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Design007-Jun2018

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18 DESIGN007 MAGAZINE I JUNE 2018 There are other things like schematic integ- rity, being able to model to do checks on sche- matics at the single board or multiple board level. I mean, there are just lots and lots of examples of validation that people have always thought of as a single board problem, but it naturally transfers itself up into the multi- board scenario. Shaughnessy: On multi-board design, is it typi- cally a team working on it? That seems like the best way to go, having a couple of guys work- ing on it at the same time doing concurrent design. Wiens: Yep, absolutely. There is concurrency in that left to right spectrum in the sense that you might have, say, a system engineer designing multiple blocks of multiple boards, and they may say, "Okay. I think this board is pretty much locked down. Hey, you PCB design engineers. You can start working on the schematic for this one board." After those guys have started laying down the schematic, they can hand it off to the layout guy who can start doing basic layout. This is all happening con- currently, right? It's no longer a serial process, and then the big thing is if a change is needed, if an ECO is required, initiated from one side or the other, how efficiently does it pass from one person to the next? So that's concurrency in what was tradi- tionally a serial process from one discipline to the next, but we've also enabled concurrency within disciplines. We started with layout con- currency more than a decade ago. We've since added concurrency to the rest of the core flow of things like the schematic, so design engi- neers can work concurrently. They can enter constraints concurrently. They can layout con- currently. They can simulate concurrently. Then, for multi-board we added the capabil- ity for multiple system engineers to collaborate concurrently in designing that architecture as well. It's really concurrency across multiple disciplines. Shaughnessy: It's been great talking to you, Dave. Thanks for your time. Wiens: Thank you, Andy. DESIGN007 Nanoscale patterns designed to bend, deflect and split light can now be fabricated directly on light-emitting diode (LED) surfaces using an inno- vative etching method developed by A*STAR researchers. A new fabrication scheme creates new possibilities for the facile control of light output. The light-emitting component of LEDs is a surprisingly simple structure, typically a thin layer of a dielectric mate- rial such as gallium nitride (GaN) on a crystalline sapphire substrate. Egor Khaidarov and colleagues from A*STAR's Data Storage Institute and Nanyang Technological University have now found a way to pattern GaN with nanoscale fea- tures that can control the behavior of light. "We have demon- strated that metasurface —surfaces patterned with features typically smaller than the wavelength of emitted light—can be fab- ricated directly on a stan- dard GaN-on-sapphire platform," says Khaidarov. Metasurface modifications of LEDs have been attempted in the past. These included patterning an additional layer with a very different refractive index than the underlying GaN-on-sapphire substrate to keep the light in the meta - surface layer and enhance the light-matter interactions. The resulting design, however, posed a major chal- lenge for fabrication, requiring the team to develop a precise nanofabrication procedure involving electron beam lithography and fast, high-temperature reactive ion etching. Light-bending Nano-patterns for LEDs

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