Illumination tilted beam

Tilt the white light swing arm back and focus the laser beam in the back focal plane of the objective by moving the fiber optic mount holder in the TIR-FM illumination port. When focused, the excitation light exits the lens as a column of light and will project as a tight spot on the ceiling Notes 9-11). 

Fig. 20-2 (a) Coordinates for describing the fields of the beam incident on the endface and (b) the fraction of total power of a Gaussian beam entering the modes of an infinite parabolic-profile fiber as a function of the tilt angle 0.. The orientation of the Gaussian beam is shown for (c) on-axis, (d) tilted and (e) offset illumination. 

Fig. 20-4 (a) The fraction of total power in a uniform beam that excites modes of a step-profile fiber as a function of the tilt angle 0j, where P includes all modes with the same values of U in Fig. 14-4, and bm is the total excited power [2]. (b) Variation of the excitation efficiency with the fiber parameter for on-axis illumination, where solid curves denote the exact solution of Eq. (20-27c) and the dashed curve is the Gaussian approximation of Eq. (20-28a). (d) The corresponding curves for the fundamental mode for various ratios of beam to core radii calculated from Eqs. (20-27c) and (20-28b). (c) Plots of Pq/Pi for the fundamental mode and different ratios of beam to core radii. 

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