Optical Microcavities Research Articles

Dark and thermal reservoir contributions to polariton sound velocity

Exciton-polaritons in an optical microcavity can form a macroscopically coherent state despite being an inherently driven-dissipative system. In comparison with equilibrium bosonic fluids, polaritonic condensates possess multiple peculiarities that make them behave differently from well-known textbook examples. One such peculiarity is the presence of dark excitons which are created by the pump together with optically active particles. They can considerably affect the spectrum of elementary excitations of the condensate and hence change its superfluid properties. Here, we theoretically analyze the influence of the bright and dark ``reservoir'' populations on the sound velocity ${c}_{s}$ of incoherently driven polaritons. Both pulsed and continuous-wave pumping schemes characterized by essentially different condensate-to-reservoir ratios are considered. We show that the dark exciton contribution leads to considerable lowering of ${c}_{s}$ and to its deviation from the square-root-like behavior on the system's chemical potential (measurable condensate blueshift). Importantly, our model allows us to unambiguously define the density of dark excitons in the system by experimentally tracking ${c}_{s}$ against the condensate blueshift and fitting the dependence at a given temperature.

Mid-infrared ultra-broadband optical Kerr frequency comb based on a CdTe ring microresonator: a theoretical investigation.

Microresonator Kerr frequency combs are coherent light sources that emit broadband spectrum of evenly spaced narrow lines in an optical microresonator, which provide breakthroughs in many technological areas, such as spectroscopy, metrology, optical telecommunications, and molecular sensing. The development of mid-infrared (MIR) optical frequency comb (OFC) based on microresonators could pave the way for high performance spectroscopy in the MIR "molecular fingerprint" region. However, the generation of microresonator MIR OFC, especially towards the long-wavelength MIR (>10 µm) region, is prohibited by the transmission window of the commonly used Kerr optical media such as Si and Si3N4, and low nonlinearity at long wavelengths. Here, we seek the possibility to realize an ultra-broadband frequency comb operating in the long-wavelength MIR region based on a cadmium telluride (CdTe) ring microresonator. CdTe features a broad transmission range covering the wavelengths of 1∼25 µm, a flat dispersion profile, and an extraordinary third-order nonlinear refractive index (∼1.4 × 10-17 m2W-1 at 7 µm) which is 2-order greater than that of Si3N4, making it a promising platform to realize MIR Kerr frequency comb. Based on the above excellent optical properties, we design a CdTe/cadmium sulfide (CdS)/Si heterojunction microring resonator to generate an ultra-broadband MIR OFC. Through the numerical simulation, the geometric parameters (width, height, and radius) of the microresonator, polarization, wavelength of the pump, and quality factor are investigated and optimized. As a result, a MIR OFC covering 3.5∼18 µm is numerically demonstrated by using the pump wavelength of 7 µm and a pump power of 500 mW. This is the first simulation demonstration of Kerr OFC with the spectral range extending beyond 10 µm, to the best of our knowledge. This work provides new opportunities for the realization of ultrabroad microresonator frequency combs based on novel Kerr optical medium, which can find important applications ranging from calibration of astronomical spectrographs to high-fidelity molecular spectroscopy.

A Microring as a Reservoir Computing Node: Memory/Nonlinear Tasks and Effect of Input Non-Ideality

The nonlinear response of an optical microresonator is used in a time multiplexed reservoir computing neural network. Within a virtual node approach combined with an offline training through ridge regression, we solved linear and nonlinear logic operations. We analyzed the nonlinearity of the microresonator as a memory between bits and/or as a neural activation function. This is made possible by controlling both the distance between bits subject to the logical operation and the number of bits supplied to the ridge regression. We show that the optical microresonator exhibits up to two bits of memory in linear tasks and that it allows solving nonlinear tasks providing both memory and nonlinearity. Finally, we demonstrate that the virtual node approach always requires a comparison of the reservoirs performance with the results obtained by applying the same training process on the input signal.

Enhancement of Dissipative Sensing in a Microresonator Using Multimode Input.

Optical whispering-gallery microresonators have proven to be especially useful as chemical sensors. Most applications involve dispersive sensing, such as the frequency shift of resonator modes in response to a change in the ambient index of refraction. However, the response to dissipative interaction can be even more sensitive than the dispersive response. Dissipative sensing is most often conducted via a change in the mode linewidth owing to absorption in the analyte, but the change in the throughput dip depth of a mode can provide better sensitivity. Dispersive sensing can be enhanced when the input to the microresonator consists of multiple fiber or waveguide modes. Here, we show that multimode input can enhance dip-depth dissipative sensing by an even greater factor. We demonstrate that the multimode-input response relative to single-mode-input response using the same fiber or waveguide can be enhanced by a factor of more than one thousand, independent of the mode linewidth, or quality factor (Q), of the mode. We also show that multimode input makes the dip-depth response nearly one hundred times more sensitive than the linewidth-change response. These enhancement factors are predicted by making only two measurements of dip depth in the absence of an analyte: one with the two input modes in phase with each other, and one with them out of phase.

Dissipative solitons in optical microresonators

<p indent="0mm">A soliton is a stationary local structure that keeps its waveform and spreading speed during propagation. Recent research shows that chip-scale optical microresonators can support dissipative solitons with surprisingly high energy efficiency and stability. The formation of optical microresonator dissipative solitons requires two balances, gain-loss balance and dispersion-nonlinearity balance. The gain-loss balance maintains the soliton’s amplitude while the dispersion-nonlinearity balance keeps its width. In this paper, we review the formation, development, and applications of dissipative optical solitons, as well as dissipative mechanical solitons in optical microresonators, and analyze the balances in different solitons. This review mainly consists of two parts: Optical microresonator dissipative solitons and opto-mechanical microresonator dissipative solitons. The first part discusses a typical kind of solitons named dissipative Kerr solitons. Dissipative Kerr solitons balance the propagation dispersion through Kerr nonlinearity in optical microresonators and are widely studied due to their easy implementation in silicon-based microcavities. In order to improve the practical performance of dissipative Kerr solitons, researchers have proposed many schemes to improve their stability and efficiency. Meanwhile, various high-precision sensing applications based on dissipative Kerr solitons, such as photonic radar, range measurement, and absorption spectrum detection, have drawn extensive attention. The second part introduces the dissipative solitons in optomechanical microresonators. A recently-discovered type of solitons, optomechanical dissipative solitons, is introduced. Unlike the dissipative Kerr solitons, the optomechanical dissipative solitons gain their power from phonon lasing, and compensate the propagation dispersion by optomechanical nonlinearity. The dynamics of the optomechanical dissipative solitons are described by the modified Korteweg-de Vries equation. Low-frequency optomechanical dissipative solitons can achieve kHz-accuracy acoustic signal measurement, which can be used in acoustic detection and communication. Finally, we summarize the formation, development, and applications of dissipative solitons in optomechanical microresonators. We also provide an outlook for future applications like radio-frequency calibration, radio-frequency communications, and underwater tomography.

Superfluid drag between excitonic polaritons and superconducting electron gas

The Andreev-Bashkin effect, or superfluid drag, is predicted in a system of Bose-condensed excitonic polaritons in optical microcavity coupled by electron-exciton interaction with a superconducting layer. Two possible setups with spatially indirect dipole excitons or direct excitons are considered. The drag density characterizing a magnitude of this effect is found by many-body calculations with taking into account dynamical screening of electron-exciton interaction. For the superconducting electronic layer, we assume the recently proposed polaritonic mechanism of Cooper pairing, although the preexisting thin-film superconductor should also demonstrate the effect. According to our calculations, the drag density can reach considerable values in realistic conditions, with excitonic and electronic layers made from GaAs-based quantum wells or two-dimensional transition metal dichalcogenides. The predicted nondissipative drag could be strong enough to be observable as induction of a supercurrent in the electronic layer by a flow of polariton Bose condensate.

Exceptional points with memory in a microcavity Brillouin laser

Exceptional points (EPs), universally present in non-Hermitian systems, often reveal some critical behaviors such as topological encircling chirality and ultrahigh enhanced sensing near such singularities. However, most of the experimental realizations of EPs have been limited to the linear regime, where system nonlinearity has been omitted. Here, we experimentally observe two distinct EPs with opposite hermiticities and demonstrate a parity–time phase transition with exotic memory effects near the EPs in a nonlinear and non-Hermitian system based on a stimulated Brillouin laser in an optical microcavity. The self-phase modulation induced nonlinearity effectively alters the EP location, surprisingly, in an asymmetric manner, resulting in a bistable memory effect. Moreover, two EPs with opposite hermiticities in the same system are found to show quite distinct behaviors in such a memory effect. This scheme completes the studies of non-Hermitian physics in a more general scenario by including nonlinearity and paves the way toward optical memory for all-optical signal processing and quantum information.

A Review on Materials and Methods for the Fabrication of Microcavity Laser

Optical microcavities are resonators that have at least one dimension on the order of a single optical wavelength. These structures enable one to control the optical emission properties of materials placed inside them. One of their most dramatic potential features is threshold-less lasing,unlike the conventional lasers. This is possible due to 2D monolayers, Heterostructures, Hybrid materials which are used as active layers for polariton-exciton strong coupling. In this review paper, a different method of Microcavity laser fabrication is reviewed, where a different type of active materials is utilized to improve the laser efficiency. Materials such as WS2, MoS2, WSe2 and MoSe2are used due to their strong exciton binding energy. These use high reflecting DBR mirrors fabricated using oxides of a higher refractive index such as SiO2, NbO2, HfO2/Al2O3, SiO2/Ta2O5 and SiO2/TiO2. In this way, the controlled spontaneous emission is expected to play a vital role in a new generation of optical devices and can have a wide range of applications in Optics, Quantum computing, high-speed signal transmission, etc.

Liquid Crystal Biosensors: Principles, Structure and Applications.

Liquid crystals (LCs) have been widely used as sensitive elements to construct LC biosensors based on the principle that specific bonding events between biomolecules can affect the orientation of LC molecules. On the basis of the sensing interface of LC molecules, LC biosensors can be classified into three types: LC–solid interface sensing platforms, LC–aqueous interface sensing platforms, and LC–droplet interface sensing platforms. In addition, as a signal amplification method, the combination of LCs and whispering gallery mode (WGM) optical microcavities can provide higher detection sensitivity due to the extremely high quality factor and the small mode volume of the WGM optical microcavity, which enhances the interaction between the light field and biotargets. In this review, we present an overview of the basic principles, the structure, and the applications of LC biosensors. We discuss the important properties of LC and the principle of LC biosensors. The different geometries of LCs in the biosensing systems as well as their applications in the biological detection are then described. The fabrication and the application of the LC-based WGM microcavity optofluidic sensor in the biological detection are also introduced. Finally, challenges and potential research opportunities in the development of LC-based biosensors are discussed.

Cavity-mediated electron-photon pairs.

Quantum information, communication, and sensing rely on the generation and control of quantum correlations in complementary degrees of freedom. Free electrons coupled to photonics promise novel hybrid quantum technologies, although single-particle correlations and entanglement have yet to be shown. In this work, we demonstrate the preparation of electron-photon pair states using the phase-matched interaction of free electrons with the evanescent vacuum field of a photonic chip-based optical microresonator. Spontaneous inelastic scattering produces intracavity photons coincident with energy-shifted electrons, which we employ for noise-suppressed optical mode imaging. This parametric pair-state preparation will underpin the future development of free-electron quantum optics, providing a route to quantum-enhanced imaging, electron-photon entanglement, and heralded single-electron and Fock-state photon sources.

Performance analysis of all optical-based quantum internet circuits

A Quantum dot implanted within a double-sided optical microcavity is considered and investigated as a critical component for all optical-based quantum internets. Due to the duality as the photonic quantum transistor and gate, the QD cavity system repsents a sturdy base for the future photonic quantum network. With the help of the analytical investigation and review presented in this paper, a quantum dot cavity unit can be developed for implementing deterministic quantum gates and transistors. The maximum fidelity observed for quantum diode, router, and storage is 95.24, 62.06, and 90.42%without considering a noisy environment, respectively, and 62.12, 60.36, and 43.66% under a noisy environment, respectively. Fidelity is also calculated with varying coupling conditions (strong and weak coupling), and optimized cavity parameters are calculated.

Progress and challenges on 3D tubular structures and devices of 2D materials

Due to their unique structures and properties, emerging two-dimensional (2D) materials have been at the frontier of research in, e.g., materials science, physics, and engineering. Three-dimensional (3D) tubular geometry enables 2D materials unparalleled advantages for various applications, for example, wide-angle infrared photodetectors, extremely sensitive molecular sensors, and memory with high density. Furthermore, 3D tubular structures offer a promising integration platform into chips with a broad range of materials, especially 2D materials. In this Perspective, we highlight state-of-the-art methods to assemble/manufacture 2D materials into 3D tubular structures/devices via self-rolled-up or template methods. These tubular 3D devices inspire unique physical, chemical, and mechanical properties for optical microcavity, photodetector, on-chip electronics, and bubble-propelled microengines. On-chip manufacture of 3D tubular structures/devices provides great opportunity and challenge for 2D materials for More than Moore applications such as unconventional electronics, smart sensors, and miniaturized robots.

Top-Emitting Active-Matrix Quantum Dot Light-Emitting Diode Array with Optical Microcavity for Micro QLED Display.

An electroluminescent quantum-dot light-emitting diode (QLED) device and a micro QLED device array with a top-emitting structure were demonstrated in this study. The QLED device was fabricated in the normal structure of [ITO/Ag/ITO anode]/PEDOT:PSS/PVK/QDs/[ZnO nanoparticles]/Ag/MoO3, in which the semi-transparent MoO3-capped Ag cathode and the reflective ITO/metal/ITO (IMI) anode were designed to form an optical microcavity. Compared with conventional bottom-emitting QLED, the microcavity-based top-emitting QLED possessed enhanced optical properties, e.g., ~500% luminance, ~300% current efficiency, and a narrower bandwidth. A 1.49 inch micro QLED panel with 86,400 top-emitting QLED devices in two different sizes (17 × 78 μm2 and 74 × 40.5 μm2) on a low-temperature polysilicon (LTPS) backplane was also fabricated, demonstrating the top-emitting QLED with microcavity as a promising structure in future micro display applications.

Reshaping the Jaynes-Cummings ladder with Majorana bound states

We study the optical properties of a hybrid device composed by a quantum dot (QD) resonantly coupled to a photonic mode of an optical microcavity and a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. In the regime of strong light-matter coupling, it is demonstrated that the leakage of the Majorana mode into the QD opens new optical transitions between polaritonic states formed due to hybridisation of material excitation with cavity photons, which leads to the reshaping of the Jaynes-Cummings ladder and can lead to the formation of a robust single-peak at cavity eigenfrequency in the emission spectrum. Moreover, weak satellite peaks in the low and high frequency regions are revealed for the distinct cases of highly isolated MBSs, overlapped MBSs and MBSs not well localized at the nanowire ends.

Broadband Manipulation of Stokes Raman Frequency Combs Via Mode Division Multiplexing in Optical Microcavities

We theoretically and experimentally investigate broadband manipulation of Stokes frequency comb generation in a silica microbottle resonator. We realize selective excitation of spectrally trapped Stokes combs belonging to distinct transverse mode families and a spectral tuning range up to ∼14.3 nm via coupling engineering by exciting distinct axial mode families with appropriate quality factors ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> s). Moreover, radial mode number selection, microcavity diameter control, or injection power adjustment also enables us to shift the Stokes comb wavelength. The tuning bandwidth can be extended to hundreds of nanometers by theoretical prediction using the bottle modal analysis and Coupled Lugiato Lefever (LL) equations simulation. We also show that multiple regimes in two-dimensional (2D) patterns can be selectively triggered depending on the cavity detuning, including Kerr frequency comb, single-frequency Raman lasing, multimode Raman lasing, and soliton crystal-like state. Our approach provides a scheme for greatly extending the wavelength tuning range of compact Raman laser devices with high performance.

Optical microcavity based on a single ZnO microwire grown on Si(111) substrate by catalyst-free mist chemical vapor deposition

Optical microcavity based on a single ZnO microwire grown on Si(111) substrate by catalyst-free mist chemical vapor deposition

Embedding Optical Microcavities in Nanoporous SiO2 Film via Infill Inkjet Printing

Embedding Optical Microcavities in Nanoporous SiO2 Film Since the transparent SiO2 nanoparticle aggregate film with a nanoporous network allows a polymer or dye solution to penetrate well, it is possible to embed a micro-optical structure such as a WGM microcavity laser inside the film by a printing method such as inkjet. In other words, it can realize an optical integrated circuit as if “drawing on paper”. More information can be found in article number 2200018 by Hiroaki Yoshioka and co-workers.

Plasmonic Nanoparticles Embedded in Nanomembrane Microcavity for Flexible Optical Tuning

AbstractThe combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane‐formed whispering‐gallery‐mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions.

Metal Halide Perovskites toward Electrically Pumped Lasers

AbstractThe rapid development of lasers since their launch has given a new lease to traditional optical technology and immensely boosted the development of natural science. Benefiting from the salient light absorption and light emission traits, perovskite lasers show incalculable prospects in applications of optical storage, optical interconnects, high‐quality displays, on‐chip photonic communications, etc. For perovskite lasers, device structure and working principle rather than just material property are also profound, especially for the realization and assessment of electrically pumped lasers, which is the prerequisite for the ultimate practical application of perovskite lasers. With this in mind, the key characteristic parameters of possible future electrically pumped lasers are discussed herein, and a systematic review of perovskite lasers is presented in a sequential order of development. To begin, the components of lasers are introduced in detail, with an emphasis on optical microcavities and diverse proposed working mechanisms, followed by introductions of representative advances in pulsed optically pumped perovskite lasers with various lasing modes, as well as state‐of‐the‐art developments in lasing phenomenon under continuous‐wave optical pumping. Finally, the challenges and fruitful progress toward electrically pumped perovskite lasers are discussed emphatically. It is hoped that this review will promote the realization of perovskite electrically pumped lasers and commercialization of perovskite lasers.

Classification of multiple arbitrary-order non-Hermitian singularities

We investigate the classification of Riemann surface topology generated by multiple arbitrary-order exceptional points of quasistationary states based on the permutation group. Our studies reveal all possible product permutations of holonomy matrices that describe a stroboscopic encircling of second-order exceptional points. The permutations turn out to be categorized into a finite number of classes according to the topological structures of the Riemann surfaces. Our results are verified by an effective non-Hermitian Hamiltonian founded on generic Jordan forms and then examined in physical systems of desymmetrized optical microcavities.