Shared posts

17 Oct 02:22

High-speed colour-converting photodetector with all-inorganic CsPbBr3 perovskite nanocrystals for ultraviolet light communication

by Chun Hong Kang

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.
17 Jan 16:17

Nonreciprocal cavities and the time–bandwidth limit

by Sander A. Mann
Sander A. Mann, Dimitrios L. Sounas, Andrea Alù
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)]
23 Apr 12:59

Nonreciprocal Cavities and the Time-Bandwidth Limit. (arXiv:1804.07420v1 [physics.optics])

by Sander A. Mann, Dimitrios L. Sounas, Andrea Alù

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.

09 Oct 19:56

Ising Superconductivity and Quantum Phase Transition in Macro-Size Monolayer NbSe2

by Ying Xing, Kun Zhao, Pujia Shan, Feipeng Zheng, Yangwei Zhang, Hailong Fu, Yi Liu, Mingliang Tian, Chuanying Xi, Haiwen Liu, Ji Feng, Xi Lin, Shuaihua Ji, Xi Chen, Qi-Kun Xue and Jian Wang

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.7b03026
29 Mar 13:45

Light-by-Light Scattering Constraint on Born-Infeld Theory. (arXiv:1703.08450v2 [hep-ph] UPDATED)

by John Ellis, Nick E. Mavromatos, Tevong You

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.

23 Mar 08:51

Leveraging Superchiral Light for Manipulation of Optical Chirality in the Near-Field of Plasmonic Metamaterials

by Lei Kang, Qiang Ren and Douglas H. Werner
Sandermann

hehehe

TOC Graphic

ACS Photonics
DOI: 10.1021/acsphotonics.7b00057
22 Jan 12:45

Childhood careers are overrated.

by engrishwebmaster

everthing-is-in-vented

Photo courtesy of D.T.
Found in Phuket, Thailand.

20 Oct 07:34

Signifying the nonlocality of NOON states using Einstein-Podolsky-Rosen steering inequalities

by R. Y. Teh, L. Rosales-Zárate, B. Opanchuk, and M. D. Reid

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

12 Sep 20:13

Quantifying losses and thermodynamic limits in nanophotonic solar cells

by Sander A. Mann

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).

26 Aug 19:40

Science in the age of selfies [Physics]

by Geman, D., Geman, S.
A time traveler from 1915 arriving in 1965 would have been astonished by the scientific theories and engineering technologies invented during that half century. One can only speculate, but it seems likely that few of the major advances that emerged during those 50 years were even remotely foreseeable in 1915:...
05 Jul 15:03

Ruff way to go

by admin

25 May 07:18

Killer Asteroids

by woit

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.

24 May 16:56

Generalized antireflection coatings for complex bulk metamaterials

by Ruben Maas, Sander A. Mann, Dimitrios L. Sounas, Andrea Alù, Erik C. Garnett, and Albert Polman

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

11 Apr 19:43

Wait, what?

by admin

via reddit

07 Apr 11:26

Damn kids…

by engrishwebmaster

kids-sucks

Photo courtesy of Thochen.
Found in Taipei, Taiwan.
Should be “kids socks”.

14 Mar 13:16

Doomsday Clock

After a power outage at the Bulletin of the Atomic Scientists, the new Digital Doomsday Clock is flashing 00:00 and mushroom clouds keep appearing and then retracting once a second.
04 Feb 22:39

[In Depth] Calling all failed replication experiments

by Jocelyn Kaiser
A growing number of retracted papers have stirred concerns about irreproducible results in biomedical research. Now, the biotech company Amgen and prominent biochemist Bruce Alberts have created a new online journal that aims to lift the curtain on often-hidden data: failed efforts to confirm other groups' published papers. Amgen is seeding the publication with reports on its own futile attempts to replicate three studies in obesity and neurodegenerative disease and hopes other companies will follow suit. The contradictory results—along with successful confirmations—will be published by F1000Research, an open-access, online-only publisher. Its new Preclinical Reproducibility and Robustness channel, launched on 4 February, will allow both companies and academic scientists to share their replications so that others will be less likely to waste time following up on flawed findings. Author: Jocelyn Kaiser
09 Dec 14:46

Don’t bother washing your hands

by engrishwebmaster

Mazda-Museum

Hon, did I already go?

Photo courtesy of Bernhard Wodok.
Found at Mazda Museum in Hiroshima, Japan.

06 Oct 11:57

This trash is sick!

by engrishwebmaster

no-killer-littering

Give a hoot…or you die.

Photo courtesy of Karuna Murdaya.
Found in Shenzhen, China.

02 Sep 11:14

Any place but here…

by engrishwebmaster

lifts-to-someplace-else

Don’t push the button marked ‘?’

Photo courtesy of Mahla, Caz, and Kenz.
Found in a hotel in Hong Kong. 

30 Aug 10:21

In Love

by admin

10 Aug 14:37

We are here! Right up these stairs…

by engrishwebmaster

NonstopIntercourse

Photo courtesy of Rick Kraus.
Spotted in Thailand (shirt from Indonesia).

17 Jul 07:41

A Day to Remember

by admin

07 Jul 14:49

Life x 1 + money =

by engrishwebmaster

Life_is_only_once

So make best and rich.

Photo courtesy of Mark Schreiber.
Billboard found above Shibuya station Tokyo.

03 Jul 07:25

Resonant Nanophotonic Spectrum Splitting for Ultrathin Multijunction Solar Cells

by Sander A. Mann and Erik C. Garnett

TOC Graphic

ACS Photonics
DOI: 10.1021/acsphotonics.5b00260
29 Jun 14:06

Arnie FTW!

by admin

28 Jun 08:49

Precious Moments

by admin

14 Jun 12:22

Comic for 2015.06.14

New Cyanide and Happiness Comic
29 May 07:50

The BDLPSWDKS Effect

This well-known effect has of course been replicated in countless experiments.
22 May 08:05

Vodka

Or whatever's handy! I'm pretty much pure alcohol and water, so it doesn't really matter!