Ultrahigh-Q Lead Halide Perovskite Microlasers

Phase Transition and Luminescent Property Change Induced by Different Organic Cations in One-Dimensional Double Perovskites

Double perovskites (DPs) have attracted attention in the field of luminescence due to their inherent broadband emission of self-trapping excitons. In this work, we choose [(CH3)3NCH2CHCH2]+ and [CH3CHOHCH2NH2]+ as organic cations to synthesize two new organic-inorganic hybrid DPs, [(CH3)3NCH2CHCH2]2KInCl6 (1) and [CH3CHOHCH2NH2]2KInCl6 (2). The [KCl6]3- and [InCl6]3- octahedra are interchangeably connected by sharing two opposite faces, forming a one-dimensional coordination chain. Each K atom coordinates with six chlorine atoms in 1, while it coordinates with two oxygen atoms in addition to the six chlorine atoms in 2. The coordination between ions K and O in compound 2 may have significantly reduced its luminescence. As a result, compound 1 shows bright-yellow light with a quantum yield of more than 90%, while 2 shows weak blue light with a quantum yield of only 0.98%. In addition, different from no phase transition found in 2, 1 undergoes a reversible phase transition at 324/307 K in the heating-cooling cycle. Through structural and spectral analysis and density functional theory calculation, we conclude that the larger degree of [InCl6]3- octahedral distortion and the larger anion distance (In···In) also cause the PLQY of compound 1 to be higher than that of compound 2.

Bound states in the continuum in circular waveguides: toward the on-chip integration of nanofiber on silicon platform

In previously reported researches on bound state in the continuum (BIC) waveguides, almost all of them are demonstrated with top-down fabrication procedures, leading to inconvenience for post-manipulation and size tuning. Nanofibers with circular cross sections are the fundamental components to transport energy due to their intrinsic advantages of high flexibility and adjustability, which is replaceable and can be readily manipulated over size and position on the substrate. In this work, we explore the possibility of achieving on-chip integration of silica nanofiber onto a silicon-on-insulator platform. By constructing additional leakage channels in coupled nanofiber waveguides, coherently destructive interferences are successfully achieved. The heavy leakage losses from the low-index nanofiber to a high-index silicon substrate are completely eliminated with BIC, and the propagation length of the nanofiber waveguide is significantly improved.

High Q-Factor Single-Mode Lasing in Inorganic Perovskite Microcavities with Microfocusing Field Confinement

The realization of high-Q single-mode lasing on the microscale is significant for the advancement of on-chip integrated light sources. It remains a challenging trade-off between Q-factor enhancement and light-field localization to raise the lasing emission rate. Here, we fabricated a zero-dimensional perovskite microcavity integrated with a nondamage pressed microlens to three-dimensionally tailor the intracavity light field and demonstrated linearly and nonlinearly (two-photon) pumped lasing by this microfocusing configuration. Notably, the microlensing microcavity experimentally achieves a high Q-factor (16700), high polarization (99.6%), and high Purcell factor (11.40) single-mode lasing under high-repetition pulse pumping. Three-dimensional light-field confinement formed by the microlens and plate microcavity simultaneously reduces the mode volume (∼3.66 μm3) and suppresses diffraction and transverse walk-off loss, which induces discretization on energy-momentum dispersions and spatial electromagnetic-field distributions. The Q factor and Purcell factor of our lasing come out on top among most of the reported perovskite microcavities, paving a promising avenue toward further studying electrically driven on-chip microlasers.

Compact angle-resolved metasurface spectrometer

Light scattered or radiated from a material carries valuable information on the said material. Such information can be uncovered by measuring the light field at different angles and frequencies. However, this technique typically requires a large optical apparatus, hampering the widespread use of angle-resolved spectroscopy beyond the lab. Here we demonstrate compact angle-resolved spectral imaging by combining a tunable metasurface-based spectrometer array and a metalens. With this approach, even with a miniaturized spectrometer footprint of only 4 × 4 μm2, we demonstrate a wavelength accuracy of 0.17 nm, spectral resolution of 0.4 nm and a linear dynamic range of 149 dB. Moreover, our spectrometer has a detection limit of 1.2 fJ, and can be patterned to an array for spectral imaging. Placing such a spectrometer array directly at the back focal plane of a metalens, we achieve an angular resolution of 4.88 × 10-3 rad. Our angle-resolved spectrometers empowered by metalenses can be employed towards enhancing advanced optical imaging and spectral analysis applications.