In this paper, a series of low band gap bithiophene-based copolymers were designed and synthesized through direct arylation polymerization using a palladium catalyst. The band structures of the five polymers were determined by quantum mechanical calculation employing Density Functional Theory (DFT) in the periodic Boundary Condition (PBC) using the HSE06/6-31G basis set. The polymers were characterized using 1H NMR, FT-IR, GPC, UV-vis and cyclic voltammetry. The five polymers have an energy gap below 2.95 eV and have broad absorption in the visible region. The experimental results support the theoretical prediction. The fluorescence lifetime of the polymers, P(BT-PH), P(BT-CZ), P(BT-FLN), P(BT-ANT) and P(BT-TPA) was monitored using Time-Correlated Single Photon Counting (TCSPC) in CHCl3. We report on the third-order nonlinear optical (NLO) properties of the copolymers, which were assessed using the Z-scan method with a nanosecond laser beam at 532 nm. The copolymers P(BT-PH), P(BT-CZ), P(BT-FLN), and P(BT-TPA) were found to have nonlinear absorption coefficients of 3.85 × 10−10, 2.87 × 10−10, 2.99 × 10−10, and 3.01 × 10−10 m W−1, respectively. The polymers exhibit better optical power limiting behavior at 532 nm because of the donor–acceptor scheme. This optical power limiting behavior positions these materials as promising candidates for integration into next-generation photonic devices, including laser protection systems, optical sensors, and nonlinear optical switches.

Optical nonlinearity and laser protection potential of transition and rare earth doped YCrO4 nanoparticles

Abstract In this study, the laser ablation mechanisms of porous silicon nitride under different gas environments and airflow velocities were compared. The high‐temperature pyrolysis characteristics of silicon nitride were integrated with thermal radiation principles to elucidate the “high‐temperature ring” recorded by thermal imaging cameras during ablation. According to the dynamic evolution of temperature distribution, the temperature inflection point corresponded to the ablation initiation time. The results revealed ablation initiation times of 2.0 and 0.7 s in air and nitrogen, respectively. A comparative analysis of the morphology and spectral characteristics of silicon nitride, subjected to short‐time laser irradiation in different gaseous environments, revealed the formation of an oxide layer, whose reflectivity was 20.6% higher than that of the original material, in air. This oxide layer formation resulted in the later initiation of ablation, the formation of smaller pit diameters, and in oxygen‐free ablation‐induced depths that exceeded those observed in air environments. Laser ablation experiments under high‐speed airflow revealed that unlike the porous ablation morphology observed in static air, higher oxygen‐content dendritic products formed under high‐speed airflow. As airflow velocity increased from 0 to 374 m/s, the ablation pit diameter decreased from 11.2 to 6.7 mm. This study provides a reference for evaluating laser damage characteristics and laser protection capabilities of porous silicon nitride. In addition, it reveals the severe high‐temperature ablation behavior of silicon nitride used as antenna radomes in high‐speed aircrafts.

Abstract : The Laser Protection Security System based on ESP8266 is an IoT-enabled solution designed to safeguard restricted areas by detecting unauthorized intrusions using a laser beam and photo sensor mechanism. The system functions by projecting a laser across the secured zone onto a light-dependent resistor (LDR) or photodiode sensor, which continuously monitors the presence of the laser beam. When the beam is interrupted by an object or individual, the sensor detects a change in light intensity, prompting the ESP8266 microcontroller to trigger an alert. Alerts are provided through sound (buzzer) and visual (LED) indicators, and remote notifications can be sent via Wi-Fi to connected devices or apps (such as Telegram or Blynk). This project combines laser-based detection with the wireless capabilities of ESP8266 for real-time monitoring and remote management, offering a scalable, low-cost, and energy-efficient security solution easily integrated into smart home or industrial systems. The system is highly accurate, responds rapidly to intrusions, and can be expanded for broader coverage. However, its effectiveness depends on clear line-of-sight and stable Wi-Fi connectivity, and it requires regular calibration to maintain reliability. Keyword: Nodemcu ESP8266 board Laser module, LDR sensor module, LED bulb, 100 Ohm resistor, Buzzer, Breadboard Jumper wires.

High energy laser protection performance and mechanism of ceramic nanofiber membranes

Developing ceramic coatings with high reflectivity, emissivity, and mechanical robustness is critical for enhancing laser protection and thermal management in various optical precision instruments and engineering equipment. However, insufficient optical and mechanical performance causes heat accumulation and fracture under thermomechanical stress that can lead to catastrophic failure. Herein, a scalable ZrO2-Al2O3 heterostructured coating featuring anti-laser ablation, thermal management, and toughness is fabricated via a facile yet effective strategy. The multiple scattering of the micro-convex structure on the coating surface and the refractive index mismatching at the heterogeneous interface enhance its reflectivity to 92% (780-2500nm), while the enlarged effective radiation area improves its emissivity to 0.93 (8-25µm). The combination of high reflectivity and low thermal conductivity of 0.6W/(mK) enables the coating to achieve a laser damage threshold of 637Wcm-2 for 35 s, reducing the damage depth by 35.46% compared to a single Al2O3 coating. Notably, the fracture toughness of the coating reaches 6.77 MPam1/2 due to the synergistic effects of zirconia phase transformation toughening and heterogeneous interface energy absorption. These characteristics make the ZrO2-Al2O3 heterostructured coating potential protective materials for various laser protection and thermal management applications.

While silica aerogels have emerged as promising thermal management materials, their practical applications under extreme conditions such as ultrahigh-energy laser irradiation or thermal shocks exceeding 2000 °C are fundamentally limited by catastrophic thermal insulation failure and mechanical instability. Herein, we report a breakthrough multiphase subcrystalline silica aerogel (MSC-SA) architecture engineered through interfacial-induced crystallization with quartz fibers. By implementing a "inter-layered insulation/in-plane conduction" design paradigm, the MSC-SAs can achieve a feature of extreme thermal anisotropy─combining unprecedented axial insulation with ultraefficient radial heat dissipation. This unique thermal management strategy enables the simultaneous achievement of record-high laser damage resistance with a threshold of 3.0 × 104 W·cm-2 and protection duration exceeding 5 min, exceptional thermal stability of an ultralow thermal expansion coefficient of 1.0 × 10-6 °C1- at 1200 °C, and remarkable mechanical robustness evidenced by interfacial shear strength of 43.7 MPa and compressive strength of 32.0 MPa at 95% strain. Our proposed MSC-SAs are ideal for thermal superinsulation materials capable of withstanding extreme environments, particularly in advanced defense applications against high-energy laser threats.

Multifunctional-layer composite coatings with synergistically enhanced laser protection performance

A VO2 functional gradient film with low threshold and high infrared switching efficiency for laser protection

Wavefront coding imaging offers a promising path for laser protection of electro-optical imaging systems. However, current designs mainly focus on a single wavelength, since achieving diffractive achromats for dual requirements of optimal imaging and laser protection capabilities has been challenging. In addition, their laser protection effect is merely predicted rather than validated through actual laser-damage experiments. In this Letter, we report a broadband laser-damage-resistant diffractive camera with high imaging quality whose laser protection capability is verified in laser-damage test. A deep optics framework is constructed to co-design the learnable diffractive optical element (DOE) and image recovery neural network (NN) in an end-to-end manner. The NN is developed with two stages to maximize the restoration quality of the blurred images with variable laser glare. We fabricated the DOE using lithography. Simulation and experiment results both demonstrate that the diffractive camera can reduce the peak intensity of laser on sensor in spectrum of 473-688 nm by over 99%, thereby enhancing the laser-damage threshold by two orders of magnitude. Meanwhile, it also maintains high imaging quality of a typical peak signal-to-noise ratio exceeding 24 dB. The anti-laser camera renders great potential in imaging scenarios that may involve lasers, such as autopilots, drones, and security mentoring.

The escalating demand for laser protection in military, industrial, and commercial sectors has intensified the pursuit for advanced optical limiting (OL) materials capable of safeguarding against high-intensity laser threats. Despite the progress, current OL materials are beset with challenges such as low linear transmittance, narrow operational bandwidths, and inadequate response speeds, which hinder their effectiveness in practical applications. In this work, an organometallic hybrid perovskite of 3-(fluoropyrrolidinium)MnCl3 demonstrated significant reverse saturable absorption properties, with an ultralow starting threshold of 9 mJ/cm2 and a substantial third-order nonlinear absorption coefficient of 4.1 × 10-5 m/W at 532 nm. Combined femtosecond transient absorption spectroscopy and density functional theory (DFT) calculations revealed that the strong nonlinear optical response originates from an excited-state absorption-dominated carrier dynamics process. This work establishes a novel material platform for developing high-sensitivity laser protection devices.

MXenes, as emerging class of two-dimensional (2D) materials, has garnered considerable attention in both optical and electrical domains. In this study, the MXene (V2C) was synthesized by etching the MAX-phase precursor (V2AlC) using a mixture of hydrofluoric acid (HF) and hydrochloric acid (HCl), followed by intercalation with tetrabutylammonium hydroxide solution (TBAH). Furthermore, V2AlC and V2C nanosheets were fabricated via the liquid-phase exfoliation (LPE) method, and their nonlinear absorption (NLA) properties were systematically investigated across the ultraviolet (UV) to short-wave infrared (SWIR) band. The results demonstrated that 2D V2AlC nanosheets exhibited higher two-photon absorption (TPA) coefficients ([Formula: see text], lower OL thresholds, and larger TPA cross sections ([Formula: see text] in the SWIR band. In contrast, V2C nanosheets, formed after etching, exhibited superior TPA performance in the UV band, displaying distinctly different nonlinear optical (NLO) behaviors. These findings suggest that both materials possess outstanding optical limiting (OL) performance, with each material offering distinct advantages at specific wavelengths. Overall, V2AlC and V2C nanosheets hold great promise as advanced OL materials for applications in optical component protection, laser protection for the human eye, and optical filtering.

BACKGROUND: Laser processes—especially high-power ones—are usually associated with reflected and scattered radiation of various spectra and increased light intensity, which have not yet been studied in detail. Due to the development of process equipment, the development and widespread use of manual laser processing systems, and the growth of laser power, the studies of collateral radiation in laser processes are becoming particularly relevant. AIM: To determine the spectral ranges and the intensity of reflected and scattered laser and collateral radiation during basic laser processing of various metals and alloys. MATERIALS AND METHODS: We tested carbon steel (С345), stainless steel (AISI 321), a titanium alloy VT6 (Grade 5), and an aluminum alloy (AlMg6). The tests were performed on a special test bench using a special method. CONCLUSIONS: The tests showed that the maximum permissible levels and intensity of reflected and scattered laser radiation, UV-C radiation, and—in some cases—UV-B radiation were exceeded in all studied processes. The results indicate the need to use both laser and UV radiation protection equipment when processing the specified materials in the studied processes.

Titanium based perovskite materials with nonequilibrium surface oxygen vacancy compatibly realize laser stealth and laser protection

This fundamental understanding of molecular structure-NLO property relationships provides critical design principles for next-generation optical limiting materials, quantum photonic devices, and ultrafast nonlinear optical switches, addressing the growing demand for high-performance organic optoelectronic materials in laser protection and photonic computing applications. In this study, it was observed that selenophene-incorporated fused D-A-D architectures exhibit a remarkable enhancement in two-photon absorption characteristics. By strategically modifying the heteroatomic composition of the Y6-derived fused-ring core, replacing thiophene (BDS) with selenophene (BDSe), the optimized system achieves unprecedented NLO performance. BDSe displays a nonlinear absorption coefficient (β) of 3.32 × 10-10 m/W and an effective two-photon absorption cross-section (σTPA) of 2428.2 GM under 532 nm with ns pulse excitation. Comprehensive characterization combining Z-scan measurements, transient absorption spectroscopy, and DFT calculations reveals that the heavy atom effect of selenium induces enhanced spin-orbit coupling, optimized intramolecular charge transfer dynamics and stabilized excited states, collectively contributing to the superior reverse saturable absorption behavior. It is believed that this molecular engineering strategy establishes critical structure-property relationships for the rational design of organic NLO materials.

Abstract The widespread application of laser technology has increased the demand for laser‐protective materials, and rare‐earth oxides are potential materials in laser protection research due to their unique physical and optical properties. This study investigates the electronic structure, dielectric, and optical properties of a series of cubic rare‐earth sesquioxides (RE2O3, RE = Gd, Dy, Er, Yb, Lu, Sc, and Y) using first‐principles calculations. The dielectric and optical properties of RE2O3 materials in the visible‐to‐near‐infrared (VIS‒NIR) wavelength range are clarified to be governed by electronic transitions. Despite similar spectral characteristics, the peaks in the spectra of dielectric function, complex refractive index, reflectance, and absorption coefficient systematically exhibit blue shifts with increasing RE3+ cationic radius in the same group, or decreasing RE3+ cationic radius in the same period, which is inherited from the variation in band gap size. And, a guideline to search for RE2O3 materials with high reflectance in the NIR wavelength range is proposed to be correlated with high refractive index and low band gap. These findings elucidate the fundamental mechanisms governing the dielectric and optical properties of rare‐earth oxides within the VIS‒NIR range, and provide useful guidelines for the screening and optimizing RE2O3‐based materials for laser‐protective applications.

Abstract With the continuous development of laser weapons, satellite structures face severe challenges in laser protection. Traditional satellite structures often use lightweight materials to reduce weight and increase payload, but their thermal conductivity is poor, making it difficult to effectively dissipate the heat generated by the laser, leading to a rapid rise in surface temperature and ultimately causing structural damage or functional failure. Phase change materials (PCM) can absorb a large amount of heat during the phase change process with almost no change in temperature, making them very suitable for absorbing the heat generated by the laser; heat pipes have the characteristic of efficient heat conduction and can quickly dissipate heat to reduce the surface temperature of the structure. Therefore, combining PCM and heat pipe technology can develop efficient and lightweight laser protection systems to effectively resist the threat of laser weapons. This study established a simplified two-dimensional thermal protection model containing heat pipes and paraffin and used software for numerical simulation to analyze the temperature field distribution of materials under laser loading. The model considers the Gaussian distribution characteristics of the laser, the latent heat absorption of the phase change material, and the efficient heat conduction of the heat pipe. The results show that the temperature at the laser irradiation point first increases and then decreases over time, and the temperature gradient is greater near the laser source. The equivalent thermal conductivity of the heat pipe has a significant effect on the temperature field distribution, and increasing the thermal conductivity can reduce the peak temperature at the laser action point, reduce the temperature gradient, and improve the stability of the overall structure.

Construction of intelligent laser protection films containing vanadium dioxide with high stability

Abstract With the rapid development of laser technology, the safety of human and equipment is increasingly threatened by high‐power laser. However, there are not any high‐power laser protection materials without flame and smoke during irradiation. In this study, we investigated a series of RE 2 Ti 2 O 7 (RE = Y, La, Sm, Eu, Yb) ceramics with high reflectivity and low thermal conductivity and evaluated their laser ablation behaviors. The results showed that all RE 2 Ti 2 O 7 have high reflectivity comparable to that of metals, and their thermal conductivity is lower than 8YSZ. Laser ablation results showed all coatings were intact after irradiation under 500 W/cm 2 for 10 s. Even after irradiation under 1000 W/cm 2 for 10 s, no significant changes were observed in the Y 2 Ti 2 O 7 and La 2 Ti 2 O 7 coatings. Further exploration determined that the protection threshold of Y 2 Ti 2 O 7 was 84 s while that of La 2 Ti 2 O 7 was 163 s, indicating its superior laser protection capability. In conclusion, La 2 Ti 2 O 7 shows significant potential in high‐power laser protection.

Abstract With the rapid advancement of laser weaponry, their exceptional strike capabilities and high energy density have become an increasing threat in modern warfare, necessitating the development of effective laser protection strategies. This study presents a novel symmetric, multicomponent, all‐dielectric high‐reflection film structure. By integrating multicomponent materials, the design enhances laser damage resistance, while its symmetric architecture enables the transformation from films to coatings using micro‐optical reflectors (MOR). The resulting room‐temperature‐cured coating achieves a high reflectance of 94.7% at 1080 nm. After 20 s of laser irradiation at 1.5 kW cm−2, the backside temperature increased by only 118.1 °C, with no visible signs of ablation. Even under extreme irradiation for 3 min, the coating demonstrated exceptional durability. These findings highlight the innovative application of optical reflective films for laser protection and underscore their potential for deployment on complex surfaces such as satellites, aircraft, and optoelectronic countermeasure systems.