Types Of Microcavities Research Articles

Purcell enhanced single-photon emission from a quantum dot coupled to a truncated Gaussian microcavity

Purcell enhancement of quantum dot (QD) single-photon emission and increased device brightness have been demonstrated with various types of microcavities. Here, we present the first realization of a truncated Gaussian-shaped microcavity coupled to a QD. The implementation is based on wet-chemical etching and epitaxial semiconductor overgrowth. The cavity modes and their spatial profiles are experimentally studied and agree well with simulations. The fundamental mode wavelength with Q-factors around 6000 and a small polarization splitting of 29 μeV can be reproducibly controlled via fabrication design, enabling the adaption of the cavity to a specific QD. Finally, transitions of a QD inside a cavity are tuned on and off resonance via temperature tuning. A reduced decay time by a factor above 3 on resonance clearly indicates Purcell enhancement while second-order correlation measurements of g(2)(0) = 0.057 prove that the QDs single-photon characteristic is preserved.

Perovskite semiconductors for room-temperature exciton-polaritonics

Lead-halide perovskites are generally excellent light emitters and can have larger exciton binding energies than thermal energy at room temperature, exhibiting great promise for room-temperature exciton-polaritonics. Rapid progress has been made recently, although challenges and mysteries remain in lead-halide perovskite semiconductors to push polaritons to room-temperature operation. In this Perspective, we discuss fundamental aspects of perovskite semiconductors for exciton-polaritons and review the recent rapid experimental advances using lead-halide perovskites for room-temperature polaritonics, including the experimental realization of strong light-matter interaction using various types of microcavities as well as reaching the polariton condensation regime in planar microcavities and lattices.

Enhancement of the quantum dot photoluminescence using transfer-printed porous silicon microcavities

Enhancement of the photoluminescence signal intensity from organic and inorganic fluorophores increases the sensitivity of operation of optical sensors, detectors, and photonic diagnostic assays. Here, we have engineered and compared optical and fluorescence-enhancing properties of two types of one-dimensional porous silicon photonic crystals: a transfer-printed microcavity based on the freestanding photonic crystal and a conventional “one-piece” microcavity created on a monocrystalline silicon substrate. Comparative analysis of the eigenmodes and the photonic bandgaps of both types of microcavities demonstrated a high quality of transfer-printed microcavities and good correlation of their reflection spectra with the spectra of “one-piece” microcavities. Moreover, embedding of a highly concentrated solution of quantum dots (QDs) in the eigenmode localization region of transfer-printed microcavity was followed by three-fold reduction of the full-width-at-half-maximum of their luminescence spectrum at the microcavity eigenmode wavelength, thus confirming a weak coupling regime of QD exciton and microcavity eigenmode interaction and significant enhancement of QD luminescence within the microcavity.

Polarization nondegenerate fiber Fabry-Perot cavities with large tunable splittings

We demonstrate a type of microcavity with large tunable splitting of polarization modes. This polarization nondegenerate cavity consists of two ellipsoidal concave mirrors with controllable eccentricity by CO2 laser machining on fiber end facets. The experiment shows that the cavities can combine the advantages of high finesse above 104 and large tunable polarization mode splitting to the GHz range. As the splitting of the cavity can be finely controlled to match atom hyperfine levels or optomechanics phonons, it will blaze a way in experiments on cavity quantum electrodynamics and cavity optomechanics.

Surface plasmon-enhanced two-photon excited whispering-gallery modes ultraviolet laser from Zno microwire

The two-photon excited UV laser with narrow line width and high Q value was obtained. The total internal reflection from the four side surfaces of the quadrilateral-ZnO microwire offered the whispering gallery mode (WGM) resonant cavity. The UV emission, resonant mechanism, and laser mode characteristics were discussed in detail for this special type of micro-cavity. In addition, in order to enhance the power of the two-photon excited UV laser, the surface plasmon enhancement by the Au nanoparticles was also performed and explained well by the theory of the localized surface plasmon.

On-Chip High-Finesse Fabry-Perot Microcavities for Optical Sensing and Quantum Information.

For applications in sensing and cavity-based quantum computing and metrology, open-access Fabry-Perot cavities—with an air or vacuum gap between a pair of high reflectance mirrors—offer important advantages compared to other types of microcavities. For example, they are inherently tunable using MEMS-based actuation strategies, and they enable atomic emitters or target analytes to be located at high field regions of the optical mode. Integration of curved-mirror Fabry-Perot cavities on chips containing electronic, optoelectronic, and optomechanical elements is a topic of emerging importance. Micro-fabrication techniques can be used to create mirrors with small radius-of-curvature, which is a prerequisite for cavities to support stable, small-volume modes. We review recent progress towards chip-based implementation of such cavities, and highlight their potential to address applications in sensing and cavity quantum electrodynamics.

Magneto-optical characteristics of layered Epsilon-Near-Zero metamaterials

The transmittance magneto-optical (MO) characteristics of Epsilon-Near-Zero (ENZ) metamaterials are studied, using 4 by 4 transfer matrix method. The considered structures are a free standing ENZ-MO slab, and a microcavity type multi-layer structure containing an ENZ-MO layer. The transmittance coefficients of the right- and left-handed circular polarizations for the slab are analytically obtained and numerically investigated. Furthermore, these characteristics are numerically studied for the multi-layer structure. In addition, the Faraday rotations of both structures are investigated. The results reveal the circular polarization filtering effects.

Whispering‐gallery microcavities with unidirectional laser emission

AbstractOptical whispering‐gallery mode (WGM) microcavities featuring ultrahigh Q factors and small mode volumes enhance significantly the interaction between light and matter, becoming an excellent platform for achieving ultralow‐threshold microlasers. However, the emission of traditional WGMs is isotropic due to the rotational symmetry of cavity geometries, which hinders the potential photonics applications. In this review, the progress in WGM microcavities towards unidirectional laser emission is summarized. When a subwavelength scatterer is placed on the boundary of the microcavity, the unidirectional emission occurs due to the collimation effect of the microcavity‐enhanced scattering field. Furthermore, microcavities deformed from the circular shapes can not only produce the chaos‐assisted unidirectional emission, but also maintain high Q factors by special design and fabrication processes. Finally, gratings along the circumference of the WGM microdisk or microring can scatter the WGMs in the vertical direction. The review also lists several important applications of these types of microcavities, such as wide‐band laser illumination source, free‐space coupling, evanescent‐field enhancement, optical energy storage, and sensing. image

Plasmon-Enhanced Whispering Gallery Mode Lasing from Hexagonal Al/ZnO Microcavity

Wurtzite structural ZnO microrods with hexagonal cross section were fabricated by a simple vapor transport method and an individual ZnO microrod was employed as a whispering gallery microcavity. The obviously enhanced spontaneous and stimulated emissions were observed as the ZnO microrod was decorated with Al nanoparticles (NPs). Based on the absorption spectrum of Al NPs, the underlying mechanism was proposed and can be attributed to the resonant coupling between excitons of ZnO and surface plasmons (SPs) of Al NPs at the metal/ZnO interface on the surface of microcavity. In addition, the threshold of the ZnO microcavity decorated with Al NPs has reduced by half compared with that of the bare one, which provides additional evidence to support the energy coupling between the ZnO microrod and Al NPs. The controllability and improved emission properties of these types of microcavities are potentially important for designing highly efficient optoelectronic devices.

Plasmon-enhanced ultraviolet photoluminescence from the hybrid plasmonic Fabry–Perot microcavity of Ag/ZnO microwires

We propose a kind of hybrid plasmonic Fabry-Perot (F-P) microcavity consisting of ZnO microwires with quadrate cross-section and planar multilayer metal-insulator-metal (MIM) homostructures with a nanoscale SiO₂ gap in between. MIM homostructures can be used to create a micro-resonator that simultaneously provides feedback for laser action and supports the coupling between the plasmonic waveguide modes and microwire modes across the gap. The hybridization of ZnO microwire modes and surface plasmons across the gap forms hybrid plasmonic F-P microcavity modes, which are highly confined to the low-loss SiO₂ gap region. By comparing with bare ZnO microwires, an enhancement in photoluminescence (PL) intensity of two orders of magnitude is realized experimentally due to the coupling between plasmonic MIM homostructures and ZnO microwires. The controllability and miniaturization emission properties of this type of microcavity are potentially important for designing laser cavity applications and information transmission.

Circular polarization bandpass filters based on one-dimensional magnetophotonic crystals

The realization of circular polarization band pass filters based on defect mode splitting in one-dimensional magnetophotonic crystals (1D-MPCs) was investigated theoretically using the transfer matrix method. The analytical formulas of the resonance conditions are derived. The results reveal that for a specific repetition number of the microcavity type 1D-MPC structure, the defect mode splits into two completely separated modes, corresponding to right- and left-circular polarization resonances. It is shown that these modes have purely circular polarization states, which enables us to propose the structure as a single and dual channel circular polarization filter. Furthermore, the tuning properties of the considered structure under the variation of exterior magnetic field are studied.

AlGaAs microdisk cavities for second-harmonic generation

We report on the design, the fabrication, and the optical characterization of AlGaAs microdisks suspended on a GaAs pedestal, conceived for second-harmonic generation with a pump in the third telecom window. We discuss the results concerning the linear characterization of whispering gallery modes at fundamental and second-harmonic wavelengths, an essential step prior to the investigation of quasi-phase-matched processes in this type of microcavity.

Influence of arrangement order ratio on the magneto-optical properties of one-dimensional microcavity structures

The dependence of the optical responses of microcavity-type one-dimensional (1D) photonic crystals and 1D magnetophotonic crystals (1D-MPCs) on the arrangement order ratio (AOR), which is the ratio of the first and second layers' refractive indexes of Bragg reflectors, is studied. It is demonstrated that the optical properties of two microcavity structures resulting from exchanging the order of Bragg reflector layers so that they have the same optical contrast ratios and different AORs would be different. This difference will be more noticeable in the case of microcavity type 1D-MPCs. Regarding the arrangement-dependent magneto-optical properties of the structures, we can propose the efficient Bragg reflectors with high transmittance enhanced Faraday rotation.

Terahertz Plasmonic Microcavity with High Quality Factor and Ultrasmall Mode Volume

In this paper, the characteristics of a novel terahertz plasmonic microcavity consisting of a circular hole and a coaxial (metallic) cylindrical core machined on a planar metal surface is theoretically investigated. It is shown that such a structure can sustain plasmonic modes, whose resonant wavelengths are much larger than the hole diameter and fields tightly localized within the cavity. For this cavity, both high quality factor and ultrasmall mode volume can be achieved in the terahertz range. As this type of microcavity is particularly compatible with planar technology, it has promising applications in the miniaturization and integration of terahertz optical components.

A microfiber cavity with minimal-volume confinement

We demonstrate a type of microcavity with minimal-volume confinement using a high-contrast phase-shifted Bragg grating in a microfiber. While waveguiding by the air-silica boundary provides a diffraction-limited two-dimensional confinement, the grating introduces the third degree of confinement. Theoretical simulations verified the microfiber cavity confinement while the experimental demonstration, carried out in samples nanostructured by focused ion beam, showed a good agreement with theoretical predictions. This cavity can be used for a variety of applications ranging from sensing to quantum dynamic experiments.

Far infrared Faraday rotation effect in one-dimensional microcavity type magnetic photonic crystals

The far infrared transmittances and Faraday rotation effect in one-dimensional photonic crystals that contain magnetic microcavities are calculated with the transfer matrix method. The different stacking sequences of dielectric layers in the magnetic photonic crystal are considered in this paper, and the linewidths of transmission peaks and localised light of the photonic crystals are discussed. The enhancement of Faraday rotation is presented in the magnetic photonic crystals, and the largest rotation angle at the frequency of the transmission peak is 29 °mm −1, which is larger than previous results.

Bloch oscillations in one-dimensional photonic crystal coupled microcavity composed of single-negative materials

We have studied the propagation properties of electromagnetic waves in one-dimensional photonic crystal coupled microcavity structure composed of single-negative materials. Two Wannier–Stark ladders can be obtained by employing only one type of microcavity. The dynamics behavior of a Gaussian pulse transmitting through the structure is simulated theoretically. We demonstrated for the first time that even in this multilayered structure completely made of single-negative materials, the optical Bloch oscillations and Zener tunneling can also be attained.

Large vacuum Rabi splitting in a multiple quantum well GaN-based microcavity in the strong-coupling regime

An $\mathrm{Al}\mathrm{In}\mathrm{N}∕\mathrm{Al}\mathrm{Ga}\mathrm{N}$ microcavity (MC) containing a $\mathrm{Ga}\mathrm{N}∕{\mathrm{Al}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{N}$ multiple quantum well (MQW) structure is investigated through room temperature (RT) photoluminescence and reflectivity experiments. A vacuum Rabi splitting as large as $50\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ at RT is reported for this MC structure, the highest value reported so far for a semiconductor MC containing QWs. This is shown to result from a geometry combining a state of the art nitride-based MC with a MQW system where the built-in electric field has a reduced impact on the oscillator strength of optical transitions. The contribution of Bragg modes seen in optical spectra is well accounted for by transfer matrix simulations. In addition, the sensitivity of the present system to the tuning between the various optical components of the microcavity (bottom and top Bragg reflectors and active cavity region) to maximize the strong-coupling regime is also shown through simulations. Prospects regarding the nonlinear polariton emission from such a structure indicate that this type of MCs could potentially sustain ultrafast polariton parametric amplification up to $440\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, thanks to an increased exciton binding energy. More generally, it is predicted that, owing to a large exciton saturation density in excess of $1\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$ per QW, such a MC structure would be suitable for the observation of nonlinear effects associated with cavity polaritons (polariton lasing and polariton Bose-Einstein condensates) at RT and above.

Self-Aligned All-Epitaxial Microcavity for Cavity QED with Quantum Dots

Using time-resolved photoluminescence spectroscopy, we have studied the Purcell spontaneous emission enhancement provided by a novel type of microcavity that forms a fully buried, all-epitaxial semiconductor heterostructure. The quantum dot containing region and the cavity boundaries are simultaneously defined in a unique way and lead to spatially self-aligned emitters. We demonstrate post-growth control of the quality factor and the capability of directly imaging the spatial field distribution that critically impacts the Purcell effect.

Lens-shaped all-epitaxial quantum dot microcavity

Data are presented on a new type of microcavity that uses epitaxial overgrowth to localize self-organized quantum dots in a microcavity optical mode. The all-epitaxial design eliminates free surfaces from the active material, eliminates quantum dots from the mirror and passive cavity regions, and provides a mechanically robust design with high thermal conductivity. The epitaxial overgrowth leads to a new type of lens-shaped microcavity, while the mesa confinement leads to lithographically defined placement of the quantum dots near the center of the optical mode.