High-quality Whispering Gallery Modes Research Articles

Controlled on-chip fabrication of large-scale perovskite single crystal arrays for high-performance laser and photodetector integration

Metal halide perovskites possess intriguing optoelectronic properties, however, the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices. Here, we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas. This method enables precise control over the crystal arrays, including different array shapes and resolutions with less than 10%-pixel position variation, tunable pixel dimensions from 2 to 8 μm as well as the in-plane rotation of each pixel. The crystal pixel could serve as a high-quality whispering gallery mode (WGM) microcavity with a quality factor of 2915 and a threshold of 4.14 μJ cm−2. Through directly on-chip fabrication on the patterned electrodes, a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns, indicating the potential application in the integrated systems of this method.

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

Wavelength tunable single-mode lasing from cesium lead halide perovskite microwires

Cesium lead halide perovskites have shown great potential applications in photoelectric devices because of their high quantum efficiency, good stability, and tunable bandgap. Herein, we prepared CsPbBr3 microwires with a high crystal quality, smooth surface, and rectangular cross section via the solution method. The as-prepared microwires presented a high quality whispering gallery mode lasing with a low threshold of 9.1 μJ cm−2 and a high quality factor of ∼3000. Furthermore, we obtained the alloys of CsPbClxBr3−x (0 < x < 2) microwires through the gas-phase anion exchange method and realized the wavelength tunable single-mode lasing emission ranging from ∼546.8 nm to ∼468.0 nm. This work will expand the practical application of lead halide perovskites in spectrograph, optical communication, and in-chip photoelectric devices.

Wavelength tuning of the spirally drawn whispering gallery mode microfiber lasers and the perspectives for sensing applications.

Facile and cost-efficient microcavities, as well as the tuning of the optical modes, especially for the application of top-grade optical devices, have been emerging as attractive research fields. In this work, controllable fabrication of the microfiber laser arrays in polymer matrix is achieved by employing the advanced spiral drawing technique. Besides the high-quality whispering gallery mode (WGM) lasing, wavelength tuning is also realized by applying external forces on the polymer matrix, which induce slightly enlarged cavity sizes. Furthermore, the perspectives of utilizing the microfiber arrays as force and strain sensors are discussed and demonstrated.

Ringing phenomenon based whispering-gallery-mode sensing.

Highly sensitive sensing is one of the most important applications of whispering-gallery-mode (WGM) microresonators, which is usually accomplished through a tunable continuous-wave laser sweeping over a whispering-gallery mode with the help of a fiber taper in a relative slow speed. It is known that if a tunable continuous-wave laser sweeps over a high quality whispering-gallery mode in a fast speed, a ringing phenomenon will be observed. The ringing phenomenon in WGM microresonators is mainly used to measure the Q factors and mode-coupling strengths. Here we experimentally demonstrate that the WGM sensing can be achieved based on the ringing phenomenon. This kind of sensing is accomplished in a much shorter time and is immune to the noise caused by the laser wavelength drift.

Quantum Light from a Whispering-Gallery-Mode Disk Resonator

Optical parametric down-conversion has proven to be a valuable source of nonclassical light. The process is inherently able to produce twin-beam correlations along with individual intensity squeezing of either parametric beam, when pumped far above threshold. Here, we present for the first time the direct observation of intensity squeezing of -1.2 dB of each of the individual parametric beams in parametric down-conversion by use of a high quality whispering-gallery-mode disk resonator. In addition, we observed twin-beam quantum correlations of -2.7 dB with this cavity. Such resonators feature strong optical confinement and offer tunable coupling to an external optical field. This work exemplifies the potential of crystalline whispering-gallery-mode resonators for the generation of quantum light. The simplicity of this device makes the application of quantum light in various fields highly feasible.

Self-assembled quantum dots in a liquid-crystal-tunable microdisk resonator

GaAs-based semiconductor microdisks with high quality whispering gallery modes ( Q > 4000 ) have been fabricated. A layer of self-organized InAs quantum dots (QDs) served as a light source to feed the optical modes at room temperature. In order to achieve frequency tuning of the optical modes, the microdisk devices have been immersed in 4-cyano-4 ′ -pentylbiphenyl (5CB), a liquid crystal (LC) with a nematic phase below the clearing temperature of T C ≈ 34 ∘ C . We have studied the device performance in the temperature range of T = 20 – 50 ∘ C , in order to investigate the influence of the nematic–isotropic phase transition on the optical modes. Moreover, we have applied an AC electric field to the device, which leads in the nematic phase to a reorientation of the anisotropic dielectric tensor of the liquid crystal. This electrical anisotropy can be used to achieve electrical tunability of the optical modes. Using the finite-difference time domain (FDTD) technique with an anisotropic material model, we are able to describe the influence of the liquid crystal qualitatively.

Optical Properties of Mesoscopic Systems of Coupled Microspheres

Two mechanisms of optical coupling between spherical cavities, tight-binding be- tween their whispering gallery modes and focusing produced by periodically coupled microlenses, are directly observed using spatially resolved scattering spectroscopy and imaging. The results can be used for developing device concepts of lasers, optical fllters, microspectrometers and sen- sors based on mesoscopic systems of coupled microspheres. DOI: 10.2529/PIERS060908001922 In this paper we consider structures formed by coupled spherical cavities which can be regarded as mesoscopic systems due to the fact that the size of their building blocks (spheres) is comparable to the characteristic wavelength. In contrast to metamaterials or photonic crystals conceptualized through the process of homogenization, the optical phenomena in such mesoscopic systems are essentially based on the properties of the constituting cavities. These include their ultra high quality whispering gallery mode (WGM) resonances (1) and their ability to focus plane waves into \nanoscale photonic jets (2) at the shadow-side. These properties lead to two difierent mechanisms of optical transport between the cavities: (i) tight-binding between WGMs, (ii) propagation in a series of periodically coupled microlenses. These mechanisms are directly studied in the present work. 1. TIGHT-BINDING BETWEEN WGMS Previously we observed WGM-related propagation efiects (3) in one-dimensional (1D) chains of slightly disordered spheres using evanescently coupled dye-doped spherical cavities pumped above the lasing threshold for WGMs. In the present work we integrated spherical cavities into 3D closed packed structures with the thickness varying from one monolayer up to » 50 monolayers. The samples were obtained by self-assembly of spheres (with sizes in 2-10 micron range with standard 3% size dispersion) directed by hydro-dynamic ∞ow in a specially designed cuvette placed in ultrasonic bath. The spheres were dye-doped and locally excited to create a built-in source of whispering gallery modes (WGMs). In the scattering spectra of such samples we observed fringes due to light propagation via coupled WGMs, as illustrated in Fig. 1. The study of pump dependence of scattering spectra indicated that above WGM lasing threshold the emission is provided in localized modes formed by multiple spheres. This is conflrmed by observation of double peak structures, the spectral signature of strong coupling regime between multiple cavities. Although size disorder plays a negative role in the e-ciency of such transport, we show that due to existence of multiple paths for photons the optical transport can be very e-cient. The study of thickness dependence of scattering spectra indicates that attenuation length of light in such 3D samples exceeds 50m. The results show that the optical transport in such systems is provided along particular conflgurations of cavities according to a principle of minimization of the total WGM detuning.