Figure 2: Physical performance of the photo-stimulation system.

(a) The inverse dependence of the stimulation spot diameter on the beam diameter at the objective back aperture. Red and blue points represent measured spot sizes obtained with X4 and X10 objective lenses, respectively. Solid lines indicate an inverse relation fit. (b) A 3D visualization of the stimulation volumes accessible by the binary-phase holographic system with a X10 objective, for diffraction efficiencies greater than 15% (blue), 20% (green) and 30% (red). (c) The spatially varying diffraction efficiency due to the rectangular SLM pixel shape causes spot intensity to decrease with increasing lateral displacement (green points, left plot), which coincides with theoretical prediction of a sinc-shaped envelope (solid line). Compensation of this effect is achieved by inversely weighing each spot during hologram calculation, resulting in improved uniformity (green points, right plot) close to a constant value (solid line).