Applied Physics B最新文献

In this paper, we analyze the dynamical evolution of physical systems governed by the one-dimensional nonlinear Schrödinger equation, with initial conditions modelled by white noise. We show that first- and second-order Akhmediev breathers emerge in numerical simulations from such random initial conditions, demonstrating that these analytical solutions — typically constructed using the Darboux transformation — are intrinsic properties of the equation and can be regarded as its fingerprint. We further investigate this problem by analyzing the statistics of local intensity maxima and show that second-order breather solutions are also clearly visible in probability density histograms over intensity intervals. To determine their properties, we employ the peak-height formula, which enables precise identification of the frequencies of the two commensurate components that nonlinearly form the breather. The method is validated using two distinct intensity peaks obtained in numerical simulations with different algorithms and evolution steps. Finally, we provide a brief analysis explaining why third- and higher-order breather solutions are difficult to generate from white noise, based on weak perturbations of carefully constructed initial conditions derived from analytical solutions.

Phase-only spatial light modulators (SLMs) are employed in optical systems for various applications. In this article, the main landmarks of SLM-based imaging systems are surveyed. In addition to conventional two-dimensional imaging, these systems are useful for multidimensional imaging, axial sectioning, field-of-view expansion, improved image resolution, imaging through scatterers, and depth-of-field control. The SLMs in this review are positioned in the system aperture and modulate the input light in various ways to achieve different imaging goals. This review begins with the nearly 20-year-old Fresnel incoherent correlation holography system, continues with coded-aperture holography, and progresses to the most recent versions of interferenceless coded-aperture holography systems.

Reduced graphene oxide (rGO) produced by the rapid thermal expansion of graphite oxide is a promising alternative to graphene for applications requiring large volumes and some chemical functionality on the graphene, since this approach offers potentially high yields and throughput. However, the surface area and single layer dispersibility of the resulting rGO powder depends heavily on precursor moisture content, chemistry and morphology, as well as and process parameters that include residence time and quenching rates. While large-scale commercial deployments have been demonstrated, there are currently no real-time diagnostics capable of assessing inline material quality. In this study, we propose time-resolved laser-induced incandescence (TiRe-LII) as a means to derive the real-time relative specific surface area (S_sp) of rGO particles which is expected to be a strong indicator of single sheet dispersibility. The TiRe-LII derived S_sp were found to be consistent in both magnitude and trend to those found through batch gas adsorption measurements analyzed by fitting the Brunauer-Emmett-Teller (BET) isotherm.

2 μm lasers are widely employed in LIDAR systems, photomedicine, and as pump sources for OPOs and mid-IR lasers. Tm:YLF is an optimal laser crystal for a 2 μm laser owing to its good mechanical properties, a negative thermo-optic coefficient, and intrinsic birefringence supporting polarized emission. However, many 2 μm lasers have been reported to exhibit unstable operation with a tendency towards self-pulsation (SP). In this paper, we investigate design parameters influencing the temporal output of a compact diode-laser pumped Tm:YLF 1.91 μm laser for stable continuous-wave (CW) and self-pulsating operation. Different sources of perturbation are discussed as main causes for SP. We introduce a novel pulse attenuation parameter, (delta ), to assess laser stability. We report optical-to-optical slope efficiencies of 35% and 41.5% in stable CW and SP operation, respectively.

Polarization mapping plays a key role in modern photonics, as many advanced optical applications, ranging from vector beam engineering to optical communication and material characterization, rely on precise knowledge of spatial polarization distributions. However, conventional mapping techniques often suffer from limitations such as multi-step measurements, sensitivity to misalignment, or the need for bulky setups, making single-shot and high-resolution polarization mapping particularly challenging. Here, we report a single-shot polarization mapping technique for parallel determination of the polarization change introduced by an unknown optical birefringent element or even device (e.g. q-plates, spatial light modulators). To achieve this, we used a 9(times )9 array of linearly polarized probe sub-beams to capture spatially resolved polarization information in a single measurement, allowing the two-dimensional polarization distribution to be reconstructed from just one data acquisition step. In this way, the measurement time is reduced while high spatial resolution is preserved. To demonstrate the robustness of the technique, we present a measurement with commercially available polarizing vortex plates, which convert linearly polarized light into radially or azimuthally polarized light, and the determination of the polarization response of a commercially available spatial light modulator. The main advantage of the method is its simplicity, achieved without sacrificing efficiency, which makes it readily accessible to any laboratory.

Singular optics is a branch of modern electromagnetics and optics that investigates solutions to Maxwell’s equations that exhibit nontrivial topological features under various boundary conditions. These solutions give rise to light fields containing singularities, points or regions at which certain optical properties, such as phase or polarization, become undefined. Over time, singular optics has evolved into a unifying framework for understanding and engineering optical fields that possess phase, polarization, coherence, and spatiotemporal singularities, each characterized by quantized topological properties. Such structured light fields enable high-dimensional information encoding, robust light–matter interactions, and sensitive probing of complex media, thereby impacting optical communication, imaging, sensing, and materials processing. Parallel advances in theory, fabrication techniques, detection hardware, and computational methods have created a diverse and rapidly expanding landscape, underscoring the need for an integrated and forward-looking perspective. This roadmap synthesizes emerging applications of singular optics across multiple platforms, offering a concise overview of current developments and highlighting key physical concepts, new architectures, and transformative technologies that bridge subfields. In addition to reflecting the insights of leading contributors to these research directions, it also surveys selected recent advances, providing a concise overview of current trends and a foundation for shaping the future of singular optics and its applications.

Photothermal stimulated Raman scattering (PT-SRS) was investigated without a probe beam in addition to the pump and Stokes beams, demonstrating that the thermal lens generated within stimulated Raman scattering (SRS) can be detected on one of the intrinsically involved beams as well. The additional signal contribution led to a twofold enhancement of the resonant SRS signal and allowed for a comparison between SRS and PT-SRS signal contributions when an iris aperture with appropriate size was implemented in front of the detector. Additionally, detailed investigations on the signal-to-noise ratio of both PT-SRS and SRS signals demonstrated that the experimental conditions and requirements predefine which technique is more sensitive and provide a decision-making aid based on available laser parameters and detection schemes.

Near-infrared diffuse transmittance imaging was investigated as a non-radiative real-time imaging technique for localizing solitary pulmonary nodules during pulmonary endoscopy and thoracoscopy combined. Ex vivo experiments on porcine lungs tissue were performed to examine near-infrared light propagation and to assess detectability of embedded optical phantoms. Transmittance measurements at 632.5 nm and 850 nm showed markedly higher signal levels and improved spatial information at 850 nm, consistent with the first NIR window. Tissue optical clearing with commercially available e-cigarettes liquids was used to increase transmitted signal levels and its applicability for the diagnostic method was examined. NIR imaging of tissue samples showed that the bronchial wall causes strong scattering and broadens the illumination spot. Nevertheless, small artificial nodules placed beneath the bronchial wall still produce detectable changes in the recorded images. The results confirm the feasibility of the method for detecting scattering local structures within heterogenous lung tissue. This study’s findings provide a technical basis for further optimization of near-infrared diffuse transmittance imaging as a minimally invasive, radiation-free real-time diagnostic imaging method for solitary pulmonary nodules localization.

A high performance terahertz (THz) metamaterial structure based on graphene is presented, exploiting hybrid dielectric graphene resonances to achieve tunable resonance frequencies. Graphene coated mesa metamaterial structures were designed and fabricated on a single chip, enabling strong electromagnetic field confinement and tunable response without the need for additional metamaterial layers. The proposed architecture provides a compact and efficient platform for tunable THz photodetection and opens new possibilities for next generation graphene based plasmonic devices. The metamaterial unit cells were optimized using CST Microwave Studio simulations to operate at target frequencies of 1.1, 0.9, and 0.8 THz, respectively. Device fabrication was performed on high resistivity silicon substrates via UV lithography and reactive ion beam etching, followed by graphene deposition using chemical vapor deposition (CVD). The electromagnetic responses of the fabricated devices were characterized using a continuous-wave THz imaging system. The effects of graphene thickness and Fermi level on the reflection spectra were investigated, and the hybrid dielectric graphene resonance modes were qualitatively analysed and compared with the experimental results. By integrating graphene conformally onto three dimensional dielectric mesa resonators, enhanced light–matter interaction and tunable hybrid resonances can be achieved. The proposed plasmonic enhanced metamaterial detector provides a promising platform for future bio-THz sensing applications.

Propellant tanks typically operate under low-temperature and high-pressure conditions. However, existing fiber optic sensors often fail to meet the comprehensive and reliable assessment requirements for large-range strain measurements and mechanical performance in such extreme environments. To address this challenge, two types of metallized-packaged fiber Bragg gratings (FBGs) strain sensors were designed and fabricated, demonstrating exceptional suitability for high-precision localized and long-term strain monitoring at ultra-low temperatures. The FBGs were inscribed using a femtosecond laser line-by-line method and securely bonded to a metallic substrate with tin (Sn) solder, ensuring robust strain transfer and enhanced mechanical stability during cryogenic testing. Experimental results demonstrated that the FBG temperature sensors effectively performed temperature sensing in the ultra-low temperature liquid helium (LH) environment (5 K). To evaluate the mechanical performance of the FBG strain sensors in the LH environment, a cyclic load test of 1000 N was first conducted, followed by four overload tests with maximum loads reaching 3000 N. Experimental results demonstrated that the metallized FBG strain sensors exhibited a well-defined elastic region under loads up to 2500 N, characterized by a strain sensitivity of over 1.26 pm/N, and a hysteresis error less than 0.1 nm. Beyond 2500 N, the sensors transitioned into a plastic deformation regime, with the hysteresis error increasing to more than 1.47 nm.