Comprehensive modeling of beam propagation in multimode fiber and experimental validation

Optical fibers are used to perform highly accurate laser measurements in photolithography machines. External factors can affect the beam propagation in these fibers, so modifying the laser settings to accommodate the variations leads to higher yield on silicon wafers (semiconductors). This project predicts output field distribution, intensity and power loss from external effects as the light propagates through the fiber.

The team modeled the structure for simulation using MATLAB, which allows integration into the model the sponsor currently supports. The code is modular and derived from preexisting mathematical models. This allows for separate functions to simulate each of the effects independently. The team’s design for the experimental validation component of the project features a supercontinuum laser, and narrow band pass filters to test individual wavelengths. The laser is then coupled into an optical fiber with a bi-convex focusing lens where the fiber is exposed to bending, twisting and thermal effects. A Newport Si power detector records the power before and after coupling.