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Engineering of organic single crystal toward controllable and aligned patterns at microscale is crucial to the realization of highly integrated organic photonic devices and optoelectronics. However, precise positioning and controllable morphology of crystal structures is still challenging due to the strict conditions for crystal growth. In this paper, a solution based crystal regulation strategy with the assistance of template‐constrained growth method and femtosecond laser processing technology is developed to prepare aligned crystalline microribbon arrays. Simple solvent evaporation results in the random distribution and orientation of self‐assembled crystalline microribbons while it tends to form highly crystalline and orderly microribbon arrays assisted by the confined template microchannels. The large‐scale microribbon array can be fabricated as organic photodetectors with sensitive and fast response under 405 nm illumination. By virtue of the femtosecond laser processing technique, the microribbon arrays are precisely processed into a series of crystal subunits and each microribbon subunit can function as an individual microcavity resonator to produce stable, high‐quality organic laser. The facile solution based template‐constrained self‐assembly and femtosecond laser processing method provide novel strategies to generate highly oriented and controllable crystal structures for the potential applications in integrated organic lasers and optoelectronics. [ABSTRACT FROM AUTHOR]

Photonic materials based on metal halide perovskites undergo rapid development owing to their unique optical properties and facile synthesis. Concurrently, there is also a growing interest in integrated photonics that can combine several elements on one chip. Nowadays technologies of integrated photonics are based on the traditional mask lithography combined with physical or chemical deposition methods. In this study, the possibility of facile fabrication of a simple pair of photonic elements is addressed, such as a microresonator with an outcoupling waveguide by means of inkjet printing on a glass substrate covered by a layer of polydimethylsiloxane (PDMS). The printed laser has revealed an appreciably high laser emission with a Q‐factor of 3300 and a threshold excitation fluence of 34 µJ·cm−2. The outcoupling waveguide has demonstrated the capability to transfer a reasonable part of the emitted radiation. The experimental results with a numerical simulation based on an appropriate physical model are also rationalized. Thus, the study points out a perspective for integrated photonics to be possibly implemented with this relatively cheap, flexible, and scalable fabrication method. [ABSTRACT FROM AUTHOR]

Dyes with aggregation‐induced emission (AIE) properties have gained interest due to their bright luminescence in solid‐state aggregates. While fluorescence from AIE dyes is widely exploited, relatively little is known about aggregation‐induced stimulated emission. Here, stimulated emission of tetraphenylethene (TPE)‐based organoboron AIE dyes, TPEQBN, in thin films and in microcavity lasers is investigated. Using femtosecond pump–probe spectroscopy, gain coefficients up to 230 cm−1 at 500 nm are measured. Using rate equations, concentration‐ and pump‐dependent gain dynamics as well as laser build‐up dynamics are analyzed. During laser oscillation, radiative stimulated emission allows high instantaneous quantum yield greater than 90% to be achieved. Solid‐state microspheres made of 100% AIE dyes are fabricated via microfluidic emulsion and solvent evaporation method. Coupled with high gain and high refractive index of 1.76, microspheres as small as 2 µm in diameter show lasing by nanosecond pumping with a threshold of ≈10 pJ µm–2. Polymer coated, but not bare, microspheres are internalized by live cells and generate narrowband cavity‐mode emission from within the cytoplasm. This work shows the potential of AIE dyes as laser materials. [ABSTRACT FROM AUTHOR]

Multiplexed, specific, and sensitive detection of antigens is critical for the rapid and accurate diagnosis of disease and the informed development of personalized treatment plans. Here, it is shown that polymer microsphere lasers can be used as photonic sensors to monitor and quantify direct surface binding of biomolecules via changes in the refractive index. The unique spectral signature of each individual laser can be used to find their size and effective refractive index which adds a new encoding dimension when compared to conventional fluorescent beads. Antibody‐functionalized microlasers selectively detect protein binding, as demonstrated for Immunoglobulin G and C‐reactive protein, and have the ability to resolve different stages of the multilayer surface modification. Moreover, by continuously monitoring single lasers, the possibility of real‐time monitoring of binding dynamics between antigens in solution phase and the immobilized antibodies is demonstrated. For multiplexed detection, the microlasers are employed in a flow cytometer configuration, with fast spectral detection and identification of microlasers with and without antigen binding. It is envisioned that by combining microlasers with well‐established surface modification chemistries and flow geometries, the multiplexing ability of microbead immunoassays can be strongly increased while also opening avenues for single‐cell profiling within heterogeneous cell populations. [ABSTRACT FROM AUTHOR]

Halide perovskite lasers based on CsPbBr3 micro‐ and nanoscale crystals have demonstrated fascinating performance owing to their low‐threshold lasing at room temperature and cost‐effective fabrication. However, chemically synthesized thin films of CsPbBr3 usually have rough polycrystalline morphology along with a large amount of crystal lattice defects and, thus, are mostly utilized for the engineering of light‐emitting devices. This obstacle prevents their usage in many photonic applications. Here, a protocol to deposit large‐grain and smooth CsPbBr3 thin films is developed. Their high quality and large scale allow to demonstrate a maximum optical gain up to 12 900 cm−1 in the spectral range of 530–540 nm, which is a record‐high value among all previously reported halide perovskites and bulk semiconductors (e.g., GaAs, GaN, etc.) at room temperature. Moreover, femtosecond laser ablation technique is employed to create high‐quality microdisc lasers on glass from these films to obtain excellent lasing characteristics. The revealed critical roles of thickness and grain size for the CsPbBr3 films with extremely high optical gain pave the way for development of low‐threshold lasers or ultimately small nanolasers, as well as to apply them for polaritonic logical elements and integrated photonic chips. [ABSTRACT FROM AUTHOR]

Low‐dimensional perovskite structures are ideal materials for nano/microlasers owing to their excellent optical gain properties and high emission efficiency. But it is still a challenge to achieve single‐mode and tunable lasing behaviors in micro‐scale perovskite, especially showing ultralow thresholds in tens of µJ cm−2. In this work, CsPbBr3/Ag hemispheroids have been synthesized in a designed chemical vapor deposition (CVD) process. Benefiting from the whispering gallery resonance mode and plasmon‐enhanced light–matter interactions in well‐confined hybrid cavities, the CsPbBr3/Ag plasmonic microlasers exhibit low pump thresholds down to 35–51 µJ cm−2. Interestingly, single‐mode and two‐mode lasing behaviors are determined by the morphology of plasmonic Ag nanostructures, and lasing modes could be selectively tuned by increasing the pump fluence accompanying with dynamic competitions of photonic and plasmonic modes. Simulations of electromagnetic field have been plotted to show near‐field resonant modes for a comprehensive understanding of plasmon‐assisted lasing. These results not only provide a solution to fabricate low‐threshold plasmonic microlasers, but also advocate the prospect of all‐inorganic perovskite nanostructures as promising candidates for on‐chip integrated light sources. [ABSTRACT FROM AUTHOR]

Micro‐ and nanolasers are emerging optoelectronic components with many properties still to be explored and understood. On the one hand, they make it possible to address fundamental physical questions in the border area between classical physics and quantum physics, on the other hand, they open up new application perspectives in many areas of photonics. This progress report provides an overview of the exciting developments from conventional semiconductor lasers toward nanoscale lasers, whose function relies on increased light–matter interaction in low‐mode‐volume resonators and unconventional gain concepts. The latest advances in the physical understanding of light emission from high‐β lasers, in which a large part of the spontaneous emission is coupled into the laser mode, are highlighted. In the limit of β = 1, this leads to thresholdless lasing and it is shown that quantum optical characterization is required to fully explore the underlying emission processes. In addition, emerging nanolaser concepts based on Fano resonators, topological photonics, and 2D materials are presented. Open questions, future prospects, and application scenarios of high‐β lasers in integrated photonics, quantum nanophotonics, and neuromorphic computing are discussed. [ABSTRACT FROM AUTHOR]

Spatial filtering is an important mechanism to improve the spatial quality of laser beams. Typically, a confocal arrangement of lenses with a diaphragm in the focal plane is used for intracavity spatial filtering. Such conventional filtering requires access to the far‐field domain. In microlasers, however, conventional filtering is impossible due to the lack of space in microresonators to access the far‐field. Therefore, a novel concept for more compact and efficient spatial filtering is necessary. In this study, a conceptually novel mechanism of spatial filtering in the near‐field domain is proposed and demonstrated, by a nanostructured multilayer coating—a 2D photonic crystal structure with a periodic index modulation along the longitudinal and transverse directions to the beam propagation. The structure is built on a nanomodulated substrate, to provide the transverse periodicity. The physical vapor deposition is used to provide self‐repeating modulation in the longitudinal direction. A 5 µm thick photonic multilayer structure composed of nanostructured multiple layers of alternating high‐ and low‐index materials providing spatial filtering in the near‐infrared frequencies with 2° low angle passband is experimentally demonstrated. The proposed photonic structure can be considered as an ideal component for intracavity spatial filtering in microlasers. [ABSTRACT FROM AUTHOR]

Semiconductor heterostructures hold the promise for developing novel integrated devices with on‐demand photonic and optoelectronic properties. Herein, the perovskite lateral heterostructures in forms of microplates and microwires are fabricated by precise control of two‐step atmospheric pressure chemical vapor deposition course and the unique optical properties are demonstrated for the first time. The comprehensive spectroscopic and elemental mapping characterizations reveal the core‐shell‐like configuration of the individual heterostructure, which features the fascinating energy routing nature. Taking advantage of the effective photon recycling and the energy transfer processes, the record‐low threshold (≈3.5 µJ cm−2) lasing and the indirect pumping induced lasers from the single micro‐heterostructure are demonstrated. Moreover, the distinctive optical waveguides with propagation length independent output spectra from the microwire heterostructure are realized. These findings represent a significant advance in developing novel and functional optoelectronic devices by engineering the perovskite heterostructure. [ABSTRACT FROM AUTHOR]

Lasers based on biological materials are attracting an increasing interest in view of their use in integrated and transient photonics. Deoxyribonucleic acid (DNA) as optical biopolymer in combination with highly emissive dyes has been reported to have excellent potential in this respect. However, achieving miniaturized lasing systems based on solid‐state DNA shaped in different geometries to confine and enhance emission is still a challenge, and the physicochemical mechanisms originating fluorescence enhancement are not fully understood. Herein, a class of wavelength‐tunable lasers based on DNA nanofibers is demonstrated, for which optical properties are highly controlled through the system morphology. A synergistic effect is highlighted at the basis of lasing action. Through a quantum chemical investigation, it is shown that the interaction of DNA with the encapsulated dye leads to hindered twisting and suppressed channels for the nonradiative decay. This is combined with effective waveguiding, optical gain, and tailored mode confinement to promote morphologically controlled lasing in DNA‐based nanofibers. The results establish design rules for the development of bright and tunable nanolasers and optical networks based on DNA nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: Metal‐halide perovskites are recently extensively investigated as light absorbing material in solar cells. The outstanding optoelectronic properties and tunable light emission of the perovskites also make them promising candidates for light emitting diodes and lasers. However, understanding the relevant mechanisms and processes of the dependence of perovskite light emission on temperature and crystal size is still challenging. Herein, the CH3NH3PbBr3 monocrystals of different sizes are uniformly excited by two‐photon absorption at 800 nm (100 fs, 1 KHz). In contrast to the reported relative large exciton binding energy (≈76 meV) and spectrum clearly resolved excitonic absorption, the light emission origin in CH3NH3PbBr3 microcrystals at room temperature is unambiguously determined to be dominated by free electron–hole bimolecular recombination. The coherent light emission threshold of CH3NH3PbBr3 microcrystal increases with temperature, which is closely related to the temperature induced transition from exciton gas to free charge carriers. In addition, the coherent light emission threshold is found to decrease with the microcrystal size, which could be well interpreted by the interaction between the optical confinement, defect density, and cavity quantum electrodynamics effect. These results presented here may facilitate the development of perovskite light emitting diodes and lasers. [ABSTRACT FROM AUTHOR]

Solution‐processed lead halide perovskites have shown good applicability in both solar cells and microlasers. Very recently, the nonlinear properties of perovskites have attracted considerable research attention. Second harmonic generation and two‐photon absorption have been successfully demonstrated. However, perovskite devices based on these nonlinear properties, such as micro‐ and nanolasers have thus far not been fabricated. Here we demonstrate two‐photon pumped microlasers from CH3NH3PbBr3 perovskite microwires. These CH3NH3PbBr3 perovskite microwires are synthesized through a one‐step solution precipitation method and dispersed on a glass substrate. Under optical excitation at 800 nm, two‐photon pumped lasing action with periodic peaks is successfully observed at around 546 nm. The obtained quality (Q) factors of the two‐photon pumped microlasers are around 682, and the corresponding thresholds are about 674 µJ cm‐2. Both the Q factors and thresholds are comparable to conventional whispering‐gallery modes in two‐dimensional polygon microplates. This work is the first demonstration of two‐photon pumped microlasers in CH3NH3PbBr3 perovskite microwires. We believe our finding will significantly expand the application of perovskites in low‐cost nonlinear optical devices, such as optical limiters, optical switches, and biomedical imaging devices. [ABSTRACT FROM AUTHOR]

Microlasers have experienced tremendous development in the past decade and become an essential part in laser evolution, as miniature lasers provide strong optical confinement and feature greatly enhanced light–matter interactions. Among all the configurations, whispering gallery mode (WGM) microcavities and microlasers exhibit outstanding optical performances with high quality factors and small mode volumes, thus ensuring low lasing thresholds. In addition, some unique properties inherent to WGM cavities, like bi‐directional propagation and an evanescent field that spans several hundred nanometers across the boundary, can be exploited for novel applications. Therefore, designing and engineering innovative WGM microcavities and microlasers has attracted increasing research interest. The fundamentals and characteristics of WGM are introduced here, and then the developments and current status of WGM microcavities and microlasers are reviewed in terms of the evolution of fabrication techniques and built‐up materials. In particular, the melting of glassy materials in early studies, top‐down and bottom‐up approaches with semiconductors, coating structures, as well as flexible, soft microresonators in recent years are presented. Finally, the application prospects of microlasers including the wavelength manipulation, sensing and microresonator coupling, are discussed. [ABSTRACT FROM AUTHOR]

Organic lasers have become an important research and application target for the development of optoelectronics and future photonics due to their ease of preparation and miniaturization, low threshold, and wideband tunability, as well as large optical and nonlinear optical cross sections. Recently, the metal–organic framework (MOF) based organic microlasers have received increasing research attention because they not only achieve high gain concentrations while minimizing the common aggregation‐caused quenching effect of organic luminescence systems, but also can optimize and even control the output performance of the laser by manipulating the interaction between the framework and the gain molecules. In this review, the latest advances in MOF‐based organic lasers are explored and insights into future trends are given, providing useful guidance for the design and preparation of new‐type lasers. [ABSTRACT FROM AUTHOR]

Soft‐matter microlasers are an interesting part of soft‐matter photonics, which are based on liquids, liquid crystals, polymers, biological materials, and fabricated mainly by solution‐processing approaches. Soft‐matter microlasers comprehend a multitude of attractive features, including low‐cost, mechanical flexibility, wide range wavelength tunability and, in some cases, biocompatibility, and biodegradability. As such, they are recognized as versatile candidates for efficient light sources with enhanced performances and applications as ultrasensitive physical, chemical, and biological sensors. Here, the recent developments of soft‐matter microlasers are reviewed in time and the prospect in this field is provided. First, the characteristics of the representative soft‐matter microlasers are discussed with focus on their laser structures, lasing mechanisms, fabrication approaches, and gain material origins, followed by an introduction about the current cutting‐edge soft‐technologies that are applied in soft‐matter microlasers. Afterward, their potential applications as wavelength tunable sources, sensors, and displays are highlighted. Finally, the work is summarized and the prospect of soft‐matter microlasers for expanding this emerging research field is presented. [ABSTRACT FROM AUTHOR]