This breakthrough, described in an advanced online publication of the journal Nature on Sunday, Aug. 30, breaks new ground in the field of optics. The UC Berkeley team not only successfully squeezed light into such a tight space, but found a novel way to keep that light energy from dissipating as it moved along, thereby achieving laser action.
"This work shatters traditional notions of laser limits, and makes a major advance toward applications in the biomedical, communications and computing fields," said Xiang Zhang, professor of mechanical engineering and director of UC Berkeley's Nanoscale Science and Engineering Center, which is funded by the National Science Foundation (NSF), and head of the research team behind this work.The achievement helps enable the development of such innovations as nanolasers that can probe, manipulate and characterize DNA molecules; optics-based telecommunications many times faster than current technology; and optical computing in which light replaces electronic circuitry with a corresponding leap in speed and processing power.
Scientists have been racing to construct surface plasmon lasers that can sustain and utilize these tiny optical excitations. However, the resistance inherent in metals causes these surface plasmons to dissipate almost immediately after being generated, posing a critical challenge to achieving the buildup of the electromagnetic field necessary for lasing.
Zhang and his research team took a novel approach to stem the loss of light energy by pairing a cadmium sulfide nanowire - 1,000 times thinner than a human hair - with a silver surface separated by an insulating gap of only 5 nanometers, the size of a single protein molecule. In this structure, the gap region stores light within an area 20 times smaller than its wavelength. Because light energy is largely stored in this tiny non-metallic gap, loss is significantly diminished.
With the loss finally under control through this unique "hybrid" design, the researchers could then work on amplifying the light.
"When you are working at such small scales, you do not have much space to play around with," said Rupert Oulton, the research associate in Zhang's lab who first theorized this approach last year and the study's co-lead author. "In our design, the nanowire acts as both a confinement mechanism and an amplifier. It's pulling double duty."
Trapping and sustaining light in radically tight quarters creates such extreme conditions that the very interaction of light and matter is strongly altered, the study authors explained. An increase in the spontaneous emission rate of light is a telltale sign of this altered interaction; in this study, the researchers measured a six-fold increase in the spontaneous emission rate of light in a gap size of 5 nanometers.
Recently, researchers from Norfolk State University reported lasing action of gold spheres in a dye-filled, glasslike shell immersed in a solution. The dye coupled to the gold spheres could generate surface plasmons when exposed to light.
The UC Berkeley researchers used semiconductor materials and fabrication technologies that are commonly employed in modern electronics manufacturing. By engineering hybrid surface plasmons in the tiny gap between semiconductors and metals, they were able to sustain the strongly confined light long enough that its oscillations stabilized into the coherent state that is a key characteristic of a laser.
"What is particularly exciting about the plasmonic lasers we demonstrated here is that they are solid state and fully compatible with semiconductor manufacturing, so they can be electrically pumped and fully integrated at chip-scale," said Volker Sorger, a Ph.D. student in Zhang's lab and study co-lead author.
"Plasmon lasers represent an exciting class of coherent light sources capable of extremely small confinement," said Zhang. "This work can bridge the worlds of electronics and optics at truly molecular length scales."
Scientists hope to eventually shrink light down to the size of an electron's wavelength, which is about a nanometer, or one-billionth of a meter, so that the two can work together on equal footing.
"The advantages of optics over electronics are multifold," added Thomas Zentgraf, a post-doctoral fellow in Zhang's lab and another co-lead author of the Nature paper. "For example, devices will be more power efficient at the same time they offer increased speed or bandwidth."
In addition to the three co-lead authors, other co-authors of the paper are Renmin Ma and Lun Dai from Peking University, and Christopher Gladden and Guy Bartal from Zhang's research group.
This work is supported by the U.S. Air Force Office of Scientific Research and the NSF.
Sarah Yang | EurekAlert!
Further reports about: > DNA molecule > NSF > Nature Immunology > Science TV > Télécommunications > electronic circuitry > laser physics > light energy > light source > optical computing > oscillating electrons > processing power > single protein molecule > surface plasmons > world's smallest semiconductor laser
NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center
Pluto's hydrocarbon haze keeps dwarf planet colder than expected
16.11.2017 | University of California - Santa Cruz
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses