Electrical fine tuning of liquid crystal lasers

Schmidtke, Jürgen; Jünnemann, Gisela; Keuker‐Baumann, Susanne; Kitzerow, Heinz‐S.

doi:10.1063/1.4739840

Cited by 38 publications

(18 citation statements)

References 17 publications

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“…[1][2][3][4][5][6][7][8][9][10][11] CLC materials possess a unique supramolecular helical structure predetermining their optical properties. Their periodic helical supramolecular structure and high sensitivity to the external fi elds make them very promising stimuli-responsive materials for different applications in photonics, electrooptics, display technology, creation of optical sensors, and other applications.…”

Section: Introductionmentioning

confidence: 99%

“…Their periodic helical supramolecular structure and high sensitivity to the external fi elds make them very promising stimuli-responsive materials for different applications in photonics, electrooptics, display technology, creation of optical sensors, and other applications. [1][2][3][4][5][6][7][8][9][10][11] CLC materials possess a unique supramolecular helical structure predetermining their optical properties. The specifi c values of helix pitch are determined by the chemical structure of substances forming cholesteric mesophase.…”

Section: Introductionmentioning

confidence: 99%

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Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch

Ryabchun

Bobrovsky

Stumpe

et al. 2015

Advanced Optical Materials

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch

Ryabchun

Bobrovsky

Stumpe

et al. 2015

Advanced Optical Materials

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“…In addition direct control and tuning of the PBG are of crucial importance for several emerging applications such as switchable optical devices, lab-on-a-chip devices as sensors 9 , modulators, reflectors and diffraction gratings. External stimuli can be used to tune the PBG such as heat [10][11][12][13] , light [14][15][16] , elasticity 17 and voltage [18][19][20][21][22][23][24][25][26][27][28][29] . In previous work 30 switchable devices with tuneable PBG with a fast response to electrical addressing and tuning over a broad range of wavelengths are demonstrated with a high reproducibility without deformation and degradation (Figure1).…”

Section: Introductionmentioning

confidence: 99%

Effect of UV curing conditions on polymerized tunable chiral nematic liquid crystals

2014

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Chiral nematic liquid crystals have attracted substantial interest. They spontaneously self-organize to form a helical structure with no complex fabrication procedure required and exhibit a reflection band for a certain wavelength interval. Since the photonic band gap can be tuned by applying external factors (heat, voltage, light, elasticity) chiral nematic liquid crystals are potentially interesting for large area optical filters and shutters, reflective displays and tunable lasers. In this work, a device which consists of a mixture of photo-polymerizable liquid crystal, non-reactive nematic liquid crystal and a chiral dopant is fabricated. By selecting the appropriate chiral dopant concentration, it is possible to make devices for different operation wavelengths. The influence of UV illumination on a partially polymerized chiral liquid crystal is investigated. A blue-wavelength shift of the photonic band gap is obtained as a function of power, duration time of UV illumination and the thickness of the cells. Interestingly the width and depth of the photonic band gap is unaffected by the change in UV curing conditions, which indicates that there is no degradation by the UV light.

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“…This can be achieved by changing the temperature (6-8), composition or cell thickness (9)(10)(11), mechanical strain in cross-linked CLC elastomers (12)(13)(14), and using reversible photochemical reactions (15,16). The most sought-after control is via an applied electric field, which, although possible in principle (17)(18)(19)(20)(21)(22)(23), has not yet achieved its full potential. The principal difficulty is created by the very geometry of CLC in which the molecules are oriented perpendicularly to the helical axis, as explained below.…”

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confidence: 99%

Electrically tunable laser based on oblique heliconical cholesteric liquid crystal

Xiang

Varanytsia

Minkowski

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

154

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A cholesteric liquid crystal (CLC) formed by chiral molecules represents a self-assembled one-dimensionally periodic helical structure with pitch p in the submicrometer and micrometer range. Because of the spatial periodicity of the dielectric permittivity, a CLC doped with a fluorescent dye and pumped optically is capable of mirrorless lasing. An attractive feature of a CLC laser is that the pitch p and thus the wavelength of lasing λ can be tuned, for example, by chemical composition. However, the most desired mode to tune the laser, by an electric field, has so far been elusive. Here we present the realization of an electrically tunable laser with λ spanning an extraordinarily broad range (>100 nm) of the visible spectrum. The effect is achieved by using an electric-fieldinduced oblique helicoidal (OH) state in which the molecules form an acute angle with the helicoidal axis rather than align perpendicularly to it as in a field-free CLC. The principal advantage of the electrically controlled CLC OH laser is that the electric field is applied parallel to the helical axis and thus changes the pitch but preserves the single-harmonic structure. The preserved single-harmonic structure ensures efficiency of lasing in the entire tunable range of emission. The broad tuning range of CLC OH lasers, coupled with their microscopic size and narrow line widths, may enable new applications in areas such as diagnostics, sensing, microscopy, displays, and holography.cholesteric liquid crystals | lasing | electric tunability | heliconical structure C hiral interactions in cholesteric liquid crystals (CLCs) result in supramolecular helical structures (1). The nematic directorn defining molecular orientation is perpendicular to the helix axis and rotates continuously along the axis, generating a regular rightangle helix with pitch p. Because the dielectric tensor is periodic in space, the CLC is a 1D photonic bandgap structure, selectively reflecting circularly polarized light of the same handedness as the helix. The reflection band edges are at wavelengths λ o = pn o and λ e = pn e , where n o and n e are, respectively, the ordinary and extraordinary refractive indices of the local uniaxial structure (1).In optically pumped thin layers of CLCs doped with fluorescent dyes, selective Bragg reflection of light gives rise to mirrorless lasing at the reflection band edges. Early demonstrations of lasing from CLCs (2-6) stimulated considerable interest in these easily produced micrometer-sized laser light sources due to their potential in spectroscopic, communications, sensing, and display applications. One major appeal of CLC lasers is the tunability of the emission wavelength by controlling the pitch. This can be achieved by changing the temperature (6-8), composition or cell thickness (9-11), mechanical strain in cross-linked CLC elastomers (12-14), and using reversible photochemical reactions (15, 16). The most sought-after control is via an applied electric field, which, although possible in principle (17-23), has not yet achiev...

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Electrical fine tuning of liquid crystal lasers

Cited by 38 publications

References 17 publications

Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch

Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch

Effect of UV curing conditions on polymerized tunable chiral nematic liquid crystals

Electrically tunable laser based on oblique heliconical cholesteric liquid crystal

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