Publications

2017
D. Pierangeli, et al., “Observation of an intrinsic nonlinearity in the electro-optic response of freezing relaxors ferroelectrics,” vol. 4, no. 8. pp. 1487 - 1493, 2017. Publisher's VersionAbstract

We demonstrate an electro-optic response that is linear in the amplitude but independent of the sign of the applied electric field. The symmetry-preserving linear electro-optic effect emerges at low applied electric fields in freezing nanodisordered KNTN above the dielectric peak temperature, deep into the nominal paraelectric phase. Strong temperature dependence allows us to attribute the phenomenon to an anomalously reduced thermal agitation in the reorientational response of the underlying polar-nanoregions. (C) 2014 Optical Society of America

2 ) Martínez-Lorente, R. ( 1, et al., “Scalable Electro-Optic Control of Localized Bistable Switching in Broad-Area VCSELs Using Reconfigurable Funnel Waveguides,” Physical Review Applied, vol. 7, no. 6, 2017. Publisher's Version
J. Parravicini, E. DelRe, A. J. Agranat, and G. Parravicini, “Liquid–solid directional composites and anisotropic dipolar phases of polar nanoregions in disordered perovskites.,” Nanoscale, vol. 9, no. 27, pp. 9572, 2017. Publisher's Version
G. Di Domenico, E. DelRe, G. Antonacci, S. Silvestri, J. Parravicini, and A. J. Agranat, “Miniaturized photogenerated electro-optic axicon lens Gaussian-to-Bessel beam conversion,” Applied Optics, vol. 56, no. 10, pp. 2908-2911, 2017. Publisher's Version
S. Belkin, et al., “Remote detection of buried landmines using a bacterial sensor.,” Nature BiotechnologyNat Biotechnol, vol. 35, no. 4, pp. 308 - 310, 2017. Publisher's Version
2016
D. Pierangeli, et al., “Enhancing optical extreme events through input wave disorder.,” Physical Review A: Atomic, Molecular & Optical Physics, vol. 94, no. 6, pp. 1 - 1, 2016. Publisher's VersionAbstract

We demonstrate how the emergence of extreme events strongly depends on the correlation length of the input field distribution. Observing the behavior of optical waves in turbulent photorefractive propagation with partially incoherent excitations, we find that rogue waves are strongly enhanced for a characteristic input correlation scale. Waveform analysis identifies this scale with a characteristic peak-intensity-independent wave size, suggesting a general role played by saturation in the nonlinear response in rogue phenomena. [ABSTRACT FROM AUTHOR]Copyright of Physical Review A: Atomic, Molecular & Optical Physics is the property of American Physical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

D. Pierangeli, F. Di Mei, G. Di Domenico, A. J. Agranat, C. Conti, and E. DelRe, “Turbulent Transitions in Optical Wave Propagation.,” Physical Review Letters, vol. 117, no. 18, pp. 183902 - 183902, 2016. Publisher's VersionAbstract

We report the direct observation of the onset of turbulence in propagating one-dimensional optical waves. The transition occurs as the disordered hosting material passes from being linear to one with extreme nonlinearity. As the response grows, increased wave interaction causes a modulational unstable quasihomogeneous flow to be superseded by a chaotic and spatially incoherent one. Statistical analysis of high-resolution wave behavior in the turbulent regime unveils the emergence of concomitant rogue waves. The transition, observed in a photorefractive ferroelectric crystal, introduces a new and rich experimental setting for the study of optical wave turbulence and information transport in conditions dominated by large fluctuations and extreme nonlinearity.;

J. Parravicini, E. DelRe, A. J. Agranat, and G. Parravicini, “Macroscopic response and directional disorder dynamics in chemically substituted ferroelectrics.,” Physical Review B: Condensed Matter & Materials Physics, vol. 93, no. 9, pp. 1 - 1, 2016. Publisher's VersionAbstract
Using temperature-resolved dielectric spectroscopy in the range 25-320 K we investigate the macroscopic response, phase symmetry, and order/disorder states in bulk ferroelectric K1-yLiyTa1-xNbx (KLTN). Four long-range symmetry phases are identified with their relative transitions. Directional analysis of the order/disorder states using Fröhlich entropy indicates global symmetry breaking along the growth axis and an anisotropic dipolar effective thermodynamic behavior, which ranges from disordered to ordered at the same temperature for different directions in the sample. Results indicate that the macroscopic polarization, driven by nanosized polar regions, follows a microscopic perovskite eight-sites lattice model. [ABSTRACT FROM AUTHOR]Copyright of Physical Review B: Condensed Matter & Materials Physics is the property of American Physical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
F. Di Mei, et al., “Intrinsic negative mass from nonlinearityIntrinsic negative mass from nonlinearity,” Physical Review Letters, vol. 116, no. 15, 2016. Publisher's Version
D. Pierangeli, et al., “Super-crystals in composite ferroelectrics,” Nature Communications, vol. 7, 2016. Publisher's Version
Y. Kabessa, et al., “Standoff Detection of Buried Landmines Using Genetically Engineered Fluorescent Bacterial Sensors,” Biosensors & Bioelectronics , vol. 79, pp. 784- 788, 2016.
2015
F. Di Mei, D. Pierangeli, J. Parravicini, C. Conti, A. J. Agranat, and E. DelRe, “Observation of diffraction cancellation for nonparaxial beams in the scale-free-optics regime.,” Physical Review A: Atomic, Molecular & Optical Physics, vol. 92, no. 1-B, pp. 1 - 5, 2015. Publisher's VersionAbstract
We report the observation of diffraction cancellation for visible beams with widths from tens of wavelengths down to fractions of the optical wavelength. The phenomenon is observed at the transition from diffraction- to antidiffraction-dominated beam propagation, triggered by a thermal shock in a photorefractive nanodisordered lithium-enriched potassium-tantalate-niobate (KTN:Li) crystal. Here beams propagate without distortion, independently of intensity and size. Confirming the main prediction of the scale-free-optics model, we find a single unified light behavior that spans across the entire hierarchy of standard optical spatial scales, from wide plane-wave-like beams that obey geometrical optics down to ultranarrow beams with widths of the order of a single wavelength. [ABSTRACT FROM AUTHOR]Copyright of Physical Review A: Atomic, Molecular & Optical Physics is the property of American Physical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
D. ( 1 ) Pierangeli, 2 ) Di Mei, F. ( 1, 3 ) Conti, C. ( 1, E. ( 1 ) Del Re, and A. J. ( 4 ) Agranat, “Spatial Rogue Waves in Photorefractive Ferroelectrics,” Physical Review Letters, vol. 115, no. 9, 2015. Publisher's VersionAbstract

Rogue waves are observed as light propagates in the extreme nonlinear regime that occurs when a photorefractive ferroelectric crystal is undergoing a structural phase transition. The transmitted spatial light distribution contains bright localized spots of anomalously large intensity that follow a signature long-tail statistics that disappears as the nonlinearity is weakened. The isolated wave events form as out-of-equilibrium response and disorder enhance the Kerr-saturated nonlinearity at the critical point. Self-similarity associable to the individual observed filaments and numerical simulations of the generalized nonlinear Schrodinger equation suggests that dynamics of soliton fusions and scale invariance can microscopically play an important role in the observed rogue intensities and statistics.

D. Pierangeli, et al., “Continuous solitons in lattice nonlinearity,” Phys. Rev. Lett, vol. 114, no. 20, pp. 203901, 2015.
R. Bekenstein, Y. Kabessa, O. Tal, M. A. Bandres, A. J. Agranat, and M. Segev, “Observing Light Dynamics in Micro-sized Schwarzschild Metric,” in QELS Fundamental Science, 2015, pp. FTu4C.2.
J. Parravicini, D. F. Mei, D. Pierangeli, A. J. Agranat, and E. DelRe, “Miniaturized electro-optic infrared beam-manipulator based on 3D photorefractive funnels.,” Journal of Optics, vol. 17, no. 5, pp. 1 - 1, 2015. Publisher's VersionAbstract

We demonstrate tunable electro-optic guiding, shaping, and switching of beams in the near infrared spectrum ( 980 nm), typical of VCSEL technology, using biomimetic 3D funnel waveguides miniaturized into a sample of potassium–lithium–tantalate–niobate. The switchable waveguides are written using the slow photorefractive build-up of a 3D volume space-charge field caused by a diffracting continuous wave low intensity λ = 532 nm beam, and electro-optic functionality is supported by the quadratic electro-optic effect of the high-symmetry paraelectric phase. [ABSTRACT FROM AUTHOR]Copyright of Journal of Optics is the property of IOP Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

E. DelRe, F. Di Mei, J. Parravicini, C. Conti, G. Parravicini, and A. J. Agranat, “Subwavelength anti-diffracting beams propagating over more than 1,000 Rayleigh lengths,” Nature Photonics, vol. 9, no. 4, pp. 228-232, 2015. Publisher's Version
J. Parravicini, R. Martínez Lorente, F. Di Mei, D. Pierangeli, A. J. Agranat, and E. DelRe, “Volume integrated phase modulator based on funnel waveguides for reconfigurable miniaturized optical circuits.,” Optics Letters, vol. 40, no. 7, pp. 1386 - 1389, 2015. Publisher's VersionAbstract

We demonstrate the integration of a miniaturized 30(x)  μm×30(y)  μm×2.7(z)  mm electro-optic phase modulator operating in the near-IR (λ=980  nm) based on the electro-activation of a funnel waveguide inside a paraelectric sample of photorefractive potassium lithium tantalate niobate. The modulator forms a basic tassel in the realization of miniaturized reconfigurable optical circuits embedded in a single solid-state three-dimensional chip.;

Y. Kabessa, A. Yativ, H. Ilan, and A. J. Agranat, “Electro-Optical Modulation with Immunity to Optical Damage by Bipolar Operation in Potassium Lithium Tantalate Niobate,” Optics express , vol. 23, no. 4, pp. 4348-4356, 2015.Abstract
A method for suppressing the formation of optical damage in quadratic electrooptic devices operated at short wavelengths is presented. Formation of optical damage is attributed to the generation of a trapped space charge induced by photoionization of impurity ions by the propagating beam. It is shown that in potassium lithium tantalate niobate where the electrooptic effect is quadratic, operating the electrooptic device by a bipolar driving voltage prevents the space charge from accumulating, which inhibits the formation of the optical damage. A 6 hours continuous operation of electrooptic modulator for a 30 W/cm2 at λ = 445 nm input beam is demonstrated.
A. B. Yashar, H. Ilan, and A. J. Agranat, “Construction of waveguiding structures in potassium lithium tantalate niobate crystals by combined laser ablation and ion implantation,” App. Phys. A-Mat. Sci. & Process, vol. 118, no. 2, pp. 403-407, 2015. Publisher's VersionAbstract
A generic methodology for constructing complex integrated electro-optic circuits in waveguided configurations is presented. The method is based on combining two techniques, 'laser ablation' and 'refractive index engineering by ion implantations.' The constructed circuits are side-cladded by air trenches that were produced using laser ablation and bottom-cladded by a layer with a reduced refractive index which is generated through the implantation of He.sup.+ ions. This fabrication technique enables the construction of circular structures with complex geometry featuring small radii of curvature, and further can be employed to construct microfluidic channels on the same substrate. The research demonstrates waveguides in both linear and circular configurations that were constructed in a potassium lithium tantalate niobate (KLTN) substrate using the aforementioned method, proving that this substrate is a suitable candidate for use in creating laboratories-on-a-chip with multifunctional capabilities. The proposed techniques used in the research are generic and applicable to a wide range of substrates.

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