Modelling and characterisation of the noise characteristics of the vertical cavity surface-emitting lasers subject to slow light feedback Abstract This paper introduces the modelling and characterisation of the noise properties of the vertical cavity surface-emitting laser (VCSEL) coupled in lateral direction with a passive cavity. This design of VCSEL with this transverse coupled cavity (TCC) is proposed for high-speed photonics. We introduce comprehensive simulations on the influence of the induced lateral slow light feedback on the relative intensity noise (RIN) and carrier-to-noise ratio (CNR). The proposed model incorporates multiple round trips of slow light in the TCC as time delay light in the rate equations of the VCSEL. The obtained results are compared with those of the conventional VCSEL. We show that the noise performance of the TCC-VCSEL is optimised when the VCSEL exhibits stable continuous wave (CW) operation under strong slow light feedback and the TCC length is smaller than 8 \(\mu \) m and between 11 and 13 \(\mu \) m. When strong slow light induces unstable regular and / or irregular oscillations, RIN is enhanced and CNR is lowered.

Successive linearisation approach to analyse thermally radiative stagnation point micropolar nanofluid flow with regression model Abstract The present paper is devoted to the investigation of magnetohydrodynamics (MHD) mixed convection stagnation point flow of a micropolar nanofluid with thermal radiation, microrotation, viscous and Joule dissipations, Brownian and thermophoretic diffusions, etc. The present analysis is done because it contains large potential to deal with many industrial processes such as electrical power generation, nuclear energy plant, melt spinning technique for cooling liquids, astrophysical flows, space vehicles, geothermal extractions, solar system, etc. The numerical solutions of the governing equations are obtained by successive linearisation method (SLM). The influence of various developing parameters, such as thermal radiation parameter, mixed convection parameter, thermophoretic parameter, etc., on the flow field is examined through graphs by accumulating sufficient data using SLM. A comparative study is performed between our results and previously obtained results in the limiting sense. Apart from this, the quadratic multiple regression analysis is performed for skin friction coefficient. It indicates that when the free stream is moving with less velocity than stretching velocity then a small variation in microrotation leads to large perturbation in skin friction in comparison to mixed convection parameter but in the opposite case, the buoyancy force becomes more dominant.

Analysis with relativistic mean-field density distribution of elastic scattering cross-sections of carbon isotopes ( 10–14,16 C) by various target nuclei Abstract A microscopic study of elastic scattering of carbon isotopes from different target nuclei at various incident energies is presented by using density distributions derived for 10–14,16C nuclei using relativistic mean field (RMF) theory. To obtain the real part of the optical potential, the double folding model is used. Woods–Saxon potential is used for the imaginary part. The theoretical results are discussed and compared with each other as well as with the experimental data. It is seen that the agreement between theoretical results and experimental data is very good. Also, new global equations for the imaginary potentials of the 10–14,16C nuclei are derived from the results of the theoretical analysis.

Solitary waves in strongly non-local media with a harmonic potential Abstract An exact analytical solution in strongly non-local media with a harmonic potential has been studied. Two-dimensional Bessel solitary wave clusters have been obtained by a self-similar method. The intensity distributions of optical beam with different parameters have been discussed in detail. It is found that the solitary waves have a symmetric necklace distribution and the number of facular points is double the value of the quantum number m. The modulation of the external potential field to the width of light beam is also discussed.

Brief report Robustness of coherence for multipartite quantum states Abstract In this brief report, we prove that the robustness of coherence (ROC), in contrast with many popular quantitative measures of quantum coherence derived from the resource-theoretic framework of coherence, may be a subadditive for a specific class of multipartite quantum states. We investigate how the subadditivity is affected by admixture with other classes of states for which ROC is superadditive. We show that pairs of quantum states may have different orderings with respect to relative entropy of coherence, \(l_{1}\) -norm of coherence and ROC and numerically study the difference in ordering for the chosen pairwise coherence measures.

q -Deformed oscillator algebra in fermionic and bosonic limits Abstract In this paper, the structure function corresponding to the q-deformed harmonic oscillator algebra is considered, where we construct the Hamiltonian by using creation and annihilation operators. Finally, the problem is investigated by evaluating the partition function of the system in finite- and infinite-dimensional Fock space for both fermionic and bosonic limits. Other thermodynamic properties such as the internal energy and the specific heat of the system are also calculated.

A chaotic study on Heisenberg ferromagnetic spin chain using Dzyaloshinski–Moriya interactions Abstract The chaotic dynamics of a one-dimensional Heisenberg ferromagnetic spin chain incorporating Dzyaloshinski–Moriya (D–M) interaction, dipole–dipole and quadrupole–quadrupole interactions has been investigated. The studies are carried out by plotting phase diagrams and chaotic trajectories. We then analyse the stability of the system using the Lyapunov stability analysis.

Violation of space–time Bell-CHSH inequality beyond the Tsirelson bound and quantum cryptography Abstract Here we show that if we insert context-dependent local unitary evolutions into the spatial (i.e. normal) Bell–Clauser–Horne–Shimony–Holt (Bell-CHSH) test, then it is possible to violate the space–time Bell-CHSH inequality maximally (i.e. up to 4). The correct context dependency can be achieved via post-selection. However, this does not contradict the Tsirelson quantum bound ( \(2\sqrt{2}\) ), because the latter has been derived without taking into consideration the context-dependent unitary evolutions and / or post-selection. As an important application, this leads to a more efficient (in terms of resource (singlets) and classical communication) and more sensitive (to eavesdropping) quantum key distribution (QKD) protocol, compared to Ekert’s and Wigner’s QKD protocols.

Numerical solution of nonlinear fractional Zakharov–Kuznetsov equation arising in ion-acoustic waves Abstract The main purpose of this work is to suggest an efficient hybrid computational technique, namely the q-homotopy analysis transform method (q-HATM) to find the solution of the nonlinear time-fractional Zakharov–Kuznetsov (FZK) equation in two dimensions. The uniqueness and convergence analysis of the nonlinear time-FZK equation is presented. The Laplace decomposition method (LDM) is also employed to get the approximate solution of the nonlinear FZK equation. We implemented these techniques on two numerical examples, plotted the solution and compared the absolute error with the variational iteration technique and homotopy perturbation transform technique to show the efficiency of these techniques.

Structural, elastic and dynamical properties of $$\hbox { YP}_{1-x}\hbox {As}_{x}$$YP1-xAsx alloys from first principles calculations Abstract The structural, elastic and lattice vibration properties of the ternary alloys \({\mathrm{YP}}_{1-x}{\mathrm{As}}_{x}\) at various As concentrations (x) from 0 to 1, \(x=0\), 0.25, 0.5, 0.75 and 1, are presented. The calculations were performed using the density functional perturbation theory (DFPT) within the generalised gradient approximation (GGA) and employing virtual crystal approximation (VCA). We studied the effect of arsenic (As) composition on structural parameters, the phase transition pressure, the elastic constants, the optical and acoustic phonon frequencies at high symmetry points \(\Gamma \), X and L, the static and electronic dielectric constants, and the Born effective charge. It is established that all these properties follow a quadratic law in the concentration (x). There is a good agreement between our results and the available data for binary compounds YP and YAs. Our results are for \({\mathrm{YP}}_{1-x}{\mathrm{As}}_{x}\) predictions.