Experimental study of radiation force on microspheres due to a single beam optical trap

• Main Authors: Banzon, D., Camelo, J., Pobre, Romeric F., Baclig, A., Buenaobra, B., Blanca, C., Saloma, C.
• Format: text
• Published: Animo Repository 2005
• Subjects: Microspheres; Piezoelectricity; Physical Sciences and Mathematics; Physics
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/12379
• Institution: De La Salle University

Experimental study of radiation force on microspheres (e.g. polystyrene, fused silica, quartz crystals) was done using a single beam 1064 nm Nd: YAG diode-pumped solid state (dpss) laser. Other experimental parameter (e.g. back focal power, numerical aperture, and diameter size of the microsphere) were also included in the experimentation process. Near the beam focus, optical trapping force behaves linearly with microsphere displacement where trapping stiffness is the constant of proportionality. Optical trapping stiffness was determined using the drag force method which was determined from the kinematic variables of the trapped microspheres. This computation was realized when trapped particles are subjected to external oscillations driven by a piezoelectric transducer attached to a glass slide. Detection and measurement of these kinematic variables were taken from the CCD imaging system of IMAQ-National Instruments. Through MATLAB's image processing program, position, velocity, and acceleration of the microspheres were calculated. Results show that all four experimental parameters had a direct effect on the trapping stiffness of the single beam optical trap. Optimum optical trap is achieved when quartz crystal microsphere was chosen among other nonlinear microsphere with experimental parameters: N.Α. = 0.5, refractive index of 1.458, back focal power of 16 mW and diameter size of 10um.