Nature-inspired research can leverage millions of years of evolutionary adaptation to pioneer cutting-edge technological solutions. The sophisticated visual system of the mantis shrimp, for example, has motivated the development of simultaneous spectral and polarimetric imaging (SPI) systems. While conventional silicon-based CMOS platforms face limitations due to the material bandgap and rely on complex optical assemblies, perovskite-based detectors offer a compelling alternative. Their tunable broadband spectral absorption and solution processability facilitate highly integrated device architectures. Herein, we present an ultra-compact SPI camera realized using multispectral perovskite photodetector array. Engineering of perovskite composition and a stacked filter strategy are used to tailor and sharpen detectors' spectral responses across the visible range. A cost-effective digital mirror device implementing structured light patterns, coupled with a computational imaging algorithm, allows for SPI with only a single super-pixel, circumventing challenges in large area production of identical perovskite pixels. SPI with 17 spectral and 4 polarization channels, a high spatial resolution of 256 x 256 pixels, and conduct accurate spectral measurements with significant anti-glare capabilities is demonstrated. This low-cost, flexible platform shows promise for a wide range of applications, from scientific research and industrial quality control to enhanced surveillance and navigation systems in visually challenging environments.

The burgeoning field of computational spectrometers is rapidly advancing, providing a pathway to highly miniaturized, on-chip systems for in-situ or portable measurements. The performance of these systems is typically limited in its encoder section. The response matrix is largely compromised with redundancies, due to the periodic intensity or overly smooth responses. As such, the inherent interdependence among the physical size, resolution, and bandwidth of spectral encoders poses a challenge to further miniaturization progress. Achieving high spectral resolution necessitates a long optical path length, leading to a larger footprint required for sufficient spectral decorrelation, resulting in a limited detectable free-spectral range (FSR). Here, we report a groundbreaking ultra-miniaturized disordered photonic molecule spectrometer that surpasses the resolution-bandwidth-footprint metric of current spectrometers. This computational spectrometer utilizes complicated electromagnetic coupling to determinately generate quasi-random spectral response matrices, a feature absents in other state-of-the-art systems, fundamentally overcoming limitations present in the current technologies. This configuration yields an effectively infinite FSR while upholding a high Q-factor ( > 7.74 × 105). Through dynamic manipulation of photon frequency, amplitude, and phase, a broad operational bandwidth exceeding 100 nm can be attained with an ultra-high spectral resolution of 8 pm, all encapsulated within an ultra-compact footprint measuring 70 × 50 μm². The disordered photonic molecule spectrometer is constructed on a CMOS-compatible integrated photonics platform, presenting a pioneering approach for high-performance and highly manufacturable miniaturized spectroscopy.

Generation of light patterns through computer-generated holography is limited by spatial light modulators with finite resolution and pixel pitch, and their ability to modulate only either phase or amplitude of light. These limitations result in finite far field sampling and speckle-like noise. In this study, we consider the signal bandwidth of the propagating wavefront to understand the cause of the noise and to develop a new algorithm for simultaneously generating a batch of phase-only holograms using gradient descent. When displayed in sequence, the holograms improve the time-averaged quality and increase the resolution of the projected reconstructed image compared to alternative approaches. We verify the results both numerically and experimentally. This method will benefit precision-critical fields such as holographic photolithography.

3D in-substrate integration of optical functionalities fully utilizes the vertical dimension of space and is valuable for advancing next-generation integrated optoelectronics. However, as a key optical effect, optical dispersion remains unavailable to be tailored at the microscale in 3D. We introduce artificial dispersive microregions in lithium niobate crystals to engineer free-space ultra-broadband optical dispersion. The microregions are formed by ultrafast laser-induced sub-wavelength phase-transition nanostripes, which modulate the crystal's birefringence to establish localized frequency-dependent interference of ordinary and extraordinary light. This approach operates across an ultra-broad wavelength range (>1300 nm) within an exceptionally compact volume (50 × 10 × 6 µm³), and allows for precise, on-demand dispersion control in 3D space. The dispersive microregions exhibit viewing-angle independence, stability to harsh conditions (600 °C high temperature, contamination, corrosion, and mechanical damage), and wide applicability across various birefringent crystals. We demonstrate the versatility of our method in developing broadband on-chip micro-spectrometers and applications of spectral imaging, information recording, and encryption.

Terahertz (THz) spectroscopy is a non-contact technique well-suited for probing the ultrafast electrical conductivity of semiconductor nanostructures, where conventional methods are often impractical. However, geometric resonances in these nanostructures can distort the measured THz response, complicating the extraction of the intrinsic material properties. Here, we use THz spectroscopy to study GaAs nanowires of varying lengths and observe that the resonant frequency increases as the nanowire length decreases. Further measurements on a model system of well-defined GaAs microsquares (ranging in size from 500 × 500 to 7 × 7 μm2) confirmed the relationship between structure size and resonant frequency. We verify that a plasmon-based model successfully separates the geometric response from the intrinsic charge-carrier response. Thus, the model allows for the accurate evaluation of critical material properties in nanostructured semiconductors, such as electron mobility. Fluence-dependent measurements and finite-difference time-domain simulations confirm the plasmonic nature of the resonances.

Covalently-bonded lateral 2D heterostructures offer unique (opto)electronic functionalities and can be deposited during a single growth process. However, the position of lateral junctions is typically uncontrolled due to random nucleation processes, which necessitates post-growth identification of suitable heterojunction regions for device integration. Here, ellipsometric contrast microscopy (ECM) is demonstrated to evaluate 2D lateral monolayer MoSe2-WSe2 and MoS2-WS2 heterostructures, which enables rapid imaging with high material-contrast down to sub-nanometer thickness for high-throughput characterisation of heterostructure domains. In addition, a computer vision algorithm provides precise identification of individual monolayer heterostructure junctions and their integration into rectifying devices and photodetectors. These results establish the advantages of ECM for reliable, fast characterization and large-scale integration of atomically thin 2D heterostructures into advanced optoelectronic devices, with potential extension to other nanomaterials.

Spinel materials offer excellent physical, optical, and biomedical properties, particularly in epitaxial form. However, spinel electrode materials for these epitaxial films are limited. While NiCo2O4 (NCO) is a high-performing conductive spinel, it loses conductivity above 400 °C, making it unsuitable as an electrode for overgrown functional spinel layers, which typically require growth above 600 °C. Here, we demonstrate the stabilization of conducting NCO through the overgrowth of a functional spinel CoFe2O4 (CFO) layer. Notably, when the NCO is capped with 625 °C-grown CFO, it retains most of the conductivity of 350 °C-grown films. The overgrowth approach of this work shows a path for NCO to be used as a conducting electrode in epitaxial spinel-based epitaxial devices.

Holography is a diffractive method to record and reconstruct wavefronts using both amplitude and phase information of light. Compared to conventional imaging optics, holography offers greater control on light using computational methods and robust corrections[1]–[3]. This allows using simpler optical setups with fewer physical components, easier methods of alignment and delocalised aberration corrections[4]. In this work we discuss how multiphase computer-generated holograms (CGH) displayed on liquid crystal on silicon (LCOS) spatial light modulators (SLM) can be used to perform maskless lithography by reconstructing custom targets.

A quantum point contact (QPC)-a constriction in a semiconducting two-dimensional electron system with a quantized conductance-is a building block of novel spintronic and topological electronic circuits. QPCs can also be used as readout electronics, charge sensors, or switches in quantum nanocircuits. A short and impurity-free constriction with superconducting contacts is a Cooper-pair QPC analogue known as a superconducting quantum point contact (SQPC). The technological development of such quantum devices has been prolonged due to the challenges of maintaining their geometrical requirement and nearmaterial and device engineering techniques and report on an innovative realization of nanoscale hybrid SQPC arrays with split gate technology in semiconducting 2D electron systems. We exploit the special gate tunability of the quantum wells, and demonstrate the first experimental observation of conductance quantization in hybrid InGaAs-Nb SQPCs. We observe reproducible quantized conductance at zero magnetic fields in multiple quantum nanodevices fabricated in a single chip and systematically investigate the quantum transport of SQPCs at low and high magnetic fields for their potential applications in quantum metrology, for extremely accurate voltage standards, and fault-tolerant quantum technologies.

Arrays of nanowire-based photoconductive antennas hold potential for hyperspectral imaging in the terahertz range. InAs nanowires were selected for their high electron mobility, tunable charge carrier lifetimes and small footprints. We investigate different nanowire crystal structures (zinc-blende and metastable wurtzite), different diameters and different surface treatments to achieve phase sensitive detectors of terahertz radiation that can be integrated into an array suitable for hyperspectral terahertz imaging. Machine vision identification of nanowires and automated electrode routing processes are employed to generate arrays of nanowire photoconductive antennas, even from initial distributions of randomly and irregularly located nanowires.

Optical spectroscopy plays an essential role across scientific research and industry for non-contact materials analysis1-3, increasingly through in-situ or portable platforms4-6. However, when considering low-light-level applications, conventional spectrometer designs necessitate a compromise between their resolution and sensitivity7,8, especially as device and detector dimensions are scaled down. Here, we report on a miniaturizable spectrometer platform where light throughput onto the detector is instead enhanced as the resolution is increased. This planar, CMOS-compatible platform is based around metasurface encoders designed to exhibit photonic bound states in the continuum9, where operational range can be altered or extended simply through adjusting geometric parameters. This system can enhance photon collection efficiency by up to two orders of magnitude versus conventional designs; we demonstrate this sensitivity advantage through ultra-low-intensity fluorescent and astrophotonic spectroscopy. This work represents a step forward for the practical utility of spectrometers, affording a route to integrated, chip-based devices that maintain high resolution and SNR without requiring prohibitively long integration times.

Nanoscale material systems are central to next-generation optoelectronic and quantum technologies, yet their development remains hindered by limited characterization tools, particularly at terahertz (THz) frequencies. Far-field THz spectroscopy techniques lack the sensitivity for investigating individual nanoscale systems, whereas in near-field THz nanoscopy, surface states, disorder, and sample-tip interactions often mask the response of the entire nanoscale system. Here, we present a THz resonance-amplified near-field spectroscopy technique that can detect subtle conductivity changes in isolated nanoscale systems─such as a single InAs nanowire─under ultrafast photoexcitation. By exploiting the spatial localization and resonant field enhancement in the gap of a bowtie antenna, our approach enables precise measurements of the nanostructures through shifts in the antenna resonant frequency, offering a direct means of extracting the system response, and unlocking investigations of ultrafast charge-carrier dynamics in isolated nanoscale and microscale systems.

In this paper, we present a reconfigurable multiplex (MUX) setup that increases the throughput of electrical characterisation at cryogenic temperature. The setup separates the MUX circuitry from quantum device under test (qDUT), allowing qDUT chips to be exchanged easily and MUX chips to be reused. To interface with different types of qDUTs, board-level designs are incorporated to allow interconnects flexibly routed into different topology. MUXs are built based on a multiple level selective gating (MLSG) scheme, where the number of multiplexed output channels (interconnects) is exponentially dependent on the number of control lines. In the prototype setup presented in this paper, with 14 out of 44 existing wires from room temperature, 4 MUXs at cryogenic temperature can supply in total 128 interconnects to interface with qDUTs. We validate the MUX setup operation and assess the various limits existed by measuring k$\Omega$ resistors made of $\mu$m-size graphene ribbons. We further demonstrate the setup by performing charge transport measurement on 128 nm-size graphene quantum devices in a single cooling down.

Ultra-thin solar cells, an order of magnitude thinner than conventional technologies, are an emerging device concept that enables low-cost, flexible, lightweight, and defect-tolerant photovoltaics. However, the advent of ultra-thin technologies is hindered by the fundamental challenge of poor light harvesting in thinnest absorber layers, which entails prohibitive photocurrent and efficiency penalties. Here, from a tutorial perspective, we review different light-management platforms that can overcome this inherent limitation, namely, antireflection coatings, rear mirrors, and light-trapping textures. We then review the state-of-the-art performances that have been achieved with these strategies and that have led to records of ∼20% efficiency in ∼200 nm absorbers. Finally, we identify persisting challenges and potential development avenues for attaining competitive performance with ever-thinner photovoltaic devices.

Active wavelength-scale optoelectronic components are widely used in photonic integrated circuitry, however coherent sources of light - namely optical lasers - remain the most challenging component to integrate. Semiconductor nanowire lasers (NWLs) represent a flexible class of light source where each nanowire (NW) is both gain material and cavity; however, strong coupling between these properties and the performance leads to inhomogeneity across the population. While this has been studied and optimized for individual material systems, no architecture-wide insight is available. Here, nine NWL material systems are studied and compared using 55,516 NWLs to provide statistically robust insight into performance. These results demonstrate that, while it may be important to optimize internal quantum efficiency for certain materials, cavity effects are always critical. The study provides a roadmap to optimize the performance of NWLs made from any material: this can be achieved by ensuring a narrow spread of lengths and end-facet reflectivities. The properties of 55 516 individual nanowire lasers, with nine different designs, are measured using high-throughput optical characterization. This enables a statistically robust comparison of the performance of each design, and the identification of the globally significant factors that impact the lasing performance. image

Conventional spectrometer designs necessitate a compromise between their resolution and sensitivity, especially as device and detector dimensions are scaled down. Here, we report on a miniaturizable spectrometer platform where light throughput onto the detector is instead enhanced as the resolution is increased. This planar, CMOS-compatible platform is based around metasurface encoders designed to exhibit photonic bound states in the continuum, where operational range can be altered or extended simply through adjusting geometric parameters. This system can enhance photon collection efficiency by up to two orders of magnitude versus conventional designs; we demonstrate this sensitivity advantage through ultralow-intensity fluorescent and astrophotonic spectroscopy. This work represents a step forward for the practical utility of spectrometers, affording a route to integrated, chip-based devices that maintain high resolution and SNR without requiring prohibitively long integration times.

Understanding the growth mechanisms of III-nitride nanowires is of great importance to realise their full potential. We present a systematic study of silane-assisted GaN nanowire growth on c-sapphire substrates by investigating the surface evolution of the sapphire substrates during the high temperature annealing, nitridation and nucleation steps, and the growth of GaN nanowires. The nucleation step - which transforms the AlN layer formed during the nitridation step to AlGaN - is critical for subsequent silane-assisted GaN nanowire growth. Both Ga-polar and N-polar GaN nanowires were grown with N-polar nanowires growing much faster than the Ga-polar nanowires. On the top surface of the N-polar GaN nanowires protuberance structures were found, which relates to the presence of Ga-polar domains within the nanowires. Detailed morphology studies revealed ring-like features concentric with the protuberance structures, indicating energetically favourable nucleation sites at inversion domain boundaries. Cathodoluminescence studies showed quenching of emission intensity at the protuberance structures, but the impact is limited to the protuberance structure area only and does not extend to the surrounding areas. Hence it should minimally affect the performance of devices whose functions are based on radial heterostructures, suggesting that radial heterostructures remain a promising device structure.