukhtarev1978">{{cite journal|title = Cholesteric liquid crystal laser with distributed feedback|journal = Soviet Journal of Quantum Electronics|year = 1978|first = NV|last = Kukhtarev|volume = 8|pages = 774–776|doi=10.1070/QE1978v008n06ABEH010397|issue = 6|bibcode = 1978QuEle...8..774K }}</ref>
* <ref name="Kuroda2009">{{cite journal|title = Doubly enhanced spontaneous emission due to increased photon density of states at photonic band edge frequencies|journal = Optics Express|year = 2009|first = Keiji|last = Kuroda|coauthors = Tsutomu Sawada, Takashi Kuroda, Kenji Watanabe, and Kazuaki Sakoda|volume = 17|issue = 15|pages = 13168–13177| doi=10.1364/OE.17.013168|pmid = 19654722|bibcode = 2009OExpr..1713168K }}</ref>
* <ref name="Kuroda2009">{{cite journal|title = Doubly enhanced spontaneous emission due to increased photon density of states at photonic band edge frequencies|journal = Optics Express|year = 2009|first = Keiji|last = Kuroda|author2=Tsutomu Sawada |author3=Takashi Kuroda |author4=Kenji Watanabe |author5=Kazuaki Sakoda |volume = 17|issue = 15|pages = 13168–13177| doi=10.1364/OE.17.013168|pmid = 19654722|bibcode = 2009OExpr..1713168K |doi-access = free}}</ref>
* <ref name="LFW2009">{{cite news|title = Laser Displays: liquid-crystal laser promises low-fabrication-cost display|date = 2009-01|url = http://www.optoiq.com/index/display/article-display/349350/articles/laser-focus-world/volume-45/issue-1/world-news/laser-displays-liquid-crystal-laser-promises-low-fabrication-cost-display.html|work = Laser Focus World|accessdate = 2011-04-09}}</ref>
* <ref name="LFW2009">{{cite news|title = Laser Displays: liquid-crystal laser promises low-fabrication-cost display|date = January 2009|url = http://www.optoiq.com/index/display/article-display/349350/articles/laser-focus-world/volume-45/issue-1/world-news/laser-displays-liquid-crystal-laser-promises-low-fabrication-cost-display.html|work = Laser Focus World|accessdate = 2011-04-09}}</ref>
<ref name="Lucchetti2004">{{cite journal|title = Colossal optical nonlinearity in dye doped liquid crystals|journal = Optics Communications|year = 2004|first = L.|last = Lucchetti|coauthors = M. Di Fabrizio, O. Francescangeli, and F. Simoni |volume = 233|pages = 417–424|doi=10.1016/j.optcom.2004.01.057|issue = 4–6|bibcode = 2004OptCo.233..417L }}</ref>
<ref name="Lucchetti2004">{{cite journal|title = Colossal optical nonlinearity in dye doped liquid crystals|journal = Optics Communications|year = 2004|first = L.|last = Lucchetti|author2=M. Di Fabrizio |author3=O. Francescangeli |author4=F. Simoni |volume = 233|pages = 417–424|doi=10.1016/j.optcom.2004.01.057|issue = 4–6|bibcode = 2004OptCo.233..417L }}</ref>
* <ref name="Maune2004">{{cite journal|title = Liquid-crystal electric tuning of a photonic crystal laser|journal = Applied Physics Letters|year = 2004|first = Brett|last = Maune|coauthors = Marko Lončar, Jeremy Witzens, Michael Hochberg, Thomas Baehr-Jones, Demetri Psaltis, Axel Scherer, and Yueming Qiu|volume = 85|pages = 360| doi=10.1063/1.1772869|issue = 3|bibcode = 2004ApPhL..85..360M }}</ref>
* <ref name="Maune2004">{{cite journal|title = Liquid-crystal electric tuning of a photonic crystal laser|journal = Applied Physics Letters|year = 2004|first = Brett|last = Maune|author2=Marko Lončar |author3=Jeremy Witzens |author4=Michael Hochberg |author5=Thomas Baehr-Jones |author6=Demetri Psaltis |author7=Axel Scherer |author8=Yueming Qiu |volume = 85|pages = 360| doi=10.1063/1.1772869|issue = 3|bibcode = 2004ApPhL..85..360M |url=https://infoscience.epfl.ch/record/155399/files/APL_85_360_Jul2004.pdf}}</ref>
* <ref name="Morris2005">{{cite journal|title = Enhanced emission from liquid-crystal lasers|journal = Journal of Applied Physics|year = 2005|first = S.M.|last = Morris|coauthors = A. D. Ford, M. N. Pivnenko, and H. J. Coles|volume = 97|pages = 023103| doi=10.1063/1.1829144|issue = 2|bibcode = 2005JAP....97b3103M }}</ref>
* <ref name="Morris2005">{{cite journal|title = Enhanced emission from liquid-crystal lasers|journal = Journal of Applied Physics|year = 2005|first = S.M.|last = Morris|author2=A. D. Ford |author3=M. N. Pivnenko |author4=H. J. Coles |volume = 97|pages = 023103–023103–9| doi=10.1063/1.1829144|issue = 2|bibcode = 2005JAP....97b3103M }}</ref>
* <ref name="Morris2008">{{cite journal|title = Polychromatic liquid crystal laser arrays towards display applications|journal = Optics Express|year = 2008|first = Stephen M.|last = Morris|coauthors = Philip JW Hands, Sonja Findeisen-Tandel, Robert H. Cole, Timothy D. Wilkinson, and Harry J. Coles|volume = 16|issue = 23|pages = 18827–37| doi=10.1364/OE.16.018827|pmid = 19581971|url=http://www-g.eng.cam.ac.uk/CMMPE/OE_16_23_2008.pdf|bibcode = 2008OExpr..1618827M }}</ref>
* <ref name="Morris2008">{{cite journal|title = Polychromatic liquid crystal laser arrays towards display applications|journal = Optics Express|year = 2008|first = Stephen M.|last = Morris|author2=Philip JW Hands |author3=Sonja Findeisen-Tandel |author4=Robert H. Cole |author5=Timothy D. Wilkinson |author6=Harry J. Coles |volume = 16|issue = 23|pages = 18827–37| doi=10.1364/OE.16.018827|pmid = 19581971|url=http://www-g.eng.cam.ac.uk/CMMPE/OE_16_23_2008.pdf|bibcode = 2008OExpr..1618827M |doi-access = free}}</ref>
* <ref name="Morris2009">{{cite journal|title = Removing the discontinuous shifts in emission wavelength of a chiral nematic liquid crystal laser|journal = Journal of Applied Physics|date = 2009-07|first = SM|last = Morris|coauthors = AD Ford, and HJ Coles|volume = 106|issue = 2|pages = 023112| doi=10.1063/1.3177251|bibcode = 2009JAP...106b3112M }}</ref>
* <ref name="Morris2009">{{cite journal|title = Removing the discontinuous shifts in emission wavelength of a chiral nematic liquid crystal laser|journal = Journal of Applied Physics|date = July 2009|first = SM|last = Morris|author2=AD Ford |author3=HJ Coles |volume = 106|issue = 2|pages = 023112–023112–4| doi=10.1063/1.3177251|bibcode = 2009JAP...106b3112M }}</ref>
* <ref name="Palffy-Muhoray2006">{{cite journal|title = Photonics and lasing in liquid crystal materials|journal = Philosophical Transactions of the Royal Society A|year = 2006|first = Peter|last = Palffy-Muhoray|coauthors = Wenyi Cao, Michele Moreira, Bahman Taheri, and Antonio Munoz|volume = 364|issue = 1847|pages = 2747–2761| doi=10.1098/rsta.2006.1851|bibcode = 2006RSPTA.364.2747P }}</ref>
* <ref name="Palffy-Muhoray2006">{{cite journal|title = Photonics and lasing in liquid crystal materials|journal = Philosophical Transactions of the Royal Society A|year = 2006|first = Peter|last = Palffy-Muhoray|author2=Wenyi Cao |author3=Michele Moreira |author4=Bahman Taheri |author5=Antonio Munoz |volume = 364|issue = 1847|pages = 2747–2761| doi=10.1098/rsta.2006.1851|pmid = 16973487|bibcode = 2006RSPTA.364.2747P | s2cid=20644720 }}</ref>
* <ref name="Ozaki2002">{{cite journal|title = Mirrorless lasing in a dye-doped ferroelectric liquid crystal|journal = Advanced Materials|year = 2002|first = M.|last = Ozaki|coauthors = M. Kasano, D. Ganzke, W. Haase, K. Yoshino|volume = 14|issue = 4|pages = 306–309|accessdate = 2011-04-23|doi = 10.1002/1521-4095(20020219)14:4<306::AID-ADMA306>3.0.CO;2-1}}</ref>
* <ref name="Ozaki2002">{{cite journal|title = Mirrorless lasing in a dye-doped ferroelectric liquid crystal|journal = Advanced Materials|year = 2002|first = M.|last = Ozaki|author2=M. Kasano |author3=D. Ganzke |author4=W. Haase |author5=K. Yoshino |volume = 14|issue = 4|pages = 306–309|doi = 10.1002/1521-4095(20020219)14:4<306::AID-ADMA306>3.0.CO;2-1| bibcode=2002AdM....14..306O }}</ref>
* <ref name="Physorg2005">{{cite news|title = Liquid crystal lasers the size of a human hair|date = 2005-12|url = http://www.physorg.com/news8993.html|work = Physorg|accessdate = 2011-04-09}}</ref>
* <ref name="Physorg2005">{{cite news|title = Liquid crystal lasers the size of a human hair|date = December 2005|url = http://www.physorg.com/news8993.html|work = Physorg|accessdate = 2011-04-09}}</ref>
* <ref name="Physorg2009">{{cite news|title = Liquid crystal lasers promise cheaper, high colour resolution laser television|date = 2009-04|url = http://www.physorg.com/news159458998.html|work = Physorg|accessdate = 2011-04-09}}</ref>
* <ref name="Physorg2009">{{cite news|title = Liquid crystal lasers promise cheaper, high colour resolution laser television|date = April 2009|url = http://www.physorg.com/news159458998.html|work = Physorg|accessdate = 2011-04-09}}</ref>
* <ref name="Schmidtke2003">{{cite journal|title = Defect Mode Emission of a Dye Doped Cholesteric Polymer Network|journal = Physical Review Letters|year = 2003|first = Jürgen|last = Schmidtke|coauthors = Werner Stille, and Heino Finkelmann|volume = 90|pages = 083902 |doi=10.1103/PhysRevLett.90.083902 |issue=8 |pmid=12633428 |url=http://homepages.uni-paderborn.de/juergen2/prl03_083902_90.pdf |accessdate=2011-04-29 |bibcode = 2003PhRvL..90h3902S }}</ref>
* <ref name="Schmidtke2003">{{cite journal|title = Defect Mode Emission of a Dye Doped Cholesteric Polymer Network|journal = Physical Review Letters|year = 2003|first = Jürgen|last = Schmidtke|author2=Werner Stille |author3=Heino Finkelmann |volume = 90|pages = 083902 |doi=10.1103/PhysRevLett.90.083902 |issue=8 |pmid=12633428 |url=http://homepages.uni-paderborn.de/juergen2/prl03_083902_90.pdf |accessdate=2011-04-29 |bibcode = 2003PhRvL..90h3902S }}</ref>
* <ref name="Yablonovich1987">{{cite journal|title = Inhibited Spontaneous Emission in Solid-State Physics and Electronics|journal = Physical Review Letters|year = 1987|first = Eli|last = Yablonovich|volume = 58|pages = 2059–2062| doi=10.1103/PhysRevLett.58.2059|issue = 20|pmid = 10034639|bibcode = 1987PhRvL..58.2059Y }}</ref>
* <ref name="Yablonovich1987">{{cite journal|title = Inhibited Spontaneous Emission in Solid-State Physics and Electronics|journal = Physical Review Letters|year = 1987|first = Eli|last = Yablonovich|volume = 58|pages = 2059–2062| doi=10.1103/PhysRevLett.58.2059|issue = 20|pmid = 10034639|bibcode = 1987PhRvL..58.2059Y |doi-access = free}}</ref>
* <ref name=CWandPulsed>{{cite web|last1 = Jacobs|last2 = Cerqua|last3 = Marshall|last4 = Schmid|last5 = Guardalben|last6 =Skerrett| title = Liquid-crystal laser optics: design, fabrication, and performance
* <ref name=CWandPulsed>{{Cite journal|last1 = Jacobs|last2 = Cerqua|last3 = Marshall|last4 = Schmid|last5 = Guardalben|last6 =Skerrett| title = Liquid-crystal laser optics: design, fabrication, and performance
| publisher = [[Optical Society of America]]|doi=10.1364/JOSAB.5.001962| year = 1988| accessdate = 2011-04-26}}</ref>
|journal = Journal of the Optical Society of America B|volume = 5|issue = 9|pages = 1962|doi=10.1364/JOSAB.5.001962| year = 1988|bibcode = 1988JOSAB...5.1962J}}</ref>
* <ref name=Patent>Lawrence Goldberg and Joel Schnur ''Tunable internal-feedback liquid crystal-dye laser'' {{US patent|3771065}} Issue date: 1973</ref>
* <ref name=Patent>Lawrence Goldberg and Joel Schnur ''Tunable internal-feedback liquid crystal-dye laser'' {{US patent|3771065}} Issue date: 1973</ref>
* <ref name=Lee2009>{{cite journal |title=Band-tunable color cone lasing emission based on dye-doped cholesteric liquid crystals with various pitches and a pitch gradient |first1=C.-R. |last1=Lee |first2=S.-H. |last2=Lin |first3=H.-C. |last3=Yeh |first4=T.-D. |last4=Ji |date=7 December 2009 |volume=17 |issue=25 |journal=Optics Express |url=http://myweb.ncku.edu.tw/~crlee/NCKU/file/Band-tunable%20color%20cone%20lasing%20emission%20based%20on%20dye-doped%20cholesteric%20liquid%20crystals%20with%20various%20pitches%20and%20a%20pitch%20gradient.pdf}}</ref>
* <ref name=Lee2009>{{cite journal |title=Band-tunable color cone lasing emission based on dye-doped cholesteric liquid crystals with various pitches and a pitch gradient |first1=C.-R. |last1=Lee |first2=S.-H. |last2=Lin |first3=H.-C. |last3=Yeh |first4=T.-D. |last4=Ji |date=7 December 2009 |volume=17 |issue=25 |pages=22616–23 |journal=Optics Express |url=http://myweb.ncku.edu.tw/~crlee/NCKU/file/Band-tunable%20color%20cone%20lasing%20emission%20based%20on%20dye-doped%20cholesteric%20liquid%20crystals%20with%20various%20pitches%20and%20a%20pitch%20gradient.pdf|doi=10.1364/oe.17.022616 |pmid=20052187 |bibcode = 2009OExpr..1722616L |doi-access=free }}</ref>
}} <!--ends reflist 2 -->
}} <!--ends reflist 2 -->


==Bibliography==
==Bibliography==
* <div id="Woltman_2007"></div>{{cite book|last1 = Woltman|first1 = Scott J.|last2 = Crawford|first2 = Gregory Philip|last3 = Jay|first3 = Gregory D.|title = Liquid crystals: frontiers in biomedical applications|publisher = World Scientific|year = 2007 |isbn = 9789812705457}}
* <div id="Woltman_2007"></div>{{cite book|last1 = Woltman|first1 = Scott J.|last2 = Crawford|first2 = Gregory Philip|last3 = Jay|first3 = Gregory D.|title = Liquid crystals: frontiers in biomedical applications|publisher = World Scientific|year = 2007 |isbn = 978-981-270-545-7}}


==Further reading==
==Further reading==
* {{cite journal|title = Liquid-crystal lasers|journal = Nature Photonics|year = 2010|first = Harry|last = Coles|coauthors = Stephen Morris|volume = 4|pages = 676–685| doi=10.1038/nphoton.2010.184|issue = 10|bibcode = 2010NaPho...4..676C }}
* {{cite journal|doi=10.1515/nanoph-2021-0096 |title=Liquid crystal lasers: The last decade and the future |date=2021 |last1=Mysliwiec |first1=Jaroslaw |last2=Szukalska |first2=Alina |last3=Szukalski |first3=Adam |last4=Sznitko |first4=Lech |journal=Nanophotonics |volume=10 |issue=9 |pages=2309–2346 |bibcode=2021Nanop..10...96M |doi-access=free }}
*{{cite journal|title = Liquid-crystal lasers|journal = Nature Photonics|year = 2010|first = Harry|last = Coles|author2=Stephen Morris |volume = 4|pages = 676–685| doi=10.1038/nphoton.2010.184|issue = 10|bibcode = 2010NaPho...4..676C }}
* {{cite book|last1 = Joannopoulos|first1 = John D.|last2 = Johnson|first2 = Steven G.|last3 = Winn|first3 = Joshua N.|last4 = Meade|first4 = Robert D.|title = Photonic Crystals: Molding the Flow of Light|publisher = Princeton University Press|year = 2008|url = http://ab-initio.mit.edu/book/|accessdate = 2011-04-10|isbn = 9780691124568}}
* {{cite book|last1 = Joannopoulos|first1 = John D.|last2 = Johnson|first2 = Steven G.|last3 = Winn|first3 = Joshua N.|last4 = Meade|first4 = Robert D.|title = Photonic Crystals: Molding the Flow of Light|publisher = Princeton University Press|year = 2008|url = http://ab-initio.mit.edu/book/|accessdate = 2011-04-10|isbn = 978-0-691-12456-8}}

==External links==
*[http://homepages.uni-paderborn.de/juergen2/lcphotonics.html a list of papers related to photonic properties of chiral liquid crystals]


{{Display Technology}}
{{Display technology}}


[[Category:Lasers]]
[[Category:Laser types]]
[[Category:Liquid crystals]]
[[Category:Liquid crystals]]
[[Category:Optical materials]]
[[Category:Optical materials]]

Latest revision as of 04:55, 18 November 2024

A liquid-crystal laser is a laser that uses a liquid crystal as the resonator cavity, allowing selection of emission wavelength and polarization from the active laser medium. The lasing medium is usually a dye doped into the liquid crystal. Liquid-crystal lasers are comparable in size to diode lasers, but provide the continuous wide spectrum tunability of dye lasers while maintaining a large coherence area. The tuning range is typically several tens of nanometers.[1] Self-organization at micrometer scales reduces manufacturing complexity compared to using layered photonic metamaterials. Operation may be either in continuous wave mode or in pulsed mode.[2]

History

[edit]

Distributed feedback lasing using Bragg reflection of a periodic structure instead of external mirrors was first proposed in 1971,[3] predicted theoretically with cholesteric liquid crystals in 1978,[4] achieved experimentally in 1980,[5] and explained in terms of a photonic band gap in 1998.[6][7][8] A United States Patent issued in 1973 described a liquid-crystal laser that uses "a liquid lasing medium having internal distributed feedback by virtue of the molecular structure of a cholesteric liquid-crystal material."[9]

Mechanism

[edit]

Starting with a liquid crystal in the nematic phase, the desired helical pitch (the distance along the helical axis for one complete rotation of the nematic plane subunits) can be achieved by doping the liquid crystal with a chiral molecule.[8] For light circularly polarized with the same handedness, this regular modulation of the refractive index yields selective reflection of the wavelength given by the helical pitch, allowing the liquid-crystal laser to serve as its own resonator cavity. Photonic crystals are amenable to band theory methods, with the periodic dielectric structure playing the role of the periodic electric potential and a photonic band gap (reflection notch) corresponding to forbidden frequencies. The lower photon group velocity and higher density of states near the photonic bandgap suppresses spontaneous emission and enhances stimulated emission, providing favorable conditions for lasing.[7][10] If the electronic band edge falls in the photonic bandgap, electron-hole recombination is strictly suppressed.[11] This allows for devices with high lasing efficiency, low lasing threshold, and stable frequency, where the liquid-crystal laser acts its own waveguide. "Colossal" nonlinear change in refractive index is achievable in doped nematic-phase liquid crystals, that is the refractive index can change with illumination intensity at a rate of about 103cm2/W of illumination intensity.[12][13][14] Most systems use a semiconductor pumping laser to achieve population inversion, though flash lamp and electrical pumping systems are possible.[15]

Tuning of the output wavelength is achieved by smoothly varying the helical pitch: as the winding changes, so does the length scale of the crystal. This in turn shifts the band edge and changes the optical path length in the lasing cavity. Applying a static electric field perpendicular to the dipole moment of the local nematic phase rotates the rod-like subunits in the hexagonal plane and reorders the chiral phase, winding or unwinding the helical pitch.[16] Similarly, optical tuning of the output wavelength is available using laser light far from the pick-up frequency of the gain medium, with degree of rotation governed by intensity and the angle between the polarization of the incident light and the dipole moment.[17][18][19] Reorientation is stable and reversible. The chiral pitch of a cholesteric phase tends to unwind with increasing temperature, with a disorder-order transition to the higher symmetry nematic phase at the high end.[5][20][21][22] By applying a temperature gradient perpendicular to the direction of emission varying the location of stimulation, frequency may be selected across a continuous spectrum.[23] Similarly, a quasi-continuous doping gradient yields multiple laser lines from different locations on the same sample.[15] Spatial tuning may also be accomplished using a wedge cell. The boundary conditions of the narrower cell squeeze the helical pitch by requiring a particular orientation at the edge, with discrete jumps where the outer cells rotate to the next stable orientation; frequency variation between jumps is continuous.[24]

If a defect is introduced into the liquid crystal to disturb the periodicity, a single allowed mode may be created inside of the photonic bandgap, reducing power leeching by spontaneous emission at adjacent frequencies. Defect mode lasing was first predicted in 1987, and was demonstrated in 2003.[11][25][26]

While most such thin films lase on the axis normal to the film's surface, some will lase on a conic angle around that axis.[27]

Applications

[edit]
  • Biomedical sensing: small size, low cost, and low power consumption offer a variety of advantages in biomedical sensing applications. Potentially, liquid-crystal lasers could form the basis for "lab on a chip" devices that provide immediate readings without sending a sample away to a separate lab.[28]
  • Medical: low emission power limits such medical procedures as cutting during surgeries, but liquid-crystal lasers show potential to be used in microscopy techniques and in vivo techniques such as photodynamic therapy.[1]
  • Display screens: liquid-crystal-laser-based displays offer most of the advantages of standard liquid-crystal displays, but the low spectral spread gives more precise control over color. Individual elements are small enough to act as single pixels while retaining high brightness and color definition. A system in which each pixel is a single spatially tuned device could avoid the sometimes long relaxation times of dynamic tuning, and could emit any color using spatial addressing and the same monochromatic pumping source.[28][29][30]
  • Environmental sensing: using a material with a helical pitch highly sensitive to temperature, electric field, magnetic field, or mechanical strain, color shift of the output laser provides a simple, direct measurement of environmental conditions.[31]

References

[edit]
  1. ^ a b Woltman 2007, p. 357
  2. ^ Jacobs; Cerqua; Marshall; Schmid; Guardalben; Skerrett (1988). "Liquid-crystal laser optics: design, fabrication, and performance". Journal of the Optical Society of America B. 5 (9): 1962. Bibcode:1988JOSAB...5.1962J. doi:10.1364/JOSAB.5.001962.
  3. ^ Kogelnik, H.; C.V. Shank (1971). "Stimulated emission in a periodic structure". Applied Physics Letters. 18 (4): 152. Bibcode:1971ApPhL..18..152K. doi:10.1063/1.1653605.
  4. ^ Kukhtarev, NV (1978). "Cholesteric liquid crystal laser with distributed feedback". Soviet Journal of Quantum Electronics. 8 (6): 774–776. Bibcode:1978QuEle...8..774K. doi:10.1070/QE1978v008n06ABEH010397.
  5. ^ a b Ilchishin, I.P.; E.A. Tikhonov; V.G. Tishchenko; M.T. Shpak (1980). "Generation of a tunable radiation by impurity cholesteric liquid crystals". Journal of Experimental and Theoretical Physics Letters. 32: 24–27. Bibcode:1980JETPL..32...24I.
  6. ^ Woltman 2007, p. 310
  7. ^ a b Kopp, V.I.; B. Fan; H. K. M. Vithana; A. Z. Genack (1998). "Low-threshold lasing at the edge of a photonic stop band in cholesteric liquid crystals". Optics Express. 23 (21): 1707–1709. Bibcode:1998OptL...23.1707K. doi:10.1364/OL.23.001707. PMID 18091891. S2CID 17966093.
  8. ^ a b Dolgaleva, Ksenia; Simon K.H. Wei; Svetlana G. Lukishova; Shaw H. Chen; Katie Schwertz; Robert W. Boyd (2008). "Enhanced laser performance of cholesteric liquid crystals doped with oligofluorene dye". Journal of the Optical Society of America. 25 (9): 1496–1504. Bibcode:2008JOSAB..25.1496D. doi:10.1364/JOSAB.25.001496.
  9. ^ Lawrence Goldberg and Joel Schnur Tunable internal-feedback liquid crystal-dye laser U.S. patent 3,771,065 Issue date: 1973
  10. ^ Kuroda, Keiji; Tsutomu Sawada; Takashi Kuroda; Kenji Watanabe; Kazuaki Sakoda (2009). "Doubly enhanced spontaneous emission due to increased photon density of states at photonic band edge frequencies". Optics Express. 17 (15): 13168–13177. Bibcode:2009OExpr..1713168K. doi:10.1364/OE.17.013168. PMID 19654722.
  11. ^ a b Yablonovich, Eli (1987). "Inhibited Spontaneous Emission in Solid-State Physics and Electronics". Physical Review Letters. 58 (20): 2059–2062. Bibcode:1987PhRvL..58.2059Y. doi:10.1103/PhysRevLett.58.2059. PMID 10034639.
  12. ^ Lucchetti, L.; M. Di Fabrizio; O. Francescangeli; F. Simoni (2004). "Colossal optical nonlinearity in dye doped liquid crystals". Optics Communications. 233 (4–6): 417–424. Bibcode:2004OptCo.233..417L. doi:10.1016/j.optcom.2004.01.057.
  13. ^ Khoo, I.C. (1995). "Holographic grating formation in dye- and fullerene C60-doped nematic liquid-crystal film". Optics Letters. 20 (20): 2137–2139. Bibcode:1995OptL...20.2137K. doi:10.1364/OL.20.002137. PMID 19862276.
  14. ^ Khoo, Iam-Choo (2007). Liquid Crystals. Wiley-Interscience. ISBN 978-0-471-75153-3.
  15. ^ a b Morris, Stephen M.; Philip JW Hands; Sonja Findeisen-Tandel; Robert H. Cole; Timothy D. Wilkinson; Harry J. Coles (2008). "Polychromatic liquid crystal laser arrays towards display applications" (PDF). Optics Express. 16 (23): 18827–37. Bibcode:2008OExpr..1618827M. doi:10.1364/OE.16.018827. PMID 19581971.
  16. ^ Maune, Brett; Marko Lončar; Jeremy Witzens; Michael Hochberg; Thomas Baehr-Jones; Demetri Psaltis; Axel Scherer; Yueming Qiu (2004). "Liquid-crystal electric tuning of a photonic crystal laser" (PDF). Applied Physics Letters. 85 (3): 360. Bibcode:2004ApPhL..85..360M. doi:10.1063/1.1772869.
  17. ^ Furumi, Seiichi; Shiyoshi Yokoyama; Akira Otomo; Shinro Mashiko (2004). "Phototunable photonic bandgap in chiral liquid crystal device". Applied Physics Letters. 84 (14): 2491. Bibcode:2004ApPhL..84.2491F. doi:10.1063/1.1699445.
  18. ^ Andy, Fuh; Tsung-Hsien Lin; J.-H. Liu; F.-C. Wu (2004). "Lasing in chiral photonic liquid crystals and associated frequency tuning". Optics Express. 12 (9): 1857–1863. Bibcode:2004OExpr..12.1857F. doi:10.1364/OPEX.12.001857. PMID 19475016.
  19. ^ Khoo, Iam-Choo; Wu, Shin-Tson (1993). Optics and nonlinear optics of liquid crystals. World Scientific. ISBN 978-981-02-0934-6.
  20. ^ Morris, S.M.; A. D. Ford; M. N. Pivnenko; H. J. Coles (2005). "Enhanced emission from liquid-crystal lasers". Journal of Applied Physics. 97 (2): 023103–023103–9. Bibcode:2005JAP....97b3103M. doi:10.1063/1.1829144.
  21. ^ Morris, SM; AD Ford; HJ Coles (July 2009). "Removing the discontinuous shifts in emission wavelength of a chiral nematic liquid crystal laser". Journal of Applied Physics. 106 (2): 023112–023112–4. Bibcode:2009JAP...106b3112M. doi:10.1063/1.3177251.
  22. ^ Ozaki, M.; M. Kasano; D. Ganzke; W. Haase; K. Yoshino (2002). "Mirrorless lasing in a dye-doped ferroelectric liquid crystal". Advanced Materials. 14 (4): 306–309. Bibcode:2002AdM....14..306O. doi:10.1002/1521-4095(20020219)14:4<306::AID-ADMA306>3.0.CO;2-1.
  23. ^ Huang, Yuhua; Ying Zhou; Shin-Tson Wu (2006). "Spatially tunable laser emission in dye-doped photonic liquid crystals". Applied Physics Letters. 88 (1): 011107. Bibcode:2006ApPhL..88a1107H. doi:10.1063/1.2161167. S2CID 119500768.
  24. ^ Jeong, Mi-Yun; Hyunhee Choi; J. W. Wu (2008). "Spatial tuning of laser emission in a dye-doped cholesteric liquid crystal wedge cell". Applied Physics Letters. 92 (5): 051108. Bibcode:2008ApPhL..92e1108J. doi:10.1063/1.2841820.
  25. ^ Woltman 2007, pp. 332–334
  26. ^ Schmidtke, Jürgen; Werner Stille; Heino Finkelmann (2003). "Defect Mode Emission of a Dye Doped Cholesteric Polymer Network" (PDF). Physical Review Letters. 90 (8): 083902. Bibcode:2003PhRvL..90h3902S. doi:10.1103/PhysRevLett.90.083902. PMID 12633428. Retrieved 2011-04-29.
  27. ^ Lee, C.-R.; Lin, S.-H.; Yeh, H.-C.; Ji, T.-D. (7 December 2009). "Band-tunable color cone lasing emission based on dye-doped cholesteric liquid crystals with various pitches and a pitch gradient" (PDF). Optics Express. 17 (25): 22616–23. Bibcode:2009OExpr..1722616L. doi:10.1364/oe.17.022616. PMID 20052187.
  28. ^ a b "Liquid crystal lasers the size of a human hair". Physorg. December 2005. Retrieved 2011-04-09.
  29. ^ "Liquid crystal lasers promise cheaper, high colour resolution laser television". Physorg. April 2009. Retrieved 2011-04-09.
  30. ^ "Laser Displays: liquid-crystal laser promises low-fabrication-cost display". Laser Focus World. January 2009. Retrieved 2011-04-09.
  31. ^ Palffy-Muhoray, Peter; Wenyi Cao; Michele Moreira; Bahman Taheri; Antonio Munoz (2006). "Photonics and lasing in liquid crystal materials". Philosophical Transactions of the Royal Society A. 364 (1847): 2747–2761. Bibcode:2006RSPTA.364.2747P. doi:10.1098/rsta.2006.1851. PMID 16973487. S2CID 20644720.

Bibliography

[edit]
  • Woltman, Scott J.; Crawford, Gregory Philip; Jay, Gregory D. (2007). Liquid crystals: frontiers in biomedical applications. World Scientific. ISBN 978-981-270-545-7.

Further reading

[edit]
[edit]
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