Periodic Reporting for period 1 - Nanophotonics (Nonreciprocal nanophotonics: a new disruptive way to control light with nanotechnology)
Berichtszeitraum: 2021-09-01 bis 2023-08-31
Problem/issue being addressed
Optics in the 21st century is undergoing revolutionary transformations driven by nanotecnology. Over just a few years we have seen a tremendous progress of tiny, nanoscale optical components from fundamental concepts to mass-fabricated consumer products. In my research I have been developing flat optical components 100 times thinner than a human hair.
I was developing a the new frontiers of both fundamental and applied nano-optics research in nonlinear light-matter interactions rendered by nanoscale engineering. Nonlinearity offers a solution to a vital but largely unaddressed problem of contemporary optics and photonics: nonreciprocal optical response at the nanoscale. A nonreciprocal system exhibits different received-transmitted field ratios when their sources and detectors are exchanged. Such response requires breaking the Lorentz reciprocity theorem. Nonlinearity is one of only few fundamentally possible pathways to such behavior.
Importance for society
We live in an information-driven society. Our exponentially growing data exchange has well-surpassed a zettabyte per year, that’s a number with 21 zeros – a remarkable achievement of information and communication technologies (ICT). The ICT revolution started from miniaturisation of nonreciprocal electronics, semiconductor diodes and transistors. The key to the next phase of social changes brought about by the ICT is to replace
electronics with photonics. Future steps are in replacing electrons with photons inside devices, their individual integrated circuits, and ultimately inside microchips. This creates a demand for miniaturisation of photonic components, with nonreciprocal components being among the most challenging to miniaturise. This project takes nonreciprocal photonics all the way to the nanoscale. The project demonstrates the first advanced manufacturing technology for nanophotonic nonreciprocal components.
Overall objectives
Objective 1. To develop a new avenue towards nonreciprocal control of photons at the nanoscale.
Outcome: The objective was achieved in applying the concept of nonlinear metasurfaces with artificial magnetic response to nonreciprocity. In the linear regime, the metasurfaces were optimized to have strong magneto-electric copling, which in nonlinear regime was breaking the reciprocity. A 100 times transmission contrast between the "forward" and "backward" light propagation in a sub-micrometer component was achieved.
Objective 2. To demonstrate design frameworks and fabrication approaches for nanoscale nonreciprocal components.
Outcome: the objective was achieved using COMSOL and CST Microwave Studio software. Nanofabrication was succesfully performed using clean-room facilities at the Paderborn University, including chemical vapour deposition of thin films of materials, electron beam lithography and reactive ion etching. Designed metasurface parameters were met with 10 nm fabrication tolerance.
Objective 3. To evaluate experimentally characteristics of the nanoscale nonreciprocal components.
Outcome: the objective was achieved using two main types of experimental setups depending on the implemented material platform of the metasurfaces. Optical diagnostics of silicon-based and ITO-based metasurfaces was performed using tunable pulsed laser systems (256 fs -- 2 ps pulse duration, 5 MHz repetition rate, 500 mW average power, 1350-1750 nm tunability range). Optical diagnostics of VO2-based metasurfaces was performed with continuus-wave (CW) diode laser 10mW power, 1350-1750 nm tunability range. Asymmetric generation of optical harmonics and nonreciprocal transmission with an order of magnitude forward-backward contrast were measured in experiments.
Optics in the 21st century is undergoing revolutionary transformations driven by nanotecnology. Over just a few years we have seen a tremendous progress of tiny, nanoscale optical components from fundamental concepts to mass-fabricated consumer products. In my research I have been developing flat optical components 100 times thinner than a human hair.
I was developing a the new frontiers of both fundamental and applied nano-optics research in nonlinear light-matter interactions rendered by nanoscale engineering. Nonlinearity offers a solution to a vital but largely unaddressed problem of contemporary optics and photonics: nonreciprocal optical response at the nanoscale. A nonreciprocal system exhibits different received-transmitted field ratios when their sources and detectors are exchanged. Such response requires breaking the Lorentz reciprocity theorem. Nonlinearity is one of only few fundamentally possible pathways to such behavior.
Importance for society
We live in an information-driven society. Our exponentially growing data exchange has well-surpassed a zettabyte per year, that’s a number with 21 zeros – a remarkable achievement of information and communication technologies (ICT). The ICT revolution started from miniaturisation of nonreciprocal electronics, semiconductor diodes and transistors. The key to the next phase of social changes brought about by the ICT is to replace
electronics with photonics. Future steps are in replacing electrons with photons inside devices, their individual integrated circuits, and ultimately inside microchips. This creates a demand for miniaturisation of photonic components, with nonreciprocal components being among the most challenging to miniaturise. This project takes nonreciprocal photonics all the way to the nanoscale. The project demonstrates the first advanced manufacturing technology for nanophotonic nonreciprocal components.
Overall objectives
Objective 1. To develop a new avenue towards nonreciprocal control of photons at the nanoscale.
Outcome: The objective was achieved in applying the concept of nonlinear metasurfaces with artificial magnetic response to nonreciprocity. In the linear regime, the metasurfaces were optimized to have strong magneto-electric copling, which in nonlinear regime was breaking the reciprocity. A 100 times transmission contrast between the "forward" and "backward" light propagation in a sub-micrometer component was achieved.
Objective 2. To demonstrate design frameworks and fabrication approaches for nanoscale nonreciprocal components.
Outcome: the objective was achieved using COMSOL and CST Microwave Studio software. Nanofabrication was succesfully performed using clean-room facilities at the Paderborn University, including chemical vapour deposition of thin films of materials, electron beam lithography and reactive ion etching. Designed metasurface parameters were met with 10 nm fabrication tolerance.
Objective 3. To evaluate experimentally characteristics of the nanoscale nonreciprocal components.
Outcome: the objective was achieved using two main types of experimental setups depending on the implemented material platform of the metasurfaces. Optical diagnostics of silicon-based and ITO-based metasurfaces was performed using tunable pulsed laser systems (256 fs -- 2 ps pulse duration, 5 MHz repetition rate, 500 mW average power, 1350-1750 nm tunability range). Optical diagnostics of VO2-based metasurfaces was performed with continuus-wave (CW) diode laser 10mW power, 1350-1750 nm tunability range. Asymmetric generation of optical harmonics and nonreciprocal transmission with an order of magnitude forward-backward contrast were measured in experiments.
Design framework for nonreciprocal nanoscale components has been developed based on nonlinear light-matter interactions. Nanotechnology fabrication was performed in-house at the University of Paderborn as well as through collaborations with A*Star Singapore and Vanderbilt University, USA. Optical diagnostics has been performed in-house at the University of Paderborn as well as through collaborations with the Australian National University.
Two main results are:
1. World-first demonstration of asymmetric light control in nanoscale components (Fig b). The work was disseminated through a publication in Nature Photonics (2022) -- most prestigious peer-reviewed journal in optics and photonics. A broader society was reached out via a media release of the University of Paderborn and via Nature News and Views article (top 1% science news article by media attention). The results were selected by Optica (formerly The Optical Society) for a "Year in Optics 2022" -- a special collection off articles reporting on most significant breakthroughs of the year.
2. World-first demonstration of nanoscale nonreciprocal optical components (Fig a). The work has been disseminated as a post-deadline presentation at "Frontiers in Optics" -- flagship conference of Optica. Post-deadline selection of conference talks is reserved for most significant recent achievements in optics that deserve rapid dissemination. Peer-review publication is in progress, the materials are available on arXiv repository.
Two main results are:
1. World-first demonstration of asymmetric light control in nanoscale components (Fig b). The work was disseminated through a publication in Nature Photonics (2022) -- most prestigious peer-reviewed journal in optics and photonics. A broader society was reached out via a media release of the University of Paderborn and via Nature News and Views article (top 1% science news article by media attention). The results were selected by Optica (formerly The Optical Society) for a "Year in Optics 2022" -- a special collection off articles reporting on most significant breakthroughs of the year.
2. World-first demonstration of nanoscale nonreciprocal optical components (Fig a). The work has been disseminated as a post-deadline presentation at "Frontiers in Optics" -- flagship conference of Optica. Post-deadline selection of conference talks is reserved for most significant recent achievements in optics that deserve rapid dissemination. Peer-review publication is in progress, the materials are available on arXiv repository.
The project is inspired by the tremendous social changes brought about by our advancements in information and communication technologies and the challenges that these technologies are now facing. We live in an information-driven society. Our exponentially growing data exchange has well-surpassed a zetta-byte per year, that’s a number with 21 zeros. The pathway to cope with the increasing demand for data transfer is to replace electronics with photonics. The first step of this transition was in an important changes in long-range internet communications where copper wires transmitting electrons were replaced with optical fibres transmitting photons. Next envisioned technological steps include replacing electrons with photons inside devices, their individual integrated circuits, and ultimately inside microchips. This creates an ever-increasing demand for miniaturisation of photonic elements. Nonreciprocal components are among the most challenging to miniaturise. This project tackles the fundamentals of this problem testing a hypothesis that our recent advancements in nanoscale topological photonics and nonlinear optics may serve as the enabling knowledge for nanoscale nonreciprocal photonics. The project has developed this hypothesis from basic concepts to proof-of-principle demonstrations. The outcomes of the Fellowship are envisioned to contribute to both basic and applied research. The main limiting factor to the range of possible applications of nonreciprocal nanoscale components outlined in this proposal is the requirement to the excitation light sources. Nonlinear nanoscale optics in its present form is typically associated with pulsed high-power, high-end laser systems, which are costly and bulky. The project however has demonstrated nonlinear nonreciprocal functionalities at incredibly low levels of power of excitation sources thus expanding the area of possible applications. A feasible pathway to miniaturise nonreciprocal components would bring benefits to the development of photonic devices and systems with ultra-compact, ultra-thin form-factors, including light generation and amplification, ultra-fast information processing and communications, as well as integrated optical circuitry.