The 2018 Nobel Prize in Physics was awarded for the invention of optical trapping and generation of ultrashort pulses, which revolutionized many areas of modern science and technology. However, physics of optical trapping under ultra-short pulsed excitation has not been explored much. The nonlinear nature of optical trapping force/potential under ultra-short pulsed excitation was theoretically investigated, however, without any direct experimental demonstration and development of any generalized theory independent of the particle size. In this work, we present a methodology to numerically estimate trapping force/potential including optical as well as thermal nonlinearity under ultra-short pulsed excitation and implement a variety of detection modalities to capture the particle's real-time trajectories. We show how highly asymmetric nonlinear axial potential, created by a femtosecond pulse-train, can be mapped from the dynamics of the trapped particle. Considering fine-tuning of trap-stiffness by changing nonlinearity, we envision far-reaching applications of using ultra-short pulsed excitation in laser trapping and manipulation.

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This paper combines interval type-2 fuzzy logic with adaptive control theory for the control of a three degree-of-freedom (DOF) helicopter. This strategy yields robustness to various kinds of uncertainties and guaranteed stability of the closed-loop control system. Thus, precise trajectory tracking is maintained under various operational conditions with the presence of various types of uncertainties. Unlike other controllers, the proposed controller approximates the helicopter’s inverse dynamic model and assumes no a priori knowledge of the helicopter’s dynamics or parameters. The proposed controller is applied to a 3-DOF helicopter model and compared against three other controllers, i.e., PID control, adaptive control, and adaptive sliding-mode control. Numerical results show its high performance and robustness under the presence of uncertainties. To better assess the performance of the control system, two quantitative tracking performance metrics are introduced, i.e., the integral of the tracking errors and the integral of the control signals. Comparative numerical results reveal the superiority of the proposed method by achieving the highest tracking accuracy with the lowest control effort.

Crucial to effective optical trapping is the ability to precisely control the nature of force/potential to be attractive or repulsive. The nature of particle being trapped is as important as...

Recent theoretical and experimental studies have shed light on how laser trapping dynamics under femtosecond pulsed excitation are fine-tuned by optical and thermal nonlinearities. Here, we present experimental results of trapping of single and multiple polystyrene beads (of 1 μm diameter). We show how integration and synchronization of bright-field video microscopy with confocal detection of backscatter provide both spatial and temporal resolution required to capture intricate details of nonlinear trapping dynamics. Such spatiotemporal detection is promising to have far-reaching applications in exploring controlled laser trapping and manipulations harnessed by optical and thermal nonlinearities.