Applied Physics B最新文献

Tracer based planar laser-induced fluorescence (PLIF) has emerged as a powerful in-situ measurement technique with a considerable spatial and temporal resolution for Internal combustion (IC) engines. In PLIF, the emitted fluorescence signals from a tracer molecule are processed to determine distribution of temperature, fuel, residual gases etc. However, it is imperative to have a thorough understanding of the tracer physical properties and its fluorescence intensity dependencies on excitation wavelength, pressure, temperature, and bath gas composition existing inside the combustor for accurate quantitative interpretation. This work consists of a series of two articles providing a detailed review of the existing literature of fluorescence characteristics of various molecules used as tracers in IC engine applications. Due to the overwhelming usage of organic compounds in IC engine environment, the work is restricted to them. Part A of this work is focussed on non-aromatic compounds (acetone, 3-pentanone and biacetyl) whereas part B will focus on aromatics. Due to a small energy gap between the excited singlet and triplet states of ketones, they experience rapid inter-system crossing making them far less sensitive to oxygen quenching effects than aromatic molecules. Addition of tracers to surrogate fuel can lead to difficulties related to co-evaporation, azeotrope formation and stability of tracer molecules in terms of photolysis and pyrolysis effects when subjected to intense laser irradiation and harsh engine environment. In this work, fluorescence signal variation of tracer molecules is divided into variations in absorption cross-section and fluorescence quantum yield (FQY). Absorption cross-section normally increases with temperature but is insensitive to pressure changes. FQY reduces with increase in temperature but increases with pressure for ketones for non-oxygen containing bath gases. The pressure sensitivity increases with the number of atoms in a collider molecule. FQY values decrease with decreasing laser excitation wavelength whereas the temperature and pressure sensitivity of FQY reduce with increasing wavelengths. For simultaneous high pressure and temperature conditions, the pressure sensitivity of FQY is found to reduce due to a reduction in the effective number of collisions with bath gas molecules. Among the three tracers, acetone has been widely used for marking gaseous fuels and 3-pentanone and biacetyl for liquid fuels like iso-octane. Acetone and 3-pentanone have received significant attention for fluorescence studies due to their widespread usage in IC engine applications. Biacetyl on the other hand has recently started to receive attention due to its application in high repetition rates PLIF measurements and requires more fluorescence studies to fully characterise its fluorescence behaviour and construct fluorescence models over the complete pressure and temperature range required in IC engine applications.

In this paper, we demonstrate a tunable mid-infrared (mid-IR) optical parametric oscillator (OPO) using an MgO: PPLN crystal with a polarization period of 29.8 μm, which was end-pumped by a 1064 nm electro-optic cavity-dumped all-solid-state laser (1064 nm EOCD-laser) with a pulse repetition frequency range of 100 Hz to 1 kHz. Thanks to the use of 808 nm pulsed laser diode (LD) side-pumping Nd: YAG crystal, transverse electro-optic modulating (TEOM) MgO: LN crystal, and birefringent crystal (BC) filtering in the 1064 nm cavity-dumped cavity, both the 1064 nm EOCD-laser and the idler light output by the OPO exhibited high peak power and low peak-to-peak instability in both pulse width and single pulse energy. By combining temperature tuning of the MgO: PPLN crystal from 30 °C to 200 °C, wavelength tuning of the idler light from 3705.2 to 3424.3 nm was achieved. For the first time, a pulsed idler light at 3705.2 nm with a high peak power of 1.224 MW, a narrow pulse width of 4.97 ns, and an optical-to-optical (1064 nm to 3705.2 nm) conversion efficiency of 38.1% was obtained, corresponding to a tuning temperature of 30 °C and a pulse repetition frequency of 100 Hz. The peak-to-peak instability for both pulse width and single pulse energy was only ± 1.04% and ± 1.41%, respectively.

In this work, the external magnetic field is employed as a “knob” to transfer the light energy from the zero-order diffraction to the high-order diffractions of electromagnetically induced grating in a degenerate two-level atomic medium. Under a standing-wave coupling field, the diffraction of the probe beam is created with the diffraction pattern including zero-, first- and second-order diffractions. When the magnetic field is not applied, the absorption grating is formed based on amplitude modulation of the transmission function; most of the probe light energy is focused on the zero-order diffraction (about 70%) and only about 6% of the first-order diffraction. However, when the external magnetic field is applied, the phase grating is formed based on the phase modulation of transmission function; the probe light energy is transferred from zero-order diffraction to first- and second-order diffractions, in which the first-order diffraction efficiency can be obtained about 32% with proper magnetic field strength. Moreover, the probe light energy can also be transferred from zero-order diffraction to first- and second-order diffractions by adjusting the frequency and/or the intensity of the coupling and probe fields in the presence of external magnetic field.

In this paper, we investigate the dynamics of quantum correlation using a Heisenberg spin system in the presence of the Dzyaloshinskii–Moriya interaction (DM) and an external magnetic field. Indeed, quantum discord and its geometrical aspects, namely the trace and Hellinger distances, have been exploited in order to study quantum correlation evolution using the Lindblad master equation. A substantial enhancement in geometric quantum discord (GQD) is observed when the values of DM increase. Moreover, our results show that the geometric quantum discord undergoes a decrease in function of the external magnetic field; except for the small values, its maximum is reached. However, we find that strong values of the temperature have a destructive effect on the behavior of GQD.

This research investigates the interplay between coherence and skew information correlations in the Ising-({textbf {XYZ}}) diamond chain, which includes both Ising and Heisenberg spin particles in the presence of an external magnetic field. The initial step involves determining the reduced density matrix using the transfer matrix approach (TMA). Following this, quantum correlations and coherence in the Ising-({textbf {XYZ}}) diamond chain are quantified using uncertainty-induced nonlocality (UIN), local quantum uncertainty (LQU), and the (ell _1) norm of coherence ((C_{ell _1})). The study examines the impact of thermal noise and various system parameters, such as the xy-anisotropy (alpha), Heisenberg interaction (Gamma) among interstitial sites, Ising spin exchange (J_1), and magnetic field strength, on the dynamics of quantum resources within the system. The results indicate that both temperature and magnetic field negatively affect these quantum properties. Conversely, values of the xy-anisotropy parameter enhance quantum correlation and coherence, mitigating the detrimental impact of absolute temperature. This research offers significant insights into the behavior of quantum resources in this specific system.

In the present theoretical analysis, a new scheme of terahertz (THz) generation is proposed by beating of the two dark hollow laser beams (DHLBs) in the magnetized plasma under the influence of a D.C. electric field. The D.C. electric and static magnetic fields are applied mutually perpendicular to each other as well as to the direction of propagation of DHLBs. The nonlinear current density becomes strong due to the coupling between the nonlinear density and D.C. drift velocity of the electrons of magnetized plasma which is further responsible for THz generation. The normalized THz amplitude shows enhancement with the increase of D.C. electric and static magnetic fields. The dark-size parameter and beam order also play a significant role in the enhancement of the THz generation. The present scheme is capable of generating THz radiation at laser intensities ( ,10^{14} ;{text{W}}/{text{cm}}^2), the magnetic field ( 38;{text{kG}}), D.C. electric field (45;{text{kV}}/{text{cm}},) and electron temperature ( ,6;{text{keV}}.) We have also considered the mutual interactions between the DHLBs and emitted THz radiation with magnetized plasma to provide more practical and accurate results. This scheme can be proved to be very effective and helpful in developing a proper tunable THz source for the investigation of histopathological samples, Bessel cell carcinoma tissues, and the treatment of tumors.

Borosilicate glasses were prepared via melt quench technique with different concentration of Nd³⁺ ions. X-ray diffraction (XRD) was performed for the prepared glass to study the amorphous structure. The glass stability was studied by Thermo-gravimetric Analysis (TGA). Spectroscopic analysis of the prepared glasses was done through absorption, excitation, emission and decay measurements. Absorption spectra was used to evaluate the J-O parameters. Radiative parameters are evaluated with the help of application of J-O theory. Emission spectra show three prominent bands in NIR region arising from ⁴F_3/2 → ⁴I_9/2, ⁴I_11/2 and ⁴I_13/2 centered around 910, 1068 and 1339 nm accordingly, with the most intense being the one at 1068 nm. Stimulated emission cross section, branching ratio and quantum efficiency for ⁴F_3/2 → ⁴I_11/2 transition is very high and is suitable for lasing applications. Dipole–dipole interaction is observed among activator ions on the basis of Dexter theory. The optimized Nd³⁺ doped glass (NBS10) possess maximum value for all radiative parameters and hence can be best suited for applications in the area of lasers and fiber amplifiers.

Laguerre-Gaussian beams possess a unique transverse mode structure defined by the orbital (l) and radial (m) mode numbers, offering promising potential for controlling nonlinear optical interactions. This comprehensive study aims to elucidate the crucial influence of this transverse mode structure on the nonlinear absorption processes. We first established a rigorous theoretical framework by deriving analytical expressions describing the behavior of the Open Z-scan normalized optical transmittance for an arbitrary nth-order nonlinear process under the weak nonlinearity approximation, accounting for the transmitted optical intensity, power, and their dependency on the beam’s transverse mode profile. In the numerical simulations, we focused on the specific case of second-order ((n=2)) nonlinear absorption. Subsequently, detailed numerical simulations were employed to systematically analyze the intricate interplay between the (l) and (m) mode indices and their impact on the transmittance characteristics. By precisely varying these indices, we investigated how the observed transmission profiles were affected, revealing distinct behaviors for different Laguerre-Gaussian modes. When only (m) increases, absorption decreases due to the wider transverse energy spread, while varying (l) leads to a non-monotonic trend involving intense lobes. Remarkably, simultaneously increasing both (l) and (m) systematically enhances absorption through constructive interference of the helical and ring-like structures.

This paper provides a detailed analysis of transverse mode degeneracy process of end-pumped Nd:(hbox {YVO}_4) laser. By observing the intersection of the beat frequency signals in the concave-plano cavity, the exact cavity length position of the transverse mode degeneracy can be clearly identified, which is also where transverse-mode locking occurs. Investigating the positions of the degeneracy of 1/3 and 2/7 reveals that transverse-mode locking occurs within the micrometer range. Our results give a simple and intuitive description of frequency degeneracy in a common solid-state laser

Heat engines are considered a valuable resource for the modern society. The development of these systems leads to the production of heat engines with high efficiency despite their small size, called quantum heat engines. Among these, the quantum Otto cycle which is considered a fundamental thermodynamic cycle in classical heat engines, has also found applications in the realm of quantum heat engines. In this paper, we consider three InAs quantum dots as a working substance, which allows the engine to operate at very small scales, in the presence of an electric field, and the Förster mechanism, which describes the transfer of energy between quantum dots and thus affects the engine’s behavior. In this regard, we study the behavior of the work performed by the engine and the entanglement in the system as the Förster parameter is varied. We found a significant link between the engine’s work performance, the system’s entanglement, and the Förster interaction. At a critical Förster interaction value, which depends on the excitons frequencies, we observe a sharp inflection in work output. This transition coincides with the system reaching maximum entanglement after a separable state.