Single-beam trapping of micro-beads in polarized light: Numerical simulations A R Zakharian, P. Polynkin, M. Mansuripur, and J.V. Moloney College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 Abstract: Using numerical solutions of Maxwell's equations in conjunc- tion with the Lorentz law of force, we compute the electromagnetic force distribution in and around a dielectric micro-sphere trapped by a focused laser beam. Dependence of the optical trap's stiffness on the polarization state of the incident beam is analyzed for particles suspended in air or immersed in water, under conditions similar to those realized in practical optical tweezers. A comparison of the simulation results with available experimental data reveals the merit of one physical model relative to two competing models, the three models arise from different interpretations of the same physical picture O 2006 Optical Society of America OCIS codes: (2602110)Electromagnetic theory; (1407010)Optical trapping,(0004430)Nu- merical computation References and links L, M. Mansuripur, "Radiation Pressure and the linear momentum of the electromagnetic field, Opt. Express 12, 2064-2074(2005),http://www.opticsexpress.org/abstract.cfm?id=8301/adielectricwedge,"opt.Express13, 2. M. Mansuripur, A oney, "Radiation Pressure or 3. M. Mansuripur, "Radiation Pressure and the linear momentum of light in dispersive dielectric media, Opt Express13.2245-225002005),htp/w 4. M. Mansuripur, "Angular momentum of circu electric media, Opt. Express 13, 5315- 324(2005),http://www.opticsexpress.org/abstract.cfm?id=84895 5. S M. Barnett and R. Loudon. "On the electromagnetic force on a dielectric medium .submitted to J Phys. B At Mol. Phys. (January 2006) 6. A.R. Zakharian, M. Mansuripur and J.V. Moloney, "Radiation Pressure and the distribution of the electromagnetic force in dielectric media," Opt. Express 13, 2321-2336(2005), 7. R Gauthier, "Computation of the optical trapping force using an FDTD based technique, Opt. Express 13 J.App.Phys.91,5474-5488(2002) 9. A Rohrbach, "Stiffness of Optical Traps: Quantitative agreement between experiment and electromagnetic the Phys.Rev.Let.9%5,168102(2005) 10. W.H. Wright, G. Sonek, and M.w. Berns, "Radiation trapping forces on microspheres with optical tweezers Appl.Phys.Lett63,715-717(1993) I1. W.H. Wright, G.J. Sonek, and M.w. Berns, "Parametric study of the forces on microspheres held by optica Opt33,1735-1 12. A. Rohrbach and E. H. K. Stelzer, "Trapping forces, force constants, and potential depths for dielectric spheres rations,”Appl.Opt.41,2494-2507(2002) 13. D. Ganic, X Gan and M. Gu, "Exact radiation trapping force calculation based on vectorial diffraction theory Opt.Express12,2670-2675(2004),http://www.opticsexpress.org/abstract.cfm?id=80240 14. P.w. Barber and S.C. Hill, Light Scattering by Particles: Computational Methods(World Scientific Publishing o.1990) #67575-$15.00USD Received 15 February 2006, revised 7 April 2006, accepted 10 April (C)2006OSA 17 April 2006/Vol 14, No 8/OPTICS EXPRESSSingle-beam trapping of micro-beads in polarized light: Numerical simulations A.R. Zakharian, P. Polynkin, M. Mansuripur, and J.V. Moloney College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 armis@u.arizona.edu Abstract: Using numerical solutions of Maxwell’s equations in conjunc￾tion with the Lorentz law of force, we compute the electromagnetic force distribution in and around a dielectric micro-sphere trapped by a focused laser beam. Dependence of the optical trap’s stiffness on the polarization state of the incident beam is analyzed for particles suspended in air or immersed in water, under conditions similar to those realized in practical optical tweezers. A comparison of the simulation results with available experimental data reveals the merit of one physical model relative to two competing models; the three models arise from different interpretations of the same physical picture. © 2006 Optical Society of America OCIS codes: (260.2110) Electromagnetic theory; (140.7010) Optical trapping; (000.4430) Nu￾merical computation References and links 1. M. Mansuripur, “Radiation Pressure and the linear momentum of the electromagnetic field,” Opt. Express 12, 5375–5401 (2004), http://www.opticsexpress.org/abstract.cfm?id=81636. 2. M. Mansuripur, A.R. Zakharian and J.V. Moloney, “Radiation Pressure on a dielectric wedge,” Opt. Express 13, 2064–2074 (2005), http://www.opticsexpress.org/abstract.cfm?id=83011. 3. M. Mansuripur, “Radiation Pressure and the linear momentum of light in dispersive dielectric media,” Opt. Express 13, 2245–2250 (2005), http://www.opticsexpress.org/abstract.cfm?id=83032. 4. M. Mansuripur, “Angular momentum of circularly polarized light in dielectric media,” Opt. Express 13, 5315– 5324 (2005), http://www.opticsexpress.org/abstract.cfm?id=84895. 5. S. M. Barnett and R. Loudon, “On the electromagnetic force on a dielectric medium,” submitted to J. Phys. B: At. Mol. Phys. (January 2006). 6. A.R. Zakharian, M. Mansuripur and J.V. Moloney, “Radiation Pressure and the distribution of the electromagnetic force in dielectric media,” Opt. Express 13, 2321–2336 (2005), http://www.opticsexpress.org/abstract.cfm?id=83272. 7. R. Gauthier, “Computation of the optical trapping force using an FDTD based technique,” Opt. Express 13, 3707–3718 (2005), http://www.opticsexpress.org/abstract.cfm?id=83817. 8. A. Rohrbach and E.H.K. Stelzer, “Three-dimensional position detection of optically trapped dielectric particles,” J. Appl. Phys. 91, 5474–5488 (2002). 9. A. Rohrbach, “Stiffness of Optical Traps: Quantitative agreement between experiment and electromagnetic the￾ory,” Phys. Rev. Lett. 95, 168102 (2005). 10. W.H. Wright, G.J. Sonek, and M.W. Berns, “Radiation trapping forces on microspheres with optical tweezers,” Appl. Phys. Lett. 63, 715–717 (1993). 11. W.H. Wright, G.J. Sonek, and M.W. Berns, “Parametric study of the forces on microspheres held by optical tweezers,” Appl. Opt. 33, 1735–1748 (1994). 12. A. Rohrbach and E. H. K. Stelzer, “Trapping forces, force constants, and potential depths for dielectric spheres in the presence of spherical aberrations,” Appl. Opt. 41, 2494–2507 (2002). 13. D. Ganic, X. Gan and M. Gu, “Exact radiation trapping force calculation based on vectorial diffraction theory,” Opt. Express 12, 2670–2675 (2004), http://www.opticsexpress.org/abstract.cfm?id=80240. 14. P.W. Barber and S.C. Hill, Light Scattering by Particles: Computational Methods (World Scientific Publishing Co. 1990). #67575 - $15.00 USD Received 15 February 2006; revised 7 April 2006; accepted 10 April 2006 (C) 2006 OSA 17 April 2006 / Vol. 14, No. 8 / OPTICS EXPRESS 3660