Mosleywinters1624

Here, some statistical behavior as well as repeating patterns are investigated at the same effect. Also thermal effects as laser diode self-heating are discussed and have been measured over six orders of magnitude in time.The notion of synthetic dimensions has expanded the realm of topological physics to four dimensional (4D) space lately. In this work, non-Hermiticity is used as a synthetic parameter in PT-symmetric photonic crystals to study the topological physics in 4D non-Hermitian synthetic parameter space. We realize a 3D exceptional hypersurface (EHS) in such 4D parameter space, and the degeneracy points emerge due to the symmetry of synthetic parameters. We further demonstrate the existence of exceptional degenerate points (EDPs) on the EHS that originates from the chirality of exceptional points (EPs), and the exceptional surface near EDPs behaves like a Dirac cone. We further show that a very narrow reflection plateau can be found near these EDPs, and their sensitivity towards the PT-symmetry breaking environmental perturbation can make these degeneracy points useful in optical sensing and many other nonlinear and quantum optical applications.Toroidal, spherocylindrical, ellipsoidal, and combined surfaces were used to correct astigmatism in aspheric spectacle lenses, and the differences among the proposed techniques were compared. Four astigmatic spectacle lenses were designed with the same optical parameters. A freeform measuring machine was used to evaluate posterior surfaces of aspheric spectacle lenses, and spherical and cylindrical power maps were generated and compared. The measured data were analyzed via commercial software. The toroidal lens helped to extend the clear vision range around the lens, and the ellipsoidal and spherocylindrical surfaces resulted in a more accurate centering of the lens around the optical axis of the eye, avoided astigmatism, and provided better visual perception.We report a diamond Raman ring cavity laser resonantly pumped by a tunable Tisapphire continuous wave laser. We characterize the laser operation generating first Stokes output and, for the first time, generate second Stokes lasing at a maximum output power of 364 mW with 33.4% slope efficiency at 1101.3 nm. Single longitudinal mode operation is achieved for all first Stokes output powers, but only for lower output powers for second Stokes operation. We discuss possible reasons preventing single longitudinal mode operation.The performance of regenerative amplifiers at high repetition rates is often limited by the occurrence of bifurcations induced by a destabilization of the pulse-to-pulse dynamics. While bifurcations can be suppressed by increasing the seed energy using dedicated pre-amplifiers, the availability of adjustable filters and control electronics in modern pulse amplifiers allows to exploit feedback strategies to cope with these instabilities. In this paper, we present a theoretical and experimental analysis of active feedback methods to stabilize otherwise unstable operational regimes of regenerative amplifiers. To this end, the dynamics of regenerative amplifiers are investigated starting from a general space-dependent description to obtain a generalization of existing models from the literature. Suitable feedback strategies are then developed utilizing measurements of the output pulse energies or the transmitted pump light, respectively. The effectiveness of the proposed approach is highlighted by experimental results for a YbCaF2-based regenerative amplifier.Plasmonic nanoparticles with a dielectric-metal core-shell morphology exhibit hybridized modes where the surface plasmon polaritons at the outer and inner surfaces of the shell couple. We demonstrate that suitably tailoring the interference of such hybrid surface plasmon polariton modes leads to composite subwavelength nanospheres with negative asymmetry parameters and strong scattering in the optical frequency range. As a result, for a low density collection of scatterers an anomalous regime occurs, where the extinction mean free path is longer than the transport mean free path. Explicit results for silver-coated nanospheres are presented.A collection of cold rubidium atoms in three-level configuration trapped in one dimensional (1D) optical lattice is revisited. The trapped atoms are considered in the Gaussian density distribution and study the realization of P T-, non-P T- and P T anti-symmetry in optical susceptibility in 1D atomic lattices in a periodic structure. Such a fascinating modulation is achieved by spatially modulating the intensity of the driving field. Interestingly, a nonreciprocal optical propagation phenomenon is investigated. In this system, we have introduced a microwave that couples to the two ground states, spatial modulation of the coupling field, and the atomic density with Gaussian distribution in practice. With a proper detuning and coupling field Rabi frequencies, we can find the condition of P T-symmetry along with field propagation direction, and the novel properties of transmission and reflections have been discussed. The large difference of field reflections from the two ends of the atomic lattice medium shows strong evidence that the nonreciprocal behavior can be greatly enhanced by increasing the spatial modulation amplitude.Three-dimensional chirped Airy Complex-variable-function Gaussian vortex (CACGV) wave packets in a strongly nonlocal nonlinear medium (SNNM) are studied. By varying the distribution parameter, CACGV wave packets can rotate stably in a SNNM in different forms, including dipoles, elliptic vortices, and doughnuts. Numerical simulation results for the CACGV wave packets agree well with theoretical analysis results under zero perturbation. Selleck 4-MU The Poynting vector related to the physics of the rotation phenomenon and the angular momentum as a torque corresponding to the force are also presented. Finally, the radiation forces of CACGV wave packets acting on a nanoparticle in a SNNM are discussed.The deep learning-based decoder of polar codes is investigated over free space optical (FSO) turbulence channel for the first time. The feedforward neural networks (NN) are adopted to establish the decoder and some custom layers are designed to train the NN decoder over the turbulence channel. The tanh-based modified log-likelihood ratio (LLR) is proposed as the input of NN decoder, which has faster convergence and better bit error rate (BER) performance compared with the standard LLR input. The simulation results show that the BER performance of NN decoder with tanh-based modified LLR is close to the conventional successive cancellation list (SCL) decoder over the turbulence channel, which verifies that the NN decoder with tanh-based modified LLR can learn the encoding rule of polar codes and the characteristics of turbulence channel. Furthermore, the turbulence-stability is investigated and the trained NN decoder in a fixed turbulence condition also has stable performance in other turbulence conditions.We propose and experimentally demonstrate the generation of dual-channels chaos with time delay signature (TDS) concealment by introducing a phase-modulated Sagnac loop in mutually coupled semiconductor lasers (MCSL). Furthermore, we demonstrate the utilization of the dual-channels chaos to solve multi-armed bandit (MAB) problem in reinforcement learning. The experimental results agree well with the numerical simulations. For the purpose of comparison, the MCSL with a conventional Sagnac loop is also considered. It is found that the TDS of dual-channels chaotic signals can be better concealed in our proposed system. Besides, the proposed system allows for a better decision making performance in MAB problem. Moreover, compared with the one-channel chaotic system, the proposed dual-channels chaotic system achieves ultrafast decision making in parallel, and thus, is highly valuable for further improving the security of communication systems and the performance of photonic intelligence.This paper presents a theory of size quantization and intersubband optical transitions in bilayer semiconductor quantum wells with asymmetric profile. We show that, in contrast to single-layer quantum wells, the size-quantized subbands of bilayer quantum wells are nonparabolic and characterized by effective masses that depend on the electron wave number and the subband number. It is found that the effective masses are related to the localization of the electron wave function in the layers of the quantum well and can be controlled by varying the chemical composition or geometric parameters of the structure. We also derive an analytical expression for the probability of optical transitions between the subbands of the bilayer quantum well. Our results are useful for the development of laser systems and photodetectors based on colloidal nanoplates and epitaxial layers of semiconductor materials with heterojunctions.A hybrid grating-based Fabry-Perot structure is proposed to investigate light manipulation in the near-infrared wavelength region. It is found that the electromagnetic energy can be easily trapped in different parts of the system at different polarization states. For TM polarization, numerical results show that two remarkable narrowband absorptance peaks appear owing to the excitation of critical coupling with guided mode resonance and Fabry-Perot resonance. link2 While for TE polarization, only one narrowband absorptance peak is generated because only Fabry-Perot resonance is excited. The near-infrared spectral selectivity of the system can be tuned by changing the geometrical parameters. In addition, the spectral absorptance of the system can be optimized by applying gate voltage on graphene sheet to change graphene chemical potential. This valuable dual-band tunable narrowband absorber is a potential application for high-performance optoelectronic devices.We combine erbium-doped fiber amplifier (EDFA) and backward distributed Raman amplifier (DRA) to achieve the real-time wavelength division multiplexing (WDM) transmission of 400 Gbps/carrier polarization division multiplexing (PDM) 16 quadrature amplitude modulation (QAM) signals over 2,000 km of terrestrial field-deployed cut-off shifted fiber (CSF) compliant with ITU-T G.654.E. This paper compares the transmission performance of 400 Gbps/carrier signals achieved in CSF and standard single-mode fiber (SMF). This transmission distance, 2,019 km, is, to the best of our knowledge, the longest in 400 Gbps/carrier WDM transmission field experiments using digital signal processing (DSP) application specific integrated circuit (ASIC) integrated real-time optical transponders with the technologies to compensate device imperfections; the backward DRA used is fully compliant with laser power safety requirements.We investigate the existence and stability of in-phase three-pole and four-pole gap solitons in the fractional Schrödinger equation supported by one-dimensional parity-time-symmetric periodic potentials (optical lattices) with defocusing Kerr nonlinearity. These solitons exist in the first finite gap and are stable in the moderate power region. When the Lévy index decreases, the stable regions of these in-phase multipole gap solitons shrink. Below a Lévy index threshold, the effective multipole soliton widths decrease as the Lévy index increases. link3 Above the threshold, these solitons become less localized as the Lévy index increases. The Lévy index cannot change the phase transition point of the PT-symmetric optical lattices. We also study transverse power flow in these multipole gap solitons.