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These results could be helpful for the understanding of the surface enhanced spectral properties of molecular systems at sub-nanometer nanocavities.In this paper, an analytical approach for the super-modes in the tightly bounded multicore fibers is proposed. The method considers deterministic and random inter-core coupling, and the analytical analysis is based on the ordinary differential equations (ODEs), which are derived from the stochastic differential equations (SDEs). It is theoretically found that the crosstalk level is directly proportional to the square of the ratio for the random inter-core coupling strength over the deterministic coupling strength, and is inversely proportional to the random coupling correlation length. The ODEs for the variance and the super-mode power correlations are also provided to further facilitate the analysis for the tightly bounded multicore fibers. Simple and explicit formulas for the super-mode crosstalk power and power covariance evaluation are provided in the weak super-mode crosstalk scenario.Conventional diffractive and dispersive devices introduce angular dispersion (AD) into pulsed optical fields, thus producing so-called 'tilted pulse fronts'. Naturally, it is always assumed that the functional form of the wavelength-dependent propagation angle[s] associated with AD is differentiable with respect to wavelength. Recent developments in the study of space-time wave packets - pulsed beams in which the spatial and temporal degrees of freedom are inextricably intertwined - have pointed to the existence of non-differentiable AD field configurations in which the propagation angle does not possess a derivative at some wavelength. Here we investigate the consequences of introducing non-differentiable AD into a pulsed field and show that it is the crucial ingredient required to realize group velocities that deviate from c (the speed of light in vacuum) along the propagation axis in free space. In contrast, the on-axis group velocity for conventional pulsed fields in free space is always equal to c. Furthermore, we show that non-differentiable AD is needed for realizing anomalous or normal group-velocity dispersion along the propagation axis, while simultaneously suppressing all higher-order dispersion terms. We experimentally verify these and several other consequences of non-differentiable AD using a pulsed-beam shaper capable of introducing AD with arbitrary spectral profile. Non-differentiable AD is not an exotic phenomenon, but is rather an accessible, robust, and versatile resource for sculpting pulsed optical fields.Due to the topological charge-independent doughnut spatial structure as well as the association of orbital angular momentums, perfect vortex beams promise significant advances in fiber communication, optical manipulation and quantum optics. Inspired by the development of planar photonics, several plasmonic and dielectric metasurfaces have been constructed to generate perfect vortex beams, instead of conventional bulky configuration. However, owing to the intrinsic Ohmic losses and interband electron transitions in materials, these metasurface-based vortex beam generators only work at optical frequencies up to the visible range. Herein, using silicon nitride nanopillars as high-efficiency half-wave plates, broadband and high-performance metasurfaces are designed and demonstrated numerically to directly produce perfect vortex beams in the ultraviolet region, by combining the phase profiles of spiral phase plate, axicon and Fourier transformation lens based on geometric phase. The conversion efficiency of the metasurface is up to 86.6% at the design wavelength. Moreover, the influence of several control parameters on perfect vortex beam structures is discussed. We believe that this ultraviolet dielectric generator of perfect vortex beams will find many significant applications, such as high-resolution spectroscopy, optical tweezer and on-chip communication.Lead iodide (PbI2) is a van der Waals layered semiconductor with a direct bandgap in its bulk form and a hexagonal layered crystalline structure. The recently developed PbI2 nanosheets have shown great promise for high-performance optoelectronic devices, including nanolasers and photodetectors. However, despite being widely used as a precursor for perovskite materials, the optical properties of PbI2 nanomaterials remain largely unexplored. Here, we determine the nonlinear optical properties of PbI2 nanosheets by utilising nonlinear microscopy as a non-invasive optical technique. We demonstrate the nonlinearity enhancement dependent on excitonic resonances, crystalline orientation, thickness, and influence of the substrate. Our results allow for estimating the second- and third-order nonlinear susceptibilities of the nanosheets, opening new opportunities for the use of PbI2 nanosheets as nonlinear and quantum light sources.We propose and demonstrate a pulsed-chaos multiple-input-multiple-output (MIMO) radar system in this paper. In the proposed MIMO radar system, multi-channel pulsed chaotic signals are extracted from an optical seed chaos source with Delta-like autocorrelation and flat spectrum. The seed chaos source is generated by passing the chaotic output of an external-cavity semiconductor laser through a dispersive self-feedback phase-modulation loop and used for MIMO radar signal generation. The cross-correlation characteristics of MIMO radar signals, the maximum channel number of separable mixed echoes, as well as the performances of multi-target ranging and anti-interference in the proposed pulsed-chaos MIMO radar system are systematically investigated. The results indicate that multi-channel pulsed-chaos signals with Delta-like autocorrelation can be simultaneously generated from the seed chaos source, and excellent quasi-orthogonality of transmission radar signals can be guaranteed. Moreover, it is demonstrated that the proposed pulsed-chaos MIMO radar supports multi-target ranging with a centimeter-level resolution and can maintain satisfactory performance under low SNR scenarios with various interferences.A switchable, widely wavelength-tunable noise-like pulse (NLP) and Q-switched Er-doped fiber (EDF) laser with a linear cavity structure is proposed and experimentally demonstrated in this work. The net-normal-dispersion mode-locked NLP operation based on a semiconductor saturable mirror (SESAM) is realized in a 57 nm continuous tuning range from 1528 to 1585 nm by using a tunable filter (TF). When the pump power is 500 mW, the NLPs produce a maximum average output power of about 16 mW with a 3-dB spectral bandwidth of about 17 nm at the central wavelength of 1555 nm, while the average peak power is about 58.8 W. The measured characteristics of the output NLPs at 1555 nm are consistent with the numerical results under the condition of Δβ2, net = 0.095 ps2, and Esat = 0.77 nJ. In addition, stable Q-switched pulses with a 67 nm wavelength tuning range from 1518 to 1585 nm are obtained by adjusting the central wavelength of the filter. The maximum pulse energy reaches 231.4 nJ at the center wavelength of 1555 nm, corresponding to a peak power of about 278.8 mW. MM3122 cell line The proposed wavelength-tunable fiber laser is simple and versatile, demonstrating significant potential for numerous practical applications.A signal picked-up technique to improve the demodulation stability and accuracy of sapphire fiber external Fabry-Perot interferometer is proposed and demonstrated. Through fusion splicing four pieces of multimode fiber in sequence with different core diameters, the in-step change of the core diameter is found to introduce a sufficient fliting effect on the transmitted higher-order guided modes in the sapphire fiber and further reduce their influence on the fundamental mode interference demodulation. Experimental results show that the proposed multi-stage coupling technique can suppress by five-fold the additional phase imposed on the fundamental mode demodulation when compared with the conventional single-stage coupling approach in which single-mode fiber is spliced with only one piece of multimode fiber. The standard deviation of the demodulated optical phase and cavity length can also be reduced by more than two times. The proposed technique provides a simple yet sufficient solution for the long-standing difficulty of multimode sapphire fiber Fabry-Perot interferometer demodulation.The impulsive stimulated Brillouin microscopy promises fast, non-contact measurements of the elastic properties of biological samples. The used pump-probe approach employs an ultra-short pulse laser and a cw laser to generate Brillouin signals. Modeling of the microscopy technique has already been carried out partially, but not for biomedical applications. The nonlinear relationship between pulse energy and Brillouin signal amplitude is proven with both simulations and experiments. Tayloring of the excitation parameters on the biologically relevant polyacrylamide hydrogels outline sub-ms temporal resolutions at a relative precision of less then 1%. Brillouin microscopy using the impulsive stimulated scattering therefore exhibits high potential for the measurements of viscoelastic properties of cells and tissues.A photonic approach to generate a linearly chirped microwave waveform (LCMW) with an ultra-long temporal duration is proposed and experimentally demonstrated. The microwave waveform generation is achieved based on spectral-shaping and wavelength-to-time (SS-WTT) mapping by using a Mach-Zehnder interferometer (MZI) and a frequency-shifting dispersive loop (FSDL), respectively. To make the generated microwave waveform have an ultra-long temporal duration, the FSDL is operating to allow a spectrally shaped optical pulse to recirculate in a dispersive loop multiple times with a low propagating loss, to generate a microwave waveform with a temporal duration that is more than one order of magnitude longer than that of a microwave waveform generated using a dispersive element without recirculation. To generate a LCMW, the spectral shaper is configured to have a free spectral range (FSR) that is linearly increasing or decreasing with optical wavelength. The proposed approach is experimentally demonstrated. Two LCMWs, by allowing an optical pulse recirculating in the FSDL for three and seven round trips, tripled and septupled temporal durations of 64 and 182 ns are generated. The generation of two LCMWs with ultra-long temporal durations of 370 ns and 450 ns are also demonstrated.Determination of macroscale detonation parameters of energetic materials (EMs) in a safe and rapid way is highly desirable. However, traditional experimental methods suffer from tedious operation, safety hazards and high cost. Herein, we present a micro-scale approach for high-precision diagnosis of explosion parameters based on radiation spectra and dynamic analysis during the interaction between laser and EMs. The intrinsic natures of micro-explosion dynamics covering nanosecond to millisecond and chemical reactions in laser-induced plasma are revealed, which reveal a tight correlation between micro-detonation and macroscopic detonation based on laser-induced plasma spectra and dynamics combined with statistic ways. As hundreds to thousands of laser pulses ablate on seven typical tetrazole-based high-nitrogen compounds and ten single-compound explosives, macroscale detonation performance can be well estimated with a high-speed and high-accuracy way. Thereby, the detonation pressure and enthalpies of formation can be quantitatively determined by the laser ablation processes for the first time to our knowledge.