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Advancing Photonics Capabilities

In July, Vice President Joe Biden announced a new national institute for integrated photonics. The Institute, to be headquartered in Rochester, N.Y., is part of the federal government’s National Network for Manufacturing and Innovation.

Historic Announcement

Vice President Joe Biden and New York Gov. Andrew Cuomo announced the $600 million public-private partnership on July 27. The federal government pledged $110 million for the Institute under the federal government’s National Network for Manufacturing and Innovation (NNMI) with another $500 million coming from a consortium of state and local governments, corporations, universities, community colleges, and nonprofit organizations across the country.

AIM Photonics will be led by the State University of New York Polytechnic Institute (SUNY Poly). RIT; University of Rochester; Columbia University; MIT; University of California at Santa Barbara; University of California, Davis; and University of Arizona are the other Tier 1 academic partners with a total of 20 universities and 33 community colleges involved. Top industry partners include IBM, Cisco, Intel, General Electric, and HP. The U.S. Department of Defense, U.S. Department of Energy, NASA, and New York state are just some of the government partners. The establishment of the NNMI in photonics is to better position the United States as a global leader in the manufacturing of integrated photonics.

What is Integrated Photonics?

Integrated photonics is the intersection of microelectronics and photonics. Microelectronics (design and fabrication of electronic devices, systems, and subsystems using extremely small components) has been the driver of technology and the world’s economy for several decades. Its success is a direct result of the integrated circuit where billions of electrical components (transistors, wires, resistors, capacitors, etc.) are seamlessly integrated together on silicon wafers using manufacturing processes that have followed the scaling trends of Moore’s law.

Photonic technologies are now at a point similar to where microelectronics was in the early 1970s—where just a relatively small number of components were tediously integrated together. By leveraging the manufacturing equipment and techniques that made microelectronics a success, it is now beginning to be possible to realize the same economies of scale to make integrated photonic circuits. Since similar manufacturing technologies are being used, photonics and electronics can be directly integrated together to make both the electronic and photonic elements of the circuits function better—not only reducing size, weight, and power but enabling entirely new applications, many of which have not been envisioned.

In order to understand how integrated photonics works, it is important to first define the broader area of photonics which is the study of the generation, manipulation, and detection of light. Light is made up of photons, similar to how electric current is made up of individual electrons. However, photons have the distinct advantage that they travel at the speed of light and don’t consume any power during their propagation. For example, photons routinely travel across the entire universe (albeit after approximately 13 billion years) with just the energy required to initially produce them. Photons are also very efficient information carriers. They are electromagnetic waves (just like a radio wave) that oscillate at very high frequencies, and as a result can easily encode terabytes/second of information in their amplitude, phase, and/or polarization.

There have been many platforms for photonics over the decades, such as fiber optic networks, where discrete components (lasers, the actual fiber optic cable that transmits light, and detectors) are separately manufactured and put together.

In the early 2000s the promise of silicon as an integrated photonics platform emerged. It is ideal for manufacturing since silicon wafers are also used to make the vast majority of integrated electronic circuits. Early on, though, it was not clear how well silicon would work for photonics. But after multiple breakthroughs over the past decade it’s proven to excel at controlling light. Specifically, silicon is excellent at guiding light in “photonic wires,” known as waveguides, because it has a very high refractive index that tightly confines light and easily supports total internal reflection—even for a ~90-degree bend.

Consequently, it is possible to realize very complex integrated photonic circuits that are now rapidly growing in density. Furthermore, silicon is transparent at the same wavelengths used for fiber optics, enabling direct interfacing of silicon photonic chips with optical fibers, which is key for many applications.

However, for silicon to be the integrated photonics platform of the future, it also needed the ability to generate, control, and detect light.

Silicon itself is not ideal in these roles as it is an indirect bandgap semiconductor. In contrast, many III-V semiconductors (named from the groups on the periodic table), such as gallium arsenide and indium phosphide, are direct bandgap semiconductors and can easily be made into lasers. Fortunately, it is now possible to bond or even grow III-V lasers directly onto silicon through advances in manufacturing technology. III-Vs can also be used to detect light, but the most commonly used detector material is germanium, because it is straightforward to grow on silicon and is already used to make silicon transistors operate faster while using less power.

It is now possible to also actively encode information on light by combining photonics and microelectronics. Light is Photonic Wafer: A working integrated photonic wafer made by RIT researchers. It contains thousands of integrated photonic devices including waveguides, filters, fiber-chip couplers, modulators, and more. These devices will make computers, Internet communications, and sensors operate at a much higher performance and at a much lower cost than what is available today. 8 Spring/Summer 2015 Research at RIT 9 Focus Area | Harnessing Light sensitive to the same electrons and holes that microelectronic devices excel at controlling. Specifically, free-carriers change the refractive index and absorption of silicon. As a result, by combining silicon photonic waveguides with PN diodes it is possible to change the transmission of the light electrically. These electro-optic modulator devices are now able to switch the light on/off at staggeringly high rates of greater than 40 GigaBits/second, while using incredibly low amounts of energy of less than 1 femtoJoule and have the potential to approach the same energy used by just a few state-of-the-art transistors.

With all of the key components now in place the potential of silicon photonics is enormous. In just the last few years the number of devices that have been integrated together has rapidly grown to over 10,000. The natural application of these integrated photonic circuits is high bandwidth communications, particularly since data centers are expected to consume a few percent of the entire power generated in the United States and a vast majority of that power usage is used to simply move data around. Consequently, the integration of all of the previously used discrete components onto silicon photonic chips will yield dramatic reductions in power along with orders of magnitude improvements in bandwidth.

Challenges remain, however, with the biggest being the ability to costeffectively package photonic chips. Packaging currently accounts for most of the cost because optical fibers must be precisely positioned to the waveguides using time-consuming procedures. However, solutions based on microfabrication are now being realized and will dramatically improve packaging throughput and reliability.

 

RIT’s Role and Assets

Packaging photonic chips will be one of RIT’s main roles in standing up the Institute. RIT will work with AIM Photonics to establish a manufacturing center for packaging integrated photonics systems in Rochester with the help of RIT’s Center for Electronics Manufacturing and Assembly. As part of AIM Photonics, RIT will also produce III-V lasers and detectors for integration with the multiproject wafers produced at SUNY Poly’s College of Nanoscale Science and Engineering. RIT recently acquired a metal organic vapor-phase epitaxy system (MOVPE) in the university’s clean room facility, the Semiconductor and Microsystems Fabrication Laboratory (SMFL). Among its many uses, the MOVPE will be used to grow III-V lasers that will be integrated onto silicon photonic wafers.

RIT will also support education and workforce development, leveraging its longstanding degree and training programs. The university has contributed to advances in the design, fabrication, and manufacturing of electronic and photonic devices for more than 30 years as technology has progressed from the micron-scale to the nano-scale. RIT created the nation’s first bachelor of science microelectronics program specializing in the fabrication of semiconductor devices and integrated circuits. The bachelor’s degree launched in 1982 and RIT began its microsystems engineering Ph.D. program in 2002.

“I’m tremendously excited that this effort has come to upstate New York and specifically to Rochester,” said Ryne Raffaelle, RIT vice president for research and associate provost. “It will allow RIT to leverage its heritage in research and workforce development in photonics and microelectronics to play a major role in the integrated photonics revolution.”

Photonics Applications

The photonics revolution is akin to the improvements seen in computers, where cell phones now have the same performance as the discrete-component supercomputers that took up entire warehouses decades ago.

Silicon photonics is also likely to lead to many new applications, some of which can be imagined now. Circuits are already being developed for processing analog radio-frequency signals, particularly for the frequencies ranges that are difficult to control electrically. These are likely to yield ultra-stable oscillators, analog communication systems, or highsensitivity Terahertz imagers (like the ones currently used in airports but with improved sensitivity). It is also possible to steer light beams emitting from the chip by controlling the relative phase of the light (e.g., phased arrays), which will be particularly useful to robotics or self-driving cars. Photons can also be used to realize sensors that, when implemented with other biological or chemical technologies, can be used to detect minute changes in the environment, which will benefit fields from health care to security. And one of the ultimate goals of photonics has always been to realize an optical computer. While this still remains very far off due to limitations of photons (they do not interact strongly with each other), there are future computing technologies that photons may benefit, such as quantum computing.

The applications for integrated photonics are endless and will have direct impact on future supercomputers, improved health care, faster telecommunications, and longer lasting cell phones. As the integrated photonics efforts in the Rochester region ramp up, there will be tremendous opportunities for research, innovation, education, and commercialization.

RIT a Key Player in Four of the Nation’s Manufacturing Initiatives

RIT is currently contributing work to four of the National Network for Manufacturing Innovation (NNMI) Institutes.

In 2012 President Barack Obama announced the NNMI—an initiative focused on bringing together government, industry, and academia to advance U.S. leadership in manufacturing. There are seven Institutes to date. In addition to AIM Photonics, RIT is part of the NNMI consortia on flexible electronics (Flex Tech Alliance), additive manufacturing (America Makes), and digital manufacturing (Digital Manufacturing and Design Innovation Institute or DMDII).

RIT’s Golisano Institute for Sustainability (GIS), led by Nabil Nasr, associate provost and director of GIS, is part of the DMDII, drawing on its extensive expertise and research in the advanced manufacturing and sustainable manufacturing areas. In addition to strengthening the nation’s manufacturing, the Institute also supports improvements to Department of Defense effectiveness, including integration of design data across product lifecycles and reducing manufacturing costs and development time.

RIT’s contributions to the Flex Tech Alliance are led by Denis Cormier, the Earl W. Brinkman Professor of Industrial and Systems Engineering, and Shu Chang, the Melbert B. Cary Jr. Distinguished Professor in RIT’s College of Imaging Arts and Sciences. Cormier’s research is on printed electronics, specifically the synthesis of printable nanoinks, the development or enhancement of printing processes, and the design of novel printed electronic devices. He also is an expert in the area of additive manufacturing and multifunctional printing. Chang’s research identifies techniques to bridge the system and material aspects of conventional digital printing to the rapidly growing field of additive manufacturing.

On The Web

RIT Nanophotonics Group
http://www.rit.edu/kgcoe/nanophotonics

Semiconductor & Microsystems Fabrication Laboratory
http://www.smfl.rit.edu

NanoPower Research Laboratory
http://www.rit.edu/gis/research-centers/nanopower