Zhijia Hu

Random lasers (RLs), characterized by cavity-free feedback, multiple-scattering-induced shot-to-shot fluctuations, and broadband spectral scalability, have been regarded as promising physical entropy sources for true random number generators (TRNGs). However, existing RL-based studies have mainly focused on single emission windows or limited spectral fluctuations, while a broadband, multi-window cascaded RL suitable for random bit extraction remains insufficiently developed and validated. Here, it demonstrates a three-dye-doped cascaded random laser (FCRL) based on Förster resonance energy transfer (FRET). The inter-dye energy transfer mechanism and mode competition enable multi-window FCRL emission from short to long wavelengths, and sustained shot-to-shot spectral fluctuations. The broadband and high-randomness FCRL is used to construct a high-entropy TRNG. Random bits are extracted based on single-pulse spectral sequences, and their randomness and reliability are confirmed via autocorrelation analysis, 0/1 balance evaluation, and NIST statistical tests. Meanwhile, the generated physical random bits are applied to RGB color image encryption, illustrating their potential as physical random key sources. This work not only validates the effectiveness of FCRL for broadband multi-window emission regulation but also establishes a comprehensive application platform spanning the design of a broadband physical entropy source and the construction of a high-entropy TRNG to the implementation of anti-counterfeiting encryption.

By regulating the SP/MC isomer ratio via light irradiation, we modulate the intramolecular FRET process and tune the gain spectra within microdroplets, enabling precise control over the resultant WGM resonant spectra.

Ethanol detection technology plays an increasingly important role in the production and life of modern society. Its applications cover a wide range of important areas from industrial safety monitoring to personal health management. In order to measure the concentration of ethanol in gas, a portable polymer optical fiber ethanol sensor based on a fiber tapered cone area coated with Metal-Organic Framework-5 (MOF-5) is proposed in this paper. The sensor detects the concentration of ethanol gas in the environment by means of intensity modulation, and a portable optical fiber ethanol sensor is fabricated using an Arduino development board, which demonstrates the feasibility of low-cost portable detection. The experimental results show that the sensor exhibits the best sensing performance with a sensitivity of 0.1963%/(g/m ³ ) and a response time of 15 seconds when the optical fiber tapered area is 15 mm in length and 200 µm in diameter. In addition, the sensor demonstrates good repeatability and stability, which has a broad potential for application in human alcohol concentration detection.

Random lasers rely on multiple scattering in disordered media to generate emission with complex spectral behavior. While their high-entropy output is valuable for random number generation, the inherent unpredictability has historically limited their utility in structured information processing. Here, we demonstrate the coexistence of spectral randomness and determinism within these systems. Using deep neural networks for multi-dimensional spectral analysis, we identify inter-modal correlations that permit partial recovery of spectral intensity components, despite temporal fluctuations. We then develop a key generation and distribution scheme utilizing the dual nature of random lasers: the disorder ensures cryptographic randomness, while the underlying order facilitates accurate key transmission. This work presents a framework for physical-layer security, suggesting potential applications in photonic-based cryptography and secure communications.

During multimode fiber (MMF)-based information transmission, strong and persistent external disturbances can readily induce mode coupling, significantly degrading image reconstruction and posing major challenges for practical applications. To ensure stable transmission, this paper analyzes mode cross-coupling and inter-mode interactions and then proposes a conditional generative adversarial network to learn rotationally speckle patterns projected through a step-index MMF under random bending or swaying perturbations. The method demonstrates exceptional robustness and stability in reconstructing various types of test images experimentally. Those findings contribute to critical theoretical and technological foundations for MMF information transmission, paving the way for further research and practical application deployment.

Structural colors hold significant application value in anticounterfeiting, displays, and smart coatings due to their high stability, eco-friendliness, and dynamic optical response potential. However, conventional fabrication strategies for photonic crystals—such as photolithography and inkjet printing—suffer from limitations including high mask costs, nozzle clogging, lattice defects, and difficulties in scaling production. This study introduces an innovative screen-printing technique to achieve high-fidelity and multicolor structural color patterning based on cholesteric liquid crystal elastomers (CLCEs), overcoming key challenges in controlling the alignment of mesoscopic helical structures and ensuring spatial homogeneity of the photonic bandgap. Crucially, the chiral helical superstructure of CLCEs was investigated, revealing its decisive role in governing the circular polarization properties of the reflected light. The printed patterns exhibit dynamic optical behaviors, including viewing-angle-dependent color shifts, inherent selective circularly polarized reflection dictated by the handedness of the helix, and reversible mechanochromic responses under strain. Furthermore, integration of photochromic spiropyran enables multistimulus-responsive color and fluorescence switching under light and thermal stimuli, as well as ultraviolet-tunable (645 to 685 nm) random lasing emission. This work demonstrates that screen-printed CLCEs, with their excellent substrate compatibility and scalability, constitute a promising platform for next-generation anticounterfeiting labels, smart packaging, and flexible photonic devices.

True random numbers occupy a core role in the field of encryption and security by virtue of their properties such as unpredictability and independence. In this paper, we propose a high-speed physical random number generator based on a dual-emission random fiber laser. The system improves the spectral bandwidth characteristics of the output signals by adjusting the pump power and the feedback length of the single mode fiber. This study effectively suppresses the autocorrelation feature by performing exclusive-OR operations on the forward and backward random laser signals, and obtain the random number sequence with a generation rate of 20 Gbps by post-processing with high-order finite difference and least significant bit extraction. In order to verify the practical application performance, we apply the random sequence as encryption key to digital image encryption, and the experimental results show that the generator has both theoretical security and practical application value.

Random optical systems have been widely investigated due to their abundant physical effects, including numerous degrees of freedom and equilibrium states. Whereas the boundary perturbation can disturb the dynamical behavior of the equilibrium states and lead to a series of unexplored evolution, here we unveil the equilibrium transition induced by boundary perturbation in random fiber lasers through introducing a laser-feedback process. In this typical random optical system, the predominant role of random scattering can be manipulated by a laser-feedback process that serves as boundary perturbation, causing the transition of the equilibrium state and output properties of the laser. On this basis, the photon lifetime can also be reduced, presenting huge potential in highly sensitive non-contact sensing with a detectable minimum feedback power of 12.08 fW and a detection distance of 130 km. Our work provides a new perspective in deepening the understanding of intrinsic mechanisms in random systems and broadens the underlying applications, including modal manipulation and high sensitivity measurement.

In the era of advancing mobile and wearable technologies, the evolution of lasers toward flexible deformation is becoming increasingly prominent. This study develops a novel, flexible, and stretchable cholesteric liquid crystal elastomer (CLCE) laser device. This innovative device demonstrates a unique ability to undergo rapid, progressive, and reversible color changes due to force‐induced reactions. Stretch switchable (random or bandgap lasing) and stretch wavelength tunable (560–625 nm) lasers are obtained by introducing the laser dye PM597 into the CLCE. To further extend the control spectrum of laser output wavelengths in flexible systems, this research introduces two laser dyes, namely donor dye PM597 and acceptor dye NB, validating the feasibility of a stretch‐dependent Förster resonance energy transfer flexible laser. By manipulating the stretching force to drive the movement of the CLCE bandgap, our flexible laser device dynamically shifts its lasing output from 560 to 750 nm. Leveraging the CLCE's exceptional mechano‐chromic and mechanical properties, a visual interactive device for real‐time monitoring of human joint movements is designed. This flexible CLCE, as an elastic functional soft material, holds significant promise for applications in smart wearables, soft robotics, and human‐machine interfaces.