Periodic Reporting for period 2 - LOGOS (Light-operated logic circuits from photonic soft-matter)
Periodo di rendicontazione: 2022-07-01 al 2023-12-31
The electricity was used for two centuries not only to power the world's industries, but also to spread the information across the Earth. Radio waves of the 19th century were followed by TV broadcasting , which all required more sophisticated electronics, and the electron tubes of the 1930's were replaced by smaller transistors in 1950's. The invention of semiconductor integrated circuits in 1959 by R. Kilby triggered a revolution in miniaturizing electronic circuits, with now millions of transistors on a single piece of silicon. This has enabled a massive increase of computational power, and allowed for streaming and processing of videos, which demand a lot of power. However, we are facing a problem: switching elements, i.e. the transistors, cannot be made arbitrary small, as they approach a size, where quantum effects become important. Furthermore, they cannot be made smaller due to production problems. By making transistors smaller, the electric signals that travel from one transistor to another get delayed and slowed down. This has nowadays slowed the operating rate, at which millions of transistors operate in unison, to a couple of GHz. This rate of switching the electric current through the integrated circuit and dense integration has resulted in huge increase of locally produced heat and temperatures of the chips are increased to the material limits. The ever increasing processing power is therefore blocked by the fundamental limits of electron transport in silicon. If any substantial advancement is to be made, a novel concept of signal and information processing is to be found. Yet, there is a new concept that could replace the electric integrated circuits: photonics or the science and engineering of light. The idea is to replace the flow of electrons in integrated circuits by the flow of photons in photonic integrated chips. Photons, like electrons, behave like particles, and they travel at the speed of light. Unlike electrons, photons do not exert force on each other and it is difficult to control their flow. Nowadays, photons are sent at a speed of light through optical fibres all over the globe, and have replaced the electrons in wire communications. The use of photonics has dramatically increased the amount of information that can be sent to any distant receiver. A typical photonic integrated circuit incorporates micrometer-sized lasers that send light via thin waveguides to light switches, detectors and other photonic elements. Most of today's integrated photonic circuits are made from silicon, exploiting the 50+ years of engineering. Silicon photonics promises to dramatically increase the computing power of microprocessors, which will use light instead of electricity. Yet, it is not quite clear if silicon photonics could support the explosive demand for data processing that is expected in the 21st century. At current pace, the required ICT energy demand will surpass the world total energy production within two decades.
LOGOS is not a mainstream photonics project. Instead, it will be the cornerstone of a new photonic technology based on self-assembled soft matter, likely to evolve into currently unforeseen, futuristic technologies. Unlike today’s photonic technologies based on hard matter that are energy consuming, use poisonous chemicals, precious metals, and producing large amounts of dangerous waste, LOGOS will exploit the room-temperature self-organisation of soft organic matter to develop functional photonic devices. This requires less production energy and reduces the carbon footprint due to the processing of materials at room temperature, uses environmentally friendly organic materials, and drastically reduces hundreds of production steps in silicon technology. This is likely to result in a huge reduction of chemical waste, as soft-matter devices can be both biodegradable and biocompatible.
LOGOS is not a mainstream photonics project. Instead, it will be the cornerstone of a new photonic technology based on self-assembled soft matter, likely to evolve into currently unforeseen, futuristic technologies. Unlike today’s photonic technologies based on hard matter that are energy consuming, use poisonous chemicals, precious metals, and producing large amounts of dangerous waste, LOGOS will exploit the room-temperature self-organisation of soft organic matter to develop functional photonic devices. This requires less production energy and reduces the carbon footprint due to the processing of materials at room temperature, uses environmentally friendly organic materials, and drastically reduces hundreds of production steps in silicon technology. This is likely to result in a huge reduction of chemical waste, as soft-matter devices can be both biodegradable and biocompatible.
LOGOS aims at producing and controlling the flow of light in micro-structured soft matter. We explore materials that produce and amplify light and will be used in devices that control the flow of light by light. We completed a study of optical amplification and robustness against photo-bleaching of different materials. We show that inorganic materials are superior in terms of good optical gain and high stability. A number of liquid crystals have been studied in terms of surface properties and optical quality. We developed new methods to study lasing of liquid crystal micro-lasers. Different geometries of optical micro-cavities were explored. We produced polymer strip waveguides on glass with good optical quality. We produced arrays of micro-fibres that will host liquid crystal droplet. Significant progress has been achieved in understanding spontaneous shape transformation of small liquid crystal droplets into fibres and tori-like structures. This could help to replace printed optical waveguides by spontaneously grown fibre-like structures. We found that surface tension between a liquid crystal with one surfactant and water with another surfactant becomes negative during a rapid cooling of a droplet, which induces transformation of a sphere into a fibre. Spontaneous generation of pairs of oppositely charged topological defects has been observed in a related study, which is important for binding optical micro-elements into functional blocks using the principle of knotting and linking of defects in nematic liquid crystals. Topological properties of nematic liquid crystals have been used in micro-lasers that shine structured light.
Experiments were complemented by modelling and theory. We developed approaches to model the flow of light and the light modes in diverse birefringent geometries, based on finite difference time domain or finite difference frequency domain methods. We demonstrate light profiles, propagation and lasing in complex topological soft matter. We show that such light is highly controllable and strongly couples to the liquid crystal birefringence -both smooth and when spatially distorted with topological defects- leading to diverse photonic phenomena, such as controllable steering of light beams, effective slowing down of light, control over spectrally adaptive phase vortex coronographs, and highly dispersive refractive gratings. The studies of light were supported also by design and assembly studies of different nematic liquid crystal superstructures, including as affected by the presence of electric ions and material flow. Overall, these results are direct contributions to transforming topological soft matter into a capable platform for logical platform manipulation of light, as of central objective of LOGOS.
Experiments were complemented by modelling and theory. We developed approaches to model the flow of light and the light modes in diverse birefringent geometries, based on finite difference time domain or finite difference frequency domain methods. We demonstrate light profiles, propagation and lasing in complex topological soft matter. We show that such light is highly controllable and strongly couples to the liquid crystal birefringence -both smooth and when spatially distorted with topological defects- leading to diverse photonic phenomena, such as controllable steering of light beams, effective slowing down of light, control over spectrally adaptive phase vortex coronographs, and highly dispersive refractive gratings. The studies of light were supported also by design and assembly studies of different nematic liquid crystal superstructures, including as affected by the presence of electric ions and material flow. Overall, these results are direct contributions to transforming topological soft matter into a capable platform for logical platform manipulation of light, as of central objective of LOGOS.
This very high-risk project challenges the mainstream photonic roadmaps by offering a disruptive technology that reduces production times, waste and energy, and enables light processing by light, all currently difficult to obtain in the solid state. LOGOS aims at producing conceptually new photonic technology based on the self-assembly of soft matter and use light to perform logical operations and redirect light signals at gigahertz to terahertz rates. This would lead to environmentally friendly, low-waste and low power, wearable, implantable and biocompatible all-organic photonic technology of the 21st century.