Multimode Laser Beam Profile

Modifying beam profiles with multimode fibers by increasing the launch angle of a gaussian beam into a multimode fiber the output beam profile can be modified.

Multimode laser beam profile.

The maximum beam spot size is 3 4 mm at z 0 and at 50 cm away from the laser it becomes 5 8 mm. Here we investigated the effect of changing the input angle of a focused laser beam into a multimode fiber patch cable. As the input angle was increased the proportion of meridional rays to skew rays increased first forming a top hat and then a donut beam profile. A comparison of gaussian and multimode beams with equal energy was carried out in order to estimate influence of beam profile only.

Intensity profile of a multimode beam which has about the maximum possible m 2 value for efficient launching into the fiber. Initial profile input angle 0. Single mode lasing gaussian beam results in better reproducibility of analytical signals compared to multimode lasing while laser energy reproducibility was the same for both cases. The figure below shows the intensity profile of a monochromatic beam from a numerical simulation where the power is well spread over all guided modes.

B 3d beam intensity profiles of the multimode dpss laser at the constructed far field using a converging lens.