Has anyone ever damaged their expensive TIRF objectives by focusing on the back focal plane (BFP) with too much power? I couldn’t get an answer from Nikoin about damage threshold (DT) at the BFP (I imagine the DT will depend on where the BFP happens to lie - near a coated surface/cement/or deep in a lens), they only mentioned that they did not observe issues with collimated beams filling the back aperture at 150mW (so it’s possible to work out a lower limit). The objective in question is HP Apo TIRF 100x/1.49NA (MRD01993). A senior academic was telling me horror stories about people burning spots in their precious TIRF objectives.
Do not know the answer. But have burned a lot of holes in things with lasers by accident over the years. Also a lot of frustrating conversations regarding damage thresholds with various vendors (one not too long ago with a linearly variable filter vendor regarding specific parameters related to its use with a supercontinuum laser). Often they do have data but not for the particular wavelength or parameters of your intended use case.
You might ask:
If someone damaged such an objective he may have repaired it. He has provided me with a lot information about the lenses which I didn’t know (particularly about the soft coatings on the internal surfaces of some lens elements within particular objectives). He may even have damaged individual lens elements left from a previous repair if you want to experiment without damaging a good lens.