How doping a cholesteric liquid crystal with polymeric dye improves an order parameter and makes possible low threshold lasing

Araoka, Fumito; Shin, Kwang-Bok; Takanishi, Yoichi; Ishikawa, Ken; Takezoe, Hideo; Zhu, Zhengguo; Swager, Timothy M.

doi:10.1063/1.1578534

Cited by 133 publications

(76 citation statements)

References 14 publications

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“…A higher order parameter for the dye favors the coupling between the dye emission and the LWE emission and reduces the coupling with the SWE in that d t // n LC . 18 This leads to suppressed optical gain at the SWE and enhanced gain at the LWE, as shown in FIG. 1(c).…”

Section: 22mentioning

confidence: 98%

Electrically assisted bandedge mode selection of photonic crystal lasing in chiral nematic liquid crystals

Wang

Chen

Yang

et al. 2018

Applied Physics Letters

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Selection of the bandedge lasing mode of a photonic crystal laser has been realized in a fluorescent dye doped chiral nematic liquid crystal by exerting electrical control over the mode competition. The bandedge lasing can be reversibly switched from the short-wavelength edge mode to the long-wavelength edge mode by applying a voltage of only 20 V, without tuning the bandgap. The underlying mechanism is the field-induced change in the order parameter of the fluorescent dye in the liquid crystal. The orientation of the transition dipole moment determines the polarization state of the dye emission, thereby promoting lasing in the bandedge mode that favors the emission polarization. Moreover, the dynamic mode-selection capability is retained upon polymer-stabilizing the chiral nematic liquid crystal laser. In the polymer-stabilized system, greatly improved stability and lasing performance are observed. The lasing behavior in chiral nematic liquid crystals (CLC) has been extensively studied over the past decades due to its favorable properties, such as low threshold, high tunability, and the ease of fabrication. [1][2][3] CLC is a particular class of liquid crystals in which the molecules self-assemble into one-dimensional helices, typically formed by mixing a nematic liquid crystal with a chiral agent. The concentration and twisting power of the chiral agent determine the helical pitch (p). Such a periodic chiral structure can be regarded as a one-dimensional photonic crystal for a circularly polarized probe with the same handedness as that of the structure. The associated photonic bandgap (PBG) is located at λ c = n c ⋅p with a bandwidth Δλ = Δn⋅p, where n c and Δn are the average refractive index and birefringence of the CLC, respectively. Resonances occur at the two bandedges: long wavelength edge (LWE) and short wavelength edge (SWE); the corresponding wavelengths are λ LWE = n e ⋅p and λ SWE = n o ⋅p, respectively, where n e is the extraordinary refractive index and n o is the ordinary refractive index. At the bandedge, the group velocity of light approaches zero, and hence the density of states is significantly enhanced. 4,5 In the presence of a gain medium, laser action can occur at the photonic bandedge(s) through optical excitation-usually termed the bandedge lasing. To date, a great deal of effort has been devoted to achieve a wide dynamic tuning range of the lasing wavelength with the aid of external inputs, such as electric field 6,7 , heat 8,9 , light 10 , and mechanical stress 11 . However, the post-

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Section: 22mentioning

confidence: 98%

Electrically assisted bandedge mode selection of photonic crystal lasing in chiral nematic liquid crystals

Wang

Chen

Yang

et al. 2018

Applied Physics Letters

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“…It was found that lasing always occurs at the lower-energy edge of the photonic gap [31]. Figure 2 indicates an emission spectrum above the threshold energy (E threshold ) at 60℃.…”

Section: Lasing In Dye Doped Cholesteric Liquid Crystalmentioning

confidence: 99%

Lasing Characteristics of Dye-Doped Cholesteric Liquid Crystal

Porov¹,

Chandel²,

Manohar³

2015

Transactions on Electrical and Electronic Materials

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Cholesteric liquid crystals naturally form helical structures with the helical pitch in an optical wavelength range [7]. The dye and cholesteric liquid crystal molecules are together subjected to the electric field action, which produces a collective movement that leads to changes in molecular arrangement, notably the applied electric field direction. As a result of the applied field, the helical molecular arrangement axis is perpendicular to the electric field direction and then produces an increase in the helical structure pitch [8,9].A cholesteric liquid crystal can be considered as a one-dimensional photonic crystal with a refractive index that is regularly modulated along the helix axis because of the particular arrangement of the molecules. The result is that the propagation of light is suppressed for a particular range of wavelength [10]. Preeti Porov† and Vishal Singh Chandel Department of Physics, Integral University, Lucknow 226026, IndiaReceived January 8, 2015; Revised April 9, 2015; Accepted May 3, 2015Cholesteric liquid crystals are one dimensional photonic band-gap materials due to their birefringence and periodic structure. Dye doped cholesteric liquid crystals are self-assembling, mirror-less, low threshold laser structures that exhibit distributed feedback. In this review paper, we have presented the development in the field of lasing characteristics of dye doped cholesteric liquid crystals.

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“…We have shown previously that this arrangement produces lowthreshold and efficient single-mode lasing. [5,6] Reflectance spectra were acquired using a microscope spectrometer (TFM-120AFT-PC, ORC). For fluorescence and lasing measurements, a 440 nm pulsed laser beam from an optical parametric oscillator (Surelite OPO; HOYA Continuum) pumped by third-harmonic light from a Nd:YAG (yttrium aluminum garnet) laser was used as the optical pumping source.…”

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confidence: 99%

Effect of Phase Retardation on Defect‐Mode Lasing in Polymeric Cholesteric Liquid Crystals

et al. 2004

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Lasing via a phase retardation defect mode is reported for the first time. The Figure shows the far‐field pattern of laser emission realized by inserting an anisotropic nematic liquid crystal (LC) defect layer between polymer cholesteric LC layers. The system mimics the cuticle of Plusiotis resplendens, a beetle, using the birefringence of the anisotropic layer to achieve reflectance greater than the 50 % provided by simple cholesteric LC photonic bandgaps.

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How doping a cholesteric liquid crystal with polymeric dye improves an order parameter and makes possible low threshold lasing

Cited by 133 publications

References 14 publications

Electrically assisted bandedge mode selection of photonic crystal lasing in chiral nematic liquid crystals

Electrically assisted bandedge mode selection of photonic crystal lasing in chiral nematic liquid crystals

Lasing Characteristics of Dye-Doped Cholesteric Liquid Crystal

Effect of Phase Retardation on Defect‐Mode Lasing in Polymeric Cholesteric Liquid Crystals

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