Trapping and precisely manipulating micron and sub-micron scale objects without interfering with a physical attachment is an interesting technical challenge. In many scientific areas such as chemistry, physics and biology, using radiation forces obtained by tightly focusing laser beams has become a useful tool for trapping and manipulating micrometer-sized particles. There are unique design requirements for an optical levitation trap setup. Especially regarding stability, loading of targets under vacuum and trapping of transparent or reflective targets, a computational tool requirement to help inform further development and experimental considerations motivate the work we present here. In this numerical study, the radial and axial forces on a micron-sized spherical particle in an optical levitation trap are calculated with the ray-optics approach. This force field is generated due to the momentum change in the photon-stream path of tightly focused incident laser beam. Under the exposure of this force, particle departs towards the centre of the Gaussian beam. Once it reaches the center of the beam, the transverse force diminishes and only the longitudinal force in the direction of the Gaussian beam remains. Utilizing the calculated force field, we simulated the optical trapping dynamics of a transparent spherical particle with continuous-wave 〖TEM〗_00 Gaussian beam in Matlab.
Anahtar Kelimeler: Optical Trapping, Gaussian Beam, Micron-sized Particle
|
