ECE Professor Kaustav Banerjee’s work on 2D materials featured in Physics Today

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Banerjee and colleagues at Harvard and Rice Universities author feature story, “Two-Dimensional van der Waals Materials,” published in the September 2016 issue of Physics Today

The article provides an overview of the physics, technology, and device applications of 2D materials including graphene and beyond-graphene 2D materials as well as their wide variety of heterostructures forming completely new materials known as “van der Waals solids”. The visionary article also discusses the prospects of employing such 2D materials for realizing layered nano- structures devices and circuits with atomic precision- a scientific dream of renowned physicist, Richard Feynman.

Professor Banerjee’s group have made seminal contributions toward advancing the understanding of 2D materials physics and uniquely exploited their properties in overcoming the limitations of conventional bulk materials (such as silicon and III-V semiconductors) for addressing power dissipation and other fundamental challenges in nanoscale transistors, interconnects and sensors. For example, a key device application highlighted in the article is a new class of transistors, the 3D/2D vertical heterostructure tunnel-field-effect-transistor demonstrated by Professor Banerjee’s group (Nature, 2015) that exhibits unprecedented low leakage currents and can switch with only 0.1 volts resulting in over 90% savings in power consumption.

Physics Today is the most influential and closely-followed physics magazine in the world, and more than 120,000 subscribers across the fields of STEM receive the publication every month. It is also the flagship publication of the American Institute of Physics that informs readers about science and its place in the world with authoritative features, news stories, analysis, and fresh perspectives on technological advances and ground-breaking research.

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Tunable Lasers with Ring-based Mirrors for Photonic Integrated Circuits on Heterogeneous Silicon-III/V

Semiconductor tunable diode lasers have application in various fields are used as sources in wavelength division multiplexing systems, as local oscillators in coherent detection schemes, and as a key component in various photonic integrated circuits. In recent years there has been increasing interest in heterogeneous silicon-III/V as a platform for photonics. Combining silicon with active III/V materials such as InP allows a higher level of integration on a single chip and allows for new types of tunable lasers to be created that utilize the strengths of both materials. This work explores the design, fabrication and measurement of several ring-based tunable lasers and their application in two photonic integrated circuits.

The first PIC is the first fully integrated two-dimensional beam-steering chip. The tunable wavelength from the laser is utilized to change the angle of emission from an output surface grating array. The second dimension of tuning is controlled by an optical phased array. Coherent light is split into multiple channels with individually tuned phases which are emitted from an array of surface gratings. By proper tuning of the phases an arbitrary beam angle can be formed from the interfering outputs of the array. Beam-steering from a fully-integrated chip is demonstrated over 23˚ x 3.6˚ with respective beam widths of 1˚ x 0.6˚, allowing for 138 resolvable points.

The second PIC is a tunable photonic microwave signal generator. This is created by heterodyning the output from two lasers on a fast photodetector and reading the beat tone at the frequency difference between them. The output frequency of the device can be shifted by tuning one of the laser sources relative to the other laser thus creating a tunable microwave source. The photodiode exhibits 65 GHz 3 dB bandwidth. Microwave signals from 1 to 112 GHz are demonstrated from a fully integrated PIC.

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Who’s new: Introducing UCSB GradPost 2016 incoming ECE graduate student Pedro Cisneros

UC Santa Barbara welcomes ​769 new graduate students into its ranks next ​week, and this group of incoming students is one of the most diverse ever. UCSB GradPost interviews Pedro Cisneros who will be joining the ECE department specializing in Communications, Control, and Signal Processing.

photo by Pedro Cisneros

Pedro was born in California and moved at a young age to Peru. His entire family is Peruvian, but he will be the third generation to earn a Ph.D. from a UC school (his grandfather ​went to UC Riverside and his father ​went to UC Davis). Pedro studied Electrical Engineering at the Pontifical Catholic University of Peru and will be pursuing a Ph.D. at UCSB in Electrical Engineering, with an emphasis on Communications, Control, and Signal Processing. Pedro explained, “Since school, I have had an equal love for math, letters, and arts. I thought of engineering as a possible way to combine those three.” He is interested in the field of Control Theory, which deals with a considerable amount of math and has a lot of theoretical work, as well as its application to biology, sociology, complex systems, and other applied math studies.

Pedro said that he is looking forward to making Santa Barbara his second home, and he is excited about both the academic opportunities and the fun activities it has to offer. Something you might not know about Pedro is that he has ​created over 27 paintings and has done four public art expositions in Peru. He also plays frontón, a Peruvian sport similar to squash, and he has a basic understanding of Quechua, an indigenous Peruvian language.

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Who’s new: UCSB GradPost breaks down 2016 incoming graduate student diversity statistics

This year is one of the most diverse years ever with the campus welcoming ​769 new graduate students. With 66 students, ECE is among the most popular disciplines and Engineering has the most with 207.

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At UCSB, there are a variety of gender identities represented in our student population. From the current demographic data we have collected on the incoming graduate student class, 52 percent of students identified as men and 48 percent identified as women. Starting with the Fall 2017 admissions cycle, all applicants to UCSB will have the option to choose among six gender identities listed on admissions forms: male, female, trans male, trans female, gender queer/gender non-conforming, and different identity. Additionally, all current UC students will be able to update their gender and sexual identity through the UCSB Registrar if they would like to.

Most of the incoming graduate students are between the ages of 22 and 30, but our youngest incoming student is 20 years old and our oldest is 57 years old. Sixteen percent are first-generation college students, and 25 percent of our new grad students identify as an underrepresented minority.

UCSB’s graduate students are coming from 45 different countries – from China to ​Chile, ​Sweden to South Africa, Mexico to Malaysia – representing nearly every continent. In fact, roughly one-third of incoming students (247, to be exact) are coming from places outside the country. Our U.S. students hail from 43 of the 50 states, but over half of them are California natives.

The most popular disciplines that our new graduate students chose were Environmental Science and Management (99 new students), the Teacher Education Program (81 new students), and Electrical and Computer Engineering (66 new students). By division, the most new graduate students are in Engineering (​207) and Mathematical, Life, and Physical Sciences (184), followed by Education (​114) and Humanities and Fine Arts (101).

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Who’s new: Introducing UCSB GradPost 2016 incoming ECE graduate student Vivek Adarsh

UC Santa Barbara welcomes ​769 new graduate students into its ranks next ​week, and this group of incoming students is one of the most diverse ever. UCSB GradPost interviews Vivek Adarsh who will be joining the ECE department specializing in communications and signal processing.

photo by Vivek Adarsh
Vivek moved around quite a bit growing up due to his father’s profession, but he spent most of his childhood in Hyderabad, India. “A new city, a new place every 2-3 years – it helped me adapt quickly and expand my comfort zone,” ​he said. “That’s one thing I’ll be carrying with me to Santa Barbara.” Vivek holds a Bachelor of Technology degree in Electrical Engineering from the University of Pune, and he’ll be joining the Electrical and Computer Engineering department at UCSB to specialize in communications and signal processing. ​He explained his research interests by saying, “Today, even though we’re using the Internet at unimaginable speeds, about 60% of the world still lacks basic connectivity, specifically developing nations. Technology in itself is futile if it doesn’t reach the masses. This is what sparked my interest in communications. I envision a future where each and every household ​has standard connectivity.”

Vivek said he is looking forward to ​UCSB’s amazing research facilities as well as the lovely beaches in Santa Barbara. He enjoys exploring new places, playing the guitar, and reading, and he also ​fancies himself a foodie. ​”I’d like to think of myself as a good cook. Well, sort of…! I tend to experiment with new elements. I try out various fusions between different cuisines.”

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U.S. News & World Report ranks UCSB number 8 among the country’s top public universities

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Within the University of California system, only UC Berkeley and UCLA ranked above UCSB

Among the “Best National Universities” ranking, which includes both public and private institutions, UCSB placed number 37. Other UC campuses in the Top 30 include Irvine, Davis and San Diego.

In addition, UCSB placed number 13 among public universities in the “Least Debt” section of the magazine’s ranking of student debt load at graduation. UCSB’s College of Engineering is ranked number 18 among public universities on the U.S. News & World Report list of “Best Programs at Engineering Schools Whose Highest Degree is a Doctorate.”

The magazine has just released its annual college rankings online at usnews.com/colleges. The print edition of “Best Colleges 2017” guidebook can be purchased online beginning today or in stores Oct. 4.

“We are proud of this national recognition, which places us at No. 8 among the country’s top public universities and further emphasizes our leading role in higher education,” said Chancellor Henry T. Yang. “A reflection of the preeminent stature of UC Santa Barbara, this ranking is the result of the dedication and enormous efforts of our world-class faculty, and the academic distinction of our diverse student body.

“Our greatness,” Yang added, “is the sum of the combined commitment of our students, faculty and staff to academic excellence, diversity, access and affordability.”

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Abusing Hardware Race Conditions to Perform Useful Computation

We propose a novel computing approach, called “Race Logic”, which utilizes a new data representation to accelerate a broad class of optimization problems, such as those solved by dynamic programming algorithms. The core idea of Race Logic is to deliberately engineer race conditions in a circuit to perform useful computation. In Race Logic, information, instead of being represented as logic levels (as is done in conventional logic), is represented as a timing delay. Computations can then be performed by observing the relative propagation times of signals injected into a configurable circuit (i.e. the outcome of races through the circuit).

In this talk I will introduce Race Based computation and talk about multiple VLSI implementations. We first begin by considering a synchronous approach, which uses simple clocked delay elements. Though this synchronous implementation outperforms highly optimized conventional implementations of the well-studied, DNA sequence alignment problem, its third order energy scaling with problem size and limited dynamic range of timing delays are its major pitfalls. Next, in the search for energy efficiency, we study asynchronous designs in order to understand the performance trade-offs and applicability of this new architecture. Finally, I will present the results of a prototype asynchronous Race Logic chip and demonstrate that Race-Based computations can align up to 10 million 50 symbol long DNA sequences per second, about 2-3 orders of magnitude faster than the state of the art.

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Low Voltage Wide Bandwidth III-V Electro-optic Modulators

Wavelength division multiplexing (WDM) along with optical fiber revolutionized the capacity and speed of data communication system and as a result, fiber optic communication systems became essential in many data communication systems. In addition, the demands for the faster data communication system has been getting higher and higher as time goes. Therefore, constant efforts have been put on improving the performance of the essential components of the fiber optic communication systems including optical modulators; optical modulators are used for converting electrical signal to optical signal. For optical modulators, among others, there are two key factors that directly contributes to the system performance; one is the driving voltage and the other is bandwidth. Drive voltage is desired to be as low as possible since it reduces power consumption by eliminating modulator driver, and bandwidth is desired to be as wide as possible to achieve faster data transfer rate.
In this work, we demonstrated a substrate removed modulator having drive voltage under 3V while showing over 60GHz modulation is possible. This modulator also shows reduction in drive voltage under reverse bias. The drive voltage goes down to 1.3V under 18V reverse bias without hurting its bandwidth. In addition, a substrate removed modulator having drive voltage of 1.55V at no external bias is demonstrated. Then, the modulator designs are further modified for the comparability to conventional foundry processing; the devices are fabricated on substrate without substrate removal. The substrate-on devices exhibit lower bandwidth although their drive voltages stay the same as substrate removed devices. However, they still provide moderately wide bandwidth, and we demonstrated in this work that they can be modulated over 20GHz.

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Deterministic Generation of a Cluster State of Polarization Entangled Photons and more…

The first part of my talk will be devoted for the recent work performed in prof. David Gershoni’s research group at the Technion, Israel institute of technology. In this research work we successfully generated a cluster state of entangled photons [1]. Photonic cluster states are a resource for quantum computation based solely on single photon measurements [2]. These measurements-based schemes are among the most fault-tolerant quantum computing architectures [3]. We used a single semiconductor quantum dot to deterministically generate long strings of polarization entangled photons, by periodic timed excitation of a precessing matter qubit, in this case the confined dark exciton [4]. Our prototype device can produce strings of hundreds photons in which the entanglement persists over 5 sequential photons.

In the second part of my talk, I will give an overview on Mellanox, which is a leading company in the end-to-end Ethernet and InfiniBand intelligent interconnect solutions, service for servers, storage and converge infrastructure. I will focus on current projects and possible future collaboration with academia regarding the future of interconnect.

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ECE Professor Pradeep Sen’s work on High dynamic range (HDR) imaging published in IEEE Signal Processing Magazine

cover of Signal Processing magazine
HDR imaging enables the capture of an extremely wide range of the illumination present in a scene and so produces images that more closely resemble what we see with our own eyes

In the article, “Practical High Dynamic Range Imaging of Everyday Scenes: Photographing the world as we see it with our own eyes,” authors Sen (UCSB) and Cecilia Aguerrebere (Duke) explain the problem of limited dynamic range in the standard imaging pipeline and then present a survey of state-of-the-art research in HDR imaging, including the technology’s history, specialized cameras that capture HDR images directly, and algorithms for capturing HDR images using sequential stacks of differently exposed images. Because this last is among the most common methods for capturing HDR images using conventional digital cameras, they also discuss algorithms to address artifacts that occur when using with this method for dynamic scenes.

Finally, they consider systems for the capture of HDR video and conclude by reviewing open problems and challenges in HDR imaging.

IEEE Signal Processing Magazine has an impact factor 6.671 and publishes tutorial-style articles on signal processing research and applications, as well as columns and forums on issues of interest. Its mission is to bring up-to-date, emerging and active technical developments, issues, and events to the research, educational, and professional communities.

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