Professor Willie Padilla

Autonomous Agentic Frameworks for the End-to-End Inverse Design of Electromagnetic Metamaterials

Artificial electromagnetic materials (AEMs) provide unprecedented control over the scattering of electromagnetic waves, enabling exotic responses unrealizable with naturally occurring materials. The design of complex functional metasurfaces is typically cast as a challenging inverse problem. Because the design space is frequently massive and the fundamental physics are often ill-posed, conventional optimization approaches struggle to find optimal geometrical configurations within a reasonable computational timeframe. While deep inverse models (DIMs) have demonstrated significant success in overcoming these limitations, the recent evolution from large language models (LLMs) to autonomous agentic systems has created a new frontier for automated scientific discovery.

We present an autonomous agentic framework that automates the complete end-to-end workflow of metamaterial research and inverse design. When prompted with a target optical scattering response, the agent autonomously reasons, plans, and utilizes external tools via APIs to first develop a custom forward deep learning surrogate model, and subsequently execute a deep inverse method to yield the optimized AEM geometry. We demonstrate the framework’s effectiveness within highly dimensional all-dielectric metasurface (ADM) design spaces, illustrating the agent’s capacity to adapt its strategy in real-time, store short- and long-term memory, and utilize internal reflection to achieve performance on par with published human studies. In view of the great potential for the future of this exciting research area, we review recent advances, open challenges, and future directions for agent-driven electromagnetic research.

Dr Tuomas Haggren

All-optical Active Terahertz Metasurfaces for Ultrafast Polarisation Control

Luyao Wang a, Kun Peng b, Tuomas Haggren a, Ford M. Wagner b, Sarah Norman b, Daria A. Smirnova a, Hark Hoe Tan a, Chennupati Jagadish a, Ilya V. Shadrivov a, Michael B. Johnston b
a ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Research School of Physics, The Australian National University, Mills Road, Canberra, 2601, ACT, Australia.
b Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK

Terahertz (THz) technologies increasingly require active photonic components that can manipulate electromagnetic waves on ultrafast timescales. However, dynamic THz metasurfaces remain limited by modulation speed, efficiency, and architectures based on passive metallic structures. Here we demonstrate an all-optical semiconductor metasurface for ultrafast THz polarisation control. The metasurface consists of stand-alone, S-shaped GaAs meta-atoms transferred onto a quartz substrate, enabling low-loss operation while allowing the electromagnetic response to be governed by the semiconductor resonator volume. Femtosecond optical excitation injects free carriers into the 2-µm-thick GaAs structures, transiently driving them from a dielectric-like to a metallic-like electromagnetic regime. This activates a broadband chiral response that converts linearly polarised THz radiation into the orthogonal polarisation, with cross-polarised transmission amplitudes up to 0.4 across 0.5–3 THz. Full-wave simulations based on a carrier-dependent Drude model reproduce the measured response and show how increasing free-carrier density turns on the resonant behaviour. Direct comparison with geometrically identical gold metasurfaces confirms that photoexcited GaAs approaches the response of metallic resonators. These results provide a scalable route to ultrafast, optically reconfigurable THz meta-optics.

Oleg Kameshkov

Development of Terahertz Meta-Optical Components for Polarisation Control: Polarisers and Waveplates

Oleg Kameshkov a, Vladlen Shvedov a, Yana Izdebskaya a, Rajour Tanyi Ako b, Peter Francis Mathew Elango b, Madhu Bhaskaran b, Ilya V. Shadrivov a
a ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia.
b ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS) and Functional Materials and Microsystems Research Group, RMIT University, Melbourne, Australia.

Over the past year, we have advanced the research and development of the devices presented within terahertz meta-optics startup from TMOS Shark Tank 2025 pitch. Our work focused on two key component families: terahertz polarisers and waveplates, which are essential building blocks for spectroscopy, imaging, sensing, and polarisation-sensitive terahertz systems.

In this presentation, we will demonstrate freestanding wire-grid polarisers, which are approaching market readiness. These devices are fabricated using laser micromachining and are designed to provide high transmission, high extinction ratio, and substrate-free operation. We will also present our progress in developing broadband terahertz waveplates based on structured silicon, with emphasis on polarisation conversion efficiency, fabrication feasibility, and suitability for integration into terahertz time-domain spectroscopy systems.

Beyond technical results, we will outline the business traction achieved since Shark Tank, including a more detailed market analysis, clearer customer segments, and progress in protecting our intellectual property. Finally, we will present the next steps to attract new investment, expand the product line, and build a specialized terahertz component company focused on customizable polarisation optics.

Tongmiao Fan

Tailored quantum states from nonlinear metasurfaces

Tongmiao Fan a, Jinyong Ma a,b , Frank Setzpfandt c, and Andrey A. Sukhorukov a
a ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australia
b Institute of Quantum Precision Measurement, State Key Laboratory of Radio Frequency Heterogeneous Integration, College of Physics and Optoelectronic Engineering, Shenzhen University, P. R. China
c Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Germany

Quantum states are key resources for high-dimensional quantum communications, information processing, imaging, and fundamental studies of nonclassical light. Conventional biphoton quantum sources typically rely on bulk nonlinear crystals and external optical assemblies to engineer spontaneous parametric downconversion (SPDC). Although powerful, these platforms are often large, alignment-sensitive, and difficult to deploy beyond laboratory environments, creating a need for miniaturized, stable, and designable quantumlight sources.

Here, we present collaborative progress in generating tailored quantum states from ultrathin nonlinear metasurfaces. Optical resonances in these metasurfaces provide a compact mechanism for enhancing SPDC and controlling the symmetry, polarization, spatial-mode structure, spectrum, and directionality of emitted photon pairs. Using a nonlocal metasurface consisting of a silica grating integrated with a lithium niobate film, we demonstrate tunable generation of spectral entanglement through resonant dispersion engineering [1], as in Fig. 1(a). We also show enhanced biphoton generation from a van der Waals nonlinear metasurface based on 3R-MoS2 in Fig. 1(b) [2]. Finally, building on hyperentanglement generation from [110]-oriented InGaP metasurfaces, we develop programmable quantum-state generation driven by complex pump fields. Together, these studies highlight how collaborative development of nonlinear metasurfaces can enable compact, stable, and engineered quantum-light sources.

[1] Tongmiao Fan et al. “Tailored biphoton entanglement from a nonlinear metasurface”, under preparation
[2] Tongmiao Fan et al. “Enhanced Photon-Pair Generation from a van der Waals Metasurface”, Nano Letters 2025 25 (31), 11844-11851
[3] Tongmiao Fan et al. “Hyperentangled photon-pair generation from a nonlinear metasurface”, under preparation

Dr Wei Wen Wong & Yiyang Cui

Coupling black phosphorus emission with bottom-up III-V microring cavities for mid-infrared lasing

Yiyang Cui a, Huan Liu a,b, Sudhanshu Kumawat a, Wei Wen Wong c, Hark Hoe Tan c, and Kenneth Crozier a
a Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, School of Physics, University of Melbourne, Parkville, VIC 3010, Australia.
b University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China
c Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2600, Australia.

Black phosphorus (BP), a two-dimensional allotrope of phosphorus, has emerged as a promising material for next-generation optoelectronic applications. Its direct bandgap is readily tunable via its layer number or external electric fields – spanning from ~ 1.7 eV in monolayers to 0.31 eV in bulk – making it an ideal material for photodetection and emission in the technologically critical mid-infrared (MIR) region [1,2]. While recent demonstrations of bright, room-temperature photoluminescence [3] and scalable exfoliation techniques [4] highlight the potential for BP-based MIR lasers, achieving coherent lasing action in compact devices remains a challenge. To date, reports have been largely limited to optically pumped lasing in BP flakes embedded within distributed Bragg reflector cavities [5,6], which have limited potential for high-density integration.

Here, we demonstrate the optical coupling of spontaneous emission from BP to whispering-gallery modes supported in epitaxially grown InP microring cavities, establishing a pathway toward compact MIR BP micro-cavity lasers. Our bottom-up microrings were grown directly on their native substrate via selective area epitaxy, effectively eliminating the etching-induced sidewall damage that typically introduces scattering and non-radiative recombination losses. Through numerical modelling, we optimised the ring cavity design to maximise both the quality factor and the spectral overlap between the spontaneous emission and the cavity mode. Following the mechanical exfoliation and transfer of BP flakes onto the microrings, we characterised the coupled systems via room-temperature photoluminescence measurements. Key findings elucidating the optical coupling between the BP flakes and the resonant cavities will be presented.

[1] Li et al., 2017. Nature Nanotechnology, 12(1), pp.21-25.
[2] Chen et al., 2020. Science Advances, 6(7), p.eaay6134.
[3] Chen et al., 2019. Nano Letters, 19(3), pp.1488-1493.
[4] Liu et al., 2025. Advanced Optical Materials, 13(27), p.e00460.
[5] Huang et al., 2019. ACS Photonics, 6(7), pp.1581-1586.
[6] Zhang et al., 2020. Advanced Materials, 32(17), p.1808319.

Professor Heike Ebendorff-Heidepriem

Specialty optical glasses and fibres: a powerful platform for the exploration of new concepts and applications

Heike Ebendorff-Heidepriem a
a School of Physics, Chemistry and Earth Sciences; and Institute for Photonics, Advanced Sensing and Quantum Technologies (IPAS-QT), Adelaide University, Adelaide, South Australia 5005, Australia.

Optical glasses and fibres provide a broad range of tailorable photonic and quantum properties, such as transmission window, fluorescence, plasmonics and nonlinear light conversion, through design of chemical composition, nano-/micro-structuring, adding dopants such as luminescent lanthanide ions and nano-/micro-crystals, and surface functionalization. This wide tunability of properties make specialty optical glasses and fibres a powerful platform to explore new science and engineering concepts as well as new applications as illustrated by these examples:

• • tellurite glasses doped with luminescent lanthanide ions for new avenues in temperature sensing and volumetric display [1,2,3]
  • exposed-core silica glass microstructured fibres as a waveguiding substrate for utilizing light manipulation properties of thin films and 2D materials [4,5,6]
  • extrusion-based glass shaping techniques for fabricating soft glass optical fibres with new structures for exploring new photonics concepts [7,8]
  • soft glass fibres doped with luminescent diamond particles for quantum-based magnetic field sensing [9,10]
  • tellurite glass with in-situ grown gold nanoparticles for extraordinary plasmonic tuning [11]
  • ZBLAN fluoride glass fibres drawn in microgravity for ultra-low-loss fibre optics cables [12]

Farid Khoshkhati & Dr Yana Izdebskaya

Active Colour Tuning of Dielectric Mie voids using Liquid Crystals

Yana Izdebskaya a, Farid Khoshkhati b, Lily Li c, Ann Roberts b, and Ilya Shadrivov a
a ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
b ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), School of Physics, The University of Melbourne, Parkville, VIC 3010, Australia
c Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2600, Australia

In contrast to conventional Mie resonators, which typically consist of high-refractive-index nanopillars embedded in a low-refractive-index medium, Mie voids are formed by introducing subwavelength air holes within a high- efractive-index material. This inverted geometry has recently emerged as an alternative platform for Mie-resonant metasurfaces, offering several advantages, including stronger electromagnetic field confinement, improved accessibility to the fields within the voids, reduced dispersion, and lower optical losses [1]. These characteristics may lead to promising applications in areas such as nanoprinting and nanoplastics detection [2].

Such metasurfaces are typically limited by their fixed optical properties defined at a fabrication step. However, a key direction in metasurface development is the realization of tunable and switchable functionalities for practical photonic devices. Recently, it was demonstrated that elliptical Mie voids can enable switching functionality by changing the polarisation state of the incident light [3]. Nevertheless, active control of Mie-void metasurfaces has not been demonstrated so far. In this work, we have integrated silicon Mie voids with liquid crystals (LCs) to investigate the feasibility of actively tuning their optical response using external stimuli. It has been demonstrated that both rotation of the polarization direction of the incident light and elevation of the temperature above the nematic-to-isotropic transition temperature of the LC material induce significant shifts in the reflected colour from the voids. This strategy provides several key advantages, including spectral tunability across a wide wavelength range.

[1] M. Hentschel, K. Koshelev, F. Sterl, S. Both, J. Karst, L. Shamsafar, T. Weiss, Y. Kivshar, and H. Giessen, Light Sci. Appl. 12, 3 (2023).
[2] D. Ludescher, L. Wesemann, J. Schwab, J. Karst, S. B. Sulejman, M. Ubl, B. O. Clarke, A. Roberts, H. Giessen, and M. Hentschel, Nat. Photon. 19, 1138–1145 (2025).
[3] S. Arslan, S. B. Sulejman, S. Klein, J. Haehner, J. Schwab, D. Ludescher, L. Wesemann, A. Roberts, H. Giessen, and M. Hentschel, Small 22, e11992 (2026).

Dr Phuong Yen Le

Non-volatile tuning of Fano resonances in a phase-change single-layer two dimensional photonic crystal slab metasurface

Benjamin J. Russell a,b, Krishna Murali c,d, Peter Francis Matthew Elango c,d, Phuong Y. Le c,d, Huan Liu a,b,e, Madhu Bhaskaran c,d, and Kenneth B. Crozier a,b,f
a School of Physics, The University of Melbourne, Parkville 3010, Australia
b ARC Centre of Excellence for Transformative Meta-optical Systems (TMOS), The University of Melbourne, Parkville 3010, Australia
c Functional Materials and Microsystems Group, RMIT University, Melbourne 3000, Australia
d ARC Centre of Excellence for Transformative Meta-optical Systems (TMOS), RMIT University, Melbourne 3000, Australia
e University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China
f Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville 3010, Australia

Low-loss Fano resonances in photonic crystal slabs are central to nanophotonic devices such as nanolasers, refractometric biosensors, and twisted bilayer metasurfaces. However, their utility is limited by the fact that their resonant behavior is generally fixed after fabrication. The Pockels, Kerr and thermo-optics effects have been used to tune Fano resonances, but in a volatile fashion. Recent works have demonstrated the non-volatile tuning of leaky guided-mode resonances using phase change materials incorporated into structures with multiple layers. Here, we experimentally demonstrate the non-volatile tuning of low-loss Fano resonances in a photonic crystal slab metasurface comprising a single nanopatterned layer, exhibiting remarkable modulation depth and high fidelity with simulation. Our design uses an ultra-thin film of antimony triselenide (Sb2Se3) patterned with a square unit cell on fused silica, optimized to maximize transmission contrast between amorphous and crystalline phases. Infrared spectra show redshifts of the Fano dip from 1441 nm to 1553 nm (112 nm) and transmission contrast up to 15.4 dB.

Dr Gurpreet Singh Gill

Resolution-Enhanced Spectral Reconstruction Using MEMS Fabry–Pérot Filters

Gurpreet Singh Gill a, Jiajun Meng b, Gilberto Umana-Membreno a, Mariusz Martyniuk a, Dilusha Siliva a, Kenneth Crozier b and Lorenzo Faraone a
a The University of Western Australia, Department of Electrical, Electronic and Computer Engineering, Perth, Western Australia, Australia
b School of Physics, The University of Melbourne, Melbourne, Victoria, Australia

Spectral reconstruction is a computational technique used to recover spectral information from a limited number of spectrally selective optical measurements. It is particularly useful for compact spectroscopic systems, where the measured response may be limited by filter bandwidth, tuning step size, signal-to-noise ratio, or available instrumentation. By combining calibrated filter responses with suitable reconstruction algorithms, target spectra can be estimated with improved effective spectral resolution without relying on bulky or highly specialised spectroscopic equipment. In this work, we use microelectromechanical systems (MEMS)-based Fabry–Pérot filters (FPFs) [1–3] to validate resolution-enhanced spectral reconstruction over the 1.3–1.6 μm wavelength range. The MEMS-FPFs were designed and fabricated at the University of Western Australia in a standard microelectronics cleanroom environment. Their spectral responses were characterised using a monochromator setup at UWA and used as the calibration basis for reconstruction performed at the University of Melbourne.

The preliminary results demonstrated the feasibility of this approach. As shown in Fig. 1, the reconstructed narrowband spectrum agrees well with the monochromator reference, while showing a much sharper response than the direct MEMS-filter measurement. This indicates that computational reconstruction can recover spectral features broadened by the filter response and improve the effective resolving capability of the MEMS FPF measurement system. We anticipate extending the study using the latest MEMS-FPF device batch with improved optical performance and implementing a more robust automated measurement system capable of repetitive measurements with finer voltage sampling steps to obtain a larger and more accurate calibration dataset. We also plan to demonstrate the method by reconstructing the transmission spectra of fixed bandpass filters and broadband polymer samples, providing a more systematic evaluation of the reconstruction accuracy, robustness, and practical limitations of the proposed MEMS-FPF-based spectroscopic platform.

[1] M. Martyniuk et al., “Optical microelectromechanical systems technologies for spectrally adaptive sensing and imaging,” Advanced Functional Materials, 32(3), 2103153, 2022.
[2] G. S. Gill, Investigation of MEMS-based spectrally adaptive Fabry–Pérot interferometers for long-wave infrared applications, Doctoral thesis, The University of Western Australia, 2022.
[3] J. R. Silva et al., “Large area silicon-air-silicon DBRs for infrared filter applications,” Journal of Lightwave Technology, 37(3), 769–779, 2019.

Professor Sejeong Kim

Structured light and chiral photonics

Dr. Sejeong Kim is an Associate Professor at the School of Electronic and Electrical Engineering at Sungkyunkwan University. She received her PhD in Physics from KAIST (Korea Advanced Institute of Science and Technology) and was a research fellow at the University of Technology Sydney before joining Melbourne.

She led the Melbourne Integrated Nanophotonics Engineering (MINE) lab, where her research focuses on light-matter interactions at the nanoscale, particularly involving photonic and plasmonic cavities, quantum light sources, and 2D materials. Dr. Kim is an OPTICA Ambassador and the Chair of OPTICA’s Nanophotonics Technical Group. Her contributions to integrated nanophotonics have been recognized with several awards, including the 2022 Ivan P. Kaminow Outstanding Early Career Professional Prize, the Young Tall Poppy Science Award.

Dr Jiajun Meng

Snapshot MWIR Polarimetric Imaging Enabled by a Metalens

W. Pan a, J. Meng b, H. Tan c, D. Neshev c, K. Crozier b, M. Martyniuk a, L. Faraone a
a Department of Electrical, Electronic and Computer Engineering, The University of Western Australia, Perth, Western Australia, Australia
b School of Physics, The University of Melbourne, Melbourne, Victoria, Australia
c Research School of Physics, Australian National University, Acton, ACT 2601, Australia

Polarimetric thermal imaging provides information beyond conventional infrared intensity imaging, including surface orientation, material properties and polarisation signatures. Existing mid-wave infrared (MWIR) polarimetric imaging systems typically rely on rotating polarisers, beam splitters or detector-integrated micropolariser arrays, increasing system complexity and limiting compact implementation.

Here we present the design, optimisation and experimental demonstration of a snapshot MWIR polarimetric imaging system enabled by a polarisation-sensitive metalens. The metalens simultaneously forms multiple polarisation-resolved thermal images on a commercial bolometer-based infrared focal plane array (FPA), enabling linear polarisation information to be recovered from a single exposure without moving parts or additional polarisation optics. The optical design was optimised to improve imaging performance and polarisation discrimination while maintaining compatibility with a conventional thermal infrared camera.

The four simultaneously acquired linear-polarisation images, corresponding to analyser orientations of 0°, 45°, 90° and 135°, are processed to reconstruct the linear Stokes parameters (S0, S1 and S2). These parameters yield the total intensity, degree of linear polarisation (DoLP) and angle of linear polarisation (AoLP) of the observed scene. Experimental results demonstrate thermal polarimetric imaging of representative targets, revealing polarisation-dependent image contrast associated with surface geometry and material properties that is not apparent in conventional thermal images. Real-time measurements further demonstrate stable snapshot operation and continuous tracking of dynamic linear-polarisation changes.

The proposed metalens provides a compact optical solution for infrared polarimetric imaging while remaining compatible with commercially available thermal cameras. This work highlights the potential of metasurface optics combined with computational polarimetric image reconstruction to realise compact and scalable MWIR polarimetric imaging systems for applications including autonomous sensing, machine vision, remote inspection and environmental monitoring

Dr Chaohao Chen & Yang Yu

Harnessing Non-Boltzmann Steady States in Lanthanide Nanocrystals for Mid-Infrared Optoelectronics

Yang Yu a, Wei Wen Wong a, Dawei Liu a, Zhe Li a, Jinyuan Chen b, Seyed Saleh Mousavi Khaleghi b, Hongwei Liu d, Xiaoying Huang a, H. H. Tan a, C. Jagadish a, Chaohao Chen c, Kenneth Crozier b, Ziyuan Li e, and Lan Fu a
a Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2600, Australia
b Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, University of Melbourne, Victoria, Australia
c Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, The University of Technology Sydney, Ultimo, NSW 2007, Australia

Converting mid-infrared (MIR) radiation to visible or near-infrared wavelengths is essential for imaging and sensing, yet achieving sensitive, low-power, and scalable detection remains challenging. Lanthanide nanocrystals provide an alternative through ratiometric luminescence but are typically constrained by Boltzmann statistics, which tie population distributions to lattice temperature and limit signal contrast. Here we show that MIR irradiation rebalances dissipative relaxation pathways, driving lanthanide emitters into a non-Boltzmann steady state that enables non-thermal control of population distributions. This allows emission behaviours inaccessible under thermal equilibrium. We exploit this regime to achieve linear MIR detection with respect to MIR power across 6.8–8.6 µm. The ratiometric response is intrinsically independent of the pump power, enabling operation at an ultralow excitation power of 10 µW, several orders of magnitude lower than conventional approaches. Using standard silicon photodetectors, we then demonstrate room-temperature MIR imaging with detection limits approaching 4 nW µm-2. Our results establish lanthanide nanoparticles as an efficient platform for MIR conversion and sensing in nanophotonic systems.

Professor Kristinn Gylfason

A guide to the design and packaging of silicon photonic MEMS

Kristinn B. Gylfason received the title of Docent in Micro- and Nanosystems in 2015 and the PhD degree in Electrical Engineering in 2010, both from KTH. He received the MSc and BSc degrees in Electrical Engineering from the University of Iceland in 2003 and 2001, respectively. In the spring term of 2002, he did an exchange at the University of California, Santa Barbara, USA. From 2003 through 2005, he was a research engineer at Lyfjathroun Biopharmaceuticals, Iceland, and in 2005 he received the Steinmaur Foundation nanotechnology graduate study scholarship. He received the Göran Gustafsson Young Researcher Price as well as the largest Young Researcher grant awarded by the Swedish Research Council to KTH in 2011. During spring 2013, Kristinn was a visiting post-doctoral scholar at the Photonics Group, Ghent University, Belgium.

Kristinn Gylfason is researching nanophotonics and how they can enhance our environmental monitoring and communication systems. The localization of hidden sources of greenhouse gas emissions, such as carbon dioxide and methane, is becoming increasingly important due to global warming. Through the tools of nanophotonics, small and inexpensive gas sensors can be manufactured in large volumes to establish global networks of environmental monitoring sensors. Kristinn and his research team have developed miniaturized optical carbon dioxide and methane sensors that can be integrated into smartphones or flown around in drones to ensure air quality and locate emissions. As the need for data communication continues to grow, more of our communication systems are becoming optical. By employing nanophotonic methods, energy-intensive microelectronic circuits can be replaced with light circuits capable of handling large amounts of data with minimal energy consumption. Kristinn and his research group have developed such light circuits that can dramatically reduce power consumption in data centers.

Dr Wenwu Pan

Metalens-Integrated MWIR HgCdTe Detectors for High Operating Temperature: Front- and Back-Illuminated Architectures

W. Pan, M. Martyniuk, L. Faraone (Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems, Department of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia)
T. Haggren, H. Tan, D. Neshev (ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia)

High-operating-temperature (HOT) infrared detectors are important for reducing the cooling requirements, size and complexity of next-generation sensing platforms. Here, we present the design, integration and system level modelling of metalens-integrated mid-wave infrared (MWIR) HgCdTe detectors, considering both front- and back-illuminated architectures. The approach decouples the optical collection area from the detector active area. A metalens concentrates radiation collected over a comparatively large aperture onto a reduced detector volume, increasing the photon-flux density while limiting thermally generated noise. This architecture is designed to improve the signal-to-noise ratio (SNR) at elevated operating temperatures. The MWIR metalens diameter, focal length and meta-atom pitch are jointly optimised to achieve high optical efficiency and minimise the required detector size while maintaining compatibility with practical detector integration.

In both front- and back-illuminated architectures, the metalens concentrates incident radiation onto a reduced active region. The front-illuminated implementation uses a metalens array on a thin sapphire substrate bonded to an n-type HgCdTe photoconductor (PC) array, providing a comparatively simple integration route. The back-illuminated implementation forms the metalens array on the rear surface of the CdZnTe substrate of an HgCdTe photovoltaic (PV) detector, enabling optical concentration into a reduced junction area in a PV architecture. The modelling framework incorporates photon collection, background radiation and temperature dependent detector noise. The results indicate that metalens-enabled optical concentration can improve SNR at elevated operating temperatures, while comparison of the PC and PV architectures highlights trade-offs among signal response, noise performance and integration complexity. These results establish a pathway towards compact, high-performance MWIR detectors with reduced cooling requirements through the co design of meta-optics and HgCdTe detector architectures.

Wenyi Li

Reflective Diffractive Optical Neural Network with Metasurfaces

Wenyi Li a,b,f, René Geromel c, Duk-Yong Choi d, Thomas Pertsch a,b,e, Thomas Zentgraf c, Dragomir Neshev f, Sina Saravi a,g
a Institute of Applied Physics and Abbe Center of Photonics, Friedrich Schiller University Jena, Jena, Germany
b Max Planck School of Photonics, Jena, Germany
c Institute for Photonic Quantum Systems (PhoQS) and Department of Physics, Paderborn University, Germany
d Laser Physics Centre, Research School of Physics, Australian National University, Canberra, Australia
e Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany
f ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australia
g Heinz Nixdorf Institute, Department of Electrical Engineering and Information Technology, Institute for Photonic Quantum Systems (PhoQS), Paderborn University, Paderborn, Germany

As artificial intelligence models continue to advance, there is an increase in the demand for faster and more energy-efficient computing methods. Optical computing, which utilises light and optical components, offers significant advantages in terms of speed and efficiency [1]. Currently, metasurfaces have made substantial advancements, largely attributable to fabrication improvements, thus enabling realisation of novel structures and applications [2]. The convergence of these two dynamic fields offers a promising opportunity to develop more efficient and compact diffractive optical neural networks (DONNs). Despite the exploration of various DONN architectures in different wavelengths and configurations [3], challenges remain in terms of miniaturization, fabrication for visible/near-infrared operation and precise multilayer alignment.

The objective of our project is to develop cascaded metasurfaces to achieve advanced neural network performance. This approach has the potential to yield compact, efficient optical computing systems. To address these challenges, we propose fabricating two plasmonic metasurfaces on a single wafer to implement DONNs based on the structure from Geromel et al. [4]. This method consolidates the network into a single element, resolving alignment issues between layers and improving stability. We design a reflective configuration on a wafer, enabling DONN integration within 1 cm² and allowing for multilayer complexity. The metasurfaces process input light signals by leveraging precise phase modulation. In our simulations the designed system can achieve a classification accuracy of 93% with the Modified National Institute of Standards and Technology (MNIST) digits database.

[1] J. Hu et al., Nature Communications 15, 1525 (2024).
[2] A. I. Kuznetsov et al., ACS photonics 11, 816-865 (2024).
[3] A. Montes McNeil and Y. Li et al., Journal of Applied Physics 136, 033101 (2024).
[4] R. Geromel et al., Nano Letters 23, 3196-3201 (2023).

Professor Mark Brongersma

The Future of Metamaterials is Soft

Optical metamaterials offer unprecedented control over the flow of light by harnessing the light scattering properties of judiciously arranged nanostructures or molecules. Exciting new opportunities have recently emerged for the use of metamaterial optics in the fields of biology, wearables, medicine and neuroscience. These fields critically rely on the development of sophisticated technologies for the delivery and collection of complex light fields to understand, influence, and communicate with living systems. Examples include endoscopic imagers, optogenetic probes and wearable sensors. However, their development faces a notable materials challenge: most metasurfaces are currently fabricated from rigid, inorganic metal and semiconductor structures that do not interface well with the soft, curved, and dynamic surfaces that we encounter in biology. In my presentation, I will argue that soft materials can bring powerful advantages in the creation of nanostructured metasurface optical elements and photonic skins, such as flexibility, compliance, biocompatibility and large stimuli-driven responses.

Deepanshu Chaudhary

Nanowire Breath Sensors for Metabolic Health Diagnosis and Monitoring

Deepanshu Chaudhary a, Dawei Liu a, Yang Yu a, Saranya Shriram a, Kosala Dhanawansha a, Andrew
Materazzo a, Christopher Nolan b, Andrea Ranzoni c, H. Hoe Tan a, Chennupati Jagadish a, Lan Fu a
a Department of Electronic Materials Engineering, Research School of Physics, Australian National
University, Australia.
b Department of Diabetes and Endocrinology, The Canberra Hospital, Australia
c Agscent Pty Ltd, Australia

Breath acetone is a promising non-invasive biomarker associated with metabolic conditions in human and veterinary healthcare. Elevated concentrations of acetone in human and animal breath have been linked to altered metabolism in conditions like diabetic ketoacidosis (DKA) and ketosis [1,2]. Current diagnosis and monitoring of these conditions rely on blood tests which are invasive, inconvenient for frequent monitoring and challenging in veterinary settings. This motivates the development of a compact, non-invasive and rapid technique for metabolic health diagnosis and monitoring.

Here, we present a light activated InP nanowire array sensor for room temperature acetone sensing. The device comprises top-down etched InP nanowires with a platinum Schottky contact and a chitosan functionalization layer for acetone specific sensing. Nanowire arrays with diameter of 120 – 300 nm and pitch size of 500 – 1500 nm were fabricated using the process developed in previous study [3]. Systematic characterization demonstrated a concentration-dependent response from 50-800 ppm in controlled conditions and dry synthetic air covering the DKA range in humans. Translating from lab-based characterization to real breath samples introduces several challenges, in particular high relative humidity, variable O2 and CO2 content and background volatile organic compounds (VOCs). A lab-based breath analysis setup with corresponding humidity minimization, gas monitoring and analysis strategies have been developed to distinguish acetone specific signal from a complex breath matrix. Proof-of-concept clinical measurements on human DKA patient breath revealed a notably elevated acetone signal when compared to a healthy reference sample. Overall, this work demonstrates the potential of InP nanowire sensors as compact, room-temperature breath sensors for metabolic health monitoring, while identifying key challenges that need to be addressed for human and veterinary breath diagnostics.

The authors acknowledge Dr. Bronwyn Darlington (Agscent Pty Ltd) and Mr. Paul Carboon (Ketone Innovations/ Solentropy) for their valuable industry collaboration and support. This work was supported by the Australian Research Council (ARC), the Australian Government Department of Education, Australian Economic Accelerator (AEA) and the National Industry PhD Program. Device fabrication was carried out using facilities of the NCRIS Australian National Fabrication Facility (ANFF), including ANFF ACT and the Melbourne Centre for Nanofabrication (MCN).
[1] V. Saasa et al., Diagnostics 9, 224 (2019).
[2] P. Dobbelaar et al., Vet. Q. 18, 151 (1996).
[3] S. Wei et al., Adv. Sci. 11, 2309481 (2024).

Professor Irina Kabakova

Brillouin and quantum imaging

Label-free optical spectroscopies and imaging techniques are becoming increasingly popular for characterisation of live cells and tissues due to their non-contact and non-destructive nature to capture structure and physical properties of living matter. The growing evidence suggests that any form of exogeneous labelling perturbs the natural biological processes in cells and tissues and degrades the vitality of the sample, reaffirming the importance of developing high-sensitivity and specificity label-free imaging methods. In this talk, I will introduce two modes of label-free spectroscopic imaging my team established at the University of Technology Sydney: Brillouin microscopy and quantum mid-infrared (MIR) spectroscopic imaging. Brillouin microscopy is used for micromechanical mapping of living tissues, cells and biomaterials, while quantum mid-IR spectroscopy allows to reduce complexity and cost of instrumentation by shifting the detection and excitation wavelength range to visible wavelengths where many cheap and reliable equipment choices exist. Thus, together these two techniques can completement conventional toolbox of optical imaging methods, without the use of labels but with preserving a high degree of specificity in terms of mechanical and chemical contrast, respectively.

Rohini Ramachandran

Portable Multi-Wavelength Optical Sensor for Decentralised Haemoglobin Testing

Rohini Ramachandran a, b, Jean Pierre Ndabakuranye a, b , Shanmuga Sundar Dhanabalan c, Denise E. Jackson d, Sharath Sriram a, b, e, Madhu Bhaskaran a, b, e
a Functional Materials and Microsystems Research Group and the Micro Nano Research Facility, RMIT University, Melbourne, VIC, Australia
b ARC Centre of Excellence for Transformative Meta-Optical Systems, RMIT University, Melbourne, Australia
c Soft Electronics, Materials and Sensors Research Group, School of Computing, Engineering and Mathematical Sciences, La Trobe University, Melbourne, VIC, Australia
d School of Health and Biomedical Sciences, STEM College, RMIT University, Melbourne, Australia
e ARC Research Hub for Connected Sensors for Health, RMIT University, Melbourne, VIC, Australia