Optical interference coating design challenge 2025: a design for production and an immersed, three-line, polarizing notch filter [Invited]

From the very first Optical Interference Coating (OIC) Topical Meeting, to our knowledge, there have been two types of design challenges that were very different from one another. For OIC 2025 there was a common theme, where each challenge required the designer to fabricate their designs using a virtual monitoring system and compare the results to the theoretical design. The design problems for OIC 2025 were a design for production and an immersed, three-line, polarizing notch filter.