Optical Microcavities Research Articles

Ray Engineering from Chaos to Order in 2D Optical Cavities

AbstractChaos, namely exponential sensitivity to initial conditions, is generally considered a nuisance, inasmuch as it prevents long‐term predictions in physical systems. Here, an easily accessible approach to undo deterministic chaos and tailor ray trajectories in arbitrary 2D optical billiards by introducing spatially varying refractive index therein is presented. A new refractive index landscape is obtained by a conformal mapping, which makes the trajectories of the chaotic billiard fully predictable and the billiard fully integrable. Moreover, trajectory rectification can be pushed a step further by relating chaotic billiards with non‐Euclidean geometries. Two examples are illustrated by projecting billiards built on a sphere as well as the deformed spacetime outside a Schwarzschild black hole, which respectively lead to all periodic orbits and spiraling trajectories remaining away from the boundaries of the transformed 2D billiards/cavities. An implementation of this method is proposed, which enables real‐time control of chaos and can further contribute to a wealth of potential applications in the domain of optical microcavities.

Photon amplification and cavity-polariton-like generation in metallic nanoshells localized in optical cavity.

In this paper, I provide nanoshell as a new candidate to achieve the lasing and cavity-polariton-like. Owing to the energy levels in hybridized plasmon modes of nanoshell, I combine the two-level nature of dark and bright plasmon modes of nanoshell with plasmon enhancement of optical second-order nonlinear in metal surface to achieve the lasing of photon, especially under the condition of no population inversion. This provide a new idea to realize nanolaser. Furthermore, using the dipole-dipole interaction between naoshells, the one dimensional array of nanoshells can form new lattice plasmon polaritons similar to exciton-polariton in optical microcavity. Because the nanoshells are much easier to control compared with atoms, the nanoshells arrays (1D and 2D) are good platforms to mimic atomic arrays interacting with cavity photons. This has some potential value in quantum optics of plasmon.

Thermal Gradient Induced Transparency and Absorption in a Microcavity (Laser Photonics Rev. 17(2)/2023)

Optical Microcavities In article number 2200644, Lei Shi and colleagues propose and demonstrate thermal gradient induced transparency (TGIT) and absorption (TGIA) effects in a single functionalized microcavity. This novel platform can be used as a probe to realize a direct temperature readout from the transmission spectrum via multiple TGIT/TGIA-based photonic barcodes with a high detection resolution of 9 × 10−4 °C.

Analysis of Fast Fluorescence Kinetics of a Single Cyanobacterium Trapped in an Optical Microcavity.

Photosynthesis is one the most important biological processes on earth, producing life-giving oxygen, and is the basis for a large variety of plant products. Measurable properties of photosynthesis provide information about its biophysical state, and in turn, the physiological conditions of a photoautotrophic organism. For instance, the chlorophyll fluorescence intensity of an intact photosystem is not constant as in the case of a single fluorescent dye in solution but shows temporal changes related to the quantum yield of the photosystem. Commercial photosystem analyzers already use the fluorescence kinetics characteristics of photosystems to infer the viability of organisms under investigation. Here, we provide a novel approach based on an optical Fabry-Pérot microcavity that enables the readout of photosynthetic properties and activity for an individual cyanobacterium. This approach offers a completely new dimension of information, which would normally be lost due to averaging in ensemble measurements obtained from a large population of bacteria.

Universality and beyond in Optical Microcavity Billiards with Source-Induced Dynamics

Optical microcavity billiards are a paradigm of a mesoscopic model system for quantum chaos. We demonstrate the action and origin of ray-wave correspondence in real and phase space using far-field emission characteristics and Husimi functions. Whereas universality induced by the invariant-measure dominated far-field emission is known to be a feature shaping the properties of many lasing optical microcavities, the situation changes in the presence of sources that we discuss here. We investigate the source-induced dynamics and the resulting limits of universality while we find ray-picture results to remain a useful tool in order to understand the wave behaviour of optical microcavities with sources. We demonstrate the source-induced dynamics in phase space from the source ignition until a stationary regime is reached comparing results from ray, ray-with-phase, and wave simulations and explore ray-wave correspondence.

Versatile Tunable Microresonator for the Light-Matter Interaction Studying in the Strong-Coupling Mode

The interaction between an ensemble of molecules and an electromagnetic field in a highly limited volume makes it possible to control the properties of a substance and, therefore, is an exceptionally promising area of research. The most common way to achieve weak or strong light-matter coupling is to place an ensemble of molecules in a micron-sized resonator. In such a system,the interaction of light with matter appears in the form of a change in the spectral response of the system, which depends on the strength of the coupling between the ensemble of molecules and the modes of the resonator. Currently, there is no general and user-friendly approach that allows studying a lot of different samples in a wide optical range using the same resonator setup. The present paper describes the design of a device that makes it possible to overcome this disadvantage, speed up and facilitate the study of the light-matter interaction, and also obtain weak and strong light-matter coupling modes for a large number of samples in the UV, visible, and IR regions of the optical spectrum. The device developed here is based on the tunable unstable λ/2 Fabry-Perot microresonator, consisting of flat and convex mirrors, which satisfy the condition of plane-parallelism at least at one point of the curved mirror and can significantly reduce the mode volume. The device was used to study the effect of the strong-coupling regime on the fluorescent properties of the Rhodamine 6G (R6G) dye embedded in a boron nitride nanoparticles matrix. It was found that the use of boron nitride (h-BN) as a carrier matrix has an orienting effect on the dye molecules, that results in an increase of the light-matter coupling strength at a lower resonator mode energy required. Keywords: microspectroscopy, optical microresonator, strong coupling, boron nitride.

Digital holography with microcombs

Optical microresonators are attractive comb sources due to their small form factor and stable broad optical spectra. We report on the first demonstration of microcomb-based digital holography. The large line spacing of microcombs promises an unprecedented combination of precision, fast update rate and ambiguity ranges on the scale of a few mm. Using a pulse-driven lithium niobate microcomb of 100 GHz line spacing and a scanning Michelson interferometer, we generate spectral hypercubes of holograms. Our first experimental results show that the amplitude and phase information of the object can be recovered for more than 100 comb lines.

Solvent atmosphere-assisted crystallization of perovskites for room-temperature continuous-wave amplified spontaneous emission

Solvent atmosphere-assisted crystallization of perovskites exhibits good amplified spontaneous emission (ASE) performance. Combined with an optical microcavity, a continuous-wave optically pumped ASE is realized with a low threshold of 3.8 W cm−2.

Fabry-Pérot Optical Microcavity and Its Application

Fabry-Pérot Optical Microcavity and Its Application

Strong light-matter coupling in pentacene thin films on plasmonic arrays.

Utilizing strong light-matter coupling is an elegant and powerful way to modify the energy landscapes of excited states of organic semiconductors. Consequently, the chemical and photophysical properties of these organic semiconductors can be influenced without the need of chemical modification but simply by implementing them in optical microcavities. This has so far mostly been shown in Fabry-Pérot cavities and with organic single crystals or diluted molecules in a host matrix. Here, we demonstrate strong, simultaneous coupling of the two Davydov transitions in polycrystalline pentacene thin films to surface lattice resonances supported by open cavities made of silver nanoparticle arrays. Such thin films are more easily fabricated and, together with the open architecture, more suitable for device applications.

Experimental realization of strong coupling between a cold atomic ensemble and an optical fiber microcavity

Experimental realization of strong coupling between a cold atomic ensemble and an optical fiber microcavity

The nonlinear effects and applications of gain doped whispering-gallery mode cavities

Whispering-gallery mode (WGM) cavities formed by dielectric structures have attracted intensive interest in various fields. The high-quality factor and smaller mode volume associated with the optical modes have inspired experiments in nonlinear optics, nanophotonics, and quantum information science. Moreover, they are also used in optical biosensors and other significant applications. To further reduce the material loss of the resonator, optical gain materials, such as erbium and ytterbium, are doped into the dielectric structure to increase the nonlinear effect and enhance the interaction between light and matter. Here in this review, we outline the most recent advancements in gain-doped optical WGM microcavities. Moreover, we introduce the dynamics of the gain in WGM resonators, the integration of gain media into WGM microcavities with various shapes, and the fabrication and applications of the gain microcavities. Also, the applications of the gain cavity based on the whispering-gallery mode have been introduced, e.g., ultra-sensitive sensors, low-threshold lasers, and high-performance optical systems.

Kerr Frequency Comb and Stimulated Raman Comb Covering S+C+L+U Band Based on a Packaged Silica Spherical Microcavity

Optical microresonators supported whispering gallery modes (WGMs) are one of the most cost-effective platforms for optical frequency comb generated due to their advantages of ultra-high quality ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> ) factor and ultra-low mode volume. In this paper, we report a portable and robust packaged silica spherical microcavity by melting the end of a standard single-mode fiber with ultra-high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${10}^8$</tex-math></inline-formula> , and theoretically and experimentally demonstrate a broadband optical frequency comb (OFC) generation including Kerr OFC and stimulated Raman comb. Kerr OFCs are separated by one, two, eight and twelve free spectral ranges corresponding to 1.4, 2.8, 11.2, and 16.8 nm, respectively. The transition between Kerr OFC and stimulated Raman comb is achieved by changing the pump laser power and the detuning frequency resulting from gain competition between modulation instability and Raman gain. Benefitting from the dispersion control and ultra-high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor persistence in our packaged microcavity, OFC can be adjusted continuously covering from S-band to C-band, L-band and U-band. We also explain these results by numerical simulations using a model framework combined with the Lugiato-Lefever equation and Raman response function.

Generation, development, and application of microcombs

Optical frequency comb (OFC) has coherently bridged the gap between light and microwave. Its advent has brought revolutionary progress to the accurate measurements of optical frequency and time, and profoundly promoted the technological development of technology of the contemporary world. The earliest optical frequency combs are generated from mode-locked laser systems. However, optical frequency combs based on mode-locked lasers have typically been limited to laboratory applications, due to their complexity, large size, and high cost. In recent years, a new type of optical frequency comb has emerged to address these problems. It is excited by continuous-wave laser coupling into a high-quality optical microresonator, generating equidistant sidebands in the frequency domain through four-wave mixing, and achieving mode locking in the time domain by using nonlinear effects to balance dispersion. This novel optical frequency comb is named "microcombs". Compared with traditional optical frequency combs, microcombs offer advantages such as compact size, integrability, low power consumption, and a wide repetition frequency range. Their occurrence marks the era of the generation of optical frequency combs towards chip-scale size and has aroused increasing attention from the scientific and industrial communities. This paper is ended by summarizing the current challenges faced by microcombs and giving a prospective outlook on their future development.

Design and Analysis of Spectral Signal Acquisition System Based on Ultra-High Q Factor Optical Microcavity

Design and Analysis of Spectral Signal Acquisition System Based on Ultra-High Q Factor Optical Microcavity

Optofluidic lasers and their applications in biochemical sensing.

Optofluidic laser (OFL) technology, as an emerging technology combining microfluidics and laser technology, offers many unique advantages in sensing applications and has become a research hotspot for highly-sensitive intracavity biochemical analysis. Biochemical sensors based on OFLs can detect changes in biochemical parameters by using significant changes in laser output characteristics, so as to achieve high detection sensitivity. Here, we provide an overview of OFLs with a focus on their constructions, the design of OFL-based biochemical sensors, and their applications in biochemical analysis. Firstly, the three elements of an OFL, including the optical microcavity, gain medium, and pump source, are described systematically. After explaining the basic principles and characterization of OFLs for biochemical sensing, the current research progress of OFL-based biochemical sensors is summarized and analyzed according to the combination of OFLs with different assay techniques. This is followed by a discussion of the research on OFLs at the level of biological macromolecules, cells, and tissues. Finally, in view of the applications of OFLs in the field of biochemical sensing, the current challenges and future development directions are briefly discussed.

Room-Temperature Excitonic Nanolaser Array with Directly Grown Monolayer WS2

Two-dimensional (2D) transition-metal chalcogenides (TMDCs) with strong excitonic emission are ideal candidates for small-volume gain materials in nanolasers, which can be realized by integrating 2D TMDCs with optical microcavities. However, at present, the integration is usually realized by the transfer method, which is not suitable for large-scale production, and the quality factor of the microcavity usually drops sharply in the process of transfer. Therefore, scalable fabrication of nanolasers remains an urgent issue to be solved. In this paper, by embedding continuous monolayer WS2 between silicon nitride (Si3N4) microdisks and Al2O3, we demonstrated the room-temperature transfer-free excitonic nanolaser array. Lasing at room temperature is achieved with the help of the high-quality-factor Si3N4 microdisks and the physical vapor deposition method for growing 2D gain material directly. This work provides a practical solution for large-scale and low-cost TMDC-based nanolaser arrays in the integrated optical communication systems.

Soliton-comb generation in ring-shaped optical Kerr microresonators under thermal effects

Soliton combs are nonlinear wavetrains resulting from entanglements of localized waves which may be pulse or kink solitons, forming periodic structures called soliton crystals. In this work we examine the possible generation of soliton-comb structures in an optical Kerr microresonator in the ring configuration, considering the physical context where the laser stores heat in the ring cavity leading to sizable thermo-optical effects. To proceed with the study we consider an existing model proposed for this physical context, in which the optical field contribution to time evolution of the heat in the microresonator is described by the its average power. With help of appropriate variable changes the model is formulated in terms of a set of coupled first-order nonlinear ordinary differential equations, which are solved numerically paying particular attention to the impact of thermal effects on characteristic parameters of the soliton crystal structures, and also on the profile of time evolution of the temperature in the microresonator cavity. Simulations show that for the specific model considered, thermal effects do not oppose the formation of soliton crystals in the optical Kerr microresonator undergoing thermo-optical effects. Nevertheless the induced thermal detuning is likely to cause the average amplitude of the soliton crystal to increase or decrease, depending on variations of thermal coefficients in the heat equation.

Feedback and compensation scheme to suppress the thermal effects from a dipole trap beam for the optical fiber microcavity.

Cavity quantum electrodynamics (cavity QED) with neutral atoms is a promising platform for quantum information processing and optical fiber Fabry-Pérot microcavity with small mode volume is an important integrant for the large light-matter coupling strength. To transport cold atoms to the microcavity, a high-power optical dipole trap (ODT) beam perpendicular to the cavity axis is commonly used. However, the overlap between the ODT beam and the cavity mirrors causes thermal effects inducing a large cavity shift at the locking wavelength and a differential cavity shift at the probe wavelength which disturbs the cavity resonance. Here, we develop a feedback and compensation scheme to maintain the optical fiber microcavity resonant with the lasers at the locking and probe wavelengths simultaneously. The large cavity shift of 210 times the cavity linewidth, which makes the conventional PID scheme ineffective can be suppressed actively by a PIID feedback scheme with an additional I parameter. Differential cavity shift at the probe wavelength can be understood from the photothermal refraction and thermal expansion effects on the mirror coatings and be passively compensated by changing the frequency of the locking laser. A further normal-mode splitting measurement demonstrates the strong coupling between 85Rb atoms and cavity mode after the thermal effects are suppressed, which also confirms successful delivery and trapping of atoms into the optical cavity. This scheme can solve the thermal effects of the high-power ODT beam and will be helpful to cavity QED experimental research.

Ultrasound detection using a thermal-assisted microcavity Raman laser

Optical microcavities have emerged as promising platforms for ultrasound detection. One of the main tendencies in recent studies is to develop high-Q microresonators for ultrasensitive ultrasound detection, while the nonlinear optical effects become significant but are generally neglected. Here, we propose a thermal-assisted microcavity Raman laser for ultrasound detection. Acoustic waves modulate the resonant frequency of the cavity mode, altering the coupled efficiency of a fixed-wavelength input laser, and therefore the output Raman power. Experimentally, the noise equivalent pressure reaches as low as 8.1 Pa at 120 kHz in air. Besides, it is found that the thermal effect involved in high-Q microcavities can compensate for the low-frequency noises, while without degrading their sensitivity to high-frequency acoustic waves above hundreds of kilohertz. Therefore, it enables long-standing stability during the measurements due to the natural resistance to laser frequency drifts and environmental disturbances, which holds great potential in practical applications of ultrasound sensing and imaging.