Laser Research Institute

We present a temperature-tuning optical parametric amplifier (OPA) based on a BaGa₄S₇ (BGS) crystal, which enables alignment-free spectral tuning across the mid-infrared (MIR) wavelength range. Utilizing the temperature-dependent birefringence of BGS, continuous wavelength tuning is realized without mechanical adjustment of the crystal phase-matching (PM) angle. With fixed PM angles of θ = 4.1° and 11.1°, the system achieves broadband spectral tunability from 5.8–7.35 μm and 7–10.3 μm, respectively, over a crystal temperature range of 20–160 °C, covering molecular fingerprint regions. The alignment-free tuning mechanism ensures excellent beam-pointing stability, thereby addressing a key limitation of conventional angle-tuned OPAs. These results demonstrate that BGS serves as a flexible platform for temperature-controlled MIR light sources, offering a scalable solution for achieving spectral agility in ultrafast laser systems. This approach holds promise for applications such as molecular spectroscopy, where it eliminates the need for mechanical complexity and alignment procedures.

Despite substantial advances in understanding urinary stone formation, including mechanisms of calcium phosphate (CaP) crystallization, tissue infiltration, and stone development via Randall’s plaques, the global prevalence of urolithiasis continues to rise and current knowledge has only limited impact on clinical outcomes. This study focuses on the CaP phase, particularly brushite, and re-examines its role under physiologically relevant conditions as a potential key to more effective prevention. The aim was to elucidate how reactions proceed near the surfaces of brushite crystals that can present in urine, and how these reactions are modulated by coexisting proteins, using wide-field optical observation combined with quantitative modeling. Single-crystal brushite was immersed in a model solution pre-equilibrated with calcium oxalate monohydrate (COM), and the time evolution of the Ca2+ concentration field associated with brushite dissolution was evaluated by in situ microscopy and one-dimensional diffusion analysis. The results demonstrated that brushite dissolution generates a critical Ca2+ supersaturation zone extending several hundred micrometers from the crystal surface, within which COM nucleation occurs. Upon addition of bovine serum albumin (BSA) as a model protein, the average growth of COM was inhibited, whereas the local frequency of COM nucleation increased markedly in regions of the brushite surface with high step and kink densities, yielding dense, rigid COM–brushite composites. These findings indicate that brushite crystals function not merely as apatite precursors, but as localized “reaction fields” that spatially control calcium oxalate nucleation, aggregation, and consolidation. Furthermore, urinary proteins can, through these fields, act not only as inhibitors but also as local promoters of stone formation.

When Distributed Fiber Optic Vibration Sensing (DVS) systems are used for perimeter security intrusion detection in complex industrial environments, existing recognition models suffer from insufficient adaptability, high computational overhead, and high latency. This paper proposes the MNV4-LDA end-to-end recognition method, which integrates the lightweight feature extraction capability of MobileNet-V4 (MNV4) with the advantages of supervised dimensionality reduction of Linear Discriminant Analysis (LDA), constructing a framework from feature enhancement to dimensionality reduction and then to classification. The experiment targets three types of events: background noise, mechanical operations, and human walking. Tests based on 6000 groups of datasets show that the number of parameters of this method is reduced from 632.22M to 2.38M, with a reduction rate exceeding 99.6%. The recognition accuracy reaches 98.28%, 4.67% higher than that of MNV4, and the single-sample inference time on the CPU is 127.0ms. Moreover, no denoising preprocessing is required. This method effectively solves the edge deployment challenges of traditional models, balances efficiency and stability, and provides a practical solution for the edge application of DVS systems in perimeter security.

The reliable detection of entanglement plays a crucial role in the construction of quantum networks. The conventional entanglement witness (EW) method has high requirements for measurement device and relies on reliable implementation of the measurement. With unreliable measurement device, EW process can be easily attacked by eavesdroppers, which can lead to incorrect entanglement detection results. Therefore, a feasible and secure measurement device independent entanglement witness (MDIEW) method is desired for constructing quantum networks. Here, we detect the continuous variable entanglement by a MDIEW in a quantum network. It is demonstrated that the conventional EW method can be affected when the local oscillator intensity is changed, while the MDIEW method can detect entanglement between users without being affected. Our results provide a trustworthy method to detect entanglement, which is an important step for constructing secure quantum networks.

Liquid droplets' interaction with textured polymer surfaces is key to ensuring their long-term performance in humid environments. Surface wetting properties affect polymer durability by influencing hydrolysis, oxidative degradation, and microbial growth. This study investigates the wetting behavior of microtextured polydimethylsiloxane surfaces replicated from metal molds obtained via micromilling and femtosecond laser texturing. Surface features with periods of 60, 100, and 750 μm were fabricated, and a modified sessile drop method was applied to determine static, advancing, and receding contact angles on horizontal and vertical substrates. Particular attention was paid to wetting hysteresis and anisotropic droplet deformation during spreading. Despite significant differences in texture size, all surfaces exhibited comparable advancing contact angles up to 165° and equilibrium angles around 102°, close to those of untextured polydimethylsiloxane. The Wenzel model was applied for theoretical prediction of contact angles but yielded results consistent with advancing rather than equilibrium values, indicating its limitations at this scale. The study concludes that classical wetting models become ineffective when droplet dimensions approach those of surface features. In such cases, hydrodynamic models or finite element simulations considering actual channel geometry are recommended for accurate characterization. The findings are relevant for microfluidics, biomedical device design, and development of self-cleaning surfaces.

Abstract Picosecond petawatt laser-driven X-rays provide a powerful diagnostic tool for high-energy-density physics with high spatial resolution. In such experiments, point-projection backlighting is employed, where a quasi-point X-ray source is routinely generated by laser irradiating a wire target. The imaging spatial resolution is inherently related to the source size. This leads to a trade-off between spatial resolution and laser-to-target interception, and thus inhibits the improvement of source brightness. Coded-source radiography provides an alternative approach, which uses structured source target with high interception to form coded images, and reconstructs the high-resolution images based on source position function. Here, we demonstrate the generation of an annular X-ray source driven by a picosecond laser. By using a large-diameter target to fully intercept the laser, we achieved an annular X-ray source with the brightness several-fold higher than that of the conventional quasi-point source produced by a wire target. Coded-source radiography with this annular source maintained a high spatial resolution, and yielded a significantly higher signal-to-noise ratio (SNR) than the conventional point-projection imaging. Our findings highlight that this technique can provide clearer and more detailed radiography for high-energy-density physics experiments conducted in challenging environments.

Kerr resonator is one of the most popular platforms to produce optical frequency comb and temporal cavity soliton. As an essential method for investigating the nonlinear dynamics of Kerr resonators, traditional numerical simulations rely on solving the Lugiato-Lefever equation (LLE) using the split-step Fourier method (SSFM), which is computationally intensive and time-consuming. To address this challenge, this study proposes a recurrent neural network model with prior information feedback, enabling efficient and accurate prediction of soliton dynamics in Kerr resonator. With the acceleration of graphics processing unit (GPU), the computational efficiency improved by 20 times. We compared various recurrent neural networks and found that the gated recurrent unit (GRU) network demonstrated superior performance in this task. This work highlights the potential of artificial intelligence (AI) for modeling nonlinear optical dynamics in Kerr resonator, paving the way for designing optical frequency comb and generating ultrafast pulse.

BACKGROUND: The efficiency of a contemporary gas turbine engines can be improved by increasing the operating temperature inside the engine, resulting in extreme thermal stress on materials. The temperature of combustion products inside aircraft engines can reach temperatures exceeding the melting points of the alloys used, limiting their applications. To protect working parts, thermal control coatings and cooling systems with punch holes are used. Laser perforation is a promising method that provides high precision and cost-effectiveness of hole punching processes for combustion liners with thermal control coatings. The development and improvement of such technologies is relevant for the aerospace industry and general mechanical engineering, where a balance between quality, performance, and cost is required. AIM: To develop an efficient laser perforation solution for combustion liners with thermal control coating, providing an optimal combination of precision, surface quality, and performance. The paper analyzes and compares existing punching methods to support the choice of the best possible technology. METHODS: The paper provides a technical analysis of existing perforation solutions for aerospace and general industrial applications. Punching options for combustion liners are considered based on data from open sources. The experimental part included the use of a serial five-axis laser processing machine SLP520 with a fiber laser. RESULTS: Analysis showed that laser perforation outperforms alternative methods in terms of accuracy and processing speed. Optimal laser radiation parameters ensure the lowest thermal effect on the thermal control coating and high repeatability. Experiments showed that a long-focus lens ensures fixed diameter and shape of the holes and a boron nitride protective paste helps prevent splashes around the holes. CONCLUSION: Laser perforation is an effective punching solution for cooling holes in combustion liners with thermal control coating. The proposed technology provides high precision, quality, and repeatability, making it preferable for aerospace applications. Further research may be aimed at studying the effect of protective paste on the thickness of the modified layer.