Toward Microlasers with Artificial Structure Based on Single-Crystal Ultrathin Perovskite Films.

A perovskite microlaser is potentially valuable for integrated photonics due to its excellent properties. The artificial microlasers were mostly made on polycrystalline films. Though a perovskite single crystal has significantly improved properties in comparison with its polycrystalline counterpart, an artificial microlaser based on single-crystal perovskite has been much less explored due to the difficulty in producing an ultrathin-single-crystal (UTSC) film. Here we show a device processing based on a perovskite UTSC film, confirming the high performance of the UTSC device with a quality factor of 1250. The single-crystal device shows 4.5 times the quality factor and 8 times the radiation intensity in comparison with its polycrystalline counterpart. The experiment first proved that hybrid perovskite microlasers with a subwavelength fine structure can be processed by focused ion beams (FIB). In addition, a wavelength-tunable distributed feedback (DFB) laser is demonstrated, with a tuning range of ∼4.6 nm. The research provides an easily applicable approach for perovskite photonic devices with excellent performance.

Continuous-Wave Lasing in Perovskite LEDs with an Integrated Distributed Feedback Resonator.

Realization of electrically pumped laser diodes based on solution-processed semiconductors is a long-standing challenge. Metal halide perovskites have shown great potential toward this goal due to their excellent optoelectronic properties. Continuous-wave (CW) optically pumped lasing in a real electroluminescent device represents a key step to current-injection laser diodes, but it has not yet been realized. This is mainly due to the challenge of incorporating a resonant cavity into an efficient light-emitting diode (LED) able to sustain intensive carrier injection. Here, CW lasing is reported in an efficient perovskite LED with an integrated distributed feedback resonator, which shows a low lasing threshold of 220 W cm-2 at 110 K. Importantly, the LED works well at a current density of 330 A cm-2 , indicating the carrier injection rate already exceeds the threshold of optically pumping. The results suggest that electrically pumped perovskite laser diodes can be achieved once the Joule heating issue is overcome.

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.

Ultralow-Threshold Continuous-Wave Room-Temperature Crystal-Fiber/Nanoperovskite Hybrid Lasers for All-Optical Photonic Integration.

Continuous-wave (CW) room-temperature (RT) laser operation with low energy consumption is an ultimate goal for electrically driven lasers. A monolithically integrated perovskite laser in a chip-level fiber scheme is ideal. However, because of the well-recognized air and thermal instabilities of perovskites, laser action in a perovskite has mostly been limited to either pulsed or cryogenic-temperature operations. Most CW laser operations at RT have had poor durability. Here, crystal fibers that have robust and high-heat-load nature are shown to be the key to enabling the first demonstration of ultralow-threshold CW RT laser action in a compact, monolithic, and inexpensive crystal fiber/nanoperovskite hybrid architecture that is directly pumped with a 405 nm diode laser. Purcell-enhanced light-matter coupling between the atomically smooth fiber microcavity and the perovskite nanocrystallites gain medium enables a high Q (≈1500) and a high ß (0.31). This 762 nm laser outperforms previously reported structures with a record-low threshold of 132 nW and an optical-to-optical slope conversion efficiency of 2.93%, and it delivers a stable output for CW and RT operation. These results represent a significant advancement toward monolithic all-optical integration.

Imaging and Controlling Photonic Modes in Perovskite Microcavities.

Perovskite microcavities have excellent photophysical properties for integrated optoelectronic devices, such as nanolasers. Imaging and controlling the photonic modes within the cavity are fundamentally important to understand and develop applications. Here, photoemission electron microscopy (PEEM) is used to image the photonic modes within optical microcavities with a nanometer-scale spatial resolution. From a CsPbBr3 microcavity, hybrid mode patterns are observed. Spatial frequency spectrum analysis on the patterns uncovers the characteristic cavity modes, which are modeled with transverse magnetic (TM) and transverse electric (TE) waves, and assigned to exciton-polariton modes. Based on this understanding, the light focus in a designed microcavity is imaged in real space and controlled by the light field polarization. The study confirms that the cavity modes in perovskites can be effectively observed by the PEEM technique under resonant excitation, which, in turn, promotes the design of optoelectronic devices based on perovskite microcavities.