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The solubilization of lipid membranes by Tween-20 is crucial for a number of biotechnological applications, but the mechanistic details remain elusive. Evidence from ensemble assays supports a solubilization model that encompasses surfactant association with the membrane and the release of mixed micelles to solution, but whether this process also involves intermediate transitions between regimes is unanswered. In search of mechanistic origins, increasing focus is placed on identifying Tween-20 interactions with controllable membrane mimetics. Here, we employed ultrasensitive biosensing approaches, including single-vesicle spectroscopy based on fluorescence and energy transfer from membrane-encapsulated molecules, to interrogate interactions between Tween-20 and submicrometer-sized vesicles below the optical diffraction limit. We discovered that Tween-20, even at concentrations below the critical micellar concentration, triggers stepwise and phase-dependent structural remodeling events, including permeabilization and swelling, in both freely diffusing and surface-tethered vesicles, highlighting the substantial impact the surfactant has on vesicle conformation and stability prior to lysis.

Semiconducting transition metal dichalcogenides (TMDs) have gained significant attention as a gain medium for nanolasers, owing to their unique ability to be easily placed and stacked on virtually any substrate. However, the atomically thin nature of the active material in existing TMD nanolasers presents a challenge, as their limited output power makes it difficult to distinguish between true laser operation and other "laser-like" phenomena. Here, we present comprehensive evidence of lasing from a CVD-grown tungsten disulphide (WS2) monolayer. The monolayer is placed on a dual-resonance dielectric metasurface with a rectangular lattice designed to enhance both absorption and emission; resulting in an ultralow threshold operation (threshold 2). We provide a thorough study of the laser performance at room temperature, paying special attention to directionality, output power, and spatial coherence. Notably, our lasers demonstrated a coherence length of over 30 μm, which is several times greater than what has been reported for 2D material lasers so far. Our realisation of a single-mode laser from a wafer-scale CVD-grown monolayer presents exciting opportunities for integration and the development of novel applications.

Transition metal dichalcogenides have emerged as promising materials for nanophotonic resonators because of their large refractive index, low absorption within a large portion of the visible spectrum, and compatibility with a wide range of substrates. Herein, we use these properties to fabricate WS2 double-pillar nanoantennas in a variety of geometries enabled by the anisotropy in the crystal structure. Using dark-field spectroscopy, we reveal multiple Mie resonances, to which we couple WSe2 monolayer photoluminescence and achieve Purcell enhancement and an increased fluorescence by factors up to 240 for dimer gaps of 150 nm. We introduce postfabrication atomic force microscope repositioning and rotation of dimer nanoantennas, achieving gaps as small as 10 ± 5 nm, which enables a host of potential applications, including strong Purcell enhancement of single-photon emitters and optical trapping, which we study in simulations. Our findings highlight the advantages of using transition metal dichalcogenides for nanophotonics by exploring applications enabled by their properties.

Vibrational spectroscopy is an important tool in chemical and biological analysis. A key issue when applying vibrational spectroscopy to dilute liquid samples is the inherently low sensitivity caused by short interaction lengths and small extinction coefficients, combined with low target molecule concentrations. Here, we introduce a novel type of surface-enhanced infrared absorption spectroscopy based on the resonance of a dielectric metasurface. We demonstrate that the method is suitable for probing vibrational bands of dilute analytes with a range of spectral linewidths. We observe that the absorption signal is enhanced by 1-2 orders of magnitude and show that this enhancement leads to a lower limit of detection compared to attenuated total reflection (ATR). Overall, the technique provides an important addition to the spectroscopist's toolkit especially for probing dilute samples.

Resonant photonic sensors are enjoying much attention based on the worldwide drive toward personalized healthcare diagnostics and the need to better monitor the environment. Recent developments exploiting novel concepts such as metasurfaces, bound states in the continuum, and topological sensing have added to the interest in this topic. The drive toward increasingly higher quality (Q)-factors, combined with the requirement for low costs, makes it critical to understand the impact of realistic limitations such as losses on photonic sensors. Traditionally, it is assumed that the reduction in the Q-factor sufficiently accounts for the presence of loss. Here, we highlight that this assumption is overly simplistic, and we show that losses have a stronger impact on the resonance amplitude than on the Q-factor. We note that the effect of the resonance amplitude has been largely ignored in the literature, and there is no physical model clearly describing the relationship between the limit of detection (LOD), Q-factor, and resonance amplitude. We have, therefore, developed a novel, ab initio analytical model, where we derive the complete figure of merit for resonant photonic sensors and determine their LOD. In addition to highlighting the importance of the optical losses and the resonance amplitude, we show that, counter-intuitively, optimization of the LOD is not achieved by maximization of the Q-factor but by counterbalancing the Q-factor and amplitude. We validate the model experimentally, put it into context, and show that it is essential for applying novel sensing concepts in realistic scenarios.

Resonant photonic sensors are enjoying much attention based on the worldwide drive toward personalized healthcare diagnostics and the need to better monitor the environment. Recent developments exploiting novel concepts such as metasurfaces, bound states in the continuum, and topological sensing have added to the interest in this topic. The drive toward increasingly higher quality (

We developed an analytical model to estimate the impacts of optical losses on the performance of photonic resonant sensors. We find that the resonance amplitude plays a significant, albeit underestimated, role on the performance.

We introduce a form-birefringent single layer metalens encoding two phase profiles on the same surface to correct spherical and off-axis aberrations allowing the switching from high resolution to wide field of view operation.

Near-field scanning optical microscopy is a powerful technique for imaging below the diffraction limit, which has been extensively used in biomedical imaging and nanophotonics. However, when the electromagnetic fields under measurement are strongly confined, they can be heavily perturbed by the presence of the near-field probe itself. Here, taking inspiration from scattering-cancellation invisibility cloaks, Huygens–Kerker scatterers, and cloaked sensors, we design and fabricate a cloaked near-field probe. We show that, by suitably nanostructuring the probe, its electric and magnetic polarizabilities can be controlled and balanced. As a result, probe-induced perturbations can be largely suppressed, effectively cloaking the near-field probe without preventing its ability to measure. We experimentally demonstrate the cloaking effect by comparing the interaction of conventional and nanostructured probes with a representative nanophotonic structure, namely, a 1D photonic-crystal cavity. Our results show that, by engineering the structure of the probe, one can systematically control its back action on the resonant fields of the sample and decrease the perturbation by > 70 % with most of our modified probes, and by up to 1 order of magnitude for the best probe, at probe-sample distances of 100 nm. Our work paves the way for non-invasive near-field optical microscopy of classical and quantum nanosystems.

The interest in high quality factor (high-Q) resonances in metasurfaces has been rekindled with the rise of the bound states in the continuum (BIC) paradigm, which describes resonances with apparently limitlessly high quality-factors (Q-factors). The application of BICs in realistic systems requires the consideration of the angular tolerance of resonances, however, which is an issue that has not yet been addressed. Here, we develop an ab-initio model, based on temporal coupled mode theory, to describe the angular tolerance of distributed resonances in metasurfaces that support both BICs and guided mode resonances (GMRs). We then discuss the idea of a metasurface with a perturbed unit cell, similar to a supercell, as an alternative approach for achieving high-Q resonances and we use the model to compare the two. We find that, while sharing the high-Q advantage of BIC resonances, perturbed structures feature higher angular tolerance due to band planarization. This observation suggests that such structures offer a route toward high-Q resonances that are more suitable for applications.

The correction of multiple aberrations in an optical system requires different optical elements, which increases its cost and complexity. Metasurfaces hold great promise to providing new functionality for miniaturized and low-cost optical systems. A key advantage over their bulk counterparts is the metasurface's ability to respond to the polarization of light, which adds a new degree of freedom to the optical design. Here, we show that polarization control enables a form-birefringent metalens to correct for both spherical and off-axis aberrations using a single element only, which is not possible with bulk optics. The metalens encodes two phase profiles onto the same surface, thus allowing switching from high resolution to wide field of view operation. Such ability to obtain both high resolution and wide field of view in a single layer is an important step towards integration of miniaturized optical systems, which may find many applications, e.g., in microscopy and endoscopy.