Due to the promising applications of femtosecond laser filamentation in remote sensing, great demands exist for diagnosing the spatiotemporal dynamics of

Due to the promising applications of femtosecond laser filamentation in remote sensing, great demands exist for diagnosing the spatiotemporal dynamics of filamentation. However, until now, the rapid and accurate diagnosis of a femtosecond laser filament remains a severe challenge. Here, a novel filament diagnosing method is proposed, which can measure the longitudinal spatial distribution of the filament by a single laser shot-induced acoustic pulse. The dependences of the point-like plasma acoustic emission on the detection distance and angle are obtained experimentally. The results indicate that the temporal profile of the acoustic wave is independent of the detection distance and detection angle. Using the measured relation among the acoustic emission and the detection distance and angle, a single measurement of the acoustic emission generated by a single laser pulse can diagnose the spatial distribution of the laser filament through the Wiener filter deconvolution (WFD) algorithm. The results obtained by this method are in good agreement with those of traditional point-by-point acoustic diagnosis methods. These findings provide a new solution and idea for the rapid diagnosis of filament, thereby laying a firm foundation for femtosecond laser filament-based promising applications.show less

Structurally anisotropic materials are ubiquitous in several application fields, yet their accurate optical characterization remains challenging due to th

Structurally anisotropic materials are ubiquitous in several application fields, yet their accurate optical characterization remains challenging due to the lack of general models linking their scattering coefficients to the macroscopic transport observables and the need to combine multiple measurements to retrieve their direction-dependent values. Here, we present an improved method for the experimental determination of light-transport tensor coefficients from the diffusive rates measured along all three directions, based on transient transmittance measurements and a generalized Monte Carlo model. We apply our method to the characterization of light-transport properties in two common anisotropic materials—polytetrafluoroethylene tape and paper—highlighting the magnitude of systematic deviations that are typically incurred when neglecting anisotropy.show less

Quantitative phase imaging (QPI) is a label-free technique that provides optical path length information for transparent specimens, finding utility in bio

Quantitative phase imaging (QPI) is a label-free technique that provides optical path length information for transparent specimens, finding utility in biology, materials science, and engineering. Here, we present QPI of a three-dimensional (3D) stack of phase-only objects using a wavelength-multiplexed diffractive optical processor. Utilizing multiple spatially engineered diffractive layers trained through deep learning, this diffractive processor can transform the phase distributions of multiple two-dimensional objects at various axial positions into intensity patterns, each encoded at a unique wavelength channel. These wavelength-multiplexed patterns are projected onto a single field of view at the output plane of the diffractive processor, enabling the capture of quantitative phase distributions of input objects located at different axial planes using an intensity-only image sensor. Based on numerical simulations, we show that our diffractive processor could simultaneously achieve all-optical QPI across several distinct axial planes at the input by scanning the illumination wavelength. A proof-of-concept experiment with a 3D-fabricated diffractive processor further validates our approach, showcasing successful imaging of two distinct phase objects at different axial positions by scanning the illumination wavelength in the terahertz spectrum. Diffractive network-based multiplane QPI designs can open up new avenues for compact on-chip phase imaging and sensing devices.show less

Surface plasmons have been given high expectations in terahertz (THz) on-chip photonics with highly bound integrated transmission and on-chip wavefront en

Surface plasmons have been given high expectations in terahertz (THz) on-chip photonics with highly bound integrated transmission and on-chip wavefront engineering. However, most surface plasmonic coupling strategies with tailorable polarization-dependent features are challenged in broadband propagation and dynamic manipulation. In this work, a liquid crystal (LC)-integrated surface plasmonic metadevice based on arc-arrayed pair-slit resonators (APSRs) is demonstrated. The mirror-symmetry structures of this metadevice achieve the spin-selective unidirectional achromatic focusing, of which the broadband characteristic is supported by containing multiple APSRs with slits of different sizes corresponding to different excitation frequencies. Moreover, arc radii are precisely designed to meet the phase matching condition of constructive interference, so that the operating frequency of this on-chip metadevice is broadened to 0.33–0.60 THz. Furthermore, the LC integration provides the active energy distribution between the left and right focal spots, and the actual modulation depth reaches up to 73%. These THz active, wideband, on-chip manipulation mechanisms and their devices are of great significance for THz-integrated photonic communication, information processing, and highly sensitive sensing.show less