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The Goos-Hänchen and Imbert-Fedorov shifts are significant wave phenomena, yet the underlying mechanism governing the spatiotemporal vortex pulses reflected and refracted on graphene remains opaque. In this study, we analytically derive the expressions for the centroid shifts of spatiotemporal vortex pulses by applying the Fresnel-Snell formulas to each plane wave in the incident spatiotemporal vortex pulse spectrum. We demonstrate that the longitudinal shifts are correlated with the angular shifts, and thus, both are subject to resonant enhancement in the vicinity of the Brewster angle. It is possible to tune the resonant enhancement of the shifts by modifying the Fermi energy of graphene. An increase in the vortex topological charge l results in an enhancement of both the angular and longitudinal shifts while the transverse shifts are reduced. The shifts of the intensity distribution, in accordance with the Goos-Hänchen and Imbert-Fedorov shifts, facilitate experimental measurements. The high frequency in the terahertz region will diminish the resonant enhancement of the spatial shifts of the reflected wavepackets. The analysis presented here can be extended with minimal effort to spatiotemporal vortex pulses reflected and refracted on other two-dimensional atomic crystals.

Volterra nonlinear equalizer (VNE) is widely used in intensity modulation and direct detection (IM/DD) systems because it employs multi-order operations to effectively capture the nonlinear characteristics of signals as a generic tool. In the specific directly-modulated laser with direct detection (DML-DD) link, the interaction between the chirp of DML and chromatic dispersion (CD) can be modeled as composite second-order (CSO) distortion. By incorporating the CSO model into the nonlinear equalizer, it is possible to better extract the feature of the end-to-end channel, achieving superior performance with lower complexity. In this work, we propose a computationally efficient physics-informed difference-symmetric nonlinear equalizer (DSNE) based on the analytical formulation of the CSO. Additionally, we provide a thorough comparison of the computational complexity and bit-error-rate (BER) performance of various equalizers. Compared to the conventional VNE, the DSNE provides a 1-dB improvement in receiver sensitivity while reducing computational complexity by 51%. It is shown that the model-assisted DSNE structure enhances the matching to channel nonlinearity by omitting the less cost-effective taps in the conventional VNE and applying difference operations to the symmetric taps. The DSNE incorporates difference-symmetric terms, in contrast to the quadratic nonlinear equalizer (QNE), which uses only diagonal terms. This addition leads to a 56% reduction in BER while incurring only a 12% increase in computational complexity. The proposed DSNE technique demonstrates significant potential for low-cost, high-performance DML-DD optical transmission systems.

A reconfigurable holographic metasurface (HM) with multifunctional modulation of radiation and scattering for conformal applications is designed in this paper. Based on optical holography theory, a holographic conformal modulation mechanism is proposed, and the conformal surface impedance distribution of HM is derived. To illustrate this mechanism, the designed conformal reconfigurable HM is used to demonstrate a series of radiation and scattering modulation functions, with its reconfigurable property enabling dynamic beam control. In radiation mode, beam scanning with wide angle from -50° to 50° is achieved. In scattering mode, specific responses are generated under different incident angles, including beam steering under oblique incidence within ±60°, multi-beam splitting within ±60° under normal incidence, and diffuse reflection. Low radar cross section (RCS) is exhibited over a wide frequency band from 7.2 to 25 GHz. The designed conformal reconfigurable HM shows high adaptability to cylindrical platforms, insensitivity to oblique incidence, and stability in beam deflection angles, which provides an innovative technical approach for information transmission and stealth in conformal devices.

Large energy single-frequency nanosecond (ns) near-infrared light source is an essential device in the field of the remote chemical analysis based on the laser-induced breakdown spectroscopy (LIBS). In this paper, a large energy single-frequency ns 824 nm light source with high repetition rate is presented, which is generated from a seed-injection locked optical parametric oscillator (OPO). By optimizing the spot radius of the pump laser and the mode-matching between the pump laser and signal light, the optical parametric generation (OPG) process is effectively eliminated. On this basis, with the assistance of the seed-injection locking, a single-frequency 4 kHz ns 824 nm light source with an output pulse energy and a spectral width of 3.39 mJ and 32.42 MHz is obtained. For the best of our knowledge, it is the largest energy for the single-frequency ns near-infrared light source with the repetition rate of kHz level.

High-resolution optical diagnostics in the short wavelength infrared (SWIR II) region have gained significant attention in medical research, showing great potential for tissue spectroscopy and visualization due to the region's low water absorption and scattering coefficients. However, high-beam-quality sources covering an entire spectral range are limited. This paper presents the development of a femtosecond Cr²⁺:ZnSe laser with a 2.2 µm center wavelength, a pulse duration of 60 fs, a spectral width of 96.5 nm, and an energy of 4.5 nJ. The resulting source is expected to enable spectroscopy and the optical coherence tomography system for diagnosing collagen-rich tissues.

Mueller matrix polarization measurement technique, as a non-invasive and label-free, provides comprehensive optical information on polarization-related and structural characteristics of the measured target. It has been widely applied in biomedical, agricultural, and industrial fields. However, the traditional time-division modulation Mueller matrix measurement method requires multiple measurements, which suffers from long measurement time and susceptibility to cumulative errors from moving parts. The snapshot spatial modulation method can capture the target's interferograms and the full Mueller matrix element images in a single exposure, but it suffers from lower spatial resolution. To address the strengths and limitations of both temporal and spatial modulation, this paper proposes a tempo-spatially modulated Mueller matrix imaging polarimeter (TSM-MMIP). This approach is based on the Stokes imaging polarimeter with the modified Savart plates as the core device, allowing the acquisition of the 16 Mueller matrix elements of the target with only four measurements. Through computer simulation and experimental platforms, we validate that the structural similarity of Mueller matrix elements between input and output exceeds 0.85, which demonstrates the reliability and feasibility of the proposed method. In addition, we use a bee wing as a target to reveal the potential of this technique to analyze the polarization characteristics of targets by extracting and analyzing key parameters of the Mueller matrix.

We propose and demonstrate an ultra-wide tunable mode-locked all-fiber laser based on nonlinear amplifying loop mirror (NALM) with the output of cylindrical vector beams (CVBs). The tuning range covers from 1029 nm to 1098 nm through the intracavity nonlinear polarization evolution (NPE) filter effect. The switchable CVBs between radially and azimuthally polarized beams with mode purity above 90% are generated by incorporating a broadband few-mode long-period fiber grating (LPFG). It is the first time to realize mode-locked CVBs near 1100 nm and the widest spectral tuning range in all-fiber laser is achieved to our knowledge. The pulsed CVBs at 1098 nm have 3 dB bandwidth of 0.31 nm with a pulse duration of 358ps.The narrow-bandwidth pulse of less than 1 nm is obtained among the whole tuning process which is of high flexibility and high tuning precision by introducing what we believe to be novel tuning mechanisms of NPE into the NALM cavity. The wide-range tunable CVBs all-fiber mode-locked laser has potential applications in high-capacity optical communication, laser imaging, and fiber optic sensing fields.

Optical accordion lattices are routinely used in quantum simulation and quantum computation experiments to tune optical lattice spacings. Here, we present a technique for creating tunable optical lattices using binary-phase transmission gratings. Lattices generated using this technique have high uniformity, contrast, lattice spacing tunability, and power efficiencies. These attributes are crucial for exploring collective quantum phenomena in highly ordered atomic arrays coupled to optical waveguides for quantum networking and quantum simulation. In this paper, we demonstrate adjustable-period lattices that are ideally suited for use with optical nanofibers.

We present a widefield fluorescence microscope that integrates an event-based image sensor (EBIS) with a CMOS image sensor (CIS) for ultra-fast microscopy with spectral distinction capabilities. The EBIS achieves a temporal resolution of ∼10μs (∼ 100,000 frames/s), while the CIS provides diffraction-limited spatial resolution. A diffractive optical element encodes spectral information into a diffractogram, which is recorded by the CIS. The diffractogram is processed using a deep neural network to resolve the fluorescence of two beads, whose emission peaks are separated by only 7 nm and exhibit an 88% spectral overlap. We validate our microscope by imaging the capillary flow of fluorescent beads, demonstrating a significant advancement in ultra-fast spectral microscopy. This technique holds broad potential for elucidating foundational dynamic biological processes.

The interaction between ultrafast, tightly focused lasers and materials has garnered significant interest owing to its distinctive properties. In this study, we present a versatile methodology for the fabrication of tunable plasmonic nanostructures by employing a disordered gold nanoisland-dielectric-metal configuration, achieved through femtosecond laser printing. By reshaping the gold nanoislands and reconfiguring them into nanograting-like structures, the orientation of these nanostructures is influenced by the polarization of the femtosecond laser light, leading to controllable plasmon resonance and polarization-sensitive color display. Furthermore, the system demonstrates a significant sensitivity to environmental humidity, as indicated by water adsorption, which leads to marked color changes. The hotspots generated through plasmonic coupling among disordered gold nanoislands significantly enhance polarization-multiplexed optical data storage, characterized by its high quality and low energy consumption. This experimental demonstration promotes the advancement of sophisticated optical devices for plasmonic color printing with tailored characteristics, thereby offering economical solutions for applications in optoelectronics and sensing.