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EETE DECEMBER 2012

NEWS & TECHNOLOGY ‘Antenna-on-a-chip’ speeds infrared light transmission By Dylan McGrath researchers at rice University have developed a micron- conventional integrated photonics relies on an array of scale spatial light modulator (sLM) that they say has the poten- pixels, the transmission of which can be changed at very high tial to improve the capability of optical information processing speed, Wu said. “When you put that in the path of an optical systems by several orders of magnitude. the rice “antenna on beam, you can change either the intensity or the phase of the a chip” is similar to those used in sensing and imaging devices. light that comes out the other side,” he said. But unlike other devices in two-dimensional semiconducting the rice sLM chips are essentially nanoscale ribs of crystal- chips, the rice chips work in three-dimensional “free space.” line silicon that form a cavity sitting between positively and according to Qianfan Xu, an assistant professor of electri- negatively doped silicon slabs connected to metallic electrodes. cal and computer engineering at Rice, the SLM chip differs the positions of the ribs are subject to nanometer-scale “pertur- dramatically from current state of the art technology. bations” and tune the resonating cavity to couple with incident “With this device, we can make very large arrays with high light outside. yield,” Xu said. “Our device is based on silicon and can be fabri- that coupling pulls incident light into the cavity. Only infrared cated in a commercial cMOs factory, and it can run at very high light passes through silicon, but once captured by the sLM, it speed.” Xu and his rice colleagues detailed their antenna-on-a- can be manipulated as it passes through the chip to the other chip for light modulation in Nature’s open-access, online journal side, according to Xu. The electric field between the electrodes Scientific Reports. Xu said the antennas would not be suitable turns the transmission on and off at very high speeds, he said. for general computing, but could be used for optical processing LeD screens and micromirror arrays in projectors are both tasks that are comparable in power to supercomputers. sLMs in which the mirrors rotate. But although the sLM is one In today’s computers, light is confined to two-dimensional of the basic elements of optical systems, their switching speed circuitry, tied to waveguides that move it from here to there, Xu is limited, he said. some of their switching speeds can get said. in the paper, Xu and his colleagues maintain 2-D systems down to microseconds, which is okay for displays and projec- fail to take advantage of “the massive multiplexing capability of tors. “But if you really want to do information processing, if you optics” made possible by the fact that “multiple light beams can want to put data on each pixel, then that speed is not good propagate in the same space without affecting each other.” enough,” Xu said. Ultra porous copper material up to 10 times more effective than conventional heat sinks By Julien happich versarieN has UNveiLeD a ground-breaking, micro-porous material (and its heat-transfer capabilities) while reducing heat metallic material claimed to be up to 10 times more effective at sink weight and physical dimensions compared to competing transferring heat energy than conventional micro-channel heat products for a given level of heat transfer. Depending on the mix sinks of equivalent size. and thermal treatment, pore diameters from 20 µm to 1 mm can Based on proprietary process technol- be specified, with porosity levels of up to ogy developed through metallurgy research 85%. conducted at the University of Liverpool, Currently, the material is offered in the versariencu product achieves a heat generic shapes, but the blanks can also transfer coefficient of approximately 150 to be machined to further increase thermal 200 kW/m2K. performance or to match particular casing in the patented Lost carbonate sinter- geometries. although the versariencu ma- ing (Lcs) process that is employed to terial uses copper as the metal, the process produce versariencu, copper particles are has been proven with other metals such as mixed together with non-metal particles and aluminium or titanium, explains Neill rick- compacted into a near-net shape which is etts, ceO and founder of versarien Ltd. the then baked to around 1000ºc under vacuum company is also experimenting with various to decompose the non-metal content. the profiles and surface textures to further process allows a homogeneous distribution of micro-fine pores extend the porous material’s use cases. in the future, this could throughout the copper base material, with an open cell porous yield new package designs for power ics or LeD lighting, to metal structure, dramatically increasing the surface area of the name a few applications. 8 Electronic Engineering Times Europe December 2012 www.electronics-eetimes.com


EETE DECEMBER 2012
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