Laguerre-Gaussian beams

Figure 7 Spatial dependence of optical force on an absorbing particle The radial and axial variation of the optical force is shown for both a TEMoo Gaussian beam and an LG03 Laguerre-Gaussian beam. Both beams have the same power (1 mW), spot size (2 urn) and wavenumber (free space wavelength 632.8 nm). The particle has a circular cross-section of radius 1 pm. Due to the cylindrical symmetry, there is no azimuthal variation of the force. The beam is propagating in the +z direction, with the beam waist at z = 0.

Spectral representations of the fields (plane, cylindrical, spherical wave expansions Hermite-Gaussian and Laguerre-Gaussian beams prolate spheroidal harmonics)... 

Liu, C., and Kim, D. Y. 2007. Differential imaging in coherent anti-Stokes Raman scattering microscopy with Laguerre-Gaussian excitation beams. Opt. Express 15 10123-34. 

The theory will be developed in terms of the two most common types of beams used for trapping particles, namely TEMoo Gaussian beams (denoted (G)) and Laguerre-Gaussian doughnut beams (denoted (LG)) described by a radial mode index p and an azimuthal mode index 1. 

Fig. 6.2 Illustration of dipole traps with red and blue detuning. In the first case, a simple Gaussian laser beam is assumed. In the second case, a Laguerre-Gaussian LGoi doughnut mode is chosen that provides the same potential depth and the same curvature in the trap center (note that the latter case requires e times more laser power or a smaller detuning). (Reprinted from Grimm et al. 2000 with courtesy and permission of Academic Press.)...

In this paper we review the work performed on absorbing particles. Both Gaussian and Laguerre-Gauss modes are used. We outline a model for the trapping of absorbing particles for these beam types based on the effects of transfer of momentum from the beam to the particle. We also consider in some detail the heating effects. 

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