Depth-Dependent Optical Stiffness Toward Water-Air Interface

Abstract

This research attempted to quantify the optical stiffness of trapped polystyrene bead toward water-air interface. The optical tweezers with 975 nm wavelength was used to optically trap a single 3 micron diameter of bead in a water-contained cell with air exposed top water surface. The optical stiffness was justified on effective radius (r*) of the bead lateral spatial distribution. The scattered light signals due to the trapped bead at different laser focus height from the bottom glass-water interface (less than 20 µm) and laser trapping powers (1.7 mW to 7.5 mW) were analyzed to investigate the r* profile. It was found that within our experimental condition, r* was independent of focus height at fixed power and exponentially decay with respect to laser power at fixed focus height.

The trapping of a single 4-cyano-4-pentylbiphenyl (5CB) microdroplet in water using optical tweezers

“…was increased with the increasing used. This is due to the strong gradient force of high optical power density [4].…”

Optical Manipulation of a Liquid Crystal (LC) Microdroplet by Optical Force

“…[4,5] Optical trapping is a non-contact manipulation technique of micron and nanometer-sized particles using a highly focused laser beam. [6][7][8][9][10][11][12] The focused laser beam creates a region of narrow optical potential that attracts and confines particles. Figure 1 illustrates the optical trapping mechanism of LC (5CB) microdroplets using a focused laser.…”