Multimode Laser Beam Profile

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.

Multimode laser beam profile.

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. 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. Focusing the light normal to the fiber face produced a near gaussian output beam profile figure 1 and increasing the angle resulted in top hat figure 2 and donut shaped figure 3 beam profiles. Multimode fibers are used for the transport of light from a laser source to the place where it is needed particularly when the light source has a poor beam quality and or the high optical power requires a large area of the fiber core.

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. 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. For example light from stationary high power lasers of various types can be sent to material processing stations for cutting or welding where e g. Here we investigated the effect of changing the input angle of a focused laser beam into a multimode fiber patch cable.

Intensity profile of a multimode beam which has about the maximum possible m 2 value for efficient launching into the fiber.