Riccardo Sapienza

Author(s): Arkadiusz Kosior and Krzysztof Sacha

Localization and transport of a quantum particle in fractal lattices with random-site connectivity and without any diagonal disorder are investigated. It is the random hopping terms that introduce disorder-causing localization of a single-particle wave function. The lattices are generated so that their fractal (Hausdorff and spectral) dimensions are independently controlled. Therefore, it is possible to analyze how different fractal dimensions influence the localization properties, which is the main purpose of this paper.

[Phys. Rev. B 95, 104206] Published Mon Mar 27, 2017

Author(s): Anatoly A. Svidzinsky, Fu Li, and Xiwen Zhang

We show that steady nonuniform motion of a medium through an optical resonator can yield light amplification at the resonator frequency. High gain can be achieved if at the generated frequency the medium refractive index is close to zero or the medium has a very strong frequency dispersion. We also ...

[Phys. Rev. Lett. 118, 123902] Published Thu Mar 23, 2017

Predatory journals recruit fake editor

Nature 543, 7646 (2017). doi:10.1038/543481a

Authors: Piotr Sorokowski, Emanuel Kulczycki, Agnieszka Sorokowska & Katarzyna Pisanski

An investigation finds that dozens of academic titles offered 'Dr Fraud' — a sham, unqualified scientist — a place on their editorial board. Katarzyna Pisanski and colleagues report.

Author(s): Stefano Lepri, Cosimo Trono, and Giovanni Giacomelli

Complex optical networks containing one or more gain sections are investigated, and the evidence of lasing action is reported; the emission spectrum reflects the topological disorder induced by the connections. A theoretical description compares well with the measurements, mapping the networks to di...

[Phys. Rev. Lett. 118, 123901] Published Tue Mar 21, 2017

Rémi Faggiani, Jianji Yang, Richard Hostein, Philippe Lalanne
One-dimensional (1D) infinite periodic systems exhibit vanishing group velocity and diverging density of states (DOS) near band edges. However, in practice, systems have finite sizes, and inevitably, this prompts the question of whether helpful physical quantities related to infinite systems, such ... [Optica 4, 393-399 (2017)]

High-resolution non-destructive three-dimensional imaging of integrated circuits

Nature 543, 7645 (2017). doi:10.1038/nature21698

Authors: Mirko Holler, Manuel Guizar-Sicairos, Esther H. R. Tsai, Roberto Dinapoli, Elisabeth Müller, Oliver Bunk, Jörg Raabe & Gabriel Aeppli

Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. This metrology gap implies a lack of direct feedback between design and manufacturing processes, and hampers quality control during production, shipment and use. Here we demonstrate that X-ray ptychography—a high-resolution coherent diffractive imaging technique—can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resolution in all directions down to 14.6 nanometres. We obtained detailed device geometries and corresponding elemental maps, and show how the devices are integrated with each other to form the chip. Our experiments represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques. Foreseeable developments in X-ray sources, optics and detectors, as well as adoption of an instrument geometry optimized for planar rather than cylindrical samples, could lead to a thousand-fold increase in efficiency, with concomitant reductions in scan times and voxel sizes.

Author(s): J. P. Balthasar Mueller, Noah A. Rubin, Robert C. Devlin, Benedikt Groever, and Federico Capasso

We present a method allowing for the imposition of two independent and arbitrary phase profiles on any pair of orthogonal states of polarization—linear, circular, or elliptical—relying only on simple, linearly birefringent wave plate elements arranged into metasurfaces. This stands in contrast to pr...

[Phys. Rev. Lett. 118, 113901] Published Tue Mar 14, 2017

Researchers should reach beyond the science bubble

Nature 542, 7642 (2017). doi:10.1038/542391a

Scientists in the United States and elsewhere ought to address the needs and employment prospects of taxpayers who have seen little benefit from scientific advances.

Static non-reciprocity in mechanical metamaterials

Nature 542, 7642 (2017). doi:10.1038/nature21044

Authors: Corentin Coulais, Dimitrios Sounas & Andrea Alù

Reciprocity is a general, fundamental principle governing various physical systems, which ensures that the transfer function—the transmission of a physical quantity, say light intensity—between any two points in space is identical, regardless of geometrical or material asymmetries. Breaking this transmission symmetry offers enhanced control over signal transport, isolation and source protection. So far, devices that break reciprocity (and therefore show non-reciprocity) have been mostly considered in dynamic systems involving electromagnetic, acoustic and mechanical wave propagation associated with fields varying in space and time. Here we show that it is possible to break reciprocity in static systems, realizing mechanical metamaterials that exhibit vastly different output displacements under excitation from different sides, as well as one-way displacement amplification. This is achieved by combining large nonlinearities with suitable geometrical asymmetries and/or topological features. In addition to extending non-reciprocity and isolation to statics, our work sheds light on energy propagation in nonlinear materials with asymmetric crystalline structures and topological properties. We anticipate that breaking reciprocity will open avenues for energy absorption, conversion and harvesting, soft robotics, prosthetics and optomechanics.

Nicolas Muller, Jakub Haberko, Catherine Marichy, Frank Scheffold
Hyperuniform disordered networks belong to a peculiar class of structured materials predicted to display isotropic complete photonic bandgaps for a refractive index contrast larger than 3. The practical realization of such photonic designer materials is challenging, however, as it requires control ... [Optica 4, 361-366 (2017)]

Author(s): Martin Berthel, Quanbo Jiang, Aline Pham, Joel Bellessa, Cyriaque Genet, Serge Huant, and Aurélien Drezet

Surface plasmons (SPs) are key excitations for manipulating light in two dimensions, as in integrated optical circuits on chips. Here the authors show how to filter, in selected directions, the signal due to SP motion in a collimating device. Considering both the classical and quantum optical regimes, they interpret their findings in terms of a propagative electromagnetic local density of states. This approach could also be used in other quantum-technology contexts, e.g. to optimize the coupling efficiency of quantum emitters.

[Phys. Rev. Applied 7, 014021] Published Fri Jan 27, 2017

A new technique slows down light in a crystal by simply shining a laser on it and varying an applied voltage.

[Physics] Published Tue Mar 07, 2017

Author(s): M. Jang, C. Yang, and I. M. Vellekoop

When a beam of light is sent through a nearly opaque material, the scattered light that emerges can be unscrambled even with few photons detected.

[Phys. Rev. Lett. 118, 093902] Published Fri Mar 03, 2017

A common quote about history is that "History is written by the victors". The over-simplified point is that sometimes the losers of a war are obliterated (or at least lose power) and so don't have the opportunity to tell their side of the story. In contrast, the victors want to propagate a one-sided story about their heroic win over their immoral adversaries. The origin of this quote is debatable but there is certainly a nice article where George Orwell discusses the problem in the context of World War II.

What does this have to do with teaching science?
The problem is that textbooks present nice clean discussions of successful theories and models that rarely engage with the complex and tortuous path that was taken to get to the final version.
If the goal is "efficient" learning and minimisation of confusion this is appropriate.
However, we should ask whether this is the best way for students to actually learn how to DO and understand science.

I have been thinking about this because this week I am teaching the Drude model in my solid state physics course. Because of its simplicity and success, it is an amazing and beautiful theory. But, it is worth thinking about two key steps in constructing the model; steps that are common (and highly non-trivial) in constructing any theoretical model in science.

1. Deciding which experimental observables and results one wants to describe.

2. Deciding which parameters or properties will be ingredients of the model.

For 1. it is Ohm's law, Fourier's law, Hall effect, Drude peak, UV transparency of metals, Weidemann-Franz, magnetoresistance, thermoelectric effect, specific heat, ...

For 2. one starts with only conduction electrons (not valence electrons or ions), no crystal structure or chemical detail (except valence), and focuses on averages (velocity, scattering time, density) rather than standard deviations, ...

In hindsight, it is all "obvious" and "reasonable" but spare a thought for Drude in 1900. It was only 3 years after the discovery of the electron, before people were even certain that atoms existed, and certainly before the Bohr model...

This issue is worth thinking about as we struggle to describe and understand complex systems such as society, the economy, or biological networks. One can nicely see 1. and 2. above in a modest and helpful article by William Bialek, Perspectives on theory at the interface of physics and biology.

Our visual perception of our surroundings is ultimately limited by the diffraction limit, which stipulates that optical information smaller than roughly half the illumination wavelength is not retrievable. Over the past decades, many breakthroughs have led to unprecedented imaging capabilities beyond the diffraction-limit, with applications in biology and nanotechnology. In this context, nano-photonics has revolutionized the field of optics in recent years by enabling the manipulation of light-matter interaction with subwavelength structures. However, despite the many advances in this field, its impact and penetration in our daily life has been hindered by a convoluted and iterative process, cycling through modeling, nanofabrication and nano-characterization. The fundamental reason is the fact that not only the prediction of the optical response is very time consuming and requires solving Maxwell's equations with dedicated numerical packages. But, more significantly, the inverse problem, i.e. designing a nanostructure with an on-demand optical response, is currently a prohibitive task even with the most advanced numerical tools due to the high non-linearity of the problem. Here, we harness the power of Deep Learning, a new path in modern machine learning, and show its ability to predict the geometry of nanostructures based solely on their far-field response. This approach also addresses in a direct way the currently inaccessible inverse problem breaking the ground for on-demand design of optical response with applications such as sensing, imaging and also for plasmon's mediated cancer thermotherapy.

Zihe Gao, Stewart T. M. Fryslie, Bradley J. Thompson, P. Scott Carney, Kent D. Choquette
We report parity-time (PT) symmetry breaking in electrically injected, coherently coupled, vertical cavity surface emitting laser arrays. We predict beam steering, mode evolution, and mode hopping as consequences of the non-Hermiticity of the array, analyzed by the temporal coupled-mode theory with ... [Optica 4, 323-329 (2017)]

Author(s): Nicolas Tancogne-Dejean, Oliver D. Mücke, Franz X. Kärtner, and Angel Rubio

Advanced first-principles calculations reveal that the generation of high harmonic spectra is enhanced by the inhomogeneity of the electron­-nuclei potential, which is obtained from the band structure.

[Phys. Rev. Lett. 118, 087403] Published Fri Feb 24, 2017

Author(s): L. Keiser, H. Bense, P. Colinet, J. Bico, and E. Reyssat

A drop of water-alcohol mixture on a layer of oil was caught on video bursting into thousands of tiny droplets.

[Phys. Rev. Lett. 118, 074504] Published Fri Feb 17, 2017

Title: Anderson Transition for Classical Transport in Composite Materials
Author(s): Murphy, N. Benjamin; Cherkaev, Elena; Golden, Kenneth M.
Source: PHYSICAL REVIEW LETTERS, 118 (3): JAN 19 2017
Document Type: Article

Author(s): Sotiris Droulias, Aditya Jain, Thomas Koschny, and Costas M. Soukoulis

The route to miniaturization of laser systems has so far led to the utilization of diverse materials and techniques for reaching the desired laser oscillation at small scales. Unfortunately, at some point all approaches encounter a trade-off between the system dimensions and the Q factor, especially...

[Phys. Rev. Lett. 118, 073901] Published Fri Feb 17, 2017