Recent Papers

2017

High Responsivity Fire Detectors based on PbS Colloidal Quantum Dot Photoconductors
Photon. Tech. Lett. Preprint


All-optical guided-wave random laser in nematic liquid crystals
Optics Express Vol. 25, Issue 5, pp. 4672-4679 (2017)


Magnetic routing of light-induced waveguides
Nat. Comm. 8, 14452 (2017)


Nematicon-enhanced spontaneous symmetry breaking
Mol. Cryst. Liq. Cryst., in press


Erratum: \"Soliton-assisted random lasing in optically-pumped liquid crystals
Appl. Phys. Lett. 110 (1), 1019902 (2017)


Bistable beam propagation in liquid crystals
IEEE Journal of Quantum Electronics Volume: 53, Issue: 1,


Interplay between diffraction and the Pancharatnam-Berry phase in inhomogeneously twisted anisotropic media
Phys. Rev. A 95, 023823 (2017)


2016

Anomalous diffraction in hyperbolic materials
Phys. Rev. A 94, 033830


Linear and nonlinear light beam propagation in chiral nematic liquid crystal waveguides
Photon. Lett. Pol. 8 (1), 1 (2016)


Quenching nematicon fluctuations via photostabilization
Photon. Lett. Pol. 8 (1), 2-4 (2016)


NooEL - Nonlinear optics and optoelectronics Laboratory -
University of Rome "Roma Tre", Department of Engineering, INFN, CNISM

The University "Roma Tre", established in 1992, has developed with NooEL a strong commitment in Optoelectronics and Photonics, carrying out advanced research in several areas of nonlinear optics, nanophotonics and near infrared detection.


Publication highlights


Alessandro Alberucci , Chandroth P. Jisha, Lorenzo Marrucci, and Gaetano Assanto, Electromagnetic Confinement via Spin-Orbit Interaction in Anisotropic Dielectrics, ACS Photonics, 2016, 3 (12), pp 2249-2254

Abstract:

We investigate electromagnetic propagation in uniaxial dielectrics with a transversely varying orientation of the optic axis, the latter staying orthogonal everywhere in the propagation direction. In such a geometry, the field experiences no refractive index gradients, yet it acquires a transversely modulated Pancharatnam-Berry phase, that is, a geometric phase originating from a spin-orbit interaction. We show that the periodic evolution of the geometric phase versus propagation gives rise to a longitudinally invariant effective potential. In certain configurations, this geometric phase can provide transverse confinement and waveguiding. The theoretical findings are tested and validated against numerical simulations of the complete Maxwell\'s equations. Our results introduce and illustrate the role of geometric phases on electromagnetic propagation over distances well exceeding the diffraction length, paving the way to a whole new family of guided waves and waveguides that do not rely on refractive index tailoring.



Urszula A. Laudyn, Paweł S. Jung, Mirosław A. Karpierz & Gaetano Assanto, Quasi two-dimensional astigmatic solitons in soft chiral metastructures, Scientific Reports 6, Article number: 22923 doi:10.1038/srep22923

Abstract:

We investigate a non-homogeneous layered structure encompassing dual spatial dispersion: continuous diffraction in one transverse dimension and discrete diffraction in the orthogonal one. Such dual diffraction can be balanced out by one and the same nonlinear response, giving rise to light self-confinement into astigmatic spatial solitons: self-focusing can compensate for the spreading of a bell-shaped beam, leading to quasi-2D solitary wavepackets which result from 1D transverse self-localization combined with a discrete soliton. We demonstrate such intensity-dependent beam trapping in chiral soft matter, exhibiting one-dimensional discrete diffraction along the helical axis and one-dimensional continuous diffraction in the orthogonal plane. In nematic liquid crystals with suitable birefringence and chiral arrangement, the reorientational nonlinearity is shown to support bell-shaped solitary waves with simple astigmatism dependent on the medium birefringence as well as on the dual diffraction of the input wavepacket. The observations are in agreement with a nonlinear nonlocal model for the all-optical response.



Andrea De Iacovo, Carlo Venettacci, Lorenzo Colace, Leonardo Scopa, Sabrina Foglia, PbS Colloidal Quantum Dot Photodetectors operating in the near infrared, Scientific Reports 6, Article number: 37913 (2016)

Abstract:

Colloidal quantum dots have recently attracted lot of interest in the fabrication of optoelectronic devices due to their unique optical properties and their simple and low cost fabrication. PbS nanocrystals emerged as the most advanced colloidal material for near infrared photodetectors. In this work we report on the fabrication and characterization of PbS colloidal quantum dot photoconductors. In order to make devices suitable for the monolithic integration with silicon electronics, we propose a simple and low cost process for the fabrication of photodetectors and investigate their operation at very low voltage bias. Our photoconductors feature high responsivity and detectivity at 1.3 μm and 1 V bias with maximum values of 30 A/W and 2x10^10 cmHz^(1/2)W^(−1), respectively. Detectivity close to 10^11 cmHz^(1/2)W^(−1) has been obtained resorting to bridge sensor readout.



V. Sorianello, G. De Angelis, A. De Iacovo, L. Colace, S. Faralli, and M. Romagnoli, High responsivity SiGe heterojunction phototransistor on silicon photonics platform, Opt. Express 23(22), 28163-28169 (2015)

Abstract:

We report on a novel near infrared SiGe phototransistor fabricated by a standard silicon photonics foundry. The device is first investigated by simulations. The fabricated devices are characterized in terms of current-voltage characteristics at different optical power. Typical phototransistors exhibit 1.55um record responsivity at low optical power exceeding 232A/W and 42A/W at 5V and 1V bias, respectively. A differential detection scheme is also proposed for the dark current cancellation to significantly increase the device sensitivity.



A. Alberucci, A. Piccardi, N. Kravets, O. Buchnev, and G. Assanto, Soliton enhancement of sponaneous symmetry breaking, Optica 2 (9), 783-9 (2015)

Abstract:

Spontaneous symmetry breaking (SSB) occurs when noise triggers an initially symmetric system to evolve toward one of its nonsymmetric states. Topological and optical SSB involve material reconfiguration/transition and light propagation/distribution in time or space, respectively. In anisotropic optical media, light beam propagation and distribution of the optic axis can be linked, thereby connecting topological and optical SSB. Using nonlinear soft matter, namely uniaxial liquid crystals, we report on simultaneous topological and optical SSB, showing that spatial solitons enhance the noise-driven transition of the medium from a symmetric to an asymmetric configuration, while acquiring a power-dependent transverse velocity in either of two specular directions with respect to the initial wavevector. Solitons enhance SSB by further distorting the optic axis distribution through nonlinear reorientation, resulting in power-tunable walk-off as well as hysteresis in beam refraction versus angle of incidence.





Conferences


Future


Recent


SPIE Photonics Europe 2016

CLEO 2015

Group IV Photonics 2015

GE 2015 Annual Meeting

Fotonica 2015

5th Workshop on Liquid Crystals for Photonics

Nonlinear Photonics 2014

Group IV Photonics 2014

FOTONICA 2014