在深海原位环境下精确捕获和收集单个目标微生物是当前深海微生物研究中的一大挑战。设计了一个应用在深海环境中的光镊捕获系统方案，系统包含光镊模块、微流控芯片、耐压外罩等部分，可实现原位捕获收集深海微生物。建立了位于南海北纬18°附近，1.5 km深处的海水折射率模型，预估了深海对光镊系统激光功率的损耗。使用T矩阵法计算对比了光镊在深海中和陆地上的纯水中对不同折射率和不同大小的球形微生物的捕获力。结果表明，相比于纯水中，光镊在1.5 km的深海中的最大轴向捕获力平均降低了25%，最大横向捕获力平均降低了20%。本研究可为未来基于光镊技术开发的深海微生物分选设备的下海实验提供参考。

为了实现粒子的非轴向旋转操控，对圆偏振涡旋光的光致旋转特性进行了研究。理论上，利用T矩阵理论，计算光场作用于微粒的光力和力矩，分析圆偏振涡旋光场中自旋角动量和轨道角动量的取向对非轴向旋转效应的影响。研究结果表明：当轨道角动量和自旋角动量的方向相同时，粒子除受轨道矩和轴向自旋矩作用外，还受一个可观的横向自旋矩作用，可以诱导粒子同时做轨道和非轴向自旋运动；当轨道角动量和自旋角动量方向相反，则粒子受到的横向自旋矩难以驱动其做非轴向自旋运动。实验上，利用全息光镊系统捕获微米尺度的粒子，观察到粒子做轨道运动时的非轴向自旋现象，对理论研究结果进行了初步验证。

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.

Mechanical forces play an important role in the behaviour of cells, from differentiation to migration and the development of diseases. Optical tweezers provide a quantitative tool to study these forces and must be combined with other tools, such as phase contrast and fluorescence microscopy. Detecting the retro-reflected trap beam is a convenient way to monitor the force applied by optical tweezers, while freeing top access to the sample. Accurate in situ calibration is required especially for single cells close to a surface where viscosity varies rapidly with height. Here, we take advantage of the well contrasted interference rings in the back focal plane of the objective to find the height of a trapped bead above a cover slip. We thus map the viscous drag dependence close to the surface and find agreement between four different measurement techniques for the trap stiffness down to 2 μm above the surface. Combining this detection scheme with phase contrast microscopy, we show that the phase ring in the back focal plane of the objective must be deported in a conjugate plane on the imaging path. This simplifies implementation of optical tweezers in combination with other techniques for biomechanical studies.

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.

悬浮光力传感技术利用真空环境的光阱实现对微纳尺度机械振子的悬浮和囚禁，将待测物理量转换为光悬浮机械振子运动参数的变化，理论上该振子与外部环境热噪声和振动完全隔绝，具有极高的测量分辨率潜力和易于小型化的独特优势。该技术在精密测量、微观热力学研究、暗物质观测、宏观量子态操控等领域具有广阔的应用前景。首先，阐述了悬浮光力系统中光力与光阱的基础概念和力学测量等基本理论；其次，介绍了其中初始起支、光力增强、位移测量、输出信号标定和等效反馈冷却等关键技术的研究进展，对比分析各子技术的特点，随后列举了悬浮光力传感技术在极弱力、加速度、微观质量、电学量、力矩等物理量测量中的典型应用；最后，总结了该技术的发展趋势，并提出相关建议。