108 pubblicazioni classificate nel seguente modo:

A new twist in ferroelectric liquids
SCIENCE
Autore/i: Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: : Spontaneous chirality emerges in a highly polar liquid of achiral molecules.

Fluid jets and polar domains, on the relationship between electromechanical instability and topology in ferroelectric nematic liquid crystal droplets
SOFT MATTER
Autore/i: Marni, S.; Caimi, F.; Barboza, R.; Clark, N.; Bellini, T.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: Ferroelectric nematic liquid crystals are a class of recently discovered fluid materials formed by highly polar molecules that spontaneously align along a common direction, giving rise to a macroscopic polarization P. Since the polarization vector is locally collinear to the optical axis n, the study of the spatial patterns of n enables deducing the structure of P. We have carried on such topological study on ferroelectric nematic droplets confined between two solid ferroelectric substrates both when the droplet is in equilibrium and during a jet-emission phase that takes place when the solid surfaces become sufficiently charged. We find that in equilibrium the droplet splits in striped domains in which P has alternating directions. When these domains extend close to the droplets' perimeter, P adopts a pi-twisted structure to minimize accumulation of polarization charges. As the substrate surface charge is increased above threshold, fluid jets are emitted with a quasi-periodic pattern, a behaviour suggesting that their location is governed by an electrofluidic instability on the droplets' rim, in turn indicating the absence of specific trigger points. Soon after their emission, the jet periodicity is lost; some jets retract while other markedly grow. In this second regime, jets that grow are those that more easily connect to polar domains with P along the jet axis. Occasionally, ejection of isolated spikes also occurs, revealing locations where polarization charges have accumulated because of topological patterns extending on length scales smaller than the typical domain size.Ferroelectric nematic droplets confined between two ferroelectric substrates separated by a thin gap provide easy access to the topology and to its relationship with the electromechanical instability generated by substrates charging.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/332054

Electrowetting and Surface Tension of Chromonic Liquid Crystals
CRYSTALS
Autore/i: Marinello, Filippo; Ferraro, Davide; Meggiolaro, Alessio; Cremaschini, Sebastian; Zaltron, Annamaria; Pierno, Matteo; Mistura, Giampaolo; Zanchetta, Giuliano; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Abstract: In this work, we report on measurements of the contact angle of sessile droplets of aqueous solutions of a chromonic liquid crystal at different temperatures and concentrations and on different hydrophobic surfaces, and we show that the wettability of this complex fluid can be easily controlled by an external electric field. Specifically, electrically induced variations of the contact angle up to 70° were obtained using external DC voltages. Complementary tensiometric measurements of the aqueous solutions confirmed that the observed variations in the contact angle were mainly related to variations in the surface tension, while they did not show an evident connection with the internal molecular order of the liquid crystal droplets. Our study is relevant in view of the use of chromonic liquid crystals in microfluidic devices, where the control of wettability is an important tool for handling fluid flow.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326721

A new twist in ferroelectric liquids
SCIENCE
Autore/i: Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: Spontaneous chirality emerges in a highly polar liquid of achiral molecules.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/332055

Polarization Coupling between Ferroelectric Liquids and Ferroelectric Solids: Effects of the Fringing Field Profile
CRYSTALS
Autore/i: Marni, S.; Barboza, R.; Oluwajoba, A. S.; Zamboni, R.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: Recent experiments devoted to characterizing the behavior of sessile ferroelectric liquid droplets on ferroelectric solid substrates have shown the existence of a droplet electromechanical Rayleigh-like instability. The instability is induced by the bulk polarization of the ferroelectric fluid, which couples to the polarization of the underlying substrate through its fringing field and solid-fluid interface coupling. With the aim of characterizing this phenomenon, namely the coupling between the polarizations of a fluid and a solid material, we studied the behavior of ferroelectric liquid droplets confined between two solid substrates, arranged in different configurations, realized to generate fringing fields with different profiles. The results show that the features of the droplets instability are indeed affected by the specific fringing field shape in a way dominated by the minimization of the electrostatic energy associated with the bulk polarization of the ferroelectric fluid.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/332052

Fluid superscreening and polarization following in confined ferroelectric nematics
NATURE PHYSICS
Autore/i: Caimi, F.; Nava, G.; Fuschetto, S.; Lucchetti, L.; Paiè, P.; Osellame, R.; Chen, X.; Clark, N. A.; Glaser, M. A.; Bellini, T.
Classificazione: 1 Contributo su Rivista
Abstract: The recently discovered ferroelectric nematic (NF) liquid-crystal phase exhibits a spontaneous polarization field that is both orientationally fluid like a liquid crystal and large in magnitude like a solid ferroelectric. This combination imparts this phase with a unique electrostatic phenomenology and response to applied fields. Here we probe this phase by applying a small electric field to ferroelectric nematics confined in microchannels that connect electrodes through straight and curved paths and find that the NF phase smoothly orders with its polarization following the channels despite their winding paths. This implies a corresponding behaviour of the electric field. On inversion of the electric field, the polar order undergoes a multistage switching process dominated by electrostatic interactions. We also find multistage polarization switching dynamics in the numerical simulations of a quasi-two-dimensional continuum model of channel-confined NF liquid crystals, enabling the exploration of their internal structural and electrical self-organization. This indicates that polarization alignment and electric-field guiding are direct consequences of fluid superscreening—the prompt elimination of electric-field components normal to the channel walls by polarization reorientation. This response mimics the behaviour expected for ultrahigh-permittivity dielectrics, but with patterns of charge accumulation and local ordering unique to fluid ferroelectrics
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326477

Photoaligned Tunable Liquid Crystal Lenses with Parabolic Phase Profile
CRYSTALS
Autore/i: Bielykh, S. P.; Lucchetti, L.; Reshetnyak, V. Y.
Classificazione: 1 Contributo su Rivista
Abstract: We present a theoretical model of a cylindrical tunable liquid crystal lens based on the modulation of anchoring energy. The latter can be easily obtained using photoalignment techniques. The liquid crystal cell we propose exhibits strong anchoring at the top substrate and anchoring energy with a parabolic profile at the bottom substrate. The model describes the dependence of the focal length on the applied voltage and presents a theoretical study of the lens aberrations. The results obtained are of general relevance and can be used to optimize the performances of every type of liquid crystal lens with a parabolic profile.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326475

Optical control of mass ejection from ferroelectric liquid droplets: A possible tool for the actuation of complex fluids
JOURNAL OF MOLECULAR LIQUIDS
Autore/i: Marni, Stefano; Barboza, Raouf; Zaltron, Annamaria; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Abstract: We report on the optical control of the recently observed electromechanical instability of ferroelectric liquid droplets exposed to the photovoltaic field of a lithium niobate ferroelectric crystal substrate. The ferroelectric liquid is a nematic liquid crystal in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase, droplets irradiated by unfocused beam undergo an electromechanical instability and disintegrate by the explosive emission of fluid jets. We show here that the regions of jets emission can be controlled by focusing the light beam in areas close to the droplet's edge. Once emitted, the fluid jets can be walked by moving the beam up to millimeter distance from the mother droplet. Reverting the lithium niobate substrate, jets become thinner and show the tendency of being repelled by the beam instead of being attracted, thus offering an additional tool for their optical manipulation. These observations may pave the way to intriguing applications of ferroelectric nematic fluids related to manipulation, actuation, and control of soft, flexible materials.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/318712

On the Behavior of Ferroelectric Liquid Droplets in the Vicinity of a Ferroelectric Solid
CRYSTALS
Autore/i: Barboza, Raouf; Bahwi, Sameh; Marni, Stefano; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Abstract: We analyzed the behavior of sessile ferroelectric liquid droplets in the vicinity of a pyroelectrically charged ferroelectric crystal, an experimental configuration that allows testing the recently observed coupling between the polarizations of the fluid and solid materials, in conditions of no direct contact. Results demonstrate that polarizations’ coupling also exists in this configuration and has two distinct effects. Specifically, it gives rise both to an electromechanical instability of the liquid droplets consisting in the sudden ejection of interfacial fluid jets, and to a slow droplet motion toward the ferroelectric solid driven by a dielectrophoretic force. The two effects can possibly be separated, depending on the droplet size.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/315234

Walking Ferroelectric Liquid Droplets with Light
ADVANCED MATERIALS
Autore/i: Marni, Stefano; Nava, Giovanni; Barboza, Raouf; Bellini, Tommaso; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Abstract: The motion of ferroelectric liquid sessile droplets deposited on a ferroelectric lithium niobate substrate can be controlled by a light beam of moderate intensity irradiating the substrate at a distance of several droplet diameters from the droplet itself. The ferroelectric liquid is a nematic liquid crystal, in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase, droplets are either attracted toward the center of the beam or repelled, depending on the side of the lithium niobate exposed to light irradiation. Moreover, moving the beam results in walking the ferroelectric droplet over long distances on the substrate. This behavior is understood as due to the coupling between the polarization of the ferroelectric droplet and the polarization photoinduced in the irradiated region of the lithium niobate substrate. Indeed, the effect is not observed in the conventional nematic phase, suggesting the crucial role of the ferroelectric liquid crystal polarization.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/315233

Opto-microfluidic coupling between optical waveguides and tilted microchannels in lithium niobate
OPTICS EXPRESS
Autore/i: Zamboni, R.; Gauthier-Manuel, L.; Zaltron, A.; Lucchetti, L.; Chauvet, M.; Sada, C.
Classificazione: 1 Contributo su Rivista
Abstract: This work presents a reconfigurable opto-microfluidic coupling between optical waveguides and tilted microfluidic channels in monolithic lithium niobate crystal. The light path connecting two waveguide arrays located on opposite sides of a microfluidic channel depends on the refractive index between the liquid phase and the hosting crystal. As a result, the optical properties of the flowing fluid, which is pumped into the microfluidic channel on demand, can be exploited to control the light pathways inside the optofluidic device. Proof-of-concept applications are herein presented, including microfluidic optical waveguide switching, optical refractive index sensing, and wavelength demultiplexing.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326476

Optical control of light polarization in heliconical cholesteric liquid crystals
OPTICS LETTERS
Autore/i: Nava, G; Barboza, R; Simoni, F; Iadlovska, O; Lavrentovich, Od; Lucchetti, L
Classificazione: 1 Contributo su Rivista
Abstract: We show here that light polarization of a beam propagating through a heliconical cholesteric cell can be controlled by tuning the Bragg resonance of the structure. We demonstrate that this control is achieved by varying either the low-frequency electric field or the intensity of a pump beam impinging on the sample. The study confirms the recently reported phenomenon of optical tuning of the heliconical cholesterics and opens the door for the development of simple and efficient polarization modulators controlled electrically or optically.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/304220

Explosive electrostatic instability of ferroelectric liquid droplets on ferroelectric solid surfaces
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Autore/i: Barboza, R.; Marni, S.; Ciciulla, F.; Ali, MIR FAROOQ; Nava, G.; Caimi, F.; Zaltron, A.; Clark, N. A.; Bellini, T.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: We investigated the electrostatic behavior of ferroelectric liquid droplets exposed to the pyroelectric field of a lithium niobate ferroelectric crystal substrate. The ferroelectric liquid is a nematic liquid crystal, in which almost complete polar ordering of the molecular dipoles generates an internal macroscopic polarization locally collinear to the mean molecular long axis. Upon entering the ferroelectric phase by reducing the temperature from the nematic phase, the liquid crystal droplets become electromechanically unstable and disintegrate by the explosive emission of fluid jets. These jets are mostly interfacial, spreading out on the substrate surface, and exhibit fractal branching out into smaller streams to eventually disrupt, forming secondary droplets. We understand this behavior as a manifestation of the Rayleigh instability of electrically charged fluid droplets, expected when the electrostatic repulsion exceeds the surface tension of the fluid. In this case, the charges are due to the bulk polarization of the ferroelectric fluid, which couples to the pyroelectric polarization of the underlying lithium niobate substrate through its fringing field and solid-fluid interface coupling. Since the ejection of fluid does not neutralize the droplet surfaces, they can undergo multiple explosive events as the temperature decreases.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/305819

Surface alignment of ferroelectric nematic liquid crystals
SOFT MATTER
Autore/i: Caimi, F.; Nava, G.; Barboza, R.; Clark, N. A.; Korblova, E.; Walba, D. M.; Bellini, T.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: The success of nematic liquid crystals in displays and optical applications is due to the combination of their optical uniaxiality, fluidity, elasticity, responsiveness to electric fields and controllable coupling of the molecular orientation at the interface with solid surfaces. The discovery of a polar nematic phase opens new possibilities for liquid crystal-based applications, but also requires a new study of how this phase couples with surfaces. Here we explore the surface alignment of the ferroelectric nematic phase by testing different rubbed and unrubbed substrates that differ in coupling strength and anchoring orientation and find a variety of behaviors - in terms of nematic orientation, topological defects and electric field response - that are specific to the ferroelectric nematic phase and can be understood as a consequence of the polar symmetry breaking. In particular, we show that by using rubbed polymer surfaces it is easy to produce cells with a planar polar preferential alignment and that cell electrostatics (e.g.grounding the electrodes) has a remarkable effect on the overall homogeneity of the ferroelectric ordering.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/295727

Heliconical cholesteric liquid crystals as electrically tunable optical filters in notch and bandpass configurations
LIQUID CRYSTALS
Autore/i: Nava, G.; Ciciulla, F.; Simoni, F.; Iadlovska, O.; Lavrentovich, O. D.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: Heliconical cholesteric liquid crystals are a recently proposed novel class of liquid crystalline materials in which the chiral pitch can be tuned by an external electric field acting parallel to the helical axis. Here we show that these materials can be used as tunable optical filters of a simple architecture. The spectral properties of transmitted light can be tuned within the whole visible range. In particular, the bandpass wavelength can be shifted from 405 nm to 637 nm by changing the applied field from 2.7 to 1.7 V/µm. The electric field can also switch the filters on and off, within 1 s or less. Moreover, the filters work with both polarised and unpolarised light and can be switched from a notch to a bandpass configuration by changing the polarisation of incident light. An optical switch among three different laser lines is also reported as an additional possible application.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/295724

Optofluidic platform based on liquid crystals in x-cut lithium niobate: Thresholdless all-optical response
CRYSTALS
Autore/i: Ciciulla, F.; Zaltron, A.; Zamboni, R.; Sada, C.; Simoni, F.; Reshetnyak, V. Yu.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 10^7 W/m2 .
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/295726

Optical force-based detection of splay and twist viscoelasticity of CCN47 across the Nematic-to-Smectic A transition
JOURNAL OF MOLECULAR LIQUIDS
Autore/i: Lucchetti, L.; Nava, G.; Barboza, R.; Ciciulla, F.; Bellini, T.
Classificazione: 1 Contributo su Rivista
Abstract: We measured the splay and twist elastic constant K and viscosity η of CCN47 by coupling optical forces with the nematic director and detecting the resulting deformation. This approach enables to separately induce each of the two distortions and allows to characterize the viscoelastic properties of both the nematic and the smectic A phase. We find that in the nematic phase far from the transition the splay elastic constant K1 is larger than that of twist K2, while its viscosity is smaller, ηsplay < ηtwist. Upon lowering the temperature, K1 and ηsplay continuously increase in the nematic and smectic phase. On the contrary, K2 and ηtwist exhibit an abrupt growth when approaching the N/SmA transition, confirming the expected critical behavior. The twist viscoelastic ratio remains approximately constant in the whole nematic phase, indicating that the critical exponents for K2 and ηtwist are similar.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/295725

Formation of relocatable umbilical defects in a liquid crystal with positive dielectric anisotropy induced via photovoltaic fields
JOURNAL OF MOLECULAR LIQUIDS
Autore/i: Schafforz, S. L.; Nordendorf, G.; Nava, G.; Lucchetti, L.; Lorenz, A.
Classificazione: 1 Contributo su Rivista
Abstract: All optically generated, relocatable umbilic defects in a liquid crystal (LC) with positive dielectric anisotropy are reported. The studied samples are made with a Fe-doped LiNbO3 substrate showing the bulk photovoltaic effect and an ITO coated glass plate as covering substrate. Umbilics are created upon exposure with a focused laser beam: They are induced via photo generated fields at the relocatable exposure beam position. The field distribution of these fields is normal to the sample plane at the exposure spot center and has increasingly high in-plane field components in radial direction: Ideal conditions to induce director reorientations with radial symmetry in a LC with positive dielectric anisotropy. The irradiated regions are studied with polarized probe light revealing the characteristic for umbilic defects and the typical doughnut-shaped intensity distributions expected for optical vortex beams. The experimental findings are compared to calculated transmission profiles. Moreover, a LC with negative dielectric anisotropy was studied in the same type of sample for reference.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/278592

Elasticity and viscosity of DNA liquid crystals
ACS MACRO LETTERS
Autore/i: Lucchetti, Liana.; Fraccia, Tommaso P.; Nava, Giovanni; Turiv, Taras; Ciciulla, Fabrizio; Bethe, Lucas; Klussman, Sven; Lavrentovich, Oleg D.; Bellini, Tommaso
Classificazione: 1 Contributo su Rivista
Abstract: Concentrated solutions of blunt-ended DNA oligomer duplexes self-assemble in living polymers and order into lyotropic nematic liquid crystal phase. Using the optical torque provided by three distinct illumination geometries, we induce independent splay, twist, and bend deformations of the DNA nematic and measure the corresponding elastic coefficients K1, K2, and K3, and viscosities ηsplay, ηtwist, and ηbend. We find the viscoelasticity of the system to be remarkably soft, as the viscoelastic coefficients are smaller than in other lyotropic liquid crystals. We find K1 > K3 > K2, in agreement with the elasticity of the nematic phase of flexible polymers, and ηbend > ηsplay > ηtwist a behavior that is nonconventional in the context of chromonic, polymeric, and thermotropic liquid crystals, indicating a possible role of the weakness and reversibility of the DNA aggregates.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/283200

Physics of matter: from the nanoscale structure to the macroscopic properties of materials
The First outstanding 50 years of "Università Politecnica delle Marche"
Autore/i: Albertini, G.; Barucca, G.; Francescangeli, O.; Lucchetta, D. E.; Lucchetti, L.; Mengucci, P.; Rinaldi, D.; Simoni, F.; Vita, F.
Editore: Springer
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/275117

Optofluidic platform using liquid crystals in lithium niobate microchannel
OPEN ACCESS SCIENTIFIC REPORTS
Autore/i: Bonfadini, Silvio; Ciciulla, Fabrizio; Criante, Luigino; Zaltron, Annamaria; Simoni, Francesco; Reshetnyak, Victor; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Abstract: We demonstrate the all optical control of the molecular orientation of nematic liquid crystals confined in microfluidic channels engraved in lithium niobate. Microchannels are obtained by a novel approach based on femtosecond pulse laser micromachining carried on in controlled atmosphere. The combined effect of photovoltaic and pyroelectric fields generated by light in lithium niobate crystals on the liquid crystal orientation, is reported for the first time. The total space charge field and its dependence on the incident light intensity can be controlled by changing the direction of pump light propagation through the microfluidic chip. The results reported in this manuscript demonstrate that liquid crystals and lithium niobate can efficiently be combined in microfluidic configuration, in order to push forward a novel class of optofluidic devices.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/265527

Pitch tuning induced by optical torque in heliconical cholesteric liquid crystals
PHYSICAL REVIEW RESEARCH
Autore/i: Nava, G.; Ciciulla, F.; Iadlovska, O. S.; Lavrentovich, O. D.; Simoni, F.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Abstract: Heliconical cholesteric liquid crystals are expected to be more sensitive to torque induced by light field since their structure allows both bend and twist in molecular orientations, differently from the conventional cholesterics in which only twist deformation is involved, requiring much higher fields. We report here a demonstration of tuning the helical pitch in heliconical cholesterics induced by an optical torque. Experimental observations are in agreement with expectations of the classical theory extended to include the effect of the optical field. A dual control of the helical pitch is achieved including both the low-frequency electric field applied along the helix axis and the optical field orthogonal to it.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272997

Hybrid photosensitive structures based on nematic liquid crystals and lithium niobate substrates
OPTICAL DATA PROCESSING AND STORAGE
Autore/i: Lucchetti, Liana; Reshetnyak, Victor
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/265528

Laser-induced erasable patterns in a N* liquid crystal on an iron doped lithium niobate surface
OPTICS EXPRESS
Autore/i: Habibpourmoghadam, Atefeh; Lucchetti, Liana; Evans, Dean R.; Reshetnyak, Victor Y.; Omairat, Faissal; Schafforz, Samuel L.; Lorenz, Alexander
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255663

Colossal nonlinear optical response of liquid crystals
JOURNAL OF MOLECULAR LIQUIDS
Autore/i: Simoni, F.; Lucchetti, L.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255664

Non-linear optical measurement of the twist elastic constant in thermotropic and DNA lyotropic chiral nematics
SCIENTIFIC REPORTS
Autore/i: Lucchetti, Liana; Fraccia, Tommaso P.; Ciciulla, Fabrizio; Bellini, Tommaso
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255657

Confined photovoltaic fields in a photo-responsive liquid crystal test cell
Proceedings of SPIE - The International Society for Optical Engineering
Autore/i: Habibpourmoghadam, A.; Jiao, L.; Omairat, F.; Evans, D. R.; Lucchetti, L.; Reshetnyak, V.; Lorenz, A.
Editore: I.C. Khoo
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Exciting experimental results on the response properties of hybridized photo responsive liquid crystal test cells are reported, where iron doped lithium niobate substrates were used to photo generate electric fields and indium tin oxide coated cover glasses were used to confine these photo generated fields in a liquid crystal layer. Samples were investigated in a modified inverted optical polarizing microscope with white probe light (crossed polarizers) and exposed with a Gaussian laser beam focused to a small spot (14 μm FWHM). Test cells filled with nematic LC showed homeotropic director alignment. Upon exposure, this alignment was maintained at the exposure spot center and the LC director was selectively realigned in a surrounding single ring. This ring had a thickness of a few microns and its diameter increased with increasing exposure intensity (112 μm at 0.7 mW, 204 μm at 1.1 mW). This characteristic director realignment was traced back to the optically generated electric field distributions by simulations. In samples filled with chiral nematic LC, uniformly standing helix alignment was found. Textural transitions were induced at the focus position, which again led to the formation of well-defined circular defects. We could show that these defects can be permanently stored within the chiral nematic LC. Polarized optical microscopy of a rotated sample revealed that a point like defect with +1 topological charge was enclosed in each of these defects. Photovoltaic fields generated in small lithium niobate particles dispersed in a LC were found to cause promising optical responses and particle movement. © 2017 SPIE.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/266281

Giant optical nonlinearity in DNA lyotropic liquid crystals
OPTICS EXPRESS
Autore/i: Lucchetti, Liana; Fraccia, Tommaso P.; Ciciulla, Fabrizio; Simoni, Francesco; Bellini, Tommaso
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255662

Light-induced electric field generated by photovoltaic substrates investigated through liquid crystal reorientation
OPTICAL MATERIALS
Autore/i: Lucchetti, L.; Kushnir, K.; Reshetnyak, Viktor; Ciciulla, Fabrizio; Zaltron, A.; Sada, C.; Simoni, F.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/255660

Light-induced effects in liquid crystals: recent developments
Light-induced effects in liquid crystals: recent developments
Autore/i: Simoni, Francesco; Lucchetti, Liana
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/241371

Light controlled phase shifter for optofluidics
OPTICS LETTERS
Autore/i: Lucchetti, Liana; K., Kushnir; A., Zaltron; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/230129

Liquid crystal cells based on photovoltaic substrates
JOURNAL OF THE EUROPEAN OPTICAL SOCIETY. RAPID PUBLICATIONS
Autore/i: Lucchetti, Liana; Kushnir, K.; Zaltron, A.; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/241357

All-optical phase shifter with photovoltaic liquid crystal cell
All-optical phase shifter with photovoltaic liquid crystal cell
Autore/i: Lucchetti, Liana; K., Kushnir; F., Ciciulla; A., Zaltron; G., Bettella; G., Pozza; C., Sada; V., Reshetnyak; Simoni, Francesco
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/241369

Optical nonlinearity in the nematic phase of bent-core mesogens
OPTICS LETTERS
Autore/i: Lucchetti, Liana; Vita, Francesco; Scharrer, E.; Francescangeli, Oriano; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: Nonlinear optical response of the cybotactic nematic phase of a bent-core mesogen has been investigated for the first time through self-phase modulation induced by a Gaussian beam. The material exhibits a high nonlinear response achieving a nonlinear index n2 ≈ 5 × 10−5 cm2∕W and an unconventional behavior characterized by two different regimes. While the high-intensity regime can be easily explained in terms of a thermal indexing effect, the low-intensity regime is metastable and characterized by an unusual dependence on the irradiation energy. It is suggested that a change of the director configuration, possibly due to a light-induced modification of surface anchoring, is responsible for the observed behavior.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/228982

Light-induced adsorption and desorption in Methyl-Red doped liquid crystals: a review.
LIQUID CRYSTALS REVIEWS
Autore/i: Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/229047

Electrical tuning of optoelastic interaction in nematic colloids
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Simoni, Francesco; F., Bracalente; E., Brasselet; L., Criante; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/221715

Role of space charges on light-induced effects in nematic liquid crystals doped by methyl red
PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS
Autore/i: Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/156305

Light-controlled electric Freedericksz threshold in dye doped liquid crystals
JOURNAL OF APPLIED PHYSICS
Autore/i: Lucchetti, Liana; L., Catani; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/170705

Enhanced optoelastic interaction range in liquid crystals with negative dielectric anisotropy
APPLIED PHYSICS LETTERS
Autore/i: Simoni, Francesco; S., Lalli; Lucchetti, Liana; L., Criante; E., Brasselet
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/221714

Light-induced effects in dye-doped liquid crystals: role of space charges
Proceedings SPIE
Autore/i: Simoni, Francesco; Lucchetti, Liana
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/221716

First-order optical Freedericksz transition in a dye-doped nematic liquid crystal
OPTICS LETTERS
Autore/i: Simoni, Francesco; 1, ; Lucchetta, Daniele Eugenio; Lucchetti, Liana; H. L., Ong; S. V., Serak; N., Tabiryan
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/106662

Electrically tunable optoelastic interaction range of nematic colloids
SOFT MATTER
Autore/i: Criante, Luigino; F., Bracalenta; Lucchetti, Liana; Simoni, Francesco; E., Brasselet
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/106663

Tunable MicrolensesOptically recorded in dye-doped liquid crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; J., Tasseva
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/106462

Optically recorded tunable microlenses based on dye-doped liquid crystal cells
APPLIED PHYSICS LETTERS
Autore/i: Lucchetti, Liana; J., Tasseva
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/76410

Optical Manipulation in Liquid Crystals: Effects of Tight Focusing on Nonlinear Optical Reorientation
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Simoni, Francesco; Aieta, Francesco; Bracalente, Francesco; L., Criante; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/76397

Effect of nonlinear optical reorientation on optical trapping in nematic liquid crystals
NONLINEAR OPTICS, QUANTUM OPTICS
Autore/i: Lucchetti, Liana; Criante, Luigino; Bracalente, Francesco; F., Aieta; F., Simoni
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/76391

Optical trapping induced by reorientational nonlocal effects in nematic liquid crystals
PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS
Autore/i: Lucchetti, Liana; Criante, Luigino; Bracalente, Francesco; Aieta, Francesco; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63149

Optical trapping in liquid crystals
Proceedings of SPIE
Autore/i: Simoni, Francesco; Lucchetti, Liana; Criante, Luigino; Bracalente, Francesco; Aieta, Francesco
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/57638

Optical trapping induced by nonlinear reorientation of liquid crystals
Newsroom
Autore/i: Simoni, Francesco; Lucchetti, Liana; Luigino, Criante; Francesco, Bracalente; Francesco, Aieta
Editore: SPIE
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/69842

Fine structure in spatial self-phase modulation patterns: at a glance determination of the sign of optical nonlinearity in highly nonlinear films
JOURNAL OF OPTICS. A, PURE AND APPLIED OPTICS
Autore/i: Lucchetti, Liana; Suchand, S.; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50231

Director sliding induced by a circularly polarised light in dye-doped liquid crystals
OPTICS COMMUNICATIONS
Autore/i: Lucchetti, Liana; Tifi, L.; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50144

All-optical steering of soliton waveguides in dye-doped liquid crystals
APPLIED PHYSICS LETTERS
Autore/i: Piccardi, A; Assanto, G; Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: Soliton induced waveguides can be all-optically readdressed in planar cells by modifying the molecular anchoring with an external light source. Using an elliptically shaped control beam we demonstrate refraction and total internal reflection of spatial solitons in dye-doped nematic liquid crystals.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50471

Surface-induced nonlinearities of liquid crystals driven by an electric field
PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS
Autore/i: Lucchetti, Liana; M., Gentili; Simoni, Francesco; S., Pavliuchenko; S., Subota; V., Reshetnyak
Classificazione: 1 Contributo su Rivista
Abstract: We report the study of the effect of a static electric field on the huge optical nonlinearity of methyl-red doped nematic liquid crystals. Experimental data are well fitted using a theoretical model that takes into account the modulation of the surface charge density due to the impinging light beam. It is demonstrated that the optical nonlinearity can be varied by orders of magnitude with application of a low voltage below the threshold of the Fredericks transition. These results confirm the previously proposed model of surface induced nonlinear effects.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51913

The never ending story of the amazing nonlinearities of liquid crystals: recent advances in studying electric field control
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; Gentili, M.; Tifi, L.; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50143

Photorefractive effects in liquid crystals
Photorefractive Materials and Their Applications 2
Autore/i: Simoni, Francesco; Lucchetti, Liana
Editore: Springer Science
Luogo di pubblicazione: NEW YORK
Classificazione: 2 Contributo in Volume
Abstract: invited contribution
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50666

Phenomenological model for the optically induced easy direction
PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS
Autore/i: ALEXE IONESCU, A. L.; Uncheselu, C; Lucchetti, Liana; Barbero, G.
Editore: pubblicata da: AMERICAN PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, USA, MD, 20740-3844
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/33852

Effects leading to colossal optical nonlinearity in dye-doped liquid crystals
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
Autore/i: Lucchetti, Liana; Gentili, M; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50898

Colossal optical nonlinearity induced by a low frequency external electric field in dye-doped liquid crystals
OPTICS EXPRESS
Autore/i: Lucchetti, Liana; M., Gentili; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: We report on the effects of a low-frequency electric field on the optical nonlinear response of thin dye-doped liquid crystal cells. Experimental data show that the external field allows reaching extremely high values of the optical nonlinearity without any critical control of the cell interfaces. A qualitative interpretation of the collected data, based on the light-induced modulation of the bulk voltage through surface modifications, is proposed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51692

Pretransitional enhancement of the optical nonlinearity of thin dye-doped liquid crystals in the nematic phase
APPLIED PHYSICS LETTERS
Autore/i: Lucchetti, Liana; Gentili, M; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: We report a critical enhancement of the nonlinear optical response of dye-doped liquid crystals obtained by approaching the clearing point in the nematic phase. The enhancement of the nonlinear diffraction efficiency has been measured in the range 0.2–0.3 deg below the nematic-isotropic transition temperature. It allows reaching a nonlinear refractive index higher than 40 cm2 /W in all the tested cells.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51143

Optical phase conjugation and wavefront correction by thin nematic liquid crystal cells
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; M., Gentili; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/72426

Light-induced molecular adsorption and reorientation at polyvinylcinnamate-fluorinated/liquid-crystal interface
PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS
Autore/i: Francescangeli, Oriano; Lucchetti, Liana; Simoni, Francesco; V., Stanic; A., Mazzulla
Classificazione: 1 Contributo su Rivista
Abstract: We have carried out a detailed experimental study, by means of x-ray reflectometry (XRR) and half-leaky guided mode (HLGM) optical characterization, of the light-induced molecular adsorption and reorientation at the polyvinylcinnamate-fluorinated (PVCN-F)/liquid-crystal (LC) interface of a LC cell doped with the azodye methyl red (MR). The XRR data allowed characterizing the microscopic structure of the adsorbed dye layer both before irradiation (dark adsorption) and after irradiation (light-induced adsorption). The HLGM optical characterization has made possible the experimental determination of the nematic director profile in the LC cell and evaluation of the effects of light-induced adsorption on the LC anchoring conditions. The experimental findings have confirmed the formation of a dark-adsorbed layer and are in agreement with the absorption model previously proposed to account for the complex phenomenology related to light-induced anchoring and reorientation in dye-doped liquid crystals.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52957

Dynamic of Surface-Mediated Director Reorientation in a Cell with Dye Doped Liquid Crystal
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: D., Fedorenko; E., Ouskova; Y., Reznikov; V., Reshetnyak; Lucchetti, Liana; Simoni, Francesco
Editore: TAYLOR & FRANCIS LTD, 4 PARK SQUARE, MILTON PARK, ABINGDON, ENGLAND, OXON, OX14 4RN
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/27416

X-ray microdiffraction study of the liquid crystal ordering in confined geometries
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Francescangeli, Oriano; V., Stanic; Lucchetti, Liana; C., Ferrero; M., Burghammer
Classificazione: 1 Contributo su Rivista
Abstract: We report, the results of recent experiments where for the first time X-ray micro-diffraction has been used to probe Liquid crystal ordering and nematic director-field configuration in single micron-sized droplets of polymer-dispersed liquid crystals. The pattern of the bipolar configuration has been detected in a droplet with radius R ≤ 1 μm and the main quantities characterizing the orientational and short-range positional order of the confined nematic have been determined. We report a detailed description of the procedure followed to determine the distribution function of the nematic director in the droplet and the droplet order parameter from the azimuthal intensity profile of the diffraction pattern.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51881

Dynamics of surface-mediated director reorientation in a cell with dye-doped liquid crystal
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: D., Fedorenko; E., Ouskova; Reznikov, Y. u.; V., Reshetnyak; Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/76370

Colossal optical nonlinearity in dye-doped liquid crystals
OPTICS COMMUNICATIONS
Autore/i: Lucchetti, Liana; M., DI FABRIZIO; Francescangeli, Oriano; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: We report the experimental evidence of a nonlinear optical response among the highest ever observed. A nonlinear refractive index on the order of 103 cm2/W (that is 108 times higher than in Giant Optical Nonlinearity) has been obtained in randomly oriented thin liquid crystal cells. This result shows the fundamental role played by the surface in the nonlinear optical response of dye-doped liquid crystals.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51410

Optical phase conjugation and efficient wave front correction of weak light beams by dye-doped liquid crystals
APPLIED PHYSICS LETTERS
Autore/i: Lucchetti, Liana; M., DI FABRIZIO; M., Gentili; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: Articolo recensito su Laser Focus World
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52974

“Liquid-crystal ordering in confined geometries probed by X-ray microdiffraction"
Congresso Nazionale di Fisica della Materia
Autore/i: Francescangeli, Oriano; C., Ferrero; V., Stanic; Pisani, Michela; Lucchetti, Liana; M., Burghammer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/83347

Comment on “Surfactant enhanced reorientation in dye-doped nematic liquid crystals”
EUROPHYSICS LETTERS
Autore/i: Lucchetti, Liana
Editore: EDP Sciences:17 Ave Du Hoggar, BP112, 91944 Les Ulis Cedex A France:011 33 1 69187575, EMAIL: subscribers@edpsciences.com, INTERNET: http://www.edpsciences.com, Fax: 011 33 1 69860678
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/34658

Polarization holographic techniques: a method to produce diffractive devices in polymer dispersed liquid crystals
LIQUID CRYSTALS
Autore/i: A., Mazzulla; A., Dastoli; G., Russo; Lucchetti, Liana
Editore: Taylor & Francis Limited:Rankine Road, Basingstoke RG24 8PR United Kingdom:011 44 1256 813035, EMAIL: madeline.sims@tandf.co.uk, info@tandf.co.uk, INTERNET: http://www.tandf.co.uk, Fax: 011 44 1256 330245
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/34657

Surface reorientation induced by short light pulses in doped liquid crystals
OPTICS LETTERS
Autore/i: Lucchetti, Liana; D., Fedorenko; Francescangeli, Oriano; Y., Reznikov; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: Fast surface reorientation induced by a single 4-ns low-energy laser pulse in dye-doped liquid crystals is reported. The reorientation is due to light-induced modification of the surface anisotropy, which affects the liquid crystal's director through the appearance of a preferred direction on the irradiated surface. The detected signals can be interpreted as being the result of light-induced desorption and adsorption of dye molecules.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51487

Optical storage of hidden images in ultraviolet-cured polymer dispersed liquid crystals
LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53404

Enhanced Nolinear Optical Response of Liquid Crystals
NONLINEAR OPTICS for the INFORMATION SOCIETY
Autore/i: Simoni, Francesco; Francescangeli, Oriano; Lucchetta, Daniele Eugenio; Lucchetti, Liana
Editore: Kluwer Academic Pub
Luogo di pubblicazione: Dordrecht
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/72427

Liquid crystal ordering by freezing of thermal convective motion in Polymer Dispersed Liquid Crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetta, Daniele Eugenio; Francescangeli, Oriano; Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: This paper reports on the first observation of thermal convective motion in high-intensity photocured PDLC mixtures and demonstrates the possibility of LC ordering through the freezing of this thermal convective motion. The dependence of laser-cured PDLC films morphology on curing parameters such as light intensity, curing time, and sample temperature have also been studied. It is shown that the transition between ordered columnar and disordered turbulent motion is possible by increasing the laser beam intensity and that the flow patterns associated with both these regimes can be frozen by the photopolymerization process.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50761

Ordering and director field configuration in single droplets of liquid crystals probed by X-ray microdiffraction
EUROPHYSICS LETTERS
Autore/i: Francescangeli, Oriano; C., Ferrero; Lucchetti, Liana; Simoni, Francesco; M., Burghammer
Classificazione: 1 Contributo su Rivista
Abstract: X-ray microdiffraction (μ-XRD) is used for the first time to probe the liquid crystal (LC) ordering in confined LCs. We report on the direct observation of the director field in single droplets of nematic LCs embedded in a solid polymeric matrix (polymer-dispersed LCs). The bipolar configuration is identified in droplets with radius R ≤ 1 μm. Both the director distribution function and the droplet order parameter are obtained from diffraction patterns and the results are in excellent agreement with theoretical calculations. This technique is unique in its application to dispersed mesophases in that it allows to probe the local (μm length scale) LC ordering. The possibility of focusing measurements on single droplets eliminates the problems connected with averaging, which are typical of other techniques. Our results prove that μ-XRD is a novel and valuable tool in the study of confined LCs and open new exciting opportunities for future investigations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52995

Light-induced anchoring and reorientation effects in dye-doped liquid crystals
Liquid Crystals VI
Autore/i: Francescangeli, Oriano; Lucchetti, Liana; Simoni, Francesco; S., Slussarenko; E., Ouskova; Y., Reznikov; S., Shiyanovskii; J. L., West
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: A review of the recent results of our group in the field of light-induced anchoring and reorientation effects in dye-doped liquid crystals (LCs) is presented. In particular, the phenomena of photoinduced anchoring and permanent reorientation over a polymeric boundary surface of a dye-doped LC cell is reported, both in the isotropic phase and in the orientationally ordered nematic phase. The results have been interpreted microscopically in terms of adsorption and desorption of the dichroic azo-dye (methyl-red) molecules onto the illuminated surface during light irradiation. The model proposed is in agreement with recent results on the dynamic and stable grating formation in methyl-red doped LCs.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52513

Light-induced adsorption and desorption in dynamic and stable grating formation in methyl-red doped liquid crystals
JOURNAL OF NONLINEAR OPTICAL PHYSICS AND MATERIALS
Autore/i: Lucchetti, Liana; M., DI FABRIZIO; Francescangeli, Oriano; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: A detailed study of the light-induced gratings in Methyl-Red-doped 4-n-pentyl-4'-cyanobiphenyl (5CB) homeotropically aligned is reported. In particular, the dependence of diffraction efficiency upon the pump and probe polarizations has been investigated both for transient and permanent gratings. Our results confirm the earlier observations on the role of light-induced adsorption of MR molecules on the cell boundaries and demonstrate the common origin of the supranonlinear response and the permanent recording effect.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/27409

Liquid Crystal Ordering by Freezing of Thermal Convection Motion in Polymer Dispersed Liquid Crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetta, Daniele Eugenio; Francescangeli, Oriano; Lucchetti, Liana; Simoni, Francesco
Editore: Gordon & Breach Science Publishers:PO Box 90, Reading RG1 8JL United Kingdom:011 44 118 9520303, 011 44 118 9560080, 011 44 181 9560080, EMAIL: philip.bott@gbmis.gbhap.com, INTERNET: http://www.gbhap.com/pubdate, Fax: 011 44 118 9568211
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/27413

SINE: surface induced nonlinear effects
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; Lucchetta, Daniele Eugenio; Francescangeli, Oriano; Simoni, Francesco
Editore: Gordon & Breach Science Publishers:PO Box 90, Reading RG1 8JL United Kingdom:011 44 118 9520303, 011 44 118 9560080, 011 44 181 9560080, EMAIL: philip.bott@gbmis.gbhap.com, INTERNET: http://www.gbhap.com/pubdate, Fax: 011 44 118 9568211
Classificazione: 1 Contributo su Rivista
Abstract: Pump-probe and TIR experiments have been performed on the dye-doped nematic liquid crystal 5CB, in order to study the basic mechanisms of the extraordinarily large nonlinear response recently reported. Experimental data show that light-induced modifications of the anchoring conditions can be the origin of the observed effect. The bulk reorientation due to the collective elastic behaviour of the liquid crystal gives then rise to the nonlinearity, which occurs without a direct optical torque on the molecular director in the bulk. We have called this effect SINE (Surface Induced Nonlinear Effect).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50997

High intensity UV laser curing of Polymer Dispersed Liquid Crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetta, Daniele Eugenio; Lucchetti, Liana; L., Gobbi; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/72440

Director reorientation induced by short pulsed irradiation in dye doped liquid crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; Simoni, Francesco; Y., Reznikov
Editore: Taylor & Francis Limited:Rankine Road, Basingstoke RG24 8PR United Kingdom:011 44 1256 813035, EMAIL: madeline.sims@tandf.co.uk, info@tandf.co.uk, INTERNET: http://www.tandf.co.uk, Fax: 011 44 1256 330245
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/34360

Optical Nonlinearities of Liquid Crystals Controlled by Surfaces
Spatial Light Modulators: Technology and Applications
Autore/i: Lucchetti, Liana; Lucchetta, Daniele Eugenio; Francescangeli, Oriano; Simoni, Francesco
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: We show that light-induced modification of the anchoring conditions can lead to an extraordinarily large optical response in dye-doped nematic liquid crystals. The bulk reorientation due to the collective elastic behavior of the liquid crystal is the origin of the nonlinearity, which occurs without a direct optical torque on the molecular director in the bulk. We call this effect SINE (Surface Induced Nonlinear Effect). These results can also explain the origin of the supranonlinear behavior recently observed in the same composites.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53287

Morphological and electro-optical properties of polymer dispersed liquid crystals cured by high intensity laser radiation
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetta, Daniele Eugenio; Francescangeli, Oriano; Lucchetti, Liana; L., Gobbi; Simoni, Francesco
Editore: Gordon & Breach Science Publishers:PO Box 90, Reading RG1 8JL United Kingdom:011 44 118 9520303, 011 44 118 9560080, 011 44 181 9560080, EMAIL: philip.bott@gbmis.gbhap.com, INTERNET: http://www.gbhap.com/pubdate, Fax: 011 44 118 9568211
Classificazione: 1 Contributo su Rivista
Abstract: We have studied the morphology and the electrooptical properties of Polymer Dispersed Liquid Crystals prepared by the Polymer Induced Phase Separation technique under high-intensity UV laser curing. Photoinduced thermal convective motions have been observed in the directly illuminated area, which originates unusual morphological patterns consisting of ordered and/or disordered structures, depending on the curing intensity. We show that transition between ordered (columnar) and disordered (turbulent) motion is possible by increasing the laser beam intensity and the flow patterns associated to both these regimes can be frozen in by the photo-polymerization process. We show also that localized high-intensity curing generates a gradient of the droplet-size distribution outside the directly irradiated area essentially due to the non-uniform spatial-distribution of scattered intensity. This complex morphology reflects into a peculiar electrooptical behavior that could find potential application in new optical devices.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/27138

Liquid crystalline materials for spatial light modulation
Proceedings of SPIE
Autore/i: Lucchetti, Liana; Lucchetta, Daniele Eugenio; R., Karapinar; A. MANNI AND F., Simoni
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/45967

Droplet-size distribution gradient induced by laser curing in polymer dispersed liquid crystals
LIQUID CRYSTALS
Autore/i: Lucchetta, Daniele Eugenio; Francescangeli, Oriano; Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Abstract: We have studied the morphology and electro-optical properties of polymer dispersed liquid crystals prepared by polymerization-induced phase separation (PIPS) under high intensity UV laser curing. The results have shown that localized high intensity curing generates a gradient of the droplet size distribution outside the directly irradiated area as a consequence of the non-uniform spatial distribution of the scattered intensity. Such a distribution of the droplet size reflects in a peculiar electro-optical behaviour that could find potential application in optical devices. Both shape and spatial extent of the droplet size gradient are affected by the spatial velocity of polymerization which in turn strongly depends on the intensity of the curing laser beam. This dependence has also been experimentally investigated.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50976

Analysis of the phase separation process in UV cured Polymer Dispersed Liquid Crystals for optical applications
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Lucchetti, Liana; L., Gobbi; Simoni, Francesco
Editore: Taylor & Francis Limited:Rankine Road, Basingstoke RG24 8PR United Kingdom:011 44 1256 813035, EMAIL: madeline.sims@tandf.co.uk, info@tandf.co.uk, INTERNET: http://www.tandf.co.uk, Fax: 011 44 1256 330245
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/34164

On the origin of the huge nonlinear response of dye-doped liquid crystal
OPTICS EXPRESS
Autore/i: Simoni, Francesco; Lucchetti, Liana; Lucchetta, Daniele Eugenio; Francescangeli, Oriano
Classificazione: 1 Contributo su Rivista
Abstract: We report the results of an investigation carried on Methyl Red-doped nematic liquid crystals with the aim of studying the basic mechanism of the extraordinarily large nonlinear response recently reported. We show that the experimental data can be explained as due to light-induced modifications of the anchoring conditions leading to director reorientation on the irradiated surface, which in turn gives rise to a bulk reorientation through the cell. We have called this phenomenon SINE (Surface Induced Nonlinear Effect) to remind that it occurs "without" (= sine in latin language) a direct optical or electric torque on the director in the bulk.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51304

Nano-size liquid crystal domains in polymer matrix
Atti del V Multinational Congress on Electron Microscopy
Autore/i: L., Gobbi; A., Manni; R., Karapinar; Lucchetta, Daniele Eugenio; Lucchetti, Liana; Simoni, Francesco
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/45968

Enhanced Nonlinear Optical Response of Liquid Crystals
Nonlinear Optics for the Information Society
Autore/i: Simoni, Francesco; Francescangeli, Oriano; Lucchetta, Daniele Eugenio; Lucchetti, Liana
Editore: Kluwer Academic Publishers
Luogo di pubblicazione: DORDRECHT
Classificazione: 2 Contributo in Volume
Abstract: Invited Article
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50423

Coarsening and phase separation in ultraviolet cured polymer dispersed liquid crystals
JOURNAL OF APPLIED PHYSICS
Autore/i: Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51225

Scrittura di immagini permanenti in Polymer Dispersed Liquid Crystals (PDLC)
Autore/i: DI BELLA, S; Lucchetti, Liana; Marzocchini, R; Simoni, Francesco
Classificazione: 6 Brevetti
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53645

Enhancement of the optical nonlinearity in liquid crystals throughout the photovoltaic effect
IQEC, International Quantum Electronics Conference Proceedings
Autore/i: Francescangeli, Oriano; Lucchetti, Liana; Simoni, Francesco; S., Slussarenko
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The transient behavior of the photovoltaic effect detected in the same kind of cell using c.w. and pulsed light excitation was examined. The study was performed on sandwich-like cells consisting of two parallel plane indium tin oxide-coated glass substrates, filled with mixture of the nematic 5CB liquid crystal and a small amount of methyl red. Results demonstrated a change of polarity of the photoinduced electromotive force while reaching the steady-state value under c.w. irradiation; and the generation of a transient photovoltage induced by a single 4 ns laser pulse with moderate energy density.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53047

Soft materials for optical storage
LA RIVISTA DEL NUOVO CIMENTO DELLA SOCIETÀ ITALIANA DI FISICA
Autore/i: Lucchetti, Liana; Simoni, Francesco
Editore: Editrice Compositori
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/33863

Phase separation and image recording in UV laser cured pdlc
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: S., DI BELLA; Lucchetti, Liana; Simoni, Francesco
Editore: Taylor & Francis Limited:Rankine Road, Basingstoke RG24 8PR United Kingdom:011 44 1256 813035, EMAIL: madeline.sims@tandf.co.uk, info@tandf.co.uk, INTERNET: http://www.tandf.co.uk, Fax: 011 44 1256 330245
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/33862

Fast optical recording in dye-doped liquid crystals
OPTICS LETTERS
Autore/i: Lucchetti, Liana; Simoni, Francesco; Reznikov, Y. u.
Editore: Optical Society of America:2010 Massachusetts Avenue Northwest:Washington, DC 20036:(800)762-6960, (202)223-8130, EMAIL: custserv@osa.org, INTERNET: http://www.osa.org, Fax: (202)223-1096
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/33861

Dye-doped Photorefractive Liquid Crystals for Dynamic and Storage Holographic Grating Formation and Spatial Light Modulation
PROCEEDINGS OF THE IEEE
Autore/i: I. C., Khoo; M. Y., Shih; M. V., Wood; B. D., Guenther; P. H., Chen; Simoni, Francesco; S. S., Slussarenko; Francescangeli, Oriano; Lucchetti, Liana
Editore: IEEE / Institute of Electrical and Electronics Engineers Incorporated:445 Hoes Lane:Piscataway, NJ 08854:(800)701-4333, (732)981-0060, EMAIL: subscription-service@ieee.org, INTERNET: http://www.ieee.org, Fax: (732)981-9667
Classificazione: 1 Contributo su Rivista
Abstract: The basic mechanisms of photo-induced space charge field formation, director axis re-orientation, and refractive index changes in fullerene C60- and dye-doped nematic liquid crystals films are presented. In particular, in aligned methyl-red-doped nematic liquid crystal film, we observe a nonlinear index change coefficient as high as 10 cm2/W, associated with purely optically induced liquid crystal director axis re-orientation. Experimental observations of dynamic and high-resolution storage holographic grating formation, two beam coupling with gain of nearly 3000 cm-1, optical limiting action at nanowatt cw laser power, and incoherent-coherent image conversion at μW/cm2 light intensity level are discussed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/29528

Dye-doped photorefractive liquid crystals for dynamic and storage holographic grating formation and spatial light modulation
PROCEEDINGS OF THE IEEE
Autore/i: I. C., Khoo; M., Shih; M. V., Wood; B. D., Guenther; P. H., Chen; Simoni, Francesco; S., Slussarenko; Francescangeli, Oriano; Lucchetti, Liana
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/45966

Polymer Dispersed Liquid Crystals as Optical Storage Materials
Liquid Crystals Materials and Devices
Autore/i: Simoni, Francesco; S., Di Bella; Lucchetti, Liana; G., Cipparrone; A., Mazzulla
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/72445

Droplets Formation in UV Cured Polymer Dispersed Liquid Crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: S., Di Bella; Lucchetti, Liana; Simoni, Francesco
Editore: Taylor & Francis Limited:Rankine Road, Basingstoke RG24 8PR United Kingdom:011 44 1256 813035, EMAIL: madeline.sims@tandf.co.uk, info@tandf.co.uk, INTERNET: http://www.tandf.co.uk, Fax: 011 44 1256 330245
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/72419

Optical Storage Effect in Polymer Dispersed Liquid Crystals
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY. SECTION A, MOLECULAR CRYSTALS AND LIQUID CRYSTALS
Autore/i: Cipparrone, G.; Mazzulla, A.; Nicoletta, F. P.; Lucchetti, L.; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/72418

Holographic grating formation in dye doped polymer dispersed liquid crystals
OPTICS COMMUNICATIONS
Autore/i: Cipparrone, G.; Mazzulla, A.; Nicoletta, F. P.; Lucchetti, Liana; Simoni, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51534