This computational study investigates the optical properties of a sixth-order Fibonacci quasi-periodic photonic crystal cavity designed for the infiltration of near-infrared colloidal quantum dots (QDs, e.g., InAs/ZnSe or PbS) and fully compatible with plasma-enhanced chemical vapor deposition (PECVD) using porous silicon layers. Using the transfer matrix method (TMM), we simulate transmission (T), reflection, absorption, electric field distributions and Purcell factors (F) for both TE and TM polarizations, incorporating the wavelength-dependent absorption of porous silicon. A multi-objective figure-of-merit is defined to simultaneously maximize transmission (T>95% at 800 nm) and the one-dimensional Purcell factor. The optimized structure (PH=0416) yields a quality factor Q≈4300, a 1D Purcell factor F1D≈3,6 and a realistic 3D Purcell enhancement estimated between 4 and 8 (under lateral confinement assumptions). This conservative estimate, derived via the effective index method to account for 3D effects, aligns with the detailed discussion within the article and is lower than the ideal upper bound of the 1D model. The integrated emission enhancement is approximately 3.0-fold. Monte Carlo simulations demonstrate remarkable robustness to fabrication tolerances (±10 nm thickness variations result in a <5% reduction in transmission), highlighting the structure’s scalability for PECVD-based processing. Comparison with periodic Bragg structures reveals superior angular stability and disorder tolerance in the Fibonacci design, positioning it as a promising platform for robust QD-based light sources and integrated refractive index sensors.

Nitrogen-vacancy (NV) color centers in diamond serve as promising atomic spin systems for measurement applications requiring high accuracy and sensitivity. A key challenge in NV-based quantum sensing is minimizing spin readout noise to approach the standard quantum limit (SQL). Based on a six-level model, this work analyze the dependence of NV-based quantum sensing performance, including spin state readout noise and signal-to-noise ratio (SNR), on controllable parameters such as the Purcell factor and excitation laser pulse characteristics. This study demonstrates that a shorter excitation pulse duration results in a higher saturation value of ground-state spin polarization, while the total time required for the polarization process remains constant. Additionally, the spin readout noise does not improve monotonically with decreasing excitation pulse duration; instead, it initially decreases and subsequently increases as the pulse duration varies. The spin readout noise reaches its optimal level when the pulse duration is 3 ns. Furthermore, no positive correlation exists between the signal-to-noise ratio (SNR) and the Purcell factor, and there is also an optimal value for SNR. When the pulse duration ranges from 1 ns to 40 ns, the variation in SNR is relatively insignificant. This research offers a novel perspective for enhancing the performance of quantum sensing based on diamond defects, such as nitrogen-vacancy (NV) centers.

We present the design, fabrication, and characterization of tunable waveguide-coupled silicon bowtie cavities with strong spatial electromagnetic field confinement. We use nanoelectromechanical in-plane actuation for the tuning, as this combines cryocompatibility with ultralow power consumption. Our device leverages a mode volume below 0.2 cubic wavelengths in the material to reach theoretical Purcell factors above 6,500 and waveguide-coupling efficiency above 30% across the full experimentally measured spectral-tuning range of 11 nm. Our spectral measurements demonstrate reversible tuning of bowtie cavities, and we directly show the in-plane actuation using in situ characterization in a scanning electron microscope. Our results constitute the first demonstration of a low-loss tunable bowtie nanocavity with strong light confinement. This solves a key issue for experiments on strong light-matter interactions for cavity quantum electrodynamics and scalable photonic quantum technologies.

An efficient interface between a spin qubit and single photons is a key enabling system for quantum science and technology. We report on a coherently controlled diamond nitrogen-vacancy center electron spin qubit that is optically interfaced with an open microcavity. Through Purcell enhancement and an asymmetric cavity design, we achieve efficient collection of resonant photons, while on-chip microwave lines allow for spin qubit control at a 10 MHz Rabi frequency. With the microcavity tuned to resonance with the nitrogen-vacancy center's optical transition, we use excited state lifetime measurements to determine a Purcell factor of 7.3±1.6. Upon pulsed resonant excitation, we find a coherent photon detection probability of 0.5% per pulse. Although this result is limited by the finite excitation probability, it already presents an order of magnitude improvement over the solid immersion lens devices used in previous quantum network demonstrations. Furthermore, we use resonant optical pulses to initialize and read out the electron spin. By combining the efficient interface with spin qubit control, we generate two-qubit and three-qubit spin-photon states and measure heralded Z-basis correlations between the photonic time-bin qubits and the spin qubit.

ABSTRACT We propose a system for channeling plasmon‐enhanced polarized single photons into optical nanowire‐guided modes. We show that the spontaneous emission properties of quantum emitters can be strongly enhanced in the presence of a gold nanorod dimer, leading to the emission of highly polarized and bright single photons. We numerically calculate the Purcell factor as high as ∼ 19150 and a radiative quantum efficiency of ∼ 0.8. This yields a coupling efficiency of ∼ 13% into the guided modes of the optical nanowire with an enhancement factor of ∼ 1990 and a high degree of polarization of > 99% for fiber‐coupled single photons. We show that the gold nanorod dimer system can yield an order of magnitude enhancement of the spontaneous emission characteristics as compared to a single gold nanorod. This proposed hybrid quantum system can be in line with fiber networks and may open new avenues for quantum information applications.

Abstract Both axion and dark photon dark matter are among the most promising candidates of dark matter. What we know with some confidence is that they exhibit a small velocity distribution δv ≲ v ∼ 10 −3 c . In addition, their mass is small, resulting in a long de Broglie wavelength and a high particle number density. Their phase space distribution contains many uncertainties, so they could give rise to either a coherent or noncoherent wave on the laboratory scale. In this paper, we demonstrated that a resonant cavity can enhance noncoherent axion-to-photon or dark photon-to-photon transitions, and the resulting power is the same as in the coherence case. The classical picture explanation is that a cavity can resonant with multiple different sources simultaneously. This aligns with the quantum perspective, where the cavity boosts dark matter particles transitioning into photons similarly to the Purcell effect. This effect increases the density of states near resonance, regardless of the coherence nature of dark matter. Certainly, the induced microwave signals in a cavity are also non-coherent, and in such case, a single-photon readout may be required.

Nanolasers based on colloidal quantum dots (CQDs), while transformative in the visible spectrum, face critical roadblocks in the near-infrared (NIR) regime due to material instability under ambient conditions and ultrafast Auger recombination in large NIR CQDs. Here, these limitations are addressed through zinc-doped PbS CQDs that suppress nonradiative decay, integrated with compact high-Q silicon nanobeam cavities to leverage the Purcell effect for efficiently guiding spontaneous emission into laser modes, thereby significantly reducing the threshold power. This work demonstrates a monolithic CQD-integrated silicon photonic platform that achieves NIR lasing under pulsed optical pumping, featuring a record narrow linewidth of 0.29 nm (0.15 meV) at 1579.20 nm and an ultralow threshold of 127 µJcm-2. Notably, under continuous-wave (CW) pumping, the device exhibits cavity-filtered spontaneous emission with a sub-nanometer linewidth across the 1350-1600 nm spectrum. This emission showcases <6% peak power decay over 15 h at 300 K, robust performance up to 360 K, and negligible degradation after 250 days of ambient storage. By monolithically integrating solution-processed CQDs with CMOS-compatible silicon photonics, this platform establishes a reliable, scalable, and low-cost route toward multiwavelength on-chip nanolaser arrays in the NIR regime, unlocking transformative potential for compact photonic technologies in imaging, sensing, and communications.

Cavity interactions are crucial to several high-efficiency photonic devices, such as resonant cavity light-emitting diodes and vertical cavity surface emitting lasers. In particular, optical microcavities are conventionally used to achieve sufficiently bright single photon sources to be utilized in modern photonic quantum technologies. We present a study of the cavity-funneling effect of the optical emission from an ensemble of CsPbBr3 PNCs embedded in an open optical plano–convex microcavity at room temperature with two different radii of curvature of the convex mirror. A generalized Purcell factor of F*=30 is found. The increase in Purcell factor as a function of the cavity radius of curvature (RoC) is compared to the decrease in the effective mode volume with RoC, obtained via a 3D simulation of the two cavity configurations with radii of curvature of 12 and 99 μm. The effective mode volume reduction going from the 99 μm to the 12 μm RoC configuration is identified as the most plausible origin for the greater optical emission enhancement observed in the smaller RoC cavity. Other secondary factors such as an increased coupling to single transverse modes or the increase in the Q-factor are discussed and placed in context, as the basis for future designs of more effective cavity systems for perovskite nanocrystals at room temperature.

Achieving highly circularly polarized luminescence has long been a primary objective in the design, synthesis, and application of chiral luminophores. However, a persistent challenge arises from the trade-off between large luminescence dissymmetry factors (glum) and high luminescence efficiency, resulting in typically mediocre brightness for most chiral emitters and limiting their practical use. While various strategies have been proposed to enhance glum, these values rarely exceed 1.0 and often come at the cost of diminished luminescence intensity. In this article, an extreme nanophotonic approach is employed using thorned helicoid-on-mirror (THoM) constructs to generate intense local optical chirality, which is then coupled to achiral dyes with high quantum yields. An efficient coupling is revealed between the strong superchiral near field and the dyes within the chiral nanocavity, which not only produces glum values exceeding 1.0 but also amplifies both excitation and emission processes via a pronounced chiral Purcell effect, leading to ultrahigh brightness in circularly polarized luminescence. By adjusting the dye assembly and its corresponding emission peaks, tunable chiral emission is achieved, demonstrating significant potential for advanced chiral displays and information encryption. Furthermore, this high-performance chiral emitting system holds promise for on-chip integration of chiral lasers and chiral single-photon sources.

Abstract The high‐dimensional Toffoli gate functions in a broader Hilbert space, which empowers it to convey and handle greater amounts of information through parallel quantum pathways. In this study, a scheme of 3‐qudit ‐D Toffoli gate in the QD cavity‐coupling system with high fidelity is proposed. By modulating Purcell factor, the balanced condition is obtained so that the error induced by whether there is interaction between the QDs and cavities or not can be neglected. The scheme features a module circuit design, which not only ensures higher construction feasibility but also helps save resources. Meanwhile, it possesses technical scalability, enabling effective promotion to the application scenarios of n‐qudit systems, which reduces the steps required to manipulate quantum states and makes it simpler to construct quantum computing circuits.

Abstract Developing spectrally precise, compact electroluminescent (EL) devices is critical for emerging photonic technologies, including advanced displays and integrated photonic systems. Although recent advances in emitter materials have enabled narrowband emission with full width at half maximum (FWHM) values as low as 25 nm, their practical applications are hindered by stability issues, fabrication complexity, and limited environmental compatibility. Optical microcavities improve spectral precision through high‐quality factors but require complex reflector structures and simultaneous optical and electrical optimization. Here, a universal strategy is presented to achieve spectrally precise emission from broadband organic light‐emitting diodes (OLEDs) by enhancing the Purcell effect through dual‐microcavity resonances. A secondary cavity atop the OLED separates optical and electrical design while generating dual‐microcavity resonances. Coupling between excitons and dual‐microcavity enhances the Purcell effect, leading to an increased spontaneous emission rate. Spectrally tunable, ultrapure green emission (FWHM = 21 nm) is demonstrated from phosphorescent OLEDs (intrinsic FWHM = 60 nm), achieving ≈65% spectral narrowing. The devices also exhibit a high luminance of 1.241 × 105 cd m−2, strong directionality, and suppressed efficiency roll‐off. Our approach is compatible with state‐of‐the‐art emitters, polaritons, and photonic architecture, offering a promising route toward advanced photonic systems requiring monochromatic emission from compact EL devices.

This work studies the Purcell effect of two quasiperiodic multilayers of gold and titanium dioxide following the Thue–Morse and Fibonacci sequence, respectively. We systematically investigated the impacts of polarization direction, dipole height, and wavelength on the Purcell factor. Additionally, we compared the normalized field distribution profiles across all multilayer structures. Concurrently, under varying polarizations, we computed the radiative part of the Purcell factor, photoluminescence at the reflection and transmission side of multilayers, respectively. Our findings indicate that under near-field excitation conditions, the Purcell factor is predominantly governed by its non-radiative component rather than the radiative one. We attribute the observed discrepancies in the Purcell factor to variations in the intensity and spatial distribution of non-radiative losses within the metallic components of the multilayers. This mechanism provides a robust physical foundation for exploring and extending the applications of photonic quasicrystals in the modulation of nanoscale light–matter interactions. Furthermore, we examined cavities constructed from symmetric multilayers. Under z-polarization and long-wavelength conditions, the cavity effect was observed to enhance the radiative part of the Purcell factor, thereby further boosting spontaneous emission efficiency. This work offers novel insights into the design of semiconductor devices with improved quantum emission efficiency and photoluminescence.

Room-temperature circularly polarized single-photon sources are crucial for quantum information and photonic technologies. Here we integrated europium (Eu3+)-doped organic complexes with chiral plasmonic nanocavities using helicoid-on-mirror (HoM) architecture, achieving giant circularly polarized emission with quantum yield of 40% and dissymmetry factor (glum) of 0.40 ± 0.02. The HoM's superchiral hotspot enhances chiral emission through the Purcell effect. Nonlinear dynamics confirms the transition from spontaneous to stimulated chiral photon generation with reduced threshold power. Time-resolved fluorescence spectroscopy shows enhanced radiative rates (0.7 μs vs 360 μs bulk), indicating efficient plasmon-exciton coupling. Single-photon emission with circular polarization characteristics is demonstrated by photon antibunching (g(2) = 0.30 ± 0.05) at room temperature when the pumping power is below 20 μW. This integration of lanthanide photophysics with chiral plasmonics provides scalable pathways for room-temperature quantum chiral photonics, with applications in quantum information encoding, chiral sensing, and circularly polarized organic light-emitting diodes.

Resonance Energy Transfer and Purcell Effect in a Cu₂O/Au Hybrid Optical Antenna

Circular Bragg grating resonators have gained a lot of attention in various material platforms due to their high Purcell factors over large bandwidth. Although the bandwidth is on the order of several nanometers, the best performance is given when perfectly matching the resonator's frequency with the frequency of the embedded emitter. The device resonance spectrum depends on many parameters, such that fabrication often renders devices with detuning to the intended frequency. Here, we show a method to tune the resonator mode in post-fabrication via atomic layer deposition. Atomic layer deposition of a dielectric layer (Al2O3) is used to red-shift the optical resonance. While the presented technique is universal for circular Bragg grating resonators within a wide class of material systems, we choose the quaternary semiconductor In0.53Al0.23Ga0.24As and incorporate InAs quantum dots as active material to validate the technique. We show a tuning of the resonator mode of up to (11.3±0.1) nm with (36±1) nm of Al2O3 at about 1460 nm emission wavelength, which is more than half of the experimental linewidth of the mode itself.

In this work, we demonstrate a substantial enhancement in photoluminescence from semiconducting single-walled carbon nanotubes through integration with a small-mode-volume silicon photonic crystal nanobeam cavity. Our design approach enables precise control of the cavity resonance over a wavelength range exceeding 30 nm, effectively covering the emission spectrum of semiconducting single-walled carbon nanotubes while maintaining stable optical performance. The fabricated nanobeam cavities, embedded with polymer-sorted semiconducting single-walled carbon nanotubes, exhibit low modal volumes of V = 0.07(λ/n)3, facilitating strong light-matter interaction characterized by high coupling efficiency and a Purcell factor on the order of 10000(λ/n)3 at a wavelength of 1570 nm. This hybrid integration exploits the robust light-matter interaction properties of the cavity, leading to a pronounced increase in emission intensity from the carbon nanotubes.

Magnetic anapole states associated with the destructive interference between magnetic dipole and magnetic toroidal moments result in suppressed scattering accompanied by strongly enhanced near fields. Here, we demonstrate the existence of such modes in the gap of a gold oblate nano-ellipsoid on gold mirror (ONEOM) structures and observe a pronounced Purcell factor enhancement for magnetic dipole radiation upon introducing magnetic dipoles into the gap. We systematically investigate the dependence of the magnetic radiation Purcell factor on gap size and structural parameters. Notably, a 230-fold Purcell factor enhancement is achieved for the ONEOM configuration. This result highlights the potential of ONEOM structures in applications requiring efficient magnetic dipole emission, including nonlinear frequency conversion, plasmonic sensing, and single-photon sources.

Epsilon-near-zero (ENZ) photonics offers a compellingplatformfor integrated photonic systems, enabling a range of novel and extraordinaryfunctionalities. However, the practical deployment of ENZ-based devicesis constrained by high material losses and severe impedance mismatch,which are detrimental to applications requiring coherent light manipulationand efficient light-matter interaction. To address these challenges,we demonstrate that all-dielectric Bragg-reflection microcavitiesoperated near their cutoff frequency, offer an ultralow-loss platformfor enhancing light-matter interaction and exploring emission processesin the ENZ regime. While Bragg cavities are well-established, theirpotential as ENZ resonant microcavities remains largely unexplored.We investigate the Purcell effect and quality factor in these structures,comparing their performance with those of the perfect-electric-conductorand metallic counterparts. Through analytical derivations based onFermi’s golden rule and field quantization in lossless dispersivemedia, we establish scaling laws that distinguish these ENZ cavitiesfrom conventional resonators. Frequency domain simulations validateour counterintuitive findings, demonstrating that in all-dielectricENZ Bragg-reflection microcavities, the Purcell and quality factorsscale as L/λ0 and (L/λ0)3, respectively, where L is the cavity length and λ0 is the resonance wavelength.Our results offer key insights into the design of ENZ-based photonicsystems, paving the way for enhanced light-matter interactions innonlinear optics and quantum photonics.

The Smith–Purcell effect enables electromagnetic radiation across arbitrary spectral ranges by phase-matching the diffraction orders of an optical grating with the near-field of a moving electron. In this work, we introduce a novel approach using a helically shaped waveguide, where phase-matching is achieved through guided light within a helical optical fiber fabricated via two-photon polymerization using a 3D printer. Our results demonstrate that radiation from these structures precisely satisfies the phase-matching condition and is emitted directionally at specific angles, contrasting with the broad angular distribution characteristic of the traditional Smith–Purcell effect. Helical electron-driven photon sources establish a new paradigm, enabling 3D-printed structures to control electron-beam-induced radiation and, inversely, to facilitate light-induced efficient electron beam shaping and acceleration.

Bimetallic gold nanorods decorated with platinum islands (AuNRs@Pt) are widely recognized as promising photothermal agents due to their localized surface plasmon resonance (LSPR) effects, which enable localized heat generation for photothermal therapy (PTT). Additionally, photodynamic therapy (PDT) using photosensitizers (PSs) offers synergistic potential for light-activated cancer treatment. This study investigates the fluorescence behavior and plasmon energy transfer mechanisms of dumbbell-shaped AuNRs@Pt with varying Pt coverages, functionalized with thiolated β-cyclodextrin (SH-βCD) as a host for methylene blue (MB), which serves as a PS. The synthesis and functionalization of AuNRs@Pt revealed tunable plasmon damping pathways, including chemical interface damping and metal interface damping, modulated by Pt deposition and host-guest supramolecular interactions. MB attachment induces plasmon damping, with LSPR damping increasing as the Pt content increases. Functionalization with SH-βCD alters the dielectric environment, while energy dissipation facilitated by Pt islands further amplifies LSPR damping. Molecular dynamics simulations revealed the preferential host-guest interaction of MB with SH-βCD rather than direct interaction with the nanoparticle surface. Meanwhile, MB inclusion increased the local dielectric constant, resulting in redshifts. Notably, host-guest inclusion reduced fluorescence quenching and Förster resonance energy transfer (FRET)-based nonradiative decay, enhancing MB fluorescence and optimizing its emission properties. Additionally, Pt content modulated radiative decay rates and fluorescence quantum yield, with Pt islands amplifying electromagnetic enhancements via the Purcell effect while simultaneously reducing FRET quenching. Therefore, this work lays the foundation for developing advanced theranostic nanoplatforms that leverage the synergy between plasmonic nanoparticles and fluorescence-active molecules for targeted cancer therapies.