(Press-News.org) Topological transport of light is the photonic analog of topological electron flow in certain semiconductors. In the electron case, the current flows around the edge of the material but not through the bulk. It is "topological" in that even if electrons encounter impurities in the material the electrons will continue to flow without losing energy.
In the photonic equivalent, light flows not through and around a regular material but in a meta-material consisting of an array of tiny glass loops fabricated on a silicon substrate. If the loops are engineered just right, the topological feature appears: light sent into the array easily circulates around the edge with very little energy loss (even if some of the loops aren't working) while light taking an interior route suffers loss.
Mohammad Hafezi and his colleagues at the Joint Quantum Institute have published a series of papers on the subject of topological light. The first pointed out the potential application of robustness in delay lines and conceived a scheme to implement quantum Hall models in arrays of photonic loops. In photonics, signals sometimes need to be delayed, usually by sending light into a kilometers-long loop of optical fiber. In an on-chip scheme, such delays could be accomplished on the microscale; this is in addition to the energy-loss reduction made possible by topological robustness (1).
The next paper reported on results from an actual experiment. Since the tiny loops aren't perfect, they do allow a bit of light to escape vertically out of the plane of the array (2). This faint light allowed the JQI experimenters to image the course of light. This confirmed the plan that light persists when it goes around the edge of the array but suffers energy loss when traveling through the bulk.
The third paper, appearing now in Physical Review Letters, actually delivers detailed measurements of the transmission (how much energy is lost) and delay for edge-state light and for bulk-route light (3). The paper is notable enough to have received an "editor's suggestion" designation. "Apart from the potential photonic-chip applications of this scheme," said Hafezi, "this photonic platform could allow us to investigate fundamental quantum transport properties."
Another measured quality is consistency. Sunil Mittal, a graduate student at the University of Maryland and first author on the paper, points out that microchip manufacturing is not a perfect process. "Irregularities in integrated photonic device fabrication usually result in device-to-device performance variations," he said. And this usually undercuts the microchip performance. But with topological protection (photons traveling at the edge of the array are practically invulnerable to impurities) at work, consistency is greatly strengthened.
Indeed, the authors, reporting trials with numerous array samples, reveal that for light taking the bulk (interior) route in the array, the delay and transmission of light can vary a lot, whereas for light making the edge route, the amount of energy loss is regularly less and the time delay for signals more consistent. Robustness and consistency are vital if you want to integrate such arrays into photonic schemes for processing quantum information.
How does the topological property emerge at the microscopic level? First, look at the electron topological behavior, which is an offshoot of the quantum Hall effect. Electrons, under the influence of an applied magnetic field can execute tiny cyclonic orbits. In some materials, called topological insulators, no external magnetic field is needed since the necessary field is supplied by spin-orbit interactions---that is, the coupling between the orbital motion of electrons and their spins. In these materials the conduction regime is topological: the material is conductive around the edge but is an insulator in the interior.
And now for the photonic equivalent. Light waves do not usually feel magnetic fields, and if they do it is very weak. In the photonic case, the equivalent of a magnetic field is supplied by a subtle phase shift imposed on the light as it circulates around the loops. Actually the loops in the array are of two kinds: resonator loops designed to exactly accommodate light at a certain frequency, allowing the waves to circle the loop many times. Link loops, by contrast, are not exactly suited to the waves, and are designed chiefly to pass the light onto the neighboring resonator loop.
Light that circulates around one unit cell of the loop array will undergo a slight phase change, an amount signified by the letter phi. That is, the light signal, in coming around the unit cell, re-arrives where it started advanced or retarded just a bit from its original condition. Just this amount of change imparts the topological robustness to the global transmission of the light in the array.
In summary, documented on-chip light delay and a robust, consistent, low-loss transport of light has now been demonstrated. The transport of light is tunable to a range of frequencies and the chip can be manufactured using standard micro-fabrications techniques.
INFORMATION:
1. Concept for making on-chip delay lines: http://jqi.umd.edu/news/miniaturizing-delay-lines
2. Topological light observed in 2D arrays: http://jqi.umd.edu/news/topological-light
3. "Topologically Robust Transport of Photons in a Synthetic Gauge Field," S. Mittal, J. Fan, S. Faez, A. Migdall, J. M. Taylor, and M. Hafezi, Physical Review Letters, to be published in August 2014; archive version: http://arxiv.org/pdf/1404.0090v1.pdf
Mohammad Hafezi, Hafezi@umd.edu; Sunil Mittal, mittals@umd.edu
Press contact at JQI: Phillip F. Schewe, pschewe@umd.edu, 301-405-0989. http://jqi.umd.edu/
On-chip topological light
First measurements of transmission and delay
2014-08-01
ELSE PRESS RELEASES FROM THIS DATE:
Expressive writing may help breast cancer survivors
2014-08-01
Writing down fears, emotions and the benefits of a cancer diagnosis may improve health outcomes for Asian-American breast cancer survivors, according to a study conducted by a researcher at the University of Houston (UH).
"The key to developing an expressive writing intervention is the writing instruction. Otherwise, writing is just like a journal recording facts and events. Writing a journal can be therapeutic, but oftentimes we don't get the empirical evidence to determine whether it's effective or not," said Qian Lu, assistant professor and director of the Culture ...
Mapping the optimal route between two quantum states
2014-08-01
As a quantum state collapses from a quantum superposition to a classical state or a different superposition, it will follow a path known as a quantum trajectory. For each start and end state there is an optimal or "most likely" path, but it is not as easy to predict the path or track it experimentally as a straight-line between two points would be in our everyday, classical world.
In a new paper featured on the July 30 cover of Nature, scientists from the Institute for Quantum Studies at Chapman University, the University of Rochester, University of California at Berkeley, ...
Cordilleran terrane collage
2014-08-01
Boulder, Colo., USA - In the August 2014 issue of LITHOSPHERE, Steve Israel of the Yukon Geological Survey and colleagues provide conclusions regarding the North American Cordillera that they say "are provocative in that they blur the definition of tectonic terranes, showing that many observations of early geologists can be attributed to evolving geologic processes rather than disparate geologic histories."
Western North America is characterized by the Cordilleran accretionary mountain belt, which has seen episodic plate convergence since the early Paleozoic, about 253 ...
On-chipt topological light
2014-08-01
Topological transport of light is the photonic analog of topological electron flow in certain semiconductors. In the electron case, the current flows around the edge of the material but not through the bulk. It is "topological" in that even if electrons encounter impurities in the material the electrons will continue to flow without losing energy.
In the photonic equivalent, light flows not through and around a regular material but in a meta-material consisting of an array of tiny glass loops fabricated on a silicon substrate. If the loops are engineered just right, ...
Society bloomed with gentler personalities and more feminine faces
2014-08-01
DURHAM, N.C. -- Modern humans appear in the fossil record about 200,000 years ago, but it was only about 50,000 years ago that making art and advanced tools became widespread.
A new study appearing Aug. 1 in the journal Current Anthropology finds that human skulls changed in ways that indicate a lowering of testosterone levels at around the same time that culture was blossoming.
"The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament," said lead author ...
History of culture visualized through art history, physics, complexity
2014-08-01
Coral Gables, Fla. (July 31, 2014) -- Quantifying and transforming the history of culture into visual representation isn't easy. There are thousands of individual stories, across thousands of years, to consider, and some historical conditions are nearly impossible to measure.
Addressing this challenge, Dr. Maximilian Schich, associate professor of arts and technology at The University of Texas at Dallas, brought together a team of network and complexity scientists, including University of Miami physicist Chaoming Song, to create and quantify a big picture of European ...
'Normal' bacteria vital for keeping intestinal lining intact
2014-08-01
August 1, 2014 — (BRONX, NY) — Scientists at Albert Einstein College of Medicine of Yeshiva University have found that bacteria that aid in digestion help keep the intestinal lining intact. The findings, reported online in the journal Immunity, could yield new therapies for inflammatory bowel disease (IBD) and a wide range of other disorders.
The research involved the intestinal microbiome, which contains some 100 trillion bacteria. The role of these microorganisms in promoting or preventing disease is a major emerging field of study. Einstein scientists found that absorption ...
A train of 5 tropical cyclones in the Central and Eastern Pacific
2014-08-01
A train of developing tropical low pressure areas stretch from the Eastern Pacific Ocean into the Central Pacific and they were captured in an image from NOAA's GOES-West satellite on August 1. The train of five tropical lows include the remnants of Tropical Storm Genevieve and newly developed Tropical Storm Iselle.
NOAA's GOES-West satellite captured an image of the Pacific Ocean on August 1 at 1200 UTC (8 a.m. EDT) that showed post-tropical cyclone Genevieve's remnants between three other systems. The GOES-West image shows the train of storms with a well-developed Iselle ...
A map for eye disease
2014-08-01
Understanding eye diseases is tricky enough. Knowing what causes them at the molecular level is even more confounding.
Now, University of Iowa researchers have created the most detailed map to date of a region of the human eye long associated with blinding diseases, such as age-related macular degeneration. The high-resolution molecular map catalogs thousands of proteins in the choroid, which supplies blood and oxygen to the outer retina, itself critical in vision. By seeing differences in the abundance of proteins in different areas of the choroid, the researchers can ...
NASA finds heavy rainfall and wind shear in newborn Tropical Storm Bertha
2014-08-01
VIDEO:
This 3-D flyby of Tropical Storm Bertha on Aug. 1 was created from TRMM satellite data. It shows (from the south) intense thunderstorms were reaching heights of over 15km (about...
Click here for more information.
The Tropical Rainfall Measuring Mission satellite known as TRMM found rain was falling heavily in the Atlantic Ocean's second tropical storm of the hurricane season. Bertha was close to the Lesser Antilles, prompting warnings and watches.
The National Hurricane ...
LAST 30 PRESS RELEASES:
Frontiers and World Economic Forum unveil top technologies to accelerate global climate and planetary health solutions
‘How drunk do you feel?’: Ozempic, Wegovy may help reduce alcohol use, Virginia Tech researchers find
Divine punishment as an ancient tool for modern sustainability
Hotter does mean wetter
Internal migrants in the U.S. age with fewer disabilities, study finds
Anna Krylov and Mikhail Yampolsky are the new George Gamow award laureates
Methane from overlooked sources higher than predicted in Osaka
World’s largest rays may be diving to extreme depths to build mental maps of vast oceans
Can we hear gravitational-wave "beats" in the rhythm of pulsars?
New survey shows many are unaware of advancements in obstetrics care
New combination therapy shows promise for aggressive lymphoma resistant to immunotherapy
Photocatalytic olefin double bond cleavage acylation
Unveiling the impact of compound drought and wildfire events on PM2.5 air pollution in the era of climate change
A bioadhesive sponge inspired by mussels and extracellular matrix offers a new way to stop internal bleeding
Poorer health linked to more votes for Reform UK, 2024 voting patterns suggest
Loneliness and social isolation linked to heightened risk of death in those with cancer
Ditch ‘shrink it and pink it’ approach to women’s running shoes, manufacturers urged
Domestic abusers forge ‘trauma bonds’ with victims before violence begins
UK food needs radical transformation on scale not seen since Second World War, new report finds
New AI tool makes medical imaging process 90% more efficient
Nitrogen-fortified nanobiochar boosts soil health and rice productivity
Generative art enhances virtual shopping experience
Fluid-based laser scanning for brain imaging
Concordia study links urban heat in Montreal to unequal greenspace access
Hidden patterns link ribosomal RNAs to genes of the nervous system
Why does losing the Y chromosome make some cancers worse? New $6.5 million NIH grant could provide clues
Xiao receives David W. Robertson Award for Excellence in Medicinal Chemistry
Boron isotopes reveal how nuclear waste glass slowly dissolves over time
Biochar helps Mediterranean vineyards hold water and fight erosion
Checking the quality of materials just got easier with a new AI tool
[Press-News.org] On-chip topological lightFirst measurements of transmission and delay