META-ACTIVE - International Research Training Group (IRTG) 2675

Tailored metasurfaces - generating, programming and detecting light

Schematic picture of optical metasurfaces with the functions of generating, programming and detecting light.

Graphic: Isabelle Staude

Doctoral projects including Australian-German Dual-PhD-degree

Metasurfaces composed of designed nanoscale, subwavelength optical elements ("meta-atoms") arranged in a plane have been established as a versatile and efficient platform for controlling the properties of light fields, including their wavefront, polarization, and spectral properties. However, most metasurfaces realized so far were passive and linear; their optical response was permanently encoded into the structure already during fabrication.

Metasurfaces are two-dimensional arrangements of designed nanoscale building blocks that offer exquisite control over the properties of light fields and allow for the realization of ultra-compact, highly functional photonic devices. Within META-ACTIVE, the spatial light control provided by optical metasurfaces will be combined with the capability of their resonant building blocks to enhance light-matter interactions and/or facilitate a tunable optical response. Pertinent research questions encompass various projects in the areas of light-emitting metasurfaces, programmable metasurfaces and metasurface-enhanced detection.

In the framework of the International Research Training Group (IRTG) 2675 "META-ACTIVE", we will create and investigate active metasurfaces, which emit, detect and dynamically manipulate light, making use of the capability of their resonant meta-atoms to enhance the interaction of light with nanoscale matter. By combining the nanoantenna effect of the individual meta-atoms with the additional degrees of freedom offered by the arrangement, metasurfaces provide opportunities for tailoring light-matter interactions far exceeding the respective capabilities of individual nanoantennas. This scientific vision will lay the foundations for new types of high-performance (quantum) light sources, programmable optical systems, and enhanced detectors based on the metasurface concept.

Doctoral projects in Pillar A - Light-emitting metasurfaces: enhancement and tailoring of light-emission processes and their far-field properties by incorporating emitters

A1 - Driving semiconductor metasurfaces to lasing

This project will develop lasing metasurfaces based on III-V and II-VI semiconductor nanostructures in order to realize coherent light emission featuring designed beam shapes. Three fabrication routes will be explored in parallel, all of which are based on well-established concepts from solid-state lasers. The realized active metasurfaces will then be evaluated on their coherent emission characteristics in the far-field. We will gain understanding of how the lasing modes within the metasurfaces evolve in space and time and define the emission properties through spatially variant arrangement of the individual metasurface building blocks.

Primary doctoral supervisors: Prof. Dr. Carsten Ronning (FSU, carsten.ronning@uni-jena.de, www.acp.uni-jena.de/ronning), Prof. Dr. Hoe Tan (ANU), ), Prof. Dr. Isabelle Staude (FSU), Prof. Dr. Lan Fu (ANU), Prof. Dr. C. Jagadish (ANU)
A2 - Nonlinear metasurfaces for photon-pair generation

Entangled quantum states are the most important resource for quantum science and technology. In photonics, such quantum states are often generated using nonlinear optical effects like spontaneous parametric down conversion in materials with second-order nonlinearity. A precise control over the properties of the generated photons is thereby highly desirable. Photonic metasurfaces clearly offer the possibility to control all aspects of linear light propagation and hold great potential for quantum optics as well, where the freedom in tailoring the properties of non-classical states generated by spontaneous frequency conversion in metasurfaces may enable the realization of novel applications of quantum phenomena. This project will investigate this potential with the aim of fully controlling the spatial distribution and spatial entanglement of two-photon quantum states.

Primary doctoral supervisors: Prof. Dr. Isabelle Staude (FSU, isabelle.staude@uni-jena.de, www.acp.uni-jena.de/staude), Prof. Dr. Andrey Sukhorukov (ANU), Prof. Dr. Thomas Pertsch (FSU), Prof. Dr. Dragomir Neshev (ANU), Prof. Dr. Ping Koy Lam, Dr. Frank Setzpfandt (FSU)
A3 - Enhancing magnetic dipole transitions of lanthanides in metasurfaces

The interaction of materials with the magnetic component of light is several orders of magnitude weaker than with the electric component of light. Therefore, when considering light emission, magnetic dipole transitions can usually be safely disregarded. However, in material systems such as trivalent lanthanide ions, where certain electronic transitions are electric-dipole forbidden by selection rules, the magnetic dipole can become dominant. This project aims to enhance and manipulate magnetic dipole transitions by resonant coupling to tailored modes of metasurfaces. We will employ trivalent lanthanides emitting in the near-infrared spectral range as magnetic dipole emitters, which will, for example, be introduced into the metasurface architecture directly by ion implantation.

Primary doctoral supervisors: Prof. Dr. Carsten Ronning (FSU, carsten.ronning@uni-jena.de, www.acp.uni-jena.de/ronning), A/Prof. Dr. Duk-Yong Choi (ANU), Prof. Dr. Isabelle Staude, Prof. Dr. Patrick Kluth (ANU), Dr. Christin David (FSU)
A4 - Efficient light emission from out-of-plane excitons coupled to metasurfaces

Excitons are strongly bound electron-hole pairs, which dominate the optical properties of semiconducting low-dimensional and quantum-confined systems such as two-dimensional transition metal dichalcogenides. In particular, excitons with a long lifetime are extremely beneficial for applications in quantum information, for example. An interesting approach in this direction is to use so-called out-of-plane excitons with lifetimes exceeding nanoseconds. The main goal of this project is to develop a new family of devices for efficient light-matter interaction and the manipulation of such long-lived excitons via their coupling and integration with resonant metallic and dielectric metasurfaces.

Primary doctoral supervisors: Jun.-Prof. Dr. Giancarlo Soavi (FSU, giancarlo.soavi@uni-jena.de, www.acp.uni-jena.de/soavi), Prof. Dr. Dragomir Neshev (ANU), Prof. Dr. Isabelle Staude, A/Prof. Dr. Yuerui Lu (ANU), A/Prof. Dr. Zongyou Yin (ANU)
A5 - Hierarchical nonlinear metasurfaces based on engineered nanocomposites

This project aims to demonstrate efficient second-order nonlinear processes, specifically second harmonic generation and sum-frequency generation, in resonant dielectric metasurfaces composed of tailored non-inversion symmetric effective nonlinear media. Dielectric metasurfaces are most commonly fabricated by nanostructuring thin-films of homogeneous dielectric materials, typically semiconductors or other high-index dielectric materials. Thus, the local optical properties of the meta-atoms' constituent materials are limited to those provided by natural materials. This project will overcome this limitation and construct dielectric metasurfaces from engineered nanocomposites.

Primary doctoral supervisors: Prof. Dr. Andreas Tünnermann (FSU, andreas.tuennermann@uni-jena.de, www.acp.uni-jena.de/tuennermann), A/Prof. Dr. Lan Fu (ANU), Prof. Dr. Thomas Pertsch (FSU), Prof. Dr. Hoe Tan (ANU), A/Prof. Dr. Duk-Yong Choi (ANU)

Doctoral projects in Pillar B - Programmable metasurfaces: dynamic tuning of optical properties by the application of external stimuli, ultimately allowing on-demand programming of functionalities

B1 - Programmable dielectric metasurfaces based on hybridization with liquid crystals

The integration of optical metasurfaces in liquid crystal (LC) cells has proven to be a successful strategy to realize pronounced metasurface resonance tuning. Such integration promises to enable spatial light modulation with unitary efficiency and fast speed, derived from a subwavelength size of both the individual pixels and thickness of the device for the first time. This project targets the realization of fully programmable metasurfaces based on LC integration, which exhibits complex dynamic functionalities dependent on one or more external stimuli. Dynamic control of the metasurface response with high spatial resolution will be realized as a central step towards metasurfaces with freely programmable optical functionality.

Primary doctoral supervisors: Dr. Isabelle Staude (FSU, isabelle.staude@uni-jena.de, www.acp.uni-jena.de/staude), Prof. Dr. Dragomir Neshev (ANU), Dr. Falk Eilenberger (FSU), Prof. Dr. Andreas Tünnermann (FSU/Fraunhofer IOF), A/Prof. Dr. Duk-Yong Choi (ANU), Prof. Dr. Ilya Shadrivov (ANU)
B2 - Active 2D materials and heterostructures for switchable resonant metasurfaces

Monolayer transition metal dichalcogenides (TMD) have been intensively studied in recent years owing to their unique electronic and optical properties. The 2D nature of both TMDs and metasurfaces facilitates their integration and makes their hybrids particularly suited for a large range of applications. However, the integration of TMDs with optical metasurfaces has been hampered so far by the lack of integrated growth technologies, requiring scientists to resort to the manual transfer of 2D materials to nanostructured substrates. In this project, we will focus on the integration of TMDs and their heterostructures with resonant metasurfaces with the aim of switching the latter's interaction with light using coupling of selective excitonic features to resonant modes of the meta-atoms.

Primary doctoral supervisors: Falk Eilenberger (FSU, falk.eilenberger@uni-jena.de, www.acp.uni-jena.de/eilenberger), A/Prof. Dr. Yuerui Lu (ANU), Prof. Dr. Ping Koy Lam, Prof. Dr. Andreas Tünnermann (FSU/Fraunhofer IOF), Prof. Dr. Isabelle Staude (FSU), Jun.-Prof. Dr. Giancarlo Soavi (FSU)
B3 - Spatio-temporal dynamics in nonlinear metasurfaces

When appearing separately, frequency dispersion, spatial dispersion, and nonlinearity are well-understood effects in optical physics. However, if these effects appear simultaneously, they give rise to non-trivial phenomena. The complexity of these phenomena is further increased by spatial inhomogeneity of the system, which, together with the nonlinearity-induced temporal inhomogeneity eventually gives rise to a loss of translation symmetries both in space and time. Effectively eliminating conservation laws in a controllable fashion, such systems could display any type of system behavior. This project will study the arising of new complex phenomena in nonlinear metasurfaces, which holds promise in realizing multifunctional nano-sized optical systems.

Primary doctoral supervisors: Prof. Dr. Thomas Pertsch (FSU, thomas.pertsch@uni-jena.de, www.acp.uni-jena.de/pertsch), Prof. Dr. C. Jagadish (ANU), Prof. Dr. Isabelle Staude (FSU), Prof. Dr. Ilya Shadrivov (ANU)
B4 - Exciton-polariton-dynamics on an active metasurface

In this project, we will realize and study active metasurfaces based on strong coupling between excitons in a semiconducting material and photons confined by a resonator or waveguiding structures. A high-energy electron-hole plasma is formed if either a quantum well or one or a few atomically thin layers of a transition metal dichalcogenide crystal is excited with photon energies well above the band gap. Pairs of electrons and holes form excitons and relax towards the band edge due to Coulomb scattering and interaction with phonons. Given an electromagnetic resonance close to the 1s-exciton energy, strong exciton-photon coupling occurs, resulting in the formation of new collective states (so-called exciton-polaritons). Our project aims to explore the capabilities of effective potential and loss/gain landscapes for exciton-polaritons which will be created by either a structured illumination with an incoherent driving field and/or by subwavelength patterning.

Primary doctoral supervisors: Prof. Dr. Ulf Peschel (FSU, ulf.peschel@uni-jena.de, www.acp.uni-jena.de/peschel), Prof. Dr. Elena Ostrovskaya (ANU), Prof. Dr. Isabelle Staude (FSU)

Doctoral projects in Pillar C - Metasurface-enhanced detection: enhance and tailor various detection and light harvesting processes

C1 - Chiroptical sensing with tunable and broadband chiral metasurfaces

Chirality determines the chemical and physical properties of chiral matter and plays an important role in many fields, including life sciences, medicine, optics, and materials sciences. Being able to precisely analyze and quantify chiral matter is of critical importance. Chiral analyses based on optical detection are attractive because they are clean, fast, and non-destructive. This project aims to develop metasurfaces to convert far-field illumination into a well-designed near field so that the chiroptical response of chiral matter can be enhanced and the sensitivity of optical chiral sensing can be improved.

Primary doctoral supervisors: Dr. Jer-Shing Huang (FSU, jer-shing.huang@leibniz-ipht.de, www.acp.uni-jena.de/huang), Prof. Dr. Ilya Shadrivov (ANU), Prof. Dr. Isabelle Staude (FSU), Prof. Dr. Ulf Peschel (FSU)
C2 - Metasurface enhanced single photon detection

Single photon detection will have tremendous impacts in a broad spectrum of applications, including astro- and astroparticle physics, photon science and spectroscopy, quantum cryptography and quantum optics. Due to their excellent characteristics, superconducting nanowire single-photon detectors and single photon avalanche photodetectors have attracted much attention in recent years despite the need to cool them to cryogenic temperatures. In this project, we aim to enhance the single photon detection efficiency of superconducting nanowire single-photon detectors and single photon avalanche photodetectors by frequency-selective metasurfaces. Furthermore, we will realize polarization-dependent single photon detection using anisotropic metasurface designs.

Primary doctoral supervisors: Prof. Dr. Heidemarie Schmidt (FSU, heidemarie.schmidt@leibniz-ipht.de, www.acp.uni-jena.de/hschmidt), A/Prof. Dr. Lan Fu (ANU), Dr. Christin David (FSU), Prof. Dr. Ilya Shadrivov (ANU)
C3 - Metasurface-based quantum-state detection and discrimination

Quantum imaging protocols like quantum ghost imaging promise an enhanced sensitivity and access to enlarged spectral ranges compared to classical schemes. However, they usually measure only the intensity of light and hence cannot detect fully transmissive objects. On the other hand, for many interesting applications, e.g. in biology and the life sciences, the objects under investigations are mostly transmissive, but have a distinct influence on the polarization of light, which cannot be easily characterized with established measurement modalities. This project aspires to use metasurfaces in a quantum ghost imaging scheme, combining the advantageous features of quantum measurement protocols with the capabilities of metasurfaces for advanced polarization state control.

Primary doctoral supervisors: Prof. Dr. Thomas Pertsch (FSU, thomas.pertsch@uni-jena.de, www.acp.uni-jena.de/pertsch), Prof. Dr. Andrey Sukhorukov (ANU), Prof. Dr. Isabelle Staude (FSU), Dr. Frank Setzpfandt (FSU)
C4 - Semiconductor metasurfaces for energy applications: active tuning of photon absorption and hot electron detection

Photocatalysis plays a vital part in environment and energy applications such as wastewater treatment, water splitting, carbon dioxide reduction, disinfection, and solar desalination. However, the semiconductors typically employed suffer from low quantum efficiencies and are photoactive in the ultraviolet, insensitive to a major part of the visible solar spectrum, and inapplicable to biological and chemical applications where absorption lies in the far-infrared. Metasurfaces allow for the enhancing of quantum efficiencies and for geometrical tailoring of resonances, thus allowing for nanophotonic enhancement of photocatalytic processes. This project will develop a theoretical description of photocatalysis at metasurfaces with focus on the enhancement phenomena mediated by specific metallic and dielectric nanostructures realized at ANU.

Primary doctoral supervisors: Dr. Christin David (FSU, christin.david@uni-jena.de, www.acp.uni-jena.de/davidExternal link), Dr. Fiona Beck (ANU), Prof. Dr. Ulf Peschel (FSU), Prof. Dr. Kylie Catchpole (ANU)

German partners

Australian partners