An electrically driven whispering gallery polariton microlaser

High-quality integratable microlasers from scalable perovskite heterostructures enabled by solution-phase processing

High-performance transferable and integratable microlasers hold great promise to construct the integrated photonics and optoelectronics. However, the qualified candidates are still being pursued. Herein, a mass-production of low-threshold and wavelength-tunable microlasers that is readily integratable with the optical fiber platform is realized by a two-step solution-phase approach. The demonstration is enabled by the formation of a novel semiconductor heterostructure from halide perovskites featuring the quasi-free-standing and highly emissive properties. Corroborated by the in-situ optical characterization, we reveal that the lateral perovskite heterostructures are constructed through a sequential reaction driven by the surface energy contrast. These perovskite heterostructures exhibit low-threshold and broadband tunable lasing action thanks to the efficient spatial light conversion nature and the facile composition tunability. Taking the merits together, the heterostructure microlasers can be the competitive applicants for photonic integration as demonstrated by the laser-on-fiber configuration.

Ultraviolet Exciton-Polariton Light-Emitting Diode in a ZnO Microwire Homojunction

Low-dimensional ZnO, possessing well-defined side facets and optical gain properties, has emerged as a promising material to develop ultraviolet coherent light sources. However, the realization of electrically driven ZnO homojunction luminescence and laser devices is still a challenge due to the absence of a reliable p-type ZnO. Herein, the sample of p-type ZnO microwires doped by Sb (ZnO:Sb MWs) was synthesized individually. Subsequently, the p-type conductivity was examined using a single-MW field-effect transistor. Upon optical pumping, a ZnO:Sb MW showing a regular hexagonal cross-section and smooth sidewall facets can feature as an optical microcavity, which is evidenced by the achievement of whispering-gallery-mode lasing. By combining an n-type ZnO layer, a single ZnO:Sb MW homojunction light-emitting diode (LED), which exhibited a typical ultraviolet emission at a wavelength of 379.0 nm and a line-width of approximately 23.5 nm, was constructed. We further illustrated that strong exciton-photon coupling can occur in the as-constructed p-ZnO:Sb MW/n-ZnO homojunction LED by researching spatially resolved electroluminescence spectra, contributing to the exciton-polariton effect. Particularly, varying the cross-sectional dimensions of ZnO:Sb wires can further modulate the exciton-photon coupling strengths. We anticipate that the results can provide an effective exemplification to realize reliable p-type ZnO and tremendously promote the development of low-dimensional ZnO homojunction optoelectronic devices.

Exciton-polariton light-emitting diode based on a single ZnO superlattice microwire heterojunction with performance enhanced by Rh nanostructures

One-dimensional (1D) wirelike superlattice micro/nanostructures have received considerable attention for potential applications due to their versatility and capability for modulating optical and electrical characteristics. In this study, 1D superlattice microwires (MWs), which are made of undoped ZnO and Ga-doped ZnO with periodic and alternating crystalline layers (ZnO/ZnO:Ga), were synthesized individually. Under optical excitation, a series of resonance peaks in the photoluminescence spectrum can be ascribed to polariton emission, which originates from the coupling interaction of the 1D photonic crystal and confined excitons along the wire direction. Using a p-type GaN layer as the hole transport layer, a kind of waveguide light source based on an individual ZnO/ZnO:Ga superlattice MW was proposed and constructed. By analysing the spatially resolved electroluminescence spectra, the observed multipeak was ascribed to exciton-polariton emission with a vacuum Rabi splitting of about 275 meV. Cladding with Rh nanostructures gives rise to appropriate ultraviolet plasmons, and the Rabi splitting energy of our device was enhanced up to 413 meV. The exciton-polariton properties were further examined using angle-resolved electroluminescence measurements. Therefore, individual superlattice MWs can act as optical microresonators to achieve photon-exciton coupling with a large Rabi splitting energy. The experimental results indicate that an individual ZnO/ZnO:Ga superlattice MW can be generally used in developing exciton-polariton luminescence/lasing light sources, particularly for constructing low-threshold/thresholdless lasers toward pragmatic applications.

Interface engineering enhanced near-infrared electroluminescence in an n-ZnO microwire/p-GaAs heterojunction

Interface engineering in the fabrication of low-dimensional optoelectronic devices has been highlighted in recent decades to enhance device characteristics such as reducing leakage current, optimizing charge transport, and modulating the energy-band structure. In this paper, we report a dielectric interface approach to realize one-dimensional (1D) wire near-infrared light-emitting devices with high brightness and enhanced emission efficiency. The light-emitting diode is composed of a zinc oxide microwire covered by a silver nanolayer (Ag@ZnO MW), magnesium oxide (MgO) buffer layer, and p-type gallium arsenide (GaAs) substrate. In the device structure, the insertion of a MgO dielectric layer in the n-ZnO MW/p-GaAs heterojunction can be used to modulate the device features, such as changing the charge transport properties, reducing the leakage current and engineering the band alignment. Furthermore, the cladding of the Ag nanolayer on the ZnO MW can optimize the junction interface quality, thus reducing the turn-on voltage and increasing the current injection and electroluminescence (EL) efficiency. The combination of MgO buffer layer and Ag nanolayer cladding can be utilized to achieve modulating the carrier recombination path, interfacial engineering of heterojunction with optimized band alignment and electronic structure in these carefully designed emission devices. Besides, the enhanced near-infrared EL and improved physical contact were also obtained. The study of current transport modulation and energy-band engineering proposes an original and efficient route for improving the device performances of 1D wire-type heterojunction light sources.

Electrically driven single microwire-based single-mode microlaser

Engineering the lasing-mode oscillations effectively within a laser cavity is a relatively updated attentive study and perplexing issue in the field of laser physics and applications. Herein, we report a realization of electrically driven single-mode microlaser, which is composed of gallium incorporated zinc oxide microwire (ZnO:Ga MW) with platinum nanoparticles (PtNPs, d ~ 130 nm) covering, a magnesium oxide (MgO) nanofilm, a Pt nanofilm, and a p-type GaN substrate. The laser cavity modes could resonate following the whispering-gallery mode (WGM) among the six side surfaces by total internal reflection, and the single-mode lasing wavelength is centered at 390.5 nm with a linewidth of about 0.18 nm. The cavity quality factor Q is evaluated to about 2169. In the laser structure, the usage of Pt and MgO buffer layers can be utilized to engineer the band alignment of ZnO:Ga/GaN heterojunction, optimize the p-n junction quality and increase the current injection. Thus, the well-designed device structure can seamlessly unite the electron-hole recombination region, the gain medium, and optical microresonator into the PtNPs@ZnO:Ga wire perfectly. Such a single MW microlaser is essentially single-mode regardless of the gain spectral bandwidth. To study the single-mode operation, PtNPs working as superabsorber can engineering the multimode lasing actions of ZnO:Ga MWs even if their dimensions are typically much larger than that of lasing wavelength. Our findings can provide a straightforward and effective scheme to develop single-mode microlaser devices based on one-dimensional wire semiconductors.

Two-round quasi-whispering gallery mode exciton polaritons with large Rabi splitting in a GaN microrod

We investigate the exciton polaritons and their corresponding optical modes in a hexagonal GaN microrod at room temperature. The dispersion curves are measured by the angle-resolved micro-photoluminescence spectrometer, and two types of exciton polaritons are identified with the help of the finite-difference time-domain simulation. By changing the pump position, the photon part of the exciton polaritons is found to switch between the quasi-whispering gallery modes and the two-round quasi-whispering gallery modes. The exciton polaritons formed by the latter are observed and distinguished for the first time, with a giant Rabi splitting as large as 2Ω = 230.3 meV.

The Deformation Behavior and Bending Emissions of ZnO Microwire Affected by Deformation-Induced Defects and Thermal Tunneling Effect

The realization of electrically pumped emitters at micro and nanoscale, especially with flexibility or special shapes is still a goal for prospective fundamental research and application. Herein, zinc oxide (ZnO) microwires were produced to investigate the luminescent properties affected by stress. To exploit the initial stress, room temperature in situ elastic bending stress was applied on the microwires by squeezing between the two approaching electrodes. A novel unrecoverable deformation phenomenon was observed by applying a large enough voltage, resulting in the formation of additional defects at bent regions. The electrical characteristics of the microwire changed with the applied bending deformation due to the introduction of defects by stress. When the injection current exceeded certain values, bright emission was observed at bent regions, ZnO microwires showed illumination at the bent region priority to straight region. The bent emission can be attributed to the effect of thermal tunneling electroluminescence appeared primarily at bent regions. The physical mechanism of the observed thermoluminescence phenomena was analyzed using theoretical simulations. The realization of electrically induced deformation and the related bending emissions in single microwires shows the possibility to fabricate special-shaped light sources and offer a method to develop photoelectronic devices.

An electrically driven single microribbon based near-infrared exciton–polariton light-emitting diode

An electrically driven exciton–polariton NIR-LED involving an n-ZnO:Ga microribbon/p-GaAs heterojunction was achieved. The Rabi splitting is measured to be 109 meV.