Kevin Chen - US grants

The objective of this research program is to develop a novel ultrafast laser processing technique to fabricate high-quality and low-cost lightwave circuits and electro-optic devices in silica glasses. By taking advantage of multi-photon processes driven by femtosecond laser pulses, novel three-dimensional photonic devices will be fabricated in silica glasses with feature sizes below the diffraction limit.
Technical Merit: This project will first develop a novel laser processing technique using variable high repetition rate (> 250 kHz) ultrafast pulse trains. Using bulk heating to modify refractive indice in transparent materials, collateral damages induced by high peak laser intensities can be completely eliminated. The three-dimensional micro-manufacturing capability offered by the ultrafast laser will be exploited by on-chip chiral optical waveguide fabrication. Entire new classes of laser-written chiral waveguide devices will be developed in silica glasses to control the circular polarization of the guided waves. In conjunction with our material research to synthesize novel glass waveguides with large third-order optical nonlinearity, comprehensive ultrafast-laser poling studies will be carried out towards the fabrication of silica-based electro-optical devices.
Broader Impacts: The proposed research work, if successful, will yield commercially viable, low-loss, photonic components for novel three-dimensional photonic architectures, which are not attainable by any other fabrication method. The unique combination of the novel glass material synthesis and ultrafast laser poling studies has the potential to produce low-cost silica waveguide electro-optical modulators for the fiber-optical communication industry. Teaming up with local industry, faculty members from mechanical engineering and material science, we will provide an interdisciplinary training program for our undergraduate students. Undergraduate students will work on integrated laser manufacturing and product innovation through senior design projects. The PI will also work with the University of Pittsburgh undergraduate Robotics Club to support undergraduates and K-12 students in their participation in extracurricular activities. Through undergraduate training and extracurricular activities, this program will encourage more undergraduate students to further their careers by attending graduate school in science, engineering,, and medicine. Through outreach activities, we will attract more female and under-represented minority high-school students to study engineering in colleges and universities

The recent invention of microstructured optical fibers has brought fiber optics into a new era. Flexible fiber designs using air holes have enabled many exciting applications unattainable with normal fibers.
In this CAREER research project, the PI proposes to fully exploit microstructured fiber design flexibility and to develop fiber sensors with unprecedented functionalities and performance. By controlling shapes, geometry, and compositions of the fiber core, air holes, and filling materials in microstructured fibers, major enhancement in sensitivity, frequency response, and power consumption for both active and passive fiber sensors can be achieved. Multi-functional sensors and enabling technology developed from this project is expected to dramatically expand the applications of fiber sensors beyond their traditional roles.
The PI recognizes the far-reaching potential of photonic devices in modern technology and proposes an interdisciplinary training plan for all engineering students. It includes a general optical engineering course and industrial motivated senior design projects on photonic product innovation and manufacturing automation. Through undergraduate extracurricular activities in robotics, the proposed outreach activities aim to attract more female and under-represented minority students to study engineering in colleges. Overall, this program will foster interdisciplinary-trained engineers, who will understand and use photonics as part of life-long career of engineering innovation.

This is a FY07 CAREER grant of DMMI/ENG.

[unreadable] DESCRIPTION (provided by applicant): Naturally-occurring polymorphisms can affect gene expression and thereby influence human diseases, such as cancer and diabetes. A deeper understanding of cis-regulatory variation will also facilitate the design of better algorithms for predicting cis-regulatory sites and help us elucidate the impact of changes in gene regulation on speciation and phenotypic evolution. Previously, by analyzing polymorphisms in human microRNA binding sites, we identified several candidate causal variants of human disease and a set of human microRNA binding sites not conserved in other mammals. Here we propose to extend this work to transcription factor binding sites. We will use the yeast, S. cerevisiae, as a model system because it offers experimental tractability, a well-studied gene regulatory network and multiple fully-sequenced strains. Our specific aims are (1) Extend our previous techniques to accommodate degenerate motifs and insertion/deletion polymorphisms, and use our new techniques to study the function and evolution of computationally predicted yeast transcription factor binding sites (2) Fit a statistical model of transcriptional regulation to publicly available microarray data for a set of 112 segregants from an experimental cross between two S. cerevisiae strains and use the model to predict polymorphisms that significantly affect gene expression (3) Experimentally validate the candidate polymorphisms using site-directed mutagenesis and quantitative PCR. The applicant's long-term goal is to use computational and experimental approaches to identify cis-regulatory variants between different human populations and pathological conditions (e.g. cancers). Since the applicant's training is in computational biology, the main impact of this award would be to provide training in a unified computational-experimental approach with Mark Siegal, an experimentalist and Nikolaus Rajewsky, a bioinformatician. Relevance: Many human diseases, such as cancer and diabetes, are caused in part by the aberrant regulation of specific genes. Identifying the genetic mutations responsible for the changes in control of these genes is the first step towards diagnosing and ultimately curing these diseases. The long-term aim of this project is to develop and validate computational methods that can be used to compile a comprehensive catalogue of gene regulatory variation in the human genome. [unreadable] [unreadable] [unreadable]

Abstract
ECCS-0801869
A. Heberle, University of Pittsburgh
Objective: Mode-locking of lasers is an important technique for generation of frequency combs and trains of picosecond or femtosecond optical pulses. So far, only longitudinal modes have been locked reliably, leading to pulses traveling around the laser cavity in direction of to the light beam.

Intellectual Merit: The goal of this experimental research program is the investigation of a new process, lateral two-dimensional mode-locking in monolithic vertical-cavity surface-emitting lasers (VCSEL?s), and the fabrication/exploration of novel devices for picoseconds or even femtosecond pulse and frequency comb generation. The project aims to demonstrate that lateral mode-locking of round VCSEL?s produces solitons that move in circles around the emission aperture. This work will not only provide understanding of ultrafast dynamics and soliton propagation in VCSEL?s, but it will add ultrafast mode-locking and frequency comb generation to this increasingly important class of lasers. It is expected, for example, that laterally mode-locked VCSEL?s will provide two orders of magnitude better control of the pulse repetition rate than conventional, longitudinally mode-locked monolithic semiconductor lasers, in which the repetition rate can be tuned by only about 0.5%. Mode-locked VCSEL?s could have significant applications for optical communication, sensing, and displays in which the blue and green colors are generated by frequency doubling.

Broader Impact: The project gives graduate and undergraduate students hands-on experience in several important fields: femtosecond technology, photonics, nanoscience, and semiconductor technology. It also supports the interdisciplinary photonics course program and the early lab experience program that involves underrepresented minorities at the University of Pittsburgh

In the last two decades, the nanotechnology revolution has led to a number of new materials, novel processing techniques, and complex nano-systems with extraordinary functionalities. This program will push nanotechnology into new frontiers in nuclear engineering. It explores interdisciplinary research opportunities that bridge nuclear engineering and nanotechnology.
Novel nano-materials and nano-structures will be used to develop new means of harnessing nuclear energy and efficiently convert it into electric and optical energy. Long-life, miniaturized nuclear batteries will be developed to provide sustained ?ÝW-level power for support of mission-critical micro- and nano-systems. A contamination-free fabrication technique will be developed to monolithically integrate micro-scale radioactive isotopes with on-chip nano-devices. New devices for power generation and sensing will be explored for homeland security and biomedical applications. This program will also leverage recent advances in novel nanostructures for the detection of radioactive materials.
This interdisciplinary research, fusing nanotechnology and nuclear engineering, will spark new opportunities in their respective areas of science and technology. Isotope micro-power sources will dramatically improve the operational life of micro- and nano- systems used for unattended applications, which span remote exploration, unmanned military operations and implanted devices. The chip-scale development of micro-isotope sources will enable detailed studies of radiation effects at the cellular level. This may lead to improved cancer treatment using radiation therapy. The use of novel nano-structures promises to speed the development of high-sensitivity radiation detectors for homeland security and for environmental protection. The proposed education efforts will offer students a refreshing perspective that bridges the small nano-world with giant nuclear power plants.

Naturally-occurring polymorphisms can affect gene expression and thereby underlie human diseases and other important phenotypic traits. A deeper understanding of cis-regulatory variafion will also facilitate the design of better algorithms for predicting cis-regulatory sites and help us elucidate the impact of changes in gene regulafion on morphological evolution. Previously, we analyzed polymorphisms in human and Drosophila microRNA sites and yeast transcription factor binding sites and their relafion to changes in gene expression between individuals in a species, Here we propose to extend this work to cis-regulatory sites that mediate post-transcripfional control via binding of RNA-binding proteins in S. cerevisiae. We use S. cerevisiae as a model system because it offers experimental tractability, arguably the best studied Eukaryofic gene regulatory network and mulfiple sequenced strains. RNA processing is a fundamental cellular process and factors involved in these pathways are conserved in higher Eukaryotes. Our specific aims for the ROO phase are (1) We will collect the best possible set of motifs for yeast RNA-binding proteins from the literature and by analyzing recent RNA immunoprecipitation (RIP-chip) data and microarray data following knock-out of various RNA-binding proteins. We will test exisfing motif finding tools and try to extend them using regression and conservation techniques, (2) We will predict cis-regulatory sites for RNA binding proteins by combining comparative and populafion genomics data in yeast. We will experimentally validate a subset of the predictions using standard site-directed mutagenesis and qPCR techniques. (3) We will use the recentiy available Digital Gene Expression [unreadable] Tag Profiling kit from lllumina to annotate 3'end isoforms In the BY and RM strains and two environmental conditions to help us predict the cis-regulatory sites in Aim 2. If there is at least one gene that is differenfially polyadenylated between BY and RM, we will map cis- and trans- regulators of alternative polyadenylation using either the well-studied BY/RM segregant lines or a panel of recently sequenced wild isolates. Our long-term goal is to use computafional and experimental approaches to link sequence polymorphisms and gene expression changes to morphological change.

DESCRIPTION (provided by applicant): Cocaine addiction continues to be a major public health problem in the U.S. With no FDA- approved pharmaceutical therapy, treatment often relies on psychosocial interventions, known as behavior therapy. Despite some positive progress these psychosocial interventions have limited efficacy with problems like high dropout, untreated physical symptoms and high relapse rate. Our clinical experience and pilot studies suggest that Integrative Meditation (IM) from Chinese medicine may help clients engage in treatment, reduce cravings/ withdrawal symptoms, and increase treatment retention, which appear missed by a typical behavior therapy. IM is an adaptation or simplified form of mindfulness meditation. It may enhance existing therapies to help reduce withdrawal symptoms, increase treatment engagement, and prevent relapse through step-by-step therapist facilitation. This will be a brief Stage-1b therapy development study, based on a preliminary therapist manual and an observational study. The specific aims include: (1) To conduct a pilot randomized controlled trial of 66 outpatient cocaine users with 12 weekly facilitation meetings to assess feasibility of recruiting and retaining cocaine addicts, and to determine effect size of IM-augmented treatment in comparison with Non-directive therapy (NT) control, with both groups receiving standard treatment as usual (TAU), (2) To examine the changes in attention networks and negative mood as possible mediators of treatment outcomes between the two groups. Treatment outcomes will be assessed at baseline, week 4, 8 and 12, and at the follow-up 3 months after intervention. Primary outcomes include cocaine urine toxicology, number of weeks in treatment, and intensity of cocaine use. Secondary outcome measures include Addiction Severity Index (ASI) composite scores, use of alcohol and other drugs, heart rate variability, craving, depression, anxiety, and self-efficacy. Additional measures are proposed to aid in understanding possible underlying mechanisms of IM's effect on attention networks and the autonomic nervous system. A diverse team experienced in meditation and behavior therapy development is brought together to conduct the proposed R21 project, and prepare for a full therapy development study. PUBLIC HEALTH RELEVANCE: Given the fact that cocaine addiction continues to be a major public health problem in the U.S. without a sound solution, the proposed study will implement a brief Stage-I study of adding Integrative Meditation (IM) as a self-care component to the current outpatient treatment to improve treatment outcome for cocaine addiction. IM requires minimum therapist involvement and can serve as an adjunct to other existing treatment modalities. It may not only provide the needed treatment for physical and psychological symptoms during withdrawal or abstinence at the time when a patient needs it, but also quickly engage patients in the treatment and improve patients'self-efficacy and attention network that could help keep them away from relapse. Therefore, if the study verifies its efficacy and feasibility, IM may become an important cost- effective tool in the field of addiction treatment.

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."

This award provides funding to acquire a high-power, high-repetition-rate, wavelength-tunable, femtosecond ultrafast laser system to study laser material interaction and to fabricate three-dimensional photonic devices. The ultrafast laser processing defines the forefront of today?s laser processing technology. Femtosecond laser pulses drive universal multi-photon photosensitivity process to change refractive index in many transparent materials. By tightly focusing the laser beam into optical substrates, the multi-photon process produces below diffraction-limit nanometer-size refractive index change for the ultra-high precision optical device fabrication. Laser-induced material damage can be mitigated by exploiting the bulk heating effect from high-repetition laser pulses. Using the acquired laser system, the mechanism of ultrafast laser photosensitivity will be thorough studied. The optimal laser processing window for a wide array of optical materials will be explored to fabricate high performance three-dimensional photonic devices that are un-attainable by other fabrication approach.

The success of the proposed research will yield a cross-platform laser fabrication technique to produce high-quality and low-loss lightwave circuits in a wide array of optical substrates for both active and passive applications. It will drastically increase the density, functionality, and complexity of the optical circuitry. This program also enables unique multi-disciplinary training opportunities for both graduate and undergraduate students. Training opportunities will cover all aspects of the laser fabrication technology including lasers, optical designs, computer control, machine vision, microstructure analysis, fiber optics, and nonlinear optics. Recruited through the University of Pittsburgh?s minority mentor EXCEL program, underrepresented minority and female students to will be encouraged to participate in academic research and training.

The research objective of this collaborative award is to develop flexible and cross-platform methods to fabricate three-dimensional (3D) lightwave circuits and photonic crystal structures in transparent media. A laser direct writing technique using high-repetition-rate femtosecond laser will be explored to produce compact 3D lightwave circuits. The approach takes advantages of multi-photon process induced by ultrashort laser pulses to initialize a universal photosensitivity response to change refractive indices in a wide array of optical materials. Bulk heating effects from high-repetition laser pulses will be utilized to mitigate laser-induced material damages to minimize optical loss and to achieve desired device performance of lightwave circuits. To fabricate 3D periodic photonic structures, multi-layer near-field diffractive optical elements will be developed to produce 3D interference patterns. Periodic photonic structures such as diamond-like photonic crystals will be fabricated using this one-optical-element and one-laser-exposure holographic fabrication process.

If successful, the results of this research will yield a cross-platform laser manufacturing technique to fabricate high-quality lightwave circuits in a wide array of optical substrates. The fabrication technique will enable new 3D photonic circuit architectures that allows lightwave circuits to be routed vertically and continuously in- and out- of a plane. This will drastically increase the density, functionality, and complexity of the optical circuitry. The success of this research will also enable the fabrication of mid-IR fiber lasers and sensor devices for applications in chemical sensing and structural health monitoring in harsh environments. The holographic laser fabrication developed from this award can be conveniently built into the existing multiple mask fabrication flow for integrated optoelectronic circuit manufacturing. This enables the monolithic integration of photonic crystal structures with other on-chip optical components for widespread applications. This award will also support an interdisciplinary training program for undergraduate students on the integrated laser manufacturing and product innovation. Through undergraduate extracurricular activities on robotics and minority outreach activities, the proposed education programs will attract female and under-represented minority students to study engineering and science at both undergraduate and graduate levels.

Abstract

1054652 (EAGER)
Peng Chen
University of Pittsburg

The Deepwater Horizon oil spills in the Gulf of Mexico has become the most damaging environmental catastrophe in the US history. The failures for scientists and engineers to promptly stop the rupture and to swiftly evaluate the environmental damage highlight a number of daunting technical challenges related to deepwater resource exploration, pollution monitoring, and ecological conservation. In this EAGAR project, a distributed sensing network based on fiber optical sensing technology is investigated and designed for in-situ measurement of subsurface oil distribution and migration. Fiber grating sensors will be fabricated in short sections of high-attenuation fibers. Each fiber sensor will be coated with oil-affinitive porous nano-materials. Once it encounters oil droplets, the porous materials will absorb oil droplet, which leads to the increase of refractive index change and absorption in porous layers. Using wavelength division multiplexing, a large number of fiber sensors can be monitored by a single interrogation instrument.

The proposed research will provide powerful and low-cost sensing tools to monitor three-dimensional oil pollution distribution and migration under ocean currents. The effectiveness of the clean-up efforts and long-term impact of oil spills to ocean ecology can be rapidly evaluated, rectified, and improved. This project will also impact the sustainability education at the University of Pittsburgh by providing unique teaching opportunities to students in terms of technological skills, professional ethnics, and environmental responsibilities.

This award supports fundamental optics science research on laser matter interaction to establish a parallel laser micro-forming manufacturing technology. Specifically, the research will use adaptive optical technology to generate multiple laser beams with arbitrary laser beam profile and energy distribution to perform rapid three-dimensional laser shock micro-forming on multiple micro workpieces simultaneously. Using the adaptive laser beam shaping tool and multi-resolution molecular mechanic simulation approach, laser-induced shock wave interaction with micro- and nano-mechanical structures will be studied to gain better understanding on laser-induced defect initiation, propagation, and distribution to improve three-dimensional laser micro-forming manufacturing outcome.

The new laser shock manufacturing scheme developed from this research has potential to completely overhaul the existing laser shock micro-forming manufacturing technique. It will dramatically improve manufacturing flexibility, precision, and throughput. The scientific investigation will advance scientific understanding on the interaction of laser-induced shock wave with mechanical structures at nanometer scale. The new laser shock manufacturing technology will enhance the competitiveness of the US manufacturing industry in micro-system manufacturing and assembly. This award also provides new training opportunities to US students in laser technology, manufacturing, and material engineering through new course development, extracurricular activities, and community outreach.

This EArly-concept Grants for Exploratory Research (EAGER) grant provides funding for feasibility studies for the laser manufacturing of 3D silicon photonic crystals for large area solar cells. Both electrodynamic computations and experiments will be performed to explore the feasibility of nanophotonic light trapping in 3D photonic crystal photoactive regions for enhanced efficiencies in solar cells. A scalable laser manufacturing method will be developed to demonstrate preliminary results on low-cost 3D silicon photonic structures. The proposed process involves the use of laser interference lithography, chemical vapor deposition and template infiltration. This process has been simulated but not yet demonstrated for 3D silicon crystals.

If successful, the results of this research will demonstrate the proof-of-concept for a new photonic crystal solar cell structure that exhibits enhanced efficiencies and that can be manufactured at production scale and low cost. The long term goal of the research effort is to determine process-structure-property relationships for the optical absorption of laser manufactured 3D photonic crystals. The preliminary data generated here will serve as the foundation for a future study.

This grant provides funding for the integration of advanced numerical tools with laser nano-manufacturing techniques. The numerical tools, called transformation optics, will be used to calculate three-dimensional structures with pre-determined optical functions. The designed structures will be fabricated by multiple laser beam-enabled patterning techniques. The three-dimensional laser patterns will be controlled by a mini liquid crystal display (LCD) with very high numbers of pixels. The numerical information will be displayed to encode the laser beam pixel by pixel. This will enable high-precision and rapid production of nanostructures with pre-designed optical properties. A large number of functional nanostructures will be produced by rapidly changing the numerical coding information displayed on the mini LCD. The above techniques will also be used to fabricate optical circuits by adding light paths and controlling the light inside.

The results of this research will lead to improvements in the design of optical devices and the development of an advanced laser fabrication capability. These new digital design and fabrication tools will enable the rapid design, verification, and fabrication of functional nanostructures and devices for telecommunication, sensing, and imaging applications. The digital display-enabled laser fabrication technique will drastically simplify the laser nano-manufacturing process and improve the process control. The single laser exposure and large-volume patterning process will reduce the manufacturing cost, making the process industrially and technically attractive. This research will also provide educational opportunities to a diverse group of undergraduate and graduate students.

DESCRIPTION (provided by applicant): An efficacious strategy for addressing problem substance use among college student drinkers is to target core risk factors. Arguably one of the most clearly documented risk factors for problem drinking among college students is impulsivity, with the relationship holding across various dimensions of impulsivity. Available evidence supports the importance of intervening with impulsivity to limit problem drinking among college students, but there are few proven treatments for any dimension of impulsivity. This notable lack may be due to the traditional view of impulsivity as an unchangeable personality trait. However, recent research suggests personality can change and is sensitive to behavior manipulation. As a result there is clear need for novel approaches targeted at core changes in the individual and their behavior patterns. Mindfulness meditation (MM) is a unique option in this direction as MM is especially useful in reducing impulsive behaviors including problem drinking, but its exact role in affecting different dimensions of impulsivity and in effecting change in problem drinking has yet to be explored. Based on evidence from recent studies, as well as our own pilot work, we hypothesize that one of the mechanisms by which MM reduces problem drinking among college students is by lessening impulsivity - moreover, the focus on changing college student problem drinking is done without any explicit focus on drinking behavior itself. The specific aims of this Stage 1 therapy development study are to: 1) modify and further develop a breathing-based mindfulness therapy (BBMT) for reducing impulsivity and problem drinking among college youth; 2) investigate the feasibility and preliminary efficacy of applying BBMT for reducing problem drinking with a pilot randomized controlled trial (RCT); 3) examine changes in impulsivity, as measured by both behavioral and self-report assessments, as one of possible mediators in the observed effect of BBMT on problem drinking. These aims will be achieved in two phases. In Phase 1 we will expand and fully develop the existing BBMT program with manuals to determine the effective treatment dosage for both problem drinking and impulsivity in an open label trial (n = 10). Using the modified treatment materials from Phase 1, in Phase 2 we will conduct a RCT comparing the effects of modified BBMT to a Supportive Counseling + Progressive Muscle Relaxation (SC + PMR) control condition (n = 36 each) on problem drinking, assessed at baseline, weeks 4 and 8, and a 3-month follow-up. Other potential mediators such as perceived stress and anxiety also will be examined in the final model. This study has great implications for reaching student drinkers who are less willing to acknowledge their drinking problems since it addresses core vulnerability (impulsivity) among at-risk students in a manner that limits stigma and may reduce resistance to change. A diverse team experienced in mindfulness, impulsivity and behavior therapy development has been assembled to conduct the proposed R34 project and prepare for a full therapy development study in the future.

Alzheimer's disease (AD) is a progressive, neurodegenerative disease that affects 5 million elderly Americans and this number is expected to triple by 2050. AD is currently the 6th leading cause of death in the United States. Despite decades of AD research, there is no cure for this deadly disease. A significant challenge in AD research is studying the mechanism that makes an ordinary protein transform from its natural, non-toxic state to an abnormal, toxic form. Often, differences in protein structure can lead to drastically altered biological activities. Unfortunately, this rapid transition between the two distinct structural identities is not well understood. Experimental evidence suggests that there are favorable molecular interactions that stabilize the abnormal form. This award supports research that aims to study the electrical interaction between two key amino acids of an important AD protein, amyloid-beta, in order to evaluate the protein's structural stability. The research will be conducted at National Taiwan University under the mentorship of Dr. Richard Cheng, whose expertise in one of the experimental techniques will be critical to the outcome of the project.

The experimental design of this basic Alzheimer's disease research integrates the specialties from both the home and host laboratories. A series of peptide structural models of amyloid-beta will be synthesized using standard solid-phase peptide synthesis followed by product purification and characterization. These synthetic peptides will incorporate fragments of amyloid-beta that are known to initiate uncontrolled aggregation which can be subsequently suppressed by a well-placed hydrogen-bond blocker. To probe the electrostatic interaction between two key amino acids (lysine and glutamic acid) of amyloid-beta, they will be systematically replaced by amino acid derivatives. The modifications should either enhance or reduce the electrostatic interaction, which can lead to structural stabilization or destabilization of these peptides, respectively. Circular dichorism spectroscopy, a specialty of Dr. Cheng, will be used to quantify the stabilizing energies. The results of this project will afford deeper insights of a key molecular interaction that can stabilize the toxic form of amyloid-beta. This information may assist other AD researchers in their own endeavors and lead to future Alzheimer's disease discoveries that will benefits society. This NSF EAPSI award supports the research of a U.S. graduate student and is funded in collaboration with the Ministry of Science and Technology of Taiwan.

Collaborative Research: Endowing nonlinear optical devices with unprecedented robustness: overcoming fabrication disorder by "topological protection" against parasitic scattering

Non-technical section of abstract:

Technology based on controlling and manipulating light affects our lives in countless ways: from the optical fibers that enable ultrafast internet speeds, laser manufacturing of automobiles, to solar cells that provide clean energy - optical devices are ubiquitous. Very often, the performance of a given device is limited by fabrication imperfections: random defects that cause unwanted scattering of light, which impedes its flow and adds unwanted noise. Investigators Rechtsman and Chen will demonstrate a method to completely suppress such scattering: so-called "photonic topological protection" of light beams. This concept, borrowed from solid-state physics (in which the goal was to protect electronic current from scattering) has already been demonstrated to work, and offers the possibility of endowing a wide class of devices with unprecedented robustness. In order to test these concepts in the lab, the investigators will fabricate waveguide arrays (a series of "wires" for light that together form a desired device) embedded in a type of glass that is particularly useful for so-called "nonlinear" optical devices. With proper design of the waveguide array, suppression of scattering will be demonstrated in multiple different devices. The implications to optical devices are clear: increased device efficiencies or cheaper fabrication costs (or both). Moreover, the authors expect their work to "shed light" on the general wave phenomenon of topological protection against scattering in many contexts, including acoustic waves, microwaves, optical waves, and even electron waves.

Technical section of abstract:

The field of "topological insulators" has captivated condensed matter physics for ten years, due to these materials' universal properties, and striking applications in spintronics and quantum computing. It was recently demonstrated that their key property -"topological protection" against scattering by disorder- could be achieved with photons in waveguide arrays with engineered linear dispersion properties to preserve edge modes.

This proposal will explore the nonlinear optical properties of Photonic Topological Insulators (PTIs). Through the fabrication of high quality PTI waveguide arrays in nonlinear optical substrates such as chalcogenide glass, this research project will explore a nonlinear properties of edge modes and their potential applications. Since PTIs have a fundamentally different dispersion, a novel understanding of nonlinear optics in these structures is bound to yield new scientific knowledge and device applications, which will be of great interest to a highly cross-disciplinary set of intellectual communities.


The activities of this project are: (1) theoretical work to analytically and numerically model nonlinear effects (i.e., modulation instability and solitons) in photonic topological systems; (2) fabrication (laser-written photonic crystal-type structures) in chalcogenide glass, which has a high nonlinear response; (3) characterizing the structures by injecting high-peak-power near-infrared light and observing spatial diffraction patterns.

The collaboration between PI and co-PI with complementary expertise will enable the success of the proposed project from theoretical studies to device fabrication to characterization. If successful, photonic topological protection can potentially be used to dramatically improve the performance of optical devices such as multiplexing systems, all-optical switches and beam-shaping systems - and indeed any optical application limited by fabrication disorder.

The science describing the interaction between light and matter has produced a wide variety of technologically important applications that our society has come to rely on (for example, fiber optics that form the backbone of the internet, lasers used in industries ranging from telecommunications to manufacturing, solar cells used for sustainable energy, and many others). For decades, researchers have been trying to increase the strength of coupling between light and matter by engineering artificial dielectric structures (like silicon or glass) to be in resonance with incoming light. Nearly all such structures have been patterns that are periodically repeating in space: a kind of microscopic scaffolding. One of the principal goals of this project is to show that certain non-periodic structures with no repeating units can facilitate stronger light-matter coupling than periodic designs. This could open a new design principle for light-matter interaction and lead to applications like more efficient lighting, solar cells, or even components for optical quantum computers.

The principal investigators will engineer photonic structures (both waveguide arrays in silica and photonic crystals in silicon) to have Dirac points in their band structure. These structures will be "strained" (either imparting physical strain or by fabricating artificially-strained structures) in such a way that they become aperiodic and experience a "pseudomagnetic field." This pseudomagnetic field causes the eigenvalue spectrum to become highly degenerate, leading to a large density-of-states, which in turn causes stronger light-matter coupling (Purcell enhancement). This project is a cross-disciplinary endeavor of an engineer, whose contribution is through fabrication and characterization of optical media (Kevin Chen, University of Pittsburgh), a physicist (Mikael Rechtsman, Penn State), who will perform optical experiments and modeling and an applied mathematician (Michael Weinstein, Columbia), who will co-develop mathematical PDE / discrete models and analyze these in collaboration with Rechtsman and Chen. Each of their expertise will be essential for the project's success.

The goal of this project is to design algorithms and statistical tools to build complex probabilistic models from massive quantities of data in a computationally efficient manner. This work is motivated by an important current problem in genomics, namely comparative epigenetics. While every cell in an organism has the same DNA sequence, epigenetic marks on the genome are known to be highly correlated with variation between cells. A pressing question in biology is to compare the epigenetic marks across different cell types to understand these differences. While massive amounts of data has been generated for this purpose, there is a great need for computational tools that can operate on this data and provide biologically meaningful solutions. This work will thus advance the state-of-the-art in the analysis of large complex data sets and advance the field of epigenomics. The broader impact of the work includes organizing workshops and tutorials at machine learning and bioinformatics venues, involving undergraduate students in research, and releasing open source software for the community.

Specifically, this project will focus on spectral learning, which has recently provided principled and computationally efficient methods for learning parameters of probabilistic graphical models. While spectral learning methods are known for some simple latent variable models, a major barrier to realizing the potential of spectral learning in real-world applications is the lack of associated statistical tools such as regularization and hypothesis testing that connect these methods in a principled manner to end-to-end application frameworks. This project proposes to develop such statistical tools by integrating modern spectral learning with the classical statistical literature in econometrics on Generalized Method of Moments. The project proposes to formulate the statistical generalized method of moment procedures for complex graphical models in the context of spectral learning as constrained optimization problems and proposes ways of solving these problems. Finally, the novel algorithms developed will be directly applied to model epigenomics data sets from the ENCODE and Roadmap Epigenomics Projects to yield methods that can operate on the massive quantities of data and provide biologically meaningful solutions. These algorithms and software have the potential to have a widespread impact on the understanding of complex human diseases such as cancer and mental disorders. This will provide a basis for designing therapeutics for these diseases and advance society towards a future of Personalized Medicine.

The broader impact/commercial potential of this I-Corps project will further develop new digitized manufacturing schemes, new materials and structures to construct compact laser photonic systems. It will open new innovation and product opportunities. The technology has potentials to yield robust and ultra-lightweight laser photonic systems with superior thermal management performance, which can be digitally manufactured at much lower cost than conventional means. The innovation in manufacturing digitization and utilization of new materials and structures will allow rapid design modification and radical design innovation in developing laser and photonic systems for wider deployments on mobile drone platforms for a wide array of industrial, consumer, environmental, and military applications.

This I-Corps project will evaluate several additive manufacturing process using both ceramic and metal powder feedstocks to build laser systems. The technology exploits the flexibility of the bottom-up manufacturing schemes to produce entire laser photonic systems made of flexure, cellular structures with embedded cooling and sensing functions. It will lead to drastic reduction on labor cost in manual assembly and alignments. Through combined optical, mechanic, and thermal design optimizations, we intend to completely digitize the manufacturing of laser photonic systems with advantages in weight, size, thermal, mechanic performance, manufacturing costs, which are unattainable by current commercial products.

Project Summary Alzheimer?s Disease (AD) is a devastating neurodegenerative disorder and a major public health crisis, currently affecting over 5.8 million Americans and expected to rise as the population ages. Positron emission tomography (PET) imaging can identify the hallmark proteinopathies of AD, including amyloid protein plaques and neurofibrillary tangles (composed primarily of tau protein) accumulating in the brain. While there is evident need for more PET neuroimaging, for example, to elucidate the sequence of amyloid and tau deposition in preclinical AD, its increased utility in longitudinal imaging studies with large study populations is limited by recruitment and cost. In particular, making multiple visits to the scanning site will be difficult for participants living far away, and the high cost of injected radiotracers will limit the scalability of PET studies. In this project we propose using deep learning-based convolutional neural networks (CNNs) to enhance ultra-low-dose amyloid and tau PET for imaging AD. Our specific aims are (1) to validate the diagnostic value of the CNNs in actual ultra-low-dose amyloid and tau imaging sessions, with the injected dose as low as 1% of the original, and with actual ultra-low-dose data, to validate simulations for use in subsequent aims and future studies; (2) to apply the ultra-low-dose CNN to data collected on other PET systems and tracers, in order to demonstrate the CNN?s generalizability; and (3) to evaluate the value of deep learning-aided ultra-low-dose amyloid and tau PET for tracking cognitive decline in a preclinical AD population. The innovation of this work lies in using multimodal imaging in addition to advanced machine learning techniques to enable acquisition of diagnostic-level PET images at extremely low dose levels. Performing actual ultra-low-dose PET acquisitions is also highly novel in itself. The outcome of this proposal is removing the limiting factors to large-scale clinical longitudinal imaging, shortening acquisitions spanning multiple days and visits to several hours in one visit with a successive ultra-low-dose and full-dose dual-tracer scan protocol. Significant dose reduction can also be achieved, allowing for more frequent amyloid/tau PET scanning. This flexibility will not only increase the utility of PET, aid longitudinal studies in dementia, but enable future comprehensive imaging of multiple PET-based biomarkers as these tracers are being developed.