Applied Physics B最新文献

Laser-induced fluorescence spectroscopy was used to determine the concentration of cobalt ions in aqueous solution, in which CH-90 resin was used to chelate the ions to transform the liquid samples into solid ones. The experimental results showed that the fluorescence emission of the ions was significantly enhanced after excited by a low-power semiconductor laser at the wavelength of 447 nm. The limit of detection of 1.0 ng/L was achieved, which was 10,000 times lower than the permissible Co(Ⅱ) content of 0.01 mg/L in drinking water. The fluorescence intensity was proportional to the concentration of cobalt ions with a linear correlation coefficient of R² = 0. 998. The method greatly improved the sensitivity of detection for cobalt element in aqueous solutions.

Ultrafine soot particles emitted from combustion devices and biomass burning are a major particulate pollutant for human health and a major climate forcer. Unprecedented efforts have been made to understand the mechanism of soot formation and the physical, chemical, and optical properties of soot particles at different stages of maturity. Pulsed laser-induced incandescence (pLII) has become a powerful tool for in-situ measurements of soot volume fraction and primary particle size and to investigate the effects of pulsed laser irradiation on soot absorption properties. Experimental studies have confirmed that a high-power laser pulse can enhance the absorption of young soot particles through laser-induced annealing. Previous studies have ascribed the observed changes in soot absorption by pulsed laser irradiation to thermal annealing. In this study, a numerical study was conducted to model the effect of pulsed laser irradiation on the absorption efficiency of soot of different maturities to reproduce the results of a recent double-pulse pLII experiment. The numerical results based on thermal annealing models proposed in the literature failed to capture the enhanced peak LII signals of laser-heated young soot compared to those of un-preheated soot. By assuming the laser-induced annealing of soot particle is attributed to both thermal and photon mechanisms, the modified LII model can reproduce the experimentally observed enhancement in the peak LII signal of laser irradiated soot of different maturities. The findings of this study serve as indirect evidence to support the conjecture that the photon mechanism plays an important role in laser-induced annealing of young soot.

In this paper, a self-calibration photoacoustic (PA) spectroscopy analysis technique based on the idle transmitted light intensity was proposed to resolve the key influence of incident light power on PA signal. To demonstrate this proposed gas sensing technique, methane (CH₄) was selected as the target gas, a photoacoustic spectroscopy (PAS) gas sensor system based on near-infrared distributed feedback (DFB) diode laser emitting at 1653 nm was developed by combining wavelength modulation spectroscopy (WMS) with second harmonic (2 F) signal detection method. Instead of the expensive optical power meter, a low-cost photodetector (PD) is used to measure the transmitted light signal and serves as the reference signal for the normalization of the PA signal. The experimental results show that the measured WMS-PA-2 F/PD signals have a good immune to the large dynamic fluctuations of the incident light power. The Allan-Werle deviation analysis indicated that a detection limit of 42.1 ppb can be achieved with an average time of 244 s, corresponding to the corresponding normalized noise equivalent absorption coefficient (NNEA) of 3.63 × 10^− 9 ({text{c}text{m}}^{-1}text{W}/text{H}text{z}).

We propose a quantum model involving two superconducting qubits (SQs) interacting with a single-mode microwave cavity, influenced by a Kerr nonlinear medium and Ising interaction, within the framework of time-varying coupling (T-VC). The Hamiltonian of the system is determined, and we compute the density operator for both the full system and its subsystems. Physically, the Kerr medium introduces nonlinearity while the Ising interaction between SQs facilitates tunable SQs coupling. The interplay of these mechanisms allows for fine-tuned quantum control, crucial for maintaining coherence and managing decoherence processes. We examine the time evolution of key quantum properties, including SQ–SQ entanglement, SQs–cat field entanglement, and quantum Fisher information, as functions of system parameters. Finally, we investigate the dynamic relationships among these quantum measures, revealing mechanisms that can maximize entanglement and coherence under various parameter regimes.

In this paper, a V₂GeC saturable absorber (SA) is prepared and used to modulate a Tm:YAP laser. In continuous wave (CW) mode, an output power of 2.48 W at 1940.5 nm was achieved with a 15.39 W pump power, corresponding to an optical–optical conversion efficiency of 16.1%. Under passively Q-switched (PQS) mode, an average output power of 663 mW at 1937.4 nm was acquired with an optical–optical conversion efficiency of 4.3%, and a pulse width of 416.7 ns at 129.00 kHz was acquired in the laser stable operation, corresponding to a per pulse energy of 5.1 µJ. These experimental results demonstrate the effective modulation capabilities of the V₂GeC SA in near-infrared laser systems.

This study explores the application of Laser-Induced Grating Spectroscopy (LIGS) for non-intrusive measurements of temperature and water vapour concentration in premixed flames of air with blends of hydrogen and methane under high-pressure conditions. Employing a swirl-stabilized burner, the research demonstrates the capabilities of tracer-free LIGS, using thermal and electrostrictive gratings generated by a 1064 nm Nd:YAG laser, to measure local temperatures and water molar fractions. The study also includes an extension of the thermoacoustic model for characteristics LIGS signals, built in order to extract the relative concentration of water vapour from the ratio of second (thermal) to first (electrostrictive) peak magnitudes. Experiments are conducted in non-sooting flames, leveraging a high-pressure optical chamber (HPOC) with pressures up to 3 bar. The study evaluates mixtures of methane and hydrogen (100%, 70%, and 40% CH(_{4})) and identifies key relationships between LIGS signal characteristics, frequency distributions, and combustion dynamics. Results show excellent agreement between measured temperatures and adiabatic flame temperatures, alongside measurements of water vapour molar fractions. The spatial temperature and water vapour maps are related to the complex mixing and recirculation patterns associated with the flame’s shear and recirculation zones. The results establish LIGS as a robust diagnostic tool for combustion analysis, with potential applications in advancing hydrogen-rich energy systems.

In this work, we explored the impact of indium composition (x) on the structural and optical characteristics of In_xAl_1-xAs layers within the context of quantum cascade laser (QCL) structures grown on InP (100) substrates using the Metal Organic Vapor Phase Epitaxy method. The quality of the In_xAl_1-xAs QCL is notably influenced by the growth with low indium composition, evident in terms of crystallinity, interface sharpness, and optical properties. The properties of the InAsP layer at the InP/In_xAl_1-xAs junction are particularly sensitive to the indium composition. A drop below 0.52 in indium composition leads to a substantial lattice mismatch between the In_xAl_1-xAs layer and the InP substrate, typically exceeding [3 8]%. This mismatch induces defects or traps within the bandgap, significantly impacting carrier localization in this system. Our study demonstrates that cultivating In_xAl_1-xAs with a low indium concentration results in a strained (lattice-mismatched) In_xAl_1-xAs layer. This finding is significant as it can be leveraged to balance strain in high indium content InGaAs layers, particularly in the context of applications involving quantum cascade lasers.

We experimentally demonstrate a continuous-wave (CW) dual-wavelength emission from a single Yb:YAG thin-disk laser (TDL). Using two grating-waveguide structures (GWS) with high diffraction efficiency allowed to tune the separation of the two spectral emission lines. The dual-wavelength output powers exceeded 42 W for wavelength separations ∆λ ranging between 3.8 and 25 nm.

In this study, an analytical methodology based on wave theory is presented in a multilayered SPR fiber optic biosensor which detects cortisol, an important stress biomarker, using a radially polarized Bessel-Gauss (RPBG) beam. The analytical model is first illuminated using a Gaussian (G) beam, and the outcomes are compared with experimental data that has already been published. The findings are correlated favourably with the assessed data presented by Usha et al. Biosens. Bioelectron. 87, 178–186 (2017). Following the confirmation of the suggested theory, the method has been modified to include Gaussian, radially polarized Gaussian (RPG), and RPBG beams as source inputs for the suggested configuration. The design of this idea features a no-core fiber (NCF) integrated between two higher-order mode fibers. The efficacy of the RPBG beam within this waveguide structure is validated using eigenmode expansion (EME) analysis in mode solutions software (Lumerical’s Inc.), ensuring the accurate evaluation of light propagation. Initial investigations with a Gaussian beam demonstrated a sensitivity of 182.8 nm/ng/mL, 4945.23 nm/RIU, and 16,059.4 dB/RIU, which is 2.2 times superior to the conventional Gaussian beam-based sensors. Next, employing an RPG beam, these values increased to 202.7 nm/ng/mL, 8844.31 nm/RIU, and 76,683.33 dB/RIU, respectively. A further extension, incorporating an RPBG beam, improves the sensitivities with 241.85 nm/ng/mL, 16,515.12 nm/RIU, and 195,951 dB/RIU, with an enhanced resolution of 5.1 × 10−⁸, surpassing the Gaussian-based sensor by a factor of 7.36. This implementation of an RPBG beam significantly boosts the sensitivity in fiber optic cortisol biomarker detection. Here, the limit of detection (LOD) is 0.001 ng/mL, and significant spectral shifts are observed when the cortisol biomarker concentration ranges from 0 to 2.5 ng/mL. Thus, the early identification of psychological stress through optical measurement may be facilitated by the attainment of improved sensitivity and resolution at lower concentrations. This sensor enables non-invasive cortisol detection through saliva analysis, offering a practical and scalable biosensing platform with high sensitivity for biomedical diagnostics and occupational health monitoring.

Methods of Laguerre–Gaussian (LG) modes formation are now the content of a significant number of publications on lasers of various types. Axicons with an obtuse apex (170–178(^{circ })) in combination with spherical lenses have been traditionally used in pumping channels of solid-state lasers to produce annular pump beams for LG modes selection. Switching of modes was carried out usually by moving the lenses or some other elements of the laser. We show that acute-apex axicons in a liquid (which do not work in air because of the total internal reflection inside) can be used also for LG modes selection and allow temperature switching of modes. A cuvette with 78(^{circ }) apex axicon immersed in a liquid mixture was installed in the pumping channel of a pulsed Rh6G dye laser ((lambda _text {las} approx ) 580 nm, (lambda _text {pump}) = 532 nm). Temperature tuning of LG(_{0,l}) petal modes with indices up to l = 21 was demonstrated. Switching to the neighboring mode required changing the temperature of the cuvette with the axicon by (approx ) 1.2(^{circ }hbox {C}) with no shift of any laser elements. The obtained results expand the range of axicons that can be used in laser pumping channels and provide a practically convenient method of LG modes selection in a laser.