Applied Physics B最新文献

Spatially resolved, quantitative laser diagnostics are needed to understand high-temperature and high-speed flow fields. To that end, a spectrally resolved laser-induced fluorescence diagnostic targeting nitric oxide (in bath gases of Ar and N₂) was developed and validated in a series of static cell and shock tube experiments. Also, a spectrally resolved fluorescence model was created to simulate the underlying processes of diatomic spectrally resolved fluorescence and quantify the maximum theoretical measurement rate under various conditions. The diagnostic was validated from 295–1350 K and 2.1–47.0 kPa, and validation experiments showed good agreement with known values—a 3.0% and 5.5% average error in temperature and pressure (for collisional-to-Doppler width ratios greater than 0.30), respectively.

Precise measurement of micro-curvature enables early detection of issues before they reach critical levels, facilitating preventive maintenance and mitigating the risk of significant economic losses and safety hazards. In this paper, we proposed and experimentally demonstrated an innovative sensor for dual parametric simultaneous measurement based on Sagnac-interferometer (SI) constructed by double-clad polarization-maintaining fiber (DPMF). The sensor is designed using a 2 × 2 coupler to connect the DPMF, forming an optical fiber loop structure while granted with a Fiber Bragg granting (FBG). The experiment proves that the SI exhibits curvature sensitivity of − 89.1 nm/m⁻¹ from 0.062 to 0.176 m⁻¹ and − 179.09 nm/m⁻¹ from 0.186 to − 0.26 m⁻¹ while temperature sensitivity of − 1.65 nm/°C. By adding FBG to realize dual parametric simultaneous measurement. The FBG has showed sensitivities of curvature and temperature are − 6.97 nm/m⁻¹ and 0.009 nm/°C. The coefficient matrix approach is employed to simultaneously measure both curvature and temperature. The sensor exhibits ultra-high curvature resolution of 1.1 × 10⁻⁴ m⁻¹ and achieves dual-parameter simultaneous measurement for curvature and temperature through a simple fabrication process. Its characteristics of high sensitivity and resolution, low production costs, and straightforward manufacturing make its application prospects in industrial manufacturing and aerospace fields broader.

We demonstrate continuous-wave laser operation of a terbium (Tb³⁺)-doped ZBLAN fiber emitting in the green spectral region. Under pumping at 486 nm, laser oscillation at 542 nm was achieved in a 4 m long Tb³⁺:ZBLAN double-clad fiber. A maximum output power of 6.2 mW was obtained with a slope efficiency of 1.2% with respect to the launched pump power and 4.1% not taking into account the transmitted pump light. Versus the actual absorbed pump power, the efficiency is estimated to be comparable to crystalline fluoride hosts. The results represent a significant improvement over previously reported Tb³⁺-doped fiber lasers and highlight the potential of fluoride fibers for compact visible laser sources provided sufficient absorption efficiency can be achieved.

I designed and experimentally performed digital holographic microscopy (DHM) in which a halogen lamp is used as a light source and theoretical two-point resolution is submicron. The DHM system consists of a commercially available optical microscope and a common-path self-reference in-line digital holography system. Quantitative phase imaging of a three-dimensional (3D) object is performed without speckle noise. 3D imaging of an object containing submicron apertures is performed with temporally incoherent thermal light.

Diabetes mellitus (DM) is a group of metabolic diseases characterized by chronic hyperglycemia, which develops due to insulin resistance (T2DM), insulin deficiency, or glucagon overproduction (T1DM). One of the key consequences of hyperglycemia is nonenzymatic glycation of biomolecules, including proteins, lipoproteins, and lipids. The aim of this study was to determine the optical properties of adipose tissue in healthy rats and rats with experimentally induced T1DM using multiwavelength refractometry and spectroscopy, followed by data verification through histological analysis and molecular modeling. Glycation of collagen and phosphatidylethanolamine was shown to lead to expansion and destabilization of their hydration shells. A comprehensive analysis revealed a correlation between optical properties, structural changes in tissues, and their hydration. The differences in the optical properties of abdominal fat, arising from pathological glycation and hydration, could enable the development of label-free optical methods to monitor T1DM in experimental settings. This approach may ultimately support new strategies for predicting, diagnosing, and tracking the progression of T1DM in humans.

We present the first step towards an intelligent thin-disk multi-pass amplifier (I-TDMPA), by simulatively proving the ability of a neural network (NN) for the detection of misalignment. A digital twin of one of our experimental systems was implemented using a specifically developed ray tracing simulation. The digital twin was used to generate more than 200,000 sets of training data to train a neural network (NN) with the goal to be able to determine misalignment of the many optical elements of a multi-pass amplifier in a simulation model, solely by observing the beam. The predictions of the NN agree very well with the simulated misalignments, which confirms the suitability of artificial-intelligence methods to ensure a safe and stable operation of complex optical systems.

Single-pixel imaging (SPI) reconstructs an object’s image via computational methods using a single-point photodetector and a sequence of mask patterns. A fundamental trade-off exists in SPI between the sampling rate and the fidelity of the reconstructed image: while increasing the number of patterns enhances image quality, it simultaneously scales the volume of the measured light intensity data. In this study, we propose a SPI data compression based on audio compression technology, taking advantage of the fact that light intensity data is inherently one-dimensional. Our results demonstrate that the Free Lossless Audio Codec algorithm achieves significantly higher compression ratios than conventional lossless methods based on LZ77 and Huffman coding, without compromising image quality. Furthermore, we show that lossy formats such as MP3 and Ogg Vorbis can achieve even higher compression ratios, albeit with minor degradation in the final reconstruction.

The quintic nonlinear response of fused silica was investigated using a modified z-scan technique and a cubic-quintic propagation model at femtosecond pulse intensities up to (10 mathrm {TW/cm^{2}}). A statistically significant deviation from the purely cubic Kerr response was observed only at the highest intensities. Interpreting this deviation within the perturbative cubic-quintic model yields effective quintic nonlinear refractive indices (n_4=-(4...7)cdot 10^{-6} mathrm {cm^4/TW^2}) at a wavelength of 1033 nm and (n_4=-(8...16)cdot 10^{-6} mathrm {cm^4/TW^2}) at 517 nm. Since plasma-induced refractive effects may contribute to the observed higher-order response, these values should be regarded as the upper bounds of the negative quintic nonlinear refractive index of fused silica. The obtained bounds are approximately 1–2 orders of magnitude lower than the previously reported values.

Temperature dependence of the optical path difference in optically transparent materials is governed by both thermal expansion and thermo-optic effects. Combining both effects with a single parameter, referred to as effective thermal expansion coefficient (α_eff), which measures change in optical path length with temperature. This quantity, α_eff, is important for quantitative characterization of the impact of temperature variations as well as thermal effects on the optical components. This work demonstrates the use of a spectral domain low coherence interferometer (SDLCI) in common path configuration, along with phase sensitive analysis, to measure effective thermal expansion coefficient of fused silica and sapphire samples with sub-nanometer scale optical path length sensitivity. The phase based optical path length retrieval methodology is first established with simulated data and then validated experimentally. Experiments were performed for phase sensitive optical path difference measurements with sub nanometer scale repeatability in using 840 nm wavelength in the temperature range of 35–70 ºC. The experimentally measured values of α_eff of fused silica and sapphire samples are found to be in agreement with the values reported in literature.