Laser-induced diffraction rings from a nematic-liquid-crystal film

Durbin, Stephen D.; Аракелян, С. М.; Shen, Y. R.

doi:10.1364/ol.6.000411

Cited by 453 publications

(250 citation statements)

References 6 publications

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“…[54] The linear refractive index of the as-prepared suspension derived by the same method as in the literature [27] 532 nm, 633 nm and 800 nm, respectively. The phase shift ψ when a laser beam passes through the bismuthene suspension is given as…”

Section: Sspm Of Bismuthenementioning

confidence: 99%

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability

Liang

et al. 2017

Laser & Photonics Reviews

344

206

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As the last element in Group VA, bismuthene has garnered substantial interest for its unique electronic and mechanical properties and its enhanced stability. However, the mechanism that drives the light-bismuthene interaction remains completely unclear. Herein, a sonochemical exfoliation approach is employed to deliver a successful synthesis of few-layer bismuthene. The corresponding nonlinear optical response at the visible wavelength is investigated. The nonlinear refractive index is ß10 −6 cm 2 /W and was measured by spatial self-phase modulation. Thanks to its direct energy band-gap at 1550 nm, the saturable absorption property of bismuthene is experimentally illustrated at the telecommunication band with an optical modulation depth of ß2.03% and a saturable intensity of ß30 MW/cm 2 . The optimization of the laser parameters resulted in the generation of an ß652-femtosecond optical pulse centered at 1559.18 nm. This result indicates that the bismuthene-based saturable absorber is indeed a new and excellent material for an ultrafast saturable absorber device. Our work highlights the promise of this material in ultrafast photonics and may be considered as an important step towards bismuthene-based photonics devices (optical modulator, optical switcher, detector, etc.).

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Section: Sspm Of Bismuthenementioning

confidence: 99%

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability

Liang

et al. 2017

Laser & Photonics Reviews

344

206

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“…The SSPM is a coherent third-order nonlinear optical process systematically investigated decades ago (22), where the nonlinear optical susceptibility χ (3) is uniquely determined by the laser-intensity-dependent refractive index n = n 0 + n 2 I, where n 0 and n 2 are linear and nonlinear refractive indexes, respectively. If this effect is strong enough in a material, the phenomenon of selffocusing can be directly observed.…”

mentioning

confidence: 99%

Emergence of electron coherence and two-color all-optical switching in MoS ₂ based on spatial self-phase modulation

Sun

et al. 2015

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

148

207

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Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS 2 flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibility χ (3) measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A windchime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials.electron coherence | transition metal dichalcogenide | self-phase modulation | optical switching | emergent phenomena R ecently 2D layered quantum materials have attracted tremendous interest since the discovery of graphene a decade ago (1). Various layered materials, ranging from boron nitride sheets to transition metal dichalcogenides and from topological insulators to high-temperature superconductors, have been intensively investigated (2-11). Strict 2D atomic crystals can now be produced at a macroscopic scale, using a variety of methods (11,12). Among them molybdenum disulfide (MoS 2 ) and related layered quantum materials are particularly interesting due to their novel optical properties and potential valleytronics applications (4,5,8,9) at a thickness of monolayer and few layers (2, 10, 13). Layered materials share common physical properties rooted in their ubiquitous 2D quantum nature, for which achieving pure coherence among electrons (lattices) is of particular interest (14-19). The presence of multiple domains is ubiquitous in many known 2D quantum materials, ranging from stripe-order cuprate superconductors to polycrystalline strongly correlated systems. For example, phase locking between different layers of stripe orders is crucial for enhancing the superconducting phase in layered hightemperature superconductors (20,21).In this work we demonstrate unambiguously that nonlocal and intraband ac electron coherence, of which the electronic wave function oscillates at an optical frequency of 10 14 Hz, can be generated in separate MoS 2 flakes, using spatial self-phase modulation (SSPM). The SSPM is a coherent third-order nonlinear optical process systematically investigated decades ago (22), where the nonlinear optical susceptibility χ (3) is uniquely determined by the laser-intensity-dependent refractive index n = n 0 + n 2 I, where n 0 and n 2 are linear and nonlinear refractive indexes, respectively. If this effect is strong enough in a material, the phenomenon of selffocusing can be directly observed. The SSPM is also f...

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“…This assumption was confirmed by direct evaluation of optical nonlinearity in self-diffraction ring measurements. 15,16,39 The following experiments were carried out on PSLC cells treated with silane coupler concentrations above 0.003 wt% because these concentrations yielded a uniform homeotropic orientation. Effect of surface treatment on molecular reorientation K Usui et al…”

Section: Evaluation Of Optical Nonlinearity Of Pslcsmentioning

confidence: 99%

“…Therefore, the molecular reorientation behavior can be evaluated quantitatively by counting the number of rings (N) associated with the photoinduced refractive index change Δn′ using the following equation, N = |Δn′ | L λ − 1 (λ: wavelength, 488 nm; L: cell thickness, 100 μm). 39 The value of Δn′ was estimated to be 0.13. It is noteworthy that molecules are reoriented almost parallel to the polarization direction of the incident beam by assuming that the birefringence of the PSLCs is equivalent to that of the host liquid crystal, 5CB.…”

Section: Evaluation Of Optical Nonlinearity Of Pslcsmentioning

confidence: 99%

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

Usui

Katayama

Wang

et al. 2016

Polym J

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Irradiation of dye-doped liquid crystals (LCs) with linearly polarized light leads to molecular reorientation, which manifests functional properties for various nonlinear optical (NLO) applications. Material designs with lower light intensity thresholds for molecular reorientation have been explored, and nematic LCs have been one of the most attractive choices because of the high NLO properties. Here we present a different approach to reduce light intensity for reorientation by modifying a substrate surface that controls initial molecular orientation in polymer-stabilized nematic LCs doped with oligothiophene. The surface of the glass substrate was treated with various concentrations of a silane coupler. Water contact angle measurement and analysis of samples using polarized optical microscopy revealed that surface anchoring in the initial state decreased as the silane coupler concentration decreased. The threshold intensity was successfully reduced by 30% simply by optimizing the silane coupler concentration. This finding clearly indicates that weak surface anchoring is key to the reduction of light intensity for molecular reorientation. INTRODUCTIONLiquid crystal (LC) materials have had a great impact on our modern information society. 1-3 Various LC materials and devices including LC displays, 3 smart windows, 4 reconfigurable optical elements 5 and tunable optical metamaterials 6 have been realized. 2 In these applications, light modulation is the most important factor and is achieved by orientational changes of LC molecules using an external field.Molecular reorientation of conventional LCs has been performed by an electric field. However, molecular reorientation triggered by an optical field has attracted attention because it enables the development of all-optical devices. 7,8 Such photoinduced molecular reorientation includes photochemical and photophysical processes. Photochemical processes control LC orientation through a photochemical reaction, for example, photoisomerization, photocrosslinking or photodegradation. [8][9][10][11][12][13][14] In contrast, a photophysical process exploits the nonlinear optical (NLO) effects of an LC. 7,15 When a homeotropic LC is vertically irradiated with linearly polarized light, the interaction between the optical field and the LC molecules generates a torque to rotate the molecular director along the polarization direction, leading to homogeneous (in-plane) orientation. On the other hand, rotation of the molecular director is disturbed both by the interaction between LCs and the glass substrate surface, a process which is also called surface anchoring, and by bulk elasticity. These torques reach a balance that determines a specific light intensity that allows

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Laser-induced diffraction rings from a nematic-liquid-crystal film

Abstract: Multiple diffraction rings appear as a cw laser beam passes through a homeotropic nematic film. The phenomenon is shown to be the result of spatial self-phase modulation that is due to the laser-induced Freedericksz transition.

Cited by 453 publications

References 6 publications

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability

Emergence of electron coherence and two-color all-optical switching in MoS ₂ based on spatial self-phase modulation

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

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Laser-induced diffraction rings from a nematic-liquid-crystal film

Abstract: Multiple diffraction rings appear as a cw laser beam passes through a homeotropic nematic film. The phenomenon is shown to be the result of spatial self-phase modulation that is due to the laser-induced Freedericksz transition.

Cited by 453 publications

References 6 publications

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability

Few‐layer Bismuthene: Sonochemical Exfoliation, Nonlinear Optics and Applications for Ultrafast Photonics with Enhanced Stability

Emergence of electron coherence and two-color all-optical switching in MoS 2 based on spatial self-phase modulation

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

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Emergence of electron coherence and two-color all-optical switching in MoS ₂ based on spatial self-phase modulation