Vladimir M. Shalaev, Ph.D. - US grants

In this project, optical properties of nanomaterials with different structures will be theoretically studied. The fundamental problem to address is how the symmetry of a nanostructured material influences its optical properties and, related to this, what geometrical structure should be chosen for best performance of the material. We specifically focus on metal-dielectric crystals and composites that can support various plasmon modes, resulting in strongly enhanced optical responses. In our research we particularly consider local optical phenomena that occur in sub-wavelength, nanometer-sized areas of the material.

We plan to study photonic crystals made of periodically structured metal, which we refer to as i) plasmonic crystals. The goal here is to develop robust band-gap materials, with large and scaleable gaps in the visible and near-infrared. Because of large and negative permittivity of metals, they are intrinsically gap materials and can dramatically improve performance of photonic band-gap crystals and ease their fabrication. By employing the skin effect that expels light from metal, losses can be dramatically decreased, which is a major foe for metals. By taking control of losses we hope to open new avenues for various applications of plasmonic crystals in photonics.

By combining plasmonic crystals with submicron-sized resonators made of nearly percolating composites, we will develop ii) left-handed materials in the visible and near-IR, which have a negative refractive index in this spectral range. The plasmonic mesh-like crystals, in this case, can provide negative permittivity, whereas the composite resonators lead to negative permeability. Such material with simultaneously negative permittivity and permeability should have negative refraction. Another possibility for developing left-handed materials, which we also plan to explore, is based on periodical arrays of metal needles. The left-handed materials have unique optical properties and can find a number of novel applications, for example for developing super-lenses, which are capable of perfect image reconstruction.

In these projects we also plan to study iii) light-managed extraordinary optical transmittance through an optically-thick metal film. This new idea stems from our recent theory that has successfully explained the earlier observed extraordinary transmittance through subwavelength hole arrays. Because of the optical Kerr nonlinearity of a film, the interfering light beams can result in a periodic modulation of the refractive index in the film. This modulation can act as a periodic "hole array," created by light itself, allowing the extraordinary light transmittance through the film. This idea, when developed into a theory, can open new avenues for manipulating light with light and for developing all-optical transistors, switchers, and modulators.
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In this project, optical properties of nanomaterials with different structures will be theoretically studied. The fundamental problem to address is how the symmetry of a nanostructured material influences its optical properties and, related to this, what geometrical structure should be chosen for best performance of the material. We specifically focus on metal-dielectric crystals and composites that can support various plasmon modes, resulting in strongly enhanced optical responses. In our research we particularly consider local optical phenomena that occur in sub-wavelength, nanometer-sized areas of the material.
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This proposal was received in response to Nanoscale Science and Engineering initiative, NSF 01-157, category NIRT. This project is aimed at developing new classes of metal-dielectric nanostructured materials and their applications in photonics, spectroscopy and optoelectronics. Metal nanostructures are capable of supporting various plasmon modes, which can result in high local fields and thus in dramatic enhancement of optical responses. Such plasmonic nanostructures act like nanoantennas accumulating and building up the electromagnetic energy in small nanometer scale areas. The dramatic enhancement of optical cross-sections resulting from such energy concentration opens new avenues for numerous applications of metal nanostructures. A number of new phenomena and their applications in photonics and optoelectronics will be studied in this project. Those include negative refraction in left-handed materials based on metal nanowires, photonic band-gap materials using metal nanostructures, plasmon-enhanced nonlinear photodetectors, disorder-induced localization of plasmons and fractal sensors for detecting molecules, light-gated optical transmitters, photonic nano-circuits and nano-chips. This interdisciplinary research brings together experts in the physics of plasmonic nanomaterials (Prof. Shalaev), femtosecond pulse-shaping spectroscopy and ultafast photonics (Prof. Weiner), and fabrication of plasmonic (Prof. Wei) and optoelectronic (Prof. Melloch) nanomaterials. A successful program in plasmonic nanomaterials, supported by synergistic activities with the Birck Nanotechnology Center and Center for Sensing Science and Technology at Purdue, will accelerate the development of a multidisciplinary Nano-photonics Program. The proposed research will integrate and infuse cutting-edge research in the emerging areas of photonics and nanotechnology with top-flight education and training.

This is a Small Grants for Exploratory Research (SGER) award. It is in response to the "Next Generation Chemical and Biological Sensors and Sensing Systems" Dear Colleague letter, NSF-02-112. In this project, novel nanostructured fractal and fractal-microcavity sensors will be fabricated. These sensors are expected to provide unsurpassed sensitivity in optical detection of molecules in minute quantities, including small amounts of biological and chemical agents. The sensors are based on fractal metal-dielectric composites, which can support various plasmon modes resulting in giant enhancement of optical responses. Plasmon modes in fractal materials experience localization so that the electromagnetic energy is accumulated and concentrated in nanometer-scale areas, "hot spots," leading to the strongly enhanced local fields. The resonating areas, hot spots, can act as nano-antennas with different resonance frequencies. Combining the energy-concentrating effects from localized optical excitations in plasmonic nano-resonators with micro-resonators based on dielectric cavities, can result in record-high enhancement of optical phenomena. This research could lead to new optical sensors with unsurpassed sensitivity. The proposed research, supported by synergistic activities with Center for Sensing Science and Technology at Purdue will integrate cutting-edge research in sensor science and technology with top-flight education and training.

This is a Small Grants for Exploratory Research (SGER) award. It is in response to the "Next Generation Chemical and Biological Sensors and Sensing Systems" Dear Colleague letter, NSF-02-112. In this project, novel nanostructured fractal and fractal-microcavity sensors will be fabricated. These sensors are expected to provide unsurpassed sensitivity in optical detection of molecules in minute quantities, including small amounts of biological and chemical agents. The sensors are based on fractal metal-dielectric composites, which can support various plasmon modes resulting in giant enhancement of optical responses. Plasmons represent collective oscillations of electrons in metals and metal-dielectric composites and they are known to be a major reason for surface-enhanced spectroscopy, in which plasmonic nanostructures lead to many orders of magnitude increases in the sensitivities of optical spectroscopies. Plasmon modes in fractal materials experience localization so that the electromagnetic energy is accumulated and concentrated in nanometer-scale areas, "hot spots," leading to the strongly enhanced local fields. Combining the energy-concentrating effects from localized optical excitations in plasmonic fractal modes with micro-resonators based on dielectric cavities can result in record-high enhancement of optical phenomena. This research can eventually lead to developing new optical sensors with unsurpassed sensitivity. The research, supported by synergistic activities with the Center for Sensing Science and Technology at Purdue will integrate cutting-edge research in sensor science and technology with top-flight education and training.

Nontechnical Description: Plasmonics has demonstrated a unique capability to bridge photonics and electronics and enable nanoscale devices for applications in imaging, sensing, data storage, and light harvesting that are efficient, compact, and multifunctional. However most of the demonstrated plasmonic systems fall short in meeting the unique challenges of harsh environments, particularly high temperatures, faced by chemical and oil/gas industries, aerospace, defense, etc. This project aims to discover and realize robust, ultra-compact, chip-compatible, nanoscale optical devices using plasmonic ceramic materials that operate at high temperatures and exhibit high durability. This interdisciplinary effort is expected to have a significant impact both in the fundamental science of optics and optical materials as well as in optical, terahertz and microwave technologies and to generate significant industry interest and start-up possibilities. Integrated in this project are student education, outreach activities, and the development of materials illustrating the unique properties of plasmonic materials and devices. Specifically, the research team develops an online "book" on refractory ceramics that would provide temperature dependence of the optical properties, as well as fabrication protocol and major applications. An online "book," a learning module, simulation tools and tutorials are created and made available to the global nanophotonics research and educational community via nanoHUB.org.

Technical Description: Plasmonic structures have been historically designed in the physics and electrical engineering communities based on room-temperature experimental data and the corresponding phenomenological models of bulk noble metals at room temperature. This project is designed to overcome application-specific drawbacks associated with the use of metals as building blocks of nanoscale functional plasmonic devices by replacing metals with robust, refractory plasmonic ceramic materials, particularly transition metal nitrides (TiN, ZrN, and HfN). The properties of these materials at high temperatures and their usage for plasmonic devices for applications under extreme environments are studied experimentally and via numerical simulations. The research subjects include investigation of optical properties of transition metal nitrides, in both thin-film and nanostructured forms; high-temperature stability and metal-dielectric phase transitions; and surface/interface phenomena of composites. In addition, an online handbook of refractory plasmonic ceramics is created to benefit the nanophotonics research and educational community.

Nontechnical description: The counterintuitive laws of quantum mechanics (not observable in a classical world) offer the possibility to build next generation of information processing, communication and sensing technologies capable of far outperforming present-day devices. Quantum phenomena are extremely susceptible to interactions with the environment and are generally limited to ultralow temperatures, where interactions are minimal. In stark contrast, atomic-scale defects in diamond, being sufficiently isolated from the environment, exhibit quantum properties even at ambient conditions. Consequently, such systems are ideal building blocks for creating room temperature quantum devices. However, in order to realize scalable room temperature quantum devices, it is imperative to increase the range of interaction between individual defects, while also having the control to turn the interaction on and off. This project addresses these outstanding challenges by developing a novel hybrid material platform of diamond defects interfaced with thin magnetic films, where the required long-distance and controllable quantum interaction between individual defects is mediated magnetically. The project also aims to enhance the United States' quantum engineering workforce by providing interdisciplinary training to undergraduate and graduate students at the interface of quantum physics, engineering and materials science.

Technical description: Nitrogen vacancy centers in diamond have emerged as the dominant room temperature quantum bit for building quantum technologies. However, scaling coherent coupling beyond Nitrogen Vacancy centers separated by few tens of nanometers has proven challenging. This research project aims to provide a solution to this materials challenge by demonstrating electrically tunable coherent coupling between Nitrogen vacancy qubit spins at room temperature, which are separated by near micrometer distances. For this purpose, a novel platform is proposed, where the coherent coupling between Nitrogen vacancy centers is mediated by magnons confined in electrically controlled low-dimensional magnets. The proposed platform takes advantage of two recent experimental advances, namely: (a) strong resonant enhancement of magnon-Nitrogen vacancy spin coupling, and (b) enhanced electric-field tunability of low-dimensional magnets. The resonant enhancement, in combination with the long-distance transport of magnons, allows for the possibility of mediating long range coherent coupling; while the electrical tunability of these resonances offers exciting possibility to turn the coherent coupling on and off. In particular, the project takes advantage of these previously unavailable opportunities to extend the range of coherent coupling beyond the state-of-the-art demonstrations for room temperature quantum bits, as well as, demonstrate an on-demand quantum gate functionality. The proposed research provides opportunities for technological applications, while it also offers unique educational opportunities for training the next generation of quantum technologists and scientists. Specifically, successful completion of the project provides the missing link towards building a scalable platform for quantum technologies working at ambient conditions. On the other hand, the intersection of quantum information processing and spintronics also offers new opportunities for interdisciplinary training of students and postdocs, development of new courses, and outreach to the public. For this purpose, the team proposes to leverage existing undergraduate research experience programs at Purdue, along with posting of online seminars on nanoHub (the largest online resource of nanotechnology) for dissemination to a broader community.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Nontechnical:

Developing new, environmentally friendly energy sources is one of the grand engineering challenges faced by society. Thermophotovoltaic devices convert waste heat into usable electricity and have attracted a great research interest to satify the increasing need for electrical power. Thermophotovoltaic (TPV) systems can take advantage of many energy sources, including solar energy and waste heat from fossil fuels and industrial processes. TPV systems could enable low-weight, versatile and compact electricity generators that are noiseless, low-maintenance and energy-efficient. Realizing high-efficiency TPV systems requires advancing fundamental knowledge of materials, photonics, and design. A key challenge is to optimize multi-functional TPV components and their constituent materials for stable operation under environment and extreme temperatures. This project will use artificial intelligenc (machine learning) to merge the knowledge of optical materials with advanced optimization to achieve highly efficient TPV systems. The project will create a fundamentally new, machine-learning-assisted optimization framework for the realization of advanced TPV components. This project will leverage the extended knowledge and database of tailorable optical materials and integrate machine-learning algorithms with photonic designs.

Technical:

In the recent years, there has been significant research interest in engineering the optical and spectral properties of materials through the use of photonic metasurfaces for efficient energy conversion, including thermophotovoltaics. The proposed program merges advanced photonic topology optimization with deep-learning-based inverse design methods and a comprehensive material database to unlock unorthodox optical designs for the realization of highly-efficient components for TPV applications. This effort will expand the design parameter space and incorporate machine-learning approaches to achieve the dramatic improvement of the speed and efficiency of topology optimization, as well as to build a large documented materials database. Through unconventional optical design, the program aims to develop highly efficient TPV energy conversion approaches by enhancing radiative heat transfer process. The proposed TPV device could enable unparalleled energy conversion efficiency potentially exceeding 50% by matching the emissivity of the emitter to the bandgap of commercial photovoltaic cells such as silicon, gallium antimonide, indium gallium arsenide. This approach could elevate nanophotonic designs into previously unavailable regimes and can be applied to photonic systems beyond TPV.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Photons, which are quantum particles of light, are one of the most promising platforms for the emerging quantum information science and technology (QIST) applications including quantum communication, computing and sensing. As photons travel long distances without inference and at the ultimate speed, the field of quantum photonics seeks to enable quantum devices for QIST using photons. The goal of this project is to produce quantum photonic structures and devices that can be integrated on a chip for future applications in quantum computing and communication links. As part of the effort, we will address several challenges, such as the fact that quantum states are hard to preserve, particularly at room temperatures, and that quantum systems can be limited in speed due to photons loss, that is absorption. We aim to overcome these limitations by developing meta-devices, which are nanoscale structures utilizing metallic thin films and so-called plasmonic nanoparticles that can uniquely enhance emission from quantum light sources. We will also explore the realization of hybrid devices that incorporate both meta-structures and conventional optical components. We will employ machine learning algorithms to aid in advance structure designs and quantum measurements.
Due to unique properties of photons as quantum information carriers, namely weak interaction with matter and propagation at the speed of light, quantum photonics has emerged as one of the most promising enabling approaches for quantum information science and technology (QIST) platforms. The goal of the project is to overcome fundamental limitations that conventional quantum nanophotonic structures are facing, which include slow operation, optical loss, and fast decoherence rates in matter at room temperature. This effort will address the critical need to develop efficient, low loss, ultra-fast (THz rates) and compact on-chip quantum photonic devices by investigating both theoretically and experimentally strongly enhanced, highly controllable light-matter interactions in the quantum regime in nanometer-scale plasmonic (metal-based) structures and metamaterials. This project will merge nanoplasmonics with artificial-intelligence (AI) to realize hybrid plasmonic-photonic meta-structures for room-temperature quantum systems that can operate at THz speeds and offer a small footprint and unprecedented functionality. The program objectives are to create a fundamentally new framework for realization of advanced photonic QIST components via (1) theoretical studies of quantum emitters coupled to plasmonic meta-structures; (2) demonstration of plasmonic speed-up of quantum processes and exploration of hybrid meta-structures, including single-photon sources, deterministic multi-photon gates and quantum frequency converters; and (3) development of AI-assisted design, integration and characterization of quantum devices. This program will advance the emerging QIST technologies and expected to generate a significant industry interest in the fields of quantum information and quantum sensors.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.