The integration of crystallographic control into solution-processed perovskite films remains a challenge for efficient light emission, as disordered optical dipoles fundamentally limit photon extraction, a bottleneck constraining both classical and quantum planar optoelectronic devices. Here, we address this by developing an in situ formation strategy for oriented quasi-2D perovskite nanosheets within films via ligand-engineered crystallization. By designing and orchestrating steric hindrance and π-π interactions of ligands, we direct the crystallization kinetics to yield regular face-on nanosheets exhibiting enhanced horizontal transition dipole moment orientation compared to conventional isotropic films. The in situ architectural control also elevates both the photoluminescence quantum yield beyond 90% and carrier mobility comparable to 3D perovskite levels. These synergies enable perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency (EQE) of 31.2% for pure-red emission at 635 nm, comparing favorably to other pure-red PeLEDs. Concurrently, the peak luminance and operational stability of the in situ nanosheet PeLEDs exhibit significant improvements.

A recent study demonstrates a metasurface platform for 3D vectorial holography that enables independent control of light intensity and polarization along the propagation axis. By utilizing longitudinally engineered meta-atoms, this approach achieves multi-dimensional optical encryption platform.

The rapid evolution of eavesdropping technologies has encouraged regular updates and improvement of encryption systems. Developing a detector-dependent optical encryption scheme to tightly connect the decryption and imaging processes offers great potential to prevent eavesdropping. By designing an optically programmable dual-band photodetector, a color image encryption scheme where the photodetector functions as both a detector and a critical decryption key is demonstrated here. The distinctive optically programmable property of the photodetector enables the manipulation of its long-wavelength sensitivity via short-wavelength photonic stimulation, leading to different imaging outputs between single-pixel imaging and point-scan imaging, which therefore demonstrates a capability to decrypt information hidden in color images. This detector-dependent decryption method can effectively prevent potential information leaks when other detectors are used as eavesdropping devices. Our encryption paradigm opens new avenues for color image encryption using photodetectors, enhancing encryption security by introducing a device-based dimension.

Integrated green light sources are essential for telecommunications and quantum applications, while the performance of current on-chip green light generation is still limited in power and tunability. In this work, we demonstrate green light generation in silicon nitride microresonators using photo-induced second-order nonlinearities, achieving up to 3.5 mW green power via second-harmonic generation and densely tunable over a 29 nm range. In addition, we report milliwatt-level all-optical poling (AOP) threshold, allowing for amplifier-free continuous-wave AOP. Furthermore, we demonstrate non-cascaded sum-frequency generation, leveraging the combination of AOP and simultaneous coherent frequency combs generation at 1 μm. Such comb-assisted AOP enables switching of the green light generation over an 11 nm range while maintaining the pump within a single resonance. The combination of such highly efficient photo-induced nonlinearity and multi-wavelength AOP enables the realization of low-threshold, high-power, widely-tunable on-chip green sources.

InGaN-based micro-light-emitting diodes (micro-LEDs) are emerging to revolutionize the display and lighting technologies, particularly for their excellent robustness, high brightness, high efficiency and small pixel size. Despite the success of blue LEDs, long-wavelength emission, particularly the red emission, has been a challenge for InGaN-based micro-LEDs. Overcoming the low quantum efficiency, color instability, and broad emission in the red wavelength regime are among the most urgent and critical problems that inhibit the commercial implementation of micro-LED technology. In this work, we utilize a nanowire photonic crystal (PhC) structure to reform the radiation behavior of red-emitting InGaN micro-LEDs. Through detailed optimization on the PhC design and device fabrication, we demonstrate red-emitting micro-LEDs with a peak wavelength at 617 nm and a full-width-at-half-maximum (FWHM) of 5 nm, which is about one order of magnitude narrower than previous reported values and is paramount for achieving high color purity. The chromaticity property is highly stable with varying injection currents due to the coupling of emission to photonic band edge mode. A high external quantum efficiency of over 10% was measured from micro-LEDs with a size of 1 µm2. This work provides a vital strategy for high-performance red-emitting micro-LEDs and a potential pathway for full-color micro-LED technology by using all III-nitride semiconductors.

A novel concept for distributed fiber sensing has recently been introduced, in which the sensing fiber itself forms a laser cavity. This configuration yields a high-quality response that is largely independent of position, thereby enhancing measurement accuracy and acquisition speed, and opening new avenues towards higher-performance sensing technologies.

Stimuli-responsive organic-inorganic metal halides hold great promise for emerging information-related applications. In this work, replacing the free halide ion Cl- with Br- in C5H11N3(MnCl3·H2O)X (where C5H11N32+ represents histamine cation, X represents free halide ions) converts the non-responsive hybrid C5H11N3(MnCl3·H2O)Cl into a stimuli-responsive C5H11N3(MnCl3·H2O)Br. The latter exhibits reversible photoluminescence color switching between red and green upon thermal or water exposure. Extensive experimental and theoretical analyses reveal that the responsive property primarily stems from weakened hydrogen bonding surrounding H2O molecules after Br- substitution, which facilitates the initial escape of H2O molecules under heating. Subsequent structural reorganization and coordination transformation then induce the change in photoluminescence. Furthermore, the fabricated halide/polymer luminescent films are demonstrated to be highly applicable in multiple scenarios, such as planar temperature sensing, thermal stamping, and encryption/decryption. This study highlights the crucial yet often overlooked role of free halide ions in metal halides and offers new insights into their structure-property relationships.

Micro-nano lasers hold significant promise for on-chip integrated photonics, where perovskite materials emerge as compelling gain media despite stability challenges. While moisture typically degrades perovskite structures, its controlled integration can paradoxically enhance crystallization. Here, we demonstrate a synergistic strategy utilizing water molecules and butylated hydroxytoluene (BHT) additive to achieve high-quality methylammonium lead iodide (MAPbI₃) films with low defect density. Through optimized BHT (4 wt%) combined with 95% relative humidity treatment, we attain an unprecedented amplified spontaneous emission (ASE) threshold of 8.987 μJ cm⁻² under nanosecond pulse excitation – the lowest value reported to date. This dual-triggered film completes ASE intensity retention after 30-day ambient storage. In situ structural and optoelectronic characterization reveals that BHT extends water-perovskite interaction, facilitating organic cation vertical diffusion and preferential (110)-oriented crystallization with 53.02% perpendicular alignment. Transient absorption (TA) spectroscopy confirms suppressed non-radiative recombination, evidenced by 11% prolonged carrier lifetime (6145 ps), while temperature-dependent photoluminescence reveals enhanced exciton binding energy (73.50 meV vs. 60.68 meV) conducive to low-threshold lasing. This work transforms moisture from a degradation agent into a crystallization promoter, establishing a paradigm for high-performance perovskite lasers with simultaneous efficiency and stability.

Photoacoustic microscopy (PAM) systems often face challenges in simultaneously achieving high speed, high resolution, high sensitivity, and a large field of view (FOV). To address this challenge, we have developed dual-channel PAM (DC-PAM) that can expand the FOV without compromising the imaging speed, detection sensitivity, or spatial resolution. DC-PAM has two identical, independent channels of laser excitation and acoustic detection. It exploits two facets of a single hexagon scanner to concurrently steer the dual excitation laser beams and the resultant acoustic waves. DC-PAM achieves an ultra-wide FOV of 22.5 × 24 mm² with a total functional imaging time of ~15 s. Proof-of-concept experiments were conducted using DC-PAM on freely-swimming zebrafish, hypoxia-challenged mice, and sleeping glassfrogs, all of which benefit from the large FOV and high imaging speed to track the dynamic and physiological processes at the whole-organ or whole-body level. These applications demonstrate the potential of DC-PAM for a wide range of biological studies.