Submicrometer perovskite plasmonic lasers at room temperature

Plasmonic Hinge Modes in Metal-Coated Nanolasers

Plasmonic lasers have traditionally been built on flat metal substrates. Here, we introduce substrate-free plasmonic lasers created by coating semiconductor particles with an optically thin layer of noble metal. This architecture supports plasmonic "hinge" modes highly localized along the particle's edges and corners, exhibiting Purcell factors exceeding 100 and Q-factors of 15-20 near the plasmon resonance frequency. We demonstrate hinge-mode lasing in submicron CsPbBr3 perovskite cubes encapsulated with conformal 15-nm-thick gold shells. The lasing is achieved with 480-nm nanosecond pumping at 10 pJ/μm2 through the translucent gold layer, producing a line width of 0.6 at 538 nm. Their rapidly decaying evanescent fields outside the gold coating show distinct sensitivities to long- and short-range external perturbations. Our results suggest the potential of these novel laser modes for sensing and imaging applications.

Ultracompact and Uniform Nanoemitter Array Based on Periodic Scattering

As emerging gain materials, lead halide perovskites have drawn considerable attention in coherent light sources. With the development of patterning and integration techniques, a perovskite laser array has been realized by distributing perovskite microcrystals periodically. Nevertheless, the packing density is limited by the crystal size and the channel gap distance. More importantly, the lasing performance for individual laser units is quite random due to variation of size and crystal quality. Herein an ultracompact perovskite nanoemitter array with uniform emission has been demonstrated. Individual emitters are formed via scattering evanescent components from a shared Fabry-Perot laser, ensuring uniform lasing emission in a unit cell with a side length of 160 nm and lattice constant of 400 nm. And the periodic silicon scatterers do not deteriorate the lasing threshold dramatically. In addition, the surface emitting efficiency increased significantly. The direct integration of a densely packed nanoemitter array with a silicon platform promises high-throughput sensing and high-capacity optical interconnects.

Microstructure-Assisted Wafer-Scale Fabrication of Perovskite Microlaser Arrays

All inorganic lead halide perovskites exhibit fascinating optical and optoelectronic characteristics for on-chip lasing, but the lack of precise control of wafer-scale fabrication for perovskite microstructure arrays restricts their potential applications in on-chip-integrated devices. In this work, a microstructure-template assisted crystallization method is demonstrated via a designed chemical vapor deposition process, achieving the controllable fabrication of homogeneous perovskite micro-hemispheroid (PeMH) arrays spanning the entire surface area of a 4-inch wafer. Benefiting from the low-loss whispering gallery resonance and plasmon-enhanced light-matter interactions in well-confined hybrid cavities, this CsPbX3/Ag (X = Cl, Br) plasmonic microlasers exhibit quite low thresholds below 10 µJ cm-2. Interestingly, these thresholds can be efficiently modulated through the manipulation of plasmonic resonance and electromagnetic field mode in PeMHs owning various diameters. This strategy not only provides a valuable methodology for the large-scale fabrication of perovskite microstructures but also endorses the potential of all-inorganic perovskite nanostructures as promising candidates for on-chip-integrated light sources.

Metal-Halide Perovskite Lasers: Cavity Formation and Emission Characteristics

Hybrid metal-halide perovskites (MHPs) have shown remarkable optoelectronic properties as well as facile and cost-effective processability. With the success of MHP solar cells and light-emitting diodes, MHPs have also exhibited great potential as gain media for on-chip lasers. However, to date, stable operation of optically pumped MHP lasers and electrically driven MHP lasers-an essential requirement for MHP laser's insertion into chip-scale photonic integrated circuits-is not yet demonstrated. The main obstacles include the instability of MHPs in the atmosphere, rudimentary MHP laser cavity patterning methods, and insufficient understanding of emission mechanisms in MHP materials and cavities. This review aims to provide a detailed overview of different strategies to improve the intrinsic properties of MHPs in the atmosphere and to establish an optimal MHP cavity patterning method. In addition, this review discusses different emission mechanisms in MHP materials and cavities and how to distinguish them.

Hyperspectral confocal imaging for high-throughput readout and analysis of bio-integrated microlasers

Integrating micro- and nanolasers into live cells, tissue cultures and small animals is an emerging and rapidly evolving technique that offers noninvasive interrogation and labeling with unprecedented information density. The bright and distinct spectra of such lasers make this approach particularly attractive for high-throughput applications requiring single-cell specificity, such as multiplexed cell tracking and intracellular biosensing. The implementation of these applications requires high-resolution, high-speed spectral readout and advanced analysis routines, which leads to unique technical challenges. Here, we present a modular approach consisting of two separate procedures. The first procedure instructs users on how to efficiently integrate different types of lasers into living cells, and the second procedure presents a workflow for obtaining intracellular lasing spectra with high spectral resolution and up to 125-kHz readout rate and starts from the construction of a custom hyperspectral confocal microscope. We provide guidance on running hyperspectral imaging routines for various experimental designs and recommend specific workflows for processing the resulting large data sets along with an open-source Python library of functions covering the analysis pipeline. We illustrate three applications including the rapid, large-volume mapping of absolute refractive index by using polystyrene microbead lasers, the intracellular sensing of cardiac contractility with polystyrene microbead lasers and long-term cell tracking by using semiconductor nanodisk lasers. Our sample preparation and imaging procedures require 2 days, and setting up the hyperspectral confocal microscope for microlaser characterization requires <2 weeks to complete for users with limited experience in optical and software engineering.

High-Q lasing via all-dielectric Bloch-surface-wave platform

Controlling the propagation and emission of light via Bloch surface waves (BSWs) has held promise in the field of on-chip nanophotonics. BSW-based optical devices are being widely investigated to develop on-chip integration systems. However, a coherent light source that is based on the stimulated emission of a BSW mode has yet to be developed. Here, we demonstrate lasers based on a guided BSW mode sustained by a gain-medium guiding structure microfabricated on the top of a BSW platform. A long-range propagation length of the BSW mode and a high-quality lasing emission of the BSW mode are achieved. The BSW lasers possess a lasing threshold of 6.7 μJ/mm2 and a very narrow linewidth reaching a full width at half maximum as small as 0.019 nm. Moreover, the proposed lasing scheme exhibits high sensitivity to environmental changes suggesting the applicability of the proposed BSW lasers in ultra-sensitive devices.

Ultrasmall InGa(As)P Dielectric and Plasmonic Nanolasers

Nanolasers have great potential for both on-chip light sources and optical barcoding particles. We demonstrate ultrasmall InGaP and InGaAsP disk lasers with diameters down to 360 nm (198 nm in height) in the red spectral range. Optically pumped, room-temperature, single-mode lasing was achieved from both disk-on-pillar and isolated particles. When isolated disks were placed on gold, plasmon polariton lasing was obtained with Purcell-enhanced stimulated emission. UV lithography and plasma ashing enabled wafer-scale fabrication of nanodisks with an intended random size variation. Silica-coated nanodisk particles generated stable subnanometer spectra from within biological cells across an 80 nm bandwidth from 635 to 715 nm.

Paper-based sensor based on lead-free manganese halide for the determination of water content in organic solvents

A highly stable and luminescent lead-free manganese(II) halide hybrid MnBr₄(TMN)₂ (C₃₄H₄₂Br₄MnN₄) was designed and synthesized by introducing a large cationic organic spacer. The MnBr₄(TMN)₂ displays high luminescence with quantum yields up to 77% and possesses turn-off fluorescence behavior (E_x/E_m=365/546 nm) for water. These properties make the MnBr₄(TMN)₂ a promising candidate as an alternative indicator for the detection of water with potential applications for the fabrication of LEDs. Herein, a paper-based sensor based on MnBr₄(TMN)₂ is described for the determination of water content in organic solvents. The mechanism of water sensing can be tentatively explained by fluorescence quenching originating from the destruction of water due to the Mn-Br bonds of MnBr₄(TMN)₂. The MnBr₄(TMN)₂-based paper sensor exhibits an excellent discrimination ability of water content in the range 0-25.0% with a detection limit of 0.27%. Satisfactory recoveries (94.91±4.09% to 103.23±2.38%) are obtained in spiked ethanol solvent samples, which demonstrate that the MnBr₄(TMN)₂-based paper sensor is capable of detecting water content in real ethanol solvent samples.

Microcavity- and Microlaser-Based Optical Barcoding: A Review of Encoding Techniques and Applications

Optical microbarcodes have recently received a great deal of interest because of their suitability for a wide range of applications, such as multiplexed assays, cell tagging and tracking, anticounterfeiting, and product labeling. Spectral barcodes are especially promising because they are robust and have a simple readout. In addition, microcavity- and microlaser-based barcodes have very narrow spectra and therefore have the potential to generate millions of unique barcodes. This review begins with a discussion of the different types of barcodes and then focuses specifically on microcavity-based barcodes. While almost any kind of optical microcavity can be used for barcoding, currently whispering-gallery microcavities (in the form of spheres and disks), nanowire lasers, Fabry-Pérot lasers, random lasers, and distributed feedback lasers are the most frequently employed for this purpose. In microcavity-based barcodes, the information is encoded in various ways in the properties of the emitted light, most frequently in the spectrum. The barcode is dependent on the properties of the microcavity, such as the size, shape, and the gain materials. Various applications of these barcodes, including cell tracking, anticounterfeiting, and product labeling are described. Finally, the future prospects for microcavity- and microlaser-based barcodes are discussed.

Insight into efficient photoluminescence regulation mechanism by lattice distortion and Mn2+ doping in organic-inorganic hybrid perovskites

The space configurations of organic ammonium cations play a vital role in indirectly revealing the relationship between the structures and photoluminescence properties. Structural transformation induced tunability of the photophysical properties has rarely been reported. In this work, two organic-inorganic halide perovskites with different octahedral distortions were synthesized to explore the relationships between "steric effect" of organic cations and photoluminescence properties. The broadband emission of (DETA)PbBr₅·H₂O with high octahedral distortion is attributed to self-trapped excitons and trap states, whereas smaller steric hindrance ammonium cation 1,4-butanediamine form a 2D layered perovskite with narrowband emission due to free excitons. More importantly, the photoactive metal ions Mn²⁺ doping strategy gives rise to tunable broadband light emission from weak to strong orange emission with higher PLQY up to 20.96 % and 12.90% in 0D (DETA)Pb_0.2Mn_0.8Br₅·H₂O and 2D (BDA)Pb_0.8Mn_0.2Br₄ respectively. Combined with time-correlated single photon counting and photoluminescence spectra, Mn-doped perovskites reveal energy transfer from host to Mn²⁺ characteristic energy level (⁴T₁-⁶A₁). Importantly, defect states are reduced by doping manganese ions in (DETA)PbBr₅·H₂O to enhance photoluminescence intensity. This work sheds light on the mechanism of defect-related emission and provides a successful strategy for designing novel and adjustable materials.

Ultralow Threshold Lasing from a Continuous-Wave-Pumped SiNx/CsPbBr3/Ag Thin Film Mediated by the Whispering Gallery Modes of a SiO2 Microsphere

Thin-film pervoskite lasers driven by a continuous wave (CW) laser with ultralow thresholds, which is crucial for the development of on-chip electrically driven lasers, have not yet been realized owing to the low excitation power density of the CW laser. Here, we reported the CW-laser-pumped lasing from a thin film of CsPbBr₃ quantum dots (QDs) sandwiched by a SiN_x and a Ag thin film and mediated by the whispering gallery modes of a SiO₂ microsphere. The stable photoluminescence from CsPbBr₃ QDs with a quantum efficiency of ∼45% is realized by encapsulating with a thin SiN_x film. Upon CW-laser pumping, lasing from the whispering gallery modes with a threshold of ∼11.6 W/cm² is successfully demonstrated at room temperature. The strong localization of electric field achieved in the particle-on-film system, which is revealed in the numerical simulations and lifetime measurements, plays a crucial role in the realization of the ultralow threshold lasing. Our findings open a new avenue for designing photostable CW-laser-pumped pervoskite lasers.

Ultrafast resonant exciton-plasmon coupling for enhanced emission in lead halide perovskite with metallic Ag nanostructures

Integrating metal halide perovskites onto plasmonic nanostructures has recently become a trending method of enabling superior emissive performance of perovskite nanophotonic devices. In this work, we present an in-depth study on the spontaneous emission properties of hybrid systems comprising CsPbBr₃ nanocrystals and silver nanostructures. Specifically, a 5.7-fold increment of the photoluminescence (PL) intensity and a 1.65-fold enhancement of the PL relaxation rate is attained when the transition energy of CsPbBr₃ is spectrally resonant with the oscillational frequency of Ag nanodisks (NDs), which is attributed to the intense exciton-plasmon coupling-induced Purcell effect. Furthermore, a 540-fs ultrafast energy transfer from the CsPbBr₃ excitons to Ag plasmons is revealed by femtosecond pump-probe experiments, suggesting the key mechanism responsible for the Purcell-enhanced radiative emission. Our finding offers a unique understanding of the enhanced emissive behavior in the plasmon-coupled perovskite system and paves the way for further applications.