An approach to scrutinize the nanoscale near-field distribution within the extreme interactions of femtosecond laser pulses and nanoparticles is outlined in this research, thereby enabling a study of the complex dynamic behavior within this system.
We investigate, both theoretically and experimentally, the optical trapping of two distinct microparticles using a double-tapered optical fiber probe (DOFP), fabricated via an interfacial etching process. Two SiO2 microspheres of diverse dimensions, or a yeast and a single SiO2 microsphere, are found trapped. Using calculation and measurement techniques, we analyze the trapping forces acting on two microparticles, and subsequently investigate how their geometric size and refractive index influence these trapping forces. A comparison of theoretical calculations and experimental measurements reveals that identical refractive indices in the two particles correlate with a stronger trapping force in the larger particle. In scenarios where the geometrical sizes of the particles are equivalent, the trapping force exhibits a direct relationship with the inverse of the refractive index; a smaller refractive index results in a greater trapping force. The application of optical tweezers, particularly in biomedical engineering and materials science, is significantly enhanced by a DOFP's ability to trap and manipulate various microparticles.
Tunable Fabry-Perot (F-P) filters, frequently employed as demodulators for fiber Bragg grating (FBG), show drift errors when confronted with ambient temperature fluctuations and piezo-electrical transducer (PZT) hysteresis. Research on drift mitigation, as represented in the majority of existing literature, commonly employs auxiliary devices such as F-P etalons and gas chambers. This paper details a new drift calibration method, constructed through a two-stage decomposition and hybrid modeling technique. Employing variational mode decomposition (VMD), the initial drift error sequences are divided into three frequency bands. A secondary VMD procedure is then applied to further break down the medium-frequency components. The initial drift error sequences' complexity is substantially lowered by the two-stage VMD process. To predict low-frequency drift errors and high-frequency drift errors, respectively, the long short-term memory (LSTM) network and polynomial fitting (PF) are utilized, building upon this foundation. The LSTM model's strength lies in predicting intricate, non-linear localized behaviors, whilst the PF method forecasts the general trend. This method effectively harnesses the potential of LSTM and PF. Compared to the simple single-stage process, the more complex two-stage decomposition procedure produces far better results. This suggested method presents an alternative to the current drift calibration techniques, proving both economical and effective in its approach.
The transformation of LP11 modes into vortex modes in gradually twisted, highly birefringent PANDA fibers is investigated under the effects of core ellipticity and core-induced thermal stress, leveraging an improved perturbation-based modeling technique. Our findings reveal a significant impact of these two technologically inescapable factors on the conversion process, characterized by a contraction of the conversion timeline, a change in the assignment of input LP11 modes to output vortex modes, and a modification of the vortex mode architecture. For certain fiber geometries, we exhibit the generation of output vortex modes that exhibit both parallel and antiparallel spin and orbital angular momenta. The modified method's simulation results display a satisfactory consistency with the recently published experimental data. Additionally, the proposed methodology provides dependable criteria for selecting fiber characteristics, thereby ensuring a brief conversion length and the necessary polarization configuration for the outgoing vortex modes.
Surface wave (SW) amplitude and phase are simultaneously and independently modified, a critical requirement for both photonics and plasmonics. A flexible approach for modulating the complex amplitude of surface waves is detailed, relying on a metasurface coupler. The meta-atoms' complex-amplitude modulation capability, spanning the entire transmitted field, empowers the coupler to convert the incident wave into a driven surface wave (DSW) possessing a customized combination of amplitude and initial phase. A dielectric waveguide that supports guided surface waves, when positioned beneath the coupler, facilitates resonant surface wave coupling, thereby maintaining complex-amplitude modulation in the coupled devices. A practical procedure for manipulating the phase and amplitude profiles of surface wave wavefronts is provided by the proposed plan. In the microwave regime, meta-devices for the generation of normal and deflected SW Airy beams, and SW dual focusing, are created and thoroughly analyzed to confirm their function. Our findings hold the promise of stimulating the design and creation of various state-of-the-art surface optical meta-devices.
A metasurface incorporating arrays of dielectric tetramer elements with broken symmetries is proposed. This structure can produce polarization-selective dual-band toroidal dipole resonances (TDR) with extremely narrow linewidths in the near-infrared region. gnotobiotic mice A consequence of disrupting the C4v symmetry within the tetramer arrays was the formation of two narrow-band TDRs, with linewidths constrained to 15nm. Analyses of the electromagnetic field distribution and the decomposition of scattering power into multiple components reinforce the nature of TDRs. Theoretically, a 100% modulation depth in light absorption, coupled with selective field confinement, has been shown achievable simply by altering the polarization orientation of the incident light. Remarkably, the metasurface exhibits a polarization-angle-dependent TDR absorption response that meticulously follows Malus' law. Beyond this, toroidal resonances with dual bands are suggested for the sensing of birefringence in an anisotropic medium. This structure's dual toroidal dipole resonances, with polarization-tuning capabilities and ultra-narrow bandwidths, could lead to promising applications in optical switching, storage, polarization-detection, and light-emitting devices.
A distributed fiber optic sensing approach, coupled with weakly supervised machine learning, is used to pinpoint manholes. To our knowledge, ambient environmental data is being employed for the first time in underground cable mapping, promising to improve operational effectiveness and reduce fieldwork. Leveraging a selective data sampling scheme and an attention-based deep multiple instance classification model, the weak informativeness of ambient data can be effectively accommodated, requiring only weakly annotated data. Multiple existing fiber networks serve as the backdrop for field data used to validate the proposed approach through a fiber sensing system.
An optical switch, based on the interference of plasmonic modes within whispering gallery mode (WGM) antennas, is presented along with its experimental validation. Even and odd WGM modes, simultaneously excited through slight symmetry disruption via non-normal illumination, toggle the plasmonic near-field between the antenna's opposing sides, contingent on the excitation wavelength within a 60nm span centered around 790nm. Experimental validation of the proposed switching mechanism is achieved by combining photoemission electron microscopy (PEEM) with a femtosecond laser system tunable in the visible and infrared regions.
Novel triangular bright solitons, believed to be solutions of the nonlinear Schrödinger equation with inhomogeneous Kerr-like nonlinearity and external harmonic potential, are demonstrated, offering potential applications in nonlinear optics and Bose-Einstein condensates. The solitons' profiles are not like those of common Gaussian or sech beams; instead, they resemble a triangle at the top and an inverted triangle at the base. In relation to the triangle-up solitons, the self-defocusing nonlinearity plays a crucial role, and conversely, the self-focusing nonlinearity plays a critical role in the emergence of triangle-down solitons. Our current concern is specifically with the lowest-order fundamental triangular solitons. All these solitons are stable, as a consequence of the clear demonstration through linear stability analysis and further confirmation from direct numerical simulations. Along with the preceding observations, the modulated propagation of both categories of triangular solitons, the strength of nonlinearity being the modulating variable, is also shown. Propagation is demonstrably sensitive to the form in which the nonlinearity is modulated. While a gradual shift in the modulated parameter produces stable solitons, sudden changes induce instabilities within the soliton structure. In addition, the parameter's rhythmic variation induces a consistent, periodic oscillation pattern in the solitons. involuntary medication The triangle-up and triangle-down solitons demonstrate a remarkable property of interconversion upon the alteration of the parameter's sign.
Expanding the range of visualizable wavelengths is facilitated by the combined use of imaging and computational processing technologies. Realizing a single system capable of imaging a broad array of wavelengths, spanning the visible and non-visible regions, presents considerable challenges. Femtosecond laser-powered sequential light source arrays are fundamental to the broadband imaging system we propose. selleck products Irradiated pulse energy, in concert with the excitation target, dictates the ultra-broadband illumination light generated by the light source arrays. The demonstration of X-ray and visible imaging, achieved under atmospheric pressure, relied on a water film as the excitation target. Additionally, by leveraging a compressive sensing algorithm, the imaging process was expedited, ensuring the same number of pixels in the reconstructed image.
Thanks to its exceptional wavefront shaping, the metasurface achieves superior performance in applications like printing and holography, representing a pinnacle of current technology. In recent times, a unified metasurface chip has amalgamated these two functions, thereby augmenting capabilities.