Narrow Results

Mitochondria play a crucial role in the physiological functions and energy metabolism of neurons, which can help in the understanding of complex biochemical reactions associated with various neurodegenerative diseases. Neurons, being highly differentiated terminal cells, require a greater number of mitochondria than ordinary cells to generate significant amounts of ATP, which is necessary for the growth of differentiated neuronal structures like axons and dendrites and the transmission of electrical signals along neuronal axons. Advancements in imaging technology, electrophysiology, and fluorescence targeting labeling have facilitated the study of mitochondrial movements in neurons and axons. However, disordered mitochondrial movements can hinder their analysis and characterization. Thus, it becomes necessary to artificially control their transport. Here, we demonstrate the utilization of scanning optical tweezers (SOTs) on the stable trapping and precise transport of soma or axon of neurons and enable. The presented method provides an optical approach to the control of mitochondria or other organelles in complex and variable biological environment.

We review recent works on optomechanics of optically trapped microspheres and nanoparticles in vacuum, which provide an ideal system for studying macroscopic quantum mechanics and ultrasensitive force detection. An optically trapped particle in vacuum has an ultrahigh mechanical quality factor as it is well-isolated from the thermal environment. Its oscillation frequency can be tuned in real time by changing the power of the trapping laser. Furthermore, an optically trapped particle in vacuum may rotate freely, a unique property that does not exist in clamped mechanical oscillators. In this review, we will introduce the current status of optical trapping of dielectric particles in air and vacuum, Brownian motion of an optically trapped particle at room temperature, Feedback cooling and cavity cooling of the Brownian motion. We will also discuss about using optically trapped dielectric particles for studying macroscopic quantum mechanics and ultrasensitive force detection. Applications range from creating macroscopic Schrödinger's cat state, testing objective collapse models of quantum wavefunctions, measuring Casimir force, searching short-range non-Newtonian gravity, to detect gravitational waves.

When femtosecond laser pulses pass through a trapped polystyrene bead, water breakdown is induced even though the energy of laser pulse is much lower compared to the threshold value of breakdown when the femtosecond laser directly irradiates in water. This mechanism is assigned to the secondary convergence of the laser by the trapped bead.

The rates of activated processes, such as escape from a metastable state and nucleation, are exponentially sensitive to an externally applied field. We describe how this applies to modulation by high-frequency fields and illustrate it with experimental observations. The results may lead to selective control of diffusion in periodic potentials, novel control mechanisms for crystal growth, and new separation techniques.

An important challenge in the field of materials design and synthesis is to deliberately design mesoscopic objects starting from well-defined precursors and inducing directed movements in them to emulate biological processes. Recently, mesoscopic metal-oxide-based soft oxometalates (SOMs) have been synthesized from well-defined molecular precursors transcending the regime of translational periodicity. Here, we show that it is actually possible to controllably move such an asymmetric SOM, with the shape of a "peapod" along complex paths using tailor-made sophisticated optical potentials created by spin–orbit interaction of light due to a tightly focused linearly polarized Gaussian beam propagating through a stratified medium in an optical trap. We demonstrate motion of individual trapped SOMs along circular paths of more than 15 μm in a perfectly controlled manner by simply varying the input polarization of the trapping laser. Such controlled motion can have a wide range of applications starting from catalysis to the construction of dynamic mesoscopic architectures.

The rates of activated processes, such as escape from a metastable state and nucleation, are exponentially sensitive to an externally applied field. We describe how this applies to modulation by high-frequency fields and illustrate it with experimental observations. The results may lead to selective control of diffusion in periodic potentials, novel control mechanisms for crystal growth, and new separation techniques.