Cell identification and sorting have been hot topics recently. However, most conventional approaches can only predict the category of a single target, and lack the ability to perform multitarget tasks to provide coordinate information of the targets. This limits the development of high-throughput cell screening technologies. Fortunately, artificial intelligence (AI) systems based on deep-learning algorithms provide the possibility to extract hidden features of cells from original image information. Here, we demonstrate an AI-assisted multitarget processing system for cell identification and sorting. With this system, each target cell can be swiftly and accurately identified in a mixture by extracting cell morphological features, whereafter accurate cell sorting is achieved through noninvasive manipulation by optical tweezers. The AI-assisted model shows promise in guiding the precise manipulation and intelligent detection of high-flux cells, thereby realizing semi-automatic cell research.

Owing to their unique optical properties and new degrees of freedom, orbital angular momentum (OAM) beams have been applied in various fields. Detection of the topological charges (TCs) of OAM beams is the key step for their applications. However, on-chip sorting of OAM beams with large TCs still remains a challenge. In this paper, Bloch surface wave (BSW) structures with five semi-ring shaped nanoslits are modeled. A spatial separation of 135 nm on the chip is obtained between two neighboring OAM states. OAM beams with TCs up to 35 can be successfully sorted by the BSW structures, which is much larger than that using metallic structures (only seven). BSW structures exhibit better OAM sorting performances than metallic structures. We systematically show how the lower attenuation of BSW structures leads to far superior separation ability compared to surface plasmons propagating on metallic structures. In addition, sorting of two OAM beams with different TCs simultaneously can be achieved in this way. Our results reveal that BSW structures should be an excellent solution for OAM sorting with large TCs, which is beneficial for applications in integrated on-chip devices and optical communications.

Nonlinear responses of nanoparticles induce enlightening phenomena in optical tweezers. With the gradual increase in optical intensity, effects from saturable absorption (SA) and reverse SA (RSA) arise in sequence and thereby modulate the nonlinear properties of materials. In current nonlinear optical traps, however, the underlying physical mechanism is mainly confined within the SA regime because threshold values required to excite the RSA regime are extremely high. Herein, we demonstrate, both in theory and experiment, nonlinear optical tweezing within the RSA regime, proving that a fascinating composite trapping state is achievable at ultrahigh intensities through an optical force reversal induced through nonlinear absorption. Integrated results help in perfecting the nonlinear optical trapping system, thereby providing beneficial guidance for wider applications of nonlinear optics.

On-chip manipulation of the spatiotemporal characteristics of optical signals is important in the transmission and processing of information. However, the simultaneous modulation of on-chip optical pulses, both spatially at the nano-scale and temporally over ultra-fast intervals, is challenging. Here, we propose a spatiotemporal Fourier transform method for on-chip control of the propagation of femtosecond optical pulses and verify this method employing surface plasmon polariton (SPP) pulses on metal surface. An analytical model is built for the method and proved by numerical simulations. By varying space- and frequency-dependent parameters, we demonstrate that the traditional SPP focal spot may be bent into a ring shape, and that the direction of propagation of a curved SPP-Airy beam may be reversed at certain moments to create an S-shaped path. Compared with conventional spatial modulation of SPPs, this method offers potentially a variety of extraordinary effects in SPP modulation especially associated with the temporal domain, thereby providing a new platform for on-chip spatiotemporal manipulation of optical pulses with applications including ultrafast on-chip photonic information processing, ultrafast pulse/beam shaping, and optical computing.On-chip manipulation of the spatiotemporal characteristics of optical signals is important in the transmission and processing of information. However, the simultaneous modulation of on-chip optical pulses, both spatially at the nano-scale and temporally over ultra-fast intervals, is challenging. Here, we propose a spatiotemporal Fourier transform method for on-chip control of the propagation of femtosecond optical pulses and verify this method employing surface plasmon polariton (SPP) pulses on metal surface. An analytical model is built for the method and proved by numerical simulations. By varying space- and frequency-dependent parameters, we demonstrate that the traditional SPP focal spot may be bent into a ring shape, and that the direction of propagation of a curved SPP-Airy beam may be reversed at certain moments to create an S-shaped path. Compared with conventional spatial modulation of SPPs, this method offers potentially a variety of extraordinary effects in SPP modulation especially associated with the temporal domain, thereby providing a new platform for on-chip spatiotemporal manipulation of optical pulses with applications including ultrafast on-chip photonic information processing, ultrafast pulse/beam shaping, and optical computing.

Imaging ultrafast processes in femtosecond (fs) laser–material interactions such as fs laser ablation is very important to understand the physical mechanisms involved. To achieve this goal with high resolutions in both spatial and temporal domains, a combination of optical pump–probe microscopy and structured illumination microscopy can be a promising approach, but suffers from the multiple-frame method with a phase shift that is inapplicable to irreversible ultrafast processes such as ablation. Here, we propose and build a wide-field single-probe structured light microscopy (SPSLM) to image the ultrafast three-dimensional topography evolution induced by fs lasers, where only a single imaging frame with a single structured probe pulse is required for topography reconstruction, benefiting from Fourier transform profilometry. The second harmonic of the fs laser is used as the structured probe light to improve spatial lateral resolution into the subwavelength region of ∼478nm, and the spatial axial and temporal resolutions are estimated to be ∼22nm and ∼256fs, respectively. With SPSLM, we successfully image the ultrafast topography evolution of a silicon wafer surface impacted by single and multiple fs pulses. The variable formation and evolution of the laser induced periodic surface structures during an ultrashort time are visualized and analyzed. We believe that SPSLM will be a significant approach for revealing and understanding various ultrafast dynamics, especially in fs laser ablation and material science.

The optical vortex beam has widely been studied and used because of its unique orbital angular momentum (OAM). To generate and control OAM in compact and integrated systems, many metallic metasurface devices have been proposed, however, most of them suffer from the low efficiency. Here, we propose and experimentally verify a high-efficiency monolayer metallic metasurface composed of semicircular nano-grooves distributed with detour phase. The metasurface can generate single or an array of OAM with spin-sensitive modulation and achieve the maximum efficiency of 60.2% in theory and 30.44% in experiment. This work has great potential in compact OAM detection and communication systems.

Optical surface waves have widely been used in optical tweezers systems for trapping particles sized from the nano- to microscale, with specific importance and needs in applications of super-resolved detection and imaging if a single particle can be trapped and manipulated accurately. However, it is difficult to achieve such trapping with high precision in conventional optical surface-wave tweezers. Here, we propose and experimentally demonstrate a new method to accurately trap and dynamically manipulate a single particle or a desired number of particles in holographic optical surface-wave tweezers. By tailoring the optical potential wells formed by surface waves, we achieved trapping of the targeted single particle while pushing away all surrounding particles and further dynamically controlling the particle by a holographic tweezers beam. We also prove that different particle samples, including gold particles and biological cells, can be applied in our system. This method can be used for different-type optical surface-wave tweezers, with significant potential applications in single-particle spectroscopy, particle sorting, nano-assembly, and others.

The cylindrical vector beam (CVB) has been extensively studied in recent years, but detection of CVBs with on-chip photonic devices is a challenge. Here, we propose and theoretically study a chiral plasmonic lens structure for CVB detection. The structure illuminated by a CVB can generate single plasmonic focus, whose focal position depends on the incident angle and the polarization order of CVB. Thus, the incident CVB can be detected according to the focal position and incident angle and with a coupling waveguide to avoid the imaging of the whole plasmonic field. It shows great potential in applications including CVB-multiplexing integrated communication systems.

作为捕获与操纵微观粒子的重要手段,光镊技术因其具有非接触和高精度操控等优势在物理、化学和生物医学等领域得到了广泛的研究及应用。飞秒激光超高的峰值功率能够有效激发被捕获物体的非线性光学响应,同时超短的脉冲输出可以在光与物质相互作用的过程中产生更小的热效应,从而在光学微操控中展现出特有的优势。本文综述了飞秒激光光镊的研究进展,详细讨论了其中涉及的非线性效应和应用,并对其发展前景进行了展望。

Tip-enhanced Raman scattering (TERS) spectroscopy is a nondestructive and label-free molecular detection approach that provides high sensitivity and nanoscale spatial resolution. Therefore, it has been used in a wide array of applications. We demonstrate a gap-plasmon hybridization facilitated by a bottom-illuminated TERS configuration. The gap-plasmon hybridization effect is first performed with the finite-difference time-domain method to optimize the parameters, and experiments are then conducted to calibrate the performance. The results demonstrate an enhancement factor of 1157 and a spatial resolution of 13.5 nm. The proposed configuration shows great potential in related surface imaging applications in various fields of research.