Mitigating the interference effects induced by optical cavities in superstrate thin-film silicon multi-junction solar cells

Multiple reflection: A Route to enhanced sensitivity in beam-deflection optical ultrasound sensing.

Hexagonal boron nitride (hBN) is gaining increasing attention in the field of biomolecule characterization due to its compatibility with single-molecule fluorescence imaging and real-time tracking. Embedding fluorescent molecules within hBN layers offers potential for molecular-resolution sensing devices, since these probes are highly sensitive to their surroundings. Yet, the effect of hBN surfaces on the fluorophore properties remains largely unexplored. Here, we monitor the photophysical properties of ATTO647N-ssDNA on hBN surfaces and elucidate the effects of the environment and substrate. We demonstrate that the presence of hBN increases the photobleaching time and changes intermittency dynamics. By combining van der Waals stacking and FDTD simulations, we subsequently engineer hBN optical cavities to modulate the emission from individual molecules, showing that the brightness can be tuned by a factor of 4. Our findings shed light on light-matter interactions in hybrid nanostructures, which can enable single-molecule imaging and biosensing at high spatial and temporal resolution.

We clarified the physical mechanism of superconducting strip single photon detectors(SSPDs) with optical cavities by using transmission line and impedance models. By introducing the transmission line model, we derived the analytical formulae for the absorptance of SSPDs with optical cavities. We compared the absorptance obtained from the analytical formulae for SSPDs with single-side, double-side, and dielectric multi-layer optical cavities against the results of numerical simulations. The comparison showed that the results were nearly identical. By introducing the impedance model, it was clearly shown that the SSPDs with optical cavities achieved the maximum absorptance when their input impedance of the SSPDs with optical cavities matched the impedance of the input medium. The design concepts proposed in this study are applicable to other superconducting detectors, such as microwave kinetic inductance detectors and transition-edge sensors.

Coupling excitons with quantized radiation has been shown to enable coherent ballistic transport at room temperature inside optical cavities. Previous theoretical works employ a simple description of the material, depicting it as a one-dimensional single-layer placed in the middle of an optical cavity, thereby ignoring the spatial variation of the radiation field. In contrast, in most experiments, the optical cavity is filled with organic molecules or multiple layers of two-dimensional materials. Here, we develop an efficient mixed-quantum-classical approach, introducing a bright layer description, that enables the simulation of exciton-polariton quantum dynamics in all three dimensions. Our simulations reveal that, for the same Rabi splitting, a multilayered material extends the quantum coherence lifetime and enhances transport compared to a single-layer material. We find that this enhanced coherence can be traced to a synchronization of phonon fluctuations over multiple layers, wherein the collective light-matter coupling in a multilayered material effectively suppresses the phonon-induced dynamical disorder.

Harnessing strong light-matter interactions to control chemical reactions in confined electromagnetic fields offers a promising route toward deepening our understanding of chemical dynamics at the collective quantum-mechanical level, with potential implications for future chemical synthesis paradigms. Achieving this goal, however, requires an in-depth mechanistic understanding of underlying dynamical processes. As a step in this direction, we present a systematic and numerically exact quantum dynamical study of cooperative reaction dynamics inside an optical microcavity. Using a hierarchy of model systems with increasing complexity, we elucidate how cavity-modified reactivity emerges from-and is highly sensitive to-subtle structural and environmental variations. Our models consist of optically dark reactive molecules, each represented by a symmetric double well potential, coupled to infrared-active non-reactive intramolecular or solvent vibrational modes, as well as their respective dissipative environments. Our results demonstrate that cavity-induced rate modifications arise from a delicate interplay among mode hybridization in strong-coupling regimes, the dynamical balance of all participating energy exchange processes, and quantum interference between multiple fluctuation-dissipation-mediated reaction pathways enabled by collective cavity coupling. By continuously tuning a single system parameter or introducing molecular collectivity, we observe qualitatively distinct rate modification profiles as functions of the cavity frequency, including resonant rate enhancement, resonant rate suppression, hybridization-induced peak splitting, and, notably, asymmetric Fano-type line shapes in which enhancement peaks and suppression dips coexist within a narrow resonance window, highlighting the important role of quantum interference in cavity-modified chemical reactivity.

Large overhang milling cutters face challenges, including poor cutting stability and surface quality when machining deep-cavity parts in aerospace and other industries. The combined interactions between overhang and process parameters significantly influence machining performance and the tool wear mechanism. In this study, the coupled effects of tool overhang length and feed per tooth on milling force, surface topography, chip morphology, and tool wear mechanism were systematically investigated under typical large overhang conditions. The tool stiffness decreased with increasing overhangs; the feed force decreased by approximately 32.4%~49.48%; and the chip morphology changed from continuous bands to fractures. The feed force increased by approximately 25.11%~67.34% with increasing the feed per tooth, resulting in reduced surface quality and accelerated tool wear. The novelty of this work lies in quantitatively revealing the coupling mechanism between overhang length and feed rate in large overhang milling, providing a theoretical basis for process optimization. The findings are directly applicable to the optimization of machining parameters for deep-cavity components such as aero-engine casings and optical mold cavities, where tool overhang is a critical factor affecting productivity and surface integrity. This study provides a theoretical foundation and experimental reference for optimizing process parameters when milling titanium alloy with long-overhang milling cutters.

We demonstrate how the transport properties of molecular polaritons in optical cavities can be extracted from a microscopic modeling of pump-probe spectroscopy. Our approach combines a mean-field treatment of the light-matter Hamiltonian with a perturbative expansion of both light and matter components, along with spatial coarse-graining. This approach extends semiclassical cavity spectroscopy to multimode light-matter interactions, providing full access to spatially resolved transient spectra. By simulating a microscopy experiment with counter-propagating pump and probe pulses, we compute the differential transmission and show how molecular dephasing and persistent dark exciton populations drive subgroup velocity transport of the root-mean-square displacement. We analyze transport across the polariton dispersion, showing how velocity renormalization correlates with excitonic weight, consistent with experimental observations, and further its dependence on the rate of molecular dephasing, exciton hopping, and exciton-exciton annihilation. Our results highlight the need to consider measured spectroscopic observables when characterizing transport in polaritonic systems.

• New balanced detection architecture for photothermal gas sensing, featuring: a reduced system complexity by utilizing a single 1-mm air-spaced Fabry-Perot interferometer, an improved signal-to-noise ratio by a factor of 18, a gas cell having a sample probe value of only 1.8 mL. • Robust sensing scheme: Refractive index changes which are induced by a mid-infrared excitation laser are monitored by a near-infrared probe laser intersecting the excitation beam in transverse configuration. • CO gas sensing achieving a minimum detection limit of 2 ppbv, which corresponds to a NNEA of 7.4 x 10 −9 cm −1 W Hz −1/2 . • Investigation of the influence of a varying water vapor concentration on the molecular relaxation process of CO at a modulation frequency of ∼ 300 Hz. This work reports on the implementation of an alternative balanced-detection scheme to the ICAPS sensing method employing solely a single cavity. The new concept was realized by simultaneous detection of the interferometer’s reflectance and transmission. The use of only one cavity significantly reduces the system’s complexity in a balanced configuration by simplifying the detection architecture. Additionally, it increases the sensor’s sensitivity by noise cancellation and an improvement of the detectable signal up to a factor of 2. The set-up employed an optical cavity with a mirror spacing of 1 mm. A mid-infrared laser served as excitation source to induce refractive index changes in the sample, and a near-infrared laser served as probe source to monitor the photo-induced variations. The sensor’s metrological figures of merit were investigated by detection of CO. Moreover, the influence of varying water vapor concentration on the molecular relaxation of CO and thus the monitored photothermal signal employing a modulation frequency of ∼ 300 Hz was investigated. For the targeted absorption band centered at 2179.77 cm −1 a 1σ minimum detection limit of 2 ppbv was achieved using an integration time of 1 s. This result corresponds to a normalized noise equivalent absorption of 7.4 × 10 −9 cm −1 W Hz −1/2 .

We explore laser-induced dewetting of thin gold films deposited on different underlayers consisting of optical cavities of gold and silica. Our observations indicate that the morphology and optical response of laser-exposed regions are sensitive to the optical environment in vicinity of the dewetting layer.

Abstract Optical cavities that provide radiative enhancement and efficient photon collection across a broad spectrum are essential for classical and quantum photonic applications. Many platforms to date have been restricted to the near-infrared (NIR) to telecom spectrum with limited cavity enhancement in the ultraviolet (UV) to NIR wavelength range. Here, we develop a silicon nitride (Si3N4) bullseye cavity platform optimized for maximal optical enhancement at UV and NIR wavelengths. By utilizing a distributed Bragg reflector designed to satisfy the first- and second-order Bragg conditions, the cavity contains guided modes at NIR and UV wavelengths, respectively. We employ finite-difference time-domain simulations to explore the full device parameter space in which our structure can be optimized for off-chip collection efficiencies exceeding 90% or Purcell factors greater than 50. Additionally, we use these two metrics to perform a global optimization where we can achieve simulated optical enhancements greater than 30 for resonances around 425 nm and 835 nm, the highest values reported to date of any optical cavity designs operating below the telecom O-band. We provide an experimental demonstration that includes a CMOS-compatible
fabrication process and reflectometry measurements to characterize the cavity resonances. This platform provides a foundation for strong cavity enhancement and efficient off-chip extraction of a wide range of single-photon emitters spanning UV and NIR wavelengths.

Abstract Quantum synchronization and synchronization transmission among three mechanical oscillators are investigated in a coupled multimode optomechanical system. The system consists of three subsystems, each comprising an optical cavity and a mechanical oscillator. The tripartite synchronization among the oscillators can be visualized through the joint limit-cycle trajectories and Wigner functions. Quantum synchronization and anti-synchronization of two oscillators can be achieved simultaneously in the coupled multimode optomechanical system. For three coupled optomechanical systems, parameter ranges for achieving synchronization are presented. Moreover, the synchronization transmission among mechanical oscillators is also investigated by manipulating the driving laser. In addition, the circular optomechanical configuration is also identified as an effective platform for studying quantum synchronization. The differences between the two optomechanical system configurations are analyzed and compared. These results provide a promising platform for studying quantum correlations and quantum information processing with mechanical oscillators based on controllable multimode optomechanical systems.

A micro-cavity based on phase-change material is a very important strategy for the realization of tunable absorption and conversion of terahertz waves. In this work, a tunable terahertz metamaterial absorber based on the phase-change material germanium–antimony–tellurium (GST) is demonstrated. The device features a metal–insulator–metal triple-layer structure, where the dynamic switching of absorption characteristics is achieved via thermally controlled GST phase transition. In the amorphous state, the absorber exhibits a single absorption peak at 7.7 THz. Upon crystallization, the absorption switches to dual peaks at 5.1 THz and 8.3 THz, achieving near-perfect absorption in both states. Full-wave electromagnetic simulations and theoretical analysis based on a multiple-reflection interference model indicate that this performance tuning originates from the GST-phase-transition-induced change in the equivalent optical cavity length. This corresponds to a switch between two resonant modes: coupled inner–outer ring resonance and independent outer ring resonance. These results provide a foundation for developing dynamically tunable terahertz devices with promising applications in terahertz communications, imaging, and sensing.

The Gravity Recovery and Climate Experiment (GRACE) missions monitor variations in the Earth’s gravity field, primarily due to water transport, by measuring the change in the distance between two spacecraft. The next generation of GRACE-like missions is expected to rely on interspacecraft laser interferometry to recover these geodesy signals, necessitating the development of a technique to provide long-term laser frequency knowledge. A development electronics unit has been designed and manufactured to provide long-term absolute laser frequency knowledge for the GRACE-Continuity laser ranging system. This paper presents the first measurement of cavity ageing over 2.5 years using this technique and reports on the performance with sub-MHz errors in a GRACE-like optical cavity, sufficient for next-generation GRACE missions. Limitations caused by spurious etalons in the optical system are discussed.

In this paper, we investigate three schemes for implementing Controlled-Z (CZ) gates between individual ytterbium (Yb) rare-earth ions doped into yttrium orthovanadate (YVO 4 or YVO). Specifically, we investigate the CZ gates based on magnetic dipolar interactions between Yb ions, photon scattering off a cavity, and a photon interference-based protocol, with and without an optical cavity. We introduce a theoretical framework for precise computations of state and gate infidelities, accounting for noise effects. We then compute the state fidelity for each scheme to evaluate the feasibility of their experimental implementation. Based on these results, we compare the performance of the two-qubit gate schemes and discuss their respective advantages and disadvantages. We conclude that the probabilistic photon interference-based scheme offers the best fidelity scaling with cooperativity and is superior with the current technology of Yb values, while photon scattering is nearly deterministic but slower with less favourable fidelity scaling as a function of cooperativity. The cavityless magnetic dipolar scheme provides a fast, deterministic gate with decent fidelities if close ion localization can be realized. While focusing on 171 Yb 3 + :YVO system as a case study, the theoretical tools and approaches developed in this work are broadly applicable to other spin qubit systems.

Molecular polaritons, formed by coupling molecular excitons with cavity photons, offer a promising platform for exploring quantum phenomena. A key challenge is understanding how these hybrid states maintain coherence in the presence of environmental vibrations. Here, we show theoretically that collective coupling of many molecular excitons in a cavity can protect polariton coherence from phonon-induced decoherence. Under realistic conditions, the coherence time can extend up to 200 fs at room temperature, compared with 15 fs for typical molecular systems. Simulations of two-dimensional electronic spectra reveal prolonged oscillations between upper and lower polariton states, and reduced vibrational coupling as indicated by changes in the nodal line slope of the lower polariton peak. These findings provide guidance for experimental efforts to realize long-lived polaritons, such as coupling CdSe nanoplatelets to optical cavities.

In this work, we present a proof-of-concept investigation of non-equilibrium chemical reaction dynamics at a molecule-electrode interface, driven out of equilibrium by an applied voltage bias and mediated by a confined, enhanced vacuum electromagnetic field inside an optical cavity. The coupled electron-vibration-photon system, together with the electrodes and a dissipative environment, is described within an open quantum system framework and solved using a numerically exact quantum dynamical approach. The reaction coordinate is modeled using a Morse potential, enabling explicit treatment of molecular anharmonicity and bond-breaking behavior. By varying the cavity frequency across the infrared regime to cover typical nuclear vibrational energies, we observe multiple resonant rate suppression features that emerge whenever the cavity mode is brought into resonance with a dipole-allowed vibrational transition along the anharmonic ladder up to the dissociation threshold. These findings open the door to extending polaritonic chemistry into genuinely non-equilibrium scenarios relevant to molecule-electrode interfaces. Moreover, building on these results, we further propose a multi-mode vibrational strong coupling strategy in which several cavity modes are individually matched to distinct vibrational transitions. This engineered multi-resonant cavity induces a stepwise vibrational ladder descending process that efficiently drains vibrational excited energy. The resulting cavity-assisted cooling suggests a potential route toward mitigating voltage-induced bond rupture and the long-standing instability issues of molecular junctions operating under high bias.

The space-based gravitational wave detector DECIGO is designed to observe primordial gravitational waves with 1000km Fabry-Perot cavities. Its sensitivity is limited by quantum noise, and although squeezing can suppress it, its effectiveness is reduced by diffraction-related loss, which leads to the injection of vacuum fields into the interferometer. This paper presents a rigorous treatment of quantum field propagation in the presence of diffraction and higher-order mode losses, deriving input-output relations and modeling their impact via an optomechanical block diagram. The analysis shows that diffraction-induced vacuum fields slightly increase radiation pressure noise, while shot noise remains unaffected. Nevertheless, cavity detuning with homodyne detection yields a dip in the noise spectrum. By accurately capturing these effects, this framework enables a detailed study of sensitivity improvements made by either just detuning the main cavity while implementing homodyne detection, or by combining this with optical-spring quantum locking using auxiliary cavities, laying a firm foundation for enhancing DECIGO's capability to detect primordial gravitational waves.

A midinfrared cavity ring-down (CRD) spectrometer was developed employing a 4.44 μm quantum cascade laser (QCL) for the sensitive detection of CO2 isotopologues, including 12C16O2 (44), 13C16O2 (45), 12C16O18O (46), and 13C16O18O (47). Instead of using an acousto-optic modulator (AOM), rapid QCL current switching was employed to initiate ring-down events, effectively reducing optical losses typically introduced by the AOM and simplifying the system design. The spectrometer incorporated a high-finesse (∼50,000) optical cavity, achieving a minimum detectable absorption coefficient (MDAC) of 2.2 × 10-11 cm-1 with 14.5 s average time. A continuous frequency sweep within a 0.2 cm-1 spectral window enabled simultaneous analysis of the four target isotopologues. Allan deviation analysis over a 6 h continuous measurement revealed optimal detection precisions of 0.45 ‰ for δ45/44, 0.28 ‰ for δ47/46, 0.47 ‰ for δ46/44, 0.35 ‰ for δ47/45, and 0.3 ‰ for δ47/44 at 65 min averaging time, demonstrating excellent long-term stability and high detection precisions. Coupled with a dedicated gas handling system, the instrument enabled analysis of gas volumes as small as ∼10 mL. The CRDS system further demonstrated robust performance in real-sample analyses, exhibiting strong linear agreement with isotope ratio mass spectrometry (IRMS). High-precision determinations of the δ13C, δ18O, and δ 47/44 isotope ratios were successfully achieved.

Coupling molecules to the quantized radiation field inside an optical cavity creates a set of new photon-matter hybrid states, so-called polaritons. Recent experiments have demonstrated that molecular polaritons can lead to modifications of excited-state dynamics and spectroscopy, photochemistry, and ground-state chemical reactivities. We review the fundamental theory of molecular polaritons under collective light-matter coupling, where many molecules are simultaneously coupled to the cavity mode. Our discussion is based on model systems that effectively capture the essential physics of experiments, allowing one to obtain analytic theories and valuable insights into the microscopic mechanisms in polariton dynamics and spectroscopy, photochemistry, and vibrational strong coupling-modified chemistry.