Data centers dedicated spaces for data storage, processing and distribution enable everything from computer cloud to video streaming. In the process, they use a large amount of power to move data back and forth in the center. With increasing data demand, there is a growing pressure for data centers to use more power. In-house data servers, high-powered computers speak to each other through connections, which are visual links that allow data exchange. Another way to reduce power consumption in data centers is to use light to communicate information with optical-powered optical switches that control light, as well as information, between servers. These tangible changes require them to use a lot of resources and save energy to support the continued expansion of data centers.
Scientists have reported the design of an energy-efficient voice dial, based on a fixed silicon that controls light using a phase switch and a graphene heater. Arka Majumdar, UW’s associate professor of physics and electrical and computer engineering, and a member of the UW Institute for Nano-Engineered Systems and the Institute for Molecular & Engineering Sciences. “Compared with what is currently being used in data centers to control photonic circuits, this technology will significantly reduce the energy needs of data centers, making them more resilient and environmentally friendly.”
Silicon photonic switches are widely used in part because they can be made using well-established semiconductor techniques. Traditionally, these changes have been attributed to the effect of heat, a process in which heat is applied more frequently than metal or semiconductor current to alter the optical properties of an object in a transition and thus change the light path. However, not only does this process save energy, but the resulting changes are not permanent. As soon as it is currently removed, the asset returns to its original state and the connection and flow of information is broken.
To address this, the team, which includes researchers from the University of Stanford, Charles Stark Draper Laboratory, University of Maryland and the Massachusetts Institute of Technology, has developed a “set and forget” button that can keep connections without additional power. They use a flexible phase changer, which means that the material is slightly heated, and stays in that position until it receives another drive, at which point it returns to its original position. This eliminates the need for constant power supply to maintain the desired condition.
Earlier, researchers used doped silicon to heat up phase-changing substances. Silicon alone does not transmit electricity, but when applied selectively with various substances such as phosphorus or boron, silicon is able to both conduct electricity and distribute light without excess absorption. When the current is pumped with doped silicon, it can act as a heater to change the position of the switching material on it. The irony is that this is also not a energy saving process. The amount of power required to replace a piece of equipment is the same as the amount of power used by traditional thermo-optic switches. This is because the entire silicon layer of nanometer (nm) 220 thickness must be welded to convert only 10 nm of phase-changing material.
A lot of energy is wasted to heat such a large amount of silicon to change the very small volume of phase-changing material.” We have seen how we need to figure out how to reduce the volume that needs to be heated to improve the efficiency of the switches,” said lead author and co-author Zhuoran (Roger) Fang, a UW student in electrical and computer studies. engineering. Another option is to make a thin silicon film, but silicon does not distribute light well when thinner than 200 nm. So instead, they used an unmixed silicon layer of 220 nm to disperse the light and introduce a layer of graphene between the silicon and the phase switches to conduct electricity.
Like iron, graphene is a high-performance electrical conductor, but unlike iron, it is thin atom and contains just one layer of carbon atoms arranged in a double helix chain. This design eliminates waste energy by directing all graphene-generated heat to achieve significant transformational changes. In fact, the density of the switching power of this set, which includes taking the power dissipation divided by the volume of the switch, is only 8.7 attojoules (aJ) / nm3, a 70-fold reduction compared to the widely used doped. silicon heater, current state of the art. This is also within one order of the maximum size limit for changing power density (1.2 aJ / nm3).
Even if the use of graphene for electrical conduction causes some loss, which means that some light is drawn, the graphene is so small that not only the loss is small, but the phase-changing material can still interact with the increasing light in the silicon layer. The team found that a graphene-based heater could reliably change a phase change condition over 1,000 cycles. This is a remarkable improvement over water-based silicon heaters, which have only been shown to withstand about 500 cycles of rotation.” Even 1,000 is not enough,” Majumdar said. “As we speak, we need the patience of a billion cycles, on which we are currently working.” Now that they have shown that light can be controlled using a phase changer and graphene heater, the team plans to show that these changes can occur. used for visual control of information about device network.
Source Journal Reference: Zhuoran Fang et al, Ultra-low-energy programmable non-volatile silicon photonics based on phase-change materials with graphene heaters, Nature Nanotechnology (2022). DOI: 10.1038/s41565-022-01153-w
