Mode coupling by scattering in chiral nematic liquid crystal ring lasing

Neyts, Kristiaan; Dadalyan, Tigran; Acker, Frederik Van; Nys, Inge; Beeckman, Jeroen

doi:10.1364/oe.27.008081

Cited by 6 publications

(1 citation statement)

References 22 publications

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“…An investigation of the stop-band structure for an oblique incidence using fluorescence in the framework of the linear optics was reported in [28]. The EM and CEM coupling was also recently investigated in [29], where, in particular, was found that a focusing of the pumping wave promotes the coupling realization (which is in a full agreement with the above discussion).…”

Section: Possible Coupling Between Localized Modessupporting

confidence: 56%

Localized Conical Edge Modes in Optics of Spiral Media (First Diffraction Order)

Belyakov

2019

Crystals

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In cholesteric liquid crystals (CLC) problems related to the localized optical modes for a non-collinear geometry are studied here in the two wave dynamic diffraction theory approximation. This approximation, which insures the results accuracy order of δ (where δ is the CLC dielectric anisotropy), is applied because for a non-collinear geometry there is no exact analytic solution of the Maxwell equations and a theoretical description of the experimental data becomes more complicated. The dispersion equation for non-collinear localized edge modes (called conical modes (CEM)) is found and analytically solved for the case of thick layers and for this case the lasing threshold and the conditions of the anomalously strong absorption effect are found. It is shown that qualitatively CEMs are very similar to the localized edge modes (EM) in CLCs related to a collinear geometry, i.e., for the case of light propagation along the spiral axis however the CEMs differ by their polarization properties (the CEM eigen polarizations are elliptical ones depending on the degree of CEM deviation from the collinear geometry in contrast to the circular eigen polarizations in the EM case). What is concerned of the CEM quantitative values of the parameters they are “worth” (the photonic effects are not so pronounced) than for the corresponding ones for EM. The CEM lasing threshold is higher than the one for EM, etc. Performed theoretical studies of possible conversion of EMs into CEMs showed that it can be due to the EM reflection at dielectric boundaries at the conditions of a high pumping wave focusing. Known experimental results on the CEM are discussed and optimal conditions for CEM observations are formulated.

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Section: Possible Coupling Between Localized Modessupporting

confidence: 56%

Localized Conical Edge Modes in Optics of Spiral Media (First Diffraction Order)

Belyakov

2019

Crystals

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Single Order Diffraction at a Negative Angle Based on a Chiral Liquid Crystal with an Inclined Helix

Stebryte,

Nys,

Beeckman

et al. 2024

ACS Appl. Opt. Mater.

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Negative refraction is a phenomenon in which light, when striking a material at an oblique angle, undergoes refraction toward the same side with respect to the surface normal. Over the past two decades, various approaches have emerged for creating materials exhibiting this unique property that is absent in nature. These methods comprise metamaterials as well as diverse techniques for tuning liquid crystal or photonic crystals containing liquid crystals utilizing birefringence of the material. This work demonstrates diffraction-based beam steering at a large angle to a negative direction with an efficiency greater than 85%, for incident light over an angular range of approximately 20°. The component is based on a chiral liquid crystal grating with an inclined helical axis, which is normally used in reflective mode and has a positive index of refraction. Here, the diffractive properties are used in the transmission mode, which can be utilized in other applications. The conditions for the angle of incidence and wavelength are derived based on a k-vector diagram. The diffraction angle and efficiency of the grating are simulated, and the properties are measured for a fabricated device.

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