10 Jan 2019

Olivia Chong and Manuel Morales have temporarily joined the Fields & Waves Lab within the framework of the MIT student externship program.

They will be working on the study of metamaterial-based analog computing.

10 Dec 2018

The call for nominations for the 2019 EurAAP Leopold B. Felsen Award for Excellence in Electrodynamics is open.

The Award was originally established jointly by the University of Siena and the University of Sannio, funded through a donation from Michael and Judy Felsen in fulfillment of the last wishes of their father, Professor Leo Felsen (1924-2005). Since 2015, the Award is established by the European Association on Antennas and Propagation (EurAAP).

The main purpose of the Award is to keep alive Prof. Felsen’s memory and scientific legacy, as well as to foster academic excellence in the electromagnetics community, by giving recognition to outstanding fundamental contributions from early stage researchers in electrodynamics.

The Award, by nomination only, will be presented annually, as a career award, to an early stage researcher. Eligible nominees should be under 40 years of age at the submission deadline. Previous awardees (also from the former Sannio and Siena editions) are not eligible.

The Award consists of a prize of 4,000 euro, which will be funded by the Felsen Family through a donation, and will be officially presented at the banquet of the upcoming [13th European Conference on Antennas and Propagation] (EuCAP 2019).

Candidates from all areas of Electromagnetics are eligible to apply. Selection will be based on quality and significance of the candidates’ contributions to the field, and on the recommendation of the referees.

The deadline for submission of the nominations is January 31, 2019.

More details can be found here.

Our paper on “Aperiodic-order-induced enhancement of weak nonlocality in multilayered dielectric metamaterials” [1] has been published in [Physical Review B].

1. Coppolaro, M., Castaldi, G., & Galdi, V. (2018). Aperiodic order induced enhancement of weak nonlocality in multilayered dielectric metamaterials. Physical Review B 98(19), 195128.

Recent studies on fully dielectric multilayered metamaterials have shown that the negligibly small nonlocal effects (spatial dispersion) typically observed in the limit of deeply subwavelength layers may be significantly enhanced by peculiar boundary effects occurring in certain critical parameter regimes. These phenomena, observed so far in periodic and randomly disordered geometries, are manifested as strong differences between the exact optical response of finite-size metamaterial samples and the prediction from conventional effective-theory-medium models based on mixing formulae. Here, with specific focus on the Thue-Morse geometry, we make a first step toward extending the studies above to the middle-ground of aperiodically ordered multilayers, lying in between perfect periodicity and disorder. We show that, also for these geometries, there exist critical parameter ranges that favor the buildup of boundary effects leading to strong enhancement of the (otherwise negligibly weak) nonlocality. However, the underlying mechanisms are fundamentally different from those observed in the periodic case, and exhibit typical footprints (e.g., fractal gaps, quasi-localized states) that are distinctive of aperiodic order. The outcomes of our study indicate that aperiodic order plays a key role in the buildup of the aforementioned boundary effects, and may also find potential applications to optical sensors, absorbers and lasers.

@article{IJ134_PRB_98_195128_2018,
title = {Aperiodic order induced enhancement of weak nonlocality in multilayered dielectric metamaterials},
author = {Coppolaro, Marino and Castaldi, Giuseppe and Galdi, Vincenzo},
journal = {Physical Review B},
volume = {98},
issue = {19},
pages = {195128},
numpages = {12},
year = {2018},
month = nov,
publisher = {American Physical Society},
doi = {10.1103/PhysRevB.98.195128}
}

Our paper on “Aperiodic-order-induced enhancement of weak nonlocality in multilayered dielectric metamaterials” has been accepted for publication in Physical Review B.

An arXiv preprint is available.

Our paper on “Space-time-coding digital metasurfaces,” [1] in collaboration with Tie Jun Cui’s Group (Southeast University), has been published in Nature Communications.

1. Zhang, L., Chen, X. Q., Liu, S., Zhang, Q., Zhao, J., Dai, J. Y., … Cui, T. J. (2018). Space-time-coding digital metasurfaces. Nature Communications 9(1), 4334.

The recently proposed digital coding metasurfaces make it possible to control electromagnetic (EM) waves in real time, and allow the implementation of many different functionalities in a programmable way. However, current configurations are only space-encoded, and do not exploit the temporal dimension. Here, we propose a general theory of space-time modulated digital coding metasurfaces to obtain simultaneous manipulations of EM waves in both space and frequency domains, i.e., to control the propagation direction and harmonic power distribution simultaneously. As proof-of-principle application examples, we consider harmonic beam steering, beam shaping, and scattering-signature control. For validation, we realize a prototype controlled by a field-programmable gate array, which implements the harmonic beam steering via an optimized space-time coding sequence. Numerical and experimental results, in good agreement, demonstrate good performance of the proposed approach, with potential applications to diverse fields such as wireless communications, cognitive radars, adaptive beamforming, holographic imaging.

@article{IJ133_NatComm_9_4334_2018,
author = {Zhang, Lei and Chen, Xiao Qing and Liu, Shuo and Zhang, Qian and Zhao, Jie and Dai, Jun Yan and Bai, Guo Dong and Wan, Xiang and Cheng, Qiang and Castaldi, Giuseppe and Galdi, Vincenzo and Cui, Tie Jun},
title = {Space-time-coding digital metasurfaces},
journal = {Nature Communications},
year = {2018},
volume = {9},
number = {1},
pages = {4334},
doi = {10.1038/s41467-018-06802-0},
note = {https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-018-06802-0/MediaObjects/41467_2018_6802_MOESM1_ESM.pdf},
month = oct
}

Our paper on “Boundary effects of weak nonlocality in multilayered dielectric metamaterials,” [1] in collaboration with Andrea Alù (ASRC-CUNY), has been published in Physical Review Applied.

1. Castaldi, G., Alù, A., & Galdi, V. (2018). Boundary effects of weak nonlocality in multilayered dielectric metamaterials. Physical Review Applied 10(3), 034060.

Nonlocal (spatial-dispersion) effects in multilayered metamaterials composed of periodic stacks of alternating, deeply subwavelength dielectric layers are known to be negligibly weak. Counterintuitively, under certain critical conditions, weak nonlocality may build up strong boundary effects that are not captured by conventional (local) effective-medium models based on simple mixing formulas. Here we show that this phenomenon can be fruitfully studied and understood in terms of error propagation in the iterated maps of the trace and antitrace of the optical transfer matrix of the multilayer. Our approach effectively parameterizes these peculiar effects via remarkably simple and insightful closed-form expressions, which enable direct identification of the critical parameters and regimes. We also show how these boundary effects can be captured by suitable nonlocal corrections.

@article{IJ132_PRAppl_10_034060_2018,
title = {Boundary effects of weak nonlocality in multilayered dielectric metamaterials},
author = {Castaldi, Giuseppe and Al\u, Andrea and Galdi, Vincenzo},
journal = {Physical Review Applied},
volume = {10},
issue = {3},
pages = {034060},
numpages = {13},
year = {2018},
month = sep,
publisher = {American Physical Society},
doi = {10.1103/PhysRevApplied.10.034060},
}

29 Aug 2018

We have presented four papers [1, 2, 3, 4] at the 12th International Congress on Engineered Material Platforms for Novel Wave Phenomena (Metamaterials), Espoo, Finland, Aug. 27-30, 2018.

1. Scaravilli, M., Micco, A., Castaldi, G., Coppola, G., Gioffrè, Iodice, M., … Cusano, A. (2018). Fiber-tip coupling of Bloch surface waves. In International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS). Espoo, Finland, Aug. 27-30, 2018.
@inproceedings{Scaravilli_2018-Metamaterials,
author = {Scaravilli, M. and Micco, A. and Castaldi, G. and Coppola, G. and Gioffr\e and Iodice, M. and La Ferrara, V. and Galdi, V. and Cusano, A.},
booktitle = {International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS)},
title = {Fiber-tip coupling of Bloch surface waves},
year = {2018},
organization = {Espoo, Finland, Aug. 27-30, 2018},
month = aug
}

2. Castaldi, G., Alù, A., & Galdi, V. (2018). Revisiting the boundary effects of weak nonlocality in multilayered dielectric metamaterials: A trace and anti-trace map approach. In International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS). Espoo, Finland, Aug. 27-30, 2018.
@inproceedings{Castaldi_2018-Metamaterials,
author = {Castaldi, Giuseppe and Al\u, Andrea and Galdi, Vincenzo},
booktitle = {International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS)},
title = {Revisiting the boundary effects of weak nonlocality in multilayered dielectric metamaterials: A trace and anti-trace map approach},
year = {2018},
organization = {Espoo, Finland, Aug. 27-30, 2018},
month = aug
}

3. Moccia, M., Castaldi, G., Alù, A., & Galdi, V. (2018). A study of spectral singularities in non-Hermitian cylindrical core-shell geometries. In International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS). Espoo, Finland, Aug. 27-30, 2018.
@inproceedings{Moccia_2018-Metamaterials,
author = {Moccia, Massimo and Castaldi, Giuseppe and Al\u, Andrea and Galdi, Vincenzo},
booktitle = {International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS)},
title = {A study of spectral singularities in non-Hermitian cylindrical core-shell geometries},
year = {2018},
organization = {Espoo, Finland, Aug. 27-30, 2018},
month = aug
}

4. Koral, C., Papari, G., Andreone, A., Moccia, M., Castaldi, G., Galdi, V., … Cui, T. J. (2018). Diffuse THz scattering via coding metasurfaces. In International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS). Espoo, Finland, Aug. 27-30, 2018.
@inproceedings{Koral_2018-Metamaterials,
author = {Koral, C. and Papari, G. and Andreone, A. and Moccia, M. and Castaldi, G. and Galdi, V. and Liu, S. and R.Y., Wu and Cui, T.J.},
booktitle = {International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS)},
title = {Diffuse THz scattering via coding metasurfaces},
year = {2018},
organization = {Espoo, Finland, Aug. 27-30, 2018},
month = aug
}

Our paper on “Boundary effects of weak nonlocality in multilayered dielectric metamaterials,” in collaboration with Andrea Alù (ASRC-CUNY), has been accepted for publication in Physical Review Applied.

An arXiv preprint is available.

Our paper on “Suboptimal coding metasurfaces for terahertz diffuse scattering,” [1] in collaboration with Tie Jun Cui’s Group (Southeast University), has been published in Scientific Reports.

1. Moccia, M., Koral, C., Papari, G. P., Liu, S., Zhang, L., Wu, R. Y., … Andreone, A. (2018). Suboptimal coding metasurfaces for terahertz diffuse scattering. Scientific Reports 8, 11908.

Coding metasurfaces, composed of only two types of elements arranged according to a binary code, are attracting a steadily increasing interest in many application scenarios. In this study, we apply this concept to attain diffuse scattering at THz frequencies. Building up on previously derived theoretical results, we carry out a suboptimal metasurface design based on a simple, deterministic and computationally inexpensive algorithm that can be applied to arbitrarily large structures. For experimental validation, we fabricate and characterize three prototypes working at 1 THz, which, in accordance with numerical predictions, exhibit significant reductions of the radar cross-section, with reasonably good frequency and angular stability. Besides the radar-signature control, our results may also find potentially interesting applications to diffusive imaging, computational imaging, and (scaled to optical wavelengths) photovoltaics.

@article{IJ131_SREP_8_11908_2018,
author = {Moccia, Massimo and Koral, Can and Papari, Gian Paolo and Liu, Shuo and Zhang, Lei and Wu, Rui Yuan and Castaldi, Giuseppe and Cui, Tie Jun and Galdi, Vincenzo and Andreone, Antonello},
title = {Suboptimal coding metasurfaces for terahertz diffuse scattering},
journal = {Scientific Reports},
year = {2018},
volume = {8},
pages = {11908},
month = aug,
url = {https://www.nature.com/articles/s41598-018-30375-z},
doi = {10.1038/s41598-018-30375-z},
note = {https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-018-30375-z/MediaObjects/41598_2018_30375_MOESM1_ESM.pdf}
}

Our paper on “Suboptimal coding metasurfaces for terahertz diffuse scattering,” in collaboration with Tie Jun Cui’s Group (Southeast University), has been accepted for publication in Scientific Reports.

We have presented two talks [1, 2] at the IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (IEEE-APS/URSI), Boston, MA, USA, July 8-13, 2018.

1. Moccia, M., Castaldi, G., Alù, A., & Galdi, V. (2018). Spectral singularities in cylindrical non-Hermitian structures. In USNC-URSI Radio Science Meeting. Boston, MA, USA, July 8-13, 2018.
@inproceedings{Moccia_2018-USNC-URSI,
author = {Moccia, Massimo and Castaldi, Giuseppe and Al\u, Andrea and Galdi, Vincenzo},
booktitle = {USNC-URSI Radio Science Meeting},
title = {Spectral singularities in cylindrical non-Hermitian structures},
year = {2018},
organization = {Boston, MA, USA, July 8-13, 2018},
month = jul
}

2. Castaldi, G., Alù, A., & Galdi, V. (2018). Boundary effects of weak nonlocality in multilayered dielectric metamaterials. In USNC-URSI Radio Science Meeting. Boston, MA, USA, July 8-13, 2018.
@inproceedings{Castaldi_2018-USNC-URSI,
author = {Castaldi, Giuseppe and Al\u, Andrea and Galdi, Vincenzo},
booktitle = {USNC-URSI Radio Science Meeting},
title = {Boundary effects of weak nonlocality in multilayered dielectric metamaterials},
year = {2018},
organization = {Boston, MA, USA, July 8-13, 2018},
month = jul
}

Our paper on “Excitation of Bloch surface waves on an optical fiber tip,” [1] in collaboration with Andrea Cusano’s Group, CNR-IMM and ENEA has been published in Advanced Optical Materials.

1. Scaravilli, M., Micco, A., Castaldi, G., Coppola, G., Gioffrè, M., Iodice, M., … Cusano, A. (2018). Excitation of Bloch surface waves on an optical fiber tip. Advanced Optical Materials 6(9), 1800477.

The integration of structures supporting Bloch surface waves (BSWs) with optical fibers is highly desirable, since it would enable the development of high-figure-of-merit miniaturized all-fiber optrodes, opening new pathways within the “lab-on-fiber” roadmap. Here, the first experimental demonstration of grating-assisted excitation of BSWs on the tip of single-mode fibers in the near-infrared region is provided. This is attained via fabrication of a 1D diffraction grating on the fiber facet, and subsequent deposition of a 1D photonic crystal. In spite of a resonance broadening due to grating-induced morphological perturbations, the measured Q-factor of 50 is still higher than typical lab-on-tip plasmonic-probe benchmarks. With a view toward biomolecular sensing, a surface sensitivity of 1.22 nm nm−1 of homogeneous overlay deposited over the active region, which is in line with most plasmonic optrodes largely used in connection with optical fibers, is evaluated. The results also highlight the current limitations and the challenges to face for the development of advanced BSW-based fiber-tip platforms for biological sensing applications.

author = {Scaravilli, Michele and Micco, Alberto and Castaldi, Giuseppe and Coppola, Giuseppe and Gioffr\e, Mariano and Iodice, Mario and La Ferrara, Vera and Galdi, Vincenzo and Cusano, Andrea},
title = {Excitation of Bloch surface waves on an optical fiber tip},
pages = {1800477},
volume = {6},
issue = {9},
year = {2018},
month = oct,
keywords = {diffraction gratings, lab-on-fiber, optical fiber sensors, photonic crystals, surface waves},
}

A Tutorial Session on Metamaterials was held at the 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace 2018) in Rome, Italy. Tutorial lectures were given by Profs. Vincenzo Galdi (University of Sannio), Alessio Monti (Niccolò Cusano University), and Mirko Barbuto (Niccolò Cusano University).

Our paper on “Excitation of Bloch surface waves on an optical fiber tip,” in collaboration with Andrea Cusano’s Group, CNR-IMM and ENEA has been accepted for publication in Advanced Optical Materials.

The paper “Roadmap on transformation optics” [1] has been published in the Journal of Optics. Section 3 contains a perspective on nonlocal and non-Hermitian extensions authored by Prof. Vincenzo Galdi.

1. McCall, M., Pendry, J. B., Galdi, V., Lai, Y., Horsley, S. A. R., Li, J., … Cummer, S. A. (2018). Roadmap on transformation optics. Journal of Optics 20(6), 063001.

Transformation optics asks, using Maxwell’s equations, what kind of electromagnetic medium recreates some smooth deformation of space? The guiding principle is Einstein’s principle of covariance: that any physical theory must take the same form in any coordinate system. This requirement fixes very precisely the required electromagnetic medium. The impact of this insight cannot be overestimated. Many practitioners were used to thinking that only a few analytic solutions to Maxwell’s equations existed, such as the monochromatic plane wave in a homogeneous, isotropic medium. At a stroke, transformation optics increases that landscape from ‘few’ to ‘infinity’, and to each of the infinitude of analytic solutions dreamt up by the researcher, there corresponds an electromagnetic medium capable of reproducing that solution precisely. The most striking example is the electromagnetic cloak, thought to be an unreachable dream of science fiction writers, but realised in the laboratory a few months after the papers proposing the possibility were published. But the practical challenges are considerable, requiring meta-media that are at once electrically and magnetically inhomogeneous and anisotropic. How far have we come since the first demonstrations over a decade ago? And what does the future hold? If the wizardry of perfect macroscopic optical invisibility still eludes us in practice, then what compromises still enable us to create interesting, useful, devices? While three-dimensional (3D) cloaking remains a significant technical challenge, much progress has been made in two dimensions. Carpet cloaking, wherein an object is hidden under a surface that appears optically flat, relaxes the constraints of extreme electromagnetic parameters. Surface wave cloaking guides sub-wavelength surface waves, making uneven surfaces appear flat. Two dimensions is also the setting in which conformal and complex coordinate transformations are realisable, and the possibilities in this restricted domain do not appear to have been exhausted yet. Beyond cloaking, the enhanced electromagnetic landscape provided by transformation optics has shown how fully analytic solutions can be found to a number of physical scenarios such as plasmonic systems used in electron energy loss spectroscopy and cathodoluminescence. Are there further fields to be enriched? A new twist to transformation optics was the extension to the spacetime domain. By applying transformations to spacetime, rather than just space, it was shown that events rather than objects could be hidden from view; transformation optics had provided a means of effectively redacting events from history. The hype quickly settled into serious nonlinear optical experiments that demonstrated the soundness of the idea, and it is now possible to consider the practical implications, particularly in optical signal processing, of having an ‘interrupt-without-interrupt’ facility that the so-called temporal cloak provides. Inevitable issues of dispersion in actual systems have only begun to be addressed. Now that time is included in the programme of transformation optics, it is natural to ask what role ideas from general relativity can play in shaping the future of transformation optics. Indeed, one of the earliest papers on transformation optics was provocatively titled ‘General Relativity in Electrical Engineering’. The answer that curvature does not enter directly into transformation optics merely encourages us to speculate on the role of transformation optics in defining laboratory analogues. Quite why Maxwell’s theory defines a ‘perfect’ transformation theory, while other areas of physics such as acoustics are not apparently quite so amenable, is a deep question whose precise, mathematical answer will help inform us of the extent to which similar ideas can be extended to other fields. The contributors to this Roadmap, who are all renowned practitioners or inventors of transformation optics, will give their perspectives into the field’s status and future development.

@article{IJ129_JO_20_063001_2018,
author = {McCall, Martin and Pendry, John B and Galdi, Vincenzo and Lai, Yun and Horsley, S A R and Li, Jensen and Zhu, Jian and Mitchell-Thomas, Rhiannon C and Quevedo-Teruel, Oscar and Tassin, Philippe and Ginis, Vincent and Martini, Enrica and Minatti, Gabriele and Maci, Stefano and Ebrahimpouri, Mahsa and Hao, Yang and Kinsler, Paul and Gratus, Jonathan and Lukens, Joseph M and Weiner, Andrew M and Leonhardt, Ulf and Smolyaninov, Igor I and Smolyaninova, Vera N and Thompson, Robert T and Wegener, Martin and Kadic, Muamer and Cummer, Steven A},
title = {Roadmap on transformation optics},
journal = {Journal of Optics},
volume = {20},
number = {6},
pages = {063001},
doi = {10.1088/2040-8986/aab976},
url = {http://stacks.iop.org/2040-8986/20/i=6/a=063001},
year = {2018}
}

23 Jan 2018

Michele Scaravilli has successfully defended his Ph.D. thesis in Information Technologies for Engineering entitled “Bloch‐Surface‐Wave Assisted Lab‐on‐Fiber Optrodes”, supervised by Profs. Vincenzo Galdi and Andrea Cusano.

Congratulations Dr. Scaravilli!

1 Dec 2017

Marino Coppolaro has joined the Fields & Waves Lab as a Ph.D. student in Information Technologies for Engineering.

His Ph.D. work will be focused on the study of nonlocal effects in metamaterials.

17 Nov 2017

The call for nominations for the 2018 EurAAP Leopold B. Felsen Award for Excellence in Electrodynamics is open.

The Award was originally established jointly by the University of Siena and the University of Sannio, funded through a donation from Michael and Judy Felsen in fulfillment of the last wishes of their father, Professor Leo Felsen (1924-2005). Since 2015, the Award is established by the European Association on Antennas and Propagation (EurAAP).

The main purpose of the Award is to keep alive Prof. Felsen’s memory and scientific legacy, as well as to foster academic excellence in the electromagnetics community, by giving recognition to outstanding fundamental contributions from early stage researchers in electrodynamics.

The Award, by nomination only, will be presented annually, as a career award, to an early stage researcher. Eligible nominees should be under 40 years of age at the submission deadline. Previous awardees (also from the former Sannio and Siena editions) are not eligible.

The Award consists of a prize of 4,000 euro, which will be funded by the Felsen Family through a donation, and will be officially presented at the banquet of the upcoming 12th European Conference on Antennas and Propagation (EuCAP 2018).

Candidates from all areas of Electromagnetics are eligible to apply. Selection will be based on quality and significance of the candidates’ contributions to the field, and on the recommendation of the referees.

The deadline for submission of the nominations is January 31, 2018.

More details can be found here.

The journal Nanomaterials and Nanotechnology will publish a Special Collection on Recent Advances and Trends in Optical Metamaterials and Metasurfaces, coordinated by the Guest Editors Profs. Mirko Barbuto (Niccolò Cusano University), Alessio Monti (Niccolò Cusano University), and Maria Principe (University of Salerno), and Vincenzo Galdi (University of Sannio).

More details and the call for papers can be found here.

The 5th IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace 2018) will convene in Rome, Italy, from June 20 - 22, 2018.

A special session on Metamaterials for Aerospace is being organized by Vincenzo Galdi (University of Sannio) and Filiberto Bilotti (University of Roma Tre).

More details and the call for papers can be found here.

The XXXV Edition of the EUPROMETA Distributed Doctoral School on Metamaterials will be held in Rome, Italy, from December 18-22, 2017. The school will be focused on Advanced Electromagnetic Materials and Surfaces for Novel Wave Phenomena.

More details can be found here.

14 Sep 2017

We have presented an invited talk [1] at the 19th International Conference on Electromagnetics in Advanced Applications (ICEAA), Verona, Italy, Sep. 11-15, 2017.

1. Moccia, M., Castaldi, G., & Galdi, V. (2017). Some perspectives in aperiodically ordered antenna arrays and metasurfaces. In Proc. 19th International Conference on Electromagnetics in Advanced Applications (ICEAA) (pp. 733–735). Verona, Italy, Sep. 11-15, 2017.
@inproceedings{Moccia_2017-ICEAA,
author = {Moccia, Massimo and Castaldi, Giuseppe and Galdi, Vincenzo},
booktitle = {Proc. 19th International Conference on Electromagnetics in Advanced Applications
(ICEAA)},
title = {Some perspectives in aperiodically ordered antenna arrays and metasurfaces},
year = {2017},
organization = {Verona, Italy, Sep. 11-15, 2017},
doi = {10.1109/ICEAA.2017.8065352},
page = {733-735},
month = sep
}

We have presented two talks [1, 2] at the 7th EOS Topical Meeting on Optical Microsystems (OµS) and the 3rd EOS Topical Meeting on Optics at the Nanoscale (ONS), Capri, Italy, Sep. 10-14, 2017.

1. Scaravilli, M., Micco, A., Castaldi, G., Gioffrè, M., Coppola, G., Galdi, V., & Cusano, A. (2017). A study of Bloch-surface-wave sensing platforms for lab-on-fiber technology. In Proc. 7th EOS Topical Meeting on Optical Microsystems (OMS’17). Capri, Italy, Sep. 10-14, 2017.
@inproceedings{Scaravilli_OMS_2017,
author = {Scaravilli, Michele and Micco, Alberto and Castaldi, Giuseppe and Gioffr\e, Mariano and Coppola, Giuseppe and Galdi, Vincenzo and Cusano, Andrea},
title = {A study of Bloch-surface-wave sensing platforms for lab-on-fiber technology},
booktitle = {Proc. 7th EOS Topical Meeting on Optical Microsystems (OMS'17)},
organization = {Capri, Italy, Sep. 10-14, 2017},
year = {2017},
month = sep
}

2. Moccia, M., Castaldi, G., Galdi, V., Liu, S., Wu, R. Y., Cui, T. J., … Andreone, A. (2017). Coding THz metasurfaces with sub-optimal design for diffuse scattering . In Proc. 3rd EOS Topical Meeting on Optics at the Nanoscale (ONS’17). Capri, Italy, Sep. 10-14, 2017.
@inproceedings{Moccia_ONS_2017,
author = {Moccia, M. and Castaldi, G. and Galdi, V. and Liu, S. and Wu, R. Y. and Cui, T. J. and Koral, C. and Papari, G. P. and Andreone, A.},
title = {Coding THz metasurfaces with sub-optimal design for diffuse scattering },
booktitle = {Proc. 3rd EOS Topical Meeting on Optics at the Nanoscale (ONS'17)},
organization = {Capri, Italy, Sep. 10-14, 2017},
year = {2017},
month = sep
}

30 Aug 2017

We have presented an invited talk [1] at the 11th International Congress on Engineered Material Platforms for Novel Wave Phenomena (Metamaterials), Marseille, France, Aug. 28-31, 2017.

1. Galdi, V. (2017). Metasurfaces for field manipulation and sensing. In Proc. International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS) (pp. 112–114). Marseille, France, Aug. 28-31, 2017.
@inproceedings{Galdi_2017-Metamaterials,
author = {Galdi, Vincenzo},
booktitle = {Proc. International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS)},
title = {Metasurfaces for field manipulation and sensing},
year = {2017},
organization = {Marseille, France, Aug. 28-31, 2017},
doi = {10.1109/MetaMaterials.2017.8107857},
page = {112-114},
month = aug
}

Our paper on “Enhancement and interplay of first- and second-order spatial dispersion in metamaterials with moderate-permittivity inclusions” [1] in collaboration with Carlo Rizza (University of l’Aquila) and Alessandro Ciattoni (CNR-SPIN), has been published in Physical Review B as a Rapid Communication.

1. Rizza, C., Galdi, V., & Ciattoni, A. (2017). Enhancement and interplay of first- and second-order spatial dispersion in metamaterials with moderate-permittivity inclusions. Physical Review B 96(8), 081113.

We investigate a class of multilayered metamaterials characterized by moderate-permittivity inclusions and low average permittivity. Via first-principles calculations, we show that in such a scenario, first- and second-order spatial dispersions may exhibit a dramatic and nonresonant enhancement, and may become comparable with the local response. Their interplay gives access to a wealth of dispersion regimes encompassing additional extraordinary waves and topological phase transitions. In particular, we identify a configuration featuring bound and disconnected isofrequency contours. Since they do not rely on high-permittivity inclusions, our proposed metamaterials may constitute an attractive and technologically viable platform for engineering nonlocal effects in the optical range.

@article{IJ128_PRB_96_081113_2017,
title = {Enhancement and interplay of first- and second-order spatial dispersion in metamaterials with moderate-permittivity inclusions},
author = {Rizza, Carlo and Galdi, Vincenzo and Ciattoni, Alessandro},
journal = {Physical Review B},
volume = {96},
issue = {8},
pages = {081113},
numpages = {5},
year = {2017},
month = aug,
publisher = {American Physical Society},
doi = {10.1103/PhysRevB.96.081113},
}

Our paper on “Enhancement and interplay of first- and second-order spatial dispersion in metamaterials with moderate-permittivity inclusions,” in collaboration with Carlo Rizza (University of l’Aquila) and Alessandro Ciattoni (CNR-SPIN), has been accepted for publication as a Rapid Communication in Physical Review B.

An arXiv preprint is available.

Our paper on “Coding metasurfaces for diffuse scattering: Scaling laws, bounds, and sub-optimal design” [1], in collaboration with Tie Jun Cui’s Group (Southeast University), has been published (early view) in Advanced Optical Materials.

1. Moccia, M., Liu, S., Wu, R. Y., Castaldi, G., Andreone, A., Cui, T. J., & Galdi, V. (2017). Coding metasurfaces for diffuse scattering: Scaling laws, bounds, and suboptimal design. Advanced Optical Materials 5(19), 1700455.

Coding metasurfaces, based on the combination of two basic unit cells with out-of-phase responses, have been the subject of many recent studies aimed at achieving diffuse scattering, with potential applications to diverse fields ranging from radar-signature control to computational imaging. Here, via a theoretical study of the relevant scaling-laws, the physical mechanism underlying the scattering-signature reduction is elucidated, and some absolute and realistic bounds are analytically derived. Moreover, a simple, deterministic suboptimal design strategy is introduced that yields results comparable with those typically obtained by approaches based on brute-force numerical optimization, at a negligible fraction of their computational burden, thereby paving the way to the design of structures with arbitrarily large electrical size. Results are corroborated by rigorous full-wave numerical simulations and microwave experiments, and may be of interest in a variety of application fields, such as the design of low-scattering targets and illumination apertures for computational imaging, not necessarily restricted to electromagnetic scenarios.

author = {Moccia, Massimo and Liu, Shuo and Wu, Rui Yuan and Castaldi, Giuseppe and Andreone, Antonello and Cui, Tie Jun and Galdi, Vincenzo},
title = {Coding metasurfaces for diffuse scattering: Scaling laws, bounds, and suboptimal design},
issn = {2195-1071},
year = {2017},
volume = {5},
issue = {19},
month = oct,
pages = {1700455},
}

14 Jul 2017

We have presented two talks [1, 2] at the IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (IEEE-APS/URSI), San Diego, California, USA, July 9-14, 2017.

1. Moccia, M., Liu, S., Wu, R. Y., Castaldi, G., Andreone, A., Cui, T. J., & Galdi, V. (2017). Coding metasurfaces for diffuse scattering: Theoretical bounds and sub-optimal design. In Proc. USNC-URSI Radio Science Meeting. San Diego, CA, USA, July 9-14, 2017.
@inproceedings{Moccia_2017-USNC-URSI,
author = {Moccia, Massimo and Liu, Shuo and Wu, Rui Yuan and Castaldi, Giuseppe and Andreone, Antonello and Cui, Tie Jun and Galdi, Vincenzo},
booktitle = {Proc. USNC-URSI Radio Science Meeting},
title = {Coding metasurfaces for diffuse scattering: Theoretical bounds and sub-optimal design},
year = {2017},
organization = {San Diego, CA, USA, July 9-14, 2017},
month = jul
}

2. Principe, M., Consales, M., Micco, A., Crescitelli, A., Castaldi, G., Esposito, E., … Cusano, A. (2017). Fiber-optics meta-tips for light manipulation and sensing. In Proc. USNC-URSI Radio Science Meeting. San Diego, CA, USA, July 9-14, 2017.
@inproceedings{Principe_2017-USNC-URSI,
author = {Principe, M. and Consales, M. and Micco, A. and Crescitelli, A. and Castaldi, G. and Esposito, E. and La Ferrara, V. and Cutolo, A. and Galdi, V. and Cusano, A.},
booktitle = {Proc. USNC-URSI Radio Science Meeting},
title = {Fiber-optics meta-tips for light manipulation and sensing},
year = {2017},
organization = {San Diego, CA, USA, July 9-14, 2017},
month = jul
}

Our paper on “Coding metasurfaces for diffuse scattering: Scaling laws, bounds, and sub-optimal design,” in collaboration with Tie Jun Cui’s Group (Southeast University), has been accepted for publication in Advanced Optical Materials.

Our paper on “Transformation-optics-based design of a metamaterial radome for extending the scanning angle of a phased array antenna” [1], in collaboration with MBDA, has been published (early view) in the IEEE Journal of Multiscale and Multiphysics Computational Techniques.

1. Moccia, M., Castaldi, G., D’Alterio, G., Feo, M., Vitiello, R., & Galdi, V. (2017). Transformation-optics-based design of a metamaterial radome for extending the scanning angle of a phased array antenna. IEEE Journal on Multiscale and Multiphysics Computational Techniques 2, 159–167.

We apply the transformation-optics approach to the design of a metamaterial radome that can extend the scanning angle of a phased-array antenna. For moderate enhancement of the scanning angle, via suitable parameterization and optimization of the coordinate transformation, we obtain a design that admits a technologically viable, robust and potentially broadband implementation in terms of thin-metallic-plate inclusions. Our results, validated via finite-element-based numerical simulations, indicate an alternative route to the design of metamaterial radomes which does not require negative-valued and/or extreme constitutive parameters.

@article{IJ126_IEEE-JMMCT_2017,
author = {Moccia, M. and Castaldi, G. and D'Alterio, G. and Feo, M. and Vitiello, R. and Galdi, V.},
journal = {IEEE Journal on Multiscale and Multiphysics Computational Techniques},
title = {Transformation-optics-based design of a metamaterial radome for extending the scanning angle of a phased array antenna},
year = {2017},
doi = {10.1109/JMMCT.2017.2713826},
volume = {2},
number = {},
pages = {159--167},
month = {}
}

Our paper on “Transformation-optics-based design of a metamaterial radome for extending the scanning angle of a phased array antenna,” in collaboration with MBDA, has been accepted for publication in the IEEE Journal of Multiscale and Multiphysics Computational Techniques.

An arXiv preprint is available.

28 Apr 2017

We have presented a talk [1] at the 25th Optical Fiber Sensors Conference (OFS), Jeju, Korea, Apr. 24-28, 2017.

1. Principe, M., Consales, M., Micco, A., Crescitelli, A., Castaldi, G., Esposito, E., … Cusano, A. (2017). Optical fiber meta-tips: Perspectives in sensing applications. In Y. Chung, W. Jin, B. Lee, J. Canning, K. Nakamura, & L. Yuan (Eds.), Proceedings of SPIE (Vol. 10323, p. 103233F). 25th Optical Fiber Sensors Conference (OFS), Jeju, Korea, Apr. 24-28, 2017.
@inproceedings{Principe_2017-OFS,
author = {Principe, M. and Consales, M. and Micco, A. and Crescitelli, A. and Castaldi, G. and Esposito, E. and Ferrara, V. L. and Cutolo, A. and Galdi, V. and Cusano, A.},
editor = {Chung, Youngjoo and Jin, Wei and Lee, Byoungho and Canning, John and Nakamura, Kentaro and Yuan, Libo},
booktitle = {Proceedings of SPIE},
title = {Optical fiber meta-tips: Perspectives in sensing applications},
year = {2017},
volume = {10323},
pages = {103233F},
doi = {10.1117/12.2265002},
month = apr,
organization = {25th Optical Fiber Sensors Conference (OFS), Jeju, Korea, Apr. 24-28, 2017}
}

Our paper on “Exceptional points of degeneracy and PT-symmetry in photonic coupled chains of scatterers” [1] in collaboration with Filippo Capolino’s Group (University of California at Irvine), has been accepted for publication in Physical Review B.

1. Othman, M. A. K., Galdi, V., & Capolino, F. (2017). Exceptional points of degeneracy and PT symmetry in photonic coupled chains of scatterers. Physical Review B 95(10), 104305.

We demonstrate the existence of exceptional points of degeneracy (EPDs) of periodic eigenstates in non-Hermitian coupled chains of dipolar scatterers. Guided modes supported by these structures can exhibit an EPD in their dispersion diagram at which two or more Bloch eigenstates coalesce, in both their eigenvectors and eigenvalues. We show the emergence of a second-order modal EPD associated with the parity-time (PT) symmetry condition, at which each particle pair in the double chain exhibits balanced gain and loss. Furthermore, we also demonstrate a fourth-order EPD occurring at the band edge. Such a degeneracy condition was previously referred to as a degenerate band edge in lossless anisotropic photonic crystals. Here, we rigorously show it under the occurrence of gain and loss balance for a discrete guiding system. We identify a more general regime of gain and loss balance showing that PT symmetry is not necessary to attain EPDs. Moreover, we investigate the degree of detuning of the EPD when the geometrical symmetry or balanced condition is broken. Furthermore, we demonstrate a realistic implementation of the EPD in a coupled chain made of pairs of plasmonic nanospheres and active core-shell nanospheres at optical frequencies. These findings open avenues toward superior light localization and transport with application to high-Q resonators utilized in sensors, filters, low-threshold switching and lasing.

@article{IJ125_PRB_95_104305_2017,
title = {Exceptional points of degeneracy and PT symmetry in photonic coupled chains of scatterers},
author = {Othman, Mohamed A. K. and Galdi, Vincenzo and Capolino, Filippo},
journal = {Physical Review B},
volume = {95},
issue = {10},
pages = {104305},
numpages = {12},
year = {2017},
month = mar,
publisher = {American Physical Society},
doi = {10.1103/PhysRevB.95.104305},
}

Our paper on “Optical fiber meta-tips” [1], in collaboration with Andrea Cusano’s Group (University of Sannio), has been published in Light: Science & Applications.

1. Principe, M., Consales, M., Micco, A., Crescitelli, A., Castaldi, G., Esposito, E., … Cusano, A. (2017). Optical fiber meta-tips. Light: Science & Applications 6, e16226.

We report on the first demonstration of a proof-of-principle optical fiber ‘meta-tip’, which integrates a phase-gradient plasmonic metasurface on the fiber tip. For illustration and validation purposes, we present numerical and experimental results pertaining to various prototypes implementing generalized forms of the Snell’s transmission/reflection laws at near-infrared wavelengths. In particular, we demonstrate several examples of beam steering and coupling with surface waves, in fairly good agreement with theory. Our results constitute a first step toward the integration of unprecedented (metasurface-enabled) light-manipulation capabilities in optical-fiber technology. By further enriching the emergent ‘lab-on-fiber’ framework, this may pave the way for the widespread diffusion of optical metasurfaces in real-world applications to communications, signal processing, imaging and sensing.

@article{IJ124_LSA_6_6226a_2017,
author = {Principe, Maria and Consales, Marco and Micco, Alberto and Crescitelli, Alessio and Castaldi, Giuseppe and Esposito, Emanuela and La Ferrara, Vera and Cutolo, Antonello and Galdi, Vincenzo and Cusano, Andrea},
title = {Optical fiber meta-tips},
journal = {Light: Science {\&} Applications},
volume = {6},
pages = {e16226},
year = {2017},
month = mar,
doi = {10.1038/lsa.2016.226},
note = {http://www.nature.com/lsa/journal/v6/n3/suppinfo/lsa2016226s1.html?url=/lsa/journal/v6/n3/full/lsa2016226a.html}
}

Our paper on “Magnified imaging based on non-Hermitian nonlocal cylindrical metasurfaces” [1], in collaboration with Andrea Alù’s Group (University of Texas at Austin), has been published in Physical Review B.

1. Savoia, S., Valagiannopoulos, C. A., Monticone, F., Castaldi, G., Galdi, V., & Alù, A. (2017). Magnified imaging based on non-Hermitian nonlocal cylindrical metasurfaces. Physical Review B 95(11), 115114.

We show that a cylindrical lensing system composed of two metasurfaces with suitably tailored non-Hermitian (i.e., with distributed gain and loss) and nonlocal (i.e., spatially dispersive) properties can perform magnified imaging with reduced aberrations. More specifically, we analytically derive the idealized surface-impedance values that are required for “perfect” magnification and imaging and elucidate the role and implications of non-Hermiticity and nonlocality in terms of spatial resolution and practical implementation. For a basic demonstration, we explore some proof-of-principle quasilocal and multilayered implementations and independently validate the outcomes via full-wave numerical simulations. We also show that the metasurface frequency-dispersion laws can be chosen so as to ensure unconditional stability with respect to arbitrary temporal excitations. These results, which extend previous studies on planar configurations, may open intriguing venues in the design of metastructures for field imaging and processing.

@article{IJ123_PRB_95_115114_2017,
title = {Magnified imaging based on non-Hermitian nonlocal cylindrical metasurfaces},
author = {Savoia, Silvio and Valagiannopoulos, Constantinos A. and Monticone, Francesco and Castaldi, Giuseppe and Galdi, Vincenzo and Al\`u, Andrea},
journal = {Physical Review B},
volume = {95},
issue = {11},
pages = {115114},
numpages = {13},
year = {2017},
month = mar,
publisher = {American Physical Society},
doi = {10.1103/PhysRevB.95.115114}
}

Our paper on “Magnified imaging based on non-Hermitian nonlocal cylindrical metasurfaces,” in collaboration with Andrea Alù’s Group (University of Texas at Austin), has been accepted for publication in Physical Review B.

An arXiv preprint is available.

Our paper on “Exceptional points of degeneracy and PT-symmetry in photonic coupled chains of scatterers,” in collaboration with Filippo Capolino’s Group (University of California at Irvine), has been accepted for publication in Physical Review B.

An arXiv preprint is available.

9 Feb 2017

The new website is on!

Details on the design and implementation can be found here.