Professor Weibo Gao

A Tunable Entangled Photon-pair Source Based on a Van der Waals Insulator

Scalable quantum photonic devices drive the development of compact sources of entangled photons, which are pivotal for quantum communication, computing, and cryptography. In this work, we present entangled photon pair generation in rhombohedral boron nitride (r-BN), leveraging its unique optical and structural properties. Unlike conventional hexagonal boron nitride, which suffers from reduced nonlinear response due to centrosymmetric structure in even-layered stacks, r-BN features interlayer ABC stacking and maintains robust in-plane inversion symmetry. These characteristics lead to highly efficient entangled photon generation. Our system demonstrates an entangled photon pair generation rate up to 8667 Hz/(mW·mm) and offers a tunable platform for Bell state generation by simply adjusting the pump polarization, without compromising the entanglement quality or generation efficiency. The polarization entangled state is measured with a fidelity up to 94%. This advancement not only marks a significant step towards ultrathin, scalable quantum devices but also establishes r-BN as a promising candidate for on-chip integrated quantum optical applications.

Professor Jin Liu

Semiconductor Cavity Quantum Electrodynamics

Semiconductor quantum emitters, especially epitaxial quantum dots (QDs) with large optical oscillator strength, are one of the most promising candidates for exploring fundamental quantum physics in solid-state and building quantum photonic devices on-chip. In this talk, I will discuss the breakthrough of scalable and deterministic coupled cavity quantum electrodynamic systems (cQED) based on single-photon hyperspectral imaging[1]. With deterministically coupled QD-microcavity systems,we’ve observed the long-sought-after dynamic resonance fluorescence in cavity quantum electrodynamics[2] and realized quantum photonic devices with state-of-the-art performances, including bright sources of entangled photon pairs[3], single-photon sources carrying orbital angular momentum[4] and stimulated emission assisted single-photon sources[6]. We finally envision long-distance quantum networks based on telecom band QDs via hybrid integration technology[7].

References

[1] S. Liu et al., Super-resolved snapshot hyperspectral imaging of solid-state quantum emitters for high-throughput integrated quantum technologies. Nature Photon. 18 967(2024).

[2] S. Liu et al., Dynamic resonance fluorescence in solid-state cavity quantum electrodynamics. Nature Photon. 18 318 (2024).

[3] J. Liu et al., A solid-state source of strongly entangled photon pairs with high brightness and indistinguishability. Nature Nano. 14 586 (2019).

[4] B. Chen et al., Bright solid-state sources for single photons with orbital angular momentum. Nature Nano. 16 302 (2021).

[5] Y. Wei et al., Tailoring solid-state single-photon sources with stimulated emissions. Nature Nano. 17 470 (2022).

[6] Y. Yu et al., Telecom band quantum dot technologies for long-distance quantum networks. Nature Nano. 18 1389 (2023).

James Liddle-Wesolowski

Creation of Room Temperature Spin Active Quantum Emitters in Hexagonal Boron Nitride

Hexagonal boron nitride (hBN) is a two-dimensional Van der Waals material that can be treated to host quantum emitters. Furthermore, the discovery of a narrowband spin active emitter in hBN increases the materials potential for quantum sensing. This work covers the generation of visible emitters though annealing and emitter characterisation for spin analysis. Finding a reliable method to generate the spin active emitters at a high density would increase the number of emitters for characterisation, subsequently aiding the process of identifying spin active emitters. The emitter characterisation was performed on a confocal microscope, with the capability to record a photoluminescence (PL) map for identifying the spatial position of emitters along with the emitter density. The set-up was also connected to a spectrometer revealing information about the emitters zero-phonon line (ZPL). To determine if the generated emitters have quantum properties the second order correlation was measured. This work performed a comparison between undoped hBN and carbon doped hBN (c-hBN) finding the presence of carbon results in emitters with ZPLs at a longer wavelength and an increased rate of detecting spin active emitters. These results provide groundwork for the use of hBN visible quantum emitters in quantum sensing.

Professor Hannah Joyce 

THz Photonics and Related Applications

Gurpreet Singh

Spectral Reconstruction of MEMS Fabry–Pérot Filter

Spectral reconstruction is a technique used to estimate the full spectral response of a device from a limited set of available information. It will allow us to examine the device response without requiring an expensive and specialised set of equipment. This can be achieved utilising various algorithms such as prior-based methods and/or data-driven deep learning approaches. Spectral reconstruction of a device becomes even critical where the response of the device exceeds the instrument’s capabilities. This allows us to determine the true response of a device, rather than limiting it due to instrument resolution.

In this work, we are using the microelectromechanical systems (MEMS) based Fabry–Pérot filters (FPFs) [1-3] to validate the concepts. These MEMS-based FPFs were designed and fabricated at the University of Western Australia (UWA) in a microelectronics standard clean environment. The spectral response of these devices is also measured at UWA using a monochromator with a resolution exceeding that of the device. To validate the device response using data reconstruction, the device response is recorded under the broadband light using basic electronics instruments, such as a lock-in amplifier. The data reconstruction will be performed at the University of Melbourne. The preliminary work has started to achieve the desired outcome.  We are looking forward to presenting a preliminary proof-of-concept for the data reconstruction of MEMS-based FPFs for the passband wavelength ranging from 1.3 to 1.6 μm.

[1] Optical Microelectromechanical Systems Technologies for Spectrally Adaptive Sensing and Imaging, Advanced Functional Materials, Vol. 32, No. 3, 2103153, 14.01.2022.

[2] Investigation of MEMS-based spectrally adaptive Fabry-Pérot interferometers for long-wave infrared applications, Research output: Doctoral Thesis

[3] Large Area Silicon-Air-Silicon DBRs for Infrared Filter Applications, J. Lightwave Technol. 37, 769-779 (2019)

Ziwei Yang

Dual-Wavelength Multifunctional Metalenses in Mono-Crystalline Silicon Carbide for Quantum Emission Collection

Silicon carbide (SiC) has attained increased attention over the last decade due to its attractive optical properties, including a low loss in the visible and infrared spectrum, strong optical nonlinearity, and the presence of room-temperature quantum emitters [1]. To increase the collection efficiency of such emitters, the conventional solid immersion lenses can be replaced by monolithic metalenses, as demonstrated for diamond-based quantum emitters [2]. Recently mono-crystalline SiC metalenses have also been realized [3], confirming the feasibility of this approach. However, these demonstrations remain limited in functionality, typically operating at a single wavelength and for a single optical task. Extending SiC metalenses to multifunctional free-space operation—such as multi-wavelength collection and polarization-resolved emission control at different angles—has not yet been achieved, despite its importance for versatile next-generation quantum photonic applications.

In this work, we design and demonstrate a pair of multifunctional monolithic SiC metalenses, one operating at 860 nm and the other at 1240 nm, each capable of directing different polarizations to distinct focal positions. The 860 nm metalens targets emission from negative silicon monovacancy in 4H-SiC. These defects serve as optically addressable spin qubit applications, making them highly attractive for quantum technologies and scalable quantum photonic platforms [4]. The 1240 nm metalens collects emission near to the common defects in the 4H-SiC, whose zero-phonon line lies in the telecom O-band and is highly desirable for quantum communication and fiber-based networks. Both devices exhibit robust performance, efficiently capturing emissions from quantum emitters embedded near the surface of mono-crystalline SiC, and demonstrate the potential of multifunctional SiC metalenses as scalable building blocks for integrated and free-space quantum photonic platforms.

[1] Room temperature coherent control of defect spin qubits in SiC, Nature 479, 84 (2011).

[2] A monolithic immersion metalens for imaging solid-state quantum emitters, Nat. Commun. 10, 2392 (2019).

[3] Monolithic silicon carbide metalenses. ACS Photonics 9.4 (2022): 1409-1414.

[4] High-fidelity spin and optical control of single silicon-vacancy centres in silicon carbide. Nature communications 10.1 (2019): 1954.

Joshua Jordaan

III-V Metasurface Lasers for Compact and Directional NIR Emission

Planar metasurfaces provide a compact platform for laser cavities and output couplers, combining subwavelength modal control with wafer-scale fabrication and seamless integration with diverse gain media [1], [2]. By tailoring the unit-cell geometry and exploiting symmetry, metasurfaces can support resonances with long radiative lifetimes while maintaining free-space addressability. These modes enable strong field confinement, narrow linewidths, and efficient vertical emission. Recent demonstrations have shown devices consisting of dielectric metasurfaces, coated with gain media cladding after patterning, that lase into high-Q, dispersionless modes [3], [4]. Such flat-band resonances enhance light-matter interaction through suppressed group velocity and increased density of states, offering opportunities for collective and nonlinear effects in nanophotonic light sources.

In this work, we report the characterisation of near-infrared (NIR) metasurface lasers patterned directly on epitaxially lifted-off III-V semiconductor membranes. The devices are optimised to exploit flat-band modal engineering for efficient lasing. Epitaxial lift-off (ELO) decouples the active III-V gain stack from the growth substrate, enabling wafer reuse and transfer onto low-index transparent hosts. This configuration enhances index contrast for stronger confinement and permits backside optical pumping through the substrate, simplifying integration, packaging, and scalability of compact metasurface-based lasers.

[1]        S. T. Ha et al., ‘Directional lasing in resonant semiconductor nanoantenna arrays’, Nature Nanotech, vol. 13, no. 11, pp. 1042–1047, Nov. 2018, doi: 10.1038/s41565-018-0245-5.

[2]        D. Wen and K. B. Crozier, ‘Metasurfaces 2.0: Laser-integrated and with vector field control’, APL Photonics, vol. 6, no. 8, p. 080902, Aug. 2021, doi: 10.1063/5.0057904.

[3]        S. Eyvazi, E. A. Mamonov, R. Heilmann, J. Cuerda, and P. Törmä, ‘Flat-Band Lasing in Silicon Waveguide-Integrated Metasurfaces’, ACS Photonics, vol. 12, no. 3, pp. 1570–1578, Mar. 2025, doi: 10.1021/acsphotonics.4c02332.

[4]        T. T. H. Do et al., ‘Room-Temperature Lasing at Flatband Bound States in the Continuum’, ACS Nano, vol. 19, no. 20, pp. 19287–19296, May 2025, doi: 10.1021/acsnano.5c01972.

Professor Christina Lim

Radio-over-Fibre Technology

Professor Yang Chai

Bioinspired In-Sensor Computing for Artificial Vision

The demand for accurate perception of the physical world leads to a dramatic increase in sensory nodes. However, the transmission of massive and unstructured sensory data from sensors to computing units poses great challenges in terms of power‐efficiency, transmission bandwidth, data storage, time latency, and security. To efficiently process massive sensory data, it is crucial to achieve data compression and structuring at the sensory terminals. In‐sensor computing integrates perception, memory, and processing functions within sensors, enabling sensory terminals to perform data compression and data structuring. In this talk, I will describe our team’s efforts towards bioinspired in-sensor computing for artificial vision. I will talk about the framework of the in-sensor computing and demonstrate a few vision sensors for different scenarios, including visual adaptation, motion perception, as well as event-driven vision sensors for spiking neural network.

References

[1] Nature Electronics, 2022, 5, 84-91

[2] Nature, 2022, 602, 364

[3] Nature Electronics, 2020, 3, 664-671

[4] Nature, 2020, 579, 32-33

[5] Nature Nanotechnology, 2019, 14, 776-782

[6] Nature Electronics, 2022, 5, 483-484

[7] Nature Nanotechnology, 2023, 18, 882-888

[8] Nature Electronics, 2023, 6, 870-878

[9] Nature Nanotechnology, 2024, 19, 919-930

[10] Nature Electronics, 2024, 7, 705-713

[11] Nature Electronics, 2025, 8, 147-156

[12] Nature Electronics, 2025, 8, 680-688.

Jiajun Meng

Design and Demonstration of Polarisation – Resolved Ge Metalenses for MWIR Imaging

Emerging optical components based on metamaterials and metasurfaces, particularly metalenses, are
transforming conventional infrared (IR) imaging systems by offering compact, lightweight, and cost-effective
alternatives to bulky refractive optics. Traditional IR lenses are typically expensive and heavy, limiting their
use in drones, handheld devices, and wearable imaging platforms. Here, we report the design, modelling,
fabrication, and demonstration of flat mid-wave infrared (MWIR) metalenses based on ultra-thin germanium (Ge) pillars on a silicon (Si) substrate, optimised for operation at 3.3 µm wavelength. In addition to a conventional design, we explore a polarisation-sensitive configuration that enables polarisation splitting,
providing spatially-resolved polarisation contrast and opening pathways for enhanced imaging modalities in
the MWIR.

Numerical modelling efforts, including rigorous coupled-wave analysis (RCWA), were used to construct a
pillar-based phase library and guide metalens performance optimisation. Two types of Ge metalenses were
fabricated: (i) a polarisation-insensitive version using circular pillars (1.5 mm aperture, 4 mm focal length),
and (ii) a polarisation-sensitive version using rectangular pillars for dual-spot focusing (1.5 mm aperture, 3
mm focal length). A subwavelength pillar pitch of 1.1 µm was selected to suppress higher-order diffraction
losses while keeping the fabrication process practical. Infrared imaging tests were performed using FLIR
Lepton uncooled microbolometer arrays with heat sources (e.g., HPIR103). Fabrication quality was confirmed via SEM imaging; incomplete etching (~0.42 µm) degraded imaging contrast, whereas fully etched structures (~1.35 µm) produced significantly improved performance. The polarisation-sensitive metalens demonstrates polarisation-resolved MWIR imaging, offering additional contrast mechanisms and sensing capabilities beyond conventional intensity-based imaging. This study highlights the feasibility of MWIR imaging with flat metalenses and underscores their strong potential for scalable, wafer-level, batch-compatible manufacturing.
The approach is readily extendable to the long-wave infrared (LWIR) regime, paving the way for compact,
lightweight, and mass-producible infrared imaging systems across multiple spectral bands.

Professor Hai Son Nguyen

Engineering Flatbands and Unidirectional Emission in Bilayer Photonic Metasurfaces

Yang Yu

Indium Arsenide Nanowire Array Based Spectrometer for Extended-SWIR Applications

The short-wave infrared (SWIR) wavelengths (1–3 μm), characterized by strong molecular absorption features and low scattering loss, is critical for advanced applications in biomedical imaging, environmental sensing, and industrial monitoring. Traditional spectroscopy in this range relies on bulky and expensive Fourier transform infrared (FTIR) systems, which often requiring cryogenic cooling and thereby limits their integration into compact and portable systems.
In this work, we present a high-performance, filter-free SWIR photodetector and on-chip spectrometer based on InAs/InP/ITO radial p–n heterojunction nanowire (NW) arrays. By incorporating a strain-relieving, double-graded InAsP buffer and a thin InP shell passivation layer, we grow high-quality p-type InAs NW arrays with large, tunable diameters on lattice-mismatched p-type InP substrates using selective area metal-organic chemical vapor deposition. The resulting devices exhibit broadband SWIR photodetection from 1 to 3.3 μm at room temperature. Our photodetectors deliver excellent performance, with peak responsivity up to 0.25 A/W at room temperature (and 0.38 A/W at 150 K), detectivity up to 2.43×10⁹ (300 K) and 1.81×10¹¹ cm·Hz1/2/W (150 K), and high-speed modulation beyond 60 kHz. By tailoring the NW array geometry, we realize wavelength-tunable photodetection across the extended-SWIR (eSWIR) band (1500–2700 nm), all grown on the substrate from the same epitaxial growth. High resolution (305×305 pixels) multispectral imaging is also demonstrated under white light, 1550 nm, and 2200 nm illumination.
Furthermore, by integrating 16 spectrally distinct photodetector arrays onto a single chip with each array functioning as a narrowband pixel with tailored responsivity, and using computational reconstruction algorithms, we demonstrate broadband spectrometry from 1 to 3 μm with a spectral resolution of ~7 nm. As a proof of concept, we reconstruct the transmission spectrum of water and resolve key absorption peaks at 1685 nm and 2210 nm, highlighting the platform’s potential for compact, chip-scale material identification and environmental sensing in the SWIR domain.

Dawei Liu

Broadband Miniature Computational Spectrometer with a Vortex Retarder

Optical spectrometers are essential for studying light-matter interactions, but traditional designs are often complex and bulky. Recent advancements have focused on miniaturized spectrometers for compact and cost-effective applications, relying on recalibrated response functions of nanophotonic structures [1-4]. However, these techniques require precise design and fabrication, posing challenges in balancing size reduction with performance. Here, we introduce an ultra-broadband miniature computational spectrometer using a q-plate vortex retarder between crossed polarizers. The q-plate generates spatially varying birefringence, creating distinctive intensity patterns under different wavelength light, which are captured by a complementary metal oxide semiconductor (CMOS) camera. We use artificial intelligence to extract features from the captured intensity patterns, with spectral reconstruction achieved using Gaussian basis functions and regularization techniques. This enables high-resolution spectral measurements across a broad wavelength range from 400 nm to 1500 nm with sub-nanometre accuracy. Our spectrometer demonstrates a spectral peak location accuracy better than 1 nm and can resolve peaks separated by 3 nm in a bimodal spectrum. This compact design offers a scalable and high-performance solution for miniature optical spectrometers. It is suitable for various fields, including environmental monitoring and biomedical imaging. The integration of advanced computational techniques and novel materials ensures robust and reliable spectral data analysis, reducing the need for precise component alignment and extensive calibration.

[1] Deng, W., et.al. Electrically tunable two-dimensional heterojunctions for miniaturized near-infrared spectrometers. Nature Communications,  2022. 13(1), p.4627.

[2] Uddin, M.G. et.al. Broadband miniaturized spectrometers with a van der Waals tunnel diode. Nature Communications,  2024.15(1), p.571.

[3] Yuan, S, et. al. A wavelength-scale black phosphorus spectrometer. Nature Photonics,  2021. 15(8), pp.601-607.

[4] Yoon, H.H., et. al.. Miniaturized spectrometers with a tunable van der Waals junction. Science,  2022. 378(6617), pp.296-299.

Lincoln Clark

Infrared to Visible Image Processing by a Nonlinear LiNbO3 Metasurface
Using Structured Light

Image processing techniques play a critical role in emerging technologies such as autonomous driving, biometric verification, and AR/VR systems [1]. These computation tasks have been performed using digital computers, but the growing demand for speed, power efficiency, and real-time performance is driving innovation beyond conventional architectures. In the IR wavelength regime, image processing using night vision cameras is more complex due to weak signals and the difficulty in extracting fine details [2]. While direct light-to-light conversion via nonlinear processes like sum-frequency generation (SFG) has been used for image conversion, it has not yet been applied to optical image processing. GaAs and LiNbO3 metasurfaces have demonstrated efficient direct light-to-light conversion with promising imaging performance [3, 4]. However, these methods focused solely on wavelength conversion, not on optical image processing. In this work, we perform IR to visible image processing using a nonlocal LiNbO3 metasurface and vortex mirrors with topological charges of 0, 1 and 2 (Fig 1. a).
We compare the processed images with those from the case of charge 0, that corresponds to the standard mirror, serving as a control reference (Fig 1. b). Our results open new opportunities for imaging of transparent biological objects, advanced security systems, and autonomous navigation.

1. Jing, J., Liu, S., Wang, G., Zhang, W. & Sun, C. Recent advances on image edge detection: A comprehensive review. Neurocomputing 503, 259–271. ISSN: 0925-2312 (2022).
2. Ashiba, H. I. & Ashiba, M. I. Super-efficient enhancement algorithm for infrared night vision imaging system. Multimedia Tools and Applications 80, 9721–9747. ISSN: 1573-7721 (2021).
3. Morales, M. C. et al. Infrared imaging in nonlinear GaAs metasurfaces in Proc.SPIE 11201 (Dec. 2019),
112011S.
4. Valencia Molina, L. et al. Enhanced Infrared Vision by Nonlinear Up-Conversion in Nonlocal Metasurfaces. Advanced Materials 36, 2402777 (2024).

Professor Goki Eda

Exciton Photonics with Atomically Thin Semiconductors

Two-dimensional (2D) van der Waals semiconductors such as monolayer MoS₂ and WSe₂ have emerged as versatile building blocks for photonic devices, owing to their strong excitonic resonances and rich many-body physics. In this tutorial-style talk, I will trace the development of exciton photonics with 2D semiconductors – from the discovery of their fundamental optical properties to recent advances in device integration and quantum light sources. I will then highlight a few recent directions from our group: the observation of an unusual upconversion electroluminescence phenomenon in plasmonic tunnel junctions [1]; and single-photon emission from impurity-bound excitons in substitutionally doped monolayers [2]. These examples illustrate how coupling excitonic materials with nanoscale architectures and precise chemical engineering can open new avenues for optoelectronic and quantum photonic applications. I will conclude with a brief outlook, pointing to symmetry engineering and interfacial ferroelectricity as emerging degrees of freedom that may further expand the potential of 2D semiconductors for novel applications.

[1] Wang et al. “Upconversion electroluminescence in 2D semiconductors integrated with plasmonic tunnel junctions” Nature Nanotech. (2024)

[2] Loh et al. “Nb impurity-bound excitons as quantum emitters in monolayer WS₂” Nature Comm. 15, 10035 (2024)

Peter Elango

A Compact Optical Sensor to Self-Assess Skin Health After Sun Exposure

Excessive sun exposure is the major environmental risk factor for melanoma and other types of skin cancer.
Reducing cumulative exposure to ultraviolet (UV) radiation and avoiding repeated, sporadic episodes of acute photodamage can drastically lower this risk. Photodamage after sun exposure can be assessed by monitoring erythema – skin redness – and increased pigmentation, both key indicators of excessive UV exposure. In this work, we present a compact optical device designed to monitor changes in pigmentation and erythema through reflectance measurements using four micro-LEDs, emitting at 405 nm, 572 nm, 650 nm and 700 nm and a photodiode with extended visible-NIR sensitivity. Monte Carlo simulations were conducted to optimise the device design by evaluating light penetration into skin tissue as a function of source-to-detector distance to target key chromophores. The device was validated using skin-mimicking tissue phantoms with controlled concentrations of coffee, with similar optical properties to melanin, and haemoglobin to simulate changes in pigmentation and erythema, respectively. Using a signal-to-noise ratio threshold of 2, we were able to detect changes in pigmentation as small as 5% across all phototypes, and erythema changes in lighter skin tones. This miniaturised device shows potential for personalised skin monitoring in therapeutic, cosmetic, and diagnostic applications.

[1] Tang, X., Yang, T., Yu, D., Xiong, H. & Zhang, S. Current insights and future perspectives of
ultraviolet radiation (UV) exposure: Friends and foes to the skin and beyond the skin. Environment
International, 108535 (2024).
[2] McDaniel, D., Farris, P. & Valacchi, G. Atmospheric skin aging—Contributors and inhibitors. Journal
of Cosmetic Dermatology 17, 124–137 (2018).
[3] Brozyna, A. et al. Mechanism of UV-related carcinogenesis and its contribution to nevi/melanoma.
Expert Review of Dermatology 2, 451–469 (2007).

Professor Mark Brongersma