Dynamic reconfiguration of bound-state-in-the-continuum (BIC) microlasers typically involves mode hopping or angle switching, which compromises mode consistency and beam topology. Here, we demonstrate a phase-change Sb2S3 nanodisk metasurface microlaser that enables nonvolatile multilevel wavelength programming while preserving the same symmetry-protected quasi-BIC lasing mode and surface-normal emission. The device exhibits vertical lasing with a linewidth of similar to 0.4 nm and Q-factors exceeding 3000. By laser writing of amorphous, intermediate, and crystalline states, the lasing wavelength is tuned from 881 to 889 nm without optical-mode switching or beam steering. Polarization-resolved far-field measurements together with interference analysis confirm vortex-beam emission with a conserved topological charge (q = -1) throughout the programmed tuning sequence. These results establish Sb2S3 quasi-BIC metasurfaces as a compact platform for programmable structured-light microlasers and integrated photonic systems.

Thermoelectric materials can be designed to support optical resonances across multiple spectral ranges to enable ultra-wide band photodetection. For instance, antimony telluride (Sb2Te3) chalcogenide exhibits interband plasmonic resonances in the visible range and Mie resonances in the mid-infrared (mid-IR) range, while simultaneously possessing large thermoelectric Seebeck coefficients. In this paper, we designed and fabricated Sb2Te3 metasurface devices to achieve resonant absorption for enabling photodetectors operating across an ultra-wideband spectrum, from visible to mid-IR. Furthermore, relying on asymmetric Sb2Te3 metasurface, we demonstrated the thermoelectric photodetectors with polarization-selectivity. This work provides a potential platform towards the portable ultrawide band spectrometers at room temperature, for environmental sensing applications.

Sb2Te3 and Ge2Sb2Te5 (GST) are important materials used in phase-change photonic devices. We investigated the tunable optical properties of Sb2Te3, demonstrating its potential for continuous tuning from metallic-like to dielectric behavior through intermediate amorphous states. Using a resonant thin-film structure, we explored how Sb2Te3 may enable continuous color modification. We have also designed and simulated optical reflectors to enhance color tuning by gradually disordering the Sb2Te3 crystal structure. These results suggest that gradual changes in the optical properties of Sb2Te3 could be potentially used for future visible photonic applications, such as zero-static power tunable color reflective displays.

Tuning quantum emission to a specific wavelength at room temperature holds significant promise for enhancing secure quantum communication, particularly by aligning with the Fraunhofer lines in the solar spectrum. The integration of quantum emitters with phase-change materials enables emission wavelength modulation, especially when strong field enhancement is present. Antimony telluride (Sb2Te3) exhibits the potential to facilitate this functionality through its support of interband plasmonics and phase-change behavior. In this study, Sb₂Te₃ antennae are designed and fabricated to tune the emission energy of adjacent perovskite quantum dots (QDs) by over 570 meV. The underlying mechanism involves the localized surface plasmons (LSPs) on Sb₂Te₃ nanostructures, which exhibit a surface-enhanced Landau damping process that facilitates the decay of LSPs into electron-hole pairs. The generated hot electrons are then injected into perovskite QDs via the microscopic electron transport process, which can be triggered by the transition of Sb2Te3 from amorphous to a crystalline state, resulting in a significant emission energy shift from 1.64 to 2.21 eV. Furthermore, the emission energy of perovskite QDs on crystalline Sb₂Te₃ nanoantennae can be modulated through DC voltage bias, highlighting the potential for extensive wavelength tunability of quantum emitters integrated with electronic systems.

Thermoelectric photodetectors are robust alternatives to photodiodes with applications in extreme environments; however, the poor absorptivity of thermoelectric materials limits their photosensitivity. Here, we take a new look at the traditional thermoelectric materials Sb2Te3 and Bi2Te3 in their recently discovered ability to support interband plasmonic resonances in the visible spectrum. We fabricated nanoresonators directly into the thermoelectric materials to improve their optical absorptance through plasmonic field enhancements, leading to improved photo-thermoelectric conversion. A thermoelectric detector with Sb2Te3 and Bi2Te3 nanostructures demonstrated ∼90 % optical absorptance across the visible spectrum, more than twice that of unpatterned materials. The solid-state device was fabricated on a substrate and exhibited a response time of 160 µs and a specific detectivity of 3.2×106cm Hz12W−1 $\left.3.2{\times}1{0}^{6} \text{cm\,H}{\text{z}}^{1/\right.2} {\text{W}}^{-1}$ . Our demonstration that plasmonic and thermoelectric properties can be exploited within the same material could advance photodetectors and other optoelectronic technologies, such as biosensors, solar cells, and integrated spectrometers.

Introduction: Taking an ear impression is a minimally invasive procedure. A review of existing literature suggests that contactless methods of scanning the ear have not been developed. We proposed to establish a correlation between external ear features with the ear canal and with this proof of concept to develop a prototype and an algorithm for capturing and predicting ear canal information. Methods: We developed a novel prototype using structured light imaging to capture external images of the ear. Using a large database of existing ear impression images obtained by traditional methods, correlation analyses were carried out and established. A deep neural network was devised to build a predictive algorithm. Patients undergoing hearing aid evaluation undertook both methods of ear impression-taking. We evaluated their subjective feedback and determined if there was a close enough objective match between the images obtained from the impression techniques. Results: A prototype was developed and deployed for trial, and most participants were comfortable with this novel method of ear impression-taking. Partial matching of the ear canal could be obtained from the images taken, and the predictive algorithm applied for a few sample images was within good standard of error with proof of concept established. Discussion: Further studies are warranted to strengthen the predictive capabilities of the algorithm and determine optimal prototype imaging positions so that sufficient ear canal information can be obtained for three-dimensional printing. Ear impression-taking may then have the potential to be automated, with the possibility of same-day three-dimensional printing of the earmold to provide timely access.

. Guest editors Nathan Youngblood, Qian Wang, Robert E. Simpson, and Juejun Hu introduce the Special Section on Phase-Change Reconfigurable Photonics.

Antimony trisulfide (Sb2S3) is an Earth abundant material that is transparent to visible and near infrared light (N-IR). Switching the material between amorphous and crystalline states causes radical property changes that deem it useful for programming the response of visible and N-IR photonics devices. We have demonstrated how Sb2S3 can be used to program high resolution micro-displays, dielectric metasurfaces, hyperbolic metamaterials, waveguides, and all-optical neural networks. This presentation will discuss these demonstrations and the underlying physics responsible for the phase transition in Sb2S3.

The optical properties of phase-change materials (PCM) can be tuned to multiple levels by controlling the transition between their amorphous and crystalline phases. In multi-material PCM structures, the number of discrete reflectance levels can be increased according to the number of PCM layers. However, the effect of increasing number of layers on quenching and reversibility has not been thoroughly studied. In this work, the phase-change physics and thermal conditions required for reversible switching of single and multi-material PCM switches are discussed based on thermo-optical phase-change models and laser switching experiments. By using nanosecond laser pulses, 16 different reflectance levels in Ge2Sb2Te5 are demonstrated via amorphization. Furthermore, a multi-material switch based on Ge2Sb2Te5 and GeTe with four discrete reflectance levels is experimentally proven with a reversible multi-level response. The results and design principles presented herein will impact active photonics applications that rely on dynamic multi-level operation, such as optical computing, beam steering, and next-generation display technologies.

Biological systems evolve with minimum metabolic costs and use common components, and they represent guideposts toward a paradigm of manufacturing that is centered on minimum energy, local resources, and ecological integration. Here, a new method of metalworking that uses chitosan from the arthropod cuticle to aggregate colloidal suspensions of different metals into solid ultra-low-binder-content composites is demonstrated. These composites, which can contain more than 99.5% metal, simultaneously show bonding affinity for biological components and metallic characteristics, such as electrical conductivity. This approach stands in contrast with existing metalworking methods, taking place at ambient temperature and pressure, and being driven by water exchange. Furthermore, all the nonmetallic components involved are metabolized in large amounts in every ecosystem. Under these conditions, the composites' ability to be printed and cast into functional shapes with metallic characteristics is demonstrated. The affinity of chitometallic composites for other biological components also allows them to infuse metallic characteristics into other biomaterials. The findings and robust manufacturing examples go well beyond basic demonstrations and offer a generalizable new approach to metalworking. The potential for a paradigm shift toward biomaterials based on their unique characteristics and the principles of their manufacturing methods is highlighted.

A compact and responsive thermoelectric photodetector is introduced for the mid-infrared. By resonantly coupling mid-infrared light to a Sb2Te3-Bi2Te3 thermoelectric junction, a thermocouple is formed that is directly heated by narrow-band mid-infrared radiation. Near-perfect absorption is achieved at this hot junction through the resonantly enhanced coupling of light to free-electrons in the Bi2Te3 and Sb2Te3 materials. The fabricated devices operate at 3.6 mu m and demonstrate a responsivity of 10.2 V W-1, a specific detectivity of 4.6 x 10(6) cm Hz(1/2) W-1, and a bandwidth in the order of 1 kHz. The optimal detection wavelength can be spectrally tuned by changing the resonant cavity dimensions. This work shows a path toward miniaturized mid-infrared detectors and spectrometers with high sensitivity, responsivity, and bandwidth. Importantly, the device presented here is ideal for industrial production, which it is hoped will provide wider access to mid-infrared technologies for chemical sensing, medicine, and security.

Discovering new inorganic materials using solid-state synthesis in an accelerated fashion is difficult due their sluggish diffusion coefficients and long diffusion distances. Furthermore, high temperatures used in these reactions generally produce thermodynamically stable products, which provides limited control on the reaction and prevents access to functional metastable phases. Herein, we report the use of a millisecond laser annealing technique to regulate the crystallographic phases of germanium telluride films of varying thicknesses. After laser heating, we combine temperature-dependent synchrotron grazing incidence measurements and transmission electron microscopy to study the structural evolution of the post-laser-heated GeTe. On average, we observe that millisecond laser heating induced the transformation of amorphous GeTe samples up to a similar to 40% to 60% mixture of cubic beta-GeTe (Fm (3) over barm) and rhombohedral alpha-GeTe (R3m) for GeTe films (thicknesses between 100 nm and 2 mu m) deposited on thermally conducting substrates (such as Si), as opposed to phase-pure alpha-GeTe, which is obtained on low thermal conductivity substrates (quartz). Further, a room-temperature thermoelectric power factor of 6.10 mu V cm(-1) K-2 was measured for a laser-heated film on quartz. These findings suggest that conformal interfaces on substrates with high thermal conductivity facilitate accelerated rates of heat extraction at the sample-substrate interface to achieve phase control. We believe our strategy opens new avenues for the development of materials that are stabilized far from their equilibrium conditions.

Today, fitting bespoke hearing aids involves injecting silicone into patients’ ears to produce ear canal molds. These are subsequently 3D scanned to create digital ear canal impressions. However, before digital impressions can be used they require a substantial amount of effort in manual 3D editing. In this article, we present computational methods to pre-process ear canal impressions. The aim is to create automation tools to assist the hearing aid design, manufacturing and fitting processes as well as normalizing anatomical data to assist the study of the outer ear canal’s morphology. The methods include classifying the handedness of the impression into left and right ear types, orienting the geometries onto the same coordinate system sense, and removing extraneous artifacts introduced by the silicone mold. We investigate the use of convolutional neural networks for performing these semantic tasks and evaluate their accuracy using a dataset of 3000 ear canal impressions. The neural networks proved highly effective at performing these tasks with 95.8% adjusted accuracy in classification, 92.3% within 20° angular error in registration and 93.4% intersection over union in segmentation.

The ear canal is usually described as an S-shaped funnel. In attempting to classify ear-canal shapes obtained from point clouds digitized from molds of 300 ears, the problem of designing criteria for distinguishing and organizing the canal shapes arose. In this work, we extracted features inspired by the S-shape characteristic (critical point, maximum, minimum, twist, writhe, translation, rotation) and, through them, introduced 14 types of ear-canal shapes. This classification allowed comparison of ears within a type and of ears between different types. It expanded our range of descriptors of canal shapes and unlocked perspectives for applications.

Capping layers are essential for protecting phase change materials (PCMs) used in non-volatile photonics technologies. This work demonstrates how $(ZnS)_{0.8}-(SiO_2)_{0.2}$ caps radically influence the performance of $Sb_{2}S_{3}$ and Ag-doped $Sb_{2}S_{3}$ integrated photonic devices. We found that at least 30 nm of capping material is necessary to protect the material from Sulfur loss. However, adding this cap affects the crystallization temperatures of the two PCMs in different ways. The crystallization temperature of $Sb_{2}S_{3}$ and Ag-doped $Sb_{2}S_{3}$ increased and decreased respectively, which is attributed to interfacial energy differences. Capped and uncapped Ag-doped $Sb_{2}S_{3}$ microring resonator (MRR) devices were fabricated and measured to understand how the cap affects the device performance. Surprisingly, the resonant frequency of the MRR exhibited a larger red-shift upon crystallization for the capped PCMs. This effect was due to the cap increasing the modal overlap with the PCM layer. Caps can, therefore, be used to provide a greater optical phase shift per unit length, thus reducing the overall footprint of these programmable devices. Overall, we conclude that caps on PCMs are not just useful for stabilizing the PCM layer, but can also be used to tune the PCM crystallization temperature and reduce device footprint. Moreover, the capping layer can be exploited to enhance light-matter interactions with the PCM element.

A classical thermal source, such as an incandescent filament, radiates according to Planck's law. The feasibility of super-Planckian radiation has been investigated with sub-wavelength-sized sources in the last decade. In such sources, a crystal-dependent coupling of photons and optical phonons is possible at thermal energies corresponding to that at room temperature. This interaction can be used to tailor the far-field thermal emission in a coherent manner; however, understanding heat transfer during this process is still nascent. Here, we used a novel measurement platform to quantify thermal signals in a Ge2Sb2Te5/SiO2 nanoribbon structure. We were able to separate and quantify the radiated and conducted heat transfer mechanisms. The thermal emission from the Ge2Sb2Te5/SiO2 nanoribbons was enhanced by 3.5× compared to that of a bare SiO2 nanoribbon. Our model revealed that this enhancement was directly due to polaritonic heat transfer, which was possible due to the large and lossless dielectric permittivity of Ge2Sb2Te5 at mid-IR frequencies. This study directly probes the far-field emission with a thermal gradient stimulated by Joule heating in temperature ranges from 100 to 400 K, which bridges the gap between mid-IR optics and thermal engineering.

Chilling Effects occur when a restriction on speech deters lawful speech, because of people’s un-certainty about the risks of incurring costs related to the restriction. I propose that, contrary to an orthodox account of this phenomenon, individual-level deterrence of speech sometimes intensifies discourse, at the group level, rather than suppressing or subduing it. The deterrence of lawful speech may, somewhat counterintuitively, trigger a Heating Effect. This hypothesis offers us a promising (partial) explanation of the relentlessness of public debate on topics for which there is, simultaneously, evidence of people self-censoring, for fear of running afoul of speech restrictions. It also helps to identify and rectify two shortcomings in existing theoretical accounts of the Chilling Effect – in how they (i) explain the relation between individual- and group-level discursive phenomena, and (ii) characterize the distinctive objectionability of inadvertent speech deterrence.