Radiation force of coherent and partially coherent flat-topped beams on a Rayleigh particle

Abstract

Propagations of coherent and partially coherent flat-topped beams through a focusing optical system are formulated. The radiation force on a Rayleigh dielectric sphere induced by focused coherent and partially coherent flat-topped beams is investigated theoretically. It is found that we can increase the transverse trapping range at the planes near the focal plane by increasing the flatness (i.e., beam order) of the flat-topped beam, and increase the transverse and longitudinal trapping ranges at the focal plane by decreasing the initial coherence of the flat-topped beam. Moreover the trapping stiffness of flat-topped beam becomes lower as the beam order increases or the initial coherence decreases. The trapping stability is also analyzed.

Towards spatio-temporal control in optical trapping

“…This can be understood from equation (1), where the ▽E 2 is zero and hence there is no gradient force available to drag the beads for getting trapped. This is also in accordance with the theoretical prediction [6]. We trapped 1 μm particle using both the CW and mode-locked laser and found that the escape velocity of the particle is more in case of pulsed laser optical trap compared to the CW one at the same power level (Figure 3), which essentially shows that the force acting on the 1 μm particle is higher in the pulsed laser situation, as the force acting on the trapped particle is given by: (5) Where r is the radius of the particle, η being the dynamic viscosity of water and v is the escape velocity.…”

Conical refraction: fundamentals and applications

“…Flat-top beams are useful in a wide variety of laser applications where one needs a uniform intensity over a fixed area, such as in optical processing [101,117], laser-driven acceleration of particles [118,119], optical trapping [120] or gravitational-waves detectors [121]. Nevertheless, the generation of flat-top beams is a non trivial task and usually diffractive optical elements are required, which suffers from several drawbacks such as losses due to inefficient mode projection or diffraction, their extreme precise control or their limited spectral range [101].…”

Optical forces on small particles from partially coherent light

“…In this context some studies concerning momentum conservation laws have been established both for deterministic [4][5][6][7] and partially coherent wavefields [8,9]. However, in spite of the vaste research on coherence of light (even in the context of inverse problems [10][11][12][13]) and on optical trapping, no study on optical forces from fluctuating partially coherent fields has been developed yet, to our knowledge; apart from a couple of works [14,15] on Rayleigh particles in some particular focusing configurations.…”