Publications

2015
Yossef Kabessa, Amir Yativ, Harel Ilan, and Aharon J Agranat. 2015. “Electro-Optical Modulation with Immunity to Optical Damage by Bipolar Operation in Potassium Lithium Tantalate Niobate.” Optics express , 23, 4, Pp. 4348-4356. 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.
D ( 1 ) Pierangeli, 2 ) Di Mei, F. ( 1, 3 ) Conti, C. ( 1, E ( 1 ) Del Re, and AJ ( 4 ) Agranat. 2015. “Spatial Rogue Waves in Photorefractive Ferroelectrics.” Physical Review Letters, 115, 9. Publisher's Version Abstract

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.

Accession Number: edselc.2-52.0-84940688543; (Physical Review Letters, 25 August 2015, 115(9)) Publication Type: Academic Journal; Rights: Copyright 2015 Elsevier B.V., All rights reserved.

E DelRe, F Di Mei, J Parravicini, C Conti, G Parravicini, and AJ Agranat. 2015. “Subwavelength anti-diffracting beams propagating over more than 1,000 Rayleigh lengths.” Nature Photonics, 9, 4, Pp. 228-232. Publisher's Version

Accession Number: edselc.2-52.0-84926333767; (Nature Photonics, 31 March 2015, 9(4):228-232) Publication Type: Academic Journal; Rights: Copyright 2015 Elsevier B.V., All rights reserved.

J Parravicini, R Martínez Lorente, F Di Mei, D Pierangeli, AJ Agranat, and E DelRe. 2015. “Volume integrated phase modulator based on funnel waveguides for reconfigurable miniaturized optical circuits..” Optics Letters, 40, 7, Pp. 1386 - 1389. Publisher's Version Abstract

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.;

Accession Number: 25831339. Language: English. Date Created: 20150402. Update Code: 20150402. Publication Type: Journal Article. Journal ID: 7708433. Publication Model: Print. Cited Medium: Internet. NLM ISO Abbr: Opt Lett. Linking ISSN: 01469592. Subset: In-Data-Review; IM; Date of Electronic Publication: 20150401. ; Original Imprints: Publication: New York, Optical Society of America.

2014
D Pierangeli, F. Di Mei, J. Parravicini, GB Parravicini, A.J. Agranat, C. Conti, and E. DelRe. 2014. “Observation of an intrinsic nonlinearity in the electro-optic response of freezing relaxors ferroelectrics.” OPTICAL MATERIALS EXPRESS, 4, 8, Pp. 1487 - 1493. Publisher's Version Abstract

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

F Di Mei, J Parravicini, D Pierangeli, C Conti, AJ Agranat, and E DelRe. 2014. “Anti-diffracting beams through the diffusive optical nonlinearity..” Optics Express, 22, 25, Pp. 31434 - 31439. Publisher's Version Abstract

Anti-diffraction is a theoretically predicted nonlinear optical phenomenon that occurs when a light beam spontaneously focalizes independently of its intensity. We observe anti-diffracting beams supported by the peak-intensity-independent diffusive nonlinearity that are able to shrink below their diffraction-limited size in photorefractive lithium-enriched potassium-tantalate-niobate (KTN:Li).;

Accession Number: 25607093. Language: English. Date Created: 20150122. Date Completed: 20150512. Update Code: 20150512. Publication Type: Journal Article. Journal ID: 101137103. Publication Model: Print. Cited Medium: Internet. NLM ISO Abbr: Opt Express. Linking ISSN: 10944087. Subset: PubMed-not-MEDLINE; Date of Electronic Publication: 20141215. ; Original Imprints: Publication: Washington, DC : Optical Society of America, 1997-

Itai Hayut, Paul Ben Ishai, Aharon J Agranat, and Yuri Feldman. 2014. “Circular polarization induced by the three-dimensional chiral structure of human sweat ducts..” Physical Review. E, Statistical, Nonlinear, And Soft Matter PhysicsPhys Rev E Stat Nonlin Soft Matter Phys, 89, 4, Pp. 042715 - 042715. Publisher's Version Abstract
The upper part of the human eccrine sweat ducts, embedded within the epidermis layer, have a well-defined helical structure. It was recently suggested that, as electromagnetic entities, the sweat ducts interact with sub-mm waves [Y. Feldman et al., Phys. Rev. Lett. 100, 128102 (2008)]. Although correlation between changes in the reflectance spectrum in this frequency range and physiological activities has been shown, a direct link between the electromagnetic reflection and the helical structure itself has remained to be established. The fact that the sweat ducts manifest natural homochirality is henceforth used to produce this link. We report the detection of circular polarization asymmetry in the electromagnetic reflection from the human skin at sub-THz frequencies in vivo. We compare the results to numerical simulations and to measurements of a fabricated metamaterial. We argue that the observed circular dichroism can be interpreted uniquely as the signature of the helical structure itself. By twisting reflected electromagnetic waves, the human skin exhibits properties which are usually discussed only in the framework of metamaterial science.;
Accession Number: 24827286. Language: English. Date Created: 20140515. Date Completed: 20150415. Update Code: 20150415. Publication Type: Journal Article. Journal ID: 101136452. Publication Model: Print-Electronic. Cited Medium: Internet. NLM ISO Abbr: Phys Rev E Stat Nonlin Soft Matter Phys. Linking ISSN: 15393755. Subset: IM; Date of Electronic Publication: 2014 Apr 25. ; Original Imprints: Publication: Melville, NY : Published by the American Physical Society through the American Institute of Physics, c2001-
Shimon E Lerner, Yuri Feldman, Michal Mierzwa, Marian Paluch, Aharon J Agranat, and Paul Ben Ishai. 2014. “Multivariate pressure effects on an electron hopping process in ferroelectric K[Ta.sub.1-x][Nb.sub.x][O.sub.3].” European Physical Journal B , 7, 158. Publisher's Version
Item Citation: The European Physical Journal B - Condensed Matter and Complex Systems. July 2014, Vol. 87 Issue 7Accession Number: edsgcl.386613351; Publication Type: Academic Journal; Source: The European Physical Journal B - Condensed Matter and Complex Systems; Language: English; Publication Date: 20140701; Rights: Copyright 2014 Gale, Cengage Learning. All rights reserved.; Imprint: Springer
J Parravicini, M Brambilla, L Columbo, F Prati, C Rizza, G Tissoni, AJ Agranat, and E DelRe. 2014. “Observation of electro-activated localized structures in broad area VCSELs..” Optics Express, 22, 24, Pp. 30225 - 30233. Publisher's Version Abstract

We demonstrate experimentally the electro-activation of a localized optical structure in a coherently driven broad-area vertical-cavity surface-emitting laser (VCSEL) operated below threshold. Control is achieved by electro-optically steering a writing beam through a pre-programmable switch based on a photorefractive funnel waveguide.;

Accession Number: 25606953. Language: English. Date Created: 20150122. Update Code: 20150317. Publication Type: Journal Article. Journal ID: 101137103. Publication Model: Print. Cited Medium: Internet. NLM ISO Abbr: Opt Express. Linking ISSN: 10944087. Subset: In-Process; IM; Date of Electronic Publication: 20141201. ; Original Imprints: Publication: Washington, DC : Optical Society of America, 1997-

Sagi Frishman, Alexander Gumennik, Harel Ilan, and Aharon J Agranat. 2014. “A Bragg grating embedded in a slab waveguide fabricated by the implantation of high-energy light ions in KLTN substrate.” Applied Physics B - Lasers and Optics , 115, 1, Pp. 143-147. Publisher's Version Abstract
Electro-optically tunable transmission grating was imprinted in potassium lithium tantalate niobate by irreversible spatial patterning of the dielectric constant. While embedded into waveguided architecture, it provides a reliable and versatile building block for opto-electronic circuitry, capable of both active switching and multiplexing. Realization of such a block is critical for the fabrication of integrated photonic circuits in electro-optic substrates by means of Refractive Index Engineering by fast ion implantation.
Item Citation: Applied Physics B: Lasers and Optics. April 2014, Vol. 115 Issue 1, p143, 5 p.Accession Number: edsgcl.361133533; Publication Type: Academic Journal; Source: Applied Physics B: Lasers and Optics; Language: English; Publication Date: 20140401; Rights: Copyright 2014 Gale, Cengage Learning. All rights reserved., COPYRIGHT 2014 Springer; Imprint: Springer
D Pierangeli, J Parravicini, F Di Mei, GB Parravicini, AJ Agranat, and E DelRe. 2014. “Photorefractive light needles in glassy nanodisordered KNTN.” Optics Letters 39 (6), Pp. 1657 - 1660. Publisher's Version Abstract

We study the formation of 2D self-trapped beams in nanodisordered potassium-sodium-tantalate-niobate (KNTN) cooled below the dynamic glass transition. Supercooling is shown to accelerate the photorefractive response and enhance steady-state anisotropy. Effects in the excited state are attributed to the anomalous slim-loop polarization curve typical of relaxors dominated by non-interacting polar-nano-regions. (C) 2014 Optical Society of America

2013
J Parravicini, D Pierangeli, F Di Mei, C Conti, AJ Agranat, and E DelRe. 2013. “Aging solitons in photorefractive dipolar glasses..” Optics Express, 21, 25, Pp. 30573 - 30579. Publisher's Version Abstract

We study experimentally the aging of optical spatial solitons in a dipolar glass hosted by a nanodisordered sample of photorefractive potassium-sodium-tantalate-niobate (KNTN). As the system ages, the waves erratically explore varying strengths of the nonlinear response, causing them to break up and scatter. We show that this process can still lead to solitons, but in a generalized form for which the changing response is compensated by changing the normalized wave size and intensity so as to maintain fixed the optical waveform.;

Accession Number: 24514634. Language: English. Date Created: 20140211. Date Completed: 20141028. Update Code: 20141125. Publication Type: Journal Article. Journal ID: 101137103. Publication Model: Print. Cited Medium: Internet. NLM ISO Abbr: Opt Express. Linking ISSN: 10944087. Subset: PubMed-not-MEDLINE; Date of Electronic Publication: 20131216. ; Original Imprints: Publication: Washington, DC : Optical Society of America, 1997-

Noam Sapiens and Aharon J Agranat. 2013. “Full C-Band Tunable Laser based on Electroholography.” Optics Letters , 38, Pp. 2131-2133. Abstract
A tunable laser that spans the entire C band is presented. The laser consists of an Er-doped fiber amplifier gain medium, a fiber ring resonator, and an electroholography-based tuning mechanism. The electrohologram used is in the g44 configuration where the Bragg condition can be electrically tuned for a specific wavelength. Two laser architectures are presented, one in which the diffracting beam and one in which the direct beam of the electrohologram is used as the laser output. Switching time between wavelengths is limited by the gain medium relaxation time, since the electrohologram switching time is less than 1 ns.
I Hayut, A Puzenko, P Ben Ishai, A Polsman, AJ Agranat, and Y Feldman. 2013. “The helical structure of sweat ducts: Their influence on the electromagnetic reflection spectrum of the skin.” IEEE Transactions on Terahertz Science and Technology, 3, 2, Pp. 207-215. Publisher's Version
Accession Number: edselc.2-52.0-84874988433; (IEEE Transactions on Terahertz Science and Technology, 2013, 3(2):207-215) Publication Type: Academic Journal; Rights: Copyright 2013 Elsevier B.V., All rights reserved.
Shani Rosen, Gabriel Y Sirat, Harel Ilan, and Aharon J Agranat. 2013. “A sub wavelength localization scheme in optical imaging using conical diffraction.” Optics Express, 21, 8, Pp. 101338. Abstract
In this paper we present a scheme for the acquisition of high temporal resolution images of single particles with enhanced lateral localization accuracy. The scheme, which is implementable as a part of the illumination system of a standard confocal microscope, is based on the generation of a vector beam that is manipulated by polarimetry techniques to create a set of illumination PSFs with different spatial profiles. The combination of data collected in different illumination states enables the extraction of spatial information obscured by diffraction in the standard imaging system. An implementation of the scheme based on the utilization of the unique phenomenon of conical diffraction is presented, and the basic strategy it provides for enhanced localization in the diffraction limited region is demonstrated.
Yossef Kabessa, Victor Korouma, Harel Ilan, Sharon Yagur-Kroll, Shimshon Belkin, and Aharon J Agranat. 2013. “Simultaneous quantification of the fluorescent responses of an ensemble of bacterial sensors..” Biosensors & Bioelectronics, 49, Pp. 394 - 398. Publisher's Version Abstract
Abstract: Bacterial bioreporters are genetically engineered microbial strains capable of detecting specific chemicals, groups of chemicals or global biological effects such as toxicity or genotoxicity. A scheme for simultaneous selective detection of the fluorescent signals emitted by a bacterial biosensor array, able to detect four different types of toxicants, using a single photodetector (photomultiplier) is presented. The underlying principle of the scheme is to convert the spatially distributed signals from all the elements in the array to temporally distributed frequency multiplexed signals at the output of the photodetector. Experimental proof of this concept is demonstrated in a four-channel system, in which low power (a few tens of picowatts) fluorescent signals produced by the bacterial sensors are measured, while maintaining a wide dynamic range of detection (more than 3 orders of magnitude). Simultaneous monitoring of concentrations down to a few mg/l of different chemicals in a liquid sample is demonstrated. [Copyright &y& Elsevier]Copyright of Biosensors & Bioelectronics is the property of Elsevier Science Publishing Company, Inc. 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.)
Accession Number: 89435767; Kabessa, Yossef 1; Email Address: yossi.kabessa@mail.huji.ac.il Korouma, Victor 1 Ilan, Har'el 1 Yagur-Kroll, Sharon 2 Belkin, Shimshon 2 Agranat, Aharon J. 1; Affiliation: 1: Department of Applied Physics and the Brojde Center for Innovative Engineering and Computer Science, The Hebrew University of Jerusalem, Jerusalem 91904, Israel 2: Department of Plant & Environmental Sciences, Institute of Life Science, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; Source Info: Nov2013, Vol. 49, p394; Subject Term: BIOSENSORS; Subject Term: RECOMBINANT microorganisms; Subject Term: GENETIC toxicology; Subject Term: PHOTODETECTORS; Subject Term: IDENTIFICATION of bacteria; Subject Term: FLUORIMETRY; Author-Supplied Keyword: Bacterial whole-cell biosensors; Author-Supplied Keyword: Fluorescence; Author-Supplied Keyword: GFP reporter gene; Author-Supplied Keyword: Simultaneous sampling; Number of Pages: 5p; Document Type: Article
2012
J Parravicini, C Conti, E DelRe, and AJ Agranat. 2012. “Equalizing disordered ferroelectrics for diffraction cancellation.” Applied Physics Letters, 101, 11. Publisher's Version

Accession Number: edselc.2-52.0-84866336071; (Applied Physics Letters, 10 September 2012, 101(11)) Publication Type: Academic Journal; Rights: Copyright 2012 Elsevier B.V., All rights reserved.

E DelRe, A Pierangelo, J Parravicini, S Gentilini, and AJ Agranat. 2012. “Funnel-based biomimetic volume optics.” Optics Express 20 (15), Pp. 16631 - 16638. Publisher's Version Abstract

We demonstrate the use of three-dimensional funnel index of refraction patterns analogous to those of retinal Muller cells as support for tunable and multi-functional volume optical component miniaturization and integration. Our experiments in paraelectric photorefractive crystals show how a single funnel can act both as a waveguide and a tunable focusing/defocusing micro-lens. Pairing multiple funnel patterns, we are also able to demonstrate ultra-compact tunable beam-splitting, with distinct guided output modes in under 1mm of propagation. (C) 2012 Optical Society of America

Electrically controlled absorption was observed in a slab waveguide, fabricated in a potassium lithium tantalate niobate substrate by proton implantation, at an energy of E=1.15 MeV and a fluence of 6.1×1016ions/cm2. The implantation created an amorphous layer which acted as the cladding with an adjacent proton doped layer at its bottom. It is suggested that a n-i junction is formed at the interface between the proton layer and the substrate, which is the core of the waveguide. The electrically controlled absorption is attributed to changes in the width of the depletion area of the n-i junction induced by the applied field. [ABSTRACT FROM AUTHOR]Copyright of Applied Physics Letters is the property of American Institute of Physics 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.)
Accession Number: 84623481; Ilan, Har'el 1 Agranat, Aharon J. 1; Affiliation: 1: Department of Applied Physics and the Brojde Center for Innovative Engineering and Computer Science, The Hebrew University of Jerusalem, Jerusalem 91904,; Source Info: 12/24/2012, Vol. 101 Issue 26, p261101; Subject Term: PROTONS; Subject Term: WAVEGUIDES; Subject Term: POTASSIUM; Subject Term: LITHIUM tantalate; Subject Term: SUBSTRATES (Materials science); Number of Pages: 4p; Illustrations: 3 Diagrams, 3 Graphs; Document Type: Article
Harel Ilan, Sagi Frishman, and Aharon J Agranat. 2012. “Investigation of the conduction in an implanted layer of protons in a potassium lithium tantalate niobate substrate..” Applied Physics Letters, 101, 14, Pp. 141111. Publisher's Version Abstract
The electrical conductivity in the amorphous layer formed by the implantation of protons at 1.15 MeV with fluence of 1.1×1017 ions/cm2 within the depth of potassium lithium tantalate niobate is investigated by four probes and Hall effect measurements. It is shown that the conductivity originates from electrons that are induced by 'Hydrogen donors' that reside in a band structure 0.22 eV below the conduction band. It is claimed that this phenomenon enables the construction of conductive structures with submicron features within the depth of the substrate that can be used as embedded electrodes in electrooptical devices integrated in this substrate. [ABSTRACT FROM AUTHOR]Copyright of Applied Physics Letters is the property of American Institute of Physics 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.)
Accession Number: 82303241; Ilan, Har'el 1 Frishman, Sagi 1 Agranat, Aharon J. 1; Affiliation: 1: Department of Applied Physics, and The Brojde Center for Innovative Engineering and Computer Science, The Hebrew University of Jerusalem, Jerusalem 91904,; Source Info: 10/1/2012, Vol. 101 Issue 14, p141111; Subject Term: ELECTRIC conductivity -- Research; Subject Term: PROTONS; Subject Term: POTASSIUM niobate; Subject Term: LITHIUM tantalate; Subject Term: LITHIUM niobate; Subject Term: SUBSTRATES (Materials science); Number of Pages: 3p; Illustrations: 1 Diagram, 1 Chart, 2 Graphs; Document Type: Article

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