Attojoule-per-bit acousto-optics
- Reference number
- FFL21-0039
- Project leader
- Van Laer, Raphaël Frank J
- Start and end dates
- 220801-271231
- Amount granted
- 14 800 000 SEK
- Administrative organization
- Chalmers University of Technology
- Research area
- Information, Communication and Systems Technology
Summary
Energy-efficient conversion of both classical and quantum information between the microwave and optical domains is an important engineering challenge. The acousto-optic approach using gigahertz-frequency mechanical devices can be extremely efficient thanks to the large photoelastic response found in common materials like silicon, and our ability to confine acoustic energy into a micron-scale volume. However, existing demonstrations suffer from combinations of low electro-acoustic and low acousto-optic efficiency. Here, we will overcome these challenges by combining the strongly piezoelectric material lithium niobate with the strongly photoelastic material silicon in a foundry-compatible way. We will illustrate the power of the approach with a landmark demonstration of acousto-optic modulation with dissipation at the attojoule-per-bit level. Such energy-efficient electro-optic links do not exist today. The new hardware we will develop has great potential in any situation where large amounts of data must be processed quickly and with low power consumption. This includes in datacenters and supercomputers as well as in emerging applications in autonomous vehicles, optical sensors, machine learning engines, and quantum technologies. The new hardware will be of strategic long-term value in a sustainable information infrastructure.
Popular science description
Our society relies heavily on information technologies such as computers and the internet. These technologies became increasingly powerful in what is known as Moore’s law. Today, however, demand for computing and connectivity outstrips even the most optimistic Moore’s law estimates. There is no realistic path to a sustainable growth in our capabilities to compute and connect without architectural changes in our information infrastructure. The internet’s energy consumption is of increasing concern. It is increasing at 10%/year, outpacing the average of 3%/year significantly. This implies that at the current rate the internet will overtake *all other* sources of power consumption. Indeed, companies we all rely on like Google and Microsoft spend enormous sums on cooling their datacenters and evacuating the excess heat by building their datacenters in cold climates like in the North of Sweden. A key issue is the excessive energy loss caused by communication inside a just about any modern electronic system. The communication takes up an enormous chunk of the energy budget, causing heating and greenhouse gas emissions along the way. Many scientists believe using light for communication is our only hope for solving this. Indeed, light had great success in the internet’s long-distance communication links. However, light has yet to improve short links this way. To do so, we must convert microwave electrical signals onto a light beam. This is an extremely difficult problem as the wavelength of the microwaves is about a centimeter, while the wavelength of near-infrared light is around a micrometer – a vast scale difference. In this project, we will demonstrate new hardware for bridging this gap. We will first convert the electrical signals into gigahertz sound. Next, we will convert the sound to light. Both can be done with near-perfect efficiency and ultra-low energy loss. The hardware makes use of the strong interactions between light and sound in tiny nanostructures. This will massively reduce the energy consumption of communication links. The approach would not only revolutionize how we transfer data inside the cloud and in supercomputers, but also become a key technology in any situation that requires large amounts of data to be analyzed and moved around quickly – such as in self-driving cars, artificial intelligence, and quantum computers. Our new hardware will help put us back on track of Moore’s law in a sustainable way.