at an exceptional point<img alt="phonon laser" src="/news/PublishingImages/Yang_optomechanics_news%20v5%20v1.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>​A team of international researchers led by engineers at Washington University in St. Louis has seen the light and now has a lasing system that produces "good vibrations." </p><p>They developed a lasing system already adept at producing tiny light packets called photons into a tunable system that also makes little bits of mechanical energy called phonons — the energy products of oscillation, or vibration. <br/></p><p>In doing so, they are the first research group to broaden what is called a laser linewidth in the phonon laser and steer it through a physical system known as the "exceptional point."<br/></p><p>Linewidth is a key component of lasing, showing the physical integrity of the lasing signal as well as the measure of usually unwanted noise in the laser. <br/></p><p>The study, which involved collaborators from China, Austria, Japan and Michigan, was published in the July 9, 2018, issue of <em><a href="">Nature Photonics</a></em>.<br/></p><p>"We've shown that you can use a light field to trigger the mechanical movement that will generate an acoustic (sound) wave," said Lan Yang, the Edwin H. & Florence G. Skinner Professor of Electrical & Systems Engineering. "Think of phonon lasing as a counterpart to traditional optic, or photon lasing, with exciting applications in medical surgery, materials science and communications. We have demonstrated a controllable phonon laser that can be tuned for threshold and linewidth, among other potential parameters.<br/></p><p>"Our study for the first time provides direct evidence that exceptional point-enhanced optical noises can be transferred directly to mechanical noises," Yang said.<br/></p><p>Yang's laser, an acronym for light amplification by stimulated emission of radiation, belongs to a category called whispering gallery mode resonators (WGM), which work like the famous whispering gallery in St. Paul's Cathedral in London, where someone on the one side of the dome can hear a message spoken to the wall by someone on the other side. Unlike the dome, which has resonances or sweet spots in the audible range, the sensor resonates at light frequencies and now at vibrational or mechanical frequencies. <br/></p><p>Think of the exceptional point as a complex, super-energy mode where often unpredictable and counterintuitive phenomena occur. Already, the exceptional point has contributed to a number of counterintuitive activities and results in recent physics studies — with more expected to be discovered. In this international research project, mathematical tools were used to describe the physical system: An exceptional point arose in a physical field when two complex eigenvalues and their eigenvectors coalesced, or became one and the same. <br/></p><p>We use the phonon laser system rather than the photon laser to demonstrate our main results because it is easier to check the linewidth of the phonon laser compared with that of the photon laser."<br/></p><p>Picture the two WGM microresonators set closely to each other in a field with two photon detectors connected by a wave guide which brings light in and out of the system. Call these two "super modes" Resonator 1 and Resonator 2.  <br/></p><p>"In the first resonator, which supports photons and produces phonons, we know when the light field is strong enough the radiation will trigger the mechanical oscillation related to the acoustic wave vibration," Yang said. "We calibrated the acoustic wave frequency at 10 megahertz. Then we adjusted the gap between the two resonators to look at the transmission spectrum of the coupled resonators. When we changed the gap, we found that we could tune the spectral distance. We tuned it from 100 megahertz, to 80 to 50 depending on the physical gap between the resonators. If you tune the gap nicely to match the spectral distance between the two to the frequency of the mechanical vibration, then you have resonance." <br/></p><p>Resonance is the phenomenon whereby an external force from a system causes another system to oscillate at certain frequencies.<br/></p><p>The two light fields have two different frequencies and energy levels. The mechanical frequency of 10 megahertz matches the energy difference between the two super modes. Both resonators support photons, but only one produces phonons.<br/></p><p>In future work, Yang intends to study more deeply the energy exchange between the two super modes in phonon lasing and continue to seek surprises at the exceptional point.<br/></p><p>She calls phonon lasing's future, ironically, "very bright."<br/></p><SPAN ID="__publishingReusableFragment"></SPAN><p><span class="ms-rteStyle-References"><br/></span></p><p>Zhang J, Peng B, Ozdemir S, Pichler K, Krimer D, Zhao G, Nori F, Liu Y, Rotter S, Yang L. Operating a phonon laser at the exceptional point. <em>Nature Photonics</em>, July 9, 2018. <br/></p><p>This research was supported by funding from the National Science Foundation; the Army Research Office; the European Commission; National Natural Science Foundation of China; National Basic Research Program of China; the Tsinghua University Initiative Scientific Research Program; the Tsinghua National Laboratory for Information Science and Technology Cross-Discipline Foundation; Air Force Office of Scientific Research; Asian Office of Aerospace Research and Development (AOARD); RIKEN-AIST Joint Research Fund; the Sir John Templeton Foundation; and the Austrian Science Fund.</p><p><br/></p><p>​<br/></p><div><div class="cstm-section"><h3>Lan Yang<br/></h3><div style="text-align: center;"><strong><a href="/Profiles/Pages/Lan-Yang.aspx"><img src="/Profiles/PublishingImages/Yang_Lan.jpg?RenditionID=3" alt="Lan Yang" style="margin: 5px;"/></a> <br/></strong></div><ul style="text-align: left;"><li>Edwin H. & Florence G. Skinner Professor</li><li>Expertise: Photonics, optical sensing, microresonators, lasers, non-Hermitian physics, parity-time symmetry in photonics<br/></li></ul><p style="text-align: center;"><a href="/Profiles/Pages/Lan-Yang.aspx">>> View Bio</a><br/></p></div></div>A phonon laser formed by coupled optical resonators. Mechanical vibrations in resonator (blue) could be enhanced when the frequency difference of two optical supermodes matches with the frequency mechanical vibrations. Credit: Micro/Nano Photonics Lab Tony Fitzpatrick2018-07-16T05:00:00ZA team of international researchers led by engineers at Washington University has developed a way to use a light field to trigger a mechanical movement that will generate an acoustic wave.<p>​New laser uses light to create sound<br/></p> a better microscope<img alt="" src="/news/PublishingImages/microscope-172212825.jpg?RenditionID=1" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>​Like our eyes, microscopes are limited in what they can see because of their resolution, or their ability to see detail. The detail, or information, from the <g class="gr_ gr_48 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Punctuation only-ins replaceWithoutSep" id="48" data-gr-id="48">object</g> is there, but some of it gets lost as the light reflecting off of the object moves through the air.<br/></p><p>Ulugbek Kamilov, an engineer in the School of Engineering & Applied Science at Washington University in St. Louis, plans to use a three-year, $265,293 grant from the National Science Foundation to capture the information that normally gets lost and add it to the information researchers typically receive from microscopes. Ultimately, this work, along with that of his collaborator, Lei Tian at Boston University, may lead to a more precise microscope that can see objects as <g class="gr_ gr_42 gr-alert gr_spell gr_inline_cards gr_disable_anim_appear ContextualSpelling" id="42" data-gr-id="42">miniscule</g> as 100 nanometers, such as viruses. Currently, microscopes have a resolution limit of about 500 nanometers, which allows them to see bacteria. A human hair, for instance, is 100,000 nanometers wide.<br/></p><p>"The whole premise of this is built on one single fact — the way light interacts with any matter is linear," said Kamilov, assistant professor of electrical & systems engineering and computer science & engineering. "But the reality is that the interaction is actually not linear."<br/></p><p>For example, if you shine a flashlight through your hand, you can't see the source of the light because it's bending, and that is nonlinearity. With a single cell, the bending is so light that it is nearly transparent, which is linear.<br/></p><p>When light interacts with a cell or an object, the light going out of the cell loses the information it gathers from that interaction. But because of that interaction, there are fluctuations in the vicinity of that cell that work with such matter and get retransformed and remitted. Those fluctuations are encoded into the nonlinearity of the interaction, but today's microscopes are unable <g class="gr_ gr_55 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Grammar only-ins replaceWithoutSep" id="55" data-gr-id="55">see</g> this, Kamilov said.<br/></p><p>"We want to take into account this nonlinear interaction of light, objects <g class="gr_ gr_43 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Punctuation only-ins replaceWithoutSep" id="43" data-gr-id="43">and</g> premises, and if we do it correctly, we can extract that information, which normally disappears in a current microscope and is treated as 'noise,'" Kamilov said. "We want to decode the information from the noise and add it back into the resolution, and that should give us features that are smaller than the resolution limit."<br/></p><p>Kamilov said there are two types of noise: imperfections and mathematical noise that is the result of science's current limitations. It is the mathematical noise that he wants to capture.<br/></p><p>"In reality, that noise is information, and we want to use that information to break the barrier to see beyond the resolution limit," he said.</p><p>Kamilov's collaborator, Tian, assistant professor of electrical & computer engineering, received a $250,707 grant from the NSF to build a new microscope that will use Kamilov's computational results, algorithms <g class="gr_ gr_47 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Punctuation only-ins replaceWithoutSep" id="47" data-gr-id="47">and</g> software and could be used in medical imaging, biological and material imaging, brain mapping and drug discovery. Together, the set of studies totals $516,000.<br/></p><p>Kamilov also plans to use machine learning to learn the features of the objects they are looking at with the microscope.<br/></p><p>"We want to look at the distinguishing features of cells so that when we combine them with the nonlinear measurements and fuse that information, we will be able to get higher resolution images," he said. "We hope to get up to five times improvement."<br/></p><p>Kamilov uses high-powered graphical processing units (GPUs) in his lab, which significantly speed the processing time. What took two days of processing on a regular computer takes just milliseconds on a GPU, he said.<br/></p><p>"This project is very <g class="gr_ gr_53 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Punctuation only-del replaceWithoutSep" id="53" data-gr-id="53">timely,</g> because we have the mathematical sophistication of signal processing, the computational tools <g class="gr_ gr_52 gr-alert gr_gramm gr_inline_cards gr_disable_anim_appear Punctuation only-ins replaceWithoutSep" id="52" data-gr-id="52">and</g> machine learning," he said. "All of those things have improved together. It would have been very difficult to do this project 10 years ago."<br/></p><SPAN ID="__publishingReusableFragment"></SPAN><p><br/></p><div><div class="cstm-section"><h3>Ulugbek Kamilov<br/></h3><div style="text-align: center;"><strong><a href="/Profiles/Pages/Rajan-Chakrabarty.aspx"><img src="/Profiles/PublishingImages/Kamilov,%20Ulugbek.JPG?RenditionID=3" alt="" style="margin: 5px;"/></a> <br/><a href="/Profiles/Pages/Rajan-Chakrabarty.aspx"><strong></strong></a></strong></div><div style="text-align: center;"><ul style="text-align: left;"><li>Assistant Professor of Computer Science & Engineering and Electrical & Systems Engineering<br/></li><li>Expertise: C<span style="font-size: 1em;">omputational imaging with an emphasis on the development of computational methods for biomedical and industrial imaging</span><br/></li></ul><p><a href="/Profiles/Pages/Ulugbek-Kamilov.aspx">View Bio</a><br/></p></div></div> ​​</div>Beth Miller 2018-06-22T05:00:00ZUsing computations, machine learning and signal processing, Ulugbek Kamilov plans to lay the groundwork for a better microscope.<p>WashU engineer to combine math, machine learning and signal processing to lay groundwork for high-resolution microscope<br/></p> speaks at computational conference <img alt="Shantanu Chakrabartty" src="/Profiles/PublishingImages/Chakrabartty_Shantanu.jpg?RenditionID=2" style="BORDER:0px solid;" /><p>Shantanu Chakrabartty, professor of electrical & systems engineering, was one of the keynote speakers at the 2018 Conference on Computational Intelligence in Bioinformatics and Computational Biology held May 30-June 2 in St. Louis. <br/></p>Shantanu Chakrabartty2018-06-14T05:00:00ZShantanu Chakrabartty, professor of electrical & systems engineering, was one of the keynote speakers at the 2018 Conference on Computational Intelligence in Bioinformatics and Computational Biology. St. Louis to Singapore to Texas: Justin Ruths <img alt="Justin and Melissa Ruths" src="/news/PublishingImages/Justin%20Ruths%20alumni%20profile.jpg?RenditionID=2" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>After earning a bachelor’s degree in physics at Rice University, Justin Ruths was looking for something he could get his hands on. He found it in engineering and applied math at Washington University in St. Louis, and <g class="gr_ gr_76 gr-alert gr_gramm gr_inline_cards gr_run_anim Punctuation only-del replaceWithoutSep" id="76" data-gr-id="76">today,</g> is giving back by teaching future engineers and conducting research at the University of Texas at Dallas (UTD). <br/></p><div>Ruths earned a master’s degree in electrical engineering from the School of Engineering & Applied Science at WashU in 2008 and a doctorate in systems science & applied math in 2011. As the first doctoral student in the lab of Jr-Shin Li, associate professor of electrical & systems engineering, Ruths became interested in control, which allowed him to apply his physics background to modeling and optimizing quantum spin dynamics and neuron behavior. </div><div><br/></div><div>Ruths’ family lived in Indonesia for much of his childhood, so he and his wife, Melissa, were eager to live outside of the United States for a few years. After he finished his doctorate, the <g class="gr_ gr_77 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="77" data-gr-id="77">Ruthses</g> moved to Singapore, where he became an assistant professor of engineering systems & design at the Singapore University of Technology and Design (SUTD), the country’s fourth-largest public university, with collaboration ties to MIT and founded two years prior, while Melissa worked in Emerson Electric Co.’s Singapore office. The first class of SUTD undergraduates began in 2012, so Ruths was in on the ground floor of a new technology-focused university where he saw many growth opportunities, including in program and curriculum building as well as some administration. </div><div><br/></div><div>“I was one of the first 20 <g class="gr_ gr_67 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar multiReplace" id="67" data-gr-id="67">faculty</g> hired there, and there was a lot to do,” he said. “The nice thing about that kind of growth is that you can find many opportunities to get involved.”<br/></div><div><br/></div><div>While in Singapore, the <g class="gr_ gr_60 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="60" data-gr-id="60">Ruthses</g> took advantage of the country’s location to travel, including taking a six-day horseback trek in Mongolia on which they rode through <g class="gr_ gr_65 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar only-ins doubleReplace replaceWithoutSep" id="65" data-gr-id="65">wilderness</g> and helped to herd sheep.</div><div><br/></div><div>Ready to return to the U.S., the couple — and their seven-week-old daughter — headed to Texas in 2016. Ruths joined the faculty at UTD, where he is an assistant professor of mechanical engineering and of systems engineering. He currently has two doctoral students and one master’s student in his lab. </div><div><br/></div><div>“UTD is experiencing a large amount of growth, and it was an exciting opportunity for me,” he said. “The mechanical engineering department started in 2008, so it’s relatively young. There is a lot of energy here, especially in the area of control theory.” </div><div><br/></div><div>Ruths’ research in control falls into three areas. He continues the work he did in Li’s lab designing inputs, working with applications in quantum control and in neuroscience. In addition, he studies large-scale systems as networks, including work published in <em>Science</em> in 2014. </div><div><br/></div><div>“Recently there has been an interest in understanding network behavior. Once we can model a network and predict what it might do, then we can start to understand how to control it,” he said. “For example, when a person experiences an epileptic seizure, there’s a kind of pathological behavior in the oscillation of the activation occurring on the network of neurons in the brain. Our goal is to change that behavior — to drive the oscillation to some other behavior, effectively stopping the seizure.” </div><div><br/></div><div>Ruths also seeks to understand the security of control systems, such as in industrial automation applications.</div><div><br/></div><div>“Control processes are in charge of making sure things go smoothly,” he said. “The question of control has largely been about designing algorithms to make sure this still happens, even in <g class="gr_ gr_59 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar only-ins doubleReplace replaceWithoutSep" id="59" data-gr-id="59">context</g> of random disturbances, noises and uncertainties, and even if we don’t model the systems completely correctly. Security raises altogether new challenges for control theory due to the adversarial nature of attacks.”</div><div><br/></div><div>“Because of the typical size of an industrial system, such as a refinery, detection and response mechanisms need to be automated,” he said. “We build algorithms, supported by mathematical reasoning, to look for the signatures of attacks and make adjustments if we find them.” </div><div><br/></div><div>Ruths presented his research results on industrial control systems March 1 at a WashU seminar. </div><div><br/></div><div>While a doctoral student, Ruths had an interesting opportunity that gave him some hands-on teaching experience. As a National Science Foundation’s Graduate STEM Fellow in K-12 Education, Ruths had the opportunity to teach science, technology, engineering and mathematics (STEM), in area middle and high schools during his first two years. He used the Lego Mindstorms kit to teach robotics, basics in control, cruise control and other methods. </div><div><br/></div><div>“Having those two years was a really neat way to interface with students,” he said. “It also helped to connect me with the St. Louis area.”<br/></div><div><br/></div><div><SPAN ID="__publishingReusableFragment"></SPAN><br/></div><p>​<br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p><p><br/></p>Justin and Melissa Ruths on their six-day horseback trek in Mongolia on which they rode through wilderness and helped to herd sheep.Beth Miller 2018-06-11T05:00:00ZAlumnus Justin Ruths continues network behavior research at UT-Dallas<p>​​Alumnus Justin Ruths took his WashU Engineering education abroad to help establish a new program before returning to the U.S. to teach mechanical and systems engineering<br/></p>$20,000-for-collaborative-research.aspx877Engineering faculty awarded $20,000 for collaborative research<p>​ShiNung Ching, Nate Huebsch, Ulugbek Kamilov and Rohan Mishra have all been awarded grants to promote collaborative research.<br/></p><img alt="" src="/news/PublishingImages/collaborative%20research%20faculty.jpg?RenditionID=12" style="BORDER:0px solid;" /><div id="__publishingReusableFragmentIdSection"><a href="/ReusableContent/36_.000">a</a></div><p>Four assistant professors in the School of Engineering & Applied Science have been awarded $20,000 grants from the School's Collaboration Initiation Grants program, which awards one-year grants to tenure-track faculty to promote collaborative research.</p><p>This year's awardees are ShiNung Ching, Nate Huebsch, Ulugbek Kamilov and Rohan Mishra. Each awardee receives funding from the school and must have $5,000 in cost-sharing from their department or collaborators. Ching and Kamilov each received $5,000 from the Institute of Clinical & Translational Sciences at the School of Medicine.</p><p>The grants encourage faculty to apply for larger, interdisciplinary grants, to create a more synergistic project <g class="gr_ gr_32 gr-alert gr_spell gr_inline_cards gr_disable_anim_appear ContextualSpelling ins-del" id="32" data-gr-id="32">than</g> could be achieved by one researcher in one discipline, and to demonstrate the potential to sustain the collaboration and obtain external funding.</p><p><img src="/Profiles/PublishingImages/Ching_ShiNung.jpg?RenditionID=10" class="ms-rtePosition-2" alt="" style="margin: 10px;"/>Ching, assistant professor of electrical & systems engineering, is collaborating with Rejean Guerriero, assistant professor of neurology and a pediatric neurologist at St. Louis Children's Hospital. They seek to improve signal processing and dynamical systems modeling to provide better explanations of ultraslow network activity in the brain, which they believe is behind a state of unrelenting seizures in critically ill children. They believe this state may be preceded by a novel brain activity pattern that is too slow to be captured on traditional electroencephalogram monitoring devices. Identifying the physiological mechanisms underlying this pattern would allow for intervention and potential treatment of this condition.</p><p><img src="/Profiles/PublishingImages/Huebsch_Nate.jpg?RenditionID=10" class="ms-rtePosition-1" alt="" style="margin: 10px;"/>Huebsch, assistant professor of biomedical engineering, is collaborating with Guy Genin, the Harold and Kathleen Faught Professor of Mechanical Engineering and professor of neurological surgery. They plan to develop an in vitro model of the effects of afterload on human heart cells using their expertise in human-induced pluripotent stem cell-based tissue engineering and biomaterials. With these models, they will apply forces that mimic the forces applied to heart cells when the heart has to pump blood against increased systemic resistance. They will apply this system to muscle cells in the heart that are genetically predisposed to dilated cardiomyopathy, a condition in which the heart's ability to pump blood is decreased. The investigators said that by combining physical and genetic causes of cardiomyopathy within their model, they will make more accurate disease-in-a-dish models that can ultimately be used to discover new therapies.  </p><p><img src="/Profiles/PublishingImages/Kamilov,%20Ulugbek.JPG?RenditionID=10" class="ms-rtePosition-2" alt="" style="margin: 10px;"/>Kamilov, assistant professor of computer science & engineering and of electrical & systems engineering, is collaborating with Hongyu An, associate professor in the Mallinckrodt Institute of Radiology at the School of Medicine and associate director of the Center for Clinical Imaging Research. They plan to develop a novel data-adaptive imaging framework that removes "noise" or errors in magnetic resonance imaging (MRI) caused by patient motion. The work will focus on efficient data acquisition and high-quality image reconstruction. Their goal is to create a single, holistic imaging framework that uses available data to generate error-free images from highly dynamic MRI data.</p><p><img src="/Profiles/PublishingImages/Mishra_Rohan_03.jpg?RenditionID=10" class="ms-rtePosition-1" alt="" style="margin: 10px;"/>Mishra, assistant professor of mechanical engineering & materials science, is collaborating with Vijay Ramani, the Roma B. and Raymond H. Wittcoff Professor of Energy, Environmental & Chemical Engineering. They plan to rationally design cheap and corrosion-resistant, transition-metal-based electrocatalysts that can be used in automotive fuel cells to promote the oxygen-reduction reaction. Currently, fuel cells use expensive platinum-group-metal-based catalysts. Mishra will predict potential catalysts using high-throughput, quantum-mechanical calculations and material informatics. Once discovered, Ramani will synthesize the materials and measure their catalytic activity, and then the team will characterize them for further optimization. Ultimately, they hope to find a catalyst that could meet the Department of Energy's Fuel Cell Program's 2020 targets for activity and stability.</p><p> </p><SPAN ID="__publishingReusableFragment"></SPAN><p><br/></p><p><br/></p>From left: ShiNung Ching, Nate Huebsch, Ulugbek Kamilov and Rohan MishraBeth Miller 2018-05-30T05:00:00ZFour faculty have been awarded grants to collaborate with other university researchers.


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