Light: Science & Applications, Published online: 16 October 2019; doi:10.1038/s41377-019-0204-4
A silicon-based receiver that incorporates perovskite nanocrystals efficiently detects ultraviolet signals, paving the way towards high-speed, high-bandwidth UV wireless communication. The photodetector (PD), developed by Boon S. Ooi of King Abdullah University of Science and Technology (KAUST) and colleagues in Saudi Arabia, is less bulky and cheaper to manufacture than currently available receivers. It builds on technologically advanced silicon-based PDs, which are compact and widely available, but respond best to higher wavelength green light. Incorporating cesium lead bromide (CsPbBr3) perovskite nanocrystals into a silicon-based PD facilitated efficient conversion of UV into green light. The team demonstrated that their receiver could be used in high-speed UV-based communication, paving the way for the use of perovskite-based materials in terrestrial and underwater UV-Internet systems.Shared posts
High-speed colour-converting photodetector with all-inorganic CsPbBr3 perovskite nanocrystals for ultraviolet light communication
Nonreciprocal cavities and the time–bandwidth limit
The time–bandwidth limit inherently relates the lifetime of a resonance and its spectral bandwidth, with direct implications for the maximum storage time of a pulse versus its frequency content. Recently, it has been argued that nonreciprocal cavities may overcome this constraint by breaking ... [Optica 6, 104-110 (2019)]
Nonreciprocal Cavities and the Time-Bandwidth Limit. (arXiv:1804.07420v1 [physics.optics])
The time-bandwidth limit inherently relates the lifetime of a resonance and its spectral bandwidth, with direct implications on the maximum storage time of a pulse versus its frequency content. It has been recently argued that nonreciprocal cavities may overcome this constraint, by breaking the strict equality of their incoupling and outcoupling coefficients. Here, we generally study the implications of nonreciprocity on resonant cavities and derive general relations, stemming from microscopic reversibility, that govern their dynamics. We show that nonreciprocal cavities do not provide specific advantages in terms of the time-bandwidth limit, but they may have other attractive properties for nanophotonic systems.
Ising Superconductivity and Quantum Phase Transition in Macro-Size Monolayer NbSe2
Light-by-Light Scattering Constraint on Born-Infeld Theory. (arXiv:1703.08450v2 [hep-ph] UPDATED)
The recent measurement by ATLAS of light-by-light scattering in LHC Pb-Pb collisions is the first direct evidence for this basic process. We find that it requires the mass scale of a nonlinear Born-Infeld extension of QED to be $\gtrsim 100$~GeV, a much stronger constraint than those derived previously. In the case of a Born-Infeld extension of the Standard Model in which the U(1)$_{\rm Y}$ hypercharge gauge symmetry is realized nonlinearly, the limit on the corresponding mass scale is $\gtrsim 90$~GeV, which in turn imposes a lower limit of $\gtrsim 11$~TeV on the magnetic monopole mass in such a U(1)$_{\rm Y}$ Born-Infeld theory.
Leveraging Superchiral Light for Manipulation of Optical Chirality in the Near-Field of Plasmonic Metamaterials
Sandermannhehehe
Signifying the nonlocality of NOON states using Einstein-Podolsky-Rosen steering inequalities
Author(s): R. Y. Teh, L. Rosales-Zárate, B. Opanchuk, and M. D. Reid
We construct Einstein-Podolsky-Rosen (EPR) steering signatures for the nonlocality of the entangled superposition state described by 12{|N〉|0〉+|0〉|N〉}, called the two-mode NOON state. The signatures are a violation of an EPR steering inequality based on an uncertainty relation. The violation confirm…
[Phys. Rev. A 94, 042119] Published Wed Oct 19, 2016
Quantifying losses and thermodynamic limits in nanophotonic solar cells
Nature Nanotechnology. doi:10.1038/nnano.2016.162
Authors: Sander A. Mann, Sebastian Z. Oener, Alessandro Cavalli, Jos E. M. Haverkort, Erik P. A. M. Bakkers & Erik C. Garnett
Nanophotonic engineering shows great potential for photovoltaics: the record conversion efficiencies of nanowire solar cells are increasing rapidly and the record open-circuit voltages are becoming comparable to the records for planar equivalents. Furthermore, it has been suggested that certain nanophotonic effects can reduce costs and increase efficiencies with respect to planar solar cells. These effects are particularly pronounced in single-nanowire devices, where two out of the three dimensions are subwavelength. Single-nanowire devices thus provide an ideal platform to study how nanophotonics affects photovoltaics. However, for these devices the standard definition of power conversion efficiency no longer applies, because the nanowire can absorb light from an area much larger than its own size. Additionally, the thermodynamic limit on the photovoltage is unknown a priori and may be very different from that of a planar solar cell. This complicates the characterization and optimization of these devices. Here, we analyse an InP single-nanowire solar cell using intrinsic metrics to place its performance on an absolute thermodynamic scale and pinpoint performance loss mechanisms. To determine these metrics we have developed an integrating sphere microscopy set-up that enables simultaneous and spatially resolved quantitative absorption, internal quantum efficiency (IQE) and photoluminescence quantum yield (PLQY) measurements. For our record single-nanowire solar cell, we measure a photocurrent collection efficiency of >90% and an open-circuit voltage of 850 mV, which is 73% of the thermodynamic limit (1.16 V).
Science in the age of selfies [Physics]
Killer Asteroids
During my recent vacation I visited my old friend Nathan Myhrvold, and got a tour of his company’s lab near Bellevue. At that time he told me about what he had been working on recently, which has now appeared on the arXiv here, and is the subject of news stories today at the New York Times and Science magazine.
I confess I’ve never worried much about killer asteroids, but am glad that someone is doing this. Nathan has always pursued a wide range of different interests, and killer asteroids has evidently been one of them. I first heard from him a year or two ago about how he had gotten interested in the question of how to model the observability of such objects. Such modeling affects choices to be made about how to optimally search for these things (space-based or earth-based telescopes? what kind?). He wrote a paper last year about this, which was published in March.
What Nathan told me when I saw him was that he had found significant problems with the modeling done by the NEOWISE/WISE group at NASA, and you can now judge for yourself by reading his paper. I’m very far from being able to understand the details of this story well enough to judge who’s right here. I do know Nathan well enough to know that his work on this deserves to be taken very seriously, and would bet that he has identified real problems. As noted in the comments there, the reaction from one of the NASA WISE people quoted at the end of the Science article wasn’t exactly confidence inspiring.
Update: There’s a press release about this out from NASA today, pretty much devoted to attacking Nathan’s work.
Update: For some specific criticisms of Nathan’s work, see the comment thread here. For a response to some of this from Nathan, see here.
Update: Scientific American has an article about this here.
Update: As pointed out by Wayt Gibbs in a comment, those interested in some discussion of the main point at issue might want to read the exchange here.
Generalized antireflection coatings for complex bulk metamaterials
Author(s): Ruben Maas, Sander A. Mann, Dimitrios L. Sounas, Andrea Alù, Erik C. Garnett, and Albert Polman
We present the optimized design of an antireflection coating to efficiently couple an incident plane wave into a metamaterial with a complex field profile. We show that such an antireflection coating must enable spatial engineering of the field profiles at the coating/metamaterial interface to achie…
[Phys. Rev. B 93, 195433] Published Tue May 24, 2016