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  • richardmitnick 11:07 am on June 8, 2017 Permalink | Reply
    Tags: , Center for MicroNanotechnology (CMi) at EPFL, , EPFL’s Laboratory of Photonics and Quantum Measurements (LPQM), Institute of Microstructure Technology (IMT), KIT’s Institute of Photonics and Quantum Electronics (IPQ), LiGenTec SA, Optical frequency combs, Optical Solitons, , , Wavelength division multiplexing (WDM)   

    From EPFL: “Ultra-fast optical data transfer using solitons on a photonic chip” 

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    École Polytechnique Fédérale de Lausanne EPFL

    Nik Papageorgiou

    Optical micro resonators made from silicon nitride on a chip using for soliton based communications. © V. Brasch (LPQM, EPFL)
    Researchers from EPFL and Karlsruhe Institute of Technology use a soliton frequency combs from optical microresonators to transmit data at speeds of more than 50 terabits per second.

    Optical solitons are special wave packages that propagate without changing their shape. They are ubiquitous in nature, and occur in Plasma Physics, water waves to biological systems. While solitons also exist in optical fiber, discovered at Bell labs in the 1980’ies, there technological use so far has been limited. While researchers studied their use for optical communication, eventually the approach was abandoned. Now, a collaboration of a research group at KIT’s Institute of Photonics and Quantum Electronics (IPQ) and Institute of Microstructure Technology (IMT) with EPFL’s Laboratory of Photonics and Quantum Measurements (LPQM) have shown that solitons may experience a comeback: Instead of using a train of soliton pulses in an optical fiber, they generated continuously circulating optical solitons in compact silicon nitride optical microresonators. These continuously circulating solitons lead to broadband optical frequency combs. Two such superimposed frequency combs enabled massive parallel data transmission on 179 wavelength channels at a data rate of more than 50 terabits per second – a record for frequency combs. The work is published in Nature [link is below].

    Optical frequency combs, for which John Hall and Theodor W. Hänsch were awarded the Nobel Prize in Physics in 2005, consist of a multitude of neighboring spectral lines, which are aligned on a regular equidistant grid. Traditionally, frequency combs serve as high-precision optical references for measurement of frequencies. The invention of so-called Kerr frequency combs, which are characterized by large optical bandwidths and by line spacings that are optimal for communications, make frequency combs equally well suited for data transmission. Each individual spectral line can be used for transmitting a data signal.

    In their experiment, the researchers from KIT and EPFL used optical silicon nitride micro-resonators on a photonic chip that can easily be integrated into compact communication systems. For the communications demonstration, two interleaved frequency combs were used to transmit data on 179 individual optical carriers, which completely cover the optical telecommunication C and L bands and allow a transmission of data rate of 55 terabits per second over a distance of 75 kilometers. “This is equivalent to more than five billion phone calls or more than two million HD TV channels. It is the highest data rate ever reached using a frequency comb source in chip format,” explains Christian Koos, professor at KIT’s IPQ and IMT and recipient of a Starting Independent Researcher Grant of the European Research Council (ERC) for his research on optical frequency combs.

    The components have the potential to reduce the energy consumption of the light source in communication systems drastically. The basis of the researchers’ work are solitons generated in low-loss optical silicon nitride micro-resonators. In these, an optical soliton state was generated for the first time by Kippenberg’s lab at EPFL in 2014. ”The soliton forms through nonlinear processes occurring due to the high intensity of the light field in the micro-resonator” explains Kippenberg. The microresonator is only pumped through a continuous-wave laser from which, by means of the soliton, hundreds of new equidistant laser lines are generated. The silicon nitride integrated photonic chips are grown and fabricated in the Center for MicroNanotechnology (CMi) at EPFL. Meanwhile, a startup from LPQM, LiGenTec SA, is also offering access to these photonic integrated circuits to interested academic and industrial research laboratories.

    The work shows that microresonator soliton frequency comb sources can considerably increase the performance of wavelength division multiplexing (WDM) techniques in optical communications. WDM allows to transmit ultra-high data rates by using a multitude of independent data channels on a single optical waveguide. To this end, the information is encoded on laser light of different wavelengths. For coherent communications, microresonator soliton frequency comb sources can be used not only at the transmitter, but also at the receiver side of WDM systems. The comb sources dramatically increase scalability of the respective systems and enable highly parallel coherent data transmission with light. According to Christian Koos, this is an important step towards highly efficient chip-scale transceivers for future petabit networks.

    This work was supported by the European Research Council (Starting Grant ‘EnTeraPIC’), the European Union (project BigPipes), the Alfried Krupp von Bohlen und Halbach Foundation, the Karlsruhe School of Optics & Photonics (KSOP), and the Helmholtz International Research School for Teratronics (HIRST), the Erasmus Mundus Doctorate Program Europhotonics, the Deutsche Forschungsgemeinschaft (DFG), the European Space Agency, the US Air Force (Office of Scientific Research), the Swiss National Science Foundation (SNF), and the Defense Advanced Research Program Agency (DARPA) via the program Quantum Assisted Sensing and Readout(QuASAR).


    Pablo Marin-Palomo, Juned N. Kemal, Maxim Karpov, Arne Kordts, Joerg Pfeifle, Martin H. P. Pfeiffer, Philipp Trocha, Stefan Wolf, Victor Brasch, Miles H. Anderson, Ralf Rosenberger, Kovendhan Vijayan, Wolfgang Freude, Tobias J. Kippenberg, Christian Koos. Microresonator solitons for massively parallel coherent optical communications.Nature 08 June 2017.

    See the full article here .

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    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university with students, professors and staff from over 120 nations. A dynamic environment, open to Switzerland and the world, EPFL is centered on its three missions: teaching, research and technology transfer. EPFL works together with an extensive network of partners including other universities and institutes of technology, developing and emerging countries, secondary schools and colleges, industry and economy, political circles and the general public, to bring about real impact for society.

  • richardmitnick 7:36 am on September 7, 2016 Permalink | Reply
    Tags: , , Optical Solitons,   

    From Caltech: “New Breed of Optical Soliton Wave Discovered” 

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    Robert Perkins
    (626) 395-1862

    These optical microcavities are where solitons are created. The solitary waves circle around the microscopic disks at the speed of light.
    Credit: Qi-Fan Yang/Caltech

    Applied scientists led by Caltech’s Kerry Vahala have discovered a new type of optical soliton wave that travels in the wake of other soliton waves, hitching a ride on and feeding off of the energy of the other wave.

    Solitons are localized waves that act like particles: as they travel across space, they hold their shape and form rather than dispersing as other waves do. They were first discovered in 1834 when Scottish engineer John Scott Russell noted an unusual wave that formed after the sudden stop of a barge in the Union Canal that runs between Falkirk and Edinburgh. Russell tracked the resulting wave for one or two miles, and noted that it preserved its shape as it traveled, until he ultimately lost sight of it.

    He dubbed his discovery a “wave of translation.” By the end of the century, the phenomenon had been described mathematically, ultimately giving birth to the concept of the soliton wave. Under normal conditions, waves tend to dissipate as they travel through space. Toss a stone into a pond, and the ripples will slowly die down as they spread out away from the point of impact. Solitons, on the other hand, do not.

    In addition to water waves, solitons can occur as light waves. Vahala’s team studies light solitons by having them recirculate indefinitely in micrometer-scale circular circuits called optical microcavities. Solitons have applications in the creation of highly accurate optical clocks, and can be used in microwave oscillators that are used for navigation and radar systems, among other things.

    But despite decades of study, a soliton has never been observed behaving in a dependent—almost parasitic—manner.

    “This new soliton rides along with another soliton—essentially, in the other soliton’s wake. It also syphons energy off of the other soliton so that it is self-sustaining. It can eventually grow larger than its host,” says Vahala, Ted and Ginger Jenkins Professor of Information Science and Technology and Applied Physics and executive officer for applied physics and materials science in the Division of Engineering and Applied Science.

    Vahala likens these newly discovered solitons to pilot fish, carnivorous tropical fish that swim next to a shark so they can pick up scraps from the shark’s meals. And by swimming in the shark’s wake, the pilot fish reduce the drag of water on their own body, so they can travel with less effort.

    Vahala is the corresponding author of a paper in the journal Nature Physics announcing and describing the new type of soliton, dubbed the “Stokes soliton.” (The name “Stokes” was chosen for technical reasons having to do with how the soliton syphons energy from the host.) The new soliton was first observed by Caltech graduate students Qi-Fan Yang and Xu Yi. Because of the soliton’s ability to closely match the position and shape of the original soliton, Yang’s and Yi’s initial reaction to the wave was to suspect that laboratory instrumentation was malfunctioning.

    “We confirmed that the signal was not an artifact of the instrumentation by observing the signal on two spectrometers. We then knew it was real and had to figure out why a new soliton would spontaneously appear like this,” Yang says.

    The microcavities that Vahala and his team use include a laser input that provides the solitons with energy. This energy cannot be directly absorbed by the Stokes soliton—the “pilot fish.” Instead, the energy is consumed by the “shark” soliton. But then, Vahala and his team found, the energy is pulled away by the pilot fish soliton, which grows in size while the other soliton shrinks.

    “Once we understood the environment required to sustain the new soliton, it actually became possible to design the microcavities to guarantee their formation and even their properties like wavelength—effectively, color,” Yi says. Yi and Yang collaborated with graduate student Ki Youl Yang on the research.

    The research was funded by the Defense Advanced Research Projects Agency under the PULSE Program; NASA; the Kavli Nanoscience Institute; and the Institute for Quantum Information and Matter, a National Science Foundation Physics Frontiers Center supported by the Gordon and Betty Moore Foundation.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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