Applied Physics B最新文献

The design features MXene–SiO₂–Fe-based metasurfaces to enhance efficient absorption across a wide range of the solar spectrum. The proposed investigation of the absorber is essential for an efficient thermal energy harvesting solution and a broad frequency range of both infrared and visible light absorber architectures. The findings derived from computational and numerical analyses will assist in identifying optimal material geometries for effective wideband infrared and visible UV light absorbers and thermal harvesting structures. The entire structure is evaluated against interference theory-based calculations to ascertain effective absorption across the solar spectrum. The basic parameters, such as refractive index, permittivity, permeability, and impedance, were presented for the proposed structure to identify its metamaterial effect. This study introduced a double-multilayer structure of SiO₂ and Fe as the metamaterials. MXene is a resonator in the THz frequency range at an angle of incidence of 60° degrees, within the range of plasmonic insensitivity. The absorption capacity reaches > 90%, making the proposed structures suitable for harvesting solar energy. In addition, the simulated results show high thermal radiation and high thermal efficiency with increasing temperature, emphasizing the importance of simulating MXene as a resonator. The proposed structure can be crucial for designing highly efficient parasitic solar absorbers for multiple solar and thermal absorption applications.

This study systematically investigates the beam quality degradation in conventional broad-area semiconductor lasers, which arises from the excitation of higher-order transverse modes under high injection currents. To address this fundamental limitation, we propose and demonstrate a novel lateral surface grating structure integrated on both sides of the ridge waveguide. Through comprehensive numerical and experimental analyses, we first examine the optical loss characteristics induced by the grating structure. Subsequently, we explore the mode modulation mechanism by systematically varying the separation distance between the gratings and the ridge waveguide. Our results reveal that reducing this critical distance significantly enhances the grating's ability to suppress higher-order transverse modes. This improvement manifests in two key aspects: (1) a notable reduction in the transverse divergence angle in the far-field pattern, and (2) a more concentrated energy distribution in the near-field profile. These findings demonstrate the effectiveness of our proposed approach in achieving superior beam quality while maintaining stable laser operation.

We present a bilayer design in a terahertz metamaterial consisting of two triangular resonators that can manipulate broadband cross-polarization conversions and three-band unidirectional reflectionlessnesses by using the phase-change material VO₂ for the incidence of linearly and circularly polarized waves. When VO₂ is in metallic state, the broadband cross-polarization conversion effects are realized in range of 0.41 THz(sim )0.54 THz and the polarization conversion ratio reaches (sim )1. We also find that the proposed structure has the ability to convert linear polarizations into circular polarizations at 0.39 THz and 0.59 THz. When VO₂ is in insulator state, three-band unidirectional reflectionlessnesses are attained at 0.50 THz, 0.72 THz and 0.81 THz based on Fabry–P({mathrm{acute{e}}})rot resonant coupling between the upper and lower triangular resonators.

A corner cube retroreflector (CCR) laser boasts an exceptional anti-misalignment property, and the limiting incident angle of the CCR determines its anti-misalignment capabilities. To facilitate an efficient analysis of the limiting incident angle of a CCR, we present an analytical expression for its three side reflection angles. Subsequently, we analyze the anti-misalignment limiting incident angle of the CCR, considering its bottom surface shape and refractive index. Theoretical analysis and simulation results indicate that when the refractive index (n₁) ≥ 1.22, the larger the value of n₁, the larger the limiting incident angle. When n₁ ≥ 2.175, the refractive index is no longer a limiting factor for the limiting incident angle. Furthermore, for the bottom surface shape of the CCR, the smaller the height–radius ratio of the CCR, the larger the limiting incident angle allowed by the CCR, which results in better anti-misalignment capability. This study provides a concise and efficient model for analyzing the anti-misalignment ability of the CCR. Additionally, it establishes a theoretical foundation for calculating the limiting incident angle of the CCR when dealing with incident light featuring a small optical field diameter.

In this paper, we present a high-efficiency dual-diode-pumped Tm:LGGG disordered crystal laser using in-band pumping architecture for the first time. The room-temperature absorption and emission spectral properties of the Tm:LGGG crystal were characterized across the spectral rang of 1500–2300 nm. A maximum output power of 11.5 W and a slope efficiency of 57.1% concerning absorbed pump power were achieved in continuous-wave regime. Moreover, the beam quality factor M2 was estimated to be 1.9 at above output power. In the acousto-optically Q-switching regime at a repetition rate of 1 kHz, a pulse energy of 5.71 mJ and a pulse width of 102 ns were achieved, resulting in a peak power of 55.98 kW.

The paper investigates the degradation of beam quality in spectral beam combining (SBC) systems with dual-gratings caused by defects in diode laser arrays (DLAs), focusing on the combined effects of beam linewidth, divergence angle, and beam deflection. A comprehensive model is developed to analyze how these defects affect the wavelength-locking mechanism and beam propagation, thereby degrading the output beam characteristics. The results reveal that the dual-grating configuration effectively mitigates angular broadening induced by linewidth dispersion. A linewidth of 1 nm results in a mere 8% reduction in the peak intensity of the combined beam, concomitantly leading to a 0.5 increase in the β factor. Although beam divergence exacerbates the degradation of beam quality, beam deflection is the dominant factor. A deflection angle of 3 mrad results in a 38% reduction in peak intensity and a 2.6 increase in the β factor, underscoring the necessity of controlling beam deflection. We hope this work provides critical insights into the interplay between DLA imperfections and SBC performance, offering a theoretical foundation for optimizing high-power, near-diffraction-limited beam combining systems.

In the framework of the Argon Power Cycle, millisecond-pulsed hydrogen gas injections into a high-pressure, room temperature nitrogen or argon ambient are investigated. Instantaneous Rayleigh scattering is used to quantify the hydrogen mole fraction in the ensuing jets. A readily available HDEV injector with a straight 0.55-mm orifice and an inward-moving needle controls the mass flow into the constant-volume setup in accordance with (compressible) choked flow theory. The linear dependence of the Rayleigh signal on the number density is experimentally validated and the validity for the assumed constant number density throughout the mixing jet is presented. The evolution of mole fraction is presented for both nitrogen and argon ambient gases, and pressure ratios of 2.5 and 10. Quasi-steady behavior is shown in both axial and radial direction, while self-similar behavior is already observed 3 mm from the nozzle ((x/d_textrm{e} = 5.5)).

Cylindrical shells, such as gas pipes and wind turbine towers, are common structural components. Ensuring the stability of these structures necessitates accurate measurement of their three-dimensional (3D) operating deflection shapes (ODSs). Laser Doppler Vibrometry (LDV) and Digital Image Correlation (DIC) are two prevalent optical measurement techniques. Measuring radial vibrations of a cylindrical shell only using a 1D scanning laser Doppler vibrometer (1D-SLDV) poses a challenging yet practical problem, as the cost of a 1D-SLDV is significantly lower than that of a 3D-SLDV. Addressing this issue, the authors previously proposed a scheme for measuring radial ODSs of a cylinder via mono-laser scanning. By leveraging the geometric relationship, the displacements measured by the laser at each point are transformed to obtain radial displacements. Although it was proven through numerical simulation using the finite element (FE) method, experimental validation via 3D measurements is critical and still pending. To ensure the reliability of this scheme, it is experimentally validated in this study through comparison with the actual radial ODSs captured by 3D DIC. To validate the accuracy of the corrected radial ODSs, the cosine similarity (CS) values across the radial ODSs obtained through the FE method, LDV, and DIC are calculated, demonstrating a high degree of similarity. Particularly, the LDV and DIC yield consistent radial ODSs, with their CSs exceeding 95% for each excitation frequency.

High-average-power, megawatt-peak-power solid-state lasers with high beam quality have garnered significant attention in the field of laser cleaning applications. This paper presents a 1064 nm diode-pumped Nd: YAG master oscillator power amplifier (MOPA) system employing a multi-mode stable resonator. The designed resonator exhibits minimal beam quality variation when operating in the second stability zone, combining excellent power scalability with remarkable multi-mode stability. A flexible beam delivery system incorporating a 400-µm-core-diameter optical fiber demonstrates exceptional performance, achieving coupling efficiency exceeding 95% at a maximum average output power of 701 W with 20 kHz repetition frequency. Furthermore, it reaches a peak power of 1.0 MW at 12 kHz repetition frequency while maintaining 588 W average power output. Experimental results confirm that this innovative design successfully balances high-power operation with beam quality preservation and efficient energy transmission.