ECE Ph.D. Alumni and Project Scientist Milan Mashanovitch and Research Scientist Leif Johansson and co-founders of Freedom Photonics receive $1 million grant

illustration freedom photonics Freedom Photonics among three Central Coast companies to receive the newest series of United States Department of Energy grants awarded to small businesses to encourage clean energy research and technology development

Freedom Photonics, whose research and production facilities are located in Santa Barbara, prides itself on the business of energy efficiency — through computer communication. Founded in 2005 by electrical engineering PhD’s Leif A. Johansson and Milan L. Mashanovitch, the team of 25 creates photonic integrated circuits, the same technology that allow servers for sites like Google, Facebook, and Amazon to communicate with each other. “Overheating is always an issue when working with so many servers,” said Mashanovitch about the airplane-hanger-sized facilities that house the Internet’s largest. The team plans to use its $1 million grant to fund research on solving such overheating issues and also developing circuits that emit less energy. Through its research, the company continues to pave inroads for hardware used by the Department of Defense, NASA, and private companies touting fiber optic “fencing.”

The $1 million grants were awarded by the Department of Energy to businesses across the United States as part of the 2016 Small Business Innovation Research and Small Business Technology Transfer programs.

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Ultra-nonlinear Switching Kinetics of Redox-based Memristive Oxide Elements

Redox-Based Resistive Switching Memories (ReRAM), also called nanoionic memories or memristive elements, are widely considered to provide a potential leap beyond the limits of Flash (with respect to write speed, write energies) and DRAM (with respect to scalability, retention times) as well as energy-efficient approaches to neuromorphic concepts.
In this seminar talk, the ultra-high non-linearity of the switching kinetics of redox-based resistive switching devices will be discussed with an emphasis on the so-called valence change mechanism (VCM) typically encountered as a bipolar switching in metal oxides. The involved electrochemical and physical processes can be either electric field/voltage enhanced or accelerated by a local increase in temperature due to Joule heating. The analysis of the published SET switching kinetics data of VCM-type ReRAM systems showed that their nonlinearity is mainly dominated by temperature-accelerated ion hopping, controlled by the local power during the switching process. The gradual RESET transition can be explained in terms of temperature-accelerated ion movement with counter-acting ion drift and diffusion processes. It will be shown that a designated combination of oxides can significantly improve the long-term kinetics, i.e. the retention time, by tailoring the ion diffusion properties in the oxide layers.

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Building Realistic Models for Non-ideal Photonics: Process Design Kits and Novel Applications

Photonics is rapidly evolving from a pure research topic to a mature and promising technology. On the other hand, the evolution towards complex photonic circuits integrating many building blocks and functionalities poses major issues on the design and control of the functionality of the fabricated circuits. Real photonic devices are naturally affected by non-ideal behaviours due to unavoidable fabrication tolerances such as optical and thermal interactions between single devices, spurious effects, drifts of the geometry and material properties. These uncertainties prevent the realized circuits to work as expected, with performances often very different from the simulation predictions.
As a consequence, non – ideal effects must be taken into account during the early design stages to evaluate their impact on the circuit behaviour. Powerful device models combined with advanced experimental techniques and test-on-wafer approaches for data collection, stochastic and uncertainty quantification methods, are hence fundamental ingredients in the recipe for a high quality and high yield design. In this perspective, process design kits and circuit simulators offer the perfect environment for the collection and exploitation of this large amount of information, paving the way to a novel approach for the design and fabrication of photonic circuits.

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UCSB Nobel Laureate Shuji Nakamura elected to Taiwan’s most prestigious academy

nakamura in the lab
Materials and ECE Professor Shuji Nakamura has been elected to Academia Sinica, Taiwan’s preeminent research institution, and is among 22 new scholars and scientists elected to the prestigious academy at its biennial Convocation of Academicians earlier this month

“I am so proud and honored to congratulate Professor Nakamura on his election to the prestigious Academia Sinica,” said UCSB Chancellor Henry T. Yang, who was himself elected to the academy in 1992. “Dr. Nakamura has forever changed the world through the impact of his LED inventions, from energy-efficient lighting and displays to optical storage to innovative medical applications, with more still to come. His election as an Honorary Academician is a testament to his global leadership in advancing the frontiers of science and technology, as well as his humanitarian contribution to our world.”

Academia Sinica collaborates with 31 research institutes across three divisions: Mathematics and Physical Sciences; Life Sciences and Humanities of Social Sciences.

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The “Music” of Light: Optical Resonances for Fun and Profit

Moore’s Law has set great expectations that the performance/price ratio of commercially available semiconductor devices will continue to improve exponentially at least until the end of this decade. But the physics of the metal wires that connect the transistors on a silicon chip already places stringent limits on the performance of integrated circuits, making their continued dramatic improvement highly unlikely. In this talk, I will introduce the basic concept of an optical resonance in a microscopic dielectric cavity in the context of the same type of spatial boundary conditions that give each musical instrument its unique sound. Then I will illustrate applications of these resonances to information technology in a variety of forms and functions using examples from my own laboratory at HPE, such as chip-scale optical networks, quantum bits based on spins in diamond, and ultrafast optical switches that could become the foundation for a new generation of optical computers. Our goal is to conduct advanced research that could precipitate an “optical Moore’s Law” and allow exponential performance gains to continue through the end of the next decade.

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Material Science for High-Efficiency Photovoltaics: From Advanced Optical Coatings to Cell Design for High-Temperature Applications

Solar cells based on III-V compound semiconductors are ideally suited to convert solar energy into electricity. The highest efficiency single-junction solar cells are made of gallium arsenide, and have attained an efficiency of 28.8%. Multiple III-V materials can be combined to construct multijunction solar cells, which have reached record efficiencies greater than 45% under concentration. III-V solar cells are also well suited to operate efficiently at elevated temperatures, due in large part to their high material quality. This dissertation explores material science to advance the state of III-V multijunction solar cells for use in concentrator photovoltaic and hybrid photovoltaic-thermal solar energy systems.

The first part of this defense will describe work on advanced optical designs to improve the efficiency of multijunction solar cells. A hybrid configuration is developed that consists of antireflective nanostructures placed on top of multilayer interference-based optical coatings. Designs that utilize this hybrid approach have near-perfect broadband and wide-angle antireflective properties, with reflection losses of just 0.2% on sapphire and 0.6% on gallium nitride for 300-1800nm light. Dichroic mirrors are developed for bonded five-junction solar cells that utilize InGaN as a top junction. These designs maximize reflection of high-energy light for an InGaN top junction while minimizing reflection of low-energy light that would be absorbed by the lower four junctions. Increasing the reflectivity of high-energy photons enables a second pass of light through the InGaN cell, leading to increased absorption and a higher photocurrent. These optical designs enhanced the efficiency of a 2.65eV InGaN solar cell to a value of 3.3% under the AM0 spectrum, the highest reported efficiency for a standalone InGaN solar cell.

The second half of the dissertation describes the development of III-V solar cells for high-temperature applications. As the operating temperature of a solar cell is increased, the ideal bandgap of the top junction increases. AlGaInP solar cells with bandgaps ranging from 1.9eV to 2.2eV are developed. A 2.03eV AlGaInP solar cell is demonstrated with a bandgap-voltage offset of 440mV, the lowest of any AlGaInP solar cell reported to date. Single-junction AlGaInP, GaInP, and GaAs solar cells designed for high-temperature operation are characterized up to a temperature of 400°C. The cell properties are compared to an analytical drift-diffusion model, and we find that a fundamental increase in the intrinsic carrier concentration, ni, dominates the temperature dependence of the dark currents, open-circuit voltage, and cell efficiency. These findings provide a valuable guide to the design of any system that requires high-temperature solar cell operation.

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Heterogeneous Integrated Photonic Transceiver on Si

The demand for high-speed and low-power consumption short-distance data links, especially for inter-chip communications for future super com, has led to great efforts to develop high density photonics integrated circuits with low cost and large bandwidth. Silicon photonic integrated circuits (PICs) 3D integrated with electronic integrated circuits promise future high-speed and cost-effective optical interconnects to enable Exascale performance computers and datacenters. For realistic intra-chip and inter-chip optical links, the bandwidth density and total power consumption are major challenges. Consequently, full integration of all photonics components on chip, including high speed modulators and photodetectors, and especially lasers, is needed for scalable and energy efficient system topology designs.

A library of functional devices has been developed on silicon with the heterogeneous integration method, including ultralow loss waveguides, arrayed waveguide grating (AWG) routers, low threshold distributed feedback (DFB) lasers, high speed electroabsorption modulators (EAM), semiconductor optical amplifiers (SOA) and photodetectors (PD) on silicon, enabling a large scale photonic integration implementation. In this work we demonstrate a high speed heterogeneous integrated circuit on silicon for chip level interconnection and network. Wavelength-division multiplexing (WDM) transceiver network was integrated on a single chip with over 400 active and passive components. With the heterogeneous integration approach, each type of device was optimized individually and show high performance in the integrated circuit. The reconfigurable photonic NoC circuit with large bandwidth transceivers promises a solution for future low cost and large bandwidth chip level interconnections.

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ECE Assistant Professor Alberto Giovanni Busetto selected Big Data Chair of the Japan-America Frontiers of Engineering

photo of alberto giovanni busettoBusetto selected as the Big Data Chair of JAFOE by the National Academy of Engineering in conjunction with the Engineering Academy of Japan

He is an Assistant Professor in the Department of Electrical and Computer Engineering and the Department of Computer Science (courtesy). He is also a member of the Center for Control, Dynamics and Computation and the Center for Bio-image Informatics.

General Research Interests: are interdisciplinary and include the areas of statistical learning, computing systems, information theory, and computational science.

Current Activities:

  • data-driven modeling
  • of complex dynamical systems for control and identification,
  • optimal experimental design
  • in computational science, engineering and personalized medicine.
  • computing and communication
  • to perform noise- and fault-tolerant information processing

The Japan-America Frontiers of Engineering aims to bring together outstanding, early-career Japanese and American Engineers from industry, universities, and other research institutions to introduce their areas of engineering research and technical work, thereby facilitating an interdisciplinary transfer of knowledge and methodology that could eventually lead to collaborative networks of engineers from the two countries.

The Frontiers of Engineering program brings together a select group of emerging engineering leaders from industry, academe, and government labs to discuss pioneering technical work and leading edge research in various engineering fields and industry sectors. The goal of the meetings is to introduce these outstanding engineers (ages 30-45) to each other, and through this interaction facilitate collaboration in engineering, the transfer of new techniques and approaches across fields, and establishment of contacts among the next generation of engineering leaders.

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The American Institute for Manufacturing Photonics (AIM Photonics) at UC Santa Barbara

AIM UCSB Director John Bowers
AIM Deputy Chief Executive Officer & ECE Professor John Bowers and ECE Electronics & Photonics faculty featured in AIM Photonics at UC Santa Barbara video

In June 2015, the Obama Administration selected AIM Photonics to lead research and manufacturing of integrated photonic technology. In collaboration with AIM lead university SUNY, UCSB is the West Coast headquarters of the public-private partnership.

AIM Photonics’ goal is to create an end-to-end integrated photonics manufacturing system in the United States and plans to bring government, industry, and academia together to better position the U.S. in the global market.

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ECE’s Dr. Deblina Sarkar receives the Winifred and Louis Lancaster Dissertation Award for Math, Physical Science and Engineering

Honors in Letters and Science recognize recipients of Dean’s award and other prizes of achievement in the sciences, social sciences, humanities and fine arts

photo of deblina sarkarFour undergraduate and four graduate students in the College of Letters and Science at UC Santa Barbara have been selected to receive awards for outstanding academic achievement.

ECE’s Deblina Sarkar, who has completed her Ph.D. in electrical and computer engineering, is the recipient of the Winifred and Louis Lancaster Dissertation Award for Math, Physical Science and Engineering. At UCSB, Sarkar was member of the Nanoelectronics Research Lab (NRL) and advised by Professor Kaustav Banerjee. She is presently a Postdoctoral Researcher at Massachusetts Institute of Technology (MIT).

Dr. Sarkar’s research, combines the interdisciplinary fields of engineering, physics and biology, aims to bridge the gap between nanotechnology and synthetic biology to create a new paradigm for computational electronics as well as to invent disruptive technologies for neuroscience.

Her doctoral research addressed one of the burning issues that plagues the Electronics Industry and threatens the environment: the exponential increase in power dissipation with technology scaling.

Sarkar’s present research focuses on understanding the brain which when decoded, can not only open up new avenues for treatment of neuronal disorders but can also transform the way electronic computations are performed today. Her ultimate aim is to augment the brain with nano-bio hybrid prosthetics to create smarter and healthier minds.

Dr. Sarkar was recognized at the 2016 Graduate Division commencement ceremony held on Sunday, June 12 on the Faculty Club Green.

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