HOT
The EU project HOT is part of the research in this sector. The project is coordinated by Tobias Kippenberg, professor of Physics at the École Polytechnique Fédérale de Lausanne and supported by the Future and Emerging Technologies (FET) Proactive programme since 2017.
The development of information and communication technology (ICT), which pervades today’s society, largely relies on the ever-increasing ability to define and control isolated physical systems at the micro- and nano- scale, and to make them interact in a controlled manner. Examples include magnetic hard-disks, micro-electronics or micro-electromechanical systems (MEMS) that have become omnipresent in consumer products, such as mobile phones, cars or healthcare products. Likewise, integrated photonic technologies are transitioning to the market and are becoming an integral part of communication and data-centric technology.
The HOT consortiumis performing research that lays the foundation for a new generation of devices, which connect or even contain several platforms at the nanoscale in a single “hybrid” system.
As hybrid interfaces, they will allow the exploitation of the unique advantages of each subsystem within a nano-scale footprint, while as integrated hybrid devices they will enable entirely novel functionalities. An entirely novel concept in this regard is the coupling of micromechanical oscillators to both optical, microwave and radio wave fields, as first studied a decade ago in the field of optomechanics.
Micro-mechanical resonators in today’s world
Micro-mechanical resonators are devices that similarly to music instrument, such as strings or drumheads, exhibit vibrations at specific frequencies. Yet, in contrast to their macroscopic counterparts, such micro- and nanomechanical devices are micron-scale, fabricated using semi-conductor processing techniques. They can sense force, acceleration, mass or provide timing information. Indeed, micromechanical oscillators, thanks to investments from the US-based Defense Advanced Research Projects Agency (DARPA) in the 80s, are today part of virtually all modern communication and navigation devices.
Due to the high mechanical Q-factor (i.e. quality factor, which describes how oscillation of resonators and oscillators pass), they present low mechanical dissipation and slow propagation of mechanical vibrations compared to the speed of light, which make it possible to create extremely compact filters based on mechanical oscillators.
Such wireless filter technology, that uses mechanical vibrations, are part of every cell phone in order to process the microwave signals used for communication. Likewise, mechanical oscillators can sense acceleration or rotation: this is used in virtually every cell phone or car today. Not to mention, that Europe has several largescale players such as Bosch or ST microelectronics that have more than 4 billion MEMS sensors built into consumer electronics.
Micromechanical oscillators are also exquisitely sensitive – and used at the nanoscale in atomic force microscopy and spin detection, and for gravitational wave detection on the macro-scale. This exquisite sensitivity due to low dissipation (i.e. high Q factor) of mechanical oscillators is providing also new capabilities in emerging quantum technologies. Mechanical oscillators have been shown to allow ultra-sensitive measurements of electromagnetic fields, relevant radio-wave detection, or can provide self-calibrated quantum noise thermometers on a chip.
They are also the basis for ‘quantum interconnects’, i.e. converters capable of translating quantum signals from superconducting devices in the microwave domain to optical signals that can be transported over optical fibre. Moreover, superconducting qubits (basic units of quantum information) are actively investigated to be coupled to mechanical vibrations as manipulation and readout element.
The future of optomechanical technologies
The potential of hybrid optomechanical technologies is solidly rooted in academic research on nano-optomechanical systems, in which Europe has taken a leading role (for more information see a study on Cavity Optomechanics). Indeed, in just 10 years, an entirely new paradigm for how to measure and control micro- and nano-mechanical oscillators using electromagnetic (radio frequency, microwave and optical) fields has emerged. Radiation-pressure-based coupling, un-observable on the macroscopic scale, is dramatically enhanced at the nanoscale.
The past decade has been focused on and produced staggering progress in basic science; reported landmark achievements include laser cooling to the mechanical ground state, quantum coherent coupling, and measurements of motion at and beyond the standard quantum limit.
Theoretical and experimental studies indicate the significant technological potential that such hybrid opto- and electromechanical systems could unlock: For example, they provide methods for optically detecting radio waves via nanomechanical motion.
First compact transducers (devices that convert energy from one form to another) have proved to be capable of measuring radio wave fields with optical fields. Such devices can operate in large magnetic field and therefore makes them ideal candidates for magnetic resonance imaging (MRI) – Indeed, first prototypes using hybrid optomechanical technologies have shown to have significant potential as next generation MRI pick-up coils for medical imaging.
Other areas of interest are conversion of microwaves or THz radiation (so-called T-rays, or electromagnetic radiation between microwave and far infrared band) to the optical domain, which is of relevant for radio-wave astronomy, classical sensing and imaging, but equally future quantum computing schemes to convert stationary qubit signals into propagating ones.
The operating principles of these devices are not employed in the fields of MEMS, NEMS (nano-electromechanical systems), and PICs (photonic integrated circuits), as they rely on the unique opto-mechanical physics. Thus, these novel devices will enable an entirely new family of uses for micro- and nano-mechanical systems that goes far beyond the state of the art. Moreover, they target key societal areas—and markets—of the future, including positioning, navigation and timing, ICT, health and medicine and security.
Background information
FET-Open and FET Proactive are now part of the Enhanced European Innovation Council (EIC) Pilot (specifically the Pathfinder), the new home for deep-tech research and innovation in Horizon 2020, the EU funding programme for research and innovation.