In the past decade, lead halide perovskites have emerged as potential optoelectronic materials in the fields of light-emitting diode, solar cell, photodetector, and laser, due to their low-cost synthesis method, tunable bandgap, high quantum yield, large absorption, gain coefficient, and low trap-state densities. In this review, we present a comprehensive discussion of lead halide perovskite applications, with an emphasis on recent advances in synthetic strategies, morphology control, and lasing performance. In particular, the synthetic strategies of solution and vapor progress and the morphology control of perovskite nanocrystals are reviewed. Furthermore, we systematically discuss the latest development of perovskite laser with various fundamental performances, which are highly dependent on the dimension and size of nanocrystals. Finally, considering current challenges and perspectives on the development of lead halide perovskite nanocrystals, we provide an outlook on achieving high-quality lead perovskite lasers and expanding their practical applications.

When approaching the subwavelength or deep subwavelength scale, there is a fundamental trade-off between the ultimate shrinking size and the performance for miniaturized lasers. Herein, to overcome this trade-off, we investigated the excitonic gain nature of quasi-two-dimensional (quasi-2D) perovskites and revealed that both singlet excitons and polarons would make nearly the entire contribution within ∼50 ps to a high net gain of 558 cm–1. Inspired by the gain characteristic, we successfully shrank the quasi-2D perovskites laser to the subwavelength scale using only a layer of ultraviolet glue and a glass substrate in the vertical dimension. In spite of the compact and simple cavity structure, single-mode lasing with a highly linear polarization degree of 81% and a quality factor of 1635 was achieved. The extremely short cavity, excellent lasing performance, and simple structure of the quasi-2D perovskite laser are expected to provide insights into next-generation integrated laser sources.

states can generate structured spatial light fields via the comprehensive manipulations of the helical phase, polarization, and propagation of the light. Intuitively, the equal-weighted superposition of OAM states with TCs of opposite signs may generate spatial modes of petal-like intensity with nonzero or zero global OAMs, and superpositions of higher-order OAMs may produce wheel-like modes with azimuthal variations of intensity in high dimensions. A variety of methods or devices have been developed to enable the superposition of OAMs. These include liquid crystal q-plates, [1][2][3] spatial light modulators, [4,5] crystal prism pairs, [6] microscopic ring resonators, [7,8] and other optical elements. [9][10][11] Moreover, the progress in OAM superposition has brought about many important applications in classical physics and quantum sciences. Classical applications include particle trapping, [12] optical communications, [13,14] and relativistic laser-matter interactions. [15,16] In the quantum field, important advancements have been made in quantum communications, [17][18][19] quantum information processing, [20,21] and quantum calculations. [22,23] The potential to miniaturize superposed spatial modes of OAM to nanoscale is promising for the implementation of integrated on-chip devices. Metasurfaces consisting of monolayers of subwavelength metallic/dielectric structures have become an efficient way to manipulate light at the subwavelength scale. In recent several years, the study of metasurfaces has attracted great interest in areas as phase-controlled, [24] broadband vectorial holograms, [25] broadband achromatic metalenses, [26] and the coherent control of plasmonic spin-Hall effects. [27] The development of metasurfaces for the manipulation of OAM states has also been studied extensively. [28][29][30][31][32][33][34][35] In the past year, significant progress has been made in achieving arbitrarily controlled OAM superposition states via metasurface engineering. Devlin et al. have proposed the metasurface J-plate to realize the superposition of independent OAM states and to convert SAMs into total angular momentum states. [36] Using a reflective plasmonic metasurface, Yue et al. demonstrated various OAM superpositions in multiple channels by changing the polarization of the illumination. [37,38] By designing a nonlinear plasmonic metasurface for the simultaneous control of the OAM and SAM, Li et al. achieved the OAM superposition of the modes of the second Superposition of orbital angular momentum (OAM) states and the structured intensity are providing new approaches for manipulating optical information and light-matter interactions. While superposition of OAMs in free space has been well studied, further extensions to surface plasmon polariton (SPP) confined in near-field would be crucial for miniaturing and integrating platforms. Here, the plasmonic metasurfaces consisting of rotated nanoslits arranged in a segmented spiral are proposed to realize the superposition of two SPP OAM states. The nanoslit rota...

Despite the superior optoelectronic properties of quasi-two-dimensional (quasi-2D) Ruddlesden–Popper halide perovskites, the inhomogeneous distribution of mixed phases result in inefficient energy transfer and multiple emission peaks. Herein, the insufficient energy funneling process at the high-energy phase is almost completely suppressed and the excitonic understanding of gain nature is studied in the energy funneling managed quasi-2D perovskite via introducing poly­(vinyl pyrrolidone) (PVP) additive. The energy transfer process is facilitated from 0.37 to 0.26 ps after introducing the PVP additive, accelerating the exciton accumulation in the emissive state, and increasing the ratio of the high-dimensional phase for enhancing radiative emission. The gain lifetime is promoted to be as fast as 28 ps to outcompete nonradiative recombination during the build-up of population inversion. Simultaneously, the net gain coefficient is increased by more than twofold that of the pristine perovskite film. Owing to the remarkable gain properties, room-temperature amplified spontaneous emission is realized with a low threshold of 11.3 μJ/cm2, 4 times lower than 43 μJ/cm2 of the pristine film. Our findings suggest that the PVP-treated quasi-2D perovskite shows great promise for high-performance laser devices.

Nanoscale lattices of arbitrary orders are generated by truncated spiral metasurfaces combining geometric and dynamic phases.

The Dirac fermion, a high-mobility electron in the Dirac cone of monolayer graphene, has significant potential for use in the terahertz probing technique. For undoped graphene, ultrafast terahertz conductivity relaxation is mostly driven by electron–acoustic phonon supercollision coupling. The decay time of this coupling can be increased to tens or hundreds of picoseconds by decreasing the temperature. However, for chemical vapor deposition (CVD)-grown graphene, which exhibits negative photoinduced terahertz conductivity, there is currently no consensus on the dominant aspects of the terahertz conductivity relaxation process on time scales of less than 10 ps. In this study, the competition between electron–acoustic and optical–acoustic phonon coupling processes during the cooling of CVD graphene was systematically investigated. We experimentally verified that the ultrafast disorder-assisted optical–acoustic phonon interaction plays a key role in ultrafast terahertz conductivity relaxation. Furthermore, the ultrafast cooling process was found to be robust under different pump wavelengths and external temperatures, and it could be modulated by substrate doping. These findings are expected to contribute to a possible cooling channel in CVD graphene and to increase hot electron extraction efficiency for the design of graphene-based photoconversion devices.

Vector beams contain complex polarization structures and they are inherently non-separable in the polarization and spatial degrees of freedom. The spatially variant polarizations of vector beams have enabled many important applications in a variety of fields ranging from classical to quantum physics. In this study, we designed and realized a setup based on Mach-Zehnder interferometer for achieving the vector beams at arbitrary points of higher-order Poincaré sphere, through manipulating two eigenstates in the Mach-Zehnder interferometer system with the combined spiral phase plate. We demonstrated the generation of different kinds of higher-order Poincaré beams, including the beams at points on a latitude or longitude of higher-order Poincaré sphere, Bell states for |l| = 1 and |l| = 2, radially polarized beams of very high order with l = 16, etc. Vector beams of high quality and good accuracy are experimentally achieved, and the flexibility, feasibility and high efficiency of the setup are demonstrated by the practical performance.

Polarization state of a wave field can be manipulated through the plasmonic metasurface consisting of orthogonal nanoslit pairs; the output polarization angle is independent of the incident linearly polarized light and is highly dependent on the orientations of nanoslit pairs. We combine the Archimedes spiral with the nanoslit pairs to compensate for the Pancharatnam-Berry (PB) phase induced by the orientation of nanoslits, as well as achieve the radially polarized vector beam (RPVB) under the illuminations of different linearly polarized lights. Experiments are performed to successfully realize the RPVB, and the results are in excellent agreement with the numerical simulations.