Dielectric Microcavity Research Articles

Neural network-based prediction and optimization of optical properties of two-dimensional GaAs dielectric background photonic crystal point-defect microcavities

Neural network-based prediction and optimization of optical properties of two-dimensional GaAs dielectric background photonic crystal point-defect microcavities

Dirac Cones and Room Temperature Polariton Lasing Evidenced in an Organic Honeycomb Lattice.

Artificial 1D and 2D lattices have emerged as a powerful platform for the emulation of lattice Hamiltonians, the fundamental study of collective many-body effects, and phenomena arising from non-trivial topology. Exciton-polaritons, bosonic part-light and part-matter quasiparticles, combine pronounced nonlinearities with the possibility of on-chip implementation. In this context, organic semiconductors embedded in microcavities have proven to be versatile candidates to study nonlinear many-body physics and bosonic condensation, and in contrast to most inorganic systems, they allow the use at ambient conditions since they host ultra-stable Frenkel excitons. A well-controlled, high-quality optical lattice is implemented that accommodates light-matter quasiparticles. The realized polariton graphene presents with excellent cavity quality factors, showing distinct signatures of Dirac cone and flatband dispersions as well as polariton lasing at room temperature. This is realized by filling coupled dielectric microcavities with the fluorescent protein mCherry. The emergence of a coherent polariton condensate at ambient conditions are demonstrated, taking advantage of coupling conditions as precise and controllable as in state-of-the-art inorganic semiconductor-based systems, without the limitations of e.g. lattice matching in epitaxial growth. This progress allows straightforward extension to more complex systems, such as the study of topological phenomena in 2D lattices including topological lasers and non-Hermitian optics.

Two-dimensional silicon-based dielectric column photonic crystal point defect microcavity Neural network modelling

In order to solve the problem that it is difficult to predict the microcavity photonic energy bands of point defects in two-dimensional silicon-based dielectric column photonic crystals, this paper proposes a method to predict the microcavity photonic energy bands of point defects in two-dimensional silicon-based photonic crystals by using an artificial neural network model. In this paper, the energy band structure of triangular lattice point defects at different radii is calculated using MPB, and a neural network model is established based on this data and the accuracy of the established model is verified.

Boosting Performance of Self‐Powered Near‐Infrared Organic Spectral Detector Through Metal–Dielectric Microcavity

AbstractMiniaturized spectrometers that are absent of bulky dispersive optical elements have received more and more attention. However, most of these advancements have been demonstrated in the visible spectrum. Among the various near‐infrared (NIR) absorbers, organic donor–acceptor blends exhibit a distinctive red‐shifted intermolecular charge‐transfer (CT) state absorption, allowing for the detection of NIR photons below the distinct molecular band edge. Nevertheless, the sub‐bandgap absorption cross‐section has been rather limited. In this study, this challenge is addressed by integrating a metal–dielectric (M–D) microcavity into a prototype (PM6:Y6) model system, with a band‐edge positioned at 869 nm. As a result, an amplified narrowband detection, demonstrating an external quantum efficiency of ≈26% at 905 nm is achieved. Furthermore, the manipulation of the cavity lengths enables easy fine‐tuning of the narrowband spectral response within the 850–960 nm range. Leveraging a spectrum reconstruction algorithm, a spectral detector with 10 nm resolution under a zero bias, validating the potential of utilizing sub‐bandgap CT state absorption for efficient narrowband detectors and micro‐spectrometers is obtained.

Nanosecond-Pulsed Passively Q-Switched Fiber Laser by Using Photothermal Dynamics in a Dielectric Microcavity

Nanosecond-Pulsed Passively Q-Switched Fiber Laser by Using Photothermal Dynamics in a Dielectric Microcavity

Comment to the paper “Quantum mechanical effects for a hydrogen atom confined in a dielectric spherical microcavity”

The article “Quantum mechanical effects for a hydrogen atom confined in a dielectric spherical microcavity” (Wang et al., 2022) does not describe correctly the Shannon entropy for the states 3p and 4p for the hydrogen atom confined by a dielectric spherical microcavity. In this comment, we show the correct behavior for these states and conclude that there was an error in the data found by the authors of that article. Thus, looking for a physical meaning for the behavior observed in that paper makes no sense.

Jaynes-Cummings interaction between low-energy free electrons and cavity photons.

The Jaynes-Cummings Hamiltonian is at the core of cavity quantum electrodynamics; however, it relies on bound-electron emitters fundamentally limited by the binding Coulomb potential. In this work, we propose theoretically a new approach to realizing the Jaynes-Cummings model using low-energy free electrons coupled to dielectric microcavities and exemplify several quantum technologies made possible by this approach. Using quantum recoil, a large detuning inhibits the emission of multiple consecutive photons, effectively transforming the free electron into a few-level system coupled to the cavity mode. We show that this approach can be used for generation of single photons, photon pairs, and even a quantum SWAP gate between a photon and a free electron, with unity efficiency and high fidelity. Tunable by their kinetic energy, quantum free electrons are inherently versatile emitters with an engineerable emission wavelength. Hence, they pave the way toward new possibilities for quantum interconnects between photonic platforms at disparate spectral regimes.

Grayscale-patterned integrated multilayer-metal-dielectric microcavities for on-chip multi/hyperspectral imaging in the extended visible bandwidth.

Pixelated filter arrays of Fabry-Perot (FP) cavities are widely integrated with photodetectors to achieve a WYSIWYG ("what you see is what you get") on-chip spectral measurements. However, FP-filter-based spectral sensors typically have a trade-off between their spectral resolution and working bandwidth due to design limitations of conventional metal or dielectric multilayer microcavities. Here, we propose a new idea of integrated color filter arrays (CFAs) consisting of multilayer metal-dielectric-mirror FP microcavities that, enable a hyperspectral resolution over an extended visible bandwidth (∼300 nm). By introducing another two dielectric layers on the metallic film, the broadband reflectance of the FP-cavity mirror was greatly enhanced, accompanied by as-flat-as-possible reflection-phase dispersion. This resulted in balanced spectral resolution (∼10 nm) and spectral bandwidth from 450 nm to 750 nm. In the experiment, we used a one-step rapid manufacturing process by using grayscale e-beam lithography. A 16-channel (4 × 4) CFA was fabricated and demonstrated on-chip spectral imaging with a CMOS sensor and an impressive identification capability. Our results provide an attractive method for developing high-performance spectral sensors and have potential commercial applications by extending the utility of low-cost manufacturing process.

Internal disorder of hydrogenic-like atom trapped in dielectric spherical microcavity

The research on the disorder of quantum system plays a very important role in the field of quantum information, and has received much attention from theoretical and experimental researchers. However, it is very difficult to study the disorder of atoms trapped in microcavity due to their complex nonlocal space-time evolution characteristics. To solve this problem, we present a method to study the internal disorder of hydrogenic atoms trapped in microcavity, that is, to characterize and investigate the disorder of the confined system by using the quantum information entropy and shape complexity of the system. The Shannon information entropy and shape complexity in position space and momentum space (<i>S</i><sub><i>r</i></sub>, <i>S</i><sub><i>p</i></sub>, <i>C</i>[<i>r</i>], <i>C</i>[<i>p</i>]) are calculated and analyzed for different quantum states of hydrogenic atom in InN dielectric spherical microcavity, and pay special attention to the exploration of the influence of quantum confinement effect on the disorder of the system. The results show that when the radius of the spherical microcavity is very small, the quantum confinement effect is more significant, and a series of extreme points appears in the shape complexity curve of the system, which is caused by the joint interaction of information entropy and spatial inhomogeneity. With the increase of the radius of the spherical cavity, the effect of quantum confinement is weakened, and the Shannon information entropy and shape complexity of the confined hydrogenic atom are similar to the counterparts of the hydrogenic atom in free space. Our work provides an effective method to study the internal disorder of a confined quantum. This work provides an effective method for studying the internal disorder of confined quantum systems and presents some references for the information measurement of confined quantum systems.

Exciton–polaritons of hBN/WS2 heterostructure in cavity observed at room temperature

The layer-by-layer buildup of a two-dimensional transition metal dichalcogenide monolayer to form a stack is an important development for these materials, which performs many remarkable properties in the light–matter interaction. Herein, we find clear evidence of exciton–polaritons emerging from WS2/hBN/WS2 heterostructures embedded in a dielectric microcavity under optical pumping. A large Rabi splitting of 15 meV is observed at room temperature, which increases to 25 meV at 5 K. An all-dielectric Fabry–Pérot microcavity provides a simple but effective way to study the room temperature strong coupling between cavity photons and excitons. Our results pave the way for room-temperature polaritonic devices based on quantum-well van der Waals heterostructures.

Tale of Two Resonances: Waveguide–Plasmon Coupling and High Q-Factor Engineering on the Nanoscale

Localized surface plasmon (LSP) excitations provide an efficient strategy for advancing nanophotonic designs and applications where strong field enhancement and confinement are often required on the nanoscale. They represent an important plasmonic paradigm for achieving strong light–matter interactions in both linear and nonlinear regimes, enabling the development of high-performance chemical and biological sensing approaches and nonlinear optics with low light intensities. However, the LSP resonance line width, limited by both radiative and resistive losses of metallic nanostructures, is significantly larger than the line width of the waveguided modes supported by low-loss dielectric microcavities with a significantly lower field confinement. Hybrid microcavity–plasmonic systems are, therefore, often used to reduce the resonant line width which improves the detection spectral resolution while maintaining strong confinement. Employing the remarkable quality factors of whispering gallery mode (WGM) microresonators, the hybrid LSP-WGM systems demonstrate sensing capabilities down to the single-molecule level. In this Perspective, we review the recent advances in the hybridization of LSPs and WGMs, focusing on the fundamental understanding of the underlying coupling mechanisms and corresponding mode hybridization regimes. We further discuss opportunities for applying heterogeneous plasmonic–photonic integration to tailor the nanoscale light–matter interactions and realize novel waveguide–plasmon coupling based nontrivial responses and highlight their prospective applications in quantum optics, chiral spin-optics, nonlinear nanophotonics, and sensing.

On‐Chip Multiwavelength Single‐Mode Lasers with CdSe Nanoribbons‐Embedded Microcavities

Integrated multiwavelength nanolasers are important in the practical development of optical circuitry for optical information processing and optical data storage. Herein, a new method for on‐chip integrated lasers is proposed, which can integrate single‐mode lasers with multiple wavelengths at room temperature. A four‐wavelength single‐mode nanoribbon laser chip is fabricated for demonstration. The mode of different laser units is controlled by the thickness of dielectric microcavity layers to select the resonant modes of excitation. Therefore, multiwavelength lasing can be coupled out based on the integrated cavity which is realized using combinatorial etching technique and can integrate tens of different‐wavelength lasers on a chip. The lasing modes of this device are all single‐mode lasing because of the short cavity length. Its lowest lasing threshold is only 5.4 kW cm−2. The gain material and the dielectric microcavity can be controlled and fabricated separately, which have strong controllability and flexibility. This new laser chip paves the way for a new class of hybrid nanolasers for chip‐integrated applications.

Antisymmetric Mode Cancellation for High-Q Cavities in a Double-Disk

High-quality factor dielectric microcavities like whispering-gallery-mode resonators can be widely applied in fields such as laser, optical sensor, switch, and filter. We propose the whispering-gallery-mode double-disk cavity comprising dielectric disks apart along the face of the disk. The electric field of each disk with opposite phases was excited; the emitted radiation field was annihilated by destructive interference. We numerically achieved a 5.67-fold enhancement in quality factor at the double-disk cavity with a radius, thickness, and gap distance of 850 nm, 220 nm, and 220 nm, respectively, compared to a single dielectric disk with the same structural conditions.

Accurate determination of low-dimensional materials’ complex refractive index by cavity resonant method

Low-dimensional (LD), especially two-dimensional(2D) materials have unique optical and photoelectric properties which can be used in fields such as nanolasers, sensors and communications. Complex refractive index including refractive index n and extinction coefficient k of LD materials is vital for the design of optical devices. However, it is difficult to be accurately measured because the thickness and size of LD, especially 2D materials, are too small. In this work, a new cavity-resonant method is proposed to solve this problem by embedding materials into dielectric optical microcavities. The n and k of embedded LD materials can be accurately obtained by measuring the shift and intensity of cavity mode with and without them. This method is valid for any monolayer 2D materials since the cavity structures and materials can be prepared separately. The complex refractive index of small size monolayer WS2 and MoS2 were obtained by this method for demonstration. The o and e light refractive index of CdS nanoribbon can also be determined by the cavity resonant method easily. The results show that it can precisely determine the complex refractive index of ultrathin and miniature size LD materials, which is especially useful for the study and development of LD materials based optical devices.

Localization of Laterally Confined Modes in a 2D Semiconductor Microcavity

Monolayer semiconductor embedded planar microcavities are becoming a promising light-matter interacting system to uncover a wealth of photonic, excitonic, and polaritonic physics at the two-dimensional (2D) limit. In these 2D semiconductor microcavities employing the longitudinal Fabry-Perot resonance, major attention has been paid to the coupling of excitons with vertically confined cavity photons; by contrast, the lateral confinement effect on exciton-photon interactions is still elusive. Here we observe the localized distribution of laterally confined modes with discrete energies in a 2D semiconductor embedded microcavity. Monolayer tungsten disulfides with equilateral triangular geometries but varied edge lengths are selected as the active media incorporated into a dielectric planar microcavity. With the shortening of the edge length, photoluminescence mappings of active regions present spatially localized emission patterns, which are attributed to the presence of in-plane triangular waveguiding resonance caused by total internal reflection at the one-dimensional closed boundary between the monolayer semiconductor and its surrounding cavity material. Unlike the conventional quantum confinement effect of native excitons appearing at the nanometer scale, the mode emission at the active-medium center exhibits apparent size-dependent features at the micrometer scale due to the optical confinement effect correlated with its photonic nature. By reducing the area of active media, single-mode dominant emission is achieved together with its nondispersive energy and improved directionality. Our work highlights the crucial role of lateral mode control in monolayer semiconductor embedded planar microcavities and encourages the investigation of the quantum billiard problem in 2D semiconductors.

Microcavity-like exciton-polaritons can be the primary photoexcitation in bare organic semiconductors

Strong-coupling between excitons and confined photonic modes can lead to the formation of new quasi-particles termed exciton-polaritons which can display a range of interesting properties such as super-fluidity, ultrafast transport and Bose-Einstein condensation. Strong-coupling typically occurs when an excitonic material is confided in a dielectric or plasmonic microcavity. Here, we show polaritons can form at room temperature in a range of chemically diverse, organic semiconductor thin films, despite the absence of an external cavity. We find evidence of strong light-matter coupling via angle-dependent peak splittings in the reflectivity spectra of the materials and emission from collective polariton states. We additionally show exciton-polaritons are the primary photoexcitation in these organic materials by directly imaging their ultrafast (5 × 106 m s−1), ultralong (~270 nm) transport. These results open-up new fundamental physics and could enable a new generation of organic optoelectronic and light harvesting devices based on cavity-free exciton-polaritons

Quantum mechanical effects for a hydrogen atom confined in a dielectric spherical microcavity

The quantum mechanical effects for a hydrogen atom confined in a dielectric spherical microcavity is discussed for the fist time. Especially we calculate the energy and Shannon entropy of this system. Some unexpected and interesting phenomena appear due to the effect of the dielectric spherical microcavity. Firstly, the energy of this system is not always negative. For smaller spherical microcavity, the energy can be positive. The turning radius for the bound energy changes from positive to negative depends on the dielectric constant of the spherical microcavity sensitively. Second, the dielectric spherical microcavity impacts the rearrangement of the excited state energy, and breaks the energy degeneracy of the excited states. At some given radius, there is energy crossover between different orbital. Third, the dielectric in the spherical microcavity affects the Shannon entropy change for the confined hydrogen atom greatly. When the size of the spherical microcavity is small, the Shannon entropy change is negative, which suggests that the electron density is localized. As we increase the radius of the microcavity, the Shannon entropy change becomes positive, and the confinement of the electron density gets delocalized. Our results show that we can control the quantum mechanical effects of the atom by changing the dielectric constant in the spherical microcavity. This work can guide the future experimental studies for trapping and manipulating of atoms and molecules in the external environment and has some practical applications in metrology and quantum information processing.

Dirac fermion optics and directed emission from single- and bilayer graphene cavities

High-mobility graphene hosting massless charge carriers with linear dispersion provides a promising platform for electron optics phenomena. Inspired by the physics of dielectric optical micro-cavities where the photon emission characteristics can be efficiently tuned via the cavity shape, we study corresponding mechanisms for trapped Dirac fermionic resonant states in deformed micro-disk graphene billiards and directed emission from those. In such graphene devices a back-gate voltage provides an additional tunable parameter to mimic different effective refractive indices and thereby the corresponding Fresnel laws at the boundaries. Moreover, cavities based on single-layer and double-layer graphene exhibit Klein- and anti-Klein tunneling, respectively, leading to distinct differences with respect to dwell times and resulting emission profiles of the cavity states. Moreover, we find a variety of different emission characteristics depending on the position of the source where charge carriers are fed into the cavites. Combining quantum mechanical simulations with optical ray tracing and a corresponding phase-space analysis, we demonstrate strong confinement of the emitted charge carriers in the mid field of single-layer graphene systems and can relate this to a lensing effect. For bilayer graphene, trapping of the resonant states is more efficient and the emission characteristics do less depend on the source position.

Bosonic condensation of exciton-polaritons in an atomically thin crystal.

The emergence of two-dimensional crystals has revolutionized modern solid-state physics. From a fundamental point of view, the enhancement of charge carrier correlations has sparked much research activity in the transport and quantum optics communities. One of the most intriguing effects, in this regard, is the bosonic condensation and spontaneous coherence of many-particle complexes. Here we find compelling evidence of bosonic condensation of exciton-polaritons emerging from an atomically thin crystal of MoSe2 embedded in a dielectric microcavity under optical pumping at cryogenic temperatures. The formation of the condensate manifests itself in a sudden increase of luminescence intensity in a threshold-like manner, and a notable spin-polarizability in an externally applied magnetic field. Spatial coherence is mapped out via highly resolved real-space interferometry, revealing a spatially extended condensate. Our device represents a decisive step towards the implementation of coherent light-sources based on atomically thin crystals, as well as non-linear, valleytronic coherent devices.

Polygonal patterns of confined light.

We propose a technique for the generation of polygonal optical patterns in real space using a combined effect of the spin-orbit interaction and confinement of light in the plane of a dielectric optical microcavity. The spin-orbit interaction emerging from the splitting in transverse electric (TE) and transverse magnetic (TM) optical modes of the microcavity gives rise to oscillations in space of propagating macroscopic wave packets of polarized photons. Confined in a harmonic potential, the latter follow closed trajectories of a polygonal form. We demonstrate the possibility of excitation by a continuous wave resonant optical pumping of polygonal optical patterns with a controllable (both even and odd) number of vertices.