Thirty-seven layer optical filter from polymerized solgel solutions

The feasibility of making multilayer optical filters using polymerized solgel solutions was demonstrated. Theoretical modeling was done to determine the expected optical response of multilayer coatings with various index profiles to select a coating design which was achievable using current technology and which would demonstrate the effectiveness of the method. The selected design consisted of a multilayer film whose index profile approximated a sine function, simulating the rugate concept for maximum reflection at 1.5 microm using a silicon substrate. Samples were prepared with 21, 29, and 37 layers. Agreement between the actual and the predicted optical performance of these films was good, showing that this method can be used to produce optical coatings having complicated index profiles.