Laser manipulation of a smectic liquid-crystal droplet

The laser trapping of a smectic-A liquid-crystal micro-droplet was spatially traced during its transient into the trapped position. The lateral and angular orientation of the droplet were determined and followed in time during the axial descent of the micro-droplet into the stationary trapped position using the analysis of polarization changes of the light passed through the droplet with temporal resolution of a video refresh rate of 30 ms. The spatial resolution of 0.1-1 microm has been achieved for typical laser trapping powers of 2-600 mW. The axial profile of a laser trapping force (an ellipticity of the focal spot) has been determined. The laser trapping mechanism of smectic micro-droplets is discussed in terms of minimization of a light-droplet interaction.